Enzyme deinking of laser and xerographic printed wastepapers produced in the Philippines

Laser and xerographic printed papers (50:50 ratio by weight) were deinked with a mixture of cellulases and hemicellulases (CELLULYVE TR400) at different pH levels, enzyme dosages and floatation times. Deinking was undertaken by repulping shredded laser and xerographic printed papers (LXPP) at 60 deg C in an aqueous solution (10% consistency) containing the enzyme. After enzymatic treatment, the mixture was transferred to a floatation cell to remove the ink. In the floatation cell, the temperature ranged from 35-45 deg C, 1% consistency and pH of 6.5-7.5 were used. The floatation-deinked stocks samples were washed with water at room temperature and deactivated with hot water (90-95 deg C) for 10 minutes. The resulting pulps were formed into handsheets and tested for brightness, effective residual ink concentration (ERIC) and strength properties (burst, tear and tensile indices). The enzyme-deinked pulps exhibited higher brightness and lower effective residual ink concentrations than the untreated and conventionally deinked paper. The gain in brightness ranged from 2 to 8 units while ERIC reduction was up to 70%. Brightness values of enzyme deinked pulps at pH 7 and 8 were significantly higher than those deinked at pH 5 and 6. Tear and burst strengths of the enzyme-deinked LXPP were not adversely affected by the treatment while the tensile strength increased. Based on statistical analysis, the deinking conditions for laser and xerographic printed papers that resulted in handsheets with the most acceptable properties were at pH 8, 10 min floatation time and 0.4% dosage for the enzyme used in the study. Final enzyme deinking trial was conducted using pH of 8, 10 min floatation time and 0.4% enzyme dose. Statistical analyses showed that the properties of the handsheets produced were better than the handsheets from the preliminary enzyme deinking and conventional deinking trials. The deinked handsheets produced from the final deinking trials were brighter than those deinked from the preliminary trials. Brightness of handsheets from the preliminary trials averaged 87.5% ISO [International Standard Organization] while the averaged value for ERIC was 47. The average burst, tensile and tear indices of handsheets made from the final trials were (4.36 kPa.m.2/g, 48.42 N.m/g and 11.47 mN.m2/g, respectively) which were higher than those in the preliminary trials. The differences could be attributed to the use of non-metallic container during repulping stage in the final trial. Both the enzyme old deinking chemicals exhibited an ability to reduce toner ink from LXPP. However, the CELLULYVE TR400 showed a greater efficiency in removing the particles of ink than the deinking chemicals