| 摘要 |
PROBLEM TO BE SOLVED: To provide a treatment method which can improve the treatment properties of metals and hexavalent chromium by a simple operation and prevent the regeneration of hexavalent chromium with time in the treatment of strongly acidic etching wastewater containing small amount of hexavalent chromium as a heavy metal in a large amount of iron, and containing a large amount of hydrogen peroxide. SOLUTION: In the wastewater treatment method, a part of reduction-inhibiting substances is decomposed beforehand by a pretreatment agent, and then a coagulant is added under an alkaline condition. Especially in the treatment of etching wastewater of a chromium-containing iron-based alloy, after decomposing and removing a part of hydrogen peroxide by adding manganese dioxide to the strongly acidic etching wastewater containing a high concentration of hydrogen peroxide, the hydrogen peroxide is decomposed while adding sodium hydroxide, pH is adjusted to an alkaline pH of 9.5 with calcium hydroxide after neutralization to form metal hydroxide mainly comprising iron, and then iron ions and hexavalent chromium in the wastewater are coagulated and removed at the same time by a coagulant having a reduction property. COPYRIGHT: (C)2007,JPO&INPIT
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