Super Absorbent Materials from Lignocellulosic Materials by Phosphorylation. (Part 3). Chlorite Treatment and Phosphorylation of Woodmeal for Water Absorbency.

Abstract

The effects of delignification with acidified sodium chlorite and phosphorylation with phosphoric acidurea on swelling behavior of woodmeal were investigated. Chlorite treatment of todomatsu was quite selective in removing lignin, and this treatment caused no significant change in carbohydrate content. Chlorite treatment of woodmeal followed by phosphorylation rapidly increased its water absorbency with increasing degree of delignification up to 30%. After phosphorylation, the woodmeal with 65% of degree of delignification had maximum water absorbency (141g H2O/g absorbent). The removal of lignin was a dominant factor for the hydrogelation of phosphorylated products. The water absorbencies increased with increasing content of phosphate groups in the products, and reached a maximum at the phosphorus content of 6.6% (0.43 ester group/glucose anhydride unit). These results indicated that the water absorbency of phosphorylated products depended on the degree of substitution of phosphate groups. Sufficient hydrogelation required the phosphorylation with 60g of urea and 1.5g of phosphoric acid on 2g of chlorite-treated woodmeal at 150°C for 60min.