Enhanced removal of tetracycline from water using MgO-modified g-C3N4 composite: Synthesis optimization and mechanism investigation

Abstract

Tetracycline(TC) is a typical pharmaceutical and personal care product (PPCP) that harms ecological health due to its impact on human allergic reactions, bacterial resistance, and environmental microbiota. Thus, developing environmentally friendly, efficient, and suitable methods to eliminate TC and inactivate bacteria in aquatic environments is becoming essential. A facile hydrothermal approach was developed to synthesize MgO-modified g-C₃N₄ composites for efficient TC removal from water. The as-prepared composites were thoroughly characterized by BET, SEM, XRD, and XPS analyses, confirming the successful incorporation of MgO into the g-C₃N₄ framework. Under optimal conditions (1:1 MgO/g-C₃N₄ ratio, 150 °C synthesis temperature), the composite achieved 84.89 % TC removal within 90 min under visible light, substantially outperforming pristine materials (MgO, g-C₃N₄). The composite maintained removal efficiency above 70 % after six successive cycles, demonstrating excellent stability. Mechanistic investigations identified O₂•⁻ as the dominant reactive species, with h⁺ playing a secondary role. Analysis of atomic Fukui indices revealed preferential radical attack at C₇, O₂₀, and N₂₄ sites, leading to TC degradation through hydroxylation and cyclization pathways. The composite showed promising performance in actual river water treatment, suggesting potential for practical applications. This work provides insights for developing efficient photocatalytic materials for pharmaceutical pollutant removal from water.