@article{ollis_2020, title={Kinetic analysis of liquid phase photocatalysis and photolysis: A frequent disguise!}, volume={340}, ISSN={["1873-4308"]}, DOI={10.1016/j.cattod.2018.11.011}, abstractNote={Studies of phenol photocatalyzed oxidation and of organic dye photolyzed or photocatalyzed destruction which explored variable initial concentrations, Co, often assumed pseudo first order behavior, and fitted data to a semilog plot of concentration, C(t) vs time, and found that the apparent first order rate constant decreases with increasing Co. We show from multiple literature examples that this behavior often disguises a true zero order initial rate of reaction. We recommend a re-analysis of existing literature reporting first order rate constants which vary with initial reactant concentration, Co.}, journal={CATALYSIS TODAY}, author={Ollis, David}, year={2020}, month={Jan}, pages={7–11} }
 @article{ollis_2019, title={Kinetics of photocatalytic, self-cleaning surfaces: A decision tree approach for determination of reaction order}, volume={242}, ISSN={["1873-3883"]}, DOI={10.1016/j.apcatb.2018.08.079}, abstractNote={Self-cleaning photocatalytic surfaces have several decades of application, yet satisfactory rate equations for analyzing the kinetics of reactions on such solid surfaces are lacking, due in large part to the many configurations of the catalyst and the deposited contaminants. We analyze the existing literature and show that nearly all studies can be described by application of the power law for rate of reaction: Rate = kcat [C] n where n = apparent reaction order, and kcat is a fundamental constant of the catalytic material. The value of reaction order, n, we show requires answers to the following six questions. In each case, the observed apparent kinetic order depends upon interplay among the distributions of photocatalyst, reactant, and irradiance. 1. Is the photocatalyst porous or non-porous? Example: Stearic acid on/within non-porous/porous photocatalyst layer. 2. Is the photocatalytically active layer optically thin or thick? Example: Dye conversion in TiO2 layers vs. 10% TiO2/SiO2? 3. Is the probe reactant deposit a submonolayer or multilayer? Examples: Dye sub/multilayers with TiO2 4. Is probe reactant light absorption negligible or important? Example: Stearic acid vs. soot 5. Is the probe reactant present as a continuous film or as a distribution of discrete islands? Example: Long chain carboxylic acids on TiO2 6. If distributed, what is breadth of distribution? Example: Stearic acid on TiO2 For contaminant removal we demonstrate apparent reaction orders of 0, ½, 1, and 2! Simple analysis is used to explain this diversity of apparent reaction orders. We use the six questions posed to construct a decision tree for determination of the apparent reaction order, n, as a function of responses to the six questions.}, journal={APPLIED CATALYSIS B-ENVIRONMENTAL}, author={Ollis, David}, year={2019}, month={Mar}, pages={431–440} }
 @article{ollis_2018, title={Connecting contact angle evolution to photocatalytic kinetics of self cleaning surfaces}, volume={310}, ISSN={["1873-4308"]}, DOI={10.1016/j.cattod.2017.09.051}, abstractNote={We demonstrate that the Cassie-Baxter model of contact angle for a composite surface consisting of “bare” and “covered” components (typically adventitious or purposeful carbonaceous deposits) can be used for quantitative determination of the kinetics of “self-cleaning” photocatalyst surfaces. In particular, literature data is analyzed to demonstrate examples of zero and first order reaction, as well as quantitative determination of rate constant values for two key processes: the initial activation of new photocatalysts, and the removal of purposeful fatty acid deposits such as that required in the ISO standard 27448: 2009 for activity determination of photocatalytic self-cleaning surfaces.}, journal={CATALYSIS TODAY}, author={Ollis, David}, year={2018}, month={Jul}, pages={49–58} }
 @article{ollis_2018, title={Kinetics of Photocatalyzed Reactions: Five Lessons Learned}, volume={6}, ISSN={["2296-2646"]}, DOI={10.3389/fchem.2018.00378}, abstractNote={Elucidation of kinetics of photocatalyzed chemical mechanisms occurring at interfaces (gas-solid, liquid-solid) has been challenging. We summarize here five lessons learned over five decades. 1. An assumed reaction network leads to a single kinetic model, but a common model, the Langmuir–Hinshelwood rate equation, r = kcat K C/ [1 +KC], arises from multiple mechanisms, hence models alone do not reveal unique mechanisms. 2. The Langmuir–Hinshelwood model parameter kcat represents the slow step at a catalyst surface, and in thermal catalysis, depends upon the reactant structure. However, early photocatalysis work with light chlorinated hydrocarbons in aqueous solutions showed a single kcat value, independent of reactant structure. 3. The dependence of the Langmuir-Hinshelwood parameters, kcat and K, upon intensity indicates that a pseudo-steady state approach is more fundamental than the presumed equilibrated adsorption of the LH model. 4. Dyes and phenols are commonly studied, and claimed as first order reactions, despite often exhibiting rate constants which diminish with increasing contaminant concentration. We show that such studies are the result of intrinsic zero order data plotted on a semilog graph, and involve zero order rate limitation by reactant saturation, electron transfer to O2, oxygen mass transfer, or light supply. 5. The apparent kinetics for contaminant removal from photocatalytic self-cleaning surfaces depends upon multiple circumstances, including the geometry of reactant deposit, catalyst porosity, and reactant light absorption. A single decision table suffices to indicate the apparent reaction order, n, to assume when fitting photocatalytic kinetic data from self-cleaning surfaces to a power law rate form, rate = k Cn.}, journal={FRONTIERS IN CHEMISTRY}, author={Ollis, David F.}, year={2018}, month={Aug} }
 @article{ollis_2017, title={Removal kinetics of stearic acid discrete deposits on photocatalytic self-cleaning surfaces: Effect of deposit initial size distribution}, volume={209}, ISSN={["1873-3883"]}, DOI={10.1016/j.apcatb.2017.02.029}, abstractNote={Earlier reports by Sawunyama et al. (1997, 1999) and Ghazzal et al. (2011) used atomic force microscopy (AFM) and optical microscopy to characterize the structure of stearic acid (SA) deposits on polycrystalline TiO2 films and Ti [110] crystal surfaces. Their preparation methods and catalysts yielded island-like SA deposits, rather than continuous films, for stearic acid submonolayers and multi-layers. Ghazzal observed that individual islands showed disappearance kinetics to be zero order with respect to island area, but apparently first order with respect to total SA remaining. We develop here kinetic models which are consistent with these “island” findings and establish the guidelines for apparent kinetic order of reaction, n: 1. Island deposits of a single size will exhibit apparent zero order kinetics., n = 0. 2. Island deposits with a narrow distribution of island sizes will exhibit an apparent half order behavior, n = 0.5. 3. Island deposits with a broad size distribution will exhibit an apparent reaction order of unity, n = 1. Our conclusion is that meaningful kinetic analysis of SA island photocatalyzed disappearance, and thus that of any oxidizable, carbonaceous pollutant which deposits in island form, rather than as a continuous film, requires knowledge of the initial island size distribution. The SA deposits may also undergo significant rearrangement as the titania surface is illuminated, quickly transforming the latter from hydrophobic to hydrophilic. Thus it is the reactant film and/or island distribution after initiation of illumination which is most relevant to kinetic modeling attempts.}, journal={APPLIED CATALYSIS B-ENVIRONMENTAL}, author={Ollis, David}, year={2017}, month={Jul}, pages={174–182} }
 @article{ollis_mills_lawrie_2016, title={Kinetics of methylene blue (MB) photocatalyzed reduction and dark regeneration in a colorimetric oxygen sensor}, volume={184}, ISSN={["1873-3883"]}, DOI={10.1016/j.apcatb.2015.11.011}, abstractNote={Performance data for a dye based, regenerable oxygen sensor (Mills and Lawrie [1], Mills et al. [2]) are analyzed to develop useful kinetic models for sensor photoactivation (dye reduction) and dark, oxygen detection (dye oxidation). The titania loaded, thin film sensor exhibits an apparent first order photoactivation of the dye, which we demonstrate (Section 3.2 and Fig. 4) is due to a kinetic disguise of a zero order photoreaction occurring through a non-uniformly illuminated sensor film. The observed zero order, slow recovery due to dye oxidation by dioxygen (O2 detection) appears best rationalized by a model assuming a near O2-impermeable skin developing on the sensor surface as solvent is evaporatively removed following sensor film casting and curing.}, journal={APPLIED CATALYSIS B-ENVIRONMENTAL}, author={Ollis, David and Mills, Andrew and Lawrie, Katherine}, year={2016}, month={May}, pages={201–207} }
 @article{ollis_2016, title={The well stirred liquid phase photochemical reactor: Laboratory tool or master of disguises?}, volume={19}, DOI={10.1515/jaots-2016-0202}, abstractNote={Abstract}, number={2}, journal={Journal of Advanced Oxidation Technologies}, author={Ollis, D.}, year={2016}, pages={192–198} }
 @article{le bechec_kinadjian_ollis_backov_lacombe_2015, title={Comparison of kinetics of acetone, heptane and toluene photocatalytic mineralization over TiO2 microfibers and Quartzel (R) mats}, volume={179}, ISSN={["1873-3883"]}, DOI={10.1016/j.apcatb.2015.05.015}, abstractNote={The kinetic parameters for VOCs (acetone, toluene, heptane) mineralization of lab-extruded pure TiO2 fibers prepared under easily scalable conditions were compared with those of a commercial photocatalytic media from Saint-Gobain, Quartzel®, under identical conditions. A flow-through recirculating reactor loop with variable LEDs irradiation at 365 nm was specially designed. All the experiments were carried out in a continuous recycle mode. Both types of fibers were very efficient for acetone and heptane mineralization. At 20% relative humidity (RH), the reaction rates were higher with the commercial media, whereas at 60% RH the catalysts displayed equal activity for acetone conversion. Toluene mineralization was much faster on these lab-made fibers than on Quarztel®, which was more sensitive to poisoning by reaction by-products. At 20% relative humidity, with the lab-made TiO2 fibers, typical quantum efficiencies were, respectively, 0.0106 and 0.0027 for acetone and heptane (100 ppmV initial concentration) and 0.0024 for toluene (200 ppmV initial concentration) while these quantum efficiencies were 0.0358, 0.0133 and 0.0011 with expanded Quartzel fibers under the same conditions. These results evidence a clear difference in the VOCs, water and polar by-products adsorption between these two kinds of fibers. These newly developed fibers can be produced at an industrial scale with a proven efficiency for VOCs degradation and mineralization. Since they are less sensitive to humidity than the commercial fibers, they could be most useful under actual ambient air conditions. These fibers present a good alternative to other commercially available photocatalytic media for gas phase purification.}, journal={APPLIED CATALYSIS B-ENVIRONMENTAL}, author={Le Bechec, M. and Kinadjian, N. and Ollis, D. and Backov, R. and Lacombe, S.}, year={2015}, month={Dec}, pages={78–87} }
 @article{ollis_2015, title={Photocatalyzed and photosensitized conversion of organic dyes on porous and non-porous air–solid surfaces: Kinetic models reconsidered}, volume={165}, ISSN={0926-3373}, url={http://dx.doi.org/10.1016/J.APCATB.2014.09.039}, DOI={10.1016/J.APCATB.2014.09.039}, abstractNote={The use of organic dyes to assay photocatalyst activity in air–solid systems has been explored frequently in recent years. We earlier proposed a two step kinetic model for photcatalyzed conversion of dyes in sub-monolayer and multi-layer deposits on titania films and powders. The present paper reconsiders both our own work and that of other researchers to propose more fundamental kinetic models which include the influence of illumination profiles within porous films and powder layers. The new models are shown to rationalize results for dye-photocatalyst data from multiple laboratories published over the last two decades. This outcome indicates that different kinetic analyses must be used to obtain rate constants in non-porous, uniformly illuminated systems (e.g., self-cleaning glasses) vs. porous systems such as thick macro- and meso-porous layers and powders, which exhibit illumination intensity variation with depth.}, journal={Applied Catalysis B: Environmental}, publisher={Elsevier BV}, author={Ollis, David}, year={2015}, month={Apr}, pages={111–116} }
 @article{ollis_silva_faria_2015, title={Simultaneous photochemical and photocatalyzed liquid phase reactions: Dye decolorization kinetics}, volume={240}, ISSN={["1873-4308"]}, DOI={10.1016/j.cattod.2014.03.062}, abstractNote={Both dyes and semiconductor photocatalysts are strong absorbers of near UV (365) and UV (254) nm wavelengths. Dye degradation may initiate via direct photolysis (254 nm), photocatalysis (254 or 365 nm), and photosensitized conversions (visible). When reactant and photocatalyst compete for photons, kinetic disguises may easily arise and must be recognized to properly interpret kinetic data from these multi-reaction systems. We published a 1990 simple kinetic analysis for liquid phase reactors involving simultaneous heterogeneous and homogeneous photochemical reactions. This circumstance applies to many of the approximately 6000 papers published to date on dye photo-degradation. While these reaction models may become complex in large reactors, the lab scale photoreactor provides simple lamp immersion geometries which allow for a clean separation of the relative weights carried by each available reaction path for dye degradation. In multiple cases, the proper consideration of the relative optical density of the dye solution and the photocatalyst suspension is not appreciated, leading to incomplete or incorrect kinetic interpretations. We analyze two detailed literature examples of dye conversions involving simultaneous homogeneous and heterogeneous photochemistries, and demonstrate kinetic disguises when dye conversion appears to be zero order from initial rate data, but first order due to linear ln(C) vs. time plots. We show that either light limitations or mass transfer limitations may be responsible for these kinetic disguises. These results may be followed in time qualitatively through use of a simple graph from our 1990 paper showing the regimes for the [relative absorbance × quantum yields] for heterogeneous vs. homogeneous reactions.}, journal={CATALYSIS TODAY}, author={Ollis, David and Silva, Claudia Gomes and Faria, Joaquim}, year={2015}, month={Feb}, pages={80–85} }
 @inproceedings{cooper_bullard_peretti_ollis_2012, title={Application of plagiarism screening software in the chemical engineering curriculum}, booktitle={ASEE Annual Conference Proceedings}, author={Cooper, M. and Bullard, L. and Peretti, S. and Ollis, D.}, year={2012} }
 @article{ollis_2010, title={Kinetics of photocatalyzed film removal on self-cleaning surfaces: Simple configurations and useful models}, volume={99}, ISSN={["0926-3373"]}, DOI={10.1016/j.apcatb.2010.06.029}, abstractNote={We develop simple reaction kinetic models for photocatalyzed removal of carbonaceous and sulfur films, and demonstrate their applicability to a common range of deposited film-catalyst configurations studied in the photocatalyst literature: Non-porous photocatalyst, non-porous transparent organic overlayer (stearic, palmitic acids). Porous photocatalyst: transparent organic (stearic acid) in catalyst void volume. Non-porous photocatalyst, non-transparent porous overlayer (sulfur). Non-porous photocatalyst, adjacent organic layer (soot). In each case, we consider a simple film-catalyst configuration, propose a corresponding one-dimensional physical model for reaction, and compare model results with literature data to evaluate the correspondence between model and experiment. These examples cover both direct and lateral oxidation by photocatalysis. The respective physical and chemical phenomena which determine these rates of film removal include intrinsic catalyst kinetics (1), simultaneous reaction and light attenuation (2), reaction with light absorption by non-transparent organic film (3), and oxidant lateral transport (surface diffusion) (4). In each case, a simple model suffices to represent the key kinetic phenomena. In all cases, the true kinetic order is zero, but the apparent order may be influenced by light absorption (case 2). The apparent rate constant may be influenced by catalyst light absorption (case 2) or overlayer (case 3), or by catalyst–reactant separation (case 4).}, number={3-4}, journal={APPLIED CATALYSIS B-ENVIRONMENTAL}, author={Ollis, David}, year={2010}, month={Sep}, pages={478–484} }
 @article{ollis_pichat_serpone_2010, title={TiO2 photocatalysis-25 years Preface}, volume={99}, ISSN={["0926-3373"]}, DOI={10.1016/j.apcatb.2010.06.030}, abstractNote={Water splitting, through electrochemical and photochemical methods, is a promising approach for large-scale hydrogen production. However, the efficiency of these methods is hindered by the water-oxidation reaction (WOR). A variety of Mn complexes have been explored as potential models for water-oxidizing complex in Photosystem II. Among different Mn complexes, [H2O(terpy)MnIII(μ-O)2MnIV(terpy)H2O](NO3)3 (1, terpy = 2,2’:6′2″-terpyridine) has been extensively studied under WOR conditions. In this study, the reactivity of 1 is investigated when loaded onto TiO2 nanoparticles and subjected to photochemical conditions. Our main goal was to identify possible products that could arise from the conversion of 1 given the specified conditions. After conducting various analytical methods, it was determined that the reaction yielded MnOx and Mn(II) species as the resulting reaction products. These findings offer valuable insights into the progress of advanced WOR catalysts and the underlying mechanism of efficient water splitting for energy storage.}, number={3-4}, journal={APPLIED CATALYSIS B-ENVIRONMENTAL}, author={Ollis, David and Pichat, Pierre and Serpone, Nick}, year={2010}, month={Sep}, pages={377–377} }
 @article{chin_grant_ollis_2009, title={Quantitative photocatalyzed soot oxidation on titanium dioxide}, volume={87}, ISSN={["1873-3883"]}, DOI={10.1016/j.apcatb.2008.09.020}, abstractNote={Abstract We report here the titanium dioxide (TiO 2 ) photocatalyzed oxidation of deposited hurricane lamp soot. Sol–gel derived TiO 2 was coated on quartz crystal microbalance (QCM) elements. Characterization by spectroscopic ellipsometry ( SE ) and atomic force microscopy (AFM) revealed low surface roughness of 0–17%, and SE showed a linear variation of the TiO 2 thickness versus the number of sol–gel spin coats. Soot was deposited on the calcined TiO 2 film using an analytical rotor passing through a hurricane lamp flame, and subsequently irradiated with near-UV light. Varying the soot mass on the TiO 2 -coated QCM crystals revealed behaviors over 20,000 min ranging from total soot destruction of a single pass soot layer to minimal oxidation of an eight pass soot layer, the latter caused by soot screening of the incident UV light. A series/parallel reaction mechanism [P. Chin, G.W. Roberts, D.F. Ollis, Industrial & Engineering Chemistry Research 46 (2007) 7598] developed to describe previous literature data on TiO 2 -catalyzed soot photooxidation was successfully employed to capture the longer time changes in presumably graphitic soot mass as a function of UV illumination time from 1000 to 20,000 min and of soot layer thickness. Short time soot mass loss is attributed to oxidation of organic carbons deposited on the graphitic soot components. This kinetic model can be used to predict the rate of TiO 2 -catalyzed soot destruction as a function of near-UV illumination time and initial soot layer thickness.}, number={3-4}, journal={APPLIED CATALYSIS B-ENVIRONMENTAL}, author={Chin, Paul and Grant, Christine S. and Ollis, David F.}, year={2009}, month={Apr}, pages={220–229} }
 @article{ollis_kennedy_granger_brent_2008, title={Addressing 'engineering solutions in global and societal context' through an integrated foreign language immersion experience}, volume={24}, number={2}, journal={International Journal of Engineering Education}, author={Ollis, D. F. and Kennedy, A. and Granger, M. and Brent, R.}, year={2008}, pages={304–313} }
 @article{chin_ollis_2008, title={Design approaches for a cycling adsorbent/photocatalyst system for moor air purification: Formaldehyde example}, volume={58}, ISSN={["1047-3289"]}, DOI={10.3155/1047-3289.58.4.494}, abstractNote={Abstract A kinetic model for a cycling adsorbent/photocatalyst combination for formaldehyde removal in indoor air (Chin et al. J. Catalysis 2006, 237, 29-37) was previously developed in our lab, demonstrating agreement with lab-scale batch operation data of other researchers (Shiraishi et al. Chem. Engineer. Sci. 2003, 58, 929-934). Model parameters evaluated included adsorption equilibrium and rate constants for the adsorbent (activated carbon) honeycomb rotor, and catalytic rate constant for pseudo-first-order formaldehyde destruction in the titanium dioxide photoreactor. This paper explores design consequences for this novel system. In particular, the batch parameter values are used to model both adsorbent and photocatalyst behavior for continuous operation in typical residential home challenges. Design variables, including realistic make-up air fraction, adsorbent honeycomb rotation speed, and formaldehyde source emission rate, are considered to evaluate the ability of the system to achieve World Health Organization pollutant guidelines. In all circumstances, the size of the required rotating adsorbent bed and photoreactor for single-stage operation and the resultant formaldehyde concentration in the home are calculated. The ability of how well such a system might be accommodated within the typical dimensions of commercial ventilation ducts is also considered.}, number={4}, journal={JOURNAL OF THE AIR & WASTE MANAGEMENT ASSOCIATION}, author={Chin, Paul and Ollis, David F.}, year={2008}, month={Apr}, pages={494–501} }
 @article{chin_ollis_2007, title={Decolorization of organic dyes on Pilkington Activ (TM) photocatalytic glass}, volume={123}, ISSN={["0920-5861"]}, DOI={10.1016/j.cattod.2007.01.069}, abstractNote={The air–solid photocatalytic degradation of organic dye films Acid Blue 9 (AB9) and Reactive Black 5 (RBk5) is studied on Pilkington Activ™ glass. The Activ™ glass comprises of a colorless TiO2 layer deposited on clear glass. The Activ™ glass is characterized using atomic force microscopy (AFM) and X-ray diffraction (XRD). Using AFM, the TiO2 average agglomerate particle size is 95 nm, with an apparent TiO2 thickness of 12 nm. The XRD results indicate the anatase phase of TiO2, with a calculated crystallite size of 18 nm. Dyes AB9 and RBk5 are deposited in a liquid film and dried on the Activ™ glass to test for photodecolorization in air, using eight UVA blacklight-blue fluorescent lamps with an average UVA irradiance of 1.4 mW/cm2. A novel horizontal coat method is used for dye deposition, minimizing the amount of solution used while forming a fairly uniform dye layer. About 35–75 monolayers of dye are placed on the Activ™ glass, with a covered area of 7–10 cm2. Dye degradation is observed visually and via UV–vis spectroscopy. The kinetics of photodecolorization satisfactorily fit a two-step series reaction model, indicating that the dye degrades to a single colored intermediate compound before reaching its final colorless product(s). Each reaction step follows a simple irreversible first-order reaction rate form. The average k1 is 0.017 and 0.021 min−1 for AB9 and RBk5, respectively, and the corresponding average k2 is 2.0 × 10−3 and 1.5 × 10−3 min−1. Variable light intensity experiments reveal a p = 0.44 ± 0.02 exponent dependency of initial decolorization rate on the UV irradiance. Solar experiments are conducted outdoors with an average temperature, water vapor density, and UVA irradiance of 30.8 °C, 6.4 g water/m3 dry air, and 1.5 mW/cm2, respectively. For AB9, the average solar k1 is 0.041 min−1 and k2 is 5.7 × 10−3 min−1.}, number={1-4}, journal={CATALYSIS TODAY}, author={Chin, Paul and Ollis, David F.}, year={2007}, month={May}, pages={177–188} }
 @article{chin_roberts_ollis_2007, title={Kinetic Modeling of photocatalyzed soot oxidation on titanium dioxide thin films}, volume={46}, ISSN={["0888-5885"]}, DOI={10.1021/ie070083t}, abstractNote={Recent research [Mills et al. Chemosphere 2006, 64, 1032−1035; Lee and Choi J. Phys. Chem. B 2002, 106, 11818−11822] has demonstrated photocatalytic oxidation of “soot” by titanium dioxide thin films. However, little attention has been paid to developing kinetic models of photocatalyzed soot destruction. We develop here a series/parallel kinetic model for soot oxidation and use it to analyze the CO2 data of Mills et al. and the mass loss data of Lee and Choi. The model assumes two oxidation pathways:  a single step yielding CO2 directly and a serial sequence through a solid intermediate species, which is subsequently oxidized to CO2. We extend this simple model to include variable O2 partial pressure, which is used to evaluate the initial CO2 data of Lee and Choi. These models fit the experimental CO2 data of Mills et al. and Lee and Choi well. The simple kinetic model also describes the mass loss data of Lee and Choi for the front mode of sample irradiation.}, number={23}, journal={INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH}, author={Chin, Paul and Roberts, George W. and Ollis, David F.}, year={2007}, month={Nov}, pages={7598–7604} }
 @article{mills_wang_ollis_2006, title={Dependence of the kinetics of liquid-phase photocatalyzed reactions on oxygen concentration and light intensity}, volume={243}, ISSN={["1090-2694"]}, DOI={10.1016/j.jcat.2006.06.025}, abstractNote={The initial kinetics of the oxidation of 4-chlorophenol, 4-CP, photocatalyzed by titania films and aqueous dispersions were studied as a function of oxygen partial pressure, PO2, and incident light intensity, I. The reaction conditions were such that the kinetics were independent of [4-CP] but strongly dependent on PO2—a situation that allowed investigation of the less-often studied kinetics of oxygen reduction. The observed kinetics fit a pseudo-steady-state model in which the oxygen is Langmuir-adsorbed on the titania photocatalyst particles before being reduced by photogenerated electrons. The maximum rate of photocatalysis depends directly on Iβ, where β=1 for films and 0.7 for dispersions of titania, indicating that the kinetics are dominated by the surface reactions of the photogenerated electrons and holes for the films and by direct recombination for the powder dispersions. Using the pseudo-first-order model, for both titania films and dispersions, the apparent Langmuir adsorption constant, KLH, derived from a Langmuir–Hinshelwood analysis of the kinetics, appears to be largely independent of incident light intensity, unlike KLH for 4-CP. Consequently, similar values are obtained for the Langmuir adsorption constant, Kads, extracted from a pseudo-steady-state analysis of the kinetics for oxygen on TiO2 dispersions and films in aqueous solution (i.e., ca. 0.0265±0.005kPa−1), and for both films and dispersions, oxygen appears to be weakly adsorbed on TiO2 compared with 4-CP, at a rate that would take many minutes to reach equilibrium. The value of Kads for oxygen on titania particles dispersed in solution is ca. 4.7 times lower than that reported for the dark Langmuir adsorption isotherm; possible causes for this difference are discussed.}, number={1}, journal={JOURNAL OF CATALYSIS}, author={Mills, Andrew and Wang, Jishun and Ollis, David F.}, year={2006}, month={Oct}, pages={1–6} }
 @article{chin_yang_ollis_2006, title={Formaldehyde removal from air via a rotating adsorbent combined with a photocatalyst reactor: Kinetic modeling}, volume={237}, ISSN={["1090-2694"]}, DOI={10.1016/j.jcat.2005.10.013}, abstractNote={A novel rotating honeycomb adsorbent coupled with a photocatalytic reactor demonstrated by Shiraishi et al. is modeled here. In operation, the air pollutant formaldehyde was adsorbed from a simulated room (10 m3) onto a slowly rotating honeycomb, which then passed slowly through a small chamber (0.09 m3) in which locally recirculated heated air desorbed the formaldehyde and carried it through a photocatalytic reactor, which oxidized the desorbed material. The regenerated rotor-adsorbent then rotated back into the airtight chamber. This system was modeled at steady states and transient states to determine adsorption, desorption, and photocatalyst pseudo-first-order rate constants at the appropriate temperatures (ambient temperature for adsorption, 120–180 °C for desorption and photocatalysis). Intensity-corrected values for the photocatalytic rate constant kcat (cm2/(mW s)) deduced from fitting our model to the data of Shiraishi et al. were in good agreement with those calculated from five literature reports for formaldehyde photocatalytic destruction.}, number={1}, journal={JOURNAL OF CATALYSIS}, author={Chin, P and Yang, LP and Ollis, DF}, year={2006}, month={Jan}, pages={29–37} }
 @article{julson_ollis_2006, title={Kinetics of dye decolorization in an air-solid system}, volume={65}, ISSN={["1873-3883"]}, DOI={10.1016/j.apcatb.2005.12.021}, abstractNote={The photocatalytic decolorization of adsorbed organic dyes (Acid Blue 9, Acid Orange 7, Reactive Black 5 and Reactive Blue 19) in air was examined, applicable to self-cleaning surfaces and catalyst characterization. Dye-coated Degussa P25 titanium dioxide (TiO2) and dye-coated photo-inert aluminum oxide (Al2O3) particles, both of sub-monolayer initial dye coverage, were illuminated with 1.3 mW cm−2 of near-UV light. Visual evidence of color removal is reported with photographic images. Two methods, Indirect and Direct Analysis, were employed to quantitatively examine the decolorization kinetics of dyes using UV–visible transmission and diffuse reflectance spectroscopy, respectively. A decrease in dye concentration with time was observed with near-UV illumination of dye-coated TiO2 powders for all dyes. Dyes did not photodegrade significantly on photo-inert Al2O3. UV–visible spectroscopy data was used to model the kinetics of the photocatalytic degradation. Two first-order reactions in series provided the most convincing rate form for the photodegradation of dyes adsorbed to TiO2, with a first step the conversion of colored dye to colored intermediate, and the second the conversion to colorless product(s). The first rate constant was of similar magnitude for all dyes, averaging k1 = 0.13 min−1. Similarly, for the second, k2 = 0.0014 min−1.}, number={3-4}, journal={APPLIED CATALYSIS B-ENVIRONMENTAL}, author={Julson, Alison J. and Ollis, David F.}, year={2006}, month={Jun}, pages={315–325} }
 @article{mills_wang_ollis_2006, title={Kinetics of liquid phase semiconductor photoassisted reactions: Supporting observations for a pseudo-steady-state model}, volume={110}, ISSN={["1520-5207"]}, DOI={10.1021/jp062317c}, abstractNote={The kinetics of liquid phase semiconductor photocatalytic and photoassisted reactions are an area of some debate, reignited recently by an article by Ollis(1) in which he proposed a simple pseudo-steady-state model to interpret the Langmuir-Hinshelwood type kinetics, commonly observed in such systems. In the current article, support for this model, over other models, is provided by a reinterpretation of the results of a study, reported initially in 1999,(2) of the photoassisted mineralization of 4-chlorophenol, 4-CP, by titania films and dispersions as a function of incident light intensity, I. On the basis of this model, these results indicate that 4-CP is adsorbed more strongly on P25 TiO2 when it is in a dispersed, rather than a film form, due to a higher rate constant for adsorption, k(1). In addition, the kinetics of 4-CP removal appear to depend on I(beta), where beta = 1 or 0.6 for when the TiO2 is in a film or a dispersed form, respectively. These findings are discussed both in terms of the pseudo-steady-state model and other popular kinetic models.}, number={29}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Mills, Andrew and Wang, Jishun and Ollis, David F.}, year={2006}, month={Jul}, pages={14386–14390} }
 @article{ollis_krupczak_2006, title={Teaching technology literacy: An opportunity for design faculty?}, volume={22}, number={3}, journal={International Journal of Engineering Education}, author={Ollis, D. and Krupczak, J.}, year={2006}, pages={665–670} }
 @article{passos_felder_fleming_mcfeeters_ollis_2005, title={Dynamic model for mass transfer of solutes in cucumber fermentation}, volume={68}, ISSN={["0260-8774"]}, DOI={10.1016/j.jfoodeng.2004.06.002}, abstractNote={A mathematical model for the mass transfer of solutes between whole cucumbers and brine in cucumber fermentation has been developed that takes into account permeation of solutes through stomata in the cucumber skin and through the epidermal cells in the skin, as well as film diffusion through the surrounding brine boundary layer. The model was used to fit experimental data for the time-dependent concentrations of solutes that permeate into the cucumbers (glucose and malate) and out of them (lactic acid, acetic acid, ethanol, and sodium chloride). The rate of lactic acid transport through the stomata was found to be three orders of magnitude greater than that through the epidermis, and the permeabilities of lactic and acetic acids were effectively independent of the brine circulation rate. These results indicate that the rate of permeation of solutes into and out of cucumbers was controlled by mass transfer through the stomata, with neither film diffusion nor epidermal diffusion having a significant effect. The model differential equation for solute transfer combined with a set of rate equations for microbial growth will provide a good basis to establish a complete mechanistic model for the cucumber fermentation process.}, number={3}, journal={JOURNAL OF FOOD ENGINEERING}, author={Passos, FV and Felder, RM and Fleming, HP and McFeeters, RF and Ollis, DF}, year={2005}, month={Jun}, pages={297–302} }
 @article{ollis_2005, title={Kinetic disguises in heterogeneous photocatalysis}, volume={35}, ISSN={["1572-9028"]}, DOI={10.1007/s11244-005-3827-z}, number={3-4}, journal={TOPICS IN CATALYSIS}, author={Ollis, DF}, year={2005}, month={Jul}, pages={217–223} }
 @article{ollis_2005, title={Kinetics of liquid phase photocatalyzed reactions: An illuminating approach}, volume={109}, ISSN={["1520-6106"]}, DOI={10.1021/jp040236f}, abstractNote={Analysis of photocatalyst kinetics to date have relied largely on Langmuir-Hinshelwood rate forms, which assume equilibrated adsorption of reactants and, correspondingly, a slow, rate-controlling surface step. Alternatively, and more generally, a pseudo-steady state analysis based upon the stationary state hypothesis for reaction intermediates may be applied. We show here that only this second approach is consistent with the reported intensity dependence of apparent adsorption (and desorption) binding constants, as well as the catalytic rate constant. In consequence, we show that for at least some photocatalyzed reactions, adsorption/desorption reaction equilibria are not established during reaction, because the substantial reactivity of an adsorbed active species (e.g., hole (h+), radical (*OH), etc.) causes a continued displacement from equilibrium of the adsorbed reactant concentration.}, number={6}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Ollis, DF}, year={2005}, month={Feb}, pages={2439–2444} }
 @article{ollis_2004, title={Basic elements of multidisciplinary design courses and projects}, volume={20}, number={3}, journal={International Journal of Engineering Education}, author={Ollis, D. F.}, year={2004}, pages={391–397} }
 @article{esplugas_contreras_ollis_2004, title={Engineering aspects of the integration of chemical and biological oxidation: Simple mechanistic models for the oxidation treatment}, volume={130}, DOI={10.1061/(asce)0733-9372(2004)130:9(967)}, abstractNote={Oxidation processes can oxidize biorecalcitrant compounds into biodegradable intermediates, which in turn can be treated less expensively by a subsequent biological process. To design such a two-step (chemical+biological) process to treat poorly characterized wastewaters, it is useful to model the time evolution of characteristic global variables, chemical oxygen demand (COD) and biochemical oxygen demand (BOD), in order to develop a useful treatment strategy based upon these classical variables. We consider two simple model reaction networks, requiring three- and five-rate constants, respectively. The first model, proposed recently, involves conversion of a nonbiodegradable species, C, into a single biodegradable intermediate S. Here, biodegradable compounds are immediate kinetic products of oxidation. In general, it is not probable that a single recalcitrant compound undergoes a single-step reaction to CO\D\N. However, when working with complex undefined wastewaters streams, single-step reactions may be used to simplify. The second new model corresponds to a lag time in BOD formation due to the necessity of multiple partial oxidations to reach a first biodegradable intermediate. The second network includes two intermediates, I and S, which are, respectively, nonbiodegradable and biodegradable. We then compare model behavior with an unfortunately sparse literature on BOD and COD values versus time in chemical reactors, and demonstrate the convenience of the first model, and the occasional necessity of the second, which reflects the presence of early intermediates which are nonbiodegradable.}, number={9}, journal={Journal of Environmental Engineering (New York, N.Y.)}, author={Esplugas, S. and Contreras, S. and Ollis, D. F.}, year={2004}, pages={967–974} }
 @inbook{brown_luyendyk_ollis_2004, title={Implementing an English and Engineering collaboration}, booktitle={Liberal education in twenty-first century engineering: responses to ABET/EC 2000 criteria  (WPI studies ; v. 23)}, publisher={New York: Peter Lang}, author={Brown, A. and Luyendyk, S. and Ollis, D. F.}, editor={D. F. Ollis, K. A. Neeley and Luegenbiehl, H. C.Editors}, year={2004}, pages={270–279} }
 @book{liberal education in twenty-first century engineering: responses to abet/ec 2000 criteria_2004, ISBN={0820449245}, publisher={New York: Peter Lang}, year={2004} }
 @article{lewandowski_ollis_2003, title={A Two-Site kinetic model simulating apparent deactivation during photocatalytic oxidation of aromatics on titanium dioxide (TiO2)}, volume={43}, ISSN={["0926-3373"]}, DOI={10.1016/S0926-3373(02)00310-7}, abstractNote={Continuous photocatalytic oxidation of aromatic contaminants at 10 ppm or above generally leads to apparent catalyst deactivation. This deactivation has been attributed to the accumulation of recalcitrant intermediate species on the catalyst surface. In the present study, two variations of a simple kinetic model for the transient photocatalytic oxidation of an aromatic contaminant are considered. Modeling results are compared to our experimental data for the gas-phase photocatalytic oxidation of benzene, toluene, and m-xylene. A kinetic model using a single type of adsorption site is unable to replicate the experimental results. A second model, using a Two-Site arrangement, was developed based upon studies addressing multi-site binding of alcohols and other oxygenated hydrocarbons. This Two-Site kinetic model was able to produce results consistent with experimental data.}, number={4}, journal={APPLIED CATALYSIS B-ENVIRONMENTAL}, author={Lewandowski, M and Ollis, DF}, year={2003}, month={Jul}, pages={309–327} }
 @article{lewandowski_ollis_2003, title={Extension of a Two-Site transient kinetic model of TiO2 deactivation during photocatalytic oxidation of aromatics: concentration variations and catalyst regeneration studies}, volume={45}, ISSN={["0926-3373"]}, DOI={10.1016/S0926-3373(03)00165-6}, abstractNote={In our previous studies, three variations of a kinetic model for the transient gas–solid photocatalytic oxidation of aromatic contaminants on titanium dioxide (TiO2) were developed and compared with experimental data. Two of the models, based upon a single type of catalyst site, were not capable of replicating transient experimental data from the photocatalytic oxidation of benzene, toluene, or m-xylene in air at a single feed concentration (50 mg/m3). The remaining kinetic model, the Two-Site model, presumed the presence of a more hydrophilic type of site and was capable of replicating the time-varying behavior seen with all three aromatic contaminants considered. In the present study, this Two-Site kinetic model is extended to separately consider the photocatalytic oxidation of gas-phase toluene at various feed concentrations (20–100 mg/m3) and the regeneration of used catalysts via flowing, humidified air and UV illumination. Our Two-Site model provides reasonable fits for experimental data collected during the photocatalytic oxidation of toluene at several concentration levels with no significant changes to the prior model. It is also capable of representing catalyst regeneration, although some significant differences between the model predictions and experimental results are noted.}, number={3}, journal={APPLIED CATALYSIS B-ENVIRONMENTAL}, author={Lewandowski, M and Ollis, DF}, year={2003}, month={Oct}, pages={223–238} }
 @article{lewandowski_ollis_2003, title={Halide acid pretreatments of photocatalysts for oxidation of aromatic air contaminants: rate enhancement, rate inhibition, and a thermodynamic rationale}, volume={217}, ISSN={["0021-9517"]}, DOI={10.1016/S0021-9517(03)00030-7}, abstractNote={The effects of chlorine radical generation during the photocatalytic oxidation of aromatic contaminants in air can be significant. Previous studies have shown that cofeeding chlorinated olefins (TCE, PCE) may increase the removal of branched aromatics (toluene, xylenes), presumably by initiating chlorine radical chain reactions. Hydrochloric acid catalyst pretreatments produce a similar enhancement of aromatic conversions. However, both approaches were ineffective for rate enhancement toward benzene, while hydrobromic and hydriodic acid pretreatments diminished the photocatalytic oxidation of both benzene and toluene. The present study broadens this halide acid inquiry to include hydrofluoric acid catalyst pretreatments and to examine halide acid influences on the removal of m-xylene as well. Only HCl pretreatments enhanced activity, and only for the branched aromatics (toluene and m-xylene). These results appear consistent with a thermodynamic analysis proposed here, which indicates that (1) fluorine radical generation is not energetically feasible under the conditions considered, (2) bromine and iodine radical generation is energetically feasible, but the radicals are insufficiently reactive to initiate the degradation of aromatics, and (3) chlorine radicals are predicted to be sufficiently energetic to abstract hydrogen from the methyl groups of branched aromatics, but not from the more strongly bound hydrogen atoms on the aromatic ring. These calculations are all in accord with our experimental results for the photocatalytic oxidation aromatics. The consistency of these thermodynamic arguments is also further support for the presumed halide radical pathway for rate enhancement.}, number={1}, journal={JOURNAL OF CATALYSIS}, author={Lewandowski, M and Ollis, DF}, year={2003}, month={Jul}, pages={38–46} }
 @inbook{ollis_2003, title={Integrating photocatalysis and membrane technologies for water treatment}, volume={984}, ISBN={3540007318}, booktitle={Advanced membrane technology}, publisher={New York, NY: New York Academy of Sciences}, author={Ollis, D. F.}, year={2003}, pages={65–84} }
 @article{contreras_ollis_esplugas_2003, title={Sequential ozonation and biological oxidation of wastewaters: A model including biomass inhibition by residual oxidant}, volume={25}, ISSN={["1547-6545"]}, DOI={10.1080/713610664}, abstractNote={We modeled the potential impact of a residual oxidant (ozone in the present case, known to be a strong bactericide) on the performance of a combined chemical and biological water treatment. This model is fashioned by adapting a recent model for the kinetics of ozone disinfection to an activated sludge system performing in the presence of ozone residuals. Our new model allows prediction of the bioreactor performance under different substrate loadings and residual oxidant concentrations, helping to identify regimes where air stripping would be necessary before the second step.}, number={2}, journal={OZONE-SCIENCE & ENGINEERING}, author={Contreras, S and Ollis, DF and Esplugas, S}, year={2003}, month={Apr}, pages={95–105} }
 @article{lewandowski_ollis_2002, title={Effects of TiO2 pretreatments on the photocatalytic oxidation of gas-phase aromatic contaminants}, volume={5}, DOI={10.1515/jaots-2002-0105}, abstractNote={Abstract}, number={1}, journal={Journal of Advanced Oxidation Technologies}, author={Lewandowski, M. and Ollis, D. F.}, year={2002}, pages={33–40} }
 @inproceedings{ollis_felder_brent_2002, title={Introducing new faculty to multidisciplinary research collaboration}, number={2002 June}, booktitle={2002 ASEE Annual Conference Proceedings, ASEE, June 2002}, publisher={Washington, D.C.: American Society for Engineering Education}, author={Ollis, D. F. and Felder, R. M. and Brent, R.}, year={2002} }
 @article{ollis_2002, title={Photocatalytic powder layer reactor: A uniformly mixed gas phase occurring in a catalytic fixed-bed flow reactor}, volume={41}, ISSN={["0888-5885"]}, DOI={10.1021/ie020038f}, abstractNote={Integral conversion photocatalysis rate data in gas−solid studies have often been obtained through the use of a powder layer downflow laboratory reactor illuminated from above. The photocatalyst particles, characteristically 20−40 nm in primary particle size and ∼1 μm in agglomerate size, are illuminated to a characteristic depth of the reciprocal of the absorption coefficient, resulting in opacity at 30−50 μm in a loose-packed powder layer. We establish here that this photocatalytic membrane reactor behaves as a well-mixed system; thus, reaction kinetic models can be directly tested for any degree of reactant conversion, without prior need for rate integration.}, number={25}, journal={INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH}, author={Ollis, DF}, year={2002}, month={Dec}, pages={6409–6412} }
 @article{borrell-damian_ollis_2002, title={Sequential extraction and photocatalytic recovery of lead from model contaminated soils}, volume={5}, DOI={10.1515/jaots-2002-0106}, abstractNote={Abstract}, number={1}, journal={Journal of Advanced Oxidation Technologies}, author={Borrell-Damian, L. and Ollis, D. F.}, year={2002}, pages={41–57} }
 @article{ollis_2001, title={On the need for engineering models of integrated chemical and biological oxidation of wastewaters}, volume={44}, ISSN={["0273-1223"]}, DOI={10.2166/wst.2001.0265}, abstractNote={Experimental examples of sequential chemical and biological oxidation treatment have been previously reviewed by Scott and Ollis, and economic estimates proposed by Esplugas and Ollis. Despite the prevalence of examples evident in these reviews and in recent conferences, very little use of kinetic models to codify and rationalize results on complex or simulated wastewaters has appeared. In consequence, models are not widely available nor have they yet received widespread acceptance as a method of analysis and reporting. To ameliorate this situation we here report a summary of important kinetic behaviors characteristic of individual chemical and biological kinetics, and provide experimental examples from recent works which illustrate the utility of such simple kinetic forms to construct two step treatment engineering models for complex wastewater and waters.}, number={5}, journal={WATER SCIENCE AND TECHNOLOGY}, author={Ollis, DF}, year={2001}, pages={117–123} }
 @inproceedings{anderson_hoit_felder_brent_zorowski_ollis_ohland_phillips_2001, title={SUCCEED: a multiple university collaborative approach to systemic curriculum change}, number={2001 August}, booktitle={2001 International Conference on Engineering Education Proceedings, Oslo, Norway, August 2001}, author={Anderson, T. and Hoit, M. and Felder, R. and Brent, R. and Zorowski, C. and Ollis, D. and Ohland, M. and Phillips, H.}, year={2001} }
 @article{d'hennezel_ollis_2001, title={Surface prechlorination of anatase TiO(2) for enhanced photocatalytic oxidation of toluene and hexane}, volume={84}, ISSN={["0018-019X"]}, DOI={10.1002/1522-2675(20011114)84:11<3511::AID-HLCA3511>3.0.CO;2-K}, abstractNote={We report the influence of prechlorination of TiO2 powder on the activity for the photocatalyzed oxidation of hydrocarbons (toluene, hexane) and oxygenates (acetone, butan-1-ol). Water- and HCl-pretreated catalyst are prepared by impregnation of TiO2 powder in H2O and in HCl solutions, respectively, followed by drying at room temperature. X-Ray photoelectron spectroscopy (XPS) analysis demonstrates the surface prechlorination efficiency: 1 g of TiO2 impregnated with 3 ml of 3n HCl solution results in a chlorine surface concentration of 1.6%. Prechlorination results in a photo-oxidation-rate enhancement for toluene and hexane, no change for butan-1-ol, and inhibition for acetone. This pattern is the same as that demonstrated earlier by us when these reactants are co-fed with the chlorine source trichloroethylene (TCE).}, number={11}, journal={HELVETICA CHIMICA ACTA}, author={d'Hennezel, O and Ollis, DF}, year={2001}, pages={3511–3518} }
 @article{ollis_2000, title={Photocatalytic purification and remediation of contaminated air and water}, volume={3}, ISSN={["1387-1609"]}, DOI={10.1016/s1387-1609(00)01169-5}, abstractNote={Among the catalytic approaches to environmental remediation, that of heterogeneous photoassisted catalysis, known as ‘photocatalysis’, is the sole example involving utilization of light along with a catalytic solid. This paper surveys the broad range of emerging potential applications for water (contaminant destruction and removal, metal deposition and recovery, sterilization and disinfection) then for air (purification, decontamination, deodorization, bioaerosol removal, self-cleaning surfaces) and presents approaches to increase the efficiency of light and catalyst utilization via periodic illumination and oxidant (ozone, peroxide) addition. Purification photocatalytique et assainissement de l'air et de l'eau contaminées. Parmi les approches catalytiques visant à assainir l'environnement, la catalyse hétérogène photoassistée, connue sous le nom de « photocatalyse », constitue l'unique exemple d'utilisation combinée de la lumière et d'un catalyseur solide. Cet article brosse un panorama du large éventail d'applications potentielles émergentes pour l'eau (destruction et extraction des contaminants, déposition et récupération des métaux, stérilisation et désinfection), puis pour l'air (purification, décontamination, désodorisation, extraction des bioaérosols, surfaces autonettoyantes) ; il présente enfin des approches visant à accroı̂tre l'efficacité de l'utilisation de la lumière et du catalyseur à travers l'illumination périodique et l'addition d'oxydants (ozone, peroxyde).}, number={6}, journal={COMPTES RENDUS DE L ACADEMIE DES SCIENCES SERIE II FASCICULE C-CHIMIE}, author={Ollis, DF}, year={2000}, month={Jun}, pages={405–411} }
 @article{flickinger_mullick_ollis_1999, title={Construction of a thread coater and use of azocasein release to characterize the sealant coat porosity of fibers coated with latex biocatalytic coatings}, volume={15}, ISSN={["1520-6033"]}, DOI={10.1021/bp990026y}, abstractNote={A single‐stage annular fiber coating method with co‐current dry‐air drying at 30 °C has been developed for multilayer coating of 128 μm diameter polyester thread (yarn) with latex films as a model for enzyme immobilization and development of a filament biocatalytic filter. Acrylic vinyl acetate polymer coatings were sequentially metered onto the fibers by the combination of a flexible squeegee and a red rubber annulus. The thread coater can operate over a range of 0.07–1.37 m/min thread velocities while delivering a nearly constant and reproducible polymer loading of 30.8 ± 1.3 mg/m. A 100% polyester, 278.9 denier thread was precoated with latex to generate an approximately 369 denier sealed filament. The filament was then coated with a latex + sulfanilamide−azocasein mixture and sealed with a polymer top coat. The permeability of the polymer sealant top coat was characterized using entrapped azocasein as a tracer molecule and monitoring the azocasein release upon rehydration of the coated threads. Azocasein release rate decreased with curing time at 30 °C until 2 days and was invariant after 2–3 days of curing. A 282 mOsm rehydrating solution was sufficient to suppress increased azocasein release due to top coat blistering. No enhancement in the permeability of the top coat was observed when high molecular weight water soluble polymers (WSPs) were used as fillers. This probably results from the low WSP to latex ratio used (0.05–0.1) and the slow rate of WSP leaching compared to the release of azocasein. A method using 60–120 mesh silica was also developed to study the effect of mechanical abrasion of the coated threads as measured by azocasein release kinetics.}, number={3}, journal={BIOTECHNOLOGY PROGRESS}, author={Flickinger, MC and Mullick, A and Ollis, DF}, year={1999}, pages={383–390} }
 @article{chen_ollis_rulkens_bruning_1999, title={Kinetic processes of photocatalytic mineralization of alcohols on metallized titanium dioxide}, volume={33}, ISSN={["0043-1354"]}, DOI={10.1016/S0043-1354(98)00307-8}, abstractNote={The metallization of TiO2 photocatalyst with 1%Pt gave increasing rates of alcohol conversions and carbon dioxide production. A new porous powder micro-cell model was proposed. Heterogeneous reactions of photocatalytic oxidation, and final mineralizing to CO2, of methanol, ethanol in dilute (50–400 pm) aqueous solution should take place on the solid–liquid interface of the photocatalyst. It has similar kinetic behavior as reactions on the solid–gas interface of a heterogeneous catalyst. The process can be described by the Langmuir adsorption isotherm. These photocatalytic degradations can be expressed as a first-order reaction. Maximum rates of photocatalytic reactions and efficiencies can be estimated according to the calculation of surface coverage of certain compounds on TiO2. Because ethanol have the double coverage of methanol at same concentration, it is presumed that methanol and ethanol have the same adsorption state of the end-group on catalyst surfaces. In a closed reactor, if oxygen pressure was controlled at 76 cm H2O, its reduction rate was nearly of zero order.}, number={5}, journal={WATER RESEARCH}, author={Chen, J and Ollis, DF and Rulkens, WH and Bruning, H}, year={1999}, month={Apr}, pages={1173–1180} }
 @article{chen_ollis_rulkens_bruning_1999, title={Photocatalyzed deposition and concentration of soluble uranium(VI) from TiO(2) suspensions}, volume={151}, ISSN={["0927-7757"]}, DOI={10.1016/S0927-7757(98)00506-8}, abstractNote={A reversible, photocatalytic reductive deposition of uranium on TiO2 or Pt/TiO2 occurs in deaerated U(VI)/EDTA solutions, accompanied by CO2 released from the oxidation of EDTA. A maximum of 50–60% uranium(VI) is deposited and an ultimate CO2 release equivalent to a single decarboxylation of EDTA was reached under our experiment conditions no matter how long the illumination time. In aerated solutions, no uranium deposited, but a large CO2 release still occurred, presumably from EDTA mineralization. Nearly 100% of the deposited, reduced products from uranium(VI) on TiO2. Pt/TiO2 can be reoxidized and desorbed to regenerate dissolved uranium(VI) simply by solution exposure to air after illumination. The reductive deposition process can be repeated, indicating a potential cycle process. Modification of TiO2 with platinum has only a slight influence on this reductive deposition of uranium on TiO2.}, number={1-2}, journal={COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS}, author={Chen, J and Ollis, DF and Rulkens, WH and Bruning, H}, year={1999}, month={Jun}, pages={339–349} }
 @article{chen_ollis_rulkens_bruning_1999, title={Photocatalyzed oxidation of alcohols and organochlorides in the presence of native TiO2 and metallized TiO2 suspensions. Part (I): Photocatalytic activity and pH influence}, volume={33}, ISSN={["0043-1354"]}, DOI={10.1016/S0043-1354(98)00261-9}, abstractNote={Photocatalytic oxidations of methanol, ethanol and chloroform, trichloroethylene (TCE), and dichloropropionic acid (DCP) in M/TiO2 aqueous slurries are studied. In the presence of oxygen, the intermediates of methanol oxidation, such as formaldehyde and formic acid, were not detected by GC in the slurries of TiO2, Pt/TiO2, or Pd/TiO2, and CO2 was the only product detected. The distribution of intermediates for ethanol photocatalytic oxidation varies with different catalysts: under the same reaction conditions, the ratio of acetaldehyde:acetic acid is 30:1 on TiO2, and 0.23:1 on Pt/TiO2, with the acetaldehyde concentration being 130 times higher on TiO2 than on Pt/TiO2. Thus, a further oxidation is achieved easily on the Pt/TiO2. The CO2 production depends on the initial reaction pH: Acidic pH produces CO2 immediately in alcohol oxidation, but alkaline pH retards the mineralization substantially. Little effect of Pd metallization on TiO2 was observed for photocatalytic oxidation of chloroform, TCE or DCP. Pt/TiO2 only enhances DCP dechlorination and has no effect on its decarboxylation.}, number={3}, journal={WATER RESEARCH}, author={Chen, J and Ollis, DF and Rulkens, WH and Bruning, H}, year={1999}, month={Feb}, pages={661–668} }
 @article{chen_ollis_rulkens_bruning_1999, title={Photocatalyzed oxidation of alcohols and organochlorides in the presence of native TiO2 and metallized TiO2 suspensions. Part (II): Photocatalytic mechanisms}, volume={33}, ISSN={["0043-1354"]}, DOI={10.1016/S0043-1354(98)00262-0}, abstractNote={A detailed description of various mechanisms for the photocatalytic oxidation of alcohols and organochlorides in an aerated or a deaerated system is given. This description includes mechanisms of surface reactions and radical reactions based on our experimental data presented. A surface mechanism of direct oxidation of substrates in photocatalyst surfaces is proposed as a favorable pathway for photocatalytic oxidations of methanol and ethanol, also a possible pathway for chloroform, trichloroethylene (TCE) and dichloropropionic acid (DCP) in M/TiO2 aqueous slurries.}, number={3}, journal={WATER RESEARCH}, author={Chen, J and Ollis, DF and Rulkens, WH and Bruning, H}, year={1999}, month={Feb}, pages={669–676} }
 @article{d'hennezel_pichat_ollis_1998, title={Benzene and toluene gas-phase photocatalytic degradation over H(2)O and HCL pretreated TiO(2): by-products and mechanisms}, volume={118}, ISSN={["1010-6030"]}, DOI={10.1016/S1010-6030(98)00366-9}, abstractNote={Photocatalytic oxidations of toluene and benzene in air were carried out over water (TiO2/H2O) and HCl (TiO2/HCl) pretreated TiO2 as this latter pretreatment enhances the toluene removal rate. The main purpose was to identify intermediate products. No gas-phase by-products were detected by direct GC/FID analysis under our conditions despite the high aromatic concentration (50 mg m−3) and the short contact time (ms); this result illustrates an attractive capability of this air purification method. Adsorbed intermediate products recovered by extraction from the used photocatalysts were the same over TiO2/H2O and TiO2/HCl; i.e. no chlorinated products were found in this latter case. Benzoic acid, benzaldehyde, and benzyl alcohol were three major toluene intermediate products identified; trace derivatives of these products and of toluene that were monohydroxylated on the ring were also detected in catalyst extract samples. The benzene major by-product was phenol which was accompanied by hydroquinone and 1,4-benzoquinone. Acetic and formic acids were also formed from both benzene and toluene. For both aromatics, a water extraction of the used photocatalysts permitted separation of a yellow viscous material that settled between water and TiO2 after centrifugation. We have not identified the products contained in this material but believe them to be polymeric products which may be at the origin of the decreased photocatalytic activity of used TiO2 with respect to fresh TiO2. Finally, we discuss the photocatalytic oxidation pathways.}, number={3}, journal={JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY}, author={d'Hennezel, O and Pichat, P and Ollis, DF}, year={1998}, month={Nov}, pages={197–204} }
 @article{flickinger_mullick_ollis_1998, title={Method for construction of a simple laboratory-scale nonwoven filament biocatalytic filter}, volume={14}, ISSN={["8756-7938"]}, DOI={10.1021/bp980049x}, abstractNote={Abstract}, number={4}, journal={BIOTECHNOLOGY PROGRESS}, author={Flickinger, MC and Mullick, A and Ollis, DF}, year={1998}, pages={664–666} }
 @article{luyendyk_brown_ollis_1998, title={Writing across first-year engineering}, volume={9}, number={1998}, journal={Innovator: the SUCCEED Newsletter}, author={Luyendyk, S. and Brown, A. and Ollis, D.}, year={1998}, pages={1} }
 @misc{peral_domenech_ollis_1997, title={Heterogeneous photocatalysis for purification, decontamination and deodorization of air}, volume={70}, ISSN={["0268-2575"]}, DOI={10.1002/(SICI)1097-4660(199710)70:2<117::AID-JCTB746>3.0.CO;2-F}, abstractNote={A research review of gas–solid heterogeneous photocatalysis is presented, ranging from details of pioneering works, which dealt with basic phenomena like oxygen and water vapor adsorption, to recent applications to pollutant removal in contaminated atmospheres. Special interest is taken in describing the different reactor configurations studied so far in this emerging and promising field. © 1997 SCI}, number={2}, journal={JOURNAL OF CHEMICAL TECHNOLOGY AND BIOTECHNOLOGY}, author={Peral, J and Domenech, X and Ollis, DF}, year={1997}, month={Oct}, pages={117–140} }
 @article{velkovska_marten_ollis_1997, title={Kinetic model for batch cellulase production by Trichoderma reesei RUT C30}, volume={54}, ISSN={["0168-1656"]}, DOI={10.1016/S0168-1656(97)01669-6}, abstractNote={A kinetic model for batch cellulase enzyme production by T. reesei from cellulose substrate is constructed from literature concepts and laboratory data. The key concepts included were four: (i) existence of primary and secondary mycelia; (ii) cellulase production by secondary mycelia only; (iii) the adsorption of cellulase (catalyst) on the particulate cellulose (substrate), and (iv) the decline of cellulose reactivity with extent of conversion. The laboratory batch data were biomass (particulate), substrate (particulate cellulose), and product (cellulase enzyme and reducing sugar) concentration vs. time. The kinetic parameters were evaluated simultaneously through a nonlinear fitting routine, and the resultant model is shown to fit the data well. The model's success validates the presumed need to include all four concepts in reactor analysis for cellulase production.}, number={2}, journal={JOURNAL OF BIOTECHNOLOGY}, author={Velkovska, S and Marten, MR and Ollis, DF}, year={1997}, month={Apr}, pages={83–94} }
 @article{passos_fleming_felder_ollis_1997, title={Modeling growth of Saccharomyces rosei in cucumber fermentation}, volume={14}, ISSN={["1095-9998"]}, DOI={10.1006/fmic.1997.0118}, abstractNote={Abstract Objectives of this study were to assess the effects of key variables involved in cucumber fermentation on growth of the yeast, Saccharomyces rosei , and to develop a mathematical description of those effects. The growth medium for the studies was cucumber juice. Effects of concentrations of lactic, acetic, and hydrochloric acids and sodium chloride on growth at 30°C were determined in batch culture. Effect of substrate concentration on the specific growth rate was also defined. The specific growth rate decreased from 0.355 h −1 at pH 6.0 to 0.189 h −1 at pH 3.2. The undissociated form of lactic acid was more inhibitory than that of acetic acid. A predictive equation for specific growth rate was developed for predicting growth of S. rosei in batch culture. The molar yield of ethanol was 1.75 (±0.07) mM ethanol per mM hexose. Malate was not utilized, and glycerol was produced. The apparent biomass yield under anaerobic condition was 12.2 (±1.3) g cells/mol hexose. Aerobically, the biomass yield was 30.7 g cells/mol hexose. Similar specific growth rates were observed anaerobically (0.358 h −1 ) and aerobically (0.352 h −1 ). The predictive model for growth of S. rosei in cucumber juice should prove useful in modeling the mixed culture (yeast and lactic acid bacteria) fermentation of brined, whole cucumbers.}, number={6}, journal={FOOD MICROBIOLOGY}, author={Passos, FV and Fleming, HP and Felder, RM and Ollis, DF}, year={1997}, month={Dec}, pages={533–542} }
 @article{upadhya_ollis_1997, title={Simple photocatalysis model for photoefficiency enhancement via controlled, periodic illumination}, volume={101}, ISSN={["1520-6106"]}, DOI={10.1021/jp962649p}, abstractNote={Under steady illumination, aqueous phase photocatalytic oxidation reactions using titanium dioxide characteristically exhibit low quantum yields, i.e., the incident light is used inefficiently in the process. Sczechowski, Koval, and Noble1 reported substantially higher photoefficiencies (defined as reaction rate divided by incident photon rate) for TiO2 while using controlled, periodic illumination instead of continuous illumination in a flow system. We propose a transient kinetic model which suggests that rapid consumption of preadsorbed reactant inventory by photoproduced holes (or by their oxidation product, OH radical, etc.) accounts for such high photoefficiencies with periodic illumination and that the characteristically slow adsorption of additional oxygen and/or electron transfer to oxygen is responsible for low quantum yields observed under steady illumination. A model simulation provides trends of photoefficiency with variation of the length of light and dark periods which resemble the observed ...}, number={14}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, author={Upadhya, S and Ollis, DF}, year={1997}, month={Apr}, pages={2625–2631} }
 @article{peral_ollis_1997, title={TiO2 photocatalyst deactivation by gas-phase oxidation of heteroatom organics}, volume={115}, ISSN={["1381-1169"]}, DOI={10.1016/S1381-1169(96)00330-5}, abstractNote={TiO2 deactivation is studied during the gas-phase photocatalytic oxidation of organics containing three different heteroatoms: Si, N and S. Auger electron spectroscopy is used to characterize the catalyst poisoning species. A kinetic equation is presented which account for the activity vs. time observed data. Finally, an estimation is made of the equivalent monolayers of reactant converted prior total activity disappearance.}, number={2}, journal={JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL}, author={Peral, J and Ollis, DF}, year={1997}, month={Jan}, pages={347–354} }
 @article{dhennezel_ollis_1997, title={Trichloroethylene-promoted photocatalytic oxidation of air contaminants}, volume={167}, ISSN={["0021-9517"]}, DOI={10.1006/jcat.1997.1552}, abstractNote={The prospects for photocatalytic purification and treatment of air depend centrally on finding conditions for which the apparent photoefficiency for contaminant disappearance is near or above 100%. We recently demonstrated that destruction of a low photoefficiency contaminant, toluene, by addition of a high photoefficiency compound, trichloroethylene, could raise the toluene photoefficiency to provide 100% conversion in a single pass, fixed bed illuminated catalyst, using a residence time of about 5–6 ms. The present paper establishes the generality of this TCE enhancement of contaminant rate and photoefficiency by examining the photocatalytic oxidation of various common contaminants at 50 mg/m3in air, including alcohols, aldehydes, ketones, aromatics, and chloroalkanes using near-UV-illuminated titanium dioxide powder in a flow reactor, in the absence and presence of trichloroethylene (TCE). Compounds exhibiting TCE rate promotion were toluene, ethylbenzene,m-xylene, methyl ethyl ketone (MEK), acetaldehyde, butyraldehyde, methyltert-butyl ether (MTBE), methyl acrylate, 1,4-dioxane, and hexane. Rate inhibition by TCE was exhibited for acetone, methylene chloride, chloroform, and 1,1,1-trichloroethane. TCE presence had almost no effect on the benzene and methanol rates. Butanol and vinyl acetate single component conversions were 100% under our standard low flow rate conditions; increasing the flow rate quenched TCE conversion in the presence of butanol, and therefore no TCE enhancement effect could be noted.}, number={1}, journal={JOURNAL OF CATALYSIS}, author={dHennezel, O and Ollis, DF}, year={1997}, month={Apr}, pages={118–126} }
 @article{kuhn_peretti_ollis_1993, title={ACID INHIBITION OF IMMOBILIZED CELLS - QUANTITATIVE COMPARISON OF MODEL AND EXPERIMENT}, volume={39}, ISSN={["0273-2289"]}, DOI={10.1007/bf02919006}, journal={APPLIED BIOCHEMISTRY AND BIOTECHNOLOGY}, author={KUHN, R and PERETTI, S and OLLIS, D}, year={1993}, pages={401–413} }
 @article{padukone_peretti_ollis_1992, title={ANALYSIS OF PRODUCTIVITY IN LYSIS-DEFICIENT LAMBDA EXPRESSION SYSTEMS}, volume={40}, ISSN={["1097-0290"]}, DOI={10.1002/bit.260400608}, abstractNote={Abstract}, number={6}, journal={BIOTECHNOLOGY AND BIOENGINEERING}, author={PADUKONE, N and PERETTI, SW and OLLIS, DF}, year={1992}, month={Sep}, pages={697–704} }
 @article{padukone_peretti_ollis_1992, title={Bacteriophage lambda expression systems for enhanced recombinant protein production}, volume={210}, journal={NATO ASI Series, Series E: Applied Sciences}, author={Padukone, N. and Peretti, S. W. and Ollis, D. F}, year={1992}, pages={367–372} }
 @article{padukone_peretti_ollis_1992, title={CHARACTERIZATION OF THE MUTANT LYTIC STATE IN LAMBDA EXPRESSION SYSTEMS}, volume={39}, ISSN={["0006-3592"]}, DOI={10.1002/bit.260390402}, abstractNote={Abstract}, number={4}, journal={BIOTECHNOLOGY AND BIOENGINEERING}, author={PADUKONE, N and PERETTI, SW and OLLIS, DF}, year={1992}, month={Feb}, pages={369–377} }
 @article{peral_ollis_1992, title={HETEROGENEOUS PHOTOCATALYTIC OXIDATION OF GAS-PHASE ORGANICS FOR AIR PURIFICATION - ACETONE, 1-BUTANOL, BUTYRALDEHYDE, FORMALDEHYDE, AND META-XYLENE OXIDATION}, volume={136}, ISSN={["0021-9517"]}, DOI={10.1016/0021-9517(92)90085-V}, abstractNote={Photocatalyzed degradations of trace levels of various oxygenates and an aromatic in air were carried out using near-UV-illuminated titanium dioxide (anatase) powder. The initial rates of degradation for acetone, 1-butanol, formaldehyde, and m-xylene were well described by Langmuir-Hinshelwood rate forms. No reaction intermediates were detected for acetone oxidation at conversions of 5–20%. Butyraldehyde was the main product of 1-butanol oxidation for conversions of 20–30%. The influence of 5% water (simulating partial humidification) in the feedstream varied strongly: water vapor inhibited acetone oxidation, but had no influence on the 1-butanol conversion rate. m-Xylene conversion was enhanced by trace water addition, but inhibited at higher water levels. Some catalyst deactivation was detected between 1-butanol runs; the activity could be easily recovered by illuminating the catalyst in fresh air. Formaldehyde was also successfully oxidized. These results, taken together with earlier literature citations for photocatalyzed total oxidation of methane, ethane, trichloroethylene (but see (27)), toluene, and a very recent report for oxidation of odor compounds, indicate a favorable technical potential for photocatalyzed treatment of air in order to degrade and remove all major classes of oxidizable air contaminants.}, number={2}, journal={JOURNAL OF CATALYSIS}, author={PERAL, J and OLLIS, DF}, year={1992}, month={Aug}, pages={554–565} }
 @article{kuhn_peretti_ollis_1991, title={MICROFLUORIMETRIC ANALYSIS OF SPATIAL AND TEMPORAL PATTERNS OF IMMOBILIZED CELL-GROWTH}, volume={38}, ISSN={["1097-0290"]}, DOI={10.1002/bit.260380404}, abstractNote={Abstract}, number={4}, journal={BIOTECHNOLOGY AND BIOENGINEERING}, author={KUHN, RH and PERETTI, SW and OLLIS, DF}, year={1991}, month={Aug}, pages={340–352} }
 @article{padukone_peretti_ollis_1990, title={LAMBDA VECTORS FOR STABLE CLONED GENE-EXPRESSION}, volume={6}, ISSN={["8756-7938"]}, DOI={10.1021/bp00004a008}, abstractNote={Abstract}, number={4}, journal={BIOTECHNOLOGY PROGRESS}, author={PADUKONE, N and PERETTI, SW and OLLIS, DF}, year={1990}, pages={277–282} }
 @article{turchi_ollis_1990, title={PHOTOCATALYTIC DEGRADATION OF ORGANIC-WATER CONTAMINANTS - MECHANISMS INVOLVING HYDROXYL RADICAL ATTACK}, volume={122}, ISSN={["0021-9517"]}, DOI={10.1016/0021-9517(90)90269-P}, abstractNote={Abstract Hydroxyl and other oxygen-containing radicals are known to be present during the degradation of organic water pollutants in illuminated TiO2 photocatalyst slurries. It is proposed that the hydroxyl radical, OH·, is the primary oxidant in the photocatalytic system. Four possible mechanisms are suggested, all based on OH· attack of the organic reactant. The cases of reaction on the surface, in the fluid, and via a Rideal mechanism are shown to yield expressions similar to Langmuir-Hinshelwood (LH) rate forms. Compared with traditional LH constants, the derived kinetic parameters represent fundamentally different reactions and properties. A rate parameter independent of organic reactant is predicted by the model and substantiated by experimental degradation data. On the basis of these model results, the kinetic parameters for the photocatalytic degradation may be estimated from data on the photocatalyst's physical properties, the knowledge of electron-hole recombination and trapping rates, and the values of second-order reaction rate constants for hydroxyl radicals.}, number={1}, journal={JOURNAL OF CATALYSIS}, author={TURCHI, CS and OLLIS, DF}, year={1990}, month={Mar}, pages={178–192} }
 @article{ollis_1985, title={CONTAMINANT DEGRADATION IN WATER}, volume={19}, ISSN={["0013-936X"]}, DOI={10.1021/es00136a002}, abstractNote={This paper describes the process by which heterogeneous photocatalysis is used for the study of the degradation of chloromethanes, bromomethanes, chloroethanes, chloroethylenes and bromoethylenes, chlorobenzene, and chloroacetic acids in dilute aqueous solutions. Rate equations are presented for each of the halocarbons. In addition, solar applications and the potential use for water purification are discussed. 32 references, 6 figures, 1 table.}, number={6}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={OLLIS, DF}, year={1985}, pages={480–484} }
 @article{marten_velkovska_khan_ollis, title={Rheological, mass transfer, and mixing characterization of cellulase-producing trichoderma reesei suspensions}, volume={12}, journal={Biotechnology Progress}, author={Marten, M.R. and Velkovska, S. and Khan, S.A. and Ollis, D.F.}, pages={602–611} }
 @article{marten_velkovska_khan_ollis, title={Steady and dynamic shear characterization of cellulase-producing trichoderma reesei suspensions}, volume={51}, number={2}, journal={Applied Biochemistry and Biotechnology}, author={Marten, M.R. and Velkovska, S. and Khan, S.A. and Ollis, D.F.}, pages={319–328} }