Method comparison for the determination of total cyanide in deposited blast furnace sludge

Abstract

Blast furnace sludge is a cyanide-containing waste created during pig iron production. In this study the determination of total cyanide in 32 samples of a disused blast furnace sludge deposit was investigated using two methods. One method is based on a weight-in of solid material followed by an acid digestive distillation. If using a distillation time of 1 h, which is laid down in Germany as the standard method, total cyanide is underestimated. If the distillation time is prolonged to 2 h, the cyanide determination is quantitative. Results of these modifications of the German standard method were statistically equal to those obtained by an alkaline extraction using 1 M sodium hydroxide repeated three-fold, and followed by an acid digestive distillation of the extracts ( y=8.4+0.991 x; r=0.996; n=32). On an average, in the first extract 85%, in the second extract 12%, and in the third extract 3% of total cyanide was dissolved. Determination of total cyanide in deposited blast furnace sludge can be performed by an acid digestive digestion of solid material for 2 h as well as by a repeated extraction by means of 1 M sodium hydroxide.