The Construction Of The Visible Light Response Multi-valence Bismuth Containing Systems And Their Environmental Catalytic Application

Recently,the application of the photocatalytic techniques in wastewater treatment and soil remediation has attracted great concerns around the world.The rational design of the photocatalytic system and photocatalyst was of great importance.Among various of the photocatalysts,the bismuth-based material was intensively studied and became a hotspot in recent years.What has not been fully understood was the high chemical valence bismuth contained materials.It showed great potential to be utilized in practice due to their unique properties and good activity.However,limited investigations of high chemical valence bismuth contained material confined its further applications.In this thesis,efforts were made to synthesize Bi^（3+x）+containing materials in order to figure out the mechanisms for the enhanced photodegradation activity over the environmental pollutants.The non-stoichiometric Cu_0.84Bi_2.08O₄,p-n junction NaBiO₃/BiOCl and Bi₂O₄/BiOCl composition were applied for pollutants degradation for actual water treatment and soil remediation.The main works are summarized as follows:1.A novel Cu_0.84Bi_2.08O₄ was synthesized through a one-step aging method,which was analyzed by the XPS to determine the surface elements and their valence state.The Cu_0.84Bi_2.08O₄/PDS/visible light system was developed for efficient PDS activation under the visible light assistance to achieve the ciprofloxacin（CIP）removal.The trapping experiments and EPR were carried out to determine the oxidation species of the system,it was found that the sulfate radicals and hydroxide radicals were the main active radicals.The copper and high valence state metal were the active sites for sulfate radicals and hydroxide radicals generating,respectively.It was found that Cu_0.84Bi_2.08O₄/PDS/visible light system possessed great strengths over many other bismuth-based catalysis and PDS activation system.The DOC removal and the antibacterial activity of the CIP degradation products was evaluated.Despite the difficulty for accomplishing the mineralization of the CIP,the antibacterial activity of the products reduced about 95%,effectively eliminating the possibility for drug resistance.Furthermore,applied with the cycling experiment,this system showed high stability and reusability.Inductively coupled plasma mass spectrometry over the reaction solution before and after the reaction was tested,demonstrating that the low ions leaching was beneficial for the environment without causing secondary pollution.Through tuning the parameters during the CIP degradation,the effects of the PDS and CIP dosage,the amount of the catalyst,the pH,anion ions and the ions strength were carefully investigated.Meanwhile,the degradation of the Cu_0.84Bi_2.08O₄/PDS/visible light system over a series of the organics,such as the antibiotics,endocrine disruptor,pesticides and the dyes,was conducted,exhibiting its wide application.The degradation of the CIP in the actual river water was also conducted,exhibiting the good adaptability of the Cu_0.84Bi_2.08O₄/PDS/visible light system.2.A novel NaBiO₃/BiOCl composition was synthesized by an etching method under the room temperature.Characterized by HRTEM,Mott-Schottky curves,XPS,FTIR,Raman spectra and so forth,the as-prepared NaBiO₃/BiOCl photocatalyst was proved to be a B-type p-n junction.The heterojunction material exhibits good activity for CBZ degradation,and the trapping experiments and probing test demonstrated that the holes and the super oxide radicals were the main active species and minor active species during the photodegradation.The DRS spectra,the time-resolved PL spectra,EIS and transient photocurrent meansurements were conducted,showing that the NaBiO₃/BiOCl p-n junction possessed excellent electrochemical properties,thus exhibiting the improved separation of the carriers.The enhanced photodegradation activity of the NaBiO₃/BiOCl was attributed to the surface BiOCl promoting the transfer of the hole toward outside.Meanwhile,the process of the CBZ degradation is also proposed based on the HPLC-MS results,demonstrated the successful degradation over the CBZ.Meanwhile,the cycle experiment,ions leaching test and cytotoxicity measurement was conducted,exhibiting higher stability and the biocompatibility of the NaBiO₃/BiOCl compared with the single component.The degradation of CBZ was carried out in the three regions of the river water and lake water located at two areas,indicating that the effects of the water matrices might hinder the capability of the degradation but prolonging the reaction could achieve the identical results.The influence of the NOM and the ions was also measured to investigate the main factors for the variation of the activity.3.A novel Bi2O4/BiOCl composition was synthesized through a mild two-step method.By carrying out the photodegradation experiments,it was found that the Bi2O4/BiOCl composition showed the great photocatalysis activity for dyes（including RhB and MO）and antibiotics（CIP）removal both in the water system and on the surface of the soil.Meanwhile,it was also good for the total carbon removal.The enhanced activity is attributing to the high efficiency of the carriers separation and excellent current response,which is confirmed by the electrochemical characterizations.Besides,the good ability for the soil sample and humic acid（HA）sentisizing greatly improves the harness of the visible light,which was proved by the DRS spectra.The trapping experiment was conducted,demonstrating that the holes,·O₂^-,and·OH was the main active species of the Bi2O4/BiOCl.In the presence of the HA,the·OH played a minor role.The degradation over the organics mixture over the P25 and Bi2O4/BiOCl was also conducted,indicating the higher selective of the Bi₂O₄/BiOCl than that of the P25.