| Recently,Antibiotic contamination has become increasingly serious.Due to the characteristicsits of low concentration,refractory degradation and inhibitory effect on microorganisms,conventional biochemical and physicochemical water treatment processes are not ideal methods to remove antibiotics.While TiO2 photocatalytic technology can rapidly and effectively degrade trace organic pollutants in mild environment without secondary pollution,which shows good application prospects in antibiotic wastewater treatment.However,there are some problems in TiO2 photocatalysis,such as high photogenerated carrier recombination rate,limited contact with low concentration antibiotics,easy reunion during preparation,non-selectivity to different pollutants,etc.,which leads to low photocatalytic efficiency and is not conducive to the rapid and complete removal of antibiotics.In order to solve the above problems,the graphitized mesoporous carbon(GMC)-TiO2 composite photocaftalyst was prepared in virtue of the high adsorption and conductivity of graphitized carbon,and used for synergistic adsorption-photocatalytic degradation of ciprofloxacin(CIP).Meanwhile,in order to increase the selectivity of the catalyst,the molecular imprinting technology and photocatalytic technology were coupled to make molecular imprinting on GMC-TiO2 surface.Specific research contents are as follows:(1)GMC-TiO2 composite photocatalyst was synthesized under low temperature hydrothermal conditions using resorcinol-formaldehyde as carbon source and TiCl3 as titanium source.In the composite,the lamellar GMC nanosheets possessed a large specific surface area and mesoporous structure,and could adsorb and enrich antibiotics effectively.This could not only significantly reduce the concentration of antibiotics in water shortly,but also greatly increase the chances for the antibiotics to contact with and be degraded by the photocatalysts and active species.Interestingly,GMC could also facilitate the transportation of photogenerated electrons to further improve the photocatalytic efficiency of TiO2,and 15 mg/L ciprofloxacin(CIP)could be totally mineralized in 1.5 h.Meanwhile,the biological inhibition of reaction solution on luminescence bacteria decreased obviously with antibiotics degradation until non-toxicity.In addition,from the viewpoint of organic chemistry,several plausible CIP degradation pathways were established by using HPLC-MS technique,and an interesting intermediate with five-membered ring structure was firstly proposed,which is very helpful to deeply understand CIP degradation.Strong synergy between adsorption and photocatalysis,along with quick and efficient antibiotics elimination,double confirm the great potential of GMC-TiO2 nanocomposite for practical antibiotic wastewater purification.(2)Based on the above results,in order to improve the selectivity,GMC-TiO2 surface molecularly imprinted photocatalyst(denoted as GMC-TiO2@MIP)was successfully prepared by using GMC-TiO2 as matrix and CIP as template,to achieve effectively selective adsorption and photocatalytic removal of specific contaminant.It was found that the imprinting occurred on matrix surface without affecting the crystal form and composition of the matrix,and the mass ratio of matrix to imprinted polymer had a great influence on the adsorption-photocatalytic performance of CIP.The saturated adsorption capacity and photocatalytic degradation rate constant of CIP prepared by the optimal ratio were 7.2 times and 3 times that of the competitive pollutants of sulfamethoxazole(SMZ),respectively.In addition,study also investigated the effect of solution pH and typical coexisting material HA on contaminant removal.The degradation process of CIP analyzed by HPLC-MS showed that the degradation of CIP on GMC-TiO2@MIP was more effective and thorough than GMC-TiO2.Therefore,GMC-TiO2@MIP prepared in this study shows the great potential for selectively degrading specific contaminant in the environment. |
PDF Full Text Request