Adsorptive removal of basic yellow 2 onto reed stem and poplar leaf: A comprehensive study

The potential of reed stem (RS) and poplar leaf (PL) as low-cost, widely available agricultural wastes for adsorption of a cationic dye (basic yellow 2) from aqueous solutions has been studied. In order to optimize the biosorption process, response surface methodology (RSM) has employed. The effect of pH, temperature, dye concentration, and adsorbent dosage have determined through central composite design (CCD) and the removal efficiency of both adsorbents has compared. The interaction of variables and their impact on dye removal process was evaluated. Results indicate that for achieving the highest efficiency, RS needed an alkali environment (pH = 10.2) and a lower dosage (0.38 g), and PL needed a more moderate environment (pH = 8.88) but more dosage (0.5 g). By utilization of experimental data, the thermodynamic parameters have been calculated. Results state that adsorption by RS was endothermic (ΔH = 7.6 KJ/mol) and has a positive entropy (ΔS = 38.0 J/Kmol) while the adsorption by PL was exothermic (ΔH = ?13.06 KJ/mol) and has a negative entropy (ΔS = ?37.3 J/Kmol). Kinetic studies were conducted at five different concentrations. It has revealed that RS has better fitted to the intraparticle diffusion model and PL has followed the pseudo-second-order model at all dye concentrations except one. Using Temkin, Freundlich and Langmuir correlations, the best adsorption isotherm for each adsorbent has determined. FTIR analysis have indicated the most effective functional groups on the surface of absorbents that effectively play role in biosorption processes.