【作者】 王震；

【导师】 杨琦；

【作者基本信息】 中国地质大学(北京) ， 环境科学与工程， 2020， 博士

【摘要】 氯代烃具有极强的毒性,在环境中难以自然降解,因此,氯代烃污染的修复一直是环境工程领域重点关注的问题。本次研究制备了纳米CoFe₂O₄、碳纳米管负载CoFe₂O₄（CNTs-CoFe₂O₄）和氮硫共掺杂石墨烯负载CoFe₂O₄（ns/GO-CoFe₂O₄）三种非均相钴系催化剂,对比研究了三种催化剂活化过一硫酸盐（PMS）对三氯乙烯的降解效果;针对难以氧化降解的四氯化碳,构建了以活化PMS为基础,添加HCOONa作为电子供体的还原体系。主要结论如下所示:（1）催化剂表征结果显示:纳米CoFe₂O₄存在明显的团聚,颗粒粒径在150-200 nm之间,比表面积为12.83 m²/g,CNTs-CoFe₂O₄和ns/GO-CoFe₂O₄改善了团聚问题,减小了颗粒的粒径（50-150 nm）,增大了比表面积（45.68和60.12m²/g）;三种材料呈现典型的尖晶石特征,所有元素在材料中所占比例均与预设值类似。（2）在pH=11时,三种催化剂活化PMS对三氯乙烯降解效果最佳,强酸（pH≤3）和强碱（pH≥13）会抑制降解效果;温度的升高、催化剂投加量和PMS浓度的增加在一定程度促进体系对TCE的降解,然而过多的催化剂投加量和PMS浓度将会对整个反应体系产生负面影响;所有条件下TCE的降解过程可用伪一级动力学拟合。（3）催化剂的催化效果随回用次数的增加出现轻微下降;在中性条件下,CoFe₂O₄中钴离子的溶出量约为0.32 mg/L,CNTs-CoFe₂O₄和ns/GO-CoFe₂O₄中钴溶出量更低（0.21和0.023 mg/L）,酸性条件（pH=3）会略微增大离子的溶出。（4）自由基鉴定显示,·OH和SO₄·^-是三种催化剂活化PMS体系降解TCE的主要活性物质,其中·OH的贡献率最大。三氯乙烯脱氯过程中有少量中间产物的产生,最终产物为CO₂、H₂O和Cl^-。（5）ns/GO-CoFe₂O₄活化PMS协同HCOONa体系在360 min内对1 mg/L四氯化碳去除率为87.7%。其降解率随温度的升高、催化剂投加量和PMS浓度的增加而增大;HCOONa浓度的增加可在一定范围内促进四氯化碳的降解,过多的HCOONa会产生负面影响;该体系对四氯化碳降解的最佳pH范围是5-9,CO₂·^-是该体系下实现四氯化碳降解的主要活性物质。更多还原

【Abstract】 Chlorinated hydrocarbons were extremely biotoxic and difficult to be degraded naturally.Therefore,the remediation of chlorinated hydrocarbon pollution has always been the key concerns in the field of environmental engineering.In this study,three kinds of heterogeneous cobalt catalysts were prepared:nano CoFe₂O₄,carbon nanotube supported CoFe₂O₄（CNTs-CoFe₂O₄）and nitrogen sulfur co-doped graphene supported CoFe₂O₄（ns/GO-CoFe₂O₄）.The degradation of trichloroethylene by three kinds of catalysts activated peroxymonosulfate（PMS）was compared;for carbon tetrachloride was difficult to be oxidized,a reduction system was built based on activated PMS with HCOONa as electron donor added.The main conclusions were as follows:（1）The results of catalyst characterization showed that the obvious agglomerations occurred among CoFe₂O₄ nanoparticles,the particle size was between150-200 nm,and the specific surface area was 12.83 m²/g.CNTs-CoFe₂O₄ and ns/GO-CoFe₂O₄ could inhibit the agglomeration of particles,reduce the particle size（50-150 nm）and increase the specific surface area（45.68 and 60.12 m²/g）;All of e three materials showed typical spinel characteristics,and the proportions of all elements in the material were similar to the preset value.（2）The highest removal efficiency of trichloroethylene was achieved at initial pH of 11 in activated PMS system while strong acid（pH≤3）and strong alkali（pH≥13）would inhibit the reaction;the degradation of trichloroethylene was promoted by the increase of temperature,catalyst dosage and PMS concentration to a certain extent,but the exceed catalyst dosage and PMS concentration would have a negative impact on the whole reaction system;The degradation process of trichloroethylene could be fitted by pseudo first order kinetics.（3）With the increase of catalyst reuse times,the degradation efficiency of trichloroethylene in activated PMS system decreased;Under neutral conditions,the dissolution of cobalt ions in CoFe₂O₄ was about 0.32 mg/L,the lower dissolutions of cobalt ions appeared in CNTs-CoFe₂O₄ and ns/GO-CoFe₂O₄（0.21 and 0.023 mg/L）;The acidic conditions（pH=3）slightly increased the dissolution of metals.（4）·OH and SO₄·^-were the main active substances in the degradation of trichloroethylene by activated PMS system,of which·OH played a more vital role.During the dechlorination process of trichloroethylene,few intermediate products were produced,and the final products were CO₂,H₂O and Cl^-.（5）The removal efficiency of carbon tetrachloride（1 mg/L）was 87.7%within360 min by ns/GO-CoFe₂O₄ activated PMS in the presence of HCOONa,and the degradation efficiency of carbon tetrachloride increased with the temperature,catalyst dosage and PMS concentration;the increase of HCOONa concentration could promote carbon tetrachloride degradation in a certain range,However excessive HCOONa would inhibit the degradation of carbon tetrachloride;the optimal pH range for carbon tetrachloride degradation is 5-9,and CO₂·^-was the main active substance to degrade carbon tetrachloride in this system.更多还原