The Research Of The Preparation Of Phosphate Photocatalysts And Their Photocatalytic Property

Phosphate compounds are common inorganic materials with rich P-O coordination polyhedron and open-framework structure. They show diversity and unique in structure performance, with excellent catalysis, ion exchange and adsorption. They possess great research potentiality, but few of them were researched in the field of photocatalysis. In this paper, we explored the photocatalytic activity of zirconium phosphate and bismuth phosphate, and optimized the preparation conditions, meanwhile, we also do some work about modification to improve their photocatalytic activity. The main research contents are as follows:(1) Using zirconium oxychloride and concentrated phosphoric acid as raw materials, Zr3(PO4)4 photocatalyst was synthesized by hydrothermal method, and the synthesis conditions were optimized. The research found that the greatest effect of synthesis conditions was the concentration of phosphoric acid in hydrothermal system. Controlling the concentration of phosphoric acid at 4 mol/L, after the hydrothermal reaction at 180 ℃ for 6 h,Zr3(PO4)4 nanoparticles was synthesized with good photocatalytic oxidation performance. The degradation rate of reactive brilliant blue(30 mg/L) was up to 57.37% under UV irradiation, and the photocatalytic activity of Zr3(PO4)4 was higher than P25(55.23%) in the same condition.(2) Using bismuth nitrate as bismuth source, phosphate ions from sodium dihydrogen phosphate, BiPO4 photocatalyst was synthesized by hydrothermal method. To study the relations between synthesis conditions and the photocatalytic activity, we changed the preparation conditions(hydrothermal time, hydrothermal temperature and pH) and the phase and morphology of BiPO4 photocatalysts were characterized by means of characterization, like XRD, SEM, etc. The hydrothermal conditions have great effects on the crystal structure of BiPO4. Without hydrothermal crystallization, hexagon BiPO4(acicular) is parpered, and it would be monoclinic BiPO4(granular and rod) after hydrothermal crystallization, meanwhile, the photocatalytic activity changed greatly. The synthesis conditions of best photocatalytic activity were 6 h(hydrothermal time), 160 ℃(hydrothermal emperature), 2.1(pH) and water(the solvent), solvent and pH are the main influencing factors.(3) AgBr layer deposited on the surface of BiPO4 via precipitation process, the Ag/AgBr/BiPO4 composite photocatalyst were prepared after putting mixture under the light. The structure and property of as-synthesized samples were characterized by XRD, TEM, XPS, PL and photocurrent. The study found that BiPO4 appearance had not changed after loading Ag/AgBr, but there are some small particles on the surface. The small particles were proved to be Ag/Ag Br particles through the characterizeation. With the increasing of loading amount, the response to visible light increased, while the loading amount was 7%, photocatalyst owned the highest catalytic activity in visible light,and the degradation rate was up to 88.7%.