STUDIES ON DEINKING OF ONP WITH ENZYMES AND EFFECT OF PECTINASE TREATMENT ON THE PROPERTIES OF DCS RELEASED FROM ONP

Cellulase blended with xylanase at certain ratio was used for deinking of the old newsprint (ONP) to obtain their optimal ratio. The effect of enzyme treatment on the properties of the deinked pulp was compared. Experimental results showed that, compared with the pulp deinked with traditional alkaline deinking, brightness was little decreased for the enzymatic deinked pulp. After being bleached by H2O2, enzymatic deinked pulp gave higher brightness, better strength properties and lower effective residual ink concentration (ERIC), compared with the control pulp deinked. Compared to the other enzymes, the addition of cellulase B and xylanase D was the most effective in deinking ONP among the enzymes. In addition, the effects of pectinase treatments on dissolved and colloidal substances (DCS) released from the process of the bleaching have been discussed. When pH was 9.0, the dosage of pectinase was 40U/L-DCS, 45 degrees C and the treatment time was about 2h, and the cationic demand (CD) of DCS was decreased by 15%.