| With the increasing shortage of resources on earth, cellulose as an inexhaustible supply natural polymer materials becomes more and more popular in many fields. And the development of nanotechnology, has also led to the development of nano cellulose based materials. Due to the good dispersibility and stability, high specific surface area and porous structure of three-dimensional space, nano microfibrillated cellulose is widely used as the matrix applied to composite material, biomedical, metal carrier and wastewater repair.The bleached bamboo pulp was pretreated through the neutral TEMPO/ Na Cl O/ Na Cl O2 process under microwave radiation technology, and then microfibrillated cellulose(MFC) was prepared by ultrasonic mechanical process; And then NZVI/MFC composite material was in situ prepared by chemical reduction method in the liquid phase; NZVI/MFC composite materials were utilized in the advanced treatment of papermaking wastewater. The results of this study were summarized as follows:(1) The optimum conditions of the neutral TEMPO/ Na Cl O/ Na Cl O2 under microwave radiation method were listed: oxidation reaction temperature 60℃, 2hours of reaction time, 0.15mmol/g of TEMPO dosage, 1.0mmol/g of Na Cl O dosage, 10mmol/g of dosage Na Cl O2(based on oven dry pulp). Compared with conventional heating process, microwave radiation can greatly shorten the oxidation time, improve the oxidation efficiency, thus effectively inhibited the degradation of cellulose during the reaction.(2) After the preoxidaton process, the bleached bamboo pulp was treated by ultrasonic process for 2 hours. And the prepared MFC solution is completely transparent, and has a uniform diameter distribution(5~15nm) and high length diameter ratio. Samples were characterized by AFM which shows that MFC has the structure of three-dimensional network. The special structure of MFC, provided a guarantee for the application of adsorption carrier, composite materials etc.(3) The NZVI/MFC composite was prepared in situ by chemical reduction in liquid phase. We found that NZVI/MFC composite solution has good dispersion stability, and can effectively slow down the oxidation of zero valent iron. SEM-EDS was used to analyze the surface element, and the results show that MFC has been loaded Fe element successfully, and when the ratio of m(Fe) /m(MFC) ratio reaches 15%, the load rate of Fe actually comes to 81.6%. The state of aggregation of the prepared NZVI/MFC composite materials was observed by AFM, with staggered three-dimensional space and it is good for the advanced treatment of papermaking wastewater. TG analysis show that with increase of iron content, the maximum mass loss temperature of NZVI/MFC composite materials is reduced.The maximum mass loss temperature has dropped from 303℃ for MFC to 290℃ for NZVI/MFC composite. The data indicate that the thermal stability of NZVI/MFC composites is actually decreased, compared to MFC.(4) The optimal conditions of NZVI/MFC composite materials for advanced treatment of papermaking wastewater are included: room temperature(25 ℃), 1.0g/L of the dosage, p H 5.And the removal rate of CODcr is 52.5% and chroma is 70.2%. The Fe2+ or Fe3+/MFC composite materials was also used to the first flocculation. After that, advanced treatment process by addition of NZVI/MFC and then sand filtration process, the overall removal rate of the total CODcr is 78.4% and the total color is 90.7%. And the theoretical analysis show that CODcr and chroma are reduced by redox reaction between Fe0 and organic residues, as well as the strong adsorption of high specific surface area of MFC substrates. Therefore the NZVI/MFC composite materials has a good application prospect in the advanced treatment of papermaking wastewater. |
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