The present work investigated the use of Polypogon monspeliensis (PM) as an environmentally friendly and economical adsorbent for the removal of methylene blue (MB) from simulated wastewater. Both batch and column adsorption experiments were carried out to examine the adsorption performance under different operational conditions. Structural and chemical characterization of the adsorbent was conducted before and after adsorption using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. In batch studies, factors of pH, adsorbent dosage, dye concentration, contact time, and temperature were applied to evaluate the impact on the removal efficiency. Furthermore, kinetics, isotherms, and thermodynamic studies were conducted to understand the adsorption mechanism. On the other side, a fixed bed column setup was employed to investigate PM's performance in continuous mode adsorption. Results indicated that PM exhibited high efficiency in MB removal, with removal rates exceeding 80% across the conditions studied. Optimal conditions were identified to be neutral pH, moderate (0.5 g/50 ml) adsorbent dosage, low initial dye concentrations, and 30 min time. The maximum adsorption capacity is 20.2 mg/g. The kinetics of the process also show that it is a pseudo-second-order rate process, indicating chemisorption as the main mechanism of removal. The results from the isotherm also show that chemisorption is the main mechanism of MB removal, as the Langmuir and Freundlich models gave a good fit to the results. The thermodynamics of the process show that it is a spontaneous, endothermic process with increasing interface randomness with increasing temperature. In continuous-mode adsorption, PM effectively removed MB, with removal rates influenced by flow rate, initial concentration, and column height. These findings showed effective MB removal for up to 90 min; the removal rates were maintained at 96% and 94% when column heights of 10 cm and 5 cm were used, respectively, at a flow rate of 75 ml/min and a dye concentration of 20 ppm.
Ahmed et al. (Fri,) studied this question.