Effect of organic matter on cyanide removal by illuminated titanium dioxide or zinc oxide nanoparticles

Effect of different type of organic compounds (humic acid, oxalate, ethylenediaminetetraacetic acid, nitrilotriaceticacid, phenol) on the photocatalytic removal of cyanide with tio2 or zno was studied in this work with variation ofthe solution ph, contact time, initial cyanide concentration and type of organic compounds. photocatalyticoxidation efficiency of cyanide with tio2 was greatly affected by the solution ph. it increased as the solution phdecreased. also maximum removal of cyanide by zno was observed near at neutral ph because of the reducedphotocatalytic activity of zno at exceedingly low and high ph values originated from either acidic/photochemicalcorrosion of the catalyst and/or surface passivation with zn(oh)2. removal efficiency of cyanide greatly decreasedin the presence of humic acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid compared to that withoutpresence of organic compound because of the competitive oxidation as well as surface blocking by relatively largeorganic compounds. the oxidation pattern of cyanide was better described by first-order kinetic model. finallyphotocatalytic reaction with tio2 or zno can be effectively applied to treat synthetic wastewater contaminatedwith cyanide.