Preparation Of Calcium Tungsten Based Catalyst And Its Soncatalyoic Degradation Of Organic Wastewater

In recent years,the industrial wastewater produced by the massive use of antibiotics and organic dyes has more and more serious impact on the environment.Therefore,how to properly treat this kind of wastewater has attracted much attention.Antibiotic wastewater and organic dye wastewater are both difficult to treat as for industrial wastewater.If discharged into the water environment,it will cause serious harm to the ecological balance and human health.The previous researches indicate that the semiconductor acoustic catalysis technology has the advantages of mild reaction conditions,green,pollution-free and complete purification,which is especially suitable for the treatment of antibiotic and organic dye wastewater.Calcium tungstate（Ca WO₄）,which has high stability,non-toxicity,high charge transfer and separation efficiency,is considered to be a good acoustic catalyst and has potential applications in the field of wastewater monitoring and environmental purification.The application of Ca WO₄ based catalyst in sonocatalytic degradation of wastewater was studied in this paper.Firstly,Ca WO₄ semiconductor material was synthesized by the hydrothermal method,and the p-n heterojunction between Ca WO₄ and（Ag₂O）,was constructed with Ca WO₄ as substrate（Ag₂O molar ratio was 1%,5%,10%,15%and 20%,respectively）.Ag₂O/Ca WO₄was characterized by X-ray diffractometer（XRD）,scanning electron microscope（SEM）,X-ray photoelectron spectroscopy（XPS）and energy dispersive X-ray spectrometer（EDX）.The prepared Ag₂O/Ca WO₄ heterojunction was used as acoustic catalyst for the degradation of ofloxacin（OFL）.The sonocatalytic activity of Ag₂O/Ca WO₄ was investigated by the change of OFL solution absorbance.When the molar ratio of Ag₂O/Ca WO₄ is 10%,the addition amount of Ag₂O/Ca WO₄ is 2.5 g/L,the initial concentration of OFL is 10 mg/L,the solution p H is 6,the addition amount of K₂S₂O₈is 0.25 mmol/L,and the ultrasonic time is 120 min,the OFL solution obtains the highest degradation ratio.In addition,the effects of different scavengers on the degradation ratio of OFL were investigated.The main types of reactive component species（ROS）produced were·OH,·O₂^-and h⁺.The recycling experiment verified that 10%Ag₂O/Ca WO₄ catalyst has good reusability and stability.In addition,the n-n heterojunction between Ca WO₄ and Cu WO₄ was constructed with Ca WO₄ as the substrate to improve the ultrasonic catalytic activity(the molar ratio of Cu²⁺was 5%,10%,15%and 20%,respectively).Cu WO₄/Ca WO₄ was characterized by XRD,SEM,XPS and EDX.The prepared Cu WO₄/Ca WO₄ heterojunction was used as an acoustic catalyst for the degradation of golden orangeⅡ（AO7）.When the molar ratio of Cu WO₄ is15%,the addition amount of Cu WO₄/Ca WO₄ is 1 g/L,the addition amount of K₂S₂O₈ is 1mmol/L,the initial concentration of AO7 solution is 5 mg/L,the solution p H is 5,the ultrasonic power is 200 W and the ultrasonic time is 120 min,the degradation ratio of AO7solution is high.In addition,the effects of different scavengers on the degradation ratio of OFL were explored.The results showed that the main ROS produced were·OH and h⁺.The recycling experiment indicated that the 15%Cu WO₄/Ca WO₄ has good reusability and stability.The above researches show that the construction of Ca WO₄ based composite can effectively improve the separation of electron-hole（e^--h⁺）pairs in the process of sonocatalytic degradation and significantly enhance its sonocatalytic activity.The research results will provide a theoretical basis for the preparation and application of Ca WO₄ based sonocatalyst.