Photocatalytic Degradation Of Trace Carbamazepine By ZnIn₂S₄/g-C₃N₄ In Real River Water

With the progress of science and technology in China,the types of medicines are becoming increasingly abundant.New medicines provide convenience and guarantee for human life,but they also pose a threat to environmental and ecological security.Many pharmaceutical active substances are discharged and abandoned,which would enter different water environment and harm the ecosystem,damage human health through enrichment in the food chain,then bring unpredictable impact.Therefore,the removal of pharmaceutical active compounds?PhACs?entering the environment has become one of the critical issues in the field of environment.Photocatalytic oxidation is a cost-effective technology for the degradation of PhACs,which has the characteristics of mild reaction conditions,small secondary pollution and low operation cost.Thus,it is of great significance to develop a low-energy photocatalytic technology for the degradation of typical pharmaceutical substances in order to protect the ecological environment and eliminate trace drug pollution in the water environment.Most of the studies on the degradation of PhACs used pure water samples,but less about the degradation mechanism in real water body.Therefore,iodine lamp and sunlight were used as reaction light source in this study,and carbamazepine?CBZ?,as a typical representative of PhACs,was used as the target.The effects of solid suspension?SS?,inorganic salt?IS?ion and dissolved organic matter?DOM?in real river water of the Chanhe River and the Bahe River water on the photocatalytic degradation of CBZ were investigated.At the same time,as powder catalysts are difficult to apply in actual water bodies,the supported catalyst was prepared in this paper and applied to degrade CBZ in simulated actual flowing water bodies under solar irradiation,and the effects of flow were analyzed simultaneously.The research results are summarized as follows:?1?UV-Vis DRS,Photocurrent Test,XRD,SEM and BET analysis showed that the photocatalytic activity of ZnIn₂S₄/g-C₃N₄ with 20:1 ratio was stronger than that of pure ZnIn₂S₄.The heterojunction formed by ZnIn₂S₄ and g-C₃N₄accelerated the separation of electron-hole pairs and inhibited their recombination.The increase of pores and specific surface area of ZnIn₂S₄/g-C₃N₄ also increased the activity of the catalyst to a certain extent.?2?The composite photocatalyst ZnIn₂S₄/g-C₃N₄ has photocatalytic activity under iodine lamp irradiation.When the iodine lamp was irradiated for 90min,CBZ with 100?g/L of initial concentration in the Chanhe river sample was completely degraded by 75 mg/L 20:1 ZnIn₂S₄/g-C₃N₄.20:1 ZnIn₂S₄/g-C₃N₄ with125mg/L dosage was the optimal composite ratio and dosage under 300 min of solar irradiation.Three water quality parameters,SS,IS and DOM in two kinds of actual water samples?from the Chanhe River and the Bahe River respectively?had different degrees of inhibition on the photocatalytic degradation of CBZ.The photocatalytic degradation of CBZ in river water followed the pseudo first-order kinetics.The influence order of river water quality parameters on the catalyst activity was DOM>IS>SS,and the photocatalytic rate constant of CBZ in filtered river water was 13 times higher than that of raw water.The CBZ of100?g/L was completely degraded at the catalyst dosage of 125mg/L and 240 min of solar irradiation.?3?The degradation of CBZ under solar irradiation was slower than that of iodine lamp.The main reason is that the absorbance of ZnIn₂S₄/g-C₃N₄ catalyst for different wavelengths of light source is different.In addition,the light source of the iodine lamp is close to the reactant and the light intensity is stable,and the sunlight intensity is unstable and weaker with the time gone.?4?The 0.5%loading rate of ZnIn₂S₄/g-C₃N₄/Pumice had the best degradation efficiency for 800mL of 100?g/LCBZ water sample,which has the advantages of easy recovery and strong water resistance.Under 480 min of solar irradiation,5mL/min of flow rate and 4 times cycle,the degradation and mineralization rates of CBZ were 86.39%and 43.9%,respectively.In this study,ZnIn₂S₄/g-C₃N₄ was used for photocatalytic degradation of CBZ in real river water under the irradiation of iodine lamp and sunlight separately,and some factors affecting the photocatalytic effect were investigated,which provides a certain reference significance for the thorough removal of toxic and harmful organic compounds in water bodies and the further purification of aqueous environment.And ZnIn₂S₄/g-C₃N₄/Pumice showed a good catalytic activity for CBZ photodegradation in flow water,which provides a reference value for its application in the degradation of trace drugs in actual water environment.