PURPOSE:To reprocess a separation reagent to recirculate the same for reuse, by distilling the aqueous ammonium chloride solution separated, to which magnesium hydroxide is added, from a strong acid type ion exchange resin to recover aqueous ammonia. CONSTITUTION:Waste water containing ammonium fluoride and ammonia is treated with a strong acid type ion exchange resin to separate the ammonium ion therein and, therafter, concn. sulfuric acid is added to the treated waste water to perform extractive distillation to recover hydrogen fluoride while the remaining diluted sulfuric acid is concn. to be recirculated to the extractive distillation process. The ion exchange resin adsorbing the ammonium ion is regenerated by an aqueous hydrochloric acid solution and Mg(OH)2 is added to the remaining aqueous ammonium chloride solution and distillation is performed to recover aqueous ammonia while the formed MgCl2-containing residual liquid is hydrothermally decomposed to obtain HCl and Mg(OH)2, and the former is recirculated to the aforementioned ion exchange resin regeneration process.
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