Mineral-Mediated Au-TiO₂/g-C₃N₄ Photocatalysts for Enhanced Naphthalene Photodegradation

Naphthalene, as a representative polycyclic aromatic hydrocarbon (PAH), is persistent, bioaccumulative, and toxic, posing a long-term threat to aquatic environments. To address this issue, a mineral-mediated Au-TiO₂/g-C₃N₄ composite photocatalyst with coupled adsorption and photocatalytic functions was constructed through photodeposition, co-pyrolysis, and subsequent in situ mineral loading/calcination. Characterization analyses demonstrated that 1.0 wt% Au provided the most effective electronic modulation, giving an apparent rate constant of 0.174 min^-1 for naphthalene degradation, which was 3.78 times that of the Au-free counterpart. Among the tested mineral supports, bentonite exhibited the strongest adsorption-enrichment effect, increasing the adsorption efficiency to 47.2% and enabling complete removal and near-complete mineralization of naphthalene within 25 min of irradiation. Radical trapping experiments and ESR spectra identified ·OH, ·O₂^-, and h⁺ as the dominant reactive species. Combined with Gas Chromatography-Mass Spectrometry (GC-MS) and in situ Gas Chromatography (GC) analyses, naphthalene was found to undergo progressive hydroxylation, ring opening, and oxidation before final mineralization. This work provides a feasible strategy for designing mineral-semiconductor composite photocatalysts for efficient PAH removal from water.