Adsorptive Removal of Emerging Pharmaceutical Contaminants from Hospital Wastewater Using Modified Biochar in Ogun State, South West Nigeria

Pharmaceutical contaminants including antibiotics, analgesics, and hormones are increasingly detected in hospital wastewater discharged into Nigerian water bodies, where they exert sub-lethal effects on aquatic ecosystems and contribute to the proliferation of antimicrobial resistance genes. This study investigates the adsorptive removal of selected emerging pharmaceutical contaminants, specifically ciprofloxacin, ibuprofen, and estradiol, from hospital wastewater using alkali-modified rice husk biochar prepared by slow pyrolysis followed by potassium hydroxide activation. Hospital wastewater samples are collected from two tertiary hospitals in Ogun State, South West Nigeria. Biochar is characterised by Brunauer-Emmett-Teller surface area analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, and proximate analysis. Batch adsorption experiments investigate the effect of pH, contact time, initial pharmaceutical concentration, biochar dosage, and temperature on removal efficiency. Equilibrium data are modelled using Langmuir, Freundlich, and Temkin isotherms, while kinetics are described using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. Thermodynamic parameters confirm the endothermic or exothermic nature of each pharmaceutical's adsorption. Column breakthrough experiments are conducted to simulate fixed-bed treatment conditions applicable to a small hospital wastewater polishing unit. Regeneration and reuse of spent biochar are evaluated over five cycles. Findings provide evidence for the practical application of low-cost modified biochar as a tertiary polishing technology for pharmaceutical-contaminated hospital wastewater in Nigeria. Keywords: pharmaceutical contaminants, biochar, adsorption, hospital wastewater, emerging pollutants