Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Silica dissolution

The other restriction of SynChropak size exclusion columns is a general one for silica-based supports, that of pH. The most harmful pH is that above 7.5 due to silica dissolution. The bonded phase of SynChropak GPC has some polymeric properties therefore, it is not removed rapidly from the silica at pH 2-3. The bonded phase of SynChropak CATSEC is polymeric and stable at pH 2-7.5. [Pg.323]

During caustic waterflooding the alkali can be consumed by the dissolution of clays and is lost in this way. The amount lost depends on the kinetics of the particular reaction. Several studies have been performed with kaolinite, using quartz as a yardstick, because the kinetic data are documented in the literature. The initial reaction rate has been found pH independent in the pH range of 11 to 13 [517]. The kinetics of silica dissolution could be quantitatively described in terms of pH, salinity, ion-exchange properties, temperature, and contact time [1549]. [Pg.199]

Ballou, E. V., M. I. Leban and T. Wydeven. 1973. Solute rejection by porous glass membranes. III. Reduced silica dissolution and prolonged hyperfiltration service with feed additive. J. Appl. Chem. Biotechnol. 23 119-30. [Pg.92]

At present, many studies are ongoing to identify a means of enhancing the carbonation chemistry of magnesium silicates in aqueous systems, using weak acids and additives that will improve silica dissolution, such as citrates, oxalates, and EDTA [105, 111]. In this case, a near-complete recovery and reuse, thereby minimizing the losses of such chemicals, will be essential for viable process economics. Likewise, there is much to improve with regards to the reaction rates and/ or times. [Pg.373]

Among the inorganic templates, zeolite produces more regulated pores as compared to the silica template. If nano-channels in zeolite are completely filled with carbonaceous precursor and then the carbon materials are extracted from the zeolite framework, one can obtain the porous carbon of which structure reflects the porosity of the original zeolite template. The ordered mesoporous silica templates, e.g., MCM-4 838,39,47 and SBA-1547 have been employed to prepare the ordered porous carbons by the procedures involving the pore filling of the silica template with carbonaceous precursor followed by carbonization and silica dissolution. The resulting pore sizes of the ordered mesoporous carbons are smaller than about 10 nm. [Pg.143]

Bidle, K., Brzezinski, M.A., Long, R.A., Jones, J.L., and Azam, F. (2003) Diminished efficiency in the oceanic silica pump caused by bacteria-mediated silica dissolution. Limnol. Oceanogr. 48, 1855-1868. [Pg.547]

The structure electrical double layer at the silica-aqueous electrolyte interface was one of the earlier examined of the oxide systems. At the beginning the investigations were performed with application of electrokinetic methods next, with potentiometric titrations. The properties of this system were very important for flotation in mineral processing. Measurements proved that pHpZC and pHiep are equal to 3, but presence of some alkaline or acidic contaminants may change the position of these points on pH scale. Few examples, concerning edl parameters are shown in Table 3. Presented data concern a group of systems of different composition of the liquid phase and solid of a different origin. The latest measurements of this system takes into account the kinetics of the silica dissolution [152], and at zeta measurements, also the porosity of dispersed solid [155]. [Pg.186]

So to develop a separation on a bare silica gel column, the chroma-tographer first would know that the C 8 approach had resulted in excessive retention and or tailing. Next the chromatographer would choose a pH at which the compounds are ionized. Often a pH of 7.8 is used since it is a basic pH within the safe range (i.e., no silica dissolution) and can be... [Pg.166]

To avoid basic silica dissolution that leads to poor reproducibility, reduced efficiencies, poor peak shapes and high back pressure carbon-based stationary phases were also tested. Unlike silica-based reversed phases, they can be exposed to both highly acidic and alkaline environments (pH 1 to 14) and very high temperatures without degradation [15] they proved very useful in the analysis of organic acids [16]. [Pg.126]

The rate of silica dissolution is proportional to its surface area. Silicic acid being passed into solution undergoes polymerization giving water and the molecules of polysilicic acids of variable complexity. At pH... [Pg.53]

Lawson, D., Hurd, D. C. and Pankratz, H. S., Silica dissolution rates of decomposing phytoplankton assemblages at various temperatures. [Pg.445]

Stone and Tiemann (S28) have reported the specific rates of silica extraction from taconite ores as a function of time, temperature, and sodium hydroxide concentration. The microcrystalline varieties of quartz associated with the taconites are easily disintegrated by sodium hydroxide under pressure. The rate of silica dissolution has an activation energy of 15,000-19,000 cal/mole. [Pg.40]

Fujii, M., and Chai, P. (2005). Effects of biogenic silica dissolution on silicon cycling and export production. Geophys. Res. Lett. 32, doi 10.1029/2004GL022054. [Pg.1618]

Van Cappellen P. and Qiu L. (1997a) Biogenic silica dissolution in sediments of the Southern Ocean ... [Pg.3168]

Martin W. R., Bender M., Leinen M., and Orchardo J. (1991) Benthic organic carbon degradation and biogenic silica dissolution in the central equatorial Pacific. Deep-Sea Res. 38, 1481-1516. [Pg.3531]

Greenwood J. E., Truesdale V. W., and Rendell A. R. (2001) Biogenic silica dissolution in seawater in vitro chemical kinetics. Prog. Oceanogr. 48, 1-23. [Pg.3562]

McManus J., Berelson W. M., Hammond D. E., Kilgore T. E., DeMaster D. J., Ragueneau O., and CoUier R. (1995) Early diagenesis of biogenic silica dissolution rates, kinetics, and paleoceanographic implications. Deep-Sea Res. II 42, 871-903. [Pg.3562]

Nelson D. A. and Goering J. J. (1977) Near-surface silica dissolution in the upwelling region off northwest Africa. Deep-Sea Res. 24, 65 -73. [Pg.3562]

Van Cappellen P., Dixit S., and Van Beusekom J. E. E. (2002) Biogenic silica dissolution in the oceans reconciling experimental and field-based dissolution rate. Global Biogeochem. Cycles 16(25), 1-10. [Pg.3563]


See other pages where Silica dissolution is mentioned: [Pg.485]    [Pg.16]    [Pg.67]    [Pg.165]    [Pg.267]    [Pg.154]    [Pg.337]    [Pg.103]    [Pg.677]    [Pg.163]    [Pg.176]    [Pg.5668]    [Pg.127]    [Pg.136]    [Pg.137]    [Pg.380]    [Pg.254]    [Pg.3138]    [Pg.3167]    [Pg.3557]    [Pg.3558]    [Pg.3562]    [Pg.3562]   
See also in sourсe #XX -- [ Pg.175 ]

See also in sourсe #XX -- [ Pg.404 , Pg.409 ]

See also in sourсe #XX -- [ Pg.448 ]

See also in sourсe #XX -- [ Pg.253 ]

See also in sourсe #XX -- [ Pg.379 ]




SEARCH



Dissolution of amorphous silica

Dissolution of silica

Silica Polymorphs, Dissolution, and Precipitation

Silica biogenic, dissolution

Silica dissolution reaction rates

Silica dissolution reactions

Silica gel dissolution

Silica glass, dissolution

Silica release during dissolution from

Silica surface dissolution

© 2024 chempedia.info