Approaching zero cellulose loss in cellulose nanocrystal (CNC) production: recovery and characterization of cellulosic solid residues (CSR) and CNC
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This study demonstrated the potential of simultaneously recovering cellulosic solid residues (CSR) and producing cellulose nanocrystals (CNCs) by strong sulfuric acid hydrolysis to minimize cellulose loss to near zero. A set of slightly milder acid hydrolysis conditions than that considered as “optimal” were used to significantly minimize the degradation of cellulose into soluble sugars that cannot be economically recovered, but resulted in CSR that is easily recoverable through conventional centrifuge. It was found that the window for simultaneous recoveries of CSR and producing high yield CNC in strong acid hydrolysis was extremely narrow. However, we achieved significant CSR yield with near zero cellulose loss but without sacrificing CNC yield compared with that obtained at “optimal condition”. The resultant CSR contains sulfate ester groups that facilitated subsequent mechanical nano-fibrillation to cellulose nanofibrils (CNFs), a potential high value nanocellulosic material for a variety of applications.
KeywordsNanocellulose materials/composites Cellulose nanocrystals (CNCs) Cellulose nanofibrils (CNFs) Cellulose nanowhiskers (CNWs) Acid hydrolysis
Financial support for this work included USDA Agriculture and Food Research Initiative (AFRI) Competitive Grant (No. 2011-67009-20056) and Chinese Scholarship Council (CSC). The funding from these two programs made the visiting appointment of Wang at the USDA Forest Products Laboratory (FPL) possible. We would like to acknowledge Fred Matt and Kolby Hirth (Both FPL) for conducting carbohydrate and sulfur content measurements, respectively, Thomas Kuster (FPL) for SEM image analysis, Debby Sherman of DSimaging and Life Science Microscopy Facility at Purdue University for TEM analysis of the mechanically fibrillated CSR samples. We also would like to thank Anne Kamata, SAIC-Frederick, Inc. for electron microscopy imaging. The TEM imaging work has been funded in whole or in part with federal funds from the National Cancer Institute, National Institutes of Health, under Contract No. HHSN261200800001E. The content of this publication does not necessarily reflect the views or policies of the Department of Health and Human Services, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government.
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