Effect of medium pH variations on enzymatic deinking efficiency of office waste papers with cellulase from Aspergillus niger

Enzymatic deinking of Xerox printed papers by commercial cellulase from Aspergillus niger fungi was investigated. Enzymatic treatment was done under constant condition of 0.1 percent enzyme based on oven-dried weight of pulp (102 unit per 100 gram oven-dried pulp), 15 min. treatment time, in four pH levels as 4, 5.7, 8 and 9. Then, the effect of pH variation on the appearance and strength properties of the enzymatic deinked pulp was evaluated and compared with those of the control and conventional chemically deinked samples. The study data were analysed with completly randomized design, ANOVA analysis of variance andDuncan mean comparison (P<0.05). The Results showed enzymatic deinking in pH 8 had the best appearance properties and caused improvement in strength properties of handsheets in comparison with chemically treated samples.