Stability of colloidal silica. IV. The silica-alumina system

Coprecipitation of silica with aluminum hydroxide

“…The effect of changing the concentration of the preformed silica was not considered in previous work (8) which reports the stability domains in the presence of aluminum nitrate but it was examined in some detail in connection with microflotation experiments (9). A very good correlation was shown between the conditions for effective flotation of silica in the presence of alumina and the boundaries of region III, where the systems consist of unstable, low charged precipitates.…”

“…For low silicate concentrations (less than 10 -a M) the solubility limits (bounding regions A and B) are not influenced by the presence of the silicate species but the colloidal stability domains (regions III, IV, and VI) change when the silicate concentration becomes greater than 5 × 10-~ M. An additional domain for sodium silicate equal to 1.6 x 10-a M is shown in fig. 6 (left) and this is compared with the stability domain reported earlier (8) where the preformed silica, a Ludox AM sol, was used. Good agreement exists between the positions of the boundaries separating regions III, IV, and VI.…”

“…Nephelometric data (4), base exchange capacity (3), electroldnetic phenomena (6), and precipitate compositions (3) are reported for a rather limited range of conditions. The interactions of aluminum salt solutions with preformed silica sols (7,8,9), of silicic acids with alumina sols (10), and of mixed sol systems (11)(12)(13)(14)(15) have also been studied. Crystalline alumino-silicates, such as clays (16) and synthetic molecular sieve zeolites (17), can be prepared from concentrated aqueous systems A12Oa-SiO2-Na20, especially at elevated temperatures or under hydrothermal conditions.…”

In Situ Surface Modification of Silicon Carbide Particles Using Al3+ Complexes and Polyelectrolytes in Aqueous Suspensions

“…The formation of solid Al(OH) 3 or polymeric Al(OH) 3 sol 26 is largely dependent on the experimental conditions. Vermeulen et al 27 and Matijević et al 28 concentration of Al 3ϩ complexes with high charging level starts to increase significantly when the pH approaches the theoretical precipitation point. After reaching this point, the hydroxide sol or polymeric Al(OH) 3 starts to form in the solution, and the concentration continues to increase with further increases of pH.…”

Treatment of Apatite Nepheline Ore Wasteenrichment Waste

“…According to findings, optimum conditions for nepheline decomposition are as follows: H 2 SO 4 concentration -100 g/l at the rate of 85% of stoichiometric rate (Table 1). Berkowitz et al, 2005;Otterstedt et al, 1987;Matijevis et al, 1971). The level of nepheline decomposition was determined from the leaching level of the most acid-resistant aluminium and silica oxides.…”