عنوان مقاله [English]
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.