Research On The Photocatalytic Degradation Of Carbamazepine In The Water Using BiOCl/SiO₂/Fe₃O₄ Composites

As a new pollutant,Pharmaceuticals and Personal Care Products?PPCPs?has become one of the hotspots and difficulties in the research of environmental water pollution management.Carbamazepine?CBZ?is a typical PPCPs,and it is difficult to be completely removed in most of the commonly used wastewater treatment processes,and the amount of CBZ in environmental water bodies will continue to increase,It will seriously affect the balance of environmental security and ecosystem;and in the human body,it will continue to be enriched by eating,so that the body produces fever,vomiting and allergies and other reactions,excessive intake of CBZ will also damage the liver and other organs,which has a great harm to health.The study of efficient and energy-saving CBZ removal technology is of great significance for improving water environment quality and protecting aquatic ecosystem.Photocatalysis,as a new advanced oxidation technology,is widely used in the removal of refractory organic matter in water.BiOCI is a new type semiconductor photocatalytic material with excellent photocatalytic performance.It has great application prospect in the treatment of CBZ wastewater.Aiming at the defects of BiOCl,taking the microspheroidal ferric tetroxide Fe₃O₄ as the core,and BiOCl is coated on Fe3O4 to make the catalyst magnetic,and the catalyst was effectively recovered by magnetic separation.Silica dioxide?SiO₂?can effectively shield the dipole interaction between magnetic particles and prevent particle agglomeration.SiO₂ is added as an intermediate layer of the composite catalyst,the photocatalytic performance of BiOCl/SiO₂/Fe₃O₄ was determined by photocatalytic degradation of CBZ under visible light conditions.The main achievements and understanding are as follows:?1?The microsphere magnetic Fe₃O₄ was prepared by hydrothermal method.Ethyl orthosilicate was used as the silicon source and Fe₃O₄ was used as the core in the production of Fe₃O₄/SiO₂.Taking Fe₃O₄/SiO₂ as a carrier,BiOCl/SiO₂/Fe₃O₄ composite catalyst was prepared by hydrothermal preparation of BiOCl.Scanning electron microscopy?SEM?,X-ray diffraction?XRD?,Ultraviolet-visible spectroscopy?UV-VIS?,X-ray photoelectron spectroscopy?XPS?and other means to characterize the product.The results showed that Fe₃O₄ was encapsulated by a layer of SiO₂ in the composite catalyst,however,the nanosheet BiOCl was uniformly distributed on the surface,the structure was complete and the purity was high.?2?The photocatalytic degradation rate of BiOCl/SiO₂/Fe₃O₄ prepared by hydrothermal method is very high,when the initial concentration of CBZ is 10 mg/L,the pH value is 5,and the dosage of BiOCl/SiO₂/Fe₃O₄ is 0.9 g/L.After 90 minutes of photocatalytic reaction,the degradation rate was 94.5%.When the inorganic anions such as CO₃^2-and SO₄^2-were added,the degradation rate of CBZ by BiOCl/SiO₂/Fe₃O₄was significantly inhibited,and the addition of inorganic cations also inhibited the degradation of CBZ.The identification of active species in photocatalytic reactions shows that photogenerated holes?h⁺?are the main active species in the degradation process of CBZ.Comparing the photocatalytic activity of BiOCl/SiO₂/Fe₃O₄ with BiOCl,the results show that the catalytic activity of BiOCl/SiO₂/Fe₃O₄ is far greater than that of BiOCl.?3?The effect of photocatalytic degradation of CBZ simulated wastewater by BiOCl/SiO₂/Fe₃O₄ on the degradation rate of the simulated wastewater of BiOCl/SiO₂/Fe₃O₄ was studied from the orthogonal experiment:the catalyst dosage>initial pH>initial concentration.The optimal degradation conditions were as follows:initial concentration 2 mg/L,initial pH value 5,catalyst dosage 0.9 g/L.?4?Photocatalytic degradation of 110 mg/L CBZ wastewater with 0.99 g BiOCl/SiO₂/Fe₃O₄ was performed.The degradation rate was 79.7%after 90 minute photocatalytic reaction.The same amount of catalyst and equivalent CBZ concentration were obtained in the laboratory environment,and the degradation rate has declined.The intermediate products in the process of photocatalytic degradation of CBZ were measured by high performance liquid chromatography mass spectrometry,and three degradation pathways of CBZ were deduced by ion chromatograms.?5?The magnetic recycle performance of BiOCl/SiO₂/Fe₃O₄ was examined with a magnet,the result showed that the composite catalyst has an obvious magnetic property.After four photocatalytic degradation experiments,the degradation rate of the catalyst to CBZ still reached 79.63%,indicating that the stability of BiOCl/SiO₂/Fe₃O₄ is good,easy to recycle and can be reused for many times.