Preparation Of Nano-TiO₂@starch Composite Materials And Study On Dye Adsorption-photocatalytic Degradatio

Aiming at the problem of serious water pollution caused by large wastewater discharge and high dye content in textile printing and dyeing enterprises,this paper combined the advantages of adsorption method and photocatalysis method,using starch-based adsorbent and nano-TiO₂,and developed a kind of dye wastewater treatment material with an integrated function of adsorption and photocatalytic degradation.The main research contents are as follows:Firstly,using corn starch as raw materials,the cross-linked carboxymethyl starch（CCMS）and cross-linked cationic starch（CCS）were prepared by a series of chemical modification including crosslinking,alkalization and etherification.The ionic functional groups—COO^-Na⁺and—N⁺（CH₃）₄Cl^-were introduced into CCMS and CCS respectively.The adsorption performance studies showed that CCMS and CCS with the characteristics of fast adsorption rate and large adsorption capacity for cationic golden X-GL dye（X-GL）and reactive golden SNE dye（SNE）respectively were suitable for use as the adsorption matrix material of composite materials.Subsequently,nano-TiO₂@starch photocatalysis composites were prepared by commercial TiO₂.Under ultraviolet light irradiation,the composites showed good adsorption-photocatalytic degradation to dyes,which indicated that loading nano-TiO₂on starch-based adsorbent for dye wastewater treatment was feasible.Secondly,anatase nitrogen doped nano-TiO₂（N-TiO₂）with band width of 2.56e Vwas prepared by sol-gel method based on alcoholysis.The absorption of light by N-TiO₂widened to the visible region.Under the simulated sunlight irradiation,the photocatalytic degradation for X-GL and SNE by N-TiO₂conformed to Langmuir-Hinshelwood reaction kinetic model.In the process of degradation,the dyes underwent chromophore cleavage,benzene ring opening and mineralization eventually.The TOC of the dye solution was significantly reduced.In addition,N-TiO₂had good recycling performance.After four times of N-TiO₂recycling,the photocatalytic degradation rates of X-GL and SNE could reach more than 80%.Therefore,the synthesized N-TiO₂could be used as the photocatalyst of composite materials.Finally,N-TiO₂was loaded on the surface of CCMS and CCS by improved sol-gel method and the N-TiO₂@CCMS photocatalysis composites（N-TCMS）and N-TiO₂@CCS photocatalysis composites（N-TCS）were synthesized.Under the simulated sunlight irradiation,the adsorption-photocatalytic degradation of N-TCMS and N-TCS had obvious synergistic effect on dye treatment and the adsorption-photocatalytic degradation behavior followed the first-order reaction kinetics.During the process of adsorption-photocatalytic degradation,the TOC of dye solution decreased significantly.Moreover,the N-TiO₂@starch composites were reusable.In addition,N-TiO₂@starch composites played an obvious role in decolorization and purification of different kinds of textile dye wastewater simulated in the laboratory,and the TOC of the wastewater was significantly reduced.In addition,N-TiO₂@starch composite loaded cotton fabric can effectively remove X-GL and SNE molecules from the solution,which preliminarily proved that it had the value of research and development.In conclusion,the N-TiO₂@starch composites prepared in this study could effectively adsorb-photocatalytic degradation dyes in wastewater under simulated sunlight with obvious characteristics of innovation,energy-saving and high efficiency,and played a role in water purification.The N-TiO₂@starch composites had a good development prospect in the treatment of textile ionic dye wastewater in the future.