二段铁盐沉淀深度脱除高浓度含砷废水中的砷

探索高浓度含砷废水中砷的深度脱除方法及脱除机理。采用预氧化-二段铁盐沉淀的方法脱除炼铅烟尘浸出液中的砷,研究影响砷脱除效率的控制条件和因素,砷脱除机理。结果表明,用双氧水氧化原料液中的低价铁和砷,加FeCl3调节铁砷比=1,在pH=4~5、T=60~70℃反应60 min,砷的脱除率达到99.95%,XRD分析结果表明,沉淀物为非晶态砷酸铁形态;在二段除砷中,控制铁砷比=5、pH=7~8,除砷后液中的砷含量小于0.014 mg/L,远低于允许的排放限值。采用二段铁盐脱砷工艺可以将高砷溶液中的砷深度脱除。

Removal of arsenic from wastewater containing high arsenic by secondary precipitating in presence of ferric salt

The aim of this work is exploring the method of arsenic removal in wastewater containing high arsenic. The process of pre-oxidation-precipitation by means of ferric arsenate was employed to remove arsenic in leachate of high arsenic lead dust in smelter,the parameters influencing arsenic removal rate and the mechanism of dearsenifing were studied. It was demonstrated in the first step that arsenic removal rate can reach 99.95% under the conditions of pH=4~5, the iron-arsenic ratio=1, t=60 min, and T=60~70℃ while after the solution was oxidized with oxidant. XRD results indicated that the mineralogical composition of the precipitation is ferric arsenate in vitreous state. Accordingly in the second arsenic removal step, controlling iron-arsenic ratio=5 and pH=7~8, the content of arsenic in filtration was lower than 0.014 mg/L which can well meet requirements of industrial waste emissions. The results show that arsenic in high arsenic solution can be eliminated thoroughly by means of two steps precipitation by adding ferric salt.