Integrated Hemicellulose Extraction and Papermaking Fiber Production from Agro-Waste Biomass

Abstract

The present study deals with the valorization of corn stalks in an integrated processing strategy targeting two products: extracted hemicelluloses (HC) and papermaking fibers. Preliminary trials were conducted to assess the individual or the combined effects of biomass treatment on the quality of the obtained hemicelluloses and papermaking fibers. Depending on the hot alkaline extraction (HAE) conditions, the extracted HC had a xylan content between 44–63%. The xylan removal yield ranged between 19–35%. The recovery of HC from the extraction liquor and final black liquor was significantly affected by process conditions. The experimental approach continued with the study of HAE conditions on the obtained paper’s mechanical properties. The optimization approach considered conserving paper strength properties while achieving an equilibrium with the highest possible HC extraction yield. The optimal values are sodium hydroxide concentration (1%), process time (33 min), and temperature (100 °C). The xylan content in the separated HC sample was ~55%. An extended extraction of HC from the resulting pulp under hot alkaline conditions with 5% NaOH was performed to prove the HC influence on paper strength. The xylan content in HC samples was 65%. The consequence of xylan content reduction in pulp leads to 30–50% mechanical strength loss.

The Potential Valorization of Corn Stalks by Alkaline Sequential Fractionation to Obtain Papermaking Fibers, Hemicelluloses, and Lignin—A Comprehensive Mass Balance Approach

“…The main components of initial CSs are cellulose, hemicellulose, and lignin, and the obtained values were comparable with other literature data [ 62 , 63 ]. As compared to our previous work [ 37 ], the cellulose content showed lower values for cellulose and xylan contents but higher for lignin. Several elements leading to the differences in chemical composition might be corn variety, precipitation/irrigation level, fertilization, and harvesting period [ 64 , 65 , 66 ].…”

“…The concentration of the total polysaccharides, mainly consisting of oligomers of anhydro-xylose units, which did not precipitate in ethanol, increased with the increase in the severity of the treatment, probably as a result of the degradation extent. In fact, the increase in the severity of the treatment also negatively affects the HC recovery yields, as previously noted [ 37 ]. Analysis results for the chemical composition of the recovered lignin samples can be seen in Figure 3 .…”

“…Before papermaking on a Rapid Koethen laboratory sheet former ISO 5269/2 [ 38 ], the pulps were all refined at a constant number of revolutions (1500) in a Jokro mill, ISO 5264-3:1979 [ 39 ]. The beating resulted in pulps of 45–48 °SR drainage resistance, a value at which the mechanical strength properties are fully developed [ 37 ]. The obtained paper sheets were the subject of testing—in this respect, tensile strength and burst strength were determined according to ISO 1924-2:2008 [ 40 ] and ISO 2758:2014 [ 37 , 41 ].…”

“…The beating resulted in pulps of 45–48 °SR drainage resistance, a value at which the mechanical strength properties are fully developed [ 37 ]. The obtained paper sheets were the subject of testing—in this respect, tensile strength and burst strength were determined according to ISO 1924-2:2008 [ 40 ] and ISO 2758:2014 [ 37 , 41 ]. The values of SCTI and CMTI were obtained after performing SCT [ 42 ] and CMT [ 43 ] tests and reporting the obtained values (kN/m and daN) for the basis weights of the tested paper.…”

“…Apart from previous work that focused on finding the optimum equilibrium between the amount of extracted HCs and paper quality, this study took into consideration the analysis of both solid as well as liquid streams [ 37 ]. The obtained products were characterized from a common perspective (chemical composition) as well as from the perspective of their usage potential (papermaking properties, degree of polymerization, and antioxidant activity).…”