Removal of cyanide from aqueous solutions using natural zeolite modified with cationic surfactant

Cyanide is one of the most important and harmful pollutants released to the environment and as a result of industrial activities, aquatic environments are the most important route for exposure of living organisms to this pollutant. This research aimed to study the adsorption of cyanide by raw zeolite and modified zeolite with surfactant. Using the cationic surfactant of hexadecyltrimethylammonium bromide, the raw zeolite was modified. After the determination of prepared adsorbent properties and isothermal experiments, kinetics, the effect of pH, and the ionic strength of the stock solution was measured by batch tests. The XRD results confirmed the presence of clinoptilolite mineral in the structure of the raw zeolite and the surface coating of raw zeolite by surfactant after modification was observed by SEM images. The Langmuir, Freundlich and, Tamkin adsorption models showed an excellent ability to describe the cyanide adsorption isotherm using the studied adsorbent. The adsorption capacity of cyanide by modified zeolite was 3.97 mg /g, which is significantly increasing compared to the maximum adsorption capacity of raw zeolite cyanide (0.54 mg /g). Modelling of kinetic data showed that pseudo first-order and pseudo second-order models have an excellent ability to describe the adsorption kinetics of cyanide contaminants using natural and modified zeolites. Cyanide removal by surfactant-modified zeolite decreased with increasing pH and ionic strength of the stock solution. The results of this study showed that the modification of zeolite with surfactant could be used as a non-toxic and efficient adsorbent to remove cyanide from aqueous solutions in the bed of the tailings dams of the Zareshoran mine processing plant in Takab city of West Azerbaijan province of Iran.