Preparation Of Semiconductor@hydrotalcite Composite Material And Its Photocatalytic Performance

With the development of industry and textile industry,a large number of industrial wastewater and printing and dyeing wastewater have been discharged into rivers,causing damage to the ecological environment and seriously threatening human health.Therefore,biodegradation,physical adsorption,chemical precipitation and photocatalytic degradation are used to degrade these organic pollutants.Among them,the photocatalytic degradation method is widely used because of its environmentally friendlly,high degradation efficiency,and easy operation.Layered Double Hydroxide（LDHs）,also known as layered bimetallic hydroxides,are anionic materials with a layered structure,which have the characteristics of memory effect and interlayer ion exchange,and therefore have great potential in the field of wastewater treatment.Both Bi₂WO₆ and WS₂ are n-type semiconductors,which have the advantages of good stability and non-toxicity,and are often used as photocatalysts.In this paper,MgAl-LDH and Bi₂WO₆ powders were prepared by hydrothermal method,and Bi₂WO₆ and WS₂ nanoparticles were loaded in the interlayer of MgAl-LDH as precursor.XRD,FE-SEM,TEM,FT-IR and XPS were characterized the structure,morphology and element composition of the material.The photocatalytic effect,catalytic mechanism and regeneration performance of the product on methyl orange（MO）dye were studied.The results are as follows:（1）The pure phase MgAl-LDH and Bi₂WO₆ are prepared by hydrothermal method.The results show that the MgAl-LDH prepared by hydrothermal method has high purity and good dispersibility.The pH value of the solution has a great influence on the morphology of Bi₂WO₆.The morphology is a flower-like structure under acidic conditions,and heterophase Bi₂O₃ with fine granular structure is formed under alkaline conditions.Under the condition of MO initial solution(300 mg L^-1),pure MgAl-LDH only performs adsorption reaction instead of photocatalysis.（2）The Bi₂WO₆ intercalated MgAl-LDH composite material（Bi₂WO₆/MgAl-LDH）was prepared by a two-step hydrothermal method,and the catalytic properties and mechanism of the product on MO were studied.The results showed that the Bi₂WO₆ nanoparticles were synthesized between the Mg Al-LDH layers,which enlarged the（003）interplanar spacing of MgAl-LDH.Under simulated visible light irradiation,the degradation rate of 300 mg L^-1 MO solution can reach 65%within 120minutes,which is higher than the degradation rate of pure phase Bi₂WO₆（～35%）.Combined with structural characterization and photocatalytic performance analysis,it is shown that after Bi₂WO₆ grows between MgAl-LDH layers,it accelerates the separation of photo-electron-hole pairs,thereby enhancing the photocatalytic activity.At the same time,the product catalysis process conforms to the quasi-first order kinetic equation of the photocatalytic reaction,and the cycle performance is good.（3）Two-step hydrothermal method was used to synthesize WS₂ intercalated MgAl-LDH composite material（WS₂/MgAl-LDH）.The results show that the growth of WS₂ between layers improves the separation efficiency of the photogenerated-electron hole pairs,thereby enhancing the photocatalytic performance of the composite material WS₂/MgAl-LDH.Under simulated visible light irradiation,the degradation rate of 150 mg L^-1 MO solution can reach 90%in 75 min,higher than pure phase WS₂（～70%）.The product catalysis process conforms to the quasi-first order kinetic equation of the photocatalytic reaction,and the cycle performance is good.