Wild reed waste as a biosorbent for toxicity lowering of selected pollutants: Isotherms, kinetic and thermodynamic studies

Abstract

Wild reed (Raw-Mat) was used as an eco-friendly biosorbent to remove two basic dyes, Rhodamine B (Rh-B) and Methylene blue (MB), from their aqueous solutions. The prepared biosorbent was characterized by scanning electron microscopy (SEM), X-ray diffraction, thermogravimmetric analysis (TGA), FT-IR spectroscopy, pHzpc, Iodine number, and Methylene Blue index. Adsorption experiments were conducted by studying the effect of conventional parameters (biosorbent dose, contact time, pH, ionic strength and temperature). Adsorption equilibrium was reached at 60 min for MB and 120 min for Rh-B at biosorbent doses of 12 g/L and 8 g/L for MB Rh-B respectively corresponding to maximum adsorption capacities of 29 mg/L and 27.9 mg/L. Adsorption models of Langmuir, Freundlich and Temkin in their linear and nonlinear were fitted to the experimental data. Ionic strength effects indicated that hydrophobic-hydrophobic interactions could be the dominant attractive force for adsorption of both dyes. Dye uptakes increased with temperature for both dyes. Adsorption kinetics was found to comply with the pseudo second order with a good correlation factor (R2 > 0.99) with intra-particle diffusion as the rate determining steps. Both dyes adsorption processes were spontaneous (ΔGo <0) and endothermic (ΔHo >0). This study showed that wild reed as a waste could prove to be a very efficient adsorbent in removing toxic substances from wastewater.