Synthesis And Properties Of Novel Photocatalyst SnC₂O₄ And Its Composite

Photocatalytic oxidation is a new advanced water treatment technology with the characteristics of simple equipment,mild operating conditions,strong oxidizing ability,strong bactericidal effect and no secondary pollution,which shows a good application prospect in water treatment.The core of photocatalytic oxidation is semiconductor photocatalyst.In recent years,the synthesis of new photocatalyst with different composition,structure and morphology,to expand its spectral response range and improve its photocatalytic activity has become one of the hot spots in the field of photocatalysis research.In this paper,the irregular block-like SnC₂O₄,rod-like SnC₂O₄ and Fe₃O₄/SnC₂O₄ novel photocatalysts were synthesized by simple precipitation method and solvothermal method.The samples were analyzed and characterized by X-ray powder diffraction,scanning electron microscopy,UV-Vis spectrophotometer and fluorescence spectrophotometer.The effects of different precipitant,reaction temperature and time on the phase structure,morphology,optical absorption properties and photocatalytic properties were investigated.Moreover,the mechanism of photocatalytic degradation reaction were discussed.The main research contents and results are as follows:?1?The novel photocatalysts SnC₂O₄ powders were synthesized by direct precipitation method using H₂C₂O₄·H₂O,Na₂C₂O₄ or?NH₄?₂C₂O₄·H₂O as precipitant,respectively.According to the analysis results,the samples prepared by different precipitants are all monoclinic scheelite-type SnC₂O₄?C2/C?15??,and the cell parameters are a=1.0371 nm,b=0.5503 nm,and c=0.8783 nm.The average band gap of the samples synthesized using H₂C₂O₄·H₂O,Na₂C₂O₄ or?NH₄?₂C₂O₄·H₂O as precipitant is 3.34 eV?3.27 eV and 3.44 eV,respectively.The photocatalytic performance of the samples was investigated by degradation of 40 mg/L methyl orange.The samples prepared using Na₂C₂O₄ or?NH₄?₂C₂O₄·H₂O as precipitant present excellent photocatalytic performance.Under visible light irradiation for 90min,when the dosage of SnC₂O₄ photocatalyst is 40 mg/50 mL,the degradation rate of Methyl Orange reaches to about 100%.The photocatalytic degradation reaction conforms to the first-order kinetic equation.Furthermore,based on the analysis of IR,PL and XRD,the decolorization of Methyl Orange is due to the photocatalytic degradation by SnC₂O₄.By adding the active species capture agent,it is proved that·O₂^-plays an important role in photocatalytic reaction.Compared with activated carbon,the as-synthesized SnC₂O₄ sample has good recovery performance and stability.?2?The novel rod-like SnC₂O₄ was synthesized by simple solvothermal method.The effect of different heating temperature and time on the phase structure,crystalline degree,morphology and photocatalytic properties were investigated.Moreover,the photocatalytic reaction conditions were optimized.The results show that the samples prepared under different heating temperatures in range of 100¹40?are all monoclinic SnC₂O₄.The particles are all rod in shape with the diameter of about 1?m.andSnC₂O₄.When the heating temperature is 120?,the as-synthesized sample has the best photocatalytic activity.When the dosage of SnC₂O₄ rods is 40 mg/50 mL,visible light is used as irradiation source and the irradiation time is 80 min,the degradation rate of Methyl Orange solution with concentration of 40 mg/L can reach to 99.1%.In addition,the heating time also has great effects on the crystalline degree and photocatalytic properties of the sample.When the heating time is prolonged from 1 h to 24 h,the crystallinity and photocatalysis activity of the samples are all improved,but the morphology is not changed obviously.Furthermore,the degradation mechanism of the dye was explored by introducing the scavengers of active species.It shows that·O₂^-play a dominant role in the degradation of the dye.?3?Fe₃O₄/SnC₂O₄ visible light photocatalytic material were synthesized by two-step precipitation.The samples were characterized by means of XRD,SEM,EDS,UV-vis and PL techniques.Methyl orange was used as simulated dye wastewater to investigate the photocatalytic activity of Fe₃O₄/SnC₂O₄.The results showed that Fe₃O₄/SnC₂O₄ samples have relatively narrow band gap energy compared with pure SnC₂O₄,and strong absorption of visible light.Among the samples with different content of Fe₃O₄,20%Fe₃O₄/SnC₂O₄ shows excellent photocatalytic performance.When the dosage of 20%Fe₃O₄/SnC₂O₄ is 40 mg/50mL,the degradation rate of 40 mg/L Methyl Orange reach to 97.7%when exposed to visible light for 60 min.The photodegradation reaction follows the first order kinetic equation,and the rate constant is 1.68 times of pure SnC₂O₄.The degradation mechanism of the dye was explored by introducing the scavengers of active species.The results shows·O₂^-play a major role in photocatalytic reaction.Recycling test indicates that as-synthesized Fe₃O₄/SnC₂O₄ was stable in five cycles.