关键词: 蒙脱石, 富氮氮化碳, 光催化水泥涂层, 混凝土基体, 四环素

Abstract:

Nitrogen-rich carbon nitride（C₃N₅） was loaded on the surface of montmorillonite MK30 to prepare C₃N₅/MK30 photocatalyst in situ.The crystal form，functional groups，elemental composition，spectral response，photoelectron-hole recombination and charge transfer resistance of the photocatalyst were characterized by X-ray diffraction（XRD），fourier transform infrared spectroscopy（FT-IR），X-ray photoelectron spectroscopy（XPS），UV-visible diffuse reflectance spectrometry（UV-vis DRS），photoluminescence spectra（PL） and electrochemical impedance spectroscopy（EIS）.The results showed that the loading of MK30 as a carrier effectively promoted the separation of C₃N₅ photoelectron-holes，and the charge transfer rate was improved.The efficient degradation of tetracycline（TC） solution was achieved under visible light irradiation for 60 min，and the degradation rate reached 97.15%.The recycled C₃N₅/MK30 photocatalyst still showed good activity.The C₃N₅/MK30 photocatalyst was coated on the surface of concrete in the form of cement coating，and the best photocatalytic activity was shown when the mass fraction was 6.5%.The C₃N₅/MK30 photocatalytic coating achieved a maximum degradation rate of 92.96% for 25 mL of TC solution with a mass concentration of 200 mg/L on the surface.The cement coating still showed a high degradation rate of 91.72% after scouring and drying by high-pressure water gun.The loading of C₃N₅/MK30 played a role of crystal nucleus to promote the hydration of cement and the formation of hydration products.The generated large amount of hydration products could effectively fill the pores，making the bonding between the concrete matrix and the cement coating closer.The compressive strength of concrete cured for 7 and 28 d was increased by 20.53% and 9.26%，respectively.

Key words: montmorillonite, nitrogen-rich carbon nitride, photocatalytic cement coating, concrete matrix, tetracycline