磁性柠檬酸膨润土对六价铬吸附性能的研究

Research on Cr(Ⅵ) Adsorption with Magnetic Citric Acid Bentonite

为改善膨润土对Cr(Ⅵ)的吸附性能,并提高其固液分离回收能力,研究构筑了一种壳聚糖修饰的复合磁性吸附材料——磁性柠檬酸膨润土(Magnetic Citric Acid Bentonite,MCAB),并利用SEM、XRD、VSM、FT-IR对改性前后的材料进行表征对比,结果表明壳聚糖中的-NH_2、-OH等功能基团及磁性Fe_3O_4微粒均负载到柠檬酸膨润土(Citric Acid Bentonite,CAB)上。MCAB对Cr(Ⅵ)的吸附性能研究结果显示:相对于CAB,复合后的MCAB吸附性能明显提高,并具有良好的磁分离能力;p H值对Cr(Ⅵ)的吸附影响较大,最佳p H值在2.0~3.0;当吸附剂投加量为1.6 g·L-1、p H值为3.0、Cr(Ⅵ)的初始浓度为10 mg·L^(-1)时,MCAB对Cr(Ⅵ)的去除率高达99%;吸附等温方程和动力学方程的拟合结果分别符合Langmuir吸附等温模型和准二级动力学模型。由于MCAB上修饰的-NH2在酸性条件下易质子化,会增强对Cr(Ⅵ)的静电吸引作用,因此MCAB对Cr(Ⅵ)的吸附去除率得到了明显提高;同时,加磁赋予了CAB快速的固液分离能力。研究表明MCAB对模拟废水中的Cr(Ⅵ)去除效果良好,有望应用于实际废水中Cr(Ⅵ)的去除。

In order to improve Cr（Ⅵ） adsorption and solid-liquid separation of bentonite, a chitosan modified magnetic composite（magnetic citric acid bentonite（MCAB）） was prepared in this study. The structural and morphological properties of MCAB were characterized by SEM, XRD, VSM and FT-IR. The results indicate that citric acid bentonite is modified by magnetic Fe3O4 particles and functional groups（-NH2,-OH） of chitosan. Cr（Ⅵ） adsorption of MCAB were also investigated. Compared with CAB, MCAB shows much better adsorption performance and excellent magnetic separation properties. Cr（Ⅵ） adsorption is highly p H-dependent and the optimum p H is 2.0～3.0. Up to 99% Cr（Ⅵ） removal can be achieved under conditions of 1.6 g·L^-1 adsorbent, p H 3.0 and 10 mg×L^-1 Cr（Ⅵ） solution. Moreover, Cr（Ⅵ） adsorption isotherms and kinetics follow Langmuir model and pseudo-second-order model, respectively.-NH2 of MCAB can be easily protonated under acidic conditions which enhances electrostatic attraction of Cr（Ⅵ） and thus improves Cr（Ⅵ） adsorption performance of MCAB. In addition, the rapid magnetic separation ability of MCAB is achieved by modifying CAB with nano-Fe3O4. These results indicate that MCAB is effective in Cr（Ⅵ） removal from simulated wastewater and promising for real wastewater treatment.