*7.2.2.3. Electrowinning*

Strong acid dissociable and weak acid dissociable cyanide complexes can be reduced to metals releasing free cyanide (Eq. (16)) by the application of an electric potential across electrodes immersed in complexes solution. The freed cyanide can then be treated by other processes.

$$\left[\mathsf{M}(\mathsf{CN})\_{\mathsf{y}}\right]^{\mathsf{x}\cdot\mathsf{y}} + \mathsf{x}\mathsf{e}^{-} \to \mathsf{M} + \mathsf{y}\mathsf{CN}^{-} \tag{16}$$

Four electrowinning cell designs have been developed for gold processing, namely Zadra, AARL, NIM graphite chip and MINTEK parallel plate cells [54, 58]. Electrowinning performs well in concentrated solutions and has been predominantly utilised for gold processing. This process is termed as Celec or HSA process [59] when it is used for cyanide regeneration.
