Preparation And Adsorption Performance Of Modified Molecular Sieves

In the dissertation, modified MCM-41 and SBA-15 were prepared by three-steps surface modification, including aminopropyl group modification, phosphonate group modification and ion chelation. The prepared adsorbents were characterized by FTIR spectra, thermogravimetric analysis, and nitrogen adsorption. Various influence factors of the phosphate adsorption efficiency were studied. Besides, the influence factors of DNA recovery were also studied. The conclusions are listed as below:The prepared adsorbent are marked as Al3+-MCM-41, La3+-MCM-41, Zn2+-MCM-41, Ce3+-MCM-41, Al3+-SBA-15, La3+-SBA-15, Zn2+-SBA-15, Ce3+-SBA-15. FTIR spectra and thermogravimetric analysis suggest that the surface of MCM-41 and SBA-15 have been modified successfully. It is shown that surface areas, pore volumes and aperture were decreased as compared to the unmodified MCM-41 and SBA-15, but retain much natural feature of molecular sieve.The research on the static experiments of adsorption shows that MCM-41 and SBA-15 have better ability to bind phosphate after chemical modifications. The order of interaction forces between phosphate and metal ions is in the following: Al3+>La3+>Zn2+>Ce3+. The recovery efficiency of phosphate are all above 90% with the use of A13+-MCM-41 and A13+-SBA-15, and the adsorption isotherms accorded with Langmuir and Freundlich equation. The adsorption equilibrium time of all sorbents were about 30 minutes, the best initial pH was around 6, the adsorption efficiency of phosphate is decreased with the adsorption temperature decreasing. The research also found that the adsorbed phosphate could be eluted with 0.5 mol/L NaOH solution. The adsorption efficiency of the regenerated adsorbent decreased with different degrees for all adsorbents.The modified molecular sieves have better adsorption properties than those of the former one. The order of interaction forces between DNA and metal ions is in the following:Al3+>La3+>Zn2+>Ce3+. The maximum absorption capacity of A13+-MCM-41 and A13+-SBA-15 are 44.70 mg/g and 41.14 mg/g and the DNA adsorption efficiency are all above 90%. The adsorption isotherms are well represented by Langmuir isotherm model and the results show that the absorption obeys monolayer adsorption. Elution experiment shows that the optimum concentration of NaCl solution is 3-4 mol/L and the pH value is 6.