Effect of Sodium Silicate on The Optical and Physical Properties of ONP Deinked Pulp

This study was aimed to investigate the effect of different charges of sodium silicate on chemical deinking of old newspaper. Chemical deinking process was accomplished with 1% hydrogen peroxide, 1% sodium hydroxide, 0.3% DTPA and 0.15% surface active agent at different charges of 0, 1, 2 and 3% sodium silicate on the basis of oven dry waste paper. The results of the optical properties of produced paper showed that the brightness of paper improved (50.9%) and the yellowness decreased (11.33%) with increasing of sodium silicate charge to 2%. Increasing of sodium silicate use from 0.3% did not indicate significant effect on opacity values. The highest opacity (98.8%) was achieved by 1% sodium silicate. The results of the physical properties indicated that increasing of sodium silicate use up to 2% resulted the paper with the highest bulk (2.75 cm³/g). Totally, the consequences of this research in relation to chemical deinking of old newspaper at different charges of sodium silicate showed that use of 2% sodium silicate would lead to produce the paper with higher brightness, caliper and bulk along with desirable opacity.