Activated carbon with composite pore structures made from peanut shell and areca nut fibers as sustainable adsorbent material for the efficient removal of active pharmaceuticals from aqueous media†

Abstract

The massive growth in the human population, along with an improved healthcare system, resulted in the discharge of a large variety of active pharmaceuticals, including antibiotics, into the water stream leading to genotoxic, mutagenic, and ecotoxicological effects on plants, animals, and human. In this study, cost-effective and environmentally sustainable activated carbon adsorbents with composite pore structures have been prepared from agricultural waste materials, peanut shells and areca nut fibers, through a facile method. Phosphoric acid (H₃PO₄) of two different concentrations (20% and 40%) was used for preparing the activated carbons. All the activated carbon samples showed reasonably high specific surface area (SSA) ranging between 580–780 m² g⁻¹. The SSA of the activated carbon obtained from peanut shells was higher than those obtained from the areca nut fibers. The adsorption characteristics of the prepared activated carbons were assessed for the common active pharmaceuticals, paracetamol, amoxicillin, and aspirin, in an aqueous medium. The rate of adsorption of the activated carbon was very high, and about 90% of the paracetamol was adsorbed within 5 min of contact. The adsorption kinetics followed a pseudo-second-order kinetic model. The paracetamol adsorption capacity of the activated carbons obtained from the Langmuir adsorption isotherm (monolayer) model was 67 mg g⁻¹. Regeneration and reuse of the adsorbent for the removal of paracetamol were also studied for up to 5 cycles. The present research work ensures the “3 Rs” principle [reduce (waste), reuse and recycle] of environmental sustainability.