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- Otterstedt, J-E, et al.
(författare)
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Colloidal components in solutions of alkali silicates
- 1987
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 115:1, s. 95-103
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Tidskriftsartikel (refereegranskat)abstract
- The particle size of colloidal silica in 1 to 5 M SiO2 solutions of lithium, sodium, potassium, and cesium silicates in the ratio range 1.5-20 moles of SiO2 per mole of M2O was determined by reaction with molybdic acid and by Sears titration. The particle size increased from 1.0 to 4.5 nm with increasing ratio but did not depend on the type of alkali-metal cation. The amount of monomeric silicate ions decreased sharply with increasing ratio from 35% for ratio 2 to 2% for ratio 15 in 5 M SiO2 solutions. The polymeric particles were extracted into tetrahydrofuran or tertiary butylalcohol at pH 2, without changing the particle size, in yields which increased to more than 95% for the highest ratios. Previous dilution caused the particle size to grow in high-ratio solutions but to decrease in low-ratio solutions.
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| 2. |
- Sterte, Johan, et al.
(författare)
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Cross-linked smectites : V. Synthesis and properties of hydroxy- silicoaluminum montmorillonites and fluorhectorites
- 1987
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Ingår i: Clays and clay minerals. - 0009-8604 .- 1552-8367. ; 35:6, s. 429-439
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Tidskriftsartikel (refereegranskat)abstract
- Solutions containing hydroxy-SiAl (HSA) oligocations were prepared by two procedures: 1) treatment of a mixture of orthosilicic acid and AlCl3 with aqueous NaOH, followed by ageing of the product; and 2) preparation and ageing of hydroxy-Al13 oligocations followed by reaction of the latter with orthosilicic acid. Ion exchange of Na,Ca-montmorillonite with HSA oligocations yielded pillared, cross-linked montmorillonites (designated as HSA-CLM) showing a maximum d(001) value of 19.5 A for air-dried samples, and maximum surface areas of approx 500 m2/g after outgassing at 250oC/10-3 torr. Corresponding ion exchange of Li-fluorhectorite yielded HSA fluorhectorites (HSA- CLFH) showing a maximum d(001) value of 19.0 A and a surface area of 355 m2/g. Calculated structural formulae for the HSA-CLM and HSA-CLFH products, based on elemental analysis, showed a gradual increase in the Si/Al ratio in the intercalated HSA oligocations with increasing Si/Al ratio in the pillaring solution. Optimum d(001) values and surface areas of HSA-CLM and HSA-CLFH products were obtained using method 2 and applying a ratio of 1.6-2.5 mmole (Si)Al/g smectite. HSA-CLFH products showed the unusual behaviour of increase of d(001) with increase in T from 400o to 500oC, and essential constancy of d(001) from 500o to 600oC. The HSA-CLM products showed a gradual decrease in surface area, whereas the HSA-CLFH products prepared with a Si/Al ratio of 1.04-2.18 in the pillaring solution showed constant surface areas with increasing T from 250o to 600oC.
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