Dissolved silica-catalyzed disordered dolomite precipitation

This research investigated the effectiveness of electrocoagulation using iron and aluminium electrodes for treating cooling tower blowdown (CTB) waters containing dissolved silica (Si(OH)4), Ca2 + and Mg2 + . The removal of each target species was measured as a function of the coagulant dose in simulated CTB waters with initial pH values of 5, 7, and 9. Experiments were also performed to investigate the effect of antiscaling compounds and coagulation aids on hardness ion removal. Both iron and aluminum electrodes were effective at removing dissolved silica. For coagulant doses ≤3 mM, silica removal was a linear function of the coagulant dose, with 0.4 to 0.5 moles of silica removed per mole of iron or aluminium. Iron electrodes were only 30% as effective at removing Ca2 + and Mg2 + as compared to silica. There was no measurable removal of hardness ions by aluminium electrodes in the absence of organic additives. Phosphonate based antiscaling compounds were uniformly effective at increasing the removal of Ca2 + and Mg2 + by both iron and aluminium electrodes. Cationic and amphoteric polymers used as coagulation aids were also effective at increasing hardness ion removal.

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Removal of Dissolved Silica from Alkali Carbonate Brines

Industrial & Engineering Chemistry ◽

10.1021/ie50413a014 ◽

1944 ◽

Vol 36 (5) ◽

pp. 420-422

Author(s):

E. Gerald Meyer ◽

Charles E. McCarthy

Keyword(s):

Dissolved Silica ◽

Alkali Carbonate

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Influences of Dolomite Precipitation on Quartz Surface Textures

Journal of Sedimentary Research ◽

10.1306/212f9291-2b24-11d7-8648000102c1865d ◽

1990 ◽

Vol Vol. 60 ◽

Author(s):

Robert G. Maliva (2), Raymond Sieve

Keyword(s):

Quartz Surface ◽

Surface Textures ◽

Dolomite Precipitation

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Alteration of Natural Uranyl Oxide Hydrates in Si-Rich Groundwaters: Implications For Uranium Solubility

MRS Proceedings ◽

10.1557/proc-257-465 ◽

1991 ◽

Vol 257 ◽

Cited By ~ 6

Author(s):

R.J. Finch ◽

R.C. Ewing

Keyword(s):

Corrosion Products ◽

Dissolved Silica ◽

Uranyl Phosphates ◽

Uranyl Silicates ◽

Solid Phases ◽

And Control

ABSTRACTThe uranyl oxide hydrates are common initial corrosion products of uraninite (nominally U02+x) during weathering. In the presence of dissolved silica these early-formed phases alter to uranyl silicates (most commonly soddyite, U2SiO8-2H2O, and uranophane, CaU2Si2O11·6H2O). Uraninite, however, usually contains radiogenic Pb, and the earlyformed Pb-poor uranyl oxide hydrates alter incongruously to uranyl silicates plus Pb-enriched uranyl oxide hydrates such as curite. Similar to dissolved silica, radiogenic Pb may also serve to limit the mobility of U in nature by fixing U in solid phases. Curite may also play an important role in the formation of uranyl phosphates, which are significantly less soluble than the uranyl silicates, and control U solubility in many groundwaters associated with altered U ore.

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