针铁矿对焦磷酸根的吸附特征及吸附机制

Adsorption Behavior and Mechanism of Pyrophosphate on Goethite

为深入了解自然水体中焦磷酸盐的迁移转化行为,以表生环境中广泛存在的稳定矿物-针铁矿为研究对象,系统研究了其对焦磷酸根的吸附过程,探索了不同实验条件下(p H值、电解质、时间、温度)针铁矿对焦磷酸根吸附的影响。结果表明,溶液p H值从6.27升至10.99时,总磷吸附量从3.00 mg/g降低至0.75 mg/g;电解质浓度越低越有利于针铁矿对焦磷酸根的吸附;吸附剂对焦磷酸根的吸附量在最初1 h内增长较快,随后渐渐达到吸附平衡;溶液温度的升高对吸附量提高具有增强作用。用动力学和热力学模型对吸附过程进行拟合,发现准二级动力学和Langmuir模型具有更好的适用性。结合材料吸附焦磷酸根前后的表征,推导出针铁矿对焦磷酸根的吸附机制可能是以表面配合和物理吸附为主导。

In order to study the fate and transport behavior of polyphosphate in water body, the adsorption process of pyrophosphate on synthetic goethite which stablely exists in the supergene environment has been studied systematically. The adsorption behaviors under different conditions （pH, electrolyte, time, temperature） were investigated and the adsorption mechanism was discussed. The results indicate that the adsorption capacity decreases from 3.00 mg/g to 0. 75 mg/g with the increase of pH from 6.27 to 10. 99. The lower the electrolyte concentration, the more favorable to the adsorption. The adsorption characteristic within 48 h was investigated. The adsorption capacity increases rapidly within 1 h, and then reaches the adsorption equilibrium. Moreover, the adsorption capacity increases with the increase of the adsorption temperature. Kinetic models and thermodynamic models were used to analyze the adsorption process, and the results show that the adsorption is in accord with the pseudo second-order equation and Langrnuir model. Furthermore, combined with the characterization of materials, the adsorption may be mainly based on surface eomplexation and physical adsorption.