Removal of Malachite Green from Aqueous Solution by Zeolite- Iron Oxide Magnetic Nanocomposite

Discharge of dye effluents into the natural streams may be toxic to the aquatic lives as well as human being. In the present studies, zeolite was synthesized from coal fly ash by alkaline hydrothermal treatment and mixed with magnetite nanoparticles in suspension to produce zeolite-iron oxide magnetic nanocomposite. It was used as adsorbent for the removal of malachite green dye from aqueous solution. Magnetite nanoparticles in suspension were synthesized by precipitating iron ions in a NaOH solution. The morphology of nanocomposite was characterized by XRD, EDX and SEM. The effect of various experimental parameters such as contact time, pH, adsorbent dose and temperature were investigated. Batch study revealed that the adsorption of malachite green (MG) was strongly pH dependent and maximum dye removal was found to occur at an equilibrium pH of 8.0. Optimum adsorbent dose, contact time and temperature were found 5 g/l, 60 minutes and 303 K respectively. Effect of varying initial malachite green concentration was also investigated to study the removal efficiency of adsorbent. Kinetic studies were performed to have an idea of the mechanistic aspects and to obtain the thermodynamic parameters of the process. The adsorption of malachite green onto nanocomposite followed pseudo-first-order kinetics. Adsorption data were also correlated with both Langmuir and Freundlich isotherm models. Results indicated that according to the Langmuir and Freundlich isotherms, the maximum sorption capacities are 21.05 and 5.01 mg·g/1 for malachite green respectively. Thermodynamic parameters ∆G, ∆H and ∆S were calculated as -3.1913 kJ/mol, -14.13 kJ/mol and -0.038 kJ/mol/K respectively indicating that process of adsorption is exothermic and spontaneous in nature. The results indicated that zeolite from fly ashiron oxide magnetic nanocomposite, was a potential adsorbent for field application in removal of contaminants from aqueous solution.