Removal of Evans Blue dye from aqueous solution using magnetic spinel ZnFe2O4 nanomaterial: Adsorption isotherms and kinetics

Magnetic nano crystalline ZnFe2O4 was successfully synthesized by simple combustion route using oxalyldihydrazine as fuel and the material formed was characterized by powder X-ray diffraction, Fourier transform infra-red spectroscopy and scanning electron microscope. Surface area measurements (90.004 m2 g−1) were done using Brunauer–Emmett–Teller analysis. Magnetic measurements done using vibrating sample magnetometer shows that ZnFe2O4 nanoparticle is superparamagnetic. Adsorption capability of the as prepared nanospinel ZnFe2O4 was measured for the removal of Evans Blue, an anionic dye by batch adsorption process. Parameters like adsorbent loading, initial dye concentration and stirring effects were carried out at neutral pH and room temperature. Spinel ZnFe2O4 nanoparticles showed good adsorptive capacity and the maximum monolayer coverage (Q0) was determined as 46 mg/g of the adsorbent. The data were analyzed by three different kinetic models viz; Lagergren pseudo first order, pseudo second order and Intraparticle diffusion models and by various isotherm models like Langmuir, Freundlich and Temkin models to study the mechanism of adsorption process. Kinetic study shows that it follows pseudo second order with highest R 2=0.998 and the rate determining step was found to be intraparticle diffusion. Isotherm studies shows that the adsorption of EB is highly favorable and the value of Temkin constant, AT = 0.5445 and heat of adsorption, B = 14 J/mol indicates that the adsorption process is exothermic and physical in nature.