Synthesis Of Chitosan-TiO₂ Multifunctional Composite And Its Environmental Application

With the aggravating of industrial wastewater pollution, more and more innovative technologies for the removal of pollutants from wastewater have been studied. Based on high adsorption performance of bioadsorbent and excellent catalytic activity of photocatalyst, a novel strategy of combining chitosan and TiO2 has been proposed for its nontoxicity and environmental friendly. Here, we have prepared both globular and membranous chitosan/TiO2 composites, and further studied their application for adsorption, degradation and antibacterial property.Three chitosan/TiO2 composites had been prepared by solution blend, which including ion-imprinted chitosan/TiO2, chitosan/TiO2/Fe3O4 microspheres and membranous chitosan/TiO2/polypropylene fiber, and then applied to the removal of Cu2+ and AMP. Results indicated that membranous composites exhibit better properties of adsorption/degradation than globular composites.Because of the space steric effect of chitosan, composites prepared by blending technology were not good at degradation of ampicillin. To handle this problem, grafted TiO2/chitosan/polypropylene fiber (TCP) was fabricated and explored to degrade ampicillin under UV light with 365nm wavelength. When exposed in strong acid/alkali condition, this grafted composite showed higher removal efficiency. As the light intensity increase, the degradability of AMP increased, and this process was also promoted by adding Zn2+ or Fe3+. Photocatalytic reaction with 40W light intensity occurred more than 3 times faster than the case of 20W. The degradation cycle was repeated 5 times under 40W UV light, and the degradation ratio still reached 97%.A modified Ag2O/TiO2/chitosan/polypropylene fiber (ATCP) was prepared for the realization of application in natural light. The graft structure and Ag2O as the existence forms of Ag element were confirmed by SEM, HRTEM, XRD and XPS. Ag2O/TiO2 nano-particles were successfully deposited on chitosan/polypropylene fiber, and presented an enhanced adsorption in the visible region from 500 to 600nm with maximum at 545nm, and band-gap was estimated at 2.4eV. The photocatalytic degradation capability of ATCP was evaluated by decomposing ampicillin (C0=20mg·L-1, V=40mL) and methyl orange (C0=10mg·L-1, V=40mL) under the halogen lamp emitted UV-vis light. Coated with 0.06g catalyst of the composites degraded AMP and MO completely in 180min and 30min, respectively. In addition, ATCP also exhibited highly efficient antimicrobial activity in inactivating different test strains of E. coli and C. albicans within a 100% bactericide rate in 1h.Our work provides a new method for TiO2 immobilization using chitosan as substrate. Both grafted TiO2/Chitosan/Polypropylene fiber and Ag2O/TiO2/Chitosan/Polypropylene fiber were prepared by simple green methods. TCP and ATCP can be applied to efficient degradation of organic pollutants under UV and fluorescent lamp respectively. With such simplified process of preparation, operation and separation, these composite materials can be potentially used in industrial decontamination.