焙烧态水滑石吸附水中钒酸根的研究

Study on Removal of Vanadate from Aqueous Solution by Calcined Layered Double Hydroxide

采用共沉淀法合成了Mg/Al物质的量比为2∶1的水滑石(LDH),773K煅烧得到其煅烧产物(CLDH),研究了CLDH对钒酸根的吸附性能,分别考察了吸附剂用量、钒酸根浓度、吸附时间和温度等因素对钒酸根吸附效果的影响,并探讨了吸附热力学。结果表明,CLDH对钒酸根有很强的吸附能力,在293～313K温度范围内,CLDH的最大吸附量随着温度的升高而逐渐增大(79.8～92.9mg/g),吸附等温线很好地符合Langmuir方程(R2>0.999),吸附自由能(ΔG0)为-2.47～-3.81kJ/mol,是自发的物理吸附过程;CLDH吸附钒酸根为熵增过程,熵变为67.23J/(mol·K)。

Mg/Al layered double hydroxide（LDH） with Mg（ Ⅱ） ： Al（Ⅲ） molar ratio of 2 ： 1 was synthesized by co-precipitation method and its calcined product（CLDH） was prepared by heating LDH at 773K. Experiments were carried out as a function of adsorbent dosage, initial concentration of solution, contact time and temperature, and dis- cussed the thermodynamics to study the adsorption property. The results indicate that the CLDH have strong adsorp- tion ability of vanadate. Isotherms for vanadate adsorption by CLDH fit the langmuir model with good values of the correlation coefficient （R2〉0. 999）. In 293~313K temperature range, maximum uptake capacity increases with the rise of temperature （79.8~92.9mg/g）, Gibbs＇ free energy change in adsorption is --2.47%--3.81kJ/mol, sugges- ting that is a spontaneous physical adsorption process, vanadate adsorption is entropy increase process, and its entropy change is 67. 23J/（mol ·K）.