Acetaminophen and Tetracycline Removal Using <i>Prosopis juliflora</i> -Derived ZnO-Modified Biochar: Evaluation in Batch and Continuous Systems

The discharge of pharmaceutical active compounds (PhACs) into aquatic environments has become a growing concern due to their adverse effects on both aquatic organisms and human health. Simultaneously, the global spread of invasive weeds disrupts ecosystems, leading to significant environmental and economic consequences. This study investigates competitive adsorption of acetaminophen (ACT) and tetracycline (TET) using green-synthesized ZnO-biochar derived from Prosopis juliflora (ZPJC). ZPJC was characterized using SEM, EDX, FTIR, XRD, TGA, and pHpzc analyses and applied in both batch and column experiments for monocomponent (ACT/TET) and multicomponent (ACT+TET) systems. Batch experiments examined the impact of operational parameters such as initial PhAC concentration (0.1–10 mg/L), contact time (1–180 min), pH (3–11), and ZPJC dose (0.25–4 g/L). Column experiments explored the variations in bed depth (3–9 cm), flow rate (0.5–2 L/h), and influent concentration (1–5 mg/L). Optimal conditions (60 min, 6.5 pH, and 3 g/L ZPJC dose) resulted in a maximum adsorption capacity of 5.27 mg/g for TET and 9.26 mg/g for ACT in the batch system, following pseudo-second-order and Langmuir models, suggesting chemisorption dominance. For column systems, the Thomas and Yoon–Nelson models better represented experimental data. Adsorption efficiency improved with increasing bed depth and flow rate, while it declined with higher PhAC concentration. In multicomponent batch systems, TET exhibited antagonistic effects due to site competition and steric effects, whereas ACT demonstrated slight synergism. However, in column systems, both ACT and TET displayed antagonistic interactions. Scale-up design of the column elucidates that ZPJC can be adopted as a sustainable solution for the removal of PhACs while addressing invasive weed proliferation.