Surface characterization of pulp fiber from mixed old newspaper and magazine deinked-pulp with combined cellulase and laccase-violuric acid system (LVS)

The pulp and paper industry is looking for eco-friendly solutions in the field of enzymatic deinking for ink elimination from different recycled papers. The current research aimed at deinking secondary fibers containing mixed 70% old newsprint (ONP) and 30% old magazine (OMG) by combining cellulase with the laccase-violuric acid system (LVS). Optical and strength properties, surface chemical composition, fiber crystallinity, fiber morphology changes during the deinking process, and pulp water retention value (WRV) were assessed by electron spectroscopy for chemical analysis (ESCA), fourier transform infrared spectrometry (FTIR), field emission scanning electron microscopy (FESEM), and the centrifuge method. Results revealed the synergistic delignification and deinking effects of cellulase and LVS making enzymatic treatment a promising alternative for chemical deinking. Pulp deinked with cellulase-LVS indicated a lower ERIC (effective residual ink concentration), better optical and strength properties, a higher oxygen/carbon (O/C) ratio of the fiber surface, a lower surface lignin, higher fiber crystallinity index, and improved pulp WRV. Furthermore, FESEM photographs demonstrated that more fibrils appeared on the fiber surface due to synergistic effects between enzymes. Among the combined cellulase-LVS trials, the C 2 L 2 trial (0.1% cellulase and 20 min; 40u laccase and 120 min) gave a paper with the best quality, the minor lignin surface coverage (or more lignin degradation), and higher cellulose crystallinity, compared to the chemically deinked pulp.