Preparation And Photocatalytic Degradation Of Bi₄O₇/Cu-BiOCl/Cotton Functional Fabric

Organic pollutants in the water have the problems of poor biodegradability and high toxicity,which seriously affect human health and environmental safety.Semiconductor photocatalysis technology can remove some pollutants in the water environment at room temperature with the help of solar energy,which is an environmentally friendly treatment technology that can effectively remediate water pollution.Among many semiconductor materials,bismuth-based semiconductor is a kind of photocatalytic material with mild reaction conditions,low cost and high stability.However,when used as a powder,there are problems of easy agglomeration and poor recycling.In this study,Cu-BiOCl was prepared by Cu²⁺doping,and Bi₄O₇/Cu-BiOCl type II heterojunction was constructed to improve the photocatalytic performance of bismuth-based semiconductors.The prepared Bi₄O₇/Cu-BiOCl was loaded on cotton fabric to solve the problem that powder materials are prone to agglomeration and improve their recycling in the application process,thus further broadening the practical application field of bismuth-based semiconductor materials.The research work includes four aspects:（1）Preparation of Bi₄O₇/Cu-BiOCl materials.The Bi₄O₇/Cu-BiOCl materials were prepared by hydrothermal method,and the effects of Cu²⁺doping,temperature and mass ratio of Bi₄O₇and Cu-BiOCl on the photocatalytic activity of Bi₄O₇/Cu-BiOCl materials were investigated using tetracycline（TC）and reactive dye（RB-19）as degradation substrates.The results showed that the Bi₄O₇/Cu-BiOCl material possessed the best photocatalytic performance with high efficiency for TC and RB-19 removal when the Cu²⁺doping ratio was 25%,the calcination temperature was 400℃and the Bi₄O₇:Cu-BiOCl=10:1（mass ratio）.（2）Characterization and analysis of Bi₄O₇/Cu-BiOCl materials.The microscopic morphology of Bi₄O₇/Cu-BiOCl materials was characterized by SEM and TEM,and it was demonstrated that Cu-BiOCl nanosheets were successfully loaded onto the surface of irregular nanosheets Bi₄O₇,the crystal structure and functional groups of the prepared samples were examined.by XRD and FT-IR,and it was demonstrated that Bi₄O₇ has high crystallinity and Bi₄O₇/Cu-BiOCl contains both Bi-O and Bi-Cl characteristic peaks.The surface composition and atomic valence states of Bi₄O₇/Cu-BiOCl materials were analyzed by XPS and EDS,and it was demonstrated that Bi,Cl,O and Cu elements were uniformly dispersed,and Cu²⁺was doped into BiOCl and successfully compounded with Bi₄O₇;the photoelectric properties of Bi₄O₇/Cu-BiOCl materials were analyzed by photoelectrochemical tests（UV-Vis DRS,EIS,PL,etc.）,which showed that the photocatalytic properties of Bi₄O₇/Cu-BiOCl materials were improved compared with both Bi₄O₇ and Cu-BiOCl.（3）Inference of degradation mechanism of Bi₄O₇/Cu-BiOCl materials.The degradation tests of TC and RB-19 showed that the degradation mechanism of Bi₄O₇/Cu-BiOCl is the synergistic effect of physical adsorption and photochemical reaction.The conduction band position(E_CB)and valence band position(E_VB)of Bi₄O₇ and Cu-BiOCl were analyzed by Mott-Schottky to know that both Bi₄O₇ and Cu-BiOCl are n-type semiconductors.Based on the position relationship of the energy band and the possible transmission path of photogenerated electrons,it was speculated that the Bi₄O₇/Cu-BiOCl type II heterojunction was successfully constructed,and the possible photocatalytic reaction mechanism was proposed.ESR test and free radical capture experiment proved that photogenerated holes（h⁺）and superoxide radicals（·O₂^-）were the main active species in the degradation reaction,while·OH only played a supporting role.The intermediates produced during the degradation of TC were analyzed by LC-MS and 3D EEM to deduce the possible degradation pathway.（4）Preparation and application performance analysis of Bi₄O₇/Cu-BiOCl/cotton functional fabric.Due to the problem of easy agglomeration of powder semiconductors,Bi₄O₇/Cu-BiOCl materials were loaded onto cotton fabrics by impregnation method to improve recycling.The prepared Bi₄O₇/Cu-BiOCl/cotton functional fabric was used to remove TC and RB-19,and the results showed that the degradation rates of both TC and RB-19 were maintained above 80%after five cycles of degradation experiments.