The Effect Of Fenton Pretreated Fibers Surface On Paper Physical Properties

Fenton system is an environmentally friendly oxidation technology with strong oxidation ability and low cost.In recent years,it has been widely applied and studied in polysaccharide polymers,such as hemicellulose,cellulose and starch.In this paper,carboxymethyl cellulose(CMC)with large molecular weight is used as the carrier of Fe2+catalyst in fenton system,and the catalyst is fixed on the fiber surface,so as to realize the modification of unbleached softwood kraft pulp and chemical mechanical pulp fiber surface.The mechanism of CMC adsorption of Fe2+ catalyst and the distribution of Fe2+catalyst on the fiber surface were analyzed through FTIR,UV-Vis,SEM-EDS and other analytical methods.At the same time,the influence of Fe2+dosage,H2O2 dosage and pretreatment time of CMC-Fe2+composite catalyst on the tensile index of paper were explored.FTIR and UV-Vis analysis results showed that hydroxyl and carboxylic acid roots of CMC could form coordination bonds with Fe2+catalyst and form stable CMC-Fe2+composite catalyst because of the strong electrostatic interaction between Fe2+and CMC.SEM-EDS of CMC-Fe2+composite catalyst showed that Fe2+could ion exchange with CMC,which significantly reduced the content of sodium in CMC,Fe2+ composite catalyst while the content of iron increased from 0 to 7.22.And then iron distribution in the CMC-Fe2+composite catalyst in the fiber was analyzed by SEM-EDS.it was found that the content of Fe2+ on the surface of the pulp fiber was significantly higher than that inside the fiber,because the CMC-Fe2+ composite catalyst existed in the form of macromolecular organic compounds,which indicated that the CMC with large molecular weight could effectively bind the Fe2+ catalyst to the fiber surface.The effects of Fenton oxidation methods on the average degree of fiber polymerization,fiber morphology,zero-span tensile strength and physical properties of paper were investigated by using CMC-Fe2+ composite catalyst and Fe2+ catalyst respectively.The results showed that the average degree of polymerization of unbleached softwood kraft pulp fibers decreased by 5%,the length of fibers was basically the same as that of the original pulp,the kink index showed an upward trend,and the zero-span tensile strength of fibers decreased by less than 2%.This indicated that the strength of fibers oxidized by CMC-Fe2+ composite catalyst had little influence on the strength of fibers.However,after the oxidation of unbleached softwood kraft pulp fibers with Fe2+ catalyst,the fiber length and zero-span tensile strength showed a significant downward trend.When the oxidized unbleached softwood kraft pulp fibers were beaten for 8000 r,the specific beating energy consumption of pulp decreased by 9%,the tensile index of paper increased by 6.9%,the tear index decreased and the whiteness of paper decreased slightly.With chemical mechanical pulp as raw material oxidized by CMC-Fe2+composite catalyst,the specific beating energy consumption of pulp fibers decreased by 31%,the average length of fibers decreased by 7%,the zero-span tensile strength decreased from 71.5 N·m-1 to 65 N·m-1,the length of fibers decreased by 7%,the fine fraction content of fibers increased by 7%,tensile index of paper increased by 18.1%and tear index showed a downward trend.