Synthesis And Photocatalytic Antibacterial Performance Of SA/TiO₂

In recent years,water pollution broke out frequently caused by microorganism,while traditional water disinfection techniques in practical applications existed disadvantages.Therefore,in this paper,SA/TiO2,as an antibacterial agent,was successfully synthesized by sol-gel hydrothermal method.Its performance was characterized,and the synthetic mechanism was studied.Also,the antibacterial effect of SA/TiO2 on E.coli and its influence factors were investigated,and the photocatalytic antibacterial process of SA/TiO2 was analyzed.The main results were as follows:(1)SA/TiO2 was synthesized in-situ by sol-gel hydrothermal method.The influences of SA/TiO2 on the antibacterial performance were investigated using the log reduction of E.coli as the evaluation index,such as different raw material molar ratio,in-situ water content,hydrothermal temperature,hydrothermal time.The optimal preparation parameters of the catalyst were as follows:n(Ti):n(SA)=1:0.05,ethanol 60 mL,glacial acetic acid 40 mL,hydrothermal temperature 180?,hydrothermal time 12 h were determined.(2)The physical and chemical properties of SA/TiO2 were characterized by XRD,FT-IR,XPS,SEM and BET.The results indicated that sorbic acid was amorphous and TiO2 existed as pure anatase phase in SA/TiO2.The modification of sorbic acid could affect the particle size and morphology of TiO2.The photocatalyst showed regular spherical particle with larger specific surface area and improved dispersibility,which could enhance photocatalytic antibacterial efficiency.The band gap of the catalyst slightly rose,which enhanced photocatalytic redox capability.According to the characterization of SA/TiO2 by FT-IR,sorbic acid was bonded to the TiO2 system by bridging coordination.(3)The effects of different catalyst amount,the illumination time and the light intensity on the antibacterial performance of the photocatalyst were investigated in the antibacterial test.The results showed that the log reduction reached 5.43 log under the 15 w UV light irradiation for 60min as the catalyst amount was 0.7 g L-1.In the dark,SA/TiO2 exhibited antibacterial activity,indicating that the synergistic effect of sorbic acid and TiO2 enhanced the antibacterial property of the composite catalyst under darkness.(4)Humic acid had certain effect on the antibacterial performance of the photocatalyst,however,when the humic acid concentration was below 15 mg-L-1,it had slight influence on the antibacterial property,and the log reduction maintained at 3.81-4.31 log.(5)The influences of SA/TiO2 on the cell morphology,membrane permeability,cellular content,and genetic material of E coli were investigated.The two pathways of photocatalytic antibacterial activity of SA/TiO2 were as follows:first,SA/TiO2 particles contacted with bacteria directly,resulting in the rupture of the cell wall(membrane).Second,SA/TiO2 produced reactive oxygen species which entered the cell interior through the damaged cell wall(membrane),and cleaved double-stranded DNA in the light.Eventually these caused the bacteria to die.