Novel activated carbons and magnetic composites from wet olive cake for the removal of pharmaceuticals from water: Synthesis, characterization and application

Two valorization strategies were developed to convert wet olive cake into efficient activated carbons through hydrothermal carbonization followed by steam-activation. The first route involved direct steam activation of hydrochar (HSA), while the second used an acid‑mediated activation process (ASAc). An additional iron‑functionalized material (MHSA) was synthesized to obtain a magnetic adsorbent. The materials were characterized using N₂ adsorption-desorption isotherms, SEM‑EDX, elemental analysis, FTIR and Raman spectroscopy. Activation significantly increased surface area, particularly for ASAc (1175 m 2 g -1 ). The adsorption performance toward four pharmaceuticals in water was evaluated, focusing on Diclofenac (DCF) and iopamidol (IOP). The pseudo‑second‑order kinetic and Langmuir isotherm fit well adsorption data (R² > 0.99). ASAc achieved a maximum adsorption capacity of 526 mg g⁻¹ for DCF, comparable to commercial activated carbon, and an even higher value of 714 mg g⁻¹ for IOP. HSA also showed strong affinity for IOP, exhibiting a faster initial adsorption rate than for DCF. The magnetic MHSA material displayed promising removal efficiency, strongly influenced by adsorbent dosage. In binary systems, DCF adsorption was favored due to its smaller molecular size, while IOP uptake depended on micropore size and mesopore abundance. At neutral pH, the positively charged surface of the activated carbons enhanced electrostatic attraction with dissociated DCF, whereas IOP adsorption involved multiple mechanisms. Overall, these activated carbons, characterized by alkaline pH pzc and high mesopore volume, enable rapid adsorption of bulky pharmaceuticals, offering a sustainable strategy to transform wet olive cake into efficient adsorbents aligned with circular-economy principles and water-reuse objectives.