黄土对锰离子的吸附特性及机理研究

重金属污染事件频发引起了很多学者的关注，锰是一种重金属痕量元素，人体通过食物链摄入过量的锰会产生中毒效应。研究了Mn(II)的浓度、反应温度、土水比、pH值等因素对Mn(II)在黄土上吸附特性的影响。黄土对Mn(II)的吸附容量可达7.84 mg/g，等温吸附模型Langmuir、Freundlich和D-R模型都能很好地解释Mn(II)在黄土上的吸附性能。热动力学分析表明Mn(II)在黄土上的吸附是一个自发的过程，升高温度可促进吸附作用的进行。增大土水比可提高Mn(II)的去除效率，但单位黄土上Mn(II)的吸附量有个最优值。Mn(II)的初始浓度越大单位黄土的最大吸附量越小，达到最大吸附量所需的土水比越高。溶液的酸碱度是影响Mn(II)去除效果的一个重要因素，pH>10.7时Mn(II)几乎完全被去除。通过X光衍射图谱和红外光谱分析，探讨了黄土与Mn(II)的结合机理，黄土中的黏土矿物、有机质成分对重金属Mn(II)的吸附起重要作用。

Adsorption behavior and mechanism of loess soil towards manganese ions

Environmental pollution accidents frequently induced by heavy metals have aroused broad interest of many researchers. Manganese is a trace element and toxic effect will be caused by the excessive intake of manganese. The factors including the concentration of Mn(II), reaction temperature, soil water ratio and pH value are studied to investigate the adsorption behavior of loess soil towards Mn(II). The adsorption capacity of Mn(II) on loess soil is determined to be 7.84 mg/g, and the adsorption test results can be well interpreted by three isotherm models (i.e., Langmuir, Freundlich and D-R models). The thermodynamic analysis indicates that the adsorption process of Mn(II) on loess soil is spontaneous, and higher temperature benefits the adsorption process. The removal efficiency of Mn(II) from aqueous solution can be raised by increasing solid-liquid ratio, but the unit adsorption amount of Mn(II) on loess soil has an optimum value. Higher initial concentration of Mn(II) leads to smaller optimum adsorption amount of loess soil, which is reached at higher solid-liquid ratio. pH value has great influence on the removal efficiency of Mn(II) from aqueous solution, and Mn(II) can be nearly completely removed when pH>10.7. X-ray diffraction spectra and Fourier transform-infrared spectra are used to further discuss the adsorption mechanism of Mn(II) on loess soil, and the analysis indicates that the clay minerals and the organic matter in loess play important roles in Mn(II) removal.