单宁酸铁吸附去除水中无机氮的性能与机制研究

Performance and Mechanism of Ferric Tannate in the Removal of Inorganic Nitrogen from Wastewater

通过批量吸附实验,研究了一种新型吸附材料——单宁酸铁吸附去除水中无机氮(NH+4-N、NO-2-N和NO-3-N)的效果及其吸附机制.结果表明,单宁酸铁对NH+4-N和NO-2-N具有优先选择性,当单宁酸铁与NH+4-N和NO-2-N的质量比为200时,NH+4-N和NO-2-N去除率均大于95%.运用吸附动力学模型、Weber-Morris方程、Langmuir和Freundlich方程进行实验数据拟合的结果表明,NH+4-N和NO-2-N在单宁酸铁表面分别进行单分子层和多分子层的吸附,其吸附过程符合二级动力学模型,并且颗粒外部扩散和表面吸附起主要的作用.NH+4-N与分布于单宁酸铁外表面的氧负离子通过静电作用结合,NO-2-N则与单宁酸铁中的铁离子通过静电作用和配位作用结合.本研究为单宁酸铁作为吸附剂的发展与应用提供了科学依据.

A novel adsorbent material-ferric tannate was synthesized,and performances and mechanisms of NH+4-N,NO-2-N and NO-3-N were investigated via batch adsorption experiments. The results indicated that ferric tannate exhibited preferential adsorption for NH+4-N and NO-2-N. When the mass ratios of ferric tannate to NH+4-N and ferric tannate to NO-2-N were both 200,the removal efficiencies were both higher than 95%. The adsorption behaviors were analyzed with adsorption kinetic models,Langmuir and Freundlich isotherm adsorption models,and Weber-Morris equation. The results implied that NH+4-N and NO-2-N were adsorbed on the surface of ferric tannate in the forms of monolayer and multilayer,respectively. The pseudo-second order kinetic model was more suitable to describe the adsorption processes,and the external particle diffusion and surface adsorption played the key roles in the adsorption process. NH+4-N could be combined with negative oxygen ions which distributed on the external surface of ferric tannate by the electrostatic interaction,whereas NO-2-N could be combined with ferric ions in ferric tannate by the electrostatic interaction and coordination. The present study provided scientific evidence for the application of ferric tannate as a potential adsorbent in the future.