Kinetic and isotherm studies on the removal of reactive Red 2 from aqueous solutions using phosphoric acid activated carbon


 In the current study, an alternative precursor for the production of activated carbon (AC) is introduced using grape wood. The AC structures and functional groups were studied using a scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). The efficiency of prepared AC has been investigated in the removal of Reactive Red 2 (RR2) from an aqueous solution. The effect of main variables, namely dye concentration (100–500 mg L−1), contact time (10–90 min), adsorbent dosage (0.25–12.25 g L−1), and initial pH (3–11) have been assessed on the adsorption process in order to find out the optimum conditions. Langmuir, Freundlich, and Temkin adsorption isotherm models were applied to describe the characteristics of adsorption behavior. Kinetic data were fitted to pseudo-first-order, pseudo-second-order, and intra-particle diffusion models. Based on the results, the highest removal efficiency (97.96%) of RR2 dye was obtained at an initial concentration of 100 mg L−1, adsorbent dose of 12.25 g, contact time of 90 min, and pH 3, which indicated a significant sorption efficiency. The rate of the adsorption fitted well to a pseudo-second-order kinetic model (R2 = 0.99). In addition, the Temkin adsorption isotherm model was found to fit the experimental data (R2 = 0.99).