Magnetic zero valent nickel nanoparticles composite with algal-derived biochar for superior removal performance toward phenanthrene

Nano zero-valent nickel nanoparticles (Ni 0 NPs) were successfully immobilized onto Enteromorpha -derived biochar to enhance the removal of polycyclic aromatic hydrocarbons (PAHs) from aqueous solutions through an integrated adsorption-magnetic recovery process. Comprehensive characterization techniques revealed the uniform dispersion of Ni 0 NPs on the biochar surface, with particle sizes predominantly ranging from 60 to 100 nm. The synthesized composites (HTNF@Ni 0 ) exhibited an exceptional specific surface area of 1388 m 2 /g, which contributed to its outstanding phenanthrene removal performance, achieving a maximum adsorption capacity of 248.54 mg/g. The experimental data were well-fitted by pseudo-second-order kinetics and Langmuir isotherm adsorption model. Moreover, the magnetic composite demonstrated excellent regeneration properties and stability in phenanthrene removal after four consecutive cycles. Additionally, the optimized structure, charge distribution, LUMO-HOMO energy gap (E GAP ), and adsorption energy of the composite indicated strong π-π interactions and charge transfer between active functional groups (e.g., –OH, −NHR, –COOH, −C–OH), particularly the electron donor–acceptor interaction between metallic Ni 0 nanoparticles and target contaminants. The interaction was confirmed as an exothermic process, predominantly governed by chemical adsorption mechanisms. This study provides novel insights into the development of innovative magnetic composites and their potential for practical applications in wastewater treatment.