MnO_2对水体中As(Ⅲ)、As(Ⅴ)的吸附性能

Adsorption of As (Ⅲ) and As (Ⅴ) from aqueous solutions by manganese dioxide

为了研究MnO2对水体中As(Ⅲ)和As(Ⅴ)去除的差异及其相关机理,在恒温(25±1℃)条件下,设置溶液pH、振荡时间、MnO2投入量、砷初始浓度等参数的变化进行相关研究.结果表明,在酸性条件下,MnO2对As(Ⅲ)和As(Ⅴ)的去除效果最佳;振荡时间在0—3 h时,MnO2对As(Ⅲ)的去除率大于As(Ⅴ);随着砷的初始浓度升高,As(Ⅲ)和As(Ⅴ)的去除率均表现为显著降低;MnO2对As(Ⅲ)的最大吸附量随MnO2投入量的加大而减小;准二级吸附动力学方程均能很好的描述砷的吸附过程,As(Ⅲ)和As(Ⅴ)平衡吸附量为0.4 mg·g-1;As(Ⅲ)吸附等温线能很好地用Langmuir方程进行描述,而As(Ⅴ)则符合Freundlich等温吸附模型.

Batch adsorption experiments were performed under isothermal conditions （25±1℃ ）, in order to evaluate the adsorption characteristics of As （ Ⅲ ） and As （ V ） with various parameters such as pH, oscillation time, dosage of MnO2 and initial concentration of arsenic on the removal efficiency using manganese dioxide, The results showed that the highest removal of As（Ⅲ ） and As（ V ） occurred in the acidic solutions. The removal rate of As （Ⅲ） was higher than that of As （ V ） in the first 3 hours, and the equilibrium adsorption capacity reached 0.4 mg·g^-1. With increased dosage of MnO2 in the solution, the removal rate showed an increasing trend while the maximum adsorption amount of As （Ⅲ） decreased. Adsorption of As （Ⅲ） and As （ V ） decreased significantly with the inerease of initial concentration. Kinetic date fitted well the pseudo second-order kinetic. Adsorption isotherm of As （Ⅲ） can be described by the Langmuir model, but As （ V ） was more consistent with the Freundlieh model.