Spent pickling bath treatment - with ammonia and hydroxides to prevent pollution

摘要

Usable materials are recovered by (a) adding an element capable of forming insol. F salt, pref. Ca ions; (b) introducing NH3 as gas or as NH4OH, to pH 7; (c) introducing NH3 as in (b), but in excess, to form sol. metal amines, i.e. to pH = 8; (d) adding alkali hydroxides, after filtering off insol. ppte., to substitute NH4+ in NH4NO3 and amines; (e) expelling NH3; (f) separating solid reaction prods. in (e) from alkali nitrate soln.