球形零价铁生物炭吸附Cd(II)的性能和机制

Cd(II) adsorption efficiency and mechanism by spherical zero-valent iron/biochar composites

摘要:

本研究提供了一种一步热解法制备纳米零价铁生物炭的方法。将海藻酸铁在高温缺氧条件下热解制备了球形零价铁生物炭复合材料（ZVIBC），考察了Cd(II)溶液pH、初始浓度、吸附时间、背景离子、空气中老化时间对ZVIBC吸附Cd(II)性能的影响，通过FTIR、XRD、XPS、EDS等方法对ZVIBC以及ZVIBC-Cd(II)进行了表征，研究了ZVIBC对Cd(II)的吸附机理。结果显示：pH对ZVIBC吸附Cd(II)有显著的影响，4为最佳吸附pH条件。ZVIBC吸附Cd(II)的过程符合Langmuir模型，拟合的饱和吸附量为240 mg/g。主要吸附机理为：活性官能团（O—H、C—O、C=C、C=O、COO）与Cd(II)形成配合物，以及Cd(II)与Fe2+生成Cd(OH)2沉淀。

Abstract:

This study provides a one-step pyrolysis method for the preparation of nanosized zero-valent iron biochar. A spherical ZVI/Biochar composite (ZVIBC) was successfully prepared via carbonization of Fe3+-crosslinked sodium alginate. The effects of pH, Cd(II) initial concentration, adsorbent time, coexisting anions, and aging under air on the adsorption of Cd(II) by ZVIBC are studied. The results of physico-chemical characterization obtained for the ZVIBC loaded with Cd(II) (FTIR, XRD, XPS, and EDS) allowed to propose the mechanism of adsorption. The results showed that the pH was a strong impact on the adsorption of Cd(II) by ZVIBC，4 was selected as the optimum pH value and used throughout the following experiments. The Langmuir model better describe the adsorption of Cd(II) on ZVIBC with the maximum adsorption capacity of 240 mg/g. The main adsorption mechanisms were that the active functional groups (O—H、C—O、C=C、C=O、COO) formed complexes with Cd(II), and Cd(II) generated Cd(OH)2 precipitation with Fe2+ on ZVIBC surface.