摘要
为了探究和比较两性+阳离子复配修饰膨润土对不同类型重金属离子[Cr(Ⅵ)和Cd^(2+)]的吸附效应及影响机制,采用阳离子型表面修饰剂十二烷基三甲基溴化铵(DTAB或DT)复配修饰两性表面修饰剂十二烷基二甲基甜菜碱(BS-12或BS)修饰膨润土,批处理法研究各复配修饰土样对Cr(Ⅵ)和Cd^(2+)的等温吸附的异同,并对比温度、pH值和离子强度对吸附的影响。结果表明:各复配修饰膨润土对Cr(Ⅵ)和Cd^(2+)的吸附等温线均符合Langmuir模型。供试土样对Cr(Ⅵ)的平衡吸附量呈现BS+150DT(150%CEC的DTAB复配修饰膨润土)>BS+100DT>BS+50DT>BS+25DT>BS>CK(膨润土)的趋势,且最大吸附量(qm)为205.67 mmol·kg-1(BS+150DT)。土样对Cd^(2+)的平衡吸附量表现为BS>CK>BS+25DT>BS+50DT>BS+100DT>BS+150DT,其qm值为232.38 mmol·kg-1(100BS)。10~40℃范围内,CK、BS修饰土对Cr(Ⅵ)吸附量为增温正效应,而BS+DT复配修饰土对Cr(Ⅵ)吸附呈现自发、焓减和熵增的特征;各供试土样对Cd^(2+)的吸附均表现为自发、焓增和熵增的特征。随着pH值的升高,各修饰土样对Cr(Ⅵ)的吸附量均逐渐降低,而对Cd^(2+)的吸附量逐渐增加。离子强度增加不利于供试土样对Cr(Ⅵ)和Cd^(2+)的吸附。BS+DT复配修饰膨润土表面的电荷类型、电荷数量是决定Cr(Ⅵ)和Cd^(2+)吸附差异的主要因素。
In order to compare the discrepancies between Cr（Ⅵ） and Cd^2＋ adsorption on bentonite modified by a mixture of amphoteric modifier, dodecyldimethyl betaine（BS-12）, and cationic modifier, Dodecyltrimethyl ammonium Bromide（DTAB）, batch method was used to study the influence of temperature, ionic strength, pH on discrepancies of adsorption of Cr（Ⅵ）and Cd^2＋ on different modified bentonites,and the thermodynamic properties were studied also. The results showed that：The Langmuir model was suited for adsorption isotherms of Cr（Ⅵ）and Cd^2＋ on different samples. The equilibrium adsorption capacity of Cr（Ⅵ）was ordered by BS＋150DT（BS-12＋150% CEC DTAB）BS＋100DTBS＋50DTBS＋25DTBSCK（unmodified bentonite）and BS＋150DT treatment had the maximum adsorption capacity（qm）205.67 mmol·kg^-1. On the contrary, the sequence of equilibrium adsorption capacity of Cd^2＋was BSCKBS＋25DTBS＋50DTBS＋100DTBS＋150DT, and 100BS（100% CEC BS-12）had maximum Cd^2＋adsorption 232.38 mmol·kg^-1. In the range of 10 ℃ to 40 ℃, the adsorption capacity of Cr（Ⅵ）on CK and BS modified bentonites were increased with increased temperature, while Cr（Ⅵ）adsorption on BS-DT bentonites was a spontaneous process with a decrease in enthalpy and an increase in entropy. The Cd2 ＋adsorption on different samples was a spontaneous process with an increase in enthalpy and an increase in entropy. With an increase of pH, the adsorption capacity of Cr（Ⅵ）decreased gradually, while the adsorption capacity of Cd^2＋increased gradually. High ionic strength was not conducive to adsorption of Cr（Ⅵ）and Cd^2＋. Charge type of BS-DT complex modified bentonite was the crucial factor to difference between Cr（Ⅵ）and Cd^2＋ adsorption.
出处
《农业环境科学学报》
CAS
CSCD
北大核心
2017年第9期1778-1786,共9页
Journal of Agro-Environment Science
基金
国家自然科学基金项目(41271244)
陕西省重点研发计划项目(2017SF-385)~~
