化学合成及废物基锰氧化物对不同形态砷的去除转化机制

摘要

In order to explore the interaction between different types of manganese oxides and arsenic,waste manganese oxides (filter and pipeline sediment) produced in a drinking water treatment plant in Shengyang and the chemically synthesized vernadite and birnessite were regarded as different types of manganese oxides to study As removal mechanism.The results showed that the pipeline sediment adsorption capacity of As(Ⅴ) was 90 μg under 0.20 g dosage,which was much smaller than that of vernadite (191 μg),birnessite (192 μg) and filter (176 μg).As(Ⅲ) in solution could not be completely oxidized by pipeline sediment in 2 h.The adsorption of As for the four kinds of manganese oxides was more consistent with the pseudo-second order kinetic model,indicating that the removal process was a complex process of rapid adsorption and slow adsorption,including external liquid film diffusion,surface adsorption and particle diffusion.The crystal form of manganese oxides in vernadite,birnessite and filter were preferable,and SiO2was the primary crystal form in the pipeline precipitation.The crystal form of filter was in perfect accordance with birnessite,but the morphologies were very different.The average oxidation degree of Mn in the four manganese oxides was 3.90,3.89,3.84 and 3.71,respectively.Studies have shown that the filter as a waste-based material can replace the chemically-synthesized vernadite and birnessite for removing As in water system to achieve the goal of co-processing waste materials and As remediation.%为探究不同类型锰氧化物与As(砷)的交互作用,采用沈阳某饮用水处理厂除锰滤池运行周期结束后产生的废料(滤料和管道沉淀物)和化学合成水羟锰矿、酸性水钠锰矿作为不同类型的锰氧化物,研究化学合成及废物基锰氧化物对不同形态As的去除转化机制.结果表明:锰氧化物的投加量为0.20 g时,管道沉淀物对As(Ⅴ)的吸附量为90 μg,远小于水羟锰矿、酸性水钠锰矿和滤料的191、192、176 μg吸附量,而且管道沉淀物2h内不能够完全氧化溶液中As(Ⅲ).四种锰氧化物对As的吸附都更符合准二级动力学方程,说明去除过程是一个快速吸附和慢速吸附相互叠加的过程,包含外部液膜扩散、表面吸附和颗粒内扩散等.水羟锰矿、酸性水钠锰矿和滤料有较好锰氧化物晶型,管道沉淀中SiO2是主要晶型,滤料晶型和酸性水钠锰矿一致,但是形貌结构却差别很大.四种锰氧化物的Mn平均氧化度较高,分别为3.90、3.89、3.84和3.71.研究显示,滤料作为废物基材料可以替代化学合成的水羟锰矿、酸性水钠锰矿实现对水体中As的去除,达到废物材料的再利用及含As水体修复的协同处置.