Synthesis Of Bismuth Phosphate Modified Composite And Photocatalytic Degradation Of Dye

As an excellent wide band-gap photocatalyst,BiPO₄ has the advantages of strong mineralization ability,stable chemical property and non-toxic character.But it also suffers the disadvantages of large crystal size,narrow optical response and insufficient photocatalytic efficiency.In order to improve the photocatalytic activity of BiPO₄,we chose the modification method of ion doping and prepared Ni-doped BiPO₄ with high photocatalytic performance by adjusting parameters of hydrothermal synthesis.The hydrothermal process of BiPO₄ and the mechanism of enhanced photocatalytic activity were revealed,which may provide experimental basis and good ideas for producing high-efficiency photocatalysts.In this paper,firstly,Ni-doped BiPO₄ was synthesized by hydrothermal method.It was found that the length diameter ratio of Ni-BiPO₄ nanorods increased and the morphology was more uniform.Ni²⁺existed as nickel oxide and formed NiO/BiPO₄heterojunction structure.Part of Ni²⁺may be doped into the lattice of BiPO₄.In addition,BiPO₄ transformed from hexagonal phase to monoclinic phase in hydrothermal process,which may be promoted by the presence of Ni²⁺.Ni-BiPO₄ with hydrothermal time of12 hours and nickel amount of 1%exhibited the highest photocatalytic activity which can completely degrade the methylene blue solution with concentration of 5 ppm in 10minutes.The apparent rate constant k of Ni-BiPO₄(k=0.46 min^-1)is nearly 7 times that of pure BiPO₄(k=0.07 min^-1).For rhodamine B solution with a concentration of50ppm,Ni-BiPO₄ showed the highest catalytic activity,and could basically degrade rhodamine B in about 60 minutes.In addition,the intrinsic reasons for the improvement of catalyst performance were further explored through various characterization methods,such as carrier separation,light absorption capacity,pollutant binding capacity,etc.It was found that the photoluminescence intensity of Ni-BiPO₄ decreased significantly,indicating that the recombination of photogenerated electrons and holes decreased significantly.Besides,the specific surface area of Ni-BiPO₄ increased remarkably.Therefore,the improvement of the catalytic performance of Ni-BiPO₄ could be attributed to the synergistic effect of morphology control by Ni²⁺and the NiO/BiPO₄ heterojunction structure.At last,the composite effect of carbon nanotubes and agarose with BiPO₄ was studied respectively.The removal efficiency of BiPO₄-agarose composite photocatalyst is not ideal,while BiPO₄-carbon nanotube composite photocatalyst showed a synergistic effect of adsorption before degradation in the removal of methylene blue,and its photocatalytic degradation efficiency is higher than that of ordinary bismuth phosphate.However,there is a certain performance loss in the circulation process of the catalyst and the preparation of composite materials needs further study.