H2o

The electrode potential of the cyanide waste solution is — 200 to —400 mV. After sufficient chlorine is applied to complete the reaction according to Equation 7.42(2), the electrode potential is +200 to +450 mV. The potential value does not increase until all cyanide is oxidized. Control of the pH is essential, with the minimum being 8.5. The reaction rate is faster at higher values.

Complete oxidation (destruction of cyanide) is a two-step reaction. The first step is oxidation to the cyanate level as described in Equation 7.42(2). The endpoint of the second-stage reaction is again detected by electrode potential readings and is + 600 to + 800 mV. The overall reaction

is as follows:

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