Facile synthesis hierarchical porous structure anatase–rutile TiO2/g-C3N4 composite for efficient photodegradation tetracycline hydrochloride

Highlights: • The (A-R)TiO₂/g-C₃N₄ composite with hierarchical porous structure was synthesized. • The relative content of anatase and rutile of TiO₂ in composite could be regulated. • The (A-R)TiO₂/g-C₃N₄ exhibited favorable visible-light photocatalytic property. The anatase–rutile TiO₂/g-C₃N₄ (denoted as ARC) photocatalyst with hierarchical porous structure is synthesized via an impregnation-calcination method utilizing TiCl₄ and melamine as precursor. The content of g-C₃N₄, and the relative content of the anatase and rutile in ARC can be regulated via controlling the dosage of melamine. Furthermore, the highly acidic environment producing by hydrochloric acid which is generated via hydrolysis reaction of TiCl₄ has significantly impact for forming the hierarchical porous structure of ARC. Comparing with g-C₃N₄, the specific surface area of ARC-5 (61.2 m²·g⁻¹) is 7.2 times than that of g-C₃N₄. Among all the resultant composites, the ARC-5 exhibits the highest visible-light photocatalytic property for degrading tetracycline hydrochloride (TC-HCl, 10 mg·L^-1). The degradation rate of TC-HCl is 92% in 60 min with ARC-5 as photocatalyst, and the kinetic constant (k) of ARC-5 is 4.4 times than that of g-C₃N₄. The favorable catalytic property of ARC-5 should be attributed to the close-knit interface contact and high surface area, which could broaden the spectra absorption range, facilitate the carriers separation, provide more active sites and enhance the transfer rate of reactant and product. Moreover, radical trapping experiments shows that h⁺ and • O₂^– have vital function for degrading TC-HCl.