天然锰砂去除水中的砷

Removal of arsenic from water by natural manganese sand

天然锰砂是一种廉价、高效的水处理用材料,但尚未用于水中砷的去除。实验研究了反应时间、砷形态、初始砷浓度、温度、溶液初始pH对吸附过程的影响。结果表明,天然锰砂对As(Ⅲ)的吸附能力大于As(Ⅴ)。25℃时,固液比为10 g/L的条件下,天然锰砂对初始浓度为5.0 mg/L的砷溶液吸附过程经72 h基本达到平衡,平衡时对As(Ⅲ)和As(Ⅴ)的去除率分别达到94.5%和85.9%。吸附过程符合Lagergren准一级反应动力学模型和假二级反应动力学模型。相比之下,假二级动力学模型拟合程度更高。对As(Ⅲ)和As(Ⅴ),45℃时的吸附量均大于25℃时。不同温度下,天然锰砂对As(Ⅲ)和As(Ⅴ)的吸附过程更符合Freundlich等温吸附模型。在溶液初始pH为3～10范围内,锰砂对砷的吸附能力受pH的影响较小。实验结果表明,天然锰砂是一种具有实际应用潜力的除砷材料。

Although natural manganese sand is a cost-effective material for water treatment, it has not been used for arsenic removal. Effects of contact time, arsenic species, initial concentration, temperature, and initial solution pH were investigated to evaluate the characteristics of arsenic adsorption on natural manganese sand. Results showed that adsorption capacity for As（ Ⅲ ） was greater than that for As（ Ⅴ ）. With the dosage of 10 g/L and the initial As concentration of 5 mg/L, the adsorption achieved equilibrium at about 72 h at 25℃. Removal efficiencies of As（ Ⅲ ） and As（ Ⅴ ） by natural manganese sand were up to 94.5% and 85.9% , respectively, at adsorption equilibrium. The adsorption kinetics was described by both Lagergren first order kinetics model and the pseudo-second order kinetics model, although the latter one fitted better. For both As（ Ⅲ ） and As（ Ⅴ ） , arsenic adsorption at 45℃ was greater than that at 25℃. Freundlich isotherm model better described As（Ⅲ ） and As（ Ⅴ） adsorption than Langmuir isotherm at 25℃ and 45℃. When the initial solution pH ranged from 3 to 10, arsenic adsorption on manganese sand was not significantly affected. It suggested that natural manganese sand is a potential adsorbent for arsenic removal in the practical application.