Optimized Preparation Of PAN Nanofiber Metal Complexes And Its Catalytic Performance Control Method

Catalysts supported on nanofibers have drawn widely attentions for their various applications in new energy conversion and ecological environment purification due to extraordinary catalytic properties,especially modified polyacrylonitrile nanofiber(n-PAN)based heterogeneous Fenton catalyst in the removal of persistent organic pollutants such as organic dyes.In order to achieve better application of heterogeneous Fenton catalyst and promote its effective regulation,we optimized the coordination structure and the physical form by preparing double-scale PAN nanofibers,bimetal ions coordination reaction and the synergy effect of adsorption-catalysis.Furthermore,modified n-PAN bimetal complex,modified double-scale n-PAN metal complex and adsorption-catalytic bifunctional modified n-PAN Fe complex were constructed,and their catalytic property to specific dye degradation were investigated to develop high performance heterogeneous Fenton reaction catalysts.Moreover,the dye molecules oxidative degradation in modified n-PAN Fe complex/H2O2 system was investigated.And the activated effect of modified n-PAN Fe complex on sodium persulfate was studied to develop activated sodium persulfate with better oxidative degradation performance.The results of various characterizations and data fitting were as following.(1)Different metal ions including Fe3+ ions,Cu2+ ions and Ce3+ ions could coordinate with AO-n-PAN to prepare nanofiber metal complexes.The elevation of reaction temperature and initial concentration favored the metal content increasing,and ranked in the order:Fe3+>Cu2+>Ce3+ under the same conditions.Langmuir isothermal model and pseudo-second-order kinetic model fitted well the coordination between metal ions and AO-n-PAN.And the resulting complexes used as heterogeneous Fenton catalysts showed good catalysis in the degradation of azo dyes in a wide pH range from 3 to 9.High metal content enhanced their catalytic performance and AO-n-PAN Cu complex showed the best catalytic efficiency in alkaline conditions.(2)The increasement of initial metal ions concentration promoted the metal content in the coordination between Fe-Cu bimetal ions solution and AO-n-PAN.There were simultaneouly competition and synergy effect between the two metal ions.The added Cu2+ ions as a brige improved the coordination of Fe3+ ions due to their lower positive charge and ionic radius,and the improvement effect increased with increasing Cu2+ions concentration.On the contrast,Fe3+ ions impeded the coordination of Cu2+ ions and the impeded effect aggravated with the elevation of Fe3+ ions concentration.Langmuir-Freundlich isothermal model fitted well the coordination between bimetal ions solution and AO-n-PAN.The addition of Cu2+ ions enhanced the dye adsorption property of Fe-Cu-AO-n-PAN and tolerance to alkaline environment as well as reuse performance.And eventually efficient removing dyes from solution could be achieved by the synergy effect between Fe3+ ions and Cu2+ ions.(3)Double-scale n-PANs with different diameter distribution were prepared by adjusting the electrospinning process parameters.The large scale nanofiber as framework reduced the bulk density of nanofibers,whereas the small scale nanofiber improved the pore structure due to their low volume and enhanced the adsorption performance,thus favoring the modification degree and affinity to Fe3+ ions and eventually resulting the excellent catalytic and reuse ability of the obtained double-scale AO-n-PAN Fe complex.(4)A seriers of adsorption-catalytic bifunctional modified n-PAN Fe complexes were fabricated by modifying n-PAN with different concentrations of the mixed solution of hydroxylamine hydrochloride and hydrazine hydrate and subsequently coordinating with Fe3+ ions.The addition of hydrazine hydrate increased the crosslinkage between PAN chains.Nevertheless,the increased amount of hydrazine hydrate decreased the degree of modification and the adhesions of nanofibers,as well as the Fe content during the coordination reaction.Good dye adsorption on different modified n-PANs elevated with increasing the amount of hydrazine hydrate,and further enhanced by Fe3+ ions on the surface of complex.In the degradation of Reactive Red 195.not only the good adsorption performance but also the synerigy between adsorption and catalysis were responsible for the fast removal of dye molecular.The modified n-PAN Fe complexes as adsorption-catalytic bifunctioanal materials were of high stable and reusable.(4)Modified n-PAN could acrivate sodium persulfate and the activated effect was further enhanced after coordinating with different metal ions,especially for Fe complex.The introduction of irradiation and high Fe content favored the activated ability of modified AO-n-PAN Fe complex and possessed better catalytic performance to the degradation of dyes than H2O2 system at pH=9.There were three kinds of radicals including ·OH,SO4-and O2-during the heterogeneous activated sodium persulfate system,and the contributions of ·OH was the highest.Adding H2O2 in modified AO-n-PAN Fe complex activating sodium persulfate system formed the bioxidation system,and the synergistic effect between H2O2 and sodium persulfate led to its higher catalytic degradation performance.