Degradation of free cyanide by photocatalytic oxidation

I.A. Ibrahim, A.A. Ismail* and R.M. Mohamed

Central Metallurgical R&D Institute, CMRDI, P.O.Box 87 Helwan, Cairo, Egypt

Received 21 January 2002; accepted 15 December 2002


Gold is normally recovered from its ores by cyanidation process, which is a well-known technique used worldwide. The merits of cyanide heap leaching technology of gold are well known, but environmental problems arise occasionally due to high toxicity of cyanide. Photocatalytic decomposition of cyanide was achieved using TiO2-SiO2 aerogel, V2O5-SiO2 xerogel or ozone. The cyanide removal efficiencies were increased from 87 to 98.74% and from 85 to 99% by increasing loading wt. % from 0.083 to 0.666 and from 0.083 to 0.166 for TiO2-SiO2 aerogel and V2O5-SiO2 xerogel respectively. Also, the rates constant were increased from 0.020 to 0.044 min-1 and from 0.022 to 0.045 min-1 for TiO2-SiO2 aerogel and V2O5-SiO2 xerogel respectively and the reaction kinetics were found to be first order. On the other hand the optimum conditions of Photocatalytic degradation of cyanide using ozone were found to be 2.5 wt. % ozone concentration, 1.14 m3/h airflow as well as 36 Watt (W) UV light power . At these conditions, the cyanide removal efficiency was 99%, the rate constant was found to be 0.0075 min-1 and the reaction kinetic was found to be first order.

Keywords: Cyanide; Photocatalytic; Degradation; TiO2; V2O5; Ozone

* Corresponding author
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