(WALSIMBook)DESTRUCTION OF CYANIDE BY A PHOTOCATALYTIC TECHNIQUE AND RECOVERY OF ANATASE PARTICLES BY ELECTROCOAGULATION

摘要

Due to the widespread use of cyanide in mining operations, the recovery and destruction ofcyanide is important both from the environmental aspects of wastewater and effluent treatment and fromthe economic aspects associated with the high reagent consumption by the process itself. Aphotoelectrocatalytic detoxification technique with titanium dioxide microelectrodes is one of the mostinnovative ways for the treatment of wastewater containing cyanide. However, this technique has adisadvantage for industrial application; the separation of titanium dioxide after the photocatalyticdegradation of cyanide is rather difficult due to fineness of the particle and, therefore, the reuse of thetitanium dioxide has not been used for the treatment of cyanide-containing wastewater. To alleviate thisweak point, an Electrocoagulation (EC) technique was used to recover the titanium dioxide from itsaqueous suspensions. The process was studied under various parameters: cyanide concentration, TiO_2concentration, current density values and other operational conditions. The results show thatphotodegradation of cyanide was 93 % in 30 minutes using a 450 W halogen lamp. The recovery ofanatase with the EC process was 98 %. The results indicate that this technique has the potential to serve asa reliable and economical method because sunlight could be used efficiently as the source power.Langmuir isotherms were used to obtain the thermodynamic parameters such free energy, enthalpy andentropy, the evaluation of this parameters (ΔG°= -37 kJ/mol, ΔH° = -54 kJ/mol and ΔS° = 0.524 kJ/mol K)indicated a spontaneous and exothermic nature of the adsorption of anatase particles on the iron species.