| 摘要 |
PROBLEM TO BE SOLVED: To facilitate final treatment by cement hardening and recover and reuse a chelating agent so as to lower the cost of decontamination by treating waste water from chemical decontamination treatment carried out using the chelating agent. SOLUTION: At first a caustic alkali is added to decontamination waste water containing a chelate compound to precipitate metals as hydroxides and separate them. Then, a mineral acid is added to the resultant liquid from which the metal hydroxides are separated to precipitate and recover a chelating agent as a free acid. The recovered chelating agent is made soluble by adding a caustic alkali and after the loss of the chelating agent is supplemented, the agent is used again for a decontamination liquid. As for the liquid obtained by filtration and separation of the chelating agent, the chelating agent is oxidized and decomposed by electrolysis to lower COD value. The resultant liquid obtained by filtration of solid matters produced by the decomposition is treated and used as reproduced water for preparation of the decontamination liquid. |
