Efficient electro-assisted adsorption of pharmaceuticals by PAN-encapsulated gorse biochar

The limitations of conventional adsorption processes and the operational challenges of powdered adsorbents underscore the need for strategies that enhance pollutant removal efficiency, and enable the development of easily handled and recoverable materials. In this study, gorse-derived biochar (BG) was evaluated as an effective adsorbent for pharmaceutical removal due to its high surface area, hydrophobic nature, and surface charge distribution. Adsorption was mainly driven by π-π and hydrophobic interactions. In the case of sulfamethoxazole, the elimination efficiency increased from 43.83% under conventional adsorption to 98.37% when an electro-assisted adsorption process was applied. This improvement was preserved after immobilizing the BG in a polyacrylonitrile matrix (PAN-BG), with no significant loss ofperformance compared to the free material. Kinetic analysis suggested predominantly physical adsorption mechanisms favored by the electric field, with electro-assisted processes reporting greater efficiency, reusability and stability through the regeneration of active sites over 6 cycles. Likewise, a salting-out effect was observed when evaluating the ionic strength of PAN-BG in the presence of an electric field. Finally, the results obtained in a continuous-flow PAN-BG electro-assisted adsorption system demonstrated the applicability of the process at a larger scale. In addition, steady-state kinetic analysis, modeled using the Langmuir-Hinshelwood approach, provided insight into the joint contribution of adsorption and degradation, offering a deeper understanding about the behavior of the system. Overall, these results highlight the potential of electro-assisted adsorption processes for sustainable treatments of contaminated water, as well as the viability and scalability of biochars derived from forest residues immobilized in polymer matrices as electrosorbent materials. • PAN-biochar beads enable efficient sulfamethoxazole removal and easy recovery. • Electro-assisted adsorption boosts sulfamethoxazole removal from 44% to >98%. • Gorse-derived biochar outperforms hydrochar due to enhanced surface properties. • Electro-assisted operation sustains near-complete removal over six reuse cycles. • CSTR tests confirm scalability and relevance for wastewater treatment.