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Wet oxidation characteristics of metal cyanide complexes below 423 K

  • Authors
    Fukuta T.
    Agari S.
    Kuchar D.
    Kubota M.
    Onyango M.
    Matsuda H.
    Huang L.
Abstract

In the present study, the wet oxidation of zinc and copper cyanide complexes (cyanide
concentration of 1,000 mg dm-3) was conducted in a hydrothermal reactor, under oxygen
atmosphere of which the pressure was set to 1 MPa. The pH of the reaction solution was kept
in the range of 11 to 12 and the reaction temperature was changed from 383 K to 423 K. In the
experiments, mainly the effect of reaction time on the cyanide decomposition was investigated.
As a result, it was found that cyanide decomposition increased with an increase in the
temperature and cyanide decompositions of 99.9 % and 96.1 % were achieved after 8 hours at
423 K for Na2[Zn(CN)4] and Na3[Cu(CN)4], respectively. In the case of Na2[Zn(CN)4], mainly
HCOO- and NH4+ were identified as the decomposition products. By contrast, in the case of
Na3[Cu(CN)4], carbon of CN- was transformed either to H2CO3 or HCOO-, and nitrogen was
converted to NH4+, N2 or NO2-. Based on these results, the decomposition mechanisms of
Na2[Zn(CN)4] and Na3[Cu(CN)4] at a temperature of 423 K and pressure of 1 MPa were
discussed.

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