Effect Of Water Quality Conditions On The Photocatalytic Degradation Of Carbamazepine

With the development of human society and the progress of science and technology,various drugs gradually enter into people's daily life and are widely used.They bring convenience to body health and also leave potential safety hazards to people.Those medicines that have not been absorbed completely will enter the aquatic environment along with the discharge of waste water so as to cause adverse effects on the water environment and ecosystems.In addition,drugs can be enriched into the human body through the food chain,thus affecting human health.As a new type of environmental pollutants,Pharmaceutical Active Compounds?PhACs?have become one of the hot spots in the field of environmental research.The research on photocatalytic oxidation technology,which has merits of easy to operation,low energy consumption,no secondary pollution and high degrading efficiency,will bring hope for the complete removal of PhACs in water bodies.At present,most researches of photocatalytic degradation of carbamazepine?CBZ?still stay in the laboratory to determine the influencing factors of artificial water distribution,but there are few studies on the effects of water quality conditions in actual water bodies.CBZ,a typical representative of the commonly used PhACs,can not be removed by conventional processes because of its poor biodegradability.Therefore,CBZ was selected as the target to check the influence of solid suspended solids?SS?,inorganic salt?IS?and dissolved organic matter?DOM?on CBZ degradation.The main research results are listed as follows:?1?The composite ZnIn₂S₄/TiO₂ catalyst was prepared by hydrothermal method.The prepared catalysts were characterized by X-ray diffraction,specific surface area,UV-vis diffuse reflectance spectroscopy,scanning electron microscopy and X-ray fluorescence spectrometer.The results showed that the composite TiO₂ did not change the crystal structure of ZnIn₂S₄ but change the morphology of the catalyst.Moreover,the addition of TiO₂ improves the response of the catalyst to UV light and slightly reduces the visible light absorption capacity.Compared with pure ZnIn₂S₄,the amount of element S decreased but In and contents increased in the composite catalyst by XRF determination,and both pore volume and pore size increased for composite catalyst on the basis of BET results.?2?The effluent of rotating filter from the third wastewater treatment plant?WWTP?in Xi'an city was taken as the substrate to check the activity of catalyst.It was found that the optimal composite ratio was 17/10 to ZnIn₂S₄/TiO₂ and the best dosage was 0.06g/800mL?equivalent 75mg/L?.Under irradiation of iodine gallium light,the effects of SS,IS and DOM on CBZ degradation by photocatalytic oxidation in four water samples?Chanhe river,secondary sedimentation tank,rotary filter,disinfection tank?were checked.It was showed that these three factors inhibited the photocatalytic degradation of CBZ with various degrees.The degradation of CBZ in water followed first-order kinetics,and the rate constant increased from 0.0639 min^-11 to 0.1324 min^-1and the half-life reduced to half after the removal of DOM,SS and IS.The order of influencing factors was DOM>IS>SS.Three water samples from the real WWTP were similar to the Chanhe river and the rate constant increased from 0.0307min^-11 to 0.1506min^-1and the order was IS>DOM>SS.Under sunlight irradiation,there was also a certain degradation effect on CBZ in the water sample,but lower than the degradation rate of iodine gallium light,which is due to the insufficient utilization of sunlight.DOM,IS and SS also inhibited the degradation of CBZ.CBZ in water samples of Chanhe river was only degraded 32.85%after 240 min reaction,but the removal reached 100%after210 min reaction in the treated samples without DOM,SS and IS.?3?The effect of Cl^-,SO₄^2-,NO₃^-inorganic anions and humic acid on photocatalytic degradation of CBZ was studied,and the results showed that the inhibitory effect was more significant with the increase of ion concentration.Low concentration promoted the photocatalysis of CBZ.However,CBZ degradation increased slowly and even was inhibited while continue increasing the NO₃^-concentration to 20 mg/L.The work has effectively revealed the influence of the actual water quality parameters on the photocatalytic oxidation degradation of CBZ,and provides a theoretical foundation for the photolysis of PhACs in water.It also has theoretical guidence in practical application for the photocatalytic oxidation of refractory organics in aquatic environment.