蔗渣炭/镁铝双金属氧化物的制备及其吸附As(Ⅴ)的研究

Preparation of bagasse charcoal/Mg-Al layered double oxide and its adsorption study of As(Ⅴ)

采用共沉淀和焙烧法制备蔗渣炭/镁铝双金属氧化物(LDO),研究了pH、吸附时间、初始As(Ⅴ)浓度等因素对其吸附As(Ⅴ)的性能的影响。采用X射线衍射(XRD)、傅立叶红外光谱(FTIR)和扫描电镜(SEM)对蔗渣炭/镁铝双金属氢氧化物(LDH)、吸附As(Ⅴ)前后的蔗渣炭/镁铝LDO进行表征,探讨其吸附As(Ⅴ)的机理。结果表明,蔗渣炭/镁铝LDH具有水滑石层状结构;在pH为3.0~10.0时,蔗渣炭/镁铝LDO对As(Ⅴ)的平衡吸附量较高。准二级动力学模型可用于描述其对As(Ⅴ)的吸附动力学过程,吸附等温线符合Langmuir方程,45℃时,其对As(Ⅴ)的饱和吸附量为26.120mg/g。蔗渣炭/镁铝LDO受共存阴离子影响表现为HPO_4^(2-)>CO_3^(2-)>SO_4^(2-)>Cl^->NO_3^-;材料再生循环利用4次后,对20.0mg/L的As(Ⅴ)的去除率为89.63%。XRD和FTIR分析表明,吸附后AsO_4^(3-)嵌入水滑石层间。

The bagasse charcoal/Mg-Al layered double oxide(LDO)was prepared by co-precipitation and calcination method.The effect of the solution pH,adsorption time and initial As(Ⅴ)concentration on the adsorption performance of As(Ⅴ)onto bagasse charcoal/Mg-Al LDO was discussed.The adsorption mechanism of As(Ⅴ)in aqueous solution was investigated via X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR)as well as scanning electron microscopy(SEM).The results showed that the bagasse charcoal/Mg-Al LDH had a hydrotalcite laminar structure,and the optimal pH for As(Ⅴ)adsorption onto bagasse charcoal/Mg-Al LDO ranged from 3.0 to 10.0.The adsorption kinetics of As(Ⅴ)was described by pseudo-second-order model and the As(Ⅴ)adsorption isotherm was fitted to the Langmuir equation.Moreover,the maximum adsorption capacity of As(Ⅴ)on bagasse charcoal/Mg-Al LDO was 26.120 mg/g at 45℃.The effect of coexisting anions on bagasse charcoal/Mg-Al LDO was HPO 2-4>CO 2-3>SO 2-4>Cl->NO-3.After the adsorbent recycling and reusing for 4 times,the removal efficiency could reach 89.63%when the initial As(Ⅴ)concentration was 20.0 mg/L.The analysis via XRD and FTIR showed that AsO 3-4 was inserted into interlayer structure.