纳米磁性磷酸二氢钙对Cd的吸附、回收与再生

以Ca（H₂PO₄）₂、铁盐与亚铁盐为原料，采用共沉淀法制备成纳米磁性材料Ca（H₂PO₄）₂@Fe₃O₄（NMCDP），研究其对Cd²⁺的吸附、回收与再生效果.透射电镜（TEM）、红外光谱（FTIR）、X射线衍射（XRD）显示，NMCDP粒径约60 nm，稳定性良好，饱和磁化强度为30.9 emu·g^-1.吸附动力学表明，NMCDP对Cd²⁺的吸附1 h之内即可达到平衡，符合准二级动力学模型.吸附热力学表明，NMCDP对Cd²⁺的吸附符合Langmuir与Freundlich等温吸附模型，最大吸附量为142.50 mg·g^-1.在pH值由2增加到3时，吸附量随溶液初始pH值的升高而增加，当pH值大于3后，逐渐保持稳定；溶液中共存离子Na⁺、Mg²⁺、Cu²⁺对材料吸附Cd²⁺均有一定的影响，影响程度Cu²⁺ > Mg²⁺ > Na⁺.采用0.01 mol·L^-1 HCl与EDTA-Na₂均可解吸出部分吸附的Cd²⁺，以EDTA-Na₂解吸率较高，达到68%，从而实现NMCDP的再生.

Adsorption, Reclaim, and Regeneration of Cd by Magnetic Calcium Dihydrogen Phosphate Nanoparticles

In order to improve the adsorption-separation of Cd²⁺ in water treatment, magnetic Fe₃O₄ coated Ca(H₂PO₄)₂ nanoparticles (NMCDP) were developed by coprecipitation. The properties of these nanoparticles were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and magnetization curves. Experiments were carried out to investigate the effect of adsorption, reclaiming, and regeneration. The results showed that NMCDP was a stable material with a particle size of 60 nm and a saturation magnetization of 30.9 emu·g^-1. The adsorption rate of Cd²⁺ by NMCDP was fast, and adsorption equilibrium could be achieved within 1 hour. The kinetic data were well fitted by a pseudo-second-order model, and the isotherm adsorption data agreed with the Langmuir and Freundlich model, with a maximum adsorption capacity of 142.50 mg·g^-1. The adsorption capacity of Cd²⁺ was affected by the pH and increased when the pH was increased from 2 to 3, while with continued increase of the pH of the solution, the adsorption capacity gradually became stable. The coexisting ions in the solution had an effect on the adsorption of Cd²⁺, especially the divalent cation Cu²⁺. The NMCDP could be regenerated by using 0.01 mol·L^-1 HCl and EDTA-Na₂, and the results indicated that it could be recycled with a desorption rate of 68% by EDTA-Na₂ solution.