Photocatalytic Degradation Of Cabamazepine Under Solar Irradiation And Investigation Of Influencing Factors

With the development of China’s economy and the improvement of personal living standards,medical condition has been greatly improved.Various medicines have brought health and happiness to people and posed a threat to ecological security simultaneously.After usage of a large amount of Pharmaceutical Active Compounds（PhACs）,the residual drugs from excrement and abandonment not only enter a variety of water environments,but also harm the ecosystem,and seriously damage human health through enrichment in the food chain.Photocatalytic oxidation is a cost-effective technique for degrading PhACs,which has the characteristics of mild reaction conditions,low secondary pollution and low operating cost.Therefore,it is of great significance to carry out research on the characteristics of the degradation of typical pharmaceutical substances by a low-energy photocatalytic technology.At present,most researches of photocatalytic degradation of PhACs in water are mainly carried out in the laboratory to analyze the relevant influencing factors using artificial light sources and artificial water distribution.However,there are few studies on photocatalytic degradation of PhACs in actual water.Therefore,sunlight was selected as the reaction light source,and CBZ,a representative of typical PhACs,which is frequently detected in water,was used as the target compound of photocatalytic reaction to investigate the influence of suspended solids（SS）,several common inorganic salts（IS）ions and dissolved organic matter（DOM,represented by humic acid）on its photocatalytic degradation.The research results obtained are listed as follows:（1）The composite ZnIn₂S₄/TiO₂ catalyst had certain photocatalytic activity under sunlight.CBZ with an initial concentration of 100μg/L in the Bahe River and the Chanhe River water was completely degraded under a catalyst dosage of 75 mg/L and solar irradiation of 240 min.And the catalyst was characterized by UV-visible diffuse reflectance spectroscopy,energy dispersive X-ray（EDX）spectroscopy and X-ray photoelectron spectroscopy.The results showed that the TiO₂ composite promoted the response of the catalyst to ultraviolet light,but the response to visible light was reduced.The EDX characterization suggested that the proportion of Zn in the composite catalyst increased compared with the single catalyst ZnIn₂S₄,and the proportions of S,Zn,In return to normal value;（2）Under the illumination of sunlight,the three water quality parameters of SS,IS and DOM in the two actual water samples（taken from the Bahe river and the Chanhe river）had different degrees of inhibition on the photocatalytic degradation of CBZ,and the photocatalytic degradation of CBZ in water followed pseudo first-order reaction kinetics.After removing DOM,SS and IS in water,the rate constant of the Chanhe River water sample increased from 0.0015min^-1 to 0.0100min^-1,and the rate constant of the Bahe River water sample increased from 0.0008min^-1 to 0.0182min^-1.The influential degree was DOM≈IS>>SS and the removal efficiency of CBZ in the Bahe River sample was higher than that of the Chanhe River.After five times of repeated use of the catalyst,the removal efficiency of CBZ was reduced by 14%.Most of CBZ was degraded by visible light and ultraviolet effect was negligible.（3）As for direct photolysis,low concentrations（10mg/L,30mg/L,50mg/L）of Cl^-in the Bahe river and the Chanhe river promoted the degradation of carbamazepine.At higher concentrations（70mg/L,90mg/L）,the reaction would be inhibited.Also,Cl^-inhibited photocatalytic reaction.With the concentration of NO₃^-increased from 2mg/L to 8mg/L,the promoting effect gradually decreased.The greater the concentration of SO₄^2-,NO₃^-and humic acid,the more significant inhibitory effect on CBZ photolysis.When the chloride ion concentration was 50mg/L and 90mg/L,the addition of isopropanol and potassium iodide changed the removal rate of CBZ from 8%to 11%and 42%to 26%.When the nitrate concentration was 6 mg/L and 10 mg/L,isopropanol and potassium iodide were added,and the removal rate of CBZ altered from 17%to69%and 84%to 65%.The preliminary and effective exploration on the catalytic degradation of CBZ has been carried out in river water under sunlight,and investigated some influencing factors affecting photocatalytic effect,which provided a theoretical basis for photocatalytic removal of PhACs in water environment such as surface water and groundwater.It also had certain reference significance for completely removing toxic and harmful organic matter in water and further deep purification of water.