Adsorption of Cyanide from Aqueous Solutions Using Magnetic Hydroxyapatite Nanoparticles Synthesized by Hydrothermal Method: Equilibrium and Kinetic Study

Cyanide is a toxic compound widely used in different industries (e.g. metal extraction) and enters into the environment through such activities. In present work magnetic hydroxyapatite nanoparticles were synthesized hydrothermally and used for removal of cyanide from aqueous solutions. Experimental parameters influencing the process such as solution pH, initial cyanide concentration, nanoparticle concentrations, and contact time were studied. In addition Langmuir and Freundlich isotherm models, pseudo-first-order, pseudo-second-order, and modified pseudo-first-order kinetic models were applied for describing the process. Restoration of used sorbent was also investigated. Maximum removal efficiency was observed at 10 mg/L of cyanide concentration, 0.8 g/L adsorbent mass, 120 min contact time, and pH=4. Under these conditions more than 92% of cyanide ions were removed. Results of isotherm study showed that trend of cyanide ion sorption to follow Langmuir model (r2=0.998). In addition, kinetic of cyanide sorption was best described by pseudo-second-order kinetic model (r2=0.999). 70% of the used sorbent can be conditioned by 1 N NaOH solution. The results of present work well demonstrate that nano magnetic adsorbent to have high ability to remove cyanide pollutant.