Development of activated carbon from Schizolobium parahyba (guapuruvu) residues employed for the removal of ketoprofen

Schizolobium parahyba species can be found in all of South America, producing several residues that can be a major opportunity to develop activated carbon. This work presents the investigation regarding the development of a high specific surface activated carbon (981.55 m² g⁻¹) and its application in the adsorption of ketoprofen from the aqueous media. The ketoprofen molecules were better adhered to the adsorbent surface under acidic conditions (pH = 2), being the ideal adsorbent dosage determined as 0.7 g L⁻¹, resulting in satisfactory values. It was found that the system reached equilibrium in 200 to 250 min depending on the initial concentration studied, achieving an adsorption capacity of 229 mg g⁻¹. The general order was the most suitable model for describing the experimental data, with an R² ≥ 0.9985 and MSR ≤ 63.40 (mg g⁻¹)². The equilibrium adsorption found that the temperature increases the adsorption capacity, achieving 447.35 mg g⁻¹ at 328 K. Besides that, the Tóth model was the most suitable for describing the isotherms R² ≥ 0.9990 and MSR ≤ 25.67 (mg g⁻¹)², indicating a heterogeneous adsorbent. The thermodynamic values found that the adsorption of ketoprofen is spontaneous (average ΔG⁰ of − 32.79 kJ mol⁻¹) and endothermic (ΔH⁰ 10.44 kJ mol⁻¹). The treatment of simulated effluent with the developed adsorbent was efficient, removing 90% of ketoprofen, ibuprofen, and salts. It was found that the adsorbent is reaming its adsorption capacity up to the 5th cycle, progressively decreasing the adsorption capacity until the adsorption does not occur past the 12th cycle. Overall, the results demonstrated that the activated carbon from residual biomass of the Schizolobium parahyba species could be an excellent alternative in obtaining an effective adsorbent to treat wastewater-containing drugs.