investigation on bleaching of mixed old newspaper and magazine deinked pulp with hydrogen peroxide

in the present research, the effect of different peroxide charges and reaction times were investigated inhydrogen peroxide bleaching of mixed old newsprint and old magazine deinked pulp. in thebeginning, mixed recycled papers were pulped using conventional method and then deinked byflotation. in addition, deinked pulps (mixture ratio of 70% onp and 30% omg) were bleached withhydrogen peroxide at different charges of 0.5, 0.75 and 1% from peroxide and times of 30, 60 and 90min under constant process conditions. the bleached pulps refined with laboratory pfi mill to freenessof 300 ml, csf and then standard handsheets (60gm-2) were made from them. the residual peroxideexisting in bleaching liquor, chemical oxygen demand (cod) of bleaching effluent and also the paperquality properties (optical, physical and strength properties) were measured according to respectedstandards. obtained results indicated that with increase in bleaching times, the residual peroxide inliquor was decreased but the differences of them was insignificant (p