Efficient synergistic catalytic degradation of Naphthalene in water by g-C3N4/ZnO heterojunction immobilized lipase

The efficient removal of Naphthalene (Nap), a persistent organic pollutant known for its severe endocrine-disrupting and carcinogenic properties, is vital for environmental protection. This study introduces a straightforward approach for addressing persistent organic pollutants in water through the strategic construction of a photo-enzyme coupled catalytic system (PECS). In this study, we fabricated a photocatalyst/enzyme heterojunction by immobilizing lipase (LPZYM) on a composite material of graphitic carbon nitride and zinc oxide (g-C₃N₄/ZnO, ZCN), which served as the photocatalytic substrate for the degradation of Nap. The resulting ZCN/LPZYM heterojunction demonstrated outstanding degradation efficacy and cyclic stability in the aqueous removal of Nap, achieving a degradation rate of 97.36 % under visible light irradiation within 150 min. This performance significantly surpasses that of g-C₃N₄ (64.16 %), ZnO (79.31 %), and ZCN alone (87.22 %). The superior degradation capabilities of ZCN/LPZYM can be primarily attributed to the synergistic catalytic effects of the enzyme, coupled with enhanced visible light absorption and carrier separation efficiency. Mechanistic investigations revealed that superoxide anion radicals (·O₂^–), hydroxyl radicals (·OH), and singlet oxygen (¹O₂) play critical roles in the Nap degradation process, with the order of effectiveness being ·O₂^–> ·OH > ¹O₂.