FORMIC ACID/ACETIC ACID/WATER PULPING OF AGRICULTURAL WASTES

摘要

In this paper, mustard branches, mustard stems and lentil stalks were characterized in order to evaluate them as pulping raw materials. These agricultural wastes are characterized by relatively moderate amounts of lignin (20-23%), reasonably low amounts of α-cellulose (35-37%) and relatively high amounts of ash content (4-7%). In this study, pulping of lentil stalks, mustard stems and mustard branches was carried out at atmospheric pressure using a mixture of formic acid, acetic acid, and water (FA/AA/H2O). Increasing formic acid concentration in the acid mixture improved the delignification rate. A higher pulp yield was obtained from lentil stalks with higher residual lignin than those of mustard stems and branches after FA/AA/H2O treatment. It was found that the delignification of FA/AA/H2O treated pulp was improved in an efficient and selective manner by using peroxyacid, which facilitated chlorine free bleaching. After prebleaching with peroxyacid, pulp from mustard branches showed the lowest kappa number among the three raw materials. Prebleached pulps were bleached by alkaline peroxide bleaching and final pulp yields reached 47.2%, 45.3% and 41.3% for lentil stalks, mustard stems and mustard branches, respectively. The bleached pulp from mustard stems and branches showed ISO brightness above 80% after alkaline peroxide bleaching, while lentil stalks bleached pulp showed 76% ISO brightness. Acceptable papermaking properties were obtained from these agricultural wastes by organic acid pulping at atmospheric pressure, followed by chlorine free bleaching.