This study investigates the synthesis and optimization of a ZnO/g-C3N4 S-scheme photocatalyst for visible light-driven degradation of paracetamol in wastewater. The researchers fabricated composites with varying percentages of g-C3N4 (3%, 5%, 10%, and 20%) to enhance the photocatalytic activity. The optimized composite, containing 10 wt.% g-C3N4 with ZnO, demonstrated a 95% degradation efficiency of paracetamol within 60 minutes of visible light exposure, a significant improvement over lower wt.% composites and pristine g-C3N4. The enhanced performance is attributed to the narrowing of the band gap to match solar radiation, increased specific surface area, and efficient charge carrier transfer mechanisms through the S-scheme heterojunction. Trapping experiments identified hydroxyl radicals as the primary reactive species responsible for paracetamol degradation. The composite also exhibited excellent photostability and reusability, making it a promising candidate for practical applications in environmental remediation. The study provides a detailed characterization and mechanistic insights into the synthesis and photocatalytic behavior of the ZnO/g-C3N4 composite, highlighting its potential for effective and sustainable removal of pharmaceutical contaminants from aquatic environments.This study investigates the synthesis and optimization of a ZnO/g-C3N4 S-scheme photocatalyst for visible light-driven degradation of paracetamol in wastewater. The researchers fabricated composites with varying percentages of g-C3N4 (3%, 5%, 10%, and 20%) to enhance the photocatalytic activity. The optimized composite, containing 10 wt.% g-C3N4 with ZnO, demonstrated a 95% degradation efficiency of paracetamol within 60 minutes of visible light exposure, a significant improvement over lower wt.% composites and pristine g-C3N4. The enhanced performance is attributed to the narrowing of the band gap to match solar radiation, increased specific surface area, and efficient charge carrier transfer mechanisms through the S-scheme heterojunction. Trapping experiments identified hydroxyl radicals as the primary reactive species responsible for paracetamol degradation. The composite also exhibited excellent photostability and reusability, making it a promising candidate for practical applications in environmental remediation. The study provides a detailed characterization and mechanistic insights into the synthesis and photocatalytic behavior of the ZnO/g-C3N4 composite, highlighting its potential for effective and sustainable removal of pharmaceutical contaminants from aquatic environments.