Preparation Of TiO₂/copper Algae-based Activated Carbon Composite Material And Study On Its Photocatalytic Degradation Of PAHs

With the rapid development ofindustrial society,contamination of polycyclic aromatic hydrocarbons?PAHs?has become more and more serious in water environment,which has caused great harm to human health.TiO₂ photocatalysis is one of the most widely used technologies for PAHstreatment,whereas,series of problems have to be solved in its practical applications,including lower light utilization efficiency,easy recombination of photoelectrons-holes,et al.In this paper,different activated carbons?ACs?were prepared by using Sargassum horneri as raw material,accompanied with FeCl₃,ZnCl₂and FeCl₃+ZnCl₂?CA?as activators,and responsiveTiO₂/AC composite were synthesized with above-mentioned ACs as carrier.The BET specific surface area analyzer,X-ray diffraction analyzer?XRD?,scanning electron microscopy?SEM?,X-ray photoelectron spectroscopy?XPS?,UV-vis diffuse reflectance spectra?UV-vis DRS?were used inmaterial characterization.The composite materials were applied in removing a kind of typical PAHs,i.e.,naphthalene,during which critical parameters affecting adsorption and degradation were systematically studied,meanwhile,the responding kinetics were investigated.The results showed that?1?In the preparation of activated carbon,the activator residuals were found in the activated carbon with the form of iron oxide.Nano TiO₂particulatesprepared in this paper showed anatase type,and the iron group were divided into Fe₂O₃ and FeO forms,with the main valence stateas positive trivalent.The residual iron components in TiO₂/AC-FeCl₃ and TiO₂/AC-CAwould combinewith TiO₂ semiconductor,which resulted in the absorption band edge red shift.At the same time,adherence ofthe tiny particles ofTiO₂were observed on the outer and inner surface of the activated carbons.Compared with activated carbon,TiO₂/AC composites showed smaller specific surface area and larger total pore volume and pore dimension.?2?Activated carbon provided a special reaction pathway to photocatalytic reaction,andenriched naphthaleneto a certain degree,whichconcentratednaphthalene around the active center,thus making reaction equilibrium positive shift.For TiO₂/AC-CA,the degradation efficiencywas the highest when the dosage was 0.6g/L,and those of TiO₂/AC-FeCl₃ and TiO₂/AC-ZnCl₂ were all 0.8 g/L.With the increase of pH,the removal efficiency of naphthalene gradually showed obvious decrease tendency.Sequentially,the naphthalene degradation efficiency is TiO₂/AC-CA,TiO₂/AC-ZnCl₂,TiO₂/AC-FeCl₃,and those of direct mixing of TiO₂ and activated carbon.?3?The degradation efficiency of TiO₂/AC-FeCl₃,TiO₂/AC-ZnCl₂ and TiO₂/AC-CA was reduced from 65.0%to 50.0%,71.0%to 54.5%,and 77.5%to64.0%after 3 cycles,and kept almost stableduring the following 3 cycles.?4?The degradation of naphthalene by 3 kinds of composite materials were proved to conform withthe first order kinetics equation of Langmuir-Hinshelwood model.The degradation rate of TiO₂/AC-CAis higher than that of TiO₂/AC-FeCl₃ and TiO₂/AC-ZnCl₂,which indicated that the adsorption of activated carbon in TiO₂/AC composites make positive and synergistic effect on photodegradation.