Zr4+掺杂对Mg/Al水滑石磷吸附行为的影响

Effect of Zr4+ Doping on Phosphorus Adsorption Behavior of Mg/Al Hydrotalcite

摘要:

采用共沉淀法制备了系列不同Zr4+含量的Mg/Al/Zr三元类水滑石材料，研究了其对废水中磷酸根离子的吸附性能。采用XRD、DRIFTS、氮气吸脱附实验等手段对材料的结构及织构性质进行了表征，并研究了溶液初始pH以及竞争阴离子对磷吸附量的影响。结果表明：掺杂Zr4+能提高类水滑石层板正电荷密度以及增大层间距，有利于磷酸根阴离子的吸附；Mg/Al/Zr类水滑石对磷的吸附过程符合准二级动力学模型，吸附等温线符合Langmuir模型，当n(Zr4+)/(Al3++Zr4+)为0.3时，理论饱和吸附量最大，达到76.6 mg/g，比Mg/Al水滑石高出28.7%；酸性环境有利于磷酸根的吸附，而二价阴离子的竞争吸附作用会显著降低磷吸附效果。Mg/Al/Zr类水滑石对磷的吸附机理为静电吸引和阴离子交换协同作用。

Abstract:

A series of Mg/Al/Zr ternary hydrotalcite-like materials with different Zr4+ contents were prepared by co-precipitation method. The phosphate adsorption performances of these materials were also studied. The structural and textural properties of these materials were characterized by XRD, DRIFTS and nitrogen adsorption-desorption experiments. The effects of initial pH and competitive anions on the phosphate adsorption capacity were also investigated. The results show that the addition of Zr4+ enhanced the positive charge density of the hydrotalcite-like layer and increased the interlayer spacing, which was beneficial to the adsorption of phosphate anions. The phosphorus adsorption process of Mg/Al/Zr hydrotalcite-like followed the pseudo-second-order kinetic model. The adsorption isotherm followed the Langmuir model. As the molar ratio of (Zr4+)/(Al3++Zr4+) was 0.3, the theoretical saturated adsorption uptake of Mg/Al/Zr hydrotalcite-like reached the maximum value of 76.6 mg/g that was 28.7% higher than that of Mg/Al hydrotalcite. The acidic environment was conducive to the adsorption of phosphate, while the competitive adsorption of divalent anions significantly reduced the phosphorus adsorption performance. The phosphorus adsorption of Mg/Al/Zr hydrotalcite-like was the result of the synergistic effect of electrostatic attraction and anion exchange.