Controllable Synthesis Of High-activity Nano-Bi₂O₃ And Its Photocatalytic Properties

Nano-Bi₂O₃ is a novel inorganic functional semiconductor material with the excellent properties and especially exhibits the potential application in the field of photodegradation for wastewater.As a result,the synthesis method and how to improve the photodegradation ability of Bi₂O₃ continue to be the focus of much attention.In this thesis,nano-Bi₂O₃ was prepared using Bi?NO₃?₃·5H₂O and?NH₄?₂CO₃ as raw materials by parallel flow precipitation process.The optimum synthesis process of nano-Bi₂O₃ was determined and the Ni-doped Bi₂O₃ nanomaterial was further modified.The prepared Bi₂O₃ photocatalytic materials were characterized by XRD,BET,SEM,TG-DTA and TEM.The photocatalytic performance of prepared nano-Bi₂O₃ towards the decolorization of acid red 26?AR 26?and malachite green?MG?which used as model pollutants was studied.The research contents and results include the following aspects:The effects of the concentration of raw materials,reaction temperature,reaction pH and calcination temperature on the performance of synthesized nano-Bi₂O₃ were researched and optimal experimental conditions were summarized.When the concentration of Bi?NO₃?₃ and?NH₄?₂CO₃ was 0.75 mol/L and 2.00 mol/L respectively,precipitated at 40? and pH 7.5,then calcined at 400? for 1.5 h,the flake nano-Bi₂O₃ was formed with the crystal size of 28 nm and surface area of 48.16 m²/g.The effects of different environmental factors on the photocatalytic activity of nano-Bi₂O₃ were investigated using AR 26 and MG as model pollutants.When initial pH of AR 26 and MG was 6 and 8 respectively,concentration of two model pollutants was 10 mg/L and dosage of nano-Bi₂O₃ was 0.6 g/L,the photodegradation efficiency of AR 26 and MG reached to 60.2% and 81.3% respectively,under irradiation of a 30 W ultraviolet lamp with distance of 15 cm for 50 min.The degradation rate of AR 26 and MG decreased to 56.2% and 77.7% respectively?less than 5%? with nano-Bi₂O₃ photocatalyst after 5 times usage.The nano-Bi₂O₃ prepared by parallel flow precipitation process had a good prospect for industrial application.The effects of Ni-doping on crystal structure,micro-morphology and photodegradation ability of Bi₂O₃ prepared using parallel flow precipitation process were studied.Ni-doping can effectively inhibit the growth process of Bi₂O₃ microcrystal and increase its specific surface area.Ni-doping did not change the intrinsic crystal structure of?-Bi₂O₃ when its doping amount was less than 5%.The self-assembled spherical Bi₂O₃ microcrystal was obtained while the Ni-doping amount was 3%.When initial pH of AR 26 and MG was 6 and8 respectively,concentration of two model pollutants was 10 mg/L and dosage of photocatalyst Ni/Bi₂O₃ was 0.3 g/L,the photodegradation efficiency of AR 26 and MG reached up to 90.3%and 100%respectively,under irradiation of a 30 W ultraviolet lamp with distance of 15 cm for 50 min.The photocatalytic activity of Bi₂O₃ was significantly improved due to Ni-doping effectively suppressed recombination of photoexcitation e^-/h⁺ pairs.