Preparation Of Manganese-based Porous Nanofiber Materials And Their Formaldehyde Purification Properties

Harmful gases（e.g.formaldehyde）can harm the human respiratory system,skin and nervous system,causing injury or death.In order to solve the problems of low catalytic efficiency caused by the easy agglomeration of nanocatalytic materials and the easy failure of catalysis at low formaldehyde concentrations,this project uses nanofibres as the substrate and adopts the double sol-gel system electrostatic spinning technology to design a functional composite nanofibre material that integrates adsorption and catalysis and to study its formaldehyde gas purification performance,which is mainly divided into the following three parts.In the first part,electrostatic spinning was carried out using a three-needle X-axis circular round-trip device to explore the conformational relationship between ZIF-8 nanoparticles and SiO₂ nanofibres,to prepare ZIF-8-SiO₂ porous nanofibre membranes,to compare and analyse the stability performance of ZIF-8 nanoparticles loaded on SiO₂ flexible porous nanofibre materials before and after grafting,and to investigate the influence of the synthesis process on the loading state of ZIF-8 nanoparticles.The results showed that the ZIF-8 nanoparticles on SiO₂ flexible porous nanofibers were well formed and the ZIF-8 nanoparticles were uniformly distributed in the SiO₂ flexible porous nanofiber network by in situ loading of ZIF-8nanoparticles at room temperature for 12 h.The results showed that the ZIF-8 nanoparticles on SiO₂ flexible porous nanofibers were well formed;SiO₂ flexible porous nanofibres fully formed with ZIF-8 nanoparticles after only 8 h of in situ loading using APTES grafting;The ZIF-8nanoparticles were almost completely detached from the fibres by sonication at 100 Hz for 5min,while a small amount of ZIF-8 nanoparticles were still present on ZIF-8-SiO₂ porous nanofibres loaded with ZIF-8 nanoparticles in situ at room temperature for 12 h.The permeability of ZIF-8-SiO₂ porous nanofibre membranes became less permeable with increasing loading time.In the second part,ZIF-8-SiO₂ convoluted porous nanofiber materials were prepared by a secondary growth method using a circular round-trip spinning device with a double sol-gel system.The effects of the volume ratio of each system of the spinning precursor and the mass fraction of the templating agent on the curl morphology of the fibres in the fibrous web were investigated.The loading of ZIF-8 nanoparticles in ZIF-8-SiO₂ porous nanofibre materials and the tensile strength properties of the two fibrous films were compared.The results show that:two types of porous nanofiber materials with different fiber diameters were prepared using a precursor solution with a volume ratio of zinc acetate sol:SiO₂ sol=1:2.The results show that two porous nanofiber materials with different fiber diameters were prepared by using a precursor solution with a volume ratio of zinc acetate sol:SiO₂ sol=1:2,and the fibers showed a curled morphology after calcination at 600℃;Compared to the ZIF-8-SiO₂ porous nanofibre material,the ZIF-8-SiO₂ coiled porous nanofibre material has a shorter preparation time,a higher loading of up to 12.7%and a tensile elongation of up to 2.26%,but its tensile strength is poorer at 0.54 MPa.In the third part,manganese-based porous nanofiber materials were prepared by in situ synthesis of aqueous sodium manganese-type manganese dioxide on SiO₂ flexible nanofibers,ZIF-8-SiO₂ nanofibers and ZIF-8-SiO₂ coiled nanofibers using a hydrothermal in situ growth method.To investigate the effect of Mn O₂-SiO₂ flexible porous nanofiber materials on the degradation efficiency of formaldehyde under different experimental bath ratios（1:100,1:500and 1:1000）and to study the performance of ZIF-8 nanoparticles in synergistic catalytic degradation of formaldehyde with aqueous sodium manganese ore-type manganese dioxide.The results show that the Mn O₂-SiO₂ flexible porous nanofiber material has the best catalytic performance at a bath ratio of 1:1000,and the catalytic performance for formaldehyde can reach55.6%;The degradation efficiency of the nanofibrous material was found to be enhanced by the loading of ZIF-8 on the fibrous material at an experimental bath ratio of 1:1000;Mn O₂-ZIF-8-SiO₂ convoluted porous nanofibre material showed the highest degradation efficiency of77%for formaldehyde and the best performance in the degradation of catalytic formaldehyde;Mn O₂-ZIF-8-SiO₂ porous nanofibre material showed poor catalytic performance against formaldehyde,with a formaldehyde degradation efficiency of 72.2%;The Mn O₂-SiO₂ flexible porous nanofibre material was the worst,with a formaldehyde degradation efficiency of only55.6%.The adsorbent（ZIF-8）and catalyst（Mn O₂）are simultaneously loaded on electrostatic spinning fibres,using ZIF-8 to enrich the concentration of formaldehyde and improve the effective contact between formaldehyde and Mn O₂,thus enhancing the removal performance of composite nanofibre materials for formaldehyde and reducing the harm of formaldehyde gas to human beings,which is of indispensable significance to the improvement of human living environment and the development of ecological civilisation.