电镀废水的铬污染特征及调控

Characteristics and Control of Cr Pollution in Electroplating Wastewater

以广东省潮州市彩塘不锈钢电镀区的水体为例,研究了电镀废水、底泥的Cr分布特征和基本特性,并针对废水基本特性,采用FeSO4进行调控,探讨如何将Cr6+转化Cr3+以及除去废水中Cr的途径。电镀废水中的总Cr和Cr6+分别为57.3mg/L、42.4mg/L,远远超过了电镀废水排放标准37、83倍,导致河流水体Cr6+超过环境质量标准。电镀废水具有低pH值和高电导率。电镀区底泥Cr大大超过背景值,底泥中的Cr残渣态含量最高,其次是氧化态、还原态,可溶态和碳酸盐态含量低,说明了底泥存在潜在危害性。FeSO4能有效地将Cr6+还原为Cr3+,Fe2+/Cr6+摩尔比为4具有很好转化效率,还原充分后将pH值调至9,对Cr3+具有最好的沉淀效果,通过该途径有效除去废水的Cr。

Distribution characteristics of Cr in the electroplating wastewater and sediments were investigated in Caitang Town,Chaozhou City,Guangdong Province.FeSO4 was used to reduce Cr6+ and Cr3+ was precipitated and removed by controlled pH value in electroplating wastewater in the experiment.Results showed that Cr and Cr6+ concentrations in the electroplating wastewater were 57.3mg/L and 42.4mg/L,exceeding electroplating wastewater discharge standard by 37 and 83 times respectively,which resulted in Cr6+ in stream exceeding surface water standard.There were low pH value and high conductivity in the electroplating wastewater.Cr concentrations in the sediments in electroplating areas were much higher than background value.Concentrations of Cr in the sediments were dominated by residual fraction,followed by oxidizable fraction and reducible fraction.The sequential geochemical extraction test showed that the sediments had low mobility and bioavailability for Cr.Cr6+ could be reduced into Cr3+ by ferrous sulphate,and reduction efficiency was highest at 4 of the ratio of Fe2+ and Cr6+.Cr in the electroplating wastewater could be removed most effectively at pH value 9 after Cr6+ was reduced by ferrous sulphate.