The determination of cyanides in steelworks effluents with a cyanide-selective electrode

Abstract

Conventional methods for the determination of cyanide in effluents associated with steel-making procedures are compared with a method based on a cyanide-selective electrode. For cyanide levels above 1.0 mg l -1, the standard argentimetric titration and electrode method give similar results. At lower levels (0.1–1.0 mg l -1 and 0.01–0.10 mg l -1), the potentiometric method is compared with pyridine-pyrazolone and pyridine—barbituric acid colorimetric procedures; the pyrazolene method tends to give higher results than the other two methods. Synthetic standards and actual effluent samples are discussed. Problems associated with the determination of cyanide in effluents containing complex iron cyanides and sulphides are examined. Sulphide removal with lead carbonate or cadmium carbonate above pH 11 should not be done until after the distillation.