1070-4272/01/7409-1509$25.00C2001 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 74, No. 9, 2001, pp. 1509!1512. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 9,
2001, pp. 1466!1469.
Original Russian Text Copyright + 2001 by Kharchenko, Agapov, Vorob’ev-Desyatovskii.
OF CHEMISTRY AND TECHNOLOGY
Detoxication of Aqueous Cyanide Solutions with Oxygen
in the Presence of S(IV) and Cu(II) Compounds
D. V. Kharchenko, I. A. Agapov, and N. V. Vorob’ev-Desyatovskii
Navy Engineering Institute, St. Petersburg, Russia
Received June 18, 2001
Abstract-Oxidation of cyanide anions with atmospheric oxygen in aqueous solutions in the presence of
mixture and CuSO
as a catalyst was studied. The reaction mechanism was proposed.
Cyanide solutions are widely used in electroplating
and mining. Usually they contain from hundreds of
milligrams to tens of grams per liter of NaCN and
cyanide complexes of transition metals [Cu(I), Zn(II),
Cd(II), Ni(II), Fe(II), Fe(III), Cr(III), etc.] and also
some impurities like NH
[1, 2]. Detoxication of these solutions is an
important task, which can be solved by numerous
ways. In general there are six main approaches to this
problem [3, 4].
(1) The passive detoxication is based on the reduc-
tion in the concentrations of free and coordinated CN
ions in solutions upon prolonged staying under natural
conditions owing to a combination of photolysis, oxi-
dation (including biological oxidation), precipitation
(in the case of complex ions), and hydrolysis caused
by gradual pH reduction on the dilution of solutions
by rain and water from thawed snow and by salt
freeze-out in wintertime.
(2) Distillation of HCN from acidified solutions
and its subsequent sorption by alkaline solutions.
(3) Sorption of CN ions and complex cyanide
anions on activated carbons in the presence of Cu(II)
compounds and on ion-exchange resins.
(4) Electrochemical anodic oxidation of free and
bound in relatively weak complexes CN
oxidation can be either direct or can accompany anod-
ic oxidation of chloride ions if they are present in
the same solution.
(5) Biological transformation (oxidation and hy-
drolysis) of free and bound cyanides with the use of
microbial biocenoses (associations of aerobes and
anaerobes in the form of activated sludge), biosor-
bents, immobilized microorganisms, or specific bac-
terial enzymes (rhodonase and cyanide hydratase).
(6) Reagent detoxication, which can be subdivided
into binding of CN
ions in nondissociated or difficul-
ty soluble compounds [treatment with CH
salts] and oxidation of free and bound CN
elemental chlorine in an alkaline medium or with cal-
cium (or sodium) hypochlorite prepared in advance,
and also with hydrogen peroxide in the presence of
Cu(II), with ozone or atmospheric oxygen in systems
containing aqueous solutions of S(IV) and Cu(II)
compounds (INCO and Noranda processes).
The use of each of these methods is determined by
climatic and economical conditions and also by local
legislation regulating wastewater discharge. Recently
the detoxication of free and bound cyanide ions by
their oxidation with atmospheric oxygen bubbled
through aqueous solutions of S(IV) and Cu(II) com-
pounds received growing use in cold-climate coun-
tries. However, the information on this method can be
found only in patents and special mining literature,
and available data  give no way of developing
the method because they cannot reveal its chemical
essence and potential. In this work we studied the
detoxication of cyanide solutions obtained after elec-
trochemical deposition of noble metals from agitation
cyanide leaching solutions of concentrates of Dukat
ore mining and concentrating enterprise. The solution
composition is given below.
We tested Na
and its mixture with Na
as a source of S(IV). Weighed samples of solid salts
were placed into a 0.5-l sample to be neutralized, and
then 0.11 g of the catalyst CuSO
O was added.
The flask was closed, and air was blown through it
with a rate of 2.5 l min
. The residual concentrations
ion and other simple and complex ions were
determined 1 h after the start of detoxication.