Novel carbon-based materials for sustainable water treatment: Perfluorooctanoic acid adsorption and adsorbent regeneration via thermally activated persulfate oxidation

Rapid increases in municipal and industrial waste pose significant environmental challenges, prompting the need for sustainable technologies. This study reports a framework that combines the production of adsorbents with value-added processes to be used in the remediation of water streams polluted by perfluorooctanoic acid (PFOA) as a target compound. This framework is based on adsorption and regeneration cycles using thermally persulfate-activated advanced oxidation process. Carbon-rich waste, including olive pomace and urban plastic residues, was used to synthesize five carbonaceous materials—activated carbon, hydrochar, pyrochar, activated carbon from hydrochar, and carbon nanotubes—via hydrothermal carbonization and pyrolysis. The adsorbents demonstrated PFOA adsorption capacities ranging from 55 to 303 mg·g⁻¹, with activated carbon achieving the highest (303 mg·g⁻¹) due to its microporous structure. Adsorption equilibrium followed the Langmuir model, while adsorption kinetics were best described by a pseudo-second-order model. Regeneration was performed using thermally activated persulfate at 60°C. Activated carbon recovered over 70% of its adsorption capacity with lower oxidant consumption, whereas hydrochar and carbon nanotubes exhibited higher oxidant use and greater structural changes. These results underscore the potential of waste-derived carbon materials for sustainable water treatment and circular economy applications, providing effective removal of persistent pollutants like PFOA with great promise. • Solid wastes into value-added adsorbents via pyrolysis and hydrothermal methods. • Active carbon and hydrochar showed high perfluorooctanoic acid (PFOA) adsorption performance. • Successful PFOA adsorption-regeneration cycles with high material recovery. • Thermal persulfate at 60°C effectively degraded adsorbed PFOA. • Adsorbents retained structure and capacity after regeneration cycle.