Response surface methodology for optimization of peracetic acid pretreatment of pulp to reduce pollutants from bleaching effluent

Pulp bleaching processes emit many toxic substances. Peracetic acid (PAA) has been long recognized as an efficient bleaching agent for cellulose pulps. In the present study, 20 runs were conducted using response surface methodology (RSM) through central composite design for optimization of peracetic acid treatment of hardwood pulp, as a pretreatment step before applying conventional bleaching. Three factors, namely temperature (50-80 °C), time (0.5-2.0 h) and PAA dose (0.5-2.0%), were investigated to find out their impact on the kappa number, yield, brightness and viscosity of the pulp. The findings revealed that the peracetic acid dose of 1.0% at 80 °C for 1.0 h was the most suitable to obtain pulp of kappa number 10.2, yield of 96.87%, brightness of 43.6% ISO and viscosity of 11.7 cP. FTIR analysis revealed that the peracetic acid pretreatment of the pulp led to lower lignin content, compared to untreated pulp, but also reduced the bleaching effluent parameters, such as BOD, COD, TDS, color and AOX, by 43.0%, 55.7%, 31.9%, 51.4% and 51.1%, respectively.