十二烷基三甲基溴化铵膨润土处理低浓度U(Ⅵ)废水试验研究

Removal of low concentration U(Ⅵ)in wastewater by dodecyl trimethyl ammonium bromide-modified bentonite

膨润土常被用于放射性核素铀的吸附与固化,但天然膨润土的硅氧结构具有较强的亲水性,导致对污染物的吸附效果较差。本文以DTAB为有机改性剂,膨润土为原料,采用共沉淀方法制备DTAB有机改性膨润土,并进行表征对比分析,并考察pH值、改性膨润土用量、温度、吸附时间、铀废水初始浓度等因素对DTAB有机改性膨润土吸附模拟废水中U(Ⅵ)的影响。得出以下结论:改性后的膨润土孔道扩大,间距扩大,而且增加了大量的疏水官能团,吸附效果得到大幅改善;试验最佳吸附条件为pH值4.0、改性膨润土用量0.1 g(2 g/L)、温度333.15 K、铀废水初始浓度10 mg/L、吸附时间240 min,此条件下铀去除率大于99%;动力学拟合表明,该材料吸附动力学模型符合准二级动力学模型,表明该吸附以化学吸附为主;等温吸附模型拟合表明,该吸附模型更符合Langmuir等温吸附模型,拟合最大吸附量为34.45 mg/g。

Bentonite is oftern used for adsorption and solidification of radionuclide uranium,but the silica structure of natural bentonite has a strong hydrophilicity,leading to a poor adsorption effect on pollutants.In this paper,DTAB organic modified bentonite was prepared by co-precipitation method with DTAB as a modifier and bentonite as raw material.And the effects of pH value,dosage of modified bentonite,temperature,adsorption time and initial concentration of U(Ⅵ)solution on the adsorption of U(Ⅵ)contained in wastewater by DTAB organic modified bentonite were investigated.It is concluded that the adsorption effect of modified bentonite is greatly improved with a wider pore and spacing as well as a large number of hydrophobic functional groups.The experimental results show that the best adsorption effect is achieved at pH 4.0,the modified bentonite dosage of 0.1 g(2 g/L),the temperature of 333.15 K,the initial concentration of U(Ⅵ)-containing wastewateras 10 mg/L and the adsorption time of 240 min,and the U(Ⅵ)removal rate could reach 99.57%under such condition.The kinetics-equation fitting shows that the adsorption model of the material is in accordance with the quasi-secondary kinetic model,indicating that the adsorption is dominated by chemisorption.The isothermal adsorption model fitting shows that the adsorption model is more consistent with the Langmuir isothermal adsorption model,and the fitted maximum adsorption amount is 34.45 mg/g.