| 摘要 |
PROBLEM TO BE SOLVED: To effectively use waste liquor of hydrochloric acid containing iron ion as an impurity, obtained by making a hydrogen chloride gas, prepared as by-product in a process for obtaining hematite (ferric oxide) from a solution of ferrous chloride, absorbed in pure water. SOLUTION: A material to be etched is etched with a solution of ferric chloride to give an etching waste liquor 52 of ferric chloride, which is reacted with iron powder to give a solution 80 of iron salt comprising ferrous chloride as a main component. The solution of the iron salt and the waste liquor of hydrochloric acid are stored in a treating tank 71 and reacted with an oxidizing gas under heating in the tank. The ferrous chloride in the solution of the iron salt is oxidized into ferric chloride by the reaction to regenerate an etching solution of ferric chloride.
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