电解锰废水中Cr^(6+)、Mn^(2+)的去除方法研究

Removal of Cr^(6+) and Mn^(2+) from electrolytic manganese wastewater

通过实验研究了还原沉淀-晶种曝气组合工艺去除电解锰废水中Cr6+和Mn2+,并探索了最佳工艺条件.首先以Na2SO3做还原剂将Cr6+转化为Cr3+后再通过化学沉淀法除去,然后采用加入MnO2做晶种曝气氧化去除废水中的Mn2+.结果表明:当Na2SO3投加量为0.5 g/L,还原反应pH值为4,还原反应时间6 min,Cr6+可完全转化为Cr3+.Cr3+在pH值为8时沉淀最完全,出水总铬浓度可从100 mg/L降到0.5 mg/L以下.除铬后,当MnO2投加量为25 g/L,废水pH值为9,曝气10 min,出水Mn2+浓度可从1 000 mg/L降到0.4 mg/L以下.通过以上处理出水总铬和总锰均达到我国《污水综合排放标准(GB8978-1996)》一级要求.

A new technology of reduction precipitation combined with crystal seed aeration is proposed for completely removing Cr6＋and Mn2＋from electrolytic manganese wastewater by studying the optimum treatment conditions. In the first step, Cr6＋ was removed by chemical precipitation by transforming into Cr3＋ using Na2SO3 as reductant. Then Mn2＋is removed by aeration using MnO2 as crystal seed. The results are as follows：Cr6＋ can be transformed into Cr3＋ completely with Na2SO3 dosage of 0.5 g/L, reduction pH value of 4, reduction time of 6 min. Precipitation of Cr3＋ is the most complete when pH value is 8 and the effluent concentration of total chromium is less than 0.5 mg/L from 100 mg/L. After chromium removal, the effluent concentration of Mn2＋ is less than 0.4 mg/L from 1 000 mg/L when MnO2 dosage is 25 g/L, wastewater pH value is 9 and aeration time is 10 min which meets the first grade national sewage effluent discharge standard （GB8978-1996）.