The Efficacy And Mechanism Of Nanoferrihydrite Catalyzed By Persulfate To Remove Butyl P-hydroxybenzoate In Water

With the rapid development of the economy,more and more emerging organic contaminants enter the environment through human activities,which brings potential risks to the ecological environment and human health.Emerging organic pollutants,represented by pharmaceuticals and personal skin care products（PPCPs）,have attracted more and more attentions by researchers.Parabens are widely used as preservatives as a type of PPCPs.Studies have shown that long-term use of parabens has a certain harmful effect on the reproductive system of humans and organisms.The existing sewage or sludge treatment plant processes are ineffective to remove PPCPs from water bodies or sludge.Therefore,it is a hot research topic to find an advanced oxidation technology based on new functional materials to effectively remove PPCPs from water.Heterogeneous persulfate advanced oxidation technology as an emerging oxidation technology,in which catalytic degradation process has attracted extensive attention from experts in the environmental field.However,secondary pollution caused by the release of metal elements in heterogeneous catalysis has plagued researchers.In this thesis,NFH/PMS system was used to study the degradation of Butyl p-Hydroxybenzoate（BHB）by nanoferrihydrihydrite（NFH）.The research contentsmainlyinclude:preparationofnanoferrihydrihydrite（NFH）by co-precipitation method,and using field emission scanning electron microscopy（SEM）,infrared spectroscopy（FTIR）,X-ray powder diffractometry（XRD）and X-ray photoelectron spectroscopy（XPS）The characterization method was used to characterize the prepared nanoferrihydrihydrite;the effects of reaction temperature,pH,material dosage and calcination temperature on the reaction system were investigated;coexisting ions were investigated.The identification and analysis of the active species in the reaction system,and the changes of the morphology and elements before and after the reaction,and further deducing the possible generation path of the active species.The main findings are as follows:（1）NFH can be prepared by precipitation method.The direct adsorption of BHB by this catalyst is low,but the reaction rate is obviously accelerated after the catalytic oxidation of oxidant PMS.When the calcination temperature is 723 K,the NFH catalyst shows the best catalytic degradation.（2）The reaction temperature,material dosage,initial pH and dissolved oxygen in water have different effects on the NFH/PMS catalytic system.The alkaline conditions are more favorable for the reaction than the acidic conditions.The aerobic conditions are more favorable than the anaerobic conditions.The reaction proceeds,and intermittent aeration is more favorable to the reaction than continuous aeration.（3）In the material stability and repeatability experiments,the highest release concentration of iron ions is 0.13 mg/L,which is less harmful to the environment.The removal rate can be more than 80%after repeated three times.（4）The inorganic anions PO₄^3-,Cl^-and HCO₃^-have a great influence on the NFH/PMS catalytic removal of BHB:PO₄^3-has a continuous inhibitory effect on the reaction system,Cl^-and HCO₃^-have a synergistic effect on the reaction.The effect of NO₃^-on the removal of BHB is relatively weak.（5）The degradation of BHB by the NFH/PMS system is a free radical reaction process involving not only SO₄^·-and^·OH,but also ¹O₂ and O₂^·-active species.XPS results showed that the valence of Fe element changed before and after the reaction,and the content of O element changed before and after the reaction,indicating that both Fe and O were involved in the reaction.（6）The possible pathway of NFH/PMS catalytic degradation of BHB is accomplishedbyROSshydroxylation,carboxylation,decarboxylation,dehydrogenation,ring opening and chain scission.