Study On The Degradation Of Congo Red By TiO₂/montmorillonite Composites Regulated By Bismut

In this paper,sodium montmorillonite was used as the matrix material,tetrabutyl titanate was used as the titanium source,and Bi（NO₃）·5H₂O was used as the bismuth source.TiO₂photodegradation materials and BiOCl/TiO₂/montmorillonite composites was prepared by sol-gel method,and were used for photocatalytic degradation of Congo red dye wastewater.The photocatalytic degradation performance and mechanism of composite materials were explored by X-ray diffraction,TG-DSC,scanning electron microscopy,transmission electron microscopy,X-ray fluorescence spectroscopy,X-ray photoelectron spectroscopy,specific surface area analyzer,UV-Vis diffuse reflectance spectroscopy,transient photocurrent,and electrochemical impedance spectroscopy,etc.The main research results were as follows:The crystallization temperature of TiO₂photodegradable materials ranged from220℃to 450℃.At 500℃,the crystal size of TiO₂particles was about 18.09 nm.When the temperature increased from 600℃to 800℃,the crystal form of TiO₂changed from anatase to rutile,and the particle agglomeration became more serious.The results of UV-Vis diffuse reflection indicated that the band gaps of anatase was3.24 e V,and rutile was 2.96 e V.TiO₂material had the best photocatalytic activity when ethanol addition was 10 m L,glacial acetic acid addition was 5 m L,calcination temperature was 500°C,and calcination time was 1.5 h.After 180 min of illumination,the degradation rate of Congo red reached 77.06%.BiOCl/TiO₂/montmorillonite composites were composed of TiO₂particles,BiOCl nanosheets and montmorillonite flakes.TiO₂particles were attached to BiOCl nanosheets in the form of anatase.Both addition of montmorillonite and BiOCl inhibit the growth of TiO₂crystals.The specific surface area of BiOCl/TiO₂/montmorillonite composites was 109.02 m²/g.Ti,Bi and Cl elements in the composite material existed in the form of+4,+3 and-1 valence states.The formation of heterojunction between BiOCl/TiO₂reduces the band gap to 2.61 e V.Composite had higher separation efficiency of photogenerated electron-hole pairs.The BiOCl/TiO₂/montmorillonite composite had the highest photocatalytic activity when the p H of the sol was 4,the mass concentration of the montmorillonite suspension was 1%,the calcination temperature was 600℃,the calcination time was 2 h,and the Bi/Ti molar ratio was20%.After 30 min of dark adsorption and 120 min of light,the degradation rates of20 mg/L Congo red solutions reached 98.64%.The photocatalytic process conformed to the Langmuir-Hinshlwood first-order kinetic equation.Repeated experiments showed that BiOCl/TiO₂/montmorillonite composites had good stability.Radical masking experiments showed that hydroxyl radicals and superoxide radicals were the main active substances in the degradation of Congo red by the composites.