Adsorptive removal of ofloxacin from the aqueous solution by P, N, S-Doped plastic wastes activated carbon

Abstract

The persistence of antibiotics in aquatic environments poses a major ecological and public health challenge, particularly due to their role in promoting antimicrobial resistance. This study investigated the synthesis of activated carbon (AC) from polyethylene plastic waste, its modification through heteroatom doping with nitrogen (N), phosphorus (P), and sulfur (S), and its application for the adsorption of ofloxacin (OFL) from aqueous solutions. The prepared adsorbents were characterized and evaluated under varying operational conditions including pH, contact time, initial concentration, and adsorbent dosage. Results showed that adsorption followed the Langmuir isotherm model with strong correlation coefficients (R² = 0.91–0.94), indicating monolayer adsorption. N-doped carbon exhibited the highest adsorption capacity (qmax = 1.45 mg/g), while S-doped carbon demonstrated the strongest binding affinity (KL = 571.28 L/mg). Kinetic analysis revealed that the pseudo-second-order model best described the adsorption process, suggesting chemisorption as the dominant mechanism. The adsorption was pH-dependent, with optimal performance near neutral to slightly basic conditions (pH 8). Overall, the study demonstrates that plastic waste-derived activated carbon offers a sustainable and effective material for antibiotic removal from contaminated water.