Study On Enzymatic Deinking Of Laser Printed Office Waste Paper

The lack of forest resources in our country has caused the raw material shortage for paper-making industry. With the improvement of people’s consciousness of environmental protection, people pay attention to waste paper recycling. The recycling of waste paper should have the deinking process. However, chemical deinking process may cause secondary pollution, the strength of recycled paper would be retrogressed and the color prone to turn yellow. Enzymatic deinking which decrease the second environmental pollution. However, the biological treatment will take a lot of time and the recovery rate of paper is low, current research is still in the laboratory.In this paper, we study the efficiency of different kinds of enzyme(such as neutral cellulose enzyme, acid cellulose enzyme, xylanase, alpha amylase and lipase) and surfactant(such as Tween-60, Tween-80, RQ-129C、RF-25、RF-25-2, Sodium dodecyl benzene sulfonate) for the deinking process of laser printing office waste paper. The paper focus on the brightness of pulp and the recovery rate of pulp. There are less reports on the study of using of Tween-60, Tween-80 in the deinking of waste paper.The paper determine the optimum enzyme reaction and flotation conditions of various enzymes. Enzyme reaction factors include dosage of enzyme, temperature, medium pH, time and density of pulp. Flotation factors include time, the flow of gas, the dosage of surfactant.When neutral cellulose was used in experiments to deink, the optimum conditions for surfactant is Tween-60, enzyme reaction temperature is 50℃, pH 5.0, the dosage of enzyme 0.912 U/g·pulp, enzyme reaction time 1.5 h, the concentration of pulp 12.5 g/L, the time of flotation 12 min, the flow of gas 235～299 ml/min, the concentration of Tween-60 0.08 g/L. Recycled pulp whiteness of 99.5%, the pulp yield of 73.7%. After the secondary flotation, the comprehensive recovery rate of pulp can reach 90.5%. When the other enzyme was used in experiments to deink, in the optimum condition, the paper pulp whiteness is 96.8%～99.6%. This paper also studied the efficiency of compound enzyme deinking, the effect of acidic cellulose/xylanase deinking is best among these compound enzyme, the whiteness of pulp can reach 99.1%. When two or three kinds of surfactant were used in experiments to deink, the efficiency of deinking was better than single surfactant.