Optimum condition determination of adsorption capacity and adsorption percentage of cyanide ions using activated red mud

In this study, removal of ferrocyanide and ferricyanide ions from synthetic wastewater with activated red mud was studied. Two activation methods by ammonia (ABA) and cationic surfactant of cetyl trimethylammonium bromide (ABC) were used. In order to evaluate the process of cyanide ion adsorption and its effective parameters, 44 experiments were designed with seven variable factors using DX8 software by the response surface method. The results showed that the optimum conditions for achieving the highest adsorption capacity with ABC adsorbent were obtained as follows: pH=7.1, adsorbent dosage of 0.57 g, ferricyanide concentration of 126 ppm, contact time of 96.66 min, agitated speed of 120 rpm and ion strength of 0.24 M. In optimum conditions, the absorption capacity of 19.5 mg/g and the absorption percentage of 99.3% were obtained. The results showed that the use of ABC adsorbent has a higher efficiency in the removal of cyanide ions from the synthetic wastewater. Thermodynamic studies were carried out in optimal conditions. The results showed that the negative value of ΔG◦ parameters at different temperatures indicates the spontaneity of the cyanide complex adsorption process on adsorbents of ABA and ABC. The spontaneity of process increased with increasing the temperature.