Thermodynamic, equilibrium, and kinetic studies of safranin adsorption onto carpobrotus edulis

In the current study, carpobrotus edulis were used to prepare three adsorbent surfaces; (dry adsorbent material, DAM), (hot activated carbon, HAC), and (acid activated carbon, AAC), and applied for safranin dye removal as a function of pH, contact time, adsorbent dose, initial dye concentration, and temperature. The ideal pH for DAM, HAC, and AAC efficient adsorption were 7-11, 7-9, and 5-11, respectively, employing an adsorbent dosage of 0.10 g and contact time of 30, 40, and 90 min, respectively. Furthermore, the adsorption processes were better explained by the pseudo-second-order-kinetic model. It was also noticed that the safranin adsorption process demonstrated a favorable agreement with Freundlich isotherm for the three adsorbents with maximum calculated adsorption capacities of 47.49, 44.18, and 46.72 mg/g for DAM, HAC, and AAC, respectively. The results of the thermodynamic study revealed the exothermic nature of dye adsorption onto DAM and AAC and the endothermic nature onto HAC. Finally, results demonstrated that the studied surfaces are efficient adsorbents and could likely be utilized for dyes adsorption.