铁锰结核对As(Ⅲ)的吸附和氧化特性研究

研究As(Ⅲ)在土壤中的铁锰结核上的吸附和氧化特征,对理解土壤中As(Ⅲ)的含量变化和制定有效的治理措施有至关重要的作用.以东北地区代表性土壤-棕壤中提取的铁锰结核作为试验材料,采用一次平衡法,对As(Ⅲ)在铁锰结核上的吸附和氧化特性,及其动力学特征进行了研究.研究结果表明,反应是包括吸附和氧化反应的复杂过程.初始质量浓度在1～15 mg·L~(-1)的范围内时,随着初始质量浓度的提高,吸附量随之增大,Mn的释放量增加,初始质量浓度在15～30 mg·L~(-1)的范围内时,吸附量的增加缓慢,Mn的释放量也接近平衡,吸附曲线可用Langmuir方程及Freundlich方程拟合(r>0.97),铁锰结核对As(Ⅲ)具有较强的吸附性能,最大吸附量达到了3 000 mg·kg~(-1).动力学实验中,反应在24 h内趋于饱和,可用Freundlich模型描述.氧化反应后释放到溶液中的As(V)质量浓度随时间变化先升高后降低,大多数的As(V)都被吸附在了铁锰结核表面,说明铁锰结核对砷具有很好的吸附和解毒作用.Mn的释放量在6 h时基本达到平衡.释放到溶液中的Mn质量浓度与时间符合Elovich动力学方程.

Adsorption and oxidation of arsenic(Ⅲ) by Fe-Mn nodules

Determining the nature of As(Ⅲ) adsorption and oxidation by iron and manganese oxides in soil is critical for understanding the fate of contaminant arsenic in soils and formulating effective remediation strategies. In batch experiments, Fe-Mn nodules were collected from brown soil which was a typical soil in the northeast region of China. Oxidation and adsorption characteristics of As(Ⅲ) and its kinetic characteristics by Fe-Mn nodules was investigated at various As(Ⅲ) concentrations(l～30 mg·L~(-1)) and various times with the method of one way balancing. The results show that the reaction is complex process including adsorption and oxidation reactions. When the initial As(Ⅲ) concentration was 1～15 mg·L~(-1), the adsorption capacity and Mn concentration increased with the increased of the initial As(Ⅲ) concentration. When the initial As(Ⅲ) concentration was 15～30 mg·L~(-1), the adsorption of Mn concentration increased slowly and close to balance, The isothermal experiment showed both Langmuir and Freundlich isothermal equations can describe the thermodynamic behaviors of adsorption very well(r>0.97).The results showed that the Fe-Mn nodules was effective for As(Ⅲ) removal, and the maximal adsorption capacity of As(Ⅲ) was 3 000 mg·kg~(-1).The adsorption and oxidation equilibrium was reached after reacting 24 hours and Freundlich kinetics equations had a better simulation(r>0.95). The Mn concentration fitted the Elovich kinetic equation and closed to balance after 6 hours. The As(V) concentration increased and the decreased with time varying. Most of As(V) adsorption to the surface sites of Fe-Mn nodules following its production otherwise release into solution. That illuminated Fe-Mn nodules has significant effects on the removal of arsenic and detoxification.