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Preparation, Characterization, And Adsorption Properties Of SiO2 And Magnetic Particles Modified With Organosilanes

Posted on:2008-06-24Degree:MasterType:Thesis
Country:ChinaCandidate:H XiangFull Text:PDF
GTID:2178360215984822Subject:Materials science
Abstract/Summary:PDF Full Text Request
The purpose of this dissertation is to find suitable methods to prepare modified silica particles with good spherical shape and narrow particle size distribution, and to prepare modified magnetic particles with good adsorption properties. After the preparation of these particles, characterize and study the surface properties of these particles comprehensively, and investigate the adsorption behaviors of these particles and the adsorption mechanisms.In order to find a convenient and economical method to prepare modified spherical silica particles, and to study the surface properties and adsorption properties of these particles, silica submicrometer spheres surface modified with -CH3, -CH=CH2, -(CH2)2CH3, -(CH2)3NH2, -C6H5, -(CH2)7CH3, -(CH2)11CH3, and -CH2(CH2)4CH2- groups were prepared through a one-step process. SEM, dynamic light scattering (DLS), FTIR, DSC, TG, UV-visible spectra, zeta potential, N2 adsorption/desorption, water vapor adsorption, dye adsorption, and convective assembly methods were used to characterize and compare the surface properties of the modified particles comprehensively. SEM images of the particles demonstrate that the modified particles are uniformly spherical, monodisperse, and well shaped with particle sizes ranging from 130 to 150 nm depending on the surface modified organic groups. The particles modified with -(CH2)3NH2 groups (APTES particles) have the largest size, the highest IEP, and the highest weight loss at 780oC. The particles modified with -(CH2)11CH3 groups (DTES particles) have the lowest water vapor adsorption. While pure silica particles have the highest water vapor adsorption, APTES particles the second highest water vapor adsorption because of the presence of amine groups, which can form hydrogen bonds with water. In water suspension the particles modified with phenyl groups -C6H5 (PhTES particles) have an obvious UV absorption peak at around 210 nm. While the other modified particles and pure silica particles do not have any UV-visible absorption peaks. The organic dye (brilliant blue FCF, BBF) adsorption experiments demonstrate that after acidification of the particles the adsorption capacity of the particles increases greatly, with APTES particles having the highest adsorption, pure silica particles the lowest adsorption, and PhTES particles the second highest adsorption. Convective assembling experiments using particle water suspension in the open air at room temperature show that under the same experimental conditions the particles modified with -CH3, -CH=CH2, -(CH2)2CH3, -(CH2)7CH3, -(CH2)11CH3, and -CH2(CH2)4CH2- groups give better assembly, APTES particles the worst, and pure silica particles the second worst assembly.In order to prepare modified magnetic particles with good adsorption properties, and to study the adsorption and desorption behaviors, and the adsorption mechanisms, organosilane-functionalized Fe3O4 particles are prepared by reacting organosilane precursor, bis[(3-trimethoxysilyl)propyl]-ethylenediamine (TSPED) on Fe3O4 magnetic particles. To examine the adsorption and desorption properties of the modified particles, brilliant blue FCF (BBF) is used as a model adsorbate. The effects of solution pH, ionic strength, temperature and initial BBF concentration on adsorption are investigated. The experimental results show that most of the dye is adsorbed and desorbed within 15 min. The equilibrium adsorption amount increases with the increase in initial BBF concentration, but decreases with the increase in ionic strength. The adsorption amount exhibits a maximum at the pH 6.5, and temperature does not have a significant effect on the adsorption below 50oC. NaOH solution appears to be a more efficient desorption medium than NaCl solution. Hydrogen bonding, electrostatic and hydrophobic attractions are found to be the driving forces for the adsorption of BBF.
Keywords/Search Tags:modified spherical silica particle, modified magnetic particle, organosilane, surface property, dye adsorption, adsorption mechanism
PDF Full Text Request
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