RESUMO
The charge densities (CD) and molecular weights (MW) of the flocculants are closely related to their application performances, but seldom researches focus on the effects of flocculant CD and MW on decolorization efficiencies. Herein, a series of flocculants with various CD and MW levels, named as PBF1-9, were designed and synthesized from papermaking sludge. The physicochemical characteristics of the PBF1-9 were measured by fourier transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), X-ray photoelectron spectroscopy (XPS) and particle charge density analyzer (PCD). The efficiencies of PBF1-9 were studied in the reactive blue (RB) dye removals by flocculation under different process conditions. The operation costs of the flocculants were evaluated at their optimal dosages. Also, the pH-independences and ion-tolerances of the aforementioned flocculants were studied in terms of the molecular levels. The experimental results exhibited that the flocculants CD or MW values were relevant to their flocculation behaviors and operation costs. CD values played a dominant role in color removal efficiencies and the costs, whereas MW values were critical to the floc structure. The pH or ion-independences of the flocculants were significantly dependent on the CD and MW values. However, some conclusions, conflicted with prior studies, were observed in this work. For instance, flocculant with the highest CD and MW levels was not the most effective one in enduring pH variation and the coexisting ions. The floc properties, including floc size, resistance and recovery ability, were relatively insensitive to flocculant intrinsic CD and MW levels when the flocculants were used at their optimal dosages. Furthermore, the possible relevance between CD or MW levels and the flocculation mechanisms have been proposed in this work. Exploring the effects of flocculants CD and MW levels could precisely control the flocculant characteristics to achieve satisfactory decontamination efficiencies with low costs.
RESUMO
Enzymatic hydrolysis is considered an efficient and environmental strategy for the degradation of organic waste materials. Compared to mesophilic cellulases, thermostable cellulases with considerable activity are more advantageous in waste paper hydrolysis, particularly in terms of their participation in synergistic action. In this study, the synergistic effect of two different types of thermostable Chaetomium thermophilum cellulases, the endoglucanase CTendo45 and the cellobiohydrolase CtCel6, on five common kinds of waste papers was investigated. CtCel6 significantly enhanced the bioconversion process, and CTendo45 synergistically increased the degradation, with a maximum degree of synergistic effect of 1.67 when the mass ratio of CTendo45/CtCel6 was 5:3. The synergistic degradation products of each paper material were also determined. Additionally, the activities of CTendo45 and CtCel6 were found to be insensitive to various metals at 2 mM and 10 mM ion concentrations. This study gives an initial insight into a satisfactory synergistic effect of C. thermophilum thermostable cellulases for the hydrolysis of different paper materials, which provides a potential combination of enzymes for industrial applications, including environmentally friendly waste management and cellulosic ethanol production.