Sol–gel synthesis of vanadia–silica for photocatalytic degradation of cyanide

Cyanides used in some chemical synthesis and metallurgical processes are highly toxic and must be destroyed or removed from wastewaters prior to discharge. Vanadia–silica xerogel as photocatalyst has been prepared via sol–gel technique by dissolving ammonium metavanadate (AMV) and tetraethylorthosilicate (TEOS) and applied for photodegradation of cyanide from solution. The optimum conditions for preparation of V2O5–SiO2 gel is 1:1 of vanadium/silicon (V/Si) molar ratio and TEOS:H2O:C2H5OH is 1:8:4 mole ratios at 30 °C for 10 min, at these conditions the photoactivity of V2O5–SiO2 was 98.5% at surface area 310 m2/g. The calculated activation energy of the reaction between AMV and TEOS was found to be −10.81 kcal/g. The optimum loading of vanadia–silica xerogel was 0.166 wt.% that give 98.5% cyanide removal efficiency after 3 h. The overall kinetics of photodegradation of cyanide using vanadia–silica photocatalyst was found to be of first order.