Repulping high wet-strength waste banknote paper by a dual-ph pretreatment process

Abstract

A repulping approach of waste Chinese banknote paper, i.e., Renminbi (RMB) paper with high wet strength, was studied, and a dual-pH pretreatment process was used before refining. Pretreatment temperature, soaking time, and consistency of waste RMB paper were investigated to obtain the optimum repulping parameters. The results showed that when the pretreatment temperature was 80 °C, soaking time was 60 min, and consistency was 10%, the repulping yield was 88.1%. The arithmetic and weighted mean lengths of fine pulp fibers from the optimum experiment were 0.564 mm and 0.785 mm, respectively, and the mean width was 22.5 μm. Obvious kinks and broken ends, as well as a slight curl of fine pulp fibers were observed by analyses with a Morfi-compact fiber analyzer and a scanning electron microscope. The results from Fourier transform infrared spectroscopy analysis possibly demonstrated that the ester bonds in waste banknote paper were destroyed after the dual-pH pretreatment.