@article{jardim_hart_lucia_jameel_chang_2022, title={The Effect of the Kraft Pulping Process, Wood Species, and pH on Lignin Recovery from Black Liquor}, volume={10}, ISSN={["2079-6439"]}, url={https://www.mdpi.com/2079-6439/10/2/16}, DOI={10.3390/fib10020016}, abstractNote={Lignin has shown a great potential to produce fuels, value-added chemicals, and functional materials due to its high-energy density and intrinsic aromatic-based structure. Yet, the lignin precipitation of different biomasses needs investigation because most of the work has been performed on softwood and much less is known about hardwoods. In fact, the lignin from these two wooden biomasses vary in composition and pulping performance, which can reflect on lignin precipitation. Therefore, the present study investigated the precipitation and composition of 40 distinct kraft lignins obtained from pine, acacia, sweetgum, and eucalyptus black liquors. Two lignin fractions were precipitated at different pHs, according to known industrial lignin separation practices (pH = 9.5 and 2.5) from black liquors taken at different levels of pulping. Overall, lignin recovery increased with increasing lignin concentration in the black liquor, i.e., higher amounts of lignin were obtained at higher levels of delignification. In addition, pine lignins showed superior yields than the hardwoods and were around five times purer. Among the hardwoods, lignin recovery increased with the S–G ratio of the native lignin, and eucalyptus showed the best performance by achieving the highest yields and purities. Finally, the present work compared the lignin recovery yield and the purity of softwood and different hardwood lignins in a systematic way, which will increase awareness of this underutilized green material and could potentially increase the interest in establishing new lignin plants across the globe.}, number={2}, journal={FIBERS}, author={Jardim, Juliana M. and Hart, Peter W. and Lucia, Lucian A. and Jameel, Hasan and Chang, Hou-min}, year={2022}, month={Feb} }
 @article{jardim_hart_lucia_jameel_2021, title={Probing the molecular weights of sweetgum and pine kraft lignin fractions}, volume={20}, ISSN={["0734-1415"]}, DOI={10.32964/TJ20.6.381}, abstractNote={The present investigation undertook a systematic investigation of the molecular weight (MW) of kraft lignins throughout the pulping process to establish a correlation between MW and lignin recovery at different extents of the kraft pulping process. The evaluation of MW is crucial for lignin characterization and utilization, since it is known to influence the kinetics of lignin reactivity and its resultant physicochemical properties. 
Sweetgum and pine lignins precipitated from black liquor at different pHs (9.5 and 2.5) and different extents of kraft pulping (30–150 min) were the subject of this effort. Gel permeation chromatography (GPC) was used to deter-
mine the number average molecular weight (Mn), mass average molecular weight (Mw), and polydispersity of the lignin samples. It was shown that the MW of lignins from both feedstocks follow gel degradation theory; that is, at the onset of the kraft pulping process low molecular weightlignins were obtained, and as pulping progressed, the molecular weight peaked and subsequently decreased. An important finding was that acetobromination was shown to be a more effective derivatization technique for carbohydrates containing lignins than acetylation, the technique typically used for derivatization of lignin.}, number={6}, journal={TAPPI JOURNAL}, author={Jardim, Juliana M. and Hart, Peter W. and Lucia, Lucian and Jameel, Hasan}, year={2021}, month={Jun}, pages={381–391} }
 @article{jardim_hart_lucia_jameel_chang_2020, title={A Quantitative Comparison of the Precipitation Behavior of Lignin from Sweetgum and Pine Kraft Black Liquors}, volume={15}, ISSN={["1930-2126"]}, DOI={10.15376/biores.15.3.5464-5480}, abstractNote={Lignin is a by-product of the pulp and paper industry that can be precipitated by acidification from black liquor as a potential feedstock for valuable green materials. Precipitation and quantification of lignin from softwood black liquors have been documented and commercialized with well-established methods; however, applying those methods to the precipitation of lignin from hardwood black liquors has produced low lignin yields. A need to understand the main differences between hardwood and softwood lignin precipitation prompted the current investigation. Multiple black liquor samples from sweetgum and pine pulping were obtained at different times of standard kraft cooks. Two lignin fractions were precipitated from each of these black liquors, one at pH 9.5 and one at pH 2.5. Detailed lignin and carbohydrate material balances were performed around each of the sample sets, starting with the wood and ending with precipitated lignin fractions. For all conditions tested, the amount and purity of pine lignin precipitated were superior to sweetgum lignin. The maximum recovery for sweetgum lignin was 69.7%, while for pine lignin, it was 90.9%.}, number={3}, journal={BIORESOURCES}, author={Jardim, Juliana M. and Hart, Peter W. and Lucia, Lucian and Jameel, Hasan and Chang, Houmin}, year={2020}, month={Aug}, pages={5464–5480} }
 @misc{jardim_hart_lucia_jameel_2020, title={Insights into the Potential of Hardwood Kraft Lignin to Be a Green Platform Material for Emergence of the Biorefinery}, volume={12}, ISSN={["2073-4360"]}, DOI={10.3390/polym12081795}, abstractNote={Lignin is an abundant, renewable, and relatively cheap biobased feedstock that has potential in energy, chemicals, and materials. Kraft lignin, more specifically, has been used for more than 100 years as a self-sustaining energy feedstock for industry after which it has finally reached more widespread commercial appeal. Unfortunately, hardwood kraft lignin (HWKL) has been neglected over these years when compared to softwood kraft lignin (SWKL). Therefore, the present work summarizes and critically reviews the research and development (R&D) dealing specifically with HWKL. It will also cover methods for HWKL extraction from black liquor, as well as its structure, properties, fractionation, and modification. Finally, it will reveal several interesting opportunities for HWKL that include dispersants, adsorbents, antioxidants, aromatic compounds (chemicals), and additives in briquettes, pellets, hydrogels, carbon fibers and polymer blends and composites. HWKL shows great potential for all these applications, however more R&D is needed to make its utilization economically feasible and reach the levels in the commercial lignin market commensurate with SWKL. The motivation for this critical review is to galvanize further studies, especially increased understandings in the field of HWKL, and hence amplify much greater utilization.}, number={8}, journal={POLYMERS}, author={Jardim, Juliana M. and Hart, Peter W. and Lucia, Lucian and Jameel, Hasan}, year={2020}, month={Aug} }
 @article{naithani_lucia_jameel_hart_2020, title={Soybean peroxidase treatment of ultra-high kappa softwood pulp to enhance yield and physical properties}, volume={19}, ISSN={["0734-1415"]}, DOI={10.32964/TJ19.9.437}, abstractNote={The working hypothesis serving as basis for this study is that pulping to a higher kappa number will produce a higher yield pulp, and then treating that pulp with a surface reactive lignin peroxidase to ablate surface lignin will increase specific bonding area. In the present case, the working hypothesis was modified so that soybean peroxidase (SBP) works like lignin peroxidase to modify surface lignin on high-kappa, high-yield softwood pulps to facilitate enhanced fiber-to-fiber bonding such that the resulting paper strength is similar to the lower kappa soft-wood pulp generally used to make linerboard. 
Soybean peroxidase is actually a plant peroxidase that exhibits lignin peroxidase-like activity. It is not a lignin peroxidase derived from white rot fungus. The current work did show a significant improvement in pulp yield (62.2% vs. 55.2% yield for a 103-kappa control linerboard grade sheet), while treatment with SBP showed that tensile, burst, and STFI properties of the pulp were improved, although more convincing data needs to be obtained.}, number={9}, journal={TAPPI JOURNAL}, author={Naithani, Ved and Lucia, Lucian and Jameel, Hasan and Hart, Peter W.}, year={2020}, month={Sep}, pages={437–443} }
 @article{jardim_du_hart_lucia_jameel_chang_gracz_2019, title={Fundamental molecular characterization and comparison of the 0, D-0, and E stage effluents from hardwood pulp bleaching}, volume={18}, ISSN={["0734-1415"]}, DOI={10.32964/TJ18.6.341}, abstractNote={The present study characterized effluents from the O, D0, and E stages using nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC) techniques to better understand the chemical nature of the dissolved organics formed from the bleaching of a high-yield hardwood kraft pulp. Understanding the structures and molecular weight distribution of these organics is the first step in developing methods to mitigate these contaminates in the discharged effluents. The results indicated that the molecular weight distribution (MWD) of the dissolved organics from oxygen delignification effluent is broader than those from D0 and E stage effluents. In addition, the O stage filtrate contained considerable amounts of lignin and xylan fragments, which showed its efficiency in removing such materials. The effluent from the D0 stage contained a lower amount of high molecular weight fragments and a higher amount of low molecular weight fragments versus the O-stage filtrate. Aromatic structures were nearly absent in the D0 stage filtrate, but the degraded organic material, presumably from oxidized lignin, contained olefinic (C=C) and carbonyl (C=O) functional groups. Furthermore, higher molecular weight fragments were detected in the E-stage effluent, presumably due to the extensive solubilization and removal of the oxidized lignin generated from the D0 pulp.}, number={6}, journal={TAPPI JOURNAL}, author={Jardim, Juliana M. and Du, Xueyu and Hart, Peter W. and Lucia, Lucian and Jameel, Hasan and Chang, Hou-Min and Gracz, Hanna}, year={2019}, month={Jun}, pages={341–351} }