VERFAHREN ZUM ENTFERNEN VON SCHWERMETALLEN AUS MINERALSAEUREN.

摘要

In removing heavy metals, esp. Cu, As, Sb and Pb, from inorganic acids by the pptn. of their sulphides, the inorganic acid is left to react with H2S or an alkali sulphide soln. under pressure, esp. of 1.5-10 bar, with strong stirring. Then, the solid obtd. is sepd. from the inorganic acid, while retaining the pressure. The inorganic acid is esp. H3PO4, partic. wet process phosphoric acid, or H2SO4. The inorganic acid is pref. admixed with 0.05-5 (0.1-0.5) wt.% filter auxiliary, esp. kieselguhr, before treatment with H2S or the alkali sulphide soln.. Pref. H2S or alkali sulphide is added in an amt. of 150-500 (200-300) mol.%, w.r.t. the stoichiometric amt. needed to ppte. the heavy metals as sulphides. A pressure filter is pref. used to separate the solid formed from the inorganic acid. The H2S or the alkali sulphide soln. is pref. introduced into the suction conduit of a high speed pump loading the pressure filter. The charging takes place directly in front of the pump. The sulphide pptn. or filtration temp. can be adjusted in function of the concn. of the inorganic acid, e.g. 30-70-, 60-90 or 100-140 deg.C respectively, for H3PO4 having P2O5 concn. 30-, 60- or 85 wt.%.