Study of the enzymatic/neutral deinking process of waste photocopy paper

Enzymatic deinking was performed by mean of common commercial enzymes, whereas the neutral deinking is a process achieved in a chemical environment that provides a pH of about 7.0, and usually with application of only surface tension agents. This work performs the deinking process in neutral conditions, with enzymatic pretreatment of the waste paper pulp, and using ethoxylated fatty acids as surfactant. The enzyme employed in the pretreatment is cellulase or amylase, and the enzymatic activity for these enzymes was evaluated according to IUPAC rules and based on temperature and pH values, as by the supplier. This paper studied the influence of HLB of surfactant in combined processes of enzymatic/neutral deinking. These deinking processes are to cause less environmental impact than the process commonly used in alkaline environment. It studied the process in waste photocopy paper. For comparison, a pulp without enzymatic pretreatment was used. The deinking enzymatic/neutral process is carried out by flotation at a stock consistency of 0.8%, with a 6 minutes flotation phase at 40°C temperature. In the deinking enzymatic/neutral process, the applied enzymes doses are 0.06%, 0.105% and 0.15%, and the ethoxylated fatty acids employed of HLB are 12, 14 and 16. Optical properties were determined as reflection factor at 457 nm (brightness ISO), not eliminating measurement points. For waste photocopy paper the maximum values of brightness ISO is 78.9% and 80.6% when cellulase and amylase are used in enzymatic pretreatment, respectively.