Research On Synthesis Of Mesoporous Nano-silica From Vanadium Tailings

Stone coal vanadium tailing is a solid waste produced by vanadium extraction process.With the growing demand for vanadium products,the amount of vanadium tailing emission is gradually increasing in China,especially 1 t V2O5 can produce 200 t vanadium tailings.However,the traditional disposal method of vanadium tailings is more than 90% piled up in the tailings and the comprehensive utilization rate is relatively low,so the vanadium industry faced with the pressure of sustainable development.In addition,the traditional synthesis method of ordered mesoporous silica takes tetraethyl orthosilicate as silicon source,which has high cost and thus limits the large-scale application of mesoporous materials.The vanadium tailing is an ideal silicon source for synthetic mesoporous silica because of its characteristics of high silicon,low aluminum and low carbon.Therefore,from the perspective of highvalue utilization,environmental protection and sustainable development,this thesis took vanadium tailings as silicon source to prepare ordered mesoporous nano-silica with different structural properties.The main research contents and achievements of this thesis are as follows:Extraction of silicon: The content of Si O2 in the vanadium tailing is up to 84.20%.Therefore,the migration and transformation mechanism of silicon and the extraction effecient of silicon were discussed through alkali fusion and alkali dissolution technology.In the Na OH roasted process,the extraction effecient of Si reached a maximum of 98.87%.In the Na2CO3 roasted process,the extraction effecient of Si reached a maximum of 95.75%.In the Na OH dissolution process,the extraction effecient of Si reached the maximum value of 97.67%.Synthesis of MCM-41: MCM-41 was synthesized by hydrothermal method with silicon leaching liquid as the precursor and CTAB as the template agent.The regulation effect of cationic surfactant concentration on mesoporous silica was illustrated: when the molar ratio of CTAB/Si was 0.16,the synthesized mesoporous material had the feature of long range order,excellent structure performance.To be specific,CTAB/Si-0.16 had the largest specific surface area of 1049 m2·g-1,total pore volume of 1.10 cm3·g-1,and the average pore size of 3.04 nm.Synthesis of SBA-15: Introducing three block copolymer P123 as template agent,and using HCl,H2SO4 and H3PO4 as acid precipitation agent,SBA-15 ordered mesoporous materials were synthesized by sol-gel method.The influences of the types and concentrations of acid precipitation agent on the pore structure and microstructure were clarified: SBA-15 had large specific surface area and total pore volume,and uniform pore size distribution.In addition,with the increase of acid concentration,folds on the surface of monomer particles decreased and the length gradually shortened.Hexahedral section can be observed under the electron microscope.Synthesis of SBA-16: SBA-16 ordered mesoporous materials were synthesized by similar method of using the triblock copolymer F127 as template: SBA-16 had the large specific surface area and total pore volume,especially large wall thickness.Additionally,regular dodecahedron morphology of single crystal particle can be seen under the electron microscope.