Research subject: In this study, a heterojunction nanostructure composed of graphitic carbon nitride (g-C₃N₄) and copper oxide (CuO) was synthesized and investigated to evaluate its photocatalytic efficiency in degrading organic dyes (such as Rhodamine B) and potassium amyl xanthate (PAX) under visible light irradiation. The main objective was to enhance photocatalytic performance by combining these two semiconductors and studying various parameters, including calcination temperature.
Research approach: To synthesize the g-C₃N₄/CuO heterojunction nanostructure, the calcination method was employed. In this process, g-C₃N₄ was synthesized through the polymerization of urea at 550  °C. For fabricating the heterojunction nanocomposite, different amounts of CuO nanoparticles were mixed with urea and calcined at various temperatures for 4 hours in a furnace.
XRD analysis was used to identify the crystalline phases, UV-vis spectroscopy was performed to measure optical transmittance, and FE-SEM was applied to examine the surface morphology. The electron–hole recombination rate was studied using photoluminescence (PL) spectroscopy. Finally, the photocatalytic activity of the composites was evaluated by the degradation of Rhodamine B and  potassium amyl xanthate under visible light irradiation, and scavenger tests were conducted to identify the active species involved in the degradation process.
Main results: XRD analysis confirmed the successful formation of the g-C₃N₄/CuO heterojunction. UV-vis spectra showed that incorporating CuO into g-C₃N₄ decreased visible light transmittance compared to pure g-C₃N₄. FE-SEM images revealed morphological changes and a reduction in the thickness of g-C₃N₄ layers as a result of heterojunction formation, contributing to improved  photogenerated charge transfer. The g C₃N₄/CuO composite degraded 88% of potassium amyl xanthate within 180 minutes and 96% of Rhodamine B within 80 minutes, whereas pure g C₃N₄ achieved only 68% degradation of potassium amyl xanthate and 90% of Rhodamine B. Scavenger test results indicated that superoxide radicals (·O₂⁻) were the main active species in the photocatalytic degradation process. These findings demonstrate the enhanced performance of the g-C₃N₄/CuO nanocomposite in light absorption, charge separation, and efficient pollutant degradation, suggesting its potential as an effective photocatalyst for industrial wastewater treatment.