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 30degreesC for 10 min, at these conditions the photoactivity Of V2O5-SiO2 was 98.5% at surface area 310 m(2)/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 0.166wt.% 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. (C) 2003 Elsevier Science B.V. All rights reserved.