摘要
层状双氢氧化物(Layered double hydroxide,LDH)是土壤中常见的矿物组分,而Na^+、K^+、Ca^2+和Mg^2+更是土壤溶液中的主要阳离子,它们共存条件下对重金属污染物在土壤中的行为过程影响如何是一个需要探讨的科学问题。通过批量静态吸附实验、动力学实验和室内土柱迁移实验,研究不同阳离子与Mg-Al-CO3 LDH共存时对重金属Cd在土壤中吸附迁移的影响。运用伪二级动力学模型、Elovich模型及内扩散模型对吸附动力学数据进行拟合,并对Mg-Al-CO3 LDH吸附Cd前后的样品进行红外光谱分析及X射线衍射分析,以探究其吸附机理。结果表明:Mg-Al-CO3 LDH的存在使土壤pH升高,且Mg-Al-CO3 LDH含有大量CO3^2-,使得土壤对Cd的吸附能力增强;阳离子类型不同时,无论土壤中是否含有LDH,其对Cd的吸附量均表现为阳离子价态越高,吸附量越小。伪二级动力学模型拟合效果非常好,R2均接近于1,说明土壤对Cd的吸附能力与吸附位点有关;内扩散模型拟合结果揭示土壤对Cd^2+吸附的速率受液膜扩散、颗粒间扩散、化学反应等综合作用的控制。不同阳离子类型对Cd在土壤中吸附迁移的影响不同,Cd迁移能力表现为随背景阳离子价态升高迁移能力增强;Mg-Al-CO3 LDH的存在抑制了Cd的迁移。红外光谱及X射线衍射分析表明,Mg-Al-CO3 LDH对Cd2+的吸附机理主要为Cd^2+与Mg-Al-CO3 LDH上的CO3^2-反应生成CdCO3沉淀。Mg-Al-CO3 LDH对不同阳离子的吸附机制不同,影响着重金属Cd在土壤中的吸附迁移过程。
Although Na^+,K^+,Ca^2+and Mg^2+are the main cations in soil water,coexisting with heavy metal pollutants in soil,Layered Double Hydroxide(LDH)is a common mineral component in soil.How Na^+,K^+,Ca^2+and Mg^2+affect the behavioral processes of heavy metal pollutants in a soil under coexistence conditions is a scientific issue that needs further exploration.By using batch static adsorption experiments,adsorption kinetics experiments and soil column migration experiments,the adsorption and transport process of cadmium in soil was examined when different cation species were used for LDH.The pseudo-second-order kinetic model,the Elovich model and the intra-particle diffusion model were used to examine differences in our experimental data;all samples were analyzed using infrared spectroscopy and Xray diffraction analysis to explore adsorption mechanisms.Results show that:The presence of Mg-Al-CO3 LDH increased soil pH,and Mg-Al-CO3 LDH contained a large amount of CO3^2-;the adsorption capacity of soil for heavy metal cadmium was also enhanced.When cation species differ,the adsorption capacity of soil for heavy metal cadmium also differs,and the higher the cationic valence is,the smaller is the amount of adsorption.The pseudo-second-order kinetic model fitted the data well,having R2 levels≥0.999.The Elovich model fitted L soil adsorption kinetics better than natural soil,and results from the intra-particle diffusion model indicated that the rate of soil adsorption to Cd^2+was controlled by the combination of liquid membrane diffusion,interparticle diffusion and chemical reaction.Different cation types had different effects on the adsorption of Cd2+by soils,and the migration of Cd^2+increased with the valence of background cations;Mg-Al-CO3 LDH could inhibit the migration of Cd2+.Infrared spectroscopy and X-ray diffraction analysis results indicate that the adsorption mechanism of Cd^2+by Mg-Al-CO3 LDH is predominantly Cd^2+reacting with CO3^2-to form CdCO3 precipitate.Results from this study show that the adsorption m
作者
王玉环
林青
徐绍辉
WANG Yu-huan;LIN Qing;XU Shao-hui(College of Environmental Science and Engineering,Qingdao University,Qingdao 266071,China)
出处
《农业环境科学学报》
CAS
CSCD
北大核心
2019年第9期2129-2137,共9页
Journal of Agro-Environment Science
基金
国家自然科学基金项目(41571214,41807010)~~
关键词
土壤
层状双氢氧化物
CD
吸附
迁移
soil
Layered Double Hydroxide
cadmium
adsorption
migration
