Investigation of substituting the organic complex of sulvy-x rather than sodium silicate in CMP pulp bleaching of Mazandaran wood and paper industries

In this study, the effect of elimination and relative decrease of sodium silicate along with substituting the organic complex of sulvy-x was investigated on optical properties of CMP pulp bleached by hydrogen peroxide. The brightness of paper were increased to 66.8%, yellowness decreased to 22% and opacity decreased to 80% with increase in sodium silicate charge from 0.7% to 3%. Also, with complete elimination of sodium silicate and using of sulvy-x at different levels of 0.4, 0.5, 0.7 and 1%, highest brightness and lowest yellowness were shown at 0.5% sulvy-x. These values were 66.1% and 21.8%, respectively. The brightness of paper enhanced from 61.2% to 67.3% with increasing of sulvy-x charge from 0.4% up to 0.5% blended with constant value of 0.7% sodium silicate. But the brightness decreased at higher levels. Generally, pretreatment by DTPA prepared the paper with lower brightness and higher yellowness at two different states namely silicate-free and silicate-containing with sulvy-x. Pretreatment by DTPA at silicate-free state led to decrease of opacity but at silicate-containing state terminated to improve of opacity values. Increasing of bleaching time up to 120 minutes resulted in the paper with higher brightness, higher opacity and lower yellowness at silicate containing state with sulvy-x. At silicate-free state, increasing of bleaching time up to 120 minutes led to improve of opacity while brightness improved and yellowness reduced with increase in bleaching time to 90 minutes. Also, the brightness of paper decreased at higher times (120 minutes) and yellowness increased. In conclusion, achieved results from comparison of optical properties of paper produced from peroxide bleaching of hardwood CMP pulp indicated that we could produce the paper with desirable or even better optical properties by replacing of sulvy-x rather than sodium silicate compared to conventional peroxide bleaching.