Magnetic Fe 3 O 4 -modified mangrove biochar for adsorptive removal of 2,4,6-trichlorophenol

2,4,6-Trichlorophenol (TCP) is a persistent organic pollutant with low biodegradability. Mangrove leaf biomass was pyrolyzed at 650 °C and functionalized with Fe₃O₄ nanoparticles through in situ co-precipitation to produce a magnetic biochar composite. XRD, FTIR, SEM–EDX, and BET analyses confirmed Fe₃O₄ incorporation while preserving the biochar’s mesoporous structure. Batch experiments demonstrated enhanced TCP adsorption compared with pristine biochar, with removal exceeding 90% under optimized conditions. Equilibrium was reached within approximately 90 min, and adsorption kinetics were adequately described by both pseudo-first-order and pseudo-second-order models. Equilibrium data fitted the Freundlich isotherm better, suggesting heterogeneous adsorption sites. The maximum adsorption capacity was approximately 2.58 mg g⁻¹. Adsorption likely involved π–π interactions, hydrogen bonding, and pore filling. Although the composite remained magnetically recoverable, adsorption efficiency declined sharply after the second regeneration cycle, reaching approximately 20% by the fifth cycle. These findings demonstrate the potential of magnetically functionalized mangrove-derived biochar as a readily separable adsorbent for TCP removal. However, improved regeneration stability is needed for repeated practical application.