the effect of different conditions of enzymatic deinking on optical properties of onp deinked pulp with cellulase

deinkability of old newspaper was investigated using cellulase at different concentrations and treatment times. the results of optical properties of the made papers indicated that by increasing the enzyme concentration to 0.05 percent the brightness was increased to 47.5% iso and yellowness decreased to 11.03% iso. while at higher charges than 0.05 percent, brightness value the was decreased and yellowness increased. opacity of paper was improved to 99.3% iso by increasing the enzyme charge to 0.1% but it was reduced at higher levels than 0.1%. it was observed that enhancing of treatment time to 15 minutes and also using one-stage washing resulted in the highest brightness of 47.5% iso, the lowest yellowness of 11.03% iso and the opacity of 97.4% iso. maximum opacity was observed at treatment time of 10 minutes. with regard to the results from paper provided with enzymatic deinking of old newspaper, we could produce the papers with desirable brightness and low yellowness using optimum charge of 0.05% cellulase and treatment time of 15 minutes along with one-stage washing. we could also obtain higher opacity values using 0.1 percent enzyme or 10 minutes treatment time.