GB1433606A - Treatment of aqueous effluents containing sulphurous impurities - Google Patents

Abstract

1433606 Treating effluents containing sulphur compounds L'AIR LIQUIDE SOC ANON POUR L'ETUDE ET L'EXPLOITATION DES PROCEDES GEORGES CLAUDE 13 July 1973 [21 July 1972] 33630/73 Heading C1C Oxidation of dissolved mineral sulphur-containing impurities (e.g. sulphides, sulphites, thiosulphates, hydrosulphites of Na, K, NH 4 ) in industrial aqueous effluents (e.g. from paper mills, tanneries and petrochemical installations) is effected by treatment with one or more peroxy compounds selected from hydrogen peroxide, perborates (e.g. Na), percarbonates (e.g. Na), monopersulphuric acid, monopersulphates (e.g. K), dipersulphates (e.g. Na, K, NH 4 ), performic, peracetic, monoper- and diperphthalic and -isophthalic acids, and salts of said organic peracids. Hydrogen peroxide may be generated in situ from per-salts or mineral or organic perhydrates. The end-point of the treatment is determined by, or the treatment is controlled in response to, the electrochemical response of an electrode pair consisting of an active electrode (e.g. of Ag which becomes coated with Ag 2 S) and a reference electrode, e.g. calomel. The pH may be 2-12 and adjusted by addition of, e.g. NaOH. The mole ratio of peroxy compound(s) to sulphur compound(s) calcd. as S<SP>2-</SP> may be 1-8. Release of hydrogen sulphide and, in many cases, precipitation of sulphur, are avoided.