@article{park_yoo_lim_rojas_hubbe_park_2019, title={Impact of oxidative carbonization on structure development of loblolly pine-derived biochar investigated by nuclear magnetic resonance spectroscopy and X-ray photoelectron spectroscopy}, volume={96}, ISSN={["1879-0062"]}, DOI={10.1016/j.diamond.2019.05.001}, abstractNote={Biochar produced at an oxidative atmosphere shows distinct chemical properties compared to those of biochar produced at an inert atmosphere. However, there has been little investigation on the relationship between the oxidative atmosphere and the structure development of biochar, which can be useful information for the utilization of derived products. In this study, the effect of the oxygen atmosphere on the structure development of loblolly pine-derived biochar during thermal treatment was investigated. Quantitative analysis using solid-state direct polarization/magic angle spinning 13C nuclear magnetic resonance spectroscopy presented the existence of large fractions of aromatic and non-protonated carbons in the biochars treated at an oxidative atmosphere, implying highly condensed aromatic structures with large cluster sizes. Simultaneous thermogravimetic analyzer-differential scanning calorimetry was employed to demonstrate the difference in heat flow during the thermal treatment at two different atmospheres. Relatively large exothermic heat flow was observed when woody biomass was treated at 350 °C under an oxidative atmosphere which might be responsible for the difference in structural alteration. The series of observations suggested that compared to inert atmospheric conditions, admitting a limited amount of oxygen during thermal treatment of woody biomass could promote the evolution of condensed aromatic carbon structures.}, journal={DIAMOND AND RELATED MATERIALS}, author={Park, Junyeong and Yoo, Seunghyun and Lim, Kwang Hun and Rojas, Orlando J. and Hubbe, Martin A. and Park, Sunkyu}, year={2019}, month={Jun}, pages={140–147} }
 @article{koo_park_gonzalez_jameel_park_2019, title={Two-stage autohydrolysis and mechanical treatment to maximize sugar recovery from sweet sorghum bagasse}, volume={276}, ISSN={["1873-2976"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85059462040&partnerID=MN8TOARS}, DOI={10.1016/j.biortech.2018.12.112}, abstractNote={Modified autohydrolysis combined with mechanical refining has been suggested to recover free sugars from sweet sorghum bagasse and facilitates enzyme access to cellulose in bagasse for enhancing its conversion to fermentable sugars. The amount of total available sugars in sweet sorghum bagasse was found to be 76.1% and this value was used to evaluate the efficiency of the process suggested. Total sugar recovery was achieved up to 68.1% through the single-stage autohydrolysis at 170 °C for 60 min, followed by mechanical refining and enzymatic hydrolysis; however, the sugar recovery through partial degradation of free sugars induced by high-temperature autohydrolysis was lower than expected. A modified two-stage autohydrolysis was suggested to prevent sugar degradation and the total sugar recovery using this process reached 83.9% of total available sugars in sweet sorghum bagasse.}, journal={BIORESOURCE TECHNOLOGY}, author={Koo, Bonwook and Park, Junyeong and Gonzalez, Ronalds and Jameel, Hasan and Park, Sunkyu}, year={2019}, month={Mar}, pages={140–145} }
 @article{park_wang_lee_jameel_jin_park_2016, title={Effect of the Two-Stage Autohydrolysis of Hardwood on the Enzymatic Saccharification and Subsequent Fermentation with an Efficient Xylose-Utilizing Saccharomyces cerevisiae}, volume={11}, ISSN={["1930-2126"]}, DOI={10.15376/biores.11.4.9584-9595}, abstractNote={To effectively utilize sugars during the fermentation process, it is important to develop a process that can minimize the generation of inhibiting compounds such as furans and acids, and a robust micro-organism that can co-ferment both glucose and xylose into products. In this study, the feasibility of efficient ethanol production was investigated using a combination of two approaches: two-stage autohydrolysis of biomass and fermentation using an engineered Saccharomyces cerevisiae to produce ethanol. When the hardwood chips were autohydrolyzed at 140 °C, followed by the second treatment at 180 °C, a higher yield of sugar conversion and fewer inhibitory effects on subsequent fermentation were achieved compared with the results from single-stage autohydrolysis. A higher overall yield of ethanol resulted by using an engineered yeast strain, SR8. This observation suggests the possibility of the feasible combination of two-stage autohydrolysis and the recombinant yeast.}, number={4}, journal={BIORESOURCES}, author={Park, Junyeong and Wang, Ziyu and Lee, Won-Heong and Jameel, Hasan and Jin, Yong-Su and Park, Sunkyu}, year={2016}, month={Nov}, pages={9584–9595} }
 @article{park_shin_yoo_zoppe_park_2015, title={Delignification of Lignocellulosic Biomass and Its Effect on Subsequent Enzymatic Hydrolysis}, volume={10}, ISSN={["1930-2126"]}, DOI={10.15376/biores.10.2.2732-2743}, abstractNote={The effect of delignification on the enzymatic hydrolysis of biomass was investigated to determine how different delignification processes affect enzymatic hydrolysis conversion yields. Oxygen, hydrogen peroxide, and sodium chlorite treatments were performed, and the structural and chemical changes in the biomass were evaluated. Sodium chlorite delignification proved the most effective process to remove lignin in hardwood samples, followed by oxygen delignification. Hydrogen peroxide delignification was not as effective as the other two methods. As for the enzymatic conversion of carbohydrates after delignification processes on hardwood, oxygen and sodium chlorite treatments substantially improved conversion yields as the number of successive treatments was increased, compared to untreated hardwood samples. Changes in α-cellulose after delignification were less substantial than those of hardwood samples, and corresponding conversion yields were also lower. Delignification-induced structural changes in treated substrates might be responsible for the changes in carbohydrate conversion yield observed following subsequent enzymatic hydrolysis.}, number={2}, journal={BIORESOURCES}, author={Park, Junyeong and Shin, Heenae and Yoo, Seunghyun and Zoppe, Justin O. and Park, Sunkyu}, year={2015}, pages={2732–2743} }
 @article{park_hung_gan_rojas_lim_park_2013, title={Activated carbon from biochar: Influence of its physicochemical properties on the sorption characteristics of phenanthrene}, volume={149}, ISSN={["1873-2976"]}, DOI={10.1016/j.biortech.2013.09.085}, abstractNote={The relationship between physicochemical properties of biochar-based activated carbons and its adsorption was investigated using an aromatic model compound, phenanthrene. Solid-state 13C NMR analysis indicated more condensed aromatic structures when pyrolysis temperature increased or after activation process induced. The increasing aromaticity and non-protonated carbon fraction of the activated biochar treated at 300 °C amounted to 14.7% and 24.0%, respectively, compared to 7.4% and 4.4% for biochar treated at 700 °C. The surface area and pore volume were reduced with the increase in pyrolysis temperature, but increased after activation. Surface characteristics correlated with the initial sorption rate and equilibrium concentration of phenanthrene, but not with the aromaticity. Solid-state 2H NMR for phenanthrene-d10 saturated activated biochars, however, showed substantial difference in molecular mobility, which might be due to the high aromaticity of the activated biochars. Overall, these results provide an opportunity to manipulate the characteristics of biomass-based adsorbents based on the application needs.}, journal={BIORESOURCE TECHNOLOGY}, author={Park, Junyeong and Hung, Ivan and Gan, Zhehong and Rojas, Orlando J. and Lim, Kwang Hun and Park, Sunkyu}, year={2013}, month={Dec}, pages={383–389} }
 @article{jung_park_lim_park_heo_her_oh_yun_yoon_2013, title={Adsorption of selected endocrine disrupting compounds and pharmaceuticals on activated biochars}, volume={263}, ISSN={["1873-3336"]}, DOI={10.1016/j.jhazmat.2013.10.033}, abstractNote={Chemically activated biochar produced under oxygenated (O-biochar) and oxygen-free (N-biochar) conditions were characterized and the adsorption of endocrine disrupting compounds (EDCs): bisphenol A (BPA), atrazine (ATR), 17 α-ethinylestradiol (EE2), and pharmaceutical active compounds (PhACs); sulfamethoxazole (SMX), carbamazepine (CBM), diclofenac (DCF), ibuprofen (IBP) on both biochars and commercialized powdered activated carbon (PAC) were investigated. Characteristic analysis of adsorbents by solid-state nuclear magnetic resonance (NMR) was conducted to determine better understanding about the EDCs/PhACs adsorption. N-biochar consisted of higher polarity moieties with more alkyl (0-45 ppm), methoxyl (45-63 ppm), O-alkyl (63-108 ppm), and carboxyl carbon (165-187 ppm) content than other adsorbents, while aromaticity of O-biochar was higher than that of N-biochar. O-biochar was composed mostly of aromatic moieties, with low H/C and O/C ratios compared to the highly polarized N-biochar that contained diverse polar functional groups. The higher surface area and pore volume of N-biochar resulted in higher adsorption capacity toward EDCs/PhACs along with atomic-level molecular structural property than O-biochar and PAC. N-biochar had a highest adsorption capacity of all chemicals, suggesting that N-biochar derived from loblolly pine chip is a promising sorbent for agricultural and environmental applications. The adsorption of pH-sensitive dissociable SMX, DCF, IBP, and BPA varied and the order of adsorption capacity was correlated with the hydrophobicity (Kow) of adsorbates throughout the all adsorbents, whereas adsorption of non-ionizable CBM, ATR, and EE2 in varied pH allowed adsorbents to interact with hydrophobic property of adsorbates steadily throughout the study.}, journal={JOURNAL OF HAZARDOUS MATERIALS}, author={Jung, Chanil and Park, Junyeong and Lim, Kwang Hun and Park, Sunkyu and Heo, Jiyong and Her, Namguk and Oh, Jeill and Yun, Soyoung and Yoon, Yeomin}, year={2013}, month={Dec}, pages={702–710} }
 @article{park_meng_lim_rojas_park_2013, title={Transformation of lignocellulosic biomass during torrefaction}, volume={100}, ISSN={["0165-2370"]}, DOI={10.1016/j.jaap.2012.12.024}, abstractNote={In this study, the effect of torrefaction on the chemical and structural transformation of lignocellulosic biomass was investigated using complementary analytical tools. It was observed that the acid-insoluble fraction was increased from approximately 30 to 38% and the methoxyl content was decreased to about half after torrefaction at 330 °C for 2.5 min. These results highlight the formation of condensed structures along with lignin transformation via demethoxylation. Solid-state NMR spectroscopy indicated that upon torrefaction the aromaticity increased from about 36 to 60%. For the sample torrefied at 330 °C, the non-protonated aromatic carbon fraction was found to be about 60% of total aromatic carbons, indicating the formation of large aromatic clusters. The complementary analyses used in this study are proposed as a suitable approach for the elucidation of chemical and structural transformation of biomass during thermal treatment.}, journal={JOURNAL OF ANALYTICAL AND APPLIED PYROLYSIS}, author={Park, Junyeong and Meng, Jiajia and Lim, Kwang Hun and Rojas, Orlando J. and Park, Sunkyu}, year={2013}, month={Mar}, pages={199–206} }
 @article{meng_park_tilotta_park_2012, title={The effect of torrefaction on the chemistry of fast-pyrolysis bio-oil}, volume={111}, ISSN={["0960-8524"]}, DOI={10.1016/j.biortech.2012.01.159}, abstractNote={Fast pyrolysis was performed on torrefied loblolly pine and the collected bio-oils were analyzed to compare the effect of the torrefaction treatment on their quality. The results of the analyses show that bio-oils produced from torrefied wood have improved oxygen-to-carbon ratios compared to those from the original wood with the penalty of a decrease in bio-oil yield. The extent of this improvement depends on the torrefaction severity. Based on the GC/MS analysis of the pyrolysis bio-oils, bio-oils produced from torrefied biomass show different compositions compared to that from the original wood. Specifically, the former becomes more concentrated in pyrolytic lignin with less water content than the latter. It was considered that torrefaction could be a potential upgrading method to improve the quality of bio-oil, which might be a useful feedstock for phenolic-based chemicals.}, journal={BIORESOURCE TECHNOLOGY}, author={Meng, Jiajia and Park, Junyeong and Tilotta, David and Park, Sunkyu}, year={2012}, month={May}, pages={439–446} }
 @article{barnette_bradley_veres_schreiner_park_park_park_kim_2011, title={Selective Detection of Crystalline Cellulose in Plant Cell Walls with Sum-Frequency-Generation (SFG) Vibration Spectroscopy}, volume={12}, ISSN={["1525-7797"]}, DOI={10.1021/bm200518n}, abstractNote={The selective detection of crystalline cellulose in biomass was demonstrated with sum-frequency-generation (SFG) vibration spectroscopy. SFG is a second-order nonlinear optical response from a system where the optical centrosymmetry is broken. In secondary plant cell walls that contain mostly cellulose, hemicellulose, and lignin with varying concentrations, only certain vibration modes in the crystalline cellulose structure can meet the noninversion symmetry requirements. Thus, SFG can be used to detect and analyze crystalline cellulose selectively in lignocellulosic biomass without extraction of noncellulosic species from biomass or deconvolution of amorphous spectra. The selective detection of crystalline cellulose in lignocellulosic biomass is not readily achievable with other techniques such as XRD, solid-state NMR, IR, and Raman analyses. Therefore, the SFG analysis presents a unique opportunity to reveal the cellulose crystalline structure in lignocellulosic biomass.}, number={7}, journal={BIOMACROMOLECULES}, author={Barnette, Anna L. and Bradley, Laura C. and Veres, Brandon D. and Schreiner, Edward P. and Park, Yong Bum and Park, Junyeong and Park, Sunkyu and Kim, Seong H.}, year={2011}, month={Jul}, pages={2434–2439} }
 @misc{hubbe_park_park, title={Cellulosic substrates for removal of pollutants from aqueous systems: A review. Part 4. dissolved petrochemical compounds}, volume={9}, number={4}, journal={BioResources}, author={Hubbe, M. A. and Park, J. and Park, S.}, pages={7782–7925} }