Physicochemical characterization of natural sand from the south-east of Morocco and its potential use as sorbent for dyes removal

In the present study, natural sand of Merzouga region (NSM) was investigated for the removal of textile dyes from aqueous solutions in static mode. X-ray diffraction analysis, FT-IR spectroscopy, N-2 sorption and transmission electron microscopy were used to investigate physicochemical properties of this siliceous material. The particle size distribution analysis was also used as a simple technique of particle sizing. Characterization of the natural material indicates pure and very fine-sized sand with a weak specific surface area. The effects of solution pH, initial dyes concentration, temperature, contact time and adsorbent dose on the removal of methylene blue (MB) and malachite green (MG) were studied. Results showed that the highest removal efficiency of MB and MC by NSM were performed at basic solution pH. The adsorption of the both dyes followed the pseudo-second-order kinetic model. The thermodynamic parameters obtained demonstrated that MB and MC adsorption process is feasible, spontaneous and endothermic. The equilibrium data were better described by Langmuir isotherm model. In optimal conditions, the maximum adsorption capacities of NSM using Langmuir isotherm model were 1.185 mg/g for MB and 3.144 mg/g for MG. FTIR analysis indicates that the adsorption of MB and MG onto NSM could be done with a physical adsorption. Desorption experiment using deionized water as desorbing agent revealed over 95.32% and 68.98% for MB and MG, respectively.