不同类型酸修饰-磁化海泡石对水体Cd(II)的吸附研究

采用无机或有机酸修饰-磁化的方法研制海泡石吸附材料H-Sep(盐酸修饰)、N-Sep(硝酸修饰)、P-Sep(磷酸修饰)和A-Sep(醋酸修饰),并借助SEM、TEM、EDS、BET、FT-IR、VSM及XPS等手段表征分析改性前后海泡石的结构特征.同时,在不同投加量、pH、温度和溶液浓度等因素条件下,考察了酸修饰-磁化海泡石对水体Cd(II)吸附效果的影响.结果表明,改性材料取得最佳吸附效果时的投加量为5g·L^-1,pH为6.5,拟合结果更符合准二级动力学方程和Langmuir等温方程.其中,P-Sep的吸附效果最好,其最大理论吸附量为52.6 mg·g^-1.VSM结果表明,H-Sep、N-Sep和A-Sep是磁化分离效果较好的材料,而P-Sep的磁化分离效果不佳.此外,Na⁺、Cl^-等阴阳离子对酸修饰-磁改性海泡石吸附性能没有太大影响,而重金属离子如Pb(II)、Zn(II)会对其吸附过程产生抑制作用.XPS吸附机理分析表明,酸修饰-磁化改性将新的功能基团引入海泡石结构,极大地提升了吸附性能.

Adsorption of Cd(II) onto different types of acid modified-magnetized sepiolite

The sepiolite adsorbents, namely as H-Sep, N-Sep, P-Sep and A-Sep, were successfully produced by inorganic or organic acid modification and magnetization, and the SEM, TEM, EDS, BET, FT-IR, VSM and XPS were used to characterize the structural characteristics of these adsorbents. The adsorption performance of adsorbents was investigated at different experimental conditions, such as dosage, pH, temperature and initial Cd(II) concentration of solution. The results showed that the optimal dosage of the adsorbents was 5 g·L^-1, while the optimal pH was 6.5 during the adsorption process. Meanwhile, the pseudo-second-order kinetic and the Langmuir model gave the better fits to the adsorption kinetics and isotherms, respectively. Among these adsorbents, P-Sep had the highest maximum theoretical adsorption capacity (52.6 mg·g^-1). Furthermore, VSM showed that H-Sep, N-Sep and A-Sep had the excellent magnetization separation, but weak for P-Sep. In addition, Na⁺, Cl^- and other anions and cations appeared little effect on the adsorption performance. However, other heavy metal ions such as Pb(II) and Zn(II) would inhibit the adsorption behavior. Finally, XPS analysis clearly demonstrated that acid modification and magnetization effectively introduced new functional groups into sepiolite structure, and then greatly improved the adsorption capacities.