Eu-Doped Zeolitic Imidazolate Framework-8 Modified Mixed-Crystal TiO2 for Efficient Removal of Basic Fuchsin from Effluent

Zeolitic imidazolate framework-8 (ZIF-8) was doped with a rare-earth metal, Eu, using a solvent synthesis method evenly on the surface of a mixed-crystal TiO2(Mc-TiO2) structure in order to produce a core–shell structure composite ZIF-8(Eu)@Mc-TiO2 adsorption photocatalyst with good adsorption and photocatalytic properties. The characterisation of ZIF-8(Eu)@Mc-TiO2 was performed via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller analysis (BET) and ultraviolet–visible light differential reflectance spectroscopy (UV-DRs). The results indicated that Eu-doped ZIF-8 was formed evenly on the Mc-TiO2 surface, a core–shell structure formed and the light-response range was enhanced greatly. The ZIF-8(Eu)@Mc-TiO2 for basic fuchsin was investigated to validate its photocatalytic performance. The effect of the Eu doping amount, basic fuchsin concentration and photocatalyst dosage on the photocatalytic efficiency were investigated. The results revealed that, when 5%-Eu-doped ZIF-8(Eu)@Mc-TiO2 (20 mg) was combined with 30 mg/L basic fuchsin (100 mL) under UV irradiation for 1 h, the photocatalytic efficiency could reach 99%. Further, it exhibited a good recycling performance. Thus, it shows certain advantages in its degradation rate and repeatability compared with previously reported materials. All of these factors suggested that, in an aqueous medium, ZIF-8(Eu)@Mc-TiO2 is an eco-friendly, sustainable and efficient material for the photocatalytic degradation of basic fuchsin.