富里酸改性FeMnNi-LDH复合材料对水中砷镉的吸附性能与机制  

Adsorption Characteristics of Arsenic and Cadmium by FeMnNi-LDH Composite Modified by Fulvic Acid and Its Mechanisms

作　　者：何雅馨 柯心怡 魏世强[1,2] 蒋珍茂[1,2] HE Ya-xin;KE Xin-yi;WEI Shi-qiang;JIANG Zhen-mao(College of Resources and Environment,Southwest University,Chongqing 400715,China;Chongqing Key Laboratory of Agricultural Resources and Environment Research,Chongqing 400715,China)

机构地区：[1]西南大学资源环境学院,重庆400715 [2]重庆市农业资源与环境研究重点实验室,重庆400715

出　　处：《环境科学》2023年第5期2646-2660,共15页Environmental Science

基　　金：国家自然科学基金项目(42177012);重庆市大学生创新创业训练计划项目(S202110635221)。

摘　　要：水体中的As(Ⅲ)和Cd(Ⅱ)重金属离子具有潜在的毒性,且能通过食物链等方式转移富集进入人体,进而威胁人体健康.选用富里酸(FA)作为铁锰镍层状双氢氧化物(FeMnNi-LDH)的修饰物,采用共沉淀法制备出能够同时吸附As(Ⅲ)和Cd(Ⅱ)阴阳离子的稳定层状复合材料(FA@FeMnNi-LDH),主要提升了其对Cd(Ⅱ)的吸附容量.利用XRD、TEM、FT-IR和XPS等技术对其结构进行表征,并探讨其对水体中As(Ⅲ)和Cd(Ⅱ)的吸附去除能力和机制.结果表明,经筛选出的具有结构稳定和最大FA负载率、且达到最优吸附性能的复合材料有层状双氢氧化物的典型特征峰.复合材料对As(Ⅲ)和Cd(Ⅱ)的吸附动力学符合准二级动力学模型,等温吸附曲线符合Langmuir模型,25℃时最大吸附量分别为249.60 mg·g^(-1)和156.50 mg·g^(-1).该复合材料在pH为2~7和4~7范围内,分别对As(Ⅲ)和Cd(Ⅱ)有较好的吸附效果.水中共存的常见阴离子对As(Ⅲ)的竞争吸附影响大小顺序为:PO^(3-)_(4)>CO_(2-)^(3)>NO_(3)^(-),常见阳离子对Cd(Ⅱ)的竞争吸附影响大小顺序为:Pb^(2+)>Cu^(2+)>K^(+),复合材料对As(Ⅲ)和Cd(Ⅱ)的吸附量均随着竞争离子浓度的增加而减少.复合材料对As(Ⅲ)的吸附机制主要为LDH层间离子交换,对Cd(Ⅱ)的吸附机制主要为负载的FA配位络合.综上,制备出的FA@FeMnNi-LDH复合材料对水中As(Ⅲ)和Cd(Ⅱ)复合体系的吸附去除和毒性控制具有良好的应用前景.Toxic As(Ⅲ)and Cd(Ⅱ)ions in water can be transferred and enriched into human bodies through the food chain,causing serious health damage at excessive levels.In this study,fulvic acid(FA)was selected as the modifier of iron-manganese-nickel layered double hydroxide(FeMnNi-LDH),and a stable layered composite(FA@FeMnNi-LDH)was prepared using the co-precipitation method,which could adsorb As(Ⅲ)anions and Cd(Ⅱ)cations simultaneously,especially with the higher adsorption capacity of the cation Cd(Ⅱ).Its structure was characterized by XRD,TEM,FT-IR,and XPS,and the adsorption capacity and mechanisms of As(Ⅲ)and Cd(Ⅱ)in water by the composite were also investigated.The results showed that with typical characteristic peaks of layered double hydroxides,the synthesized composite possessed a stable structure,maximum FA loading capacity,and optimal adsorption performance.The adsorption kinetics of As(Ⅲ)and Cd(Ⅱ)conformed to the pseudo-second-order kinetic model,and the adsorption isotherms well-followed the Langmuir model,with the maximum adsorption capacity at 25℃being 249.60 mg·g^(-1)for As(Ⅲ)and 156.50 mg·g^(-1)for Cd(Ⅱ),respectively.The composite exhibited a good adsorption performance on As(Ⅲ)and Cd(Ⅱ)in the range of pH 2-7 and pH 4-7,respectively.The competitive adsorption effect of co-existed anions on As(Ⅲ)showed a sequence of PO^(3-)_(4)>CO_(2-)^(3)>NO_(3)^(-),and that of co-existed cations on Cd(Ⅱ)was Pb^(2+)>Cu^(2+)>K^(+).The adsorption capacity of As(Ⅲ)and Cd(Ⅱ)decreased with the increase in the concentration of competing ions.The main adsorption mechanism for As(Ⅲ)was ion-exchange occurring in the interlayers of LDH,and that for Cd(Ⅱ)was coordination complexation occurring with the loaded FA,respectively.In conclusion,the prepared FA@FeMnNi-LDH composite material posed a good application prospect for adsorption removal of As(Ⅲ)and Cd(Ⅱ)in water and their toxicity control.

关 键 词：层状双金属氢氧化物(LDH) 富里酸(FA) 改性 砷镉复合污染 吸附机制 

分 类 号：X703.1[环境科学与工程—环境工程]