Pharmaceutical pollution, especially antibiotics, poses a significant environmental challenge due to their high chemical and biological stability, which hinders their removal by conventional water treatment methods. Ciprofloxacin, a commonly used antibiotic, is frequently detected in aquatic environments and is resistant to conventional degradation. In this study, graphitic carbon nitride (g-C3N4) nanomaterials were synthesized via thermal polymerization under a nitrogen atmosphere at three different gas flow rates of 10, 40, and 80 mL/min (denoted as G-10, G-40, and G-80, respectively). The synthesized samples were characterized using XRD, FTIR, BET, PL, and FE-SEM, confirming the formation of a crystalline structure with favorable porosity and optical properties. BET analysis revealed that G-10 exhibited the highest specific surface area (46.6 m²/g), which resulted in enhanced light absorption and superior photocatalytic activity. Photocatalytic degradation experiments of ciprofloxacin (initial concentration of 10 mg/L) under visible LED light at pH 5 and catalyst dosage of 1 g/L demonstrated that G-10 achieved a removal efficiency of 96.4% within 90 minutes, whereas G-40 and G-80 showed lower efficiencies due to reduced surface area. Kinetic analysis indicated that the degradation followed a pseudo-second-order model. Reusability tests confirmed that the catalyst maintained high performance after several successive cycles. These results indicate that g-C3N4 synthesized under a nitrogen flow of 10 mL/min offers high efficiency and stability as a visible-light photocatalyst for the removal of pharmaceutical contaminants from aqueous systems.