Recent environmental assessments have highlighted the urgent need for efficient and sustainable technologies capable of degrading recalcitrant pharmaceutical pollutants in freshwater systems. Among photocatalytic materials, graphitic carbon nitride (g-C₃N₄) has garnered attention due to its visible light activity, chemical stability, and tunable properties. However, its performance is strongly influenced by the precursor material and synergistic modifications. This study explores the efficacy of g-C₃N₄ synthesized from melamine, urea, and thiourea—alongside biochar—as a composite system for the photodegradation of selected persistent pharmaceuticals.
The different sources of g-C₃N₄ were calcined at 550°C for two hours to obtain a slightly yellowish form of g-C₃N₄, which was then tested on methyl orange dye. Among the sources, urea demonstrated the highest degradability at 60.25%, followed by thiourea at 32.05% and melamine at 7.59%. To enhance the degradation efficiency, urea was blended with melamine and subsequently with thiourea, resulting in improved degradation attributed to the presence of urea. Further optimization involved blending g-C₃N₄ from these sources with biochar, enhancing both the adsorption capability and photodegradation activity, with urea maintaining a degradation rate of 59.7%. These preliminary investigations led to testing the urea-derived g-C₃N₄ with biochar on the recalcitrant pharmaceuticals, yielding degradation efficiencies of 92.59%, 84.44%, 68.11%, and 61.11% for tetracycline, cefixime, ciprofloxacin, and carbamazepine, respectively. These results indicate that the strategic enhancement of g-C₃N₄ with biochar offers promising potential for advanced water treatment applications targeting pharmaceutical contaminants.