Study On The Preparation Of Metal Organic Framework Based Catalyst And Its Degradation Performance For Organic Micro-pollutants In Water

Advanced oxidation technology based on persulfate is a novel oxidization technology developed based on the traditional Fenton process,which shows a broad application prospect in the field of refractory organic wastewater treatment.Heterogeneous catalytic activation of persulfate has the advantages of higher efficiency,mild/non-pollution and simple synthesizing equipment,and the key of it is the development of efficient and stable catalysts.As a branch of Metal Organic Frameworks（MOFs）,Zeolitic Imidazolate Frameworks（ZIFs）has outstanding application properties like high activity,various structures and simple synthesis methods and has gradually become a hot material in studying on efficient heterogeneous catalytic materials.However,it shows some shortages like insufficient stability and low catalytic activation while directly used into activation of persulfate.Thus,in this thesis,using the Zeolitic Imidazolate Frameworks,ZIF-67 and ZIF-8,which are easy to synthesize,as the main part,we successfully synthesized three modified composited catalytic materials based on ZIFs through different methods respectively.It was characterized by Transmission electron microscopy（TEM）,Scanning electron microscopy（SEM）,X-ray diffraction（XRD）,X-ray photoelectron spectroscopy analyzer（XPS）,physical adsorption instrument（BET）to analyze the properties like morphology,structures and chemical composition of the materials.We studied the oxidative degradation performance of catalytic materials for organic micro-pollution in water system by activating PMS and further explored the catalytic mechanism.The specific research content as follow:The silica（SiO₂）was loaded on the surface of ZIF-67 by controlling the hydrolysis of tetraethoxysilane and subsequently calcined under inert atmosphere to obtain the yolk-shell carbon nanomaterials CZIF-67@SiO₂.The results showed that the morphology of precursor templates was retained.The Siand Co elements were uniformly dispersed.The degradation performance of the catalyst for the microscale Rodamine B（Rh B）in water system by activating PMS was studied.Additionally,the factors affecting the PMS activation such as temperature,catalysts dosage,PMS concentration and p H value in degrading Rh B reaction system were also investigated.When the concentration of CZIF-67@SiO₂ and Rh B was 0.04 g/L and 0.05 g/L,the degradation efficiency of Rh B could reach 100%in 20 min.After 4 times recycling,the removal efficiency could still be 80%.Besides,the catalytic mechanism was analized by quenching test and electron paramagnetic resonance（EPR）.The results showed that ¹O₂ was the dominant active species involving in the degradation process.The ZIF-67 was loaded on the polystyrene（PS）spheres templates and subsequently doped with Cu by impregnation method.Then,the hollow sphere carbon material Cu-Co/NC was obtained by pyrolysis.The degradation performance for microscale 4-nitrophenol（4-NP）in water system by activating PMS was investigated.Factors that affect 4-NP degradation were examined,including the catalyst and PMS dose,solution p H,temperature and initial concentration of 4-NP.The results showed that the degradation efficiency was 90%in 40 min when the dose of catalysts and4-NP was 0.1 g/L and 0.025 g/L.The catalyst could be easily recycled and had good stability and reusability.Meanwhile,it was found that^·SO₄^-is the main reactive species participating in 4-NP degradation by activating PMS.ZIF-8 was loaded on PS spheres surface and then the yolk-shell hollow porous carbon CPS@ZIF-8 was synthesized.The catalyst had high N content and large specific surface area and pore volume（1301 m²/g and 1.12 cm³/g）.The phenol degradation performance of the catalyst by activating PMS was studied.The effects of operation conditions such as the catalyst and PMS dose,phenol concentration,initial p H and temperature on phenol removal were investigated comprehensively.Moreover,the main reactive species involved in phenol oxidation were investigated,and a plausible mechanism for the degradation of phenol was proposed.The results showed that CPS@ZIF-8 exhibited an excellent phenol adsorption and degradation performance.Both the nonradical pathway（¹O₂）and the radical pathway（^·SO₄^-and^·O₂^-）were found to be involved in the decomposition of phenol.