包埋磷酸盐小球的合成及其对溶液中铅镉的吸附与固定（英文）

Synthesis of phosphate-embedded calcium alginate beads for Pb(Ⅱ) and Cd(Ⅱ) sorption and immobilization in aqueous solutions

采用海藻酸钠、磷酸二氢钙和碳酸氢钠成功合成了包埋磷酸盐的海藻酸钙小球。通过扫描电镜、傅里叶变换红外光谱、X射线衍射等分析表征了该小球的形貌与结构。研究p H值和初始金属离子浓度对铅镉去除率的影响,发现吸附铅镉的最佳p H值分别为4.0和5.5;铅镉的最适初始浓度分别为200 mg/L和25 mg/L,对应的去除率分别达94.2%和80%。XRD和FTIR的分析结果证实了该小球对铅镉的去除机理为:铅镉离子吸附到小球的表面,与小球的羧基发生反应,进而与磷酸根反应生成稳定的磷酸盐沉淀。铅镉的吸附符合Langmuir等温线方程,拟合系数R2分别为0.9957和0.988。根据Langmuir等温线方程计算得到铅镉的理论饱和吸附量分别为263.16mg/g和82.64 mg/g。研究结果表明该小球对溶液中的铅镉离子有良好的处理效果,同时由于生成稳定的沉淀物,也能应用于处理被铅镉污染的水稻土。

The phosphate-embedded calcium alginate beads were successfully synthesized based on sodium alginate, calcium dihydrogen phosphate and sodium hydrogen carbonate. Scanning electron microscopy, Fourier transformed infrared (FTIR) spectroscopy and X-ray diffraction (XRD) were conducted to characterize the morphology and structure of the phosphate-embedded calcium alginate beads. The effects of pH and the initial concentration of the metal ions on Pb(II) and Cd(II) sorption by the beads were investigated. The optimal pH values for Pb(II) and Cd(II) sorption are 4.0 and 5.5, respectively. The optimal initial concentrations of Pb(II) and Cd(II) are 200 mg/L and 25 mg/L, correspondingly, and the removal efficiencies are 94.2% and 80%,respectively. The sorption mechanism is that the heavy metal ions accessed the beads firstly due to the large surface area, combinedwith OH?, and then precipitated with phosphate radical, which was proven by FTIR and XRD. The sorption of Pb(II) and Cd(II) isfitted to Langmuir isotherm model with R2 values of 0.9957 and 0.988, respectively. The sorption capacities of Pb(II) and Cd(II) are263.16 mg/g and 82.64 mg/g, respectively. The results indicate that the phosphate-embedded calcium alginate beads could be appliedto treating Pb(II)/Cd(II)-containing wastewater and it could be implied that the synthesized beads also could be used as a kind of soil ameliorant for remediation of the heavy metal contaminated paddy soil.