Application Of Cellulose-based Composites And Modified Graphene Oxide In Water Pollution Treatment

During the process of industrial development,t the issue of water pollution is becoming more and more serious owing to the massive unreasonable exploitation of rare earth resources and the production of oily wastewater.Therefore,it is particularly urgent and important to solve water pollution.In order to remove rare earth ion pollutants in wastewater and purify the oily wastewater.In this thesis,the effect of adsorbent on the rare earth ion pollutants removal was systematically studied by adsorption method.Meanwhile,the separation of oily wastewater was treated via membrane separation.An adsorption material（GO-g-PAA）with good adsorption properties for Ce（Ⅲ）was prepared by graft copolymerization with graphene oxide（GO）as substrate and acrylic acid（AA）as monomer.The structure,morphology and thermal stability of GO-g-PAA were also characterized by Fourier infrared spectroscopy（FTIR）and scanning electron microscopy（SEM）.The influences of adsorption time,solution p H,adsorbent dosage and Na Cl concentration on the adsorption behavior and mechanism of Ce（Ⅲ）onto GO-g-PAA were systematically studied.The results showed that the adsorption equilibrium was reached within100 min and the adsorption process was in accordance with the pseudo-second-order adsorption kinetic model and the Langmuir adsorption model,which is a typical chemisorption process and single-molecule layer adsorption.The theoretical maximum adsorption capacity of Ce（Ⅲ）on GO-g-PAA was 251.9 mg·g^-1.The samples after the adsorption and desorption were characterized by X-ray photoelectron spectroscopy（XPS）.The XPS results showed that the adsorption of Ce（Ⅲ）onto GO-g-PAA was the cation exchange mechanism.Moreover,the adsorption capacity of GO-g-PAA for Ce（Ⅲ）was 101.9 mg·g^-1 at the p H value of 1,indicating that the adsorbent could be used under strong acid conditions.Therefore,GO-g-PAA has good application potential in removing rare earth ion pollutants from wastewater.On the other hand,cellulose,as the abundant renewable resource,has broad prospects for the development in the treatment of oily wastewater.In this thesis,cellulose-g-PAMPS was prepared by graft copolymerization with microcrystalline cellulose（MCC）as substrate and 2-acrylamide-2-methylpropanesulfonic acid（AMPS）as monomer.Meanwhile,cellulose-g-PAMPS metal-based membrane was prepared by simply coating method with cellulose-g-PAMPS on the surface of stainless steel metal mesh.The cellulose-g-PAMPS metal based membrane with grafting yield of 220%had the largest underwater oil contact angle of 154°.In addition,the above membrane was super oleophobic under water with the oil-water separation efficiency of 98%and flux of 15000 L·m^-2·h^-1.Meanwhile,it still remained underwater oil repellency in 30 wt%Na Cl solution.In order to achieve better treatment effect of oily wastewater,Cellulose-g-PAMPS/Si O₂metal-based membrane was prepared by mixing silica（Si O₂）and Cellulose-g-PAMPS of different quality and then coating it on the metal based membrane.The structure,morphology and thermal stability of Cellulose-g-PAMPS and Cellulose-g-PAMPS/Si O₂ were characterized by FTIR,TGA and SEM,respectively.Cellulose-g-PAMPS/Si O₂metal-based membrane had better thermal stability than that of cellulose-g-PAMPS metal-based membrane.It was found that when the mass of Si O₂ was 80 mg,the maximum underwater oil contact angle of Cellulose-g-PAMPS/Si O₂ metal based membrane was 164°and the rolling angle was 1.3°,respectively.In the test of oil-water separation performance,the oil-water separation efficiency and flux of Cellulose-g-PAMPS/Si O₂metal-based membrane was 98%and 25000 L·m^-2·h^-1,respectively.Furthermore.In addition,under the conditions of different concentrations of Na Cl solution and p H,the separation efficiency of the membrane was maintained at about 98%,which had little effect on the separation efficiency.The prepared Cellulose-g-PAMPS/Si O₂ metal-based membrane can successfully separate water and oil from different oil-water mixtures,such as vacuum pump oil,n-hexane,petroleum ether and n-dodecane.In summary the prepared oil-water separation material has a certain application potential in the treatment field of oil-bearing wastewater.