Studies On Adsorption/Photocatalysis Of Typical PPCPs By Bismuth Oxyhalides

Pharmaceutical and Personal Care Products(Pharmaceuticals and Personal Care Products,PPCPs)were continually detected in the water environment in the last decades.Even though the concentration is low,the accumulation of PPCPs would do harm to water ecosystem and people’s health,therefore it is very urgent to remove PPCPs from water.In this dissertation,Bismuth Oxyhalides(BiOX,X =Cl,Br,I)were used as adsorbent and photocatalyst to study its performance and mechanism on the removal of PPCPs.Thus new methods and technologies were further proposed.The adsorption/UV light photocatalytic performances of BiOCl microspheres in the removal of Ibuprofen(IBP)were first studied.BiOCl has been synthesized through typical solvothermal process and characterized by X-ray Diffraction(XRD),Scanning Electron Microscope(SEM),Transmission Electron Microscope(TEM),High-Resolution Transmission Electron Microscope(HRTEM),N2 adsorption-desorption,UV-Visible Disffuse Reflectance Spectroscopy(UV-Vis DRS)to obtain physicochemical and optical properties.Reaction parameters on the IBP removal rate were studied.Other than the conclusions reported from previous papers,the results suggested that the photocatalytic oxidation efficiency of BiOCl is highly adsorption-dependent,of which the adsorption accounts for over 90%.The adsorption kinetics was well fitted to Freundlich isotherm and Langmuir isotherm,and the adsorption processes were well fitted to second-order kinetic equation,with its correlation index R2 over 0.99.The adsorption/visible light photocatalytic performances of BiOBr microspheres in the removal of IBP were also studied.The results suggested that the photocatalytic oxidation efficiency of BiOBr is highly adsorption-dependent,of which the adsorption accounts for over 80%.Further experiments on Ion Chromatography(IC),Inductively Coupled Plasma-Mass Spectrometry(ICP-MS),Fourier Transform Infrared(FT-IR),and X-ray Photoelectron Spectroscopy(XPS)proved that the anion exchange between Br-anions from hydrolysis of BiOBr and dissociated IBP followed by the formation of O-Bi-O bond by carboxyl-COOH on the surface of BiOX is the main adsorption mechanism.The experiments on the selective adsorption of PPCPs pollutions by BiOBr further proved the hypothesis and perfected the adsorption mechanism.Further experiments on the combination of BiOX + peroxides in the removal of Carbamazepine(CBZ)were also conducted.The results showed that the combination of BiOBr + PMS exhibited better performance in the degradation of CBZ,which can degrade CBZ woth concentration of 5 μM in 5 min.It was found that CBZ degradation was primarily(67.3%)attributable to the attack by sulfate radical.Reaction parameters such as additional anions,HA concentration,solution pH,and water backgrounds on the degradation of CBZ were also investigated.The CBZ degradation by BiOX activated peroxide was caused by the attack of sulfate radicals,which was generated from the PMS with the help of Bi(III)-Bi(V)-Bi(III)redox cycle.Substitution of the hydroxyl groups and direct complexation with the Bi(III)on the surface of the catalyst particles were found to be involved in the decomposition of the PMS.Experiments on Electron Paramagnetic Resonance(EPR),IC,XPS,and FT-IR further proved the mechanism.Different parameters(anions,HA concentration,solution pH,water background)would also affect the CBZ degradation performance.Based on the TOC and LC-MS results above,we noticed that the mineralization of the target pollutant by BiOX photocatalysis was relatively low.We further combine the bismuth oxychloride BiOCl,PMS and ultraviolet light UV to enhance the mineralization of CBZ.The results showed that the combination of BiOCl + PMS +UV was able to enhance the mineralization of CBZ to approximately 90%with low luminous flux 550 μW/cm2.The EPR detection proved that the hydroxyl radical ·OH played an important role in the degradation.LC-MS was used for the further analysis of degradation intermediates and the degradation pathway was proposed.Moreover,the combination of BiOCl + PMS + UV was used in the degradation of typical PPCPs and the mineralization were all over 90%,which could be applied in practical use.