Study On The Performance And Mechanism Of Multi-shelled NiO Nanoreactor For Nanoconfined Catalytic Degradation Of Bisphenol A

Advanced oxidation processes based on persulfate（PS-AOPs）have been widely used in the degradation of refractory organic pollutants in water on account of their strong oxidation capacity,mild reaction conditions.Compared with the traditional free radical(OH^·、SO₄^·-)oxidation,non-radical oxidation mechanism based on electron transfer process（ETP）has attracted extensive attention in recent years due to its high selectivity and strong anti-interference ability.However,the catalytic decomposition efficiency of organic pollutants still needs to be improved due to its inherent mild oxidation capacity.In order to strengthen the catalytic reaction kinetics of nonradical oxidation,the hollow multi-shelled structure（Ho MSs）Ni O mesoporous nanoreactor were designed to activate peroxydisulfate（PDS）to degrade endocrine disruptor bisphenol A（BPA）.The Ho MSs of the Ni O nanoreactor was used to improve the utilization efficiency of the active site and the local concentration of the reactant,thus improving the catalytic degradation efficiency of BPA.The main research contents and conclusions of this thesis are as follows:（1）Based on the coordination chemistry principle of tannic acid（TA）,the Ni-TA complex nanospheres were synthesized by sol-gel method,and the Ni O hollow nanospheres with adjustable layers were synthesized via calcing at different temperatures.The physicochemical properties of the nanospheres were characterized by various techniques.Scanning electron microscope（SEM）,transmission electron microscope（TEM）analysis showed the Ho MSs of Ni O nanospheres,the X ray photoelectron spectroscopy（XPS）and solid electron paramagnetic resonance（EPR）results showed that each catalyst contained different concentrations of surface oxygen defects,and the concentration of defects increased gradually with the increase in temperature.（2）The catalytic performance of different multi-shelled Ni O nanoreactor/PDS systems was investigated,including BPA degradation performance,PDS decomposition performance and BPA mineralization degree.The catalytic experiments showed that the degradation kinetics and total organic carbon（TOC）removal rate of BPA by 2-shelled Ni O were 4 times and 1.8 times higher than that of Ni O nanoparticles（Ni O NPs）,respectively.Moreover,increasing the shell number to 3 could further improve the degradation kinetics of BPA and the removal efficiency of TOC.The results of kinetic experiments showed that the catalytic performance of the multi-shelled Ni O nanoreactor were mainly due to the nanoconfinement effect of the Ho MSs.（3）The performance of BPA by activated PDS in the multi-shelled structure Ni O nanoreactor were investigated under different reaction conditions（e.g.,PDS dosing,catalyst dosing,initial p H）,different environmental factors（inorganic ions,natural organic matter）,and different actual water conditions,the cyclic stability of the nanoreactor was evaluated by cyclic regeneration experiments.The results showed the Ni O nanoreactor（3-shelled Ni O）catalyst has a good PDS decomposition efficiency,and could remove many organic pollutants,including BPA,Phenol,acetaminophen（AAP）,sulfamethoxazole（SMX）,sulfadiazine（SDZ）,efficiently at[PDS]/[BPA]=2.5:1,and had good activity in the p H range of 3-12;the inorganic anions and humic acid in simulated water had insignificant effect on the degradation of BPA;the 3-shelled Ni O/PDS system maintained a good performance in groundwater,surface water,and secondary effluent.（4）The chemical quenching experiments and EPR tests demonstrated that non-free radical oxidation based on electron transfer was the main way of BPA degradation.XPS,in situ ATR-FTIR,Raman,DFT calculation and electrochemical analysis showed that the O_V was the main active site for the activation of PDS in the nanoreactor.PDS first adsorbed on O_V to form surface active complexes,and then selectively attracted electron-rich BPA and oxidized it.Finite element method（FEM）calculation indicated that the Ho MSs improved the utilization rate of oxygen defects at the active site of Ni O surface catalysis.On the other hand,the nanoconfinement effect of the multi-shelled structure significantly increased the local concentration of BPA and its degradation intermediates,and thus improved the catalytic reaction kinetics of BPA.The degradation of BPA mainly occurred via hydroxylation,single electron transfer and strong oxidation.