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

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 method s. 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. I f the distillation time is prolonged to 2 h, the cyanide determination is q uantitative. Results of these modifications of the German standard method w ere 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 + 0.991x; r = 0.996; n = 32). On an a verage, in the first extract 85%, in the second extract 12%, and in the thi rd extract 3% of total cyanide was dissolved. Determination of total cyanid e in deposited blast furnace sludge can be performed by an acid digestive d igestion of solid material for 2 h as well as by a repeated extraction by m eans of 1 M sodium hydroxide. (C) 2001 Elsevier Science B.V. All rights res erved.