Mechanochemical synthesis of N-doped porous cyanobacteria-based biochar for decontamination of antibiotic wastewater

N-doped porous cyanobacterial-based biochar (N-PBC) was synthesized via ball milling coupled with pyrolysis and demonstrated as a high-performance adsorbent for enrofloxacin (ENR) removal. Compared to raw biochar (BC, 25.06 mg g⁻¹), N-PBC exhibited a significantly enhanced adsorption capacity of 51.02 mg g⁻¹ (adsorbent dosage 0.05 g L⁻¹, 298 K), corresponding to removal efficiencies of 22.48 % and 12.17 % for N-PBC and BC, respectively. Adsorption kinetics for both biochar followed the pseudo-second-order model, suggesting chemisorption-dominated mechanisms, while isotherms aligned with the Langmuir model, indicating monolayer adsorption. Thermodynamic analysis confirmed the spontaneous and endothermic nature of ENR adsorption. N-PBC maintained stable adsorption capacity across varying pH conditions and in the presence of common anions, alongside excellent regeneration performance. This study innovatively transforms cyanobacterial waste into functional N-doped biochar, showcasing its superior design for active sites and surface area. The findings underscore cyanobacterial waste biochar significant potential as a sustainable, efficient adsorbent for antibiotic remediation in water treatment applications.