| abstract |
PROBLEM TO BE SOLVED: To provide a method and an apparatus for efficiently collecting an effective component and reusing washing water in a washing step after a phosphate coating conversion treatment of a metal molded product. SOLUTION: Washing comprises one or more washing steps, taking out washing water from a first washing tank 2 in the first stage of the process, and removing the washing water from phosphoric acid, nitric acid, hydrofluoric acid, silicic hydrofluoric acid, and borofluoric acid. PH adjustment is performed in the pH adjustment tank 4 with one or more kinds of acids described above, and then reverse osmosis treatment is performed in the first reverse osmosis membrane treatment device 6, The first permeate is neutralized with an alkali in a neutralization tank 7, and the neutralized permeate is treated in a second reverse osmosis membrane treatment device 9. The first concentrated liquid is sent to the phosphate coating chemical conversion treatment tank 1 and the second permeated liquid is sent to the first washing tank, and the first concentrated liquid is recycled to the second washing liquid. Is discharged outside the system. |