用低品位菱铁矿石去除水中低浓度磷酸盐

Removal of Low Concentration Phosphate Using Low Grade Siderite

用扫描电子显微镜、透射电子显微镜、X射线衍射仪、X射线荧光和Fourier红外等技术研究了铜陵新桥天然菱铁矿吸附除磷前后的结构和组成特征,结合粒径、溶液p H、反应温度、干扰离子、溶解氧对菱铁矿吸附除磷的效果影响,分析了天然菱铁矿深度除磷的效果及机理。静态吸附实验表明:25℃室温下,在初始磷浓度为1 mg/L,固液质量比为1﹕500时,吸附后溶液中残留磷浓度低于0.025 mg/L,处理后的磷浓度满足地表水环境质量Ⅱ类标准。动力学、热力学实验结果表明:25℃室温下,接触反应8 h时可达到平衡,过程较好地符合Lagergren准二级速率方程;天然菱铁矿对磷的去除规律可用Langmuir模型很好地描述,静态实验除磷饱和容量为6.101 mg/g,并且不受水体共存离子影响。其除磷作用机理主要是菱铁矿中亚铁经氧化产生新生铁氧化物对磷酸根的化学吸附,溶解氧对除磷有显著影响。吸附的产物是以双齿双核表面配位为主,以少量单齿单核表面配位为辅的配位化合物。利用天然菱铁矿在水中氧化产生铁氢氧化物的特性,在城市生活污水深度除磷以及富营养化水体净化领域具有潜在应用价值。

The structure and composition of a natural siderite （from Tongling, Anhui） were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray fluorescence, Fourier transformed infrared spectoscopy and other modem testing methods, respectively. Furthermore, the performance and mechanism of the natural siderite on the removal of phosphate with respect to the effects of particle size, solution pH, reaction temperature, interfering ions and dissolved oxygen were investigated. The experimental results via the static adsorption show that when the initial phosphorus concentration is 1 mg/L, and the solid-liquid ratio is 1：500, P concentration in the solution is less than 0.025 mg/L after the adsorption at 25 ~C, and the phosphorus concentration of effluent achieves the II criterion of environmental quality for surface water. According to the kinetic and thermodynamic analysis, the adsorption equilibrium occurs at the reaction time of 8 h and 25 ~C, and the adsorption process follows the quasi-second-order kinetics model. The process of siderite on adsorption of phosphate can be well described by the Langmuir isotherm adsorption model, and P saturated adsorption capacity is 6.101 mg/g. This natural siderite cannot be affected by the interference ions in water. The removal mechanism is a chemical adsorption for phosphate. The adsorption products of the surface are bidentate-binuclear surface complexes oriented, and a small amount of monodentate-mononuclear coordination compounds. The natural siderite oxidation to produce iron hydroxide is a foundation for phosphorus removal in water, indicating a promising potential application in the fields of water purification and P removal in urban sewage.