Preparation And Modification Of Nanometer Red Phosphorus And Its Application In Photocatalytic Reduction Of Cr(?)

As we all know,hexavalent chromium Cr?VI?is carcinogenic and teratogenic.It is difficult to degrade in the environment.As one of the heavy metal pollutant,it has always been a research emphasis in the environmental protection industry to adopt effective measures to deal with hexavalent chromium pollution.Compared with traditional treatment measures,photocatalytic technology is more economical and does not produce secondary pollution,with great application advantages.Red phosphorus,as one of the natural semiconductor,does not contain metal elements,has a wide visible light absorption range?bandwidth is about 1.8 eV?,and many advantages,such aslow cost,stable chemical properties,non-toxicity,etc.It has great potential in in study of heterogeneous photocatalysis on semiconductors and its applications.However,the original commercial red phosphorus particle size is at the micron level with the low photocatalytic due to high carrier recombination and activity specific surface area.Herein,this paper used hydrothermal treatment and ultrasonic treatment to modify the commercial red phosphorus and applied it to the photoreduction research of Cr?VI?,compared the photocatalytic activity of the nano red phosphorus and the commercial red phosphorus obtained after treatment,and further improves the photocatalytic activity of the nano red phosphorus by modifying the nano red phosphorus.Finally,the mechanism of the activity of catalytic materials was studied through material characterization.The main contents are as follows:1.Using commercial red phosphorus as the raw material,hydrothermal treatment for 12 hours and ultrasonic treatment for 2 hours,red phosphorus photocatalytic material with particle size below 10 nm was obtained.X-ray diffraction,scanning and transmission electron microscopy,solid ultraviolet absorption,photoelectron spectroscopy and other characterization were used to analyze the phase,surface chemical composition,morphology and structure and optical properties of nano-red phosphorus.The photocatalytic reduction activity of Cr?VI?by commercial red phosphorus and nano-red phosphorus is compared.The experimental results show that under the condition of pH=2,40 mL of 20 mg/L Cr?VI?aqueous solution can be completely converted after adding 2 mg of nano-red phosphorus and irradiating with visible light for 36 min.The experimental results show that the decrease of particle size is the main reason for the improvement of photocatalytic activity of red phosphorus.2.BiPO₄/RP composite photocatalyst was synthesized by simple adsorption-deposition method.The phase,surface chemical composition,morphology and optical properties of nano-red phosphorus were analyzed by X-ray diffraction,scanning and transmission electron microscopy,photoelectron spectroscopy and solid ultraviolet absorption.The flat band potentials of bismuth phosphate and red phosphorus are calculated by Mott-Schottky curve and the band width calculated by solid ultraviolet absorption is combined to give the possible energy level structure of bismuth phosphate/red phosphorus heterojunction.Under the same conditions,the photocatalytic reduction of Cr?VI?by BiPO₄/RP composites with different mass ratios,pure bismuth phosphate and nano red phosphorus under visible light irradiation were investigated.In addition,it also studied.According to the experimental results,when the mass ratio of red phosphorus to bismuth phosphate is 5:1?BiPO₄/RP-0.2?,the obtained material has the best photocatalytic activity.after 8 min of illumination under visible light,the removal rate of hexavalent chromium reaches 99%,and its reaction rate constant is 1.8 times that of nano red phosphorus.Research shows that bismuth phosphate can be used as an electron trap,improving the separation efficiency of carriers on the surface of red phosphorus and reducing the migration rate of photo-generated charges are the main reasons for improving the photocatalytic activity of bismuth phosphate/red phosphorus heterojunction.