【作者】 高海霞；

【导师】 王晓晶；

【作者基本信息】 内蒙古大学 ， 化学， 2023， 硕士

【摘要】 吡虫啉因毒性低、杀虫效果好而被广泛用于田间农作物害虫的防治,但在农业中频繁使用会造成环境问题——水体污染。因此需要开发消除水环境中残留吡虫啉杀虫剂的工艺。双金属硫化物光催化降解处理废水有机污染物是一种有效的去除水环境中的残留农药的方法。其中硫化锌镉(Zn_xCd_1-xS)的直接带隙能带间隔较小,可通过可见光照射激活光响应。本论文将Zn_0.5Cd_0.5S选为主要的催化剂,通过元素掺杂、形成二元复合物对其进行改性以进一步提高光催化降解吡虫啉的活性和稳定性。本论文的研究内容主要为以下几个部分:1.本研究通过沉淀共水热法制备了可调带隙的Zn_xCd_1-xS纳米光催化剂。通过XRD、SEM、XPS和DRS等对催化剂的光电化学性质进行了表征。在可见光照射下对杀虫剂吡虫啉（IMD）的降解进行评估,其中Zn_0.5Cd_0.5S催化剂活性最好。经过6 h,10 mg·L^-1 IMD被降解了75%左右,近一步研究了环境因素如光辐射时间、p H和农药浓度等对IMD降解性能的影响,基于自由基捕获实验分析出h⁺和·O₂^-是Zn_0.5Cd_0.5S降解IMD的活性物质。2.使用简单的沉淀溶剂热技术制备了N-Zn_0.5Cd_0.5S（N-ZCS）光催化剂,其具有出色的光活性,可在可见光源下从废水中有效去除有毒的吡虫啉农药。使用XRD、UV-Vis DRS、SEM、EDX、TEM和BET比表面积对制备的复合材料进行表征。SEM证实,掺杂N后对样品的形貌无影响,电化学阻抗以及光电流的测定结果表明光生电子和空穴的分离更高,光催化性能得到改善。光催化活性结果表明,N-ZCS-3的降解效率在6 h内为92.6%,明显优于Zn_0.5Cd_0.5S。机理研究表明,催化剂N-ZCS-3降解IMD是通过光激活催化剂产生的h⁺和·O₂^-实现的,可有效地将IMD分解为CO₂、H₂O、无机离子和更简单的小分子。3.采用简单的原位法合成了高稳定性的N-Zn_0.5Cd_0.5S/BN二元复合光催化剂。使用XRD、SEM、TEM、FTIR和XPS技术进行分析,考察了合成的纳米粒子在可见光下对IMD杀虫剂的光催化活性及循环稳定性,结果表明其稳定性明显优于NZCS,四次循环实验后仍能达到74%左右的降解活性。通过自由基捕获实验,BET、PEC、EIS、UV-Vis DRS等表征手段分析了复合催化剂具有高活性和高稳定性的原因。结果表明超氧自由基（·O₂^-）、空穴（h⁺）的清除使复合材料对吡虫啉的去除明显下降,证明·O₂^-和h⁺是吡虫啉降解的活性基团,复合相催化剂的瞬时光电流增强、电化学阻抗降低,这可能是N-Zn_0.5Cd_0.5S/BN稳定性提高的主要因素。N-Zn_0.5Cd_0.5S/BN是一种很有前途的可见光活性光催化剂,这为催化剂稳定性的提升提供了思路。更多还原

【Abstract】 Imidacloprid is widely used to control crop pests because of its low toxicity and good insecticidal effect,however,its frequent use in agriculture can cause environmental problems-water pollution.Therefore,there is a need to develop techenology to eliminate residual imidacloprid insecticide from the aqueous environment.The photocatalytic degradation of organic pollutants by bimetallic sulfide in wastewater is an effective method to remove residual pesticide in water environment.Cadmium zinc sulfide(Zn_xCd_1-xS)has a small direct band gap energy,which can activate the light response through visible light irradiation.In this thesis,Zn_0.5Cd_0.5S was selected as the main catalyst,which was modified by element doping and forming a binary complex to further improve the activity and stability of photocatalytic degradation of imidacloprid.The research for this thesis is in the following sections:1.In this study,Zn_xCd_1-xS nanoparticle photocatalyst with tunable band gap was prepared by hydrothermal deposition.The photochemical properties of the catalysts were characterized by XRD,SEM,XPS and DRS.Their photocatalytic activity was evaluated by degradation of aqueous insecticide imidacloprid（IMD）under visible light radiation,in which,Zn_0.5Cd_0.5S catalysts shows the best activity.After 6 h,10 mg·L^-1IMD was degraded by about 75%.The effects of environmental factors such as light radiation time,p H and pesticide concentration on the degradation performance of IMD were further studied.Based on the free radical capture experiment,h⁺and·O₂^-were identified as the active substances for degradation of IMD by Zn_0.5Cd_0.5S.2.N-Zn_0.5Cd_0.5S（N-ZCS）photocatalysts were prepared using a simple precipitation solvothermal technique.It has excellent photoactivity and can effectively remove toxic imidacloprid pesticides from wastewater under visible light source.The prepared composites were characterized using XRD,UV-Vis-DRS,SEM,EDX,TEM and BET specific surface area.SEM confirmed that doping N has no effect on the morphology of the samples,and the results of electrochemical impedance as well as photocurrent measurements indicate the more excellent separation of photoelectrons and holes and the improved photocatalytic performance are achieved.The results of photocatalytic activity show that the degradation efficiency of N-ZCS-3 within 6 h is92.6%,which is significantly better than that of Zn_0.5Cd_0.5S.The mechanism studies show that the degradation of IMD by N-ZCS-3 catalyst is achieved by photoactivation of h⁺and·O₂^-produced by the catalyst,which can effectively decompose IMD into CO₂,H₂O,inorganic ions,and simpler molecules.3.N-Zn_0.5Cd_0.5S/BN binary photocatalyst with high stability was synthesized by a simple in-situ method.XRD,SEM,TEM,FT-IR and XPS were used for characterize.The photocatalytic activity and cycle stability of the synthesized nanoparticles against IMD insecticide under visible light were investigated.The results show that the stability of the nanoparticles is significantly better than that of N-Zn_0.5Cd_0.5S,and the degradation activity is still about 74%after four cycles of experiments.The reasons for the high activity and stability of the composite catalyst were analyzed by free radical capture experiments,BET,PEC,EIS,UV-Vis-DRS and other characterization methods.The results show that the removal of imidacloprid by superoxide free radical（·O₂^-）and hole（h⁺）decreased significantly,which proves that·O₂^-and h⁺are the active groups of imidacloprid degradation.The improved stability of N-Zn_0.5Cd_0.5S/BN were confirmed by instantaneous photocurrent enhancement and electrochemical impedance reduction.N-Zn_0.5Cd_0.5S/BN is a promising photocatalyst with visible light activity,which provides a way to improve the stability of catalysts.更多还原