Wet Oxidation Pretreatment of Poplar Waste for Enhancing Enzymatic Hydrolysis Efficiency

In this paper, we described the optimization of the wet oxidation pretreatment conditions to enhance enzymatic hydrolysis efficiency, using poplar waste from the stock section of a paper mill as the raw material. We showed that the optimal conditions of the pretreatment for poplar waste were an initial p H value of 10, a temperature of 195℃, a holding time of 15 min, and an oxygen pressure of 1.2 MPa. In this case, the yield of the obtained solid material produced by the process was 51.7% and the reducing sugar yield was 46.8%. The solid part obtained from the pretreatment process was hydrolyzed by cellulase L-10. The optimal enzymatic conditions were a temperature of 49℃, a duration time of 56 h, an enzyme dosage of 38 FPU/g at a p H value of 4.8, and a solid-to-liquor ratio of 1∶50. The resulting cellulose conversion rate reached 96.4% in terms of the pretreated substances. In addition, a chemical composition analysis of the poplar waste and pretreated material indicated that about 92% of the hemicelluloses and 43% of the lignin in the raw material were degraded and dissolved. In addition, the crystallization decreased from 57.5% to 54.8%. An obvious fibrillation of the fiber pretreated by the wet oxidization process was observed by SEM. Moreover, high-performance liquid chromatography(HPLC) results showed a high xylose content and monosaccharide degradation products in the pretreatment solution. In conclusion, the wet oxidation pretreatment process could efficiently degrade or remove the lignin and hemicellulose, as well as reduce the crystallinity of the lignocellulosic material, which resulted in animprovement of the enzymatic ability and an increase in the cellulose conversion rate.

Preparation and Characteristics of a pH-sensitive Glucose-based Hydrogel

With glucose as the template compound,a p H-sensitive hydrogel was prepared by polymerization of the modified glucose,acrylamide,and acrylic acid.The porous hydrogel showed the highest swelling ratio of 42.7 g/g at p H=7.4 and the best adsorption of methylene blue at p H=7.The Langmuir isotherm fitted very well to the equilibrium adsorption data with the maximum adsorption capacity of 49.1 mg/g.The adsorption kinetics were well described by the pseudo 2^(nd) order model.Adsorption studies suggested that the p H-sensitive glucose-based hydrogel could be used as an adsorbent for the removal of methylene blue from wastewater.Other applications of the hydrogel are on the way,such as scaffolding in the biomedical field and soil conditioning in agriculture.