Modification of bentonite surface with magnetite nanoparticles for removal of Reactive yellow dye from aqueous solutions

Clay minerals are among the mostly used minerals in numerous applications. The term bentonite as an aluminium silicate compound is used in the industry for clays mostly composed of smectite group minerals. Nano-sized materials have superior physical and chemical properties due to their mesoscopic and surface effects. Recently, magnetite nanoparticles (Fe3O4 MNPs) have been intensively investigated because of their superparamagnetic, non- toxicity, high coercivity, low Curie temperature and biocompatibility properties [1]. The present study deals with the development of an innovative cost effective bentonite adsorbent modified with Fe3O4 MNPs for the removal of Reactive yellow anionic dye from aqueous samples. For this propose, bentonite/Fe3O4 nanocomposites were synthesized via a co-precipitation method with addition of ammonium hydroxide to a solution of Fe2+/Fe3+ in the presence of bentonite [2]. The structure, magnetic property and morphology of the prepared composite were investigated by Fourier transform infra-red spectroscopy (FT-IR), vibrating scanning magnetometer (VSM), X-ray diffraction (XRD) and scanning electron microscope (SEM) instruments, respectively. Experimental factors affecting the removal of Reactive yellow dye such as pH, ionic strength, adsorbent dosage and contact time were studied using orthogonal array design (OA16). Under the optimum conditions (solution pH= 8.5, NaCl concentration: 0.1 mol L-1, contact time: 40 min and adsorbent dosage: 0.1 g), the removal efficiency higher than 86% was obtained. The adsorption kinetic was studied using two different concentrations of Reactive yellow (15 and 100 mg L-1) via four kinetic models including pseudo-first-order, pseudo-second-order, intra-particle diffusion and Elovich models. The data were obeyed from pseudo-second-order kinetic model (R2 = 0.9997, qe=24.69 mg g-1). Also, three well-known isotherm models (Langmuir, Freundlich and Tempkin) were studied in the optimized conditions. Finally, the applicability of magnetite modified bentonite composite for removal of Reactive yellow dye from real aqueous samples was successfully investigated. The results indicated that modification of bentonite surface by magnetite generates an adsorbent with suitable adsorption capacity for removal of dyes like Reactive yellow from aqueous solutions.