Adsorption of an anionic dye from aqueous solution on a treated clay

The presence of synthetic dyes in water causes serious environmental issues due to the poor water quality, toxicity to the environment and human carcinogenic effects. Adsorption has progressively become an economical and feasible method for dye wastewater decontamination. Clay minerals are an interesting alternative for removing colorants from colored aqueous solutions because they are inexpensive, easy to extract and handle, and non-toxic. In this work, a bentonite treated with H2SO4 is used to adsorb an azoderivative dye such as methyl orange (MO). The physicochemical properties of the solids were evaluated through X-ray powder diffraction (XRD), Brunauer Emmett Teller surface area analysis (BET), Scanning electron microscopy coupled with Energy dispersive spectroscopy (SEM-EDS), and Fourier transform infrared spectroscopy (FTIR). The initial dye concentration, adsorbent mass, contact time, temperature and pH influence the adsorption capacity. Acid modification of the clay increased its capacity to adsorb MO. For a concentration of 200 mg/L MO, an adsorption capacity of 125 mg/g was achieved. The adsorption process follows the pseudo second-order kinetic model. The thermodynamic study indicates that the adsorption is spontaneous and exothermic. The adsorption isotherm is best fitted to the Freundlich mathematical model. The results obtained show that, after receiving an acid treatment, clay can be effectively used to remove MO in aqueous solution.