Poly(ethylenimine) modified Punica granatum derived biochar for antibiotic removal: mechanistic insights

A sustainable polymerized base-activated biochar (PBC-B) derived from Punica granatum peel and surface activation and polymerization with branched poly(ethylenimine) were prepared and demonstrated efficient tetracycline (TC) remediation from wastewater. Polymerized acid-activated biochar (PBC-A) and pristine biochar were also evaluated for comparison. The PBC-B exhibited enhanced porous morphology and surface functional groups, effectively improving TC adsorption. Results indicated that PBC-B has a Langmuir adsorption capacity of 295.9 mg g⁻¹ and a partition coefficient of 18.67 mg g⁻¹ µM⁻¹, manifesting that surface activation and polymerization lead to well-developed pore structures. The PBC-B showed a 19.59 and 75.39% improvement in TC adsorption compared to PBC-A and BC, respectively. Adsorption isotherm studies revealed that the Langmuir model described the strong adsorption behavior with a high adsorption capacity (Q_L = 295.9 mg g⁻¹) and R² (0.98) for PBC-B. Kinetic studies indicated that the pseudo-second-order model fits well, with a low sum of squared error values (< 4.4 × 10⁻³) and high R² values (0.99). This study pioneers the use of PBC as an adsorbent with reduced organic compound content while elucidating the TC adsorption mechanism in aqueous phases, marking a significant advancement in the field. Density functional theory evidenced that chemisorption mechanism predominates in the interaction between TC and PBC.