Degumming Pretreatment with Sodium Hydroxide and Sodium Oxalate in the Process of Whole Cotton Stalk APMP Pulping

The effect of degumming pretreatment on whole cotton stalk alkaline peroxide mechanical pulp (APMP) was researched. Degumming pretreatment was used as the first stage of an APMP pulping process, replacing conventional hot water pretreatment. Two degumming agents of sodium hydroxide (NaOH) and sodium oxalate (Na2C2O4) were researched separately. The efficiency of hot water pretreatment, NaOH pretreatment, and Na2C2O4 pretreatment on pectin and metal ions removal was compared. After pretreatment of hot water, NaOH, and Na2C2O4, pectin content was reduced to 4.0%, 2.1%, 1.6%, respectively, compared to original material (4.3%), at removal rates of 7%, 51%, and 64%, respectively. For metal ions, especially transition metal ions, the removal rate was up to 20% after degumming pretreatment. The brightness of the handsheets was 64% ISO, 68% ISO, and 73% ISO, respectively. The dirt count was 2674 mm(2).m(-2), 533 mm(2).m(-2), and 132 mm(2).m(-2), respectively. After Na2C2O4 pretreatment, the tension index and tear index were increased to 40.5 N.m.g(-1) and 4.5 mN.m(2).g(-1), respectively. Through degumming pretreatment, pectin, metal ions, and dirt count were reduced efficiently, and the brightness and physical strength were improved significantly.