ABSTRACT
Synthesis of mesoporous silica microspheres larger than 10 microm via surfactant template approach has rarely been reported. According to the previous studies, particle morphologies were highly variable, depending on the synthesis conditions and impeller design such as impeller type, size, and agitation speed. A new robust surfactant-template synthesis strategy for the stable suspension of large silica microspheres was investigated by introducing an additional cosurfactant. Di(2-ethylhexyl)phosphoric acid (HDEHP) as a cosurfactant played a key role in suspension stabilization without distorting the spherical morphology as well as in the formation of uniform pore structures. High quality of mesoporous silica microspheres was obtained and compared with the Kosuge's silica under different conditions such as stirring rate, acid concentration, the amount of solvent in a mother liquor.
Subject(s)
Colloids/chemistry , Crystallization/methods , Organophosphates/chemistry , Silicon Dioxide/chemistry , Surface-Active Agents/chemistry , Macromolecular Substances/chemistry , Materials Testing , Microspheres , Molecular Conformation , Particle Size , Porosity , Surface PropertiesABSTRACT
Large sample sizes of uranyl ions are eluted on a strenedivinylbenzene copolymer phase and an octadecyl phase column, respectively, using alpha-hydroxyisobutyric acid (alpha-HiBA) as an eluent. Chromatograms are obtained from variations of the uranyl sample amounts, eluent concentrations, concentrations of the sample matrix, and the pH of the sample solution for both columns, respectively. Column capacities are estimated from the loading factors measured from the retention times of the peaks. Bandwidths of the peaks and apparent column efficiencies are measured as a function of the loading factor and calculated using the equations derived from the assumptions of a Langmuir isotherm for a single solute. Comparison between the experiment and the calculation reveals that the former showed a broader bandwidth and worse column efficiency than the latter for both columns. The two columns are compared with regards to the retention time, peak shape, column capacity, column efficiency, etc. The PRP-1 column shows a rectangular-, triangle-type peak shape, longer retention time, lower column capacity, and better column efficiency, and the LC-18 column shows a distorted Gaussian curve, shorter retention time, higher column capacity, and worse column efficiency. Column capacity, peak shape, and retention time are dependent on the eluent concentration rather than the alpha-HiBA concentration in the sample solutions.
