海南热带雨林土壤中胡敏酸对Pb2+、Cu2+的吸附解吸特性研究

重金属元素在土壤-溶液界面的吸附反应深刻地影响重金属行为及其生态风险。以热带次生雨林土壤中提取的胡敏酸为材料, 采用傅立叶红外光谱、扫描电镜等技术对胡敏酸进行了表征, 通过批量吸附实验研究了胡敏酸对铅、铜的吸附特性, 通过连续解吸方法研究了在不同浓度下饱和吸附的胡敏酸对重金属吸附的形成过程。结果表明, 胡敏酸的腐殖化系数较高, 阳离子交换量为52.84 mmol·g-1, 表面含有羧基和酚羟基官能团。胡敏酸对铜的吸附符合准二级动力学模型, 对铅的吸附符合准一级动力学方程; Langmuir 模型能够更好地描述单一和复合污染条件下胡敏酸对Pb2+的等温吸附行为, Freundlich 模型能够更好的描述单一和复合污染条件下胡敏酸对Cu2+的等温吸附行为。通过连续解吸实验发现, 胡敏酸对铅的吸附过程中4种结合方式的先后饱和顺序为: 物理吸附、络合、离子交换和氢键结合。胡敏酸对铜的吸附过程中4种结合方式的先后饱和顺序为: 络合、氢键结合、离子交换和物理吸附。

Characteristic of adsorption of Pb2+ and Cu2+ onto soil humic acids from tropical rainforest,hainan province

The adsorption properties of heavy metal elements at the soil-solution interface profoundly influence the behavior and ecological risk of heavy metal.The adsorptive behavior of Pb^2+ and Cu^2+ onto humic acid which extracted by alkali dissolution-acid deposition from tropical primary secondary forest soil was investigated.Humic acid was characterized by Fourier infrared spectroscopy,scanning electron microscopy and other techniques.The adsorption characteristics of humic acid to lead and copper were studied through batch adsorption experiment.The composition mechanism of the total amount of lead and copper adsorbed by Humic acid saturated with different concentrations by continuous desorption method.The results showed that humification coefficient of humic acid was high,the cation exchange capacity was 52.84 mmol·g^-1,and the surface contained carboxyl group and phenol hydroxyl functional group.The adsorption of humic acid to copper conforms to the quasi-second-order kinetic model and the adsorption of lead conforms to the quasi-first-order kinetic equation.Langmuir model can better describe the isothermal adsorption behavior of humic acid to Pb^2+ under single and combined pollution conditions,and Freundlich model can better describe the isothermal adsorption behavior of humic acid to Cu^2+ under single and combined pollution conditions.Through continuous desorption experiments,it was found that the saturation sequence of the four binding modes in the adsorption process of humic acid to lead is:physical adsorption and complexation,then ion exchange mode,and finally hydrogen bond mode.The saturation sequence of the four binding modes in the adsorption process of humic acid to copper is:complexation,then hydrogen bond binding and ion exchange mode,and finally physical adsorption mode.