Controllable Preparation Of Bi₂O₃ And Bi₂SiO₅-Bi₂O₃ Loaded Sepiolite Photocatalysts And Its Photocatalytic Property

The environmental problems caused by the rapid development of social economic and the continuously progress of the industry have been increasingly serious,from which the water pollution had more attention.Traditional wastewater treatment methods such as coagulant sedimentation,adsorption,and membrane separation were non-destructive method,thus the contaminant had no complete decompose.Biological method was a destructive way to decompose the wastewater,but for which the content of the toxic substances in wastewater was much higher than the standards of wastewater discharge for its low cleanliness ability.Photocatalysis technology was an advanced oxidation technology,the photocatalyst produced the electron(e-)-hole(h+)pairs,superoxide radicals(·O2-)and hydroxyl radicals(·OH)under light irradiation,by which the hard-degraded organic pollutants(such as dyeing wastewater)was decomposed to became some innocuous substances such as CO2 and H2O after a series of oxidation-reduction reactions.Bi2O3 as a new type of semiconductor photocatalyst had widely attention for its excellent optical absorption ability,but the pure Bi2O3 powder particles was easily aggregation thus limited which photocatalytic properties.Sepiolite was an natural magnesium hydrosilicate clay mineral with fibrous structures,which had large specific surface area and high absorption ability,loaded Bi2O3 on sepiolite can easily overcame the problem.By controlling the reaction conditions in this process,the sepiolite was not only as a supporter,but also a provider of silicon reacting with Bi(NO3)3·5H2O to formation of Bi2SiO5.The synthesis of Bi2SiO5-Bi2O3 loaded sepiolite solved the problem of the pure Bi2O3 was easily aggregation,furthermore,the formation of Bi2SiO5-Bi2O3 heterojunction makes its photocatalytic activity had further improve.In this paper,the selective preparation of the Bi2O3 and Bi2SiO5-Bi2O3 loaded sepiolite was achieved by controlling the reaction conditions for chemical precipitation method.Using X-ray diffraction(XRD),scanning electron microscope(SEM)and UV-vis diffuse reflectance spectra(UV-vis DRS)to characterized the prepared catalyst.The malachite green(MG)was utilized as the model pollutant to evaluate the photodegradation peroperties under visible light(?>400nm)irradiation.The main conclusions of this study are as follows:1.A series of Bi2O3 and Bi2SiO5-Bi2O3 loaded sepiolite was selective synthesized by adjusting the concentration of Bi(NO3)3·5H2O and NaOH,reaction temperature,reaction time and calcination temperature.The XRD characterization results shows that only in the concentration of Bi(NO3)3·5H2O was 0.02mol/L and NaOH was 0.5-1mol/L,reaction temperature was 25?75 ?,after reaction with 2 hours and calcination at 400 ? for 2 hours,the Bi2SiO5-Bi2O3 loaded sepiolite photocatalyst can be successfully synthesized.According to the photodegradation experiment,the Bi2SiO5-Bi2O3 loaded sepiolite photocatalyst performed higher photocatalytic activity than the photocatalyst of Bi2O3 loaded sepiolite at every experiments.2.The scavenger experiments performed that addition of benzoquinone(BQ)leading the photocatalytic activity of Bi2SiO5-Bi2O3 loaded sepiolite photocatalyst had obviously decrease,the next was isopropanol(IPA).The photocatalytic activity had no obvious variation when addition ammonium oxalate(AO)into the degradation system.It illustrated that the mainly active species was O2-,the next was ·OH,h+ had little influence on photodegradation activity of Bi2SiO5-Bi2O3 loaded sepiolite photocatalyst.3.By controlling the reaction conditions at photodegradation process,the utilized dosage of photocatalyst and the initial pH value of the MG solution were investigated to illustrate which influence on photodegradation property of the Bi2SiO5-Bi2O3 loaded sepiolite photocatalyst.The results of photocatalytic experiment shows that the Bi2SiO5-Bi2O3 loaded sepiolite photocatalyst performed optimal photocatalytic activity when utilized dosage of photocatalyst was 0.05g and the initial pH value of the MG solution was about 4.