Construction Of Noble Metal@semiconductor Heterojunction Nanophotocatalysts For The Degradation Of Organic Pollutants In Drilling Waste Fluid

In recent years,with the increasing demand of human society for oil,natural gas and other oil and gas resources,the waste liquid generated in the process of oil and gas resource exploitation is also causing more and more serious environmental pollution.These drilling waste fluids generally contain additives such as polyacrylamide,humic acid propanesulfonic acid amide multipolymer RSTF,and maleic anhydride multipolymer TX.These additives have wide pollution area,slow degradation rate,affect dissolved oxygen in water,and have hazards such as high toxicity,high chroma,and high chemical oxygen demand.Therefore,there is an urgent need to develop a treatment technology for organic pollutants in drilling waste fluids.On the one hand,it can solve the problem of recycling water resources at the mining site and reduce the consumption of water resources;On the other hand,it can improve the environmental protection level of the drilling process.In view of the above problems,photocatalytic technology has a wide application range,strong oxidizing ability,high degradation efficiency,and utilizes clean,pollution-free and renewable solar energy,which has the advantages of non-toxicity,stability and reusability.Therefore,we applied photocatalytic technology to the field of degradation of organic pollutants in drilling waste fluids.In terms of the selection of photocatalysts,we prepared noble metal@semiconductor heterojunction nanophotocatalysts to achieve efficient photocatalytic degradation of organic pollutants in drilling waste fluids.In Chapter 2,we first prepared ultrathin 2D BiVO₄ nanosheets with monoclinic phase by the"two-phase method",and then deposited Au nanoparticles on the surface of BiVO₄ by the"photoreduction"method,so as to obtain excellent photoresistance Ultrathin 2D Au@BiVO₄nanosheets for catalytic performance.It can photocatalytically degrade polyacrylamide（HPAM）with high efficiency.We systematically studied the effects of catalyst preparation conditions,catalyst dosage,and initial concentration of HPAM on the photocatalytic degradation performance.The results showed that the initial concentration of HPAM had no effect on the degradation efficiency;Increasing the catalyst dosage will improve the degradation efficiency of HPAM;with the increase of Au loading,the ability of Au@BiVO₄ to generate hydroxyl radicals（·OH）increases first and then weakens.When the amount-to-feed ratio is 1:100,the obtained product has the best photocatalytic degradation effect on HPAM.In addition,we also explored the photocatalytic mechanism of ultrathin 2D Au@BiVO₄ nanosheets.We believe that the photocatalytic performance of ultrathin two-dimensional Au@BiVO₄ nanosheets is mainly due to the fact that Au nanoparticles（Au NPs）can effectively promote the separation of photogenerated electrons and holes at the interface of the heterojunction,inhibit their recombination,and then make the photocatalyst in the light.Under conditions,more hydroxyl radicals（·OH）are generated for the degradation of organic pollutants.In Chapter 3,based on the research results in the previous chapter,we took the drilling waste fluid collected on site as the research object,and selected inexpensive TiO₂ as the raw material to prepare the Au@TiO₂ heterogeneity in batches by a simple"photoreduction"method.The nano-photocatalyst can realize the efficient photocatalytic degradation of organic pollutants in drilling waste fluid.Using this method,we successfully prepared 200 g of Au@TiO₂ heterojunction nanophotocatalysts and loaded them on the surface of polypropylene polyhedral spheres for easy recycling.Finally,we characterized the catalytic performance of Au@TiO₂ heterojunction nanophotocatalysts by COD detection.The research results show that the photocatalytic degradation rate of organic pollutants in 100 mg/L petroleum drilling waste fluid can reach 100%under the irradiation of full spectrum for 90 min;the lower initial concentration of organic pollutants has better degradation effect.As the dosage of photocatalyst increases,the degradation effect of organic pollutants in oil drilling waste fluid increases first and then decreases,and reaches the highest when the catalyst concentration is 1 g/L.The degradation effect of organic pollutants in the waste liquid first increased and then decreased,and reached the highest at 25°C;the initial p H of the oil drilling waste fluid affects its degradation effect,and the degradation of organic pollutants in the oil drilling waste fluid at the initial p H value of 9.60 Most efficient.In addition,our photocatalysts have good repeatability.After being reused 4 times,81.62%of the initial catalytic activity can still be retained.The above research work was completed in cooperation with China National Petroleum Corporation Chuanqing Drilling Engineering Co.,Ltd.Safety,Environmental Protection and Quality Supervision and Inspection Research Institute.The research results are expected to be promoted on drilling platforms.In summary,by constructing a noble metal@semiconductor heterojunction nanostructure,we can effectively promote the separation of photogenerated electrons and holes at the heterojunction interface and inhibit their recombination,thereby realizing the preparation of nanophotocatalysts with excellent photocatalytic performance.Further,we successfully achieved the degradation of organic pollutants in drilling waste fluid collected on site by batch preparation of noble metal@semiconductor heterojunction nanophotocatalysts.