Detection And Removal Methods Of Pollutants Based On Metal-organic Framework Composite Materials

Metal organic framework materials(MOFs)are rich in microporous structure,high specific surface area,adjustable pore size and structure.However,the weak electrical conductivity and poor hydrothermal stability restrict the application of single-phase MOFs in many fields.In order to avoid these,functionalized materials or modified MOFs are introduced to prepare MOFs composites.MOFs composite materials can make full use of the excellent properties of the guest functionalized materials,as well as the highly selective adsorption and high-efficiency accumulation capabilities of the host MOFs.MOFs composite materials not only retain the original excellent characteristics of MOFs,but also utilize the advantages of other single-phase materials.MOFs composite materials have broad application prospects and practical application value,and have been widely used in lighting,information storage,food quality control,biological monitoring and imaging,chemical threat detection,environmental pollution analysis and other fields.In the field of environmental pollution analysis,the development of MOFs composite materials and the research on the detection and removal of environmental pollutants have become a hot topic.In this paper,three kinds of MOFs composite materials are prepared by encapsulation method and solvothermal method.These materials are used for the detection of Cr(?)and removal of OFX in water,respectively.The specific research contents are as follows:(1)Preparation of UiO-66@BPEI-CDs composite material based on UiO-66 and application in Cr(?)detection:UiO-66@BPEI-CDs fluorescent probe was prepared by combining BPEI-CDs with high luminescence quantum yield and UiO-66 with high water stability through encapsulation method.The composite material combined the high photoluminescence properties of BPEI-CDs and the porous structure characteristics of UiO-66(pore size:15.40(?)).Cr(?)has a significant fluorescence quenching on the probe,which can realize the detection of Cr(?).The fluorescence performance and crystal structure of UiO-66@BPEI-CDs were analyzed by ultraviolet-visible spectrophotometer(UV-Vis),time-resolved fluorescence spectrometer,Fourier transform infrared spectrometer(FT-IR),X-ray diffractometer(XRD)and energy dispersive spectrometer(EDS).The results showed that the XRD spectra of UiO-66@BPEI-CDs and UiO-66 were consistent,indicating that the loading of BPEI-CDs did not change the crystal structure of UiO-66.This experiment optimizes the detection conditions,the optimal conditions are:UiO-66 concentration:4 mg/m L,p H=4,and reaction time:5 min.Under the optimal conditions,the linear range of UiO-66@BPEI-CDs for Cr(?)detection are 0.05?0.25?mol/L(R²=0.999)and 0.75?8?mol/L(R²=0.999),and the detection limit is 0.044?mol/L.The selectivity of UiO-66@BPEI-CDs on Cr(?)detection was testing by comparing with other metal ions(Co²⁺,Cr³⁺,Cu²⁺,Fe²⁺,Fe³⁺,Ca²⁺,Zn²⁺,Mg²⁺,Pb²⁺,Ba²⁺,K⁺,Li⁺,Ag⁺,Al³⁺?Hg²⁺).The anti-interference ability of UiO-66@BPEI-CDs was investigated in the presence of(SO₄^2-,CO₃^2-,HPO₄^2-,HCO₃^-,H₂PO₄^-,Cl^-,I^-and Br^-).Finally,the fluorescent probe was used to detect Cr(?)in lake water and tap water.(2)Preparation of UiO-66@RhB composite material based on UiO-66 and application in ofloxacin(OFX)detection:UiO-66@RhB ratio fluorescent probe was prepared by combining the fluorescent dye Rhodamine B(RhB)with high water stability MOFs(UiO-66)through encapsulation method.The probe showed double emission peaks at 395 nm and 585 nm under the excitation wavelength of 270 nm.After OFX adding,the fluorescence intensity of the probe decreased at 395 nm and increased at 585 nm.The quantitative detection of ofloxacin can be realized according to the change of fluorescence ratio.In this paper,the morphology and crystal structure of UiO-66@RhB were characterized by scanning electron microscopy(SEM),energy dispersive spectrometer(EDS),Fourier transform infrared spectroscopy(FT-IR),X-ray diffraction(XRD)and other means.The characterization results showed that the morphology and size of UiO-66 did not change significantly after loading RhB.This experiment optimizes the detection conditions,the optimal conditions are:UiO-66@RhB concentration:0.6 g/L,p H=6,and reaction time:2 min.Under optimal conditions,the linear range of UiO-66@RhB for OFX detection is 0.05?0.8 mg/L(R²=0.999),and the detection limit is 0.022 mg/L.The selectivity of UiO-66@RhB on OFX detection was testing by comparing with other antibiotics(CIP,SMZ,TC,ENR,NOR).The anti-interference ability of UiO-66@RhB was investigated in the presence of(Cu²⁺,Fe³⁺,Zn²⁺,Mg²⁺,Ag⁺,Al³⁺,Hg²⁺,Cl^-,I^-SO₄^2-,CO₃^2-,HPO₄^2-and Br^-).Finally,the ratio fluorescent probe was used to detect OFX in lake water and tap water.(3)Preparation of UiO-66/wood composite material based on UiO-66 and application in ofloxacin(OFX)degradation:One-step solvothermal method was used to synthesize the new photocatalyst UiO-66/wood,and it was applied to the photocatalytic degradation of OFX under simulate sunlight.The crystal structure and chemical composition of UiO-66/wood were further analyzed by scanning electron microscope(SEM),Fourier transform infrared spectroscopy(FT-IR),Raman spectroscopy,X-ray diffraction(XRD)and energy dispersive spectrometer(EDS).For the photocatalytic elimination of OFX,UiO-66/wood exhibited good removal efficiency and reusability:After 4h simulated sunlight radiation,the degradation rate of OFX reaches 75.3%.The recycle experiment showed that after 4 cycles,the photocatalytic performance of UiO-66/wood is not significantly reduced and the crystal structure is not destroyed.Mechanism studies have shown that the adsorption and photocatalysis played an important role in the degradation of OFX by UiO-66/wood.The main active free radicals are superoxide radicals(·O₂^-)and hydroxyl radicals(·OH).OFX photodegradation pathway and product toxicity studies showed that the toxicity of product is lower than the initial pollutant.UiO-66/wood showed good photocatalytic degradation efficiency for ofloxacin in actual water samples,indicating that it has great potential in actual wastewater treatment.