Valorization of Agroindustrial Waste: Use of Adsorbents from Peanut Shells for Removal of Paracetamol and Propranolol

Abstract The improper disposal of pharmaceuticals such as paracetamol and propranolol represent a significant environmental concern due to their high persistence in the environment and low removal efficiency by conventional wastewater treatment processes. In this context, this work aimed to develop and evaluate five adsorbents derived from peanut shells precursor for removal of paracetamol and propranolol in a binary mixture (228 and 279 nm), an application that has not yet been explored for this bioresidue. Among the produced adsorbents, phosphoric-acid-modified activated carbon (CAH3PO4) presented the best performance, achieving removal efficiencies of 99.40% and 99.47% at wavelengths of 228 and 279 nm, respectively. This result can be attributed to its high specific surface area (547 m2 g–1) and the presence of oxygenated and phosphorylated functional groups on the CAH3PO4 surface, formed through thermochemical treatment. The kinetic data were best fitted to pseudo-second order model, indicating the predominance of chemical interactions between adsorbate and adsorbent. In the equilibrium study, the data best fitted the Sips model, suggesting a surface with both homogeneous and heterogeneous adsorption sites. Thermodynamic analysis revealed that the adsorption process is exothermic, indicating spontaneous and energetically favorable interactions. These results highlight the high adsorption potential of CAH3PO4 as an effective and viable alternative for the treatment of pharmaceutical-contaminated effluents.