Recent Advance in
Cyanide Waste Reduction Practice
ROBERT H. L. HOWE, Sanitary Engineer
Eli Lilly and Company
Lafayette, Indiana
INTRODUCTION
This paper is intended to discuss the recent advance in cyanide waste reduction
practice. Some of the new achievements have been based on a few classic hypotheses reported quite a number of years ago. In order to present the background
of these "new" methods of cyanide waste reduction and detoxication, a brief review of some literature will first be discussed.
During the last twenty years, a large number of papers concerning cyanide
waste reduction has been published. Simple cyanide had been detoxicated by
acidification, neutralization and chlorination, according to Tarman (1), White(2),
Kesslor (3), Dobson (4), Zubban (5) and Chamberlin (6). Ozonation of cyanide
wastes has been reported by Zubban (5) and Milne (7). Catalytic oxidation of cyanide was discussed by Ehler (8). Electrolytic oxidation process for cyanide wastes
reduction was reported by Oyler (9) and others (10). Bloodgood et al. (11) discussed the use of ion exchange process for cyanide reduction. Pettet(12) described
the effects of cyanides on tile percolating filter of sewage treatment. Ridenour
(13) discussed the effect of cyanide on activated sludge process. Gurnham and
others (14,15) investigated the application of biological filtration for cyanide
waste treatments. Ludzack et al. (16,17) reported the effect of organic cyanides
on conventional sewage treatment methods and also discussed the activated sludge
treatment of cyanide, cyanate and thiocyanate. Nesbitt (18) discussed his work on
the aerobic metabolism of potassium cyanide by activated sludge. More recently,
Brink (19) revealed some data of experimental work on the biological decomposition of cyanides by biological filtration. Howe, Paradiso, and Wollenweber (20)
disclosed some applicational data on the reduction of cyanides with the aid of digested sludge. Bahensky (21) suggested the use of calcium permanganate for cyanide reduction. Also, attfield reported the oxidation of aqueous hydrogen cyanide
by hydrogen peroxide (22).
Undoubtedly, there are still other publications which also deal with the reduction of cyanides. However, in this presentation, the author intends to cite only
the above as the introduction to some recent accomplishments in cyanide wastes
reduction.
CHEMICAL REACTIONS IN CYANIDE WASTES REDUCTION
Summarizing the literature cited, the basic chemical reactions can be outlined as follows:
Acidification and Neutralization
NaCN + H+ —Na+ + HCN f
NaCN + S02 + HgO —NaHS03 + HCN*
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