Abstract

Cyanide is a toxic pollutant found in different industrial wastewater, and wastewater of these industries is discharged to the environment without any treatment. The main aim of this research was to remove cyanide from aqueous solutions using bleaching earth adsorbent recycled from vegetable oil industries. In this study, Regenerated Spent Bleaching Earth (RSBE) obtained from vegetable oil industries was used to remove cyanide from aqueous solutions. Effects of pH, cyanide initial concentration, contact time and adsorbent dose were investigated in a batch reactor. The optimum conditions obtained in this study on Kerman coke industry wastewater were also examined. Finally, kinetics and isotherms of cyanide adsorption were analyzed. Results showed that the regenerated bleaching earth with a concentration of 1 N NaOH had a higher adsorption capacity than other regenerated agents. The maximum cyanide adsorption was achieved at a pH of 7 and a contact time of 140 minutes. As cyanide initial concentration increased, adsorption rate increased but removal efficiency decreased. Moreover, as adsorbent dose increased, removal efficiency increased but adsorbent capacity decreased. The effect of bleaching earth on coke industry wastewater in optimal conditions revealed that cyanide removal rate was 86. The data of this research had the greatest conformity with Langmuir-2 isotherm. The maximum adsorption capacity of cyanide on RSBE was 13 mg/g. In addition, Elovich was the most appropriate model to determine the reaction kinetics. The results of this study showed that treatment costs of cyanide-containing wastewater could be reduced by regenerating this industrial waste.