Precursor-Directed Synthesis of Graphitic Carbon Nitride–Biochar Composites for Improved Photodegradation of Recalcitrant Pharmaceuticals

Abstract

This study investigates how graphitic carbon nitride (g-C3N4), derived from melamine, urea, and thiourea, degrades recalcitrant pharmaceuticals. Among the materials used, g-C3N4 derived from urea showed the highest degradation of methyl orange (60.25%). When calcined with biochar derived from onion flower seed-cover biomass via pyrolysis and further activated with potassium hydroxide (KOH), it showed better adsorption and photodegradation results of 92.59%, 84.44%, 68.11%, and 61.11% for tetracycline, cefixime, ciprofloxacin, and carbamazepine, respectively. These results emphasize the potential of biochar-g-C3N4 composites as sustainable photocatalysts for water treatment focused on removing recalcitrant pharmaceutical contaminants.