Synthesis Of Mesoporous Silica Nanomaterial And Its Catalytic Performance For Persulfate

Mesoporous silica has been commonly used in catalysis as carriers due to its high specific surface area,excellent hydrothermal stability and varied preparation methods as well as environmental friendly,and cycling stability.Persulfate,which is typical oxidants,has been proved feasible in the advantage of chemically stable properties,simplicity of storage transportation,and cost-effectiveness.However,with its poor oxidation capacity,persulfate required a certain activation,in which transition metal activation used commonly.In this study,mesoporous silica was prepared by the surface-protected etching method.Based on that,magnetic mesoporous silica spheres(MMSS),mesoporous silica-doping copper oxide(Cu O/MSS)and mesoporous silica-doping copper-aluminum(Cu-Al/MSS)catalyst were prepared and used for exploring the catalytic performance of persulfate as well as its reaction mechanism.Compared with magnetic silica spheres(magnetic SS),MMSS showed a higher specific surface area as 161.14 m²/g(four more times than magnetic SS)as well as high-loading supported iron oxide(Fe₃O₄)nanoparticles as 32.67 wt%(one more time than magnetic SS)with soluble iron as 6.75 mg/L.According to the free radical capture experiment,the main active species was sulfate radical(SO₄^·-)at p H 5 while both sulfate radical(SO₄^·-)and hydroxyl radical(·OH)as the dominant radicals at p H 9.After five-run catalyst reclying text,MMSS still obtained 90%of the removal efficiency and could easily be isolated by using an external magnet.The results showed an excellent stability of MMSS.Comparing the catalytic activity between MMSS and Cu O/MSS,the latter achieve faster.The Cu content of Cu O/MSS was 57.74 wt%(one more time than Cu O/SS)while the soluble copper ions was 0.27 mg/L.Prior to supporting materials,doped materials creating has obviously unique catalytic performance.For example,it strengthened copper oxides(Cu O)connections with mesoporous silica to expose more active sites during catalytic process leading to increased catalytic efficiency.After five-run catalyst reclying text,without any change of the oxidized state of Cu²⁺and the soluble copper irons was 0.073 mg/L.The results showed a good stability and environmental benefits of Cu O/MSS.To confirm the catalytic performance of the Cu O/MSS+PDS system,the highly effective in degradation of Bisphenol A(BPA)was 83.0%in acidic conditions while 90.34%under alkaline conditions to the beneficial removal efficiency of BPA.The reaction mechanism was assessed via radical and non-radical pathway,the main pathway was non-radical at the initial p H of 5,in which BPA combined with Cu(II)to form coordination complexes.Cu(II)has improved the electronegativity of benzene ring and electron transferred directly from persulfate ions(S₂O₈^2-)to these complexes for BPA degradation.By contrast,radical pathway dominated catalytic oxidation at p H 9,persulfate ions were converted to sulfate radical and hydroxyl radical contributing to BPA degradation.Cu-Al/MSS had a higher catalytic ability than Cu O/MSS,by which almost 90%of BPA was removed within 30 min.The rate constant of Cu-Al/MSS/PDS system was0.075 min^-1(two more times than Cu O/MSS+PDS)and the soluble copper irons was0.13 mg/L.Due to the fact that galvanic effect of copper-aluminum with potential difference,which forms electron-rich copper and electron-poor aluminum active sites.Therefore,BPA was preferentially accumulated with Cu(II)to form coordination complexes around the electron-poor copper centre,which accelerated a high-efficiency process.