镁铝层状双金属氢氧化物及其煅烧产物对水体W(Ⅵ)的吸附特征与机制  

Adsorption characteristics and mechanism of W(Ⅵ)from aqueous solution using MgAl layered double hydroxide and its calcined product

作　　者：袁秀娟 曾萍 任嗣利 罗武辉 YUAN Xiu-juan;ZENG Ping;REN Si-li;LUO Wu-hui(Jiangxi Key Laboratory of Mining&Metallurgy Environmental Pollution Control,Ganzhou 341000,China;School of Resources and Environmental Engineering,Jiangxi University of Science and Technology,Ganzhou 341000,China;Guangdong Fuyuan Rare Earth Co.Ltd.,Meizhou 514000,China;Jiangxi Academy of Eco-Environmental Sciences and Planning,Nanchang 330039,China)

机构地区：[1]江西省矿冶环境污染控制重点实验室,江西赣州341000 [2]江西理工大学资源与环境工程学院,江西赣州341000 [3]广东省富远稀土有限公司,广东梅州514000 [4]江西省生态环境科学研究与规划院,江西南昌330039

出　　处：《中国环境科学》2023年第3期1166-1176,共11页China Environmental Science

基　　金：江西省自然科学基金资助项目(20212BAB203016);江西省博士后科研项目择优资助(2018KY32);江西理工大学清江青年英才支持计划(JXUSTQJYX2020006)。

摘　　要：采用微波陈化法制备了物质的量比为2:1的硝酸型镁铝层状双金属氢氧化物(LDH),系统地研究了LDH及其煅烧产物(CLDH)对W(Ⅵ)的吸附特征,并通过对吸附W(Ⅵ)前后LDH和CLDH的结构进行表征阐明相关吸附机制.LDH和CLDH对W(Ⅵ)的吸附动力学更符合拟二级动力学模型,表明化学吸附是决定吸附速率的关键.LDH和CLDH对W(Ⅵ)具有较高的亲和性,最大吸附量分别达176.0,124.5mg/g,远高于同类LDH.LDH吸附W(Ⅵ)的最佳pH值范围为4.0~10.0,酸性条件有利于CLDH吸附W(Ⅵ).综合对比,LDH具有更高的吸附容量、更快的吸附速率以及更弱的水质影响(Mg、Al溶出低,pH变化小),更适宜用于W(Ⅵ)吸附.LDH吸附W(Ⅵ)的主要机制包括离子交换、外层络合和内层络合,而CLDH对W(Ⅵ)的吸附机制还包括重构层状结构时仲钨酸盐(W_(7)O_(24)^(6-))的插层作用.以上结果表明,采用微波法合成LDH和CLDH均可高效地吸附污染水体的W(Ⅵ),是一类性能优越的W(Ⅵ)吸附材料.A nitrate-type layered double hydroxide(LDH)with the Mg/Al molar ratio of 2:1 was prepared via microwave aging method.The adsorption characteristics of W(Ⅵ)using LDH and its calcined product(CLDH)were systematically studied,and the involved mechanisms were elucidated through the structural characterization of LDH and CLDH before and after adsorption.The adsorption kinetics of LDH and CLDH to W(Ⅵ)was well fitted with the pseudo-second order model,indicating that chemisorption was the key process determining the adsorption rate.Both LDH and CLDH showed high affinity to W(Ⅵ),showing the maximum uptakes of 176.0 and 124.5mg/g,respectively,which are far higher than the analogous LDH.The optimum pH range for W(Ⅵ)adsorption on LDH was 4.0~10.0,while the acidic condition was conducive to W(Ⅵ)adsorption by CLDH.Compared with CLDH,LDH showed the higher adsorption capacity,faster adsorption rate,and less influences on water qualities(e.g.,less releases of Mg and Al and change of pH),suggesting that the original LDH is more applicable for W(Ⅵ)adsorption.The main mechanisms of W(Ⅵ)adsorption on LDH include ion exchange,outer-sphere complexation,and inner-sphere complexation,while for the case of CLDH,the intercalation of paratungstate(W_(7)O_(24)^(6-))during the reconstruction of layered structure was also involved.The above results indicate that both LDH and CLDH synthesized via the microwave radiation are favorable adsorbents with the superior performance in removal of W(Ⅵ)from the polluted water.

关 键 词：微波 层状双金属氢氧化物 煅烧 钨 吸附 

分 类 号：X703[环境科学与工程—环境工程]