La2O3纳米颗粒对水溶液中As（Ⅲ）的吸附

ADSORPTION OF As（Ⅲ） ON La2O3 NANOPARTICLES IN AQUEOUS SOLUTION

以十六烷基三甲基溴化铵(CTMAB)为表面活性剂,采用共沉淀法制得La2O3纳米颗粒。利用扫描电子显微镜(SEM)、X射线衍射(XRD)和比表面积分析仪(BET)对La2O3纳米颗粒进行分析。采用批实验考察了溶液pH、典型阴离子和离子强度等因素对La2O3纳米颗粒吸附溶液中As(Ⅲ)的影响,并对吸附动力学、吸附等温模型及吸附机理进行研究。结果表明:添加质量分数为0. 2%的CTMAB时制得的La2O3对As(Ⅲ)的吸附效果最好。当溶液pH为5~9时,As(Ⅲ)去除率较高,可达85. 36%。溶液中共存的SO42-和CO32-对As(Ⅲ)的吸附影响较小,而SiO32-和PO43-增加到10 mmol/L时,As(Ⅲ)去除率从85. 36%分别降低至39. 14%和25. 36%。离子强度对As(Ⅲ)的吸附影响较小,表明该吸附过程为内层吸附。La2O3纳米颗粒对As(Ⅲ)的吸附符合伪二级反应动力学和Langmuir吸附等温模型,表明该吸附为单分子层吸附,理论最大吸附量为45. 5 mg/g。La2O3纳米颗粒吸附As(Ⅲ)的机理分析为La2O3表面羟基化后产生的羟基基团La-OH与As(Ⅲ)反应生成单齿或双齿络合物,从而将As(Ⅲ)从水溶液中去除。

La2O3 nanoparticles,using cetrimonium bromide( CTMAB) as the surfactant,were prepared by co-precipitation method and characterized by X-ray diffraction( XRD),scanning electron microscopy( SEM),and N2 adsorption-desorption isotherms( BET). A series of batch experiments were carried out to study the effects of solution pH,coexisting anions and ionic strength on the adsorption of As( Ⅲ) by La2O3 nanoparticles. Adsorption kinetics and adsorption isotherm models were used to simulate the adsorption process and explore the adsorption mechanism. The results showed that La2O3 prepared with 0. 2%CTMAB had a higher adsorption capacity on As( Ⅲ) . The optimum pH range of As( Ⅲ) adsorption was 5 ~ 9. The effect of SO42- and CO32- on the adsorption of As( Ⅲ) was insignificant,while the efficiencies of As( Ⅲ) adsorption were separately decreased to 39. 14% and 25. 36%,when the concentrations of SiO32- and PO43- were increased to 10 mmol/L. The negligible influence of ionic strength on the adsorption indicated that the adsorption was an inner layer adsorption;the adsorption of As( Ⅲ) by La2O3 nanoparticles fitted with the pseudo-secondary reaction kinetics and the Langmuir adsorption isotherm model,demonstrating that the adsorption was a monolayer adsorption. The theoretical maximum adsorption capacity of La2O3 nanoparticles was 45. 5 mg/g. The mechanism for As( Ⅲ) adsorption was as follows: the hydroxyl group La-OH formed by hydroxylation of La2O3 reacted with As( Ⅲ) and generated a monodentate or bidentate complex,which removed As( Ⅲ) from aqueous solution.