Yield stress and zeta potential of nanoparticulate silica dispersions under the influence of adsorbed hydrolysis products of metal ions - Cu(II), A1(III) and Th(IV)
Leong, Yee-Kwong (2005) Yield stress and zeta potential of nanoparticulate silica dispersions under the influence of adsorbed hydrolysis products of metal ions - Cu(II), A1(III) and Th(IV). Journal of Colloid and Interface Science, 292 (2). pp. 558-566.
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The effects of hydrolysable Cu2+, Al3+ and Th4+ ions on the zeta potential and yield stress behaviour of silica dispersions were evaluated as a function of pH and metal ions concentration. Silica dispersion remained dispersed at its point of zero charge (pzc) of pH ~2.0(CR1). Adsorbed hydrolysis products of Cu2+ and Al3+ caused the dispersion to display two further points of charge reversal (CR2 and CR3) at moderate ions concentration. CR2 occurred near the pH for the formation of the first hydrolysis product. This pH is about 2.8 for Al3+ and 5.0 for Cu2+. For all three metal ions, CR3 approached the pzc of the metal hydroxides at complete surface coverage. At CR3, the dispersions displayed a maximum yield stress. As many as three type of attractive forces; bridging, charged patch and van der Waals, may account for the maximum yield stress at low surface coverage. At complete coverage, only the van der Waals force is in play—the adsorbed hydrolysis products must have increased significantly the effective Hamaker constant of silica. With Al3+ the yield stress was absent at CR2 because particle bridging and charged patch attraction are unimportant as the silica surface charge is near zero. Adsorption of strongly hydrolysed Th4+ ions at pH < 2.0 caused the dispersion to display only one pzc (CR3).
|Item Type:||Article (Refereed Research - C1)|
|Keywords:||bridging; charged patch attraction; metal ions hydrolysis products; silica; yield stress; zeta potential|
|Date Deposited:||30 Mar 2010 01:16|
|FoR Codes:||09 ENGINEERING > 0904 Chemical Engineering > 090499 Chemical Engineering not elsewhere classified @ 60%
03 CHEMICAL SCIENCES > 0306 Physical Chemistry (incl Structural) > 030603 Colloid and Surface Chemistry @ 40%
|SEO Codes:||86 MANUFACTURING > 8606 Industrial Chemicals and Related Products > 860699 Industrial Chemicals and Related Products not elsewhere classified @ 51%
86 MANUFACTURING > 8615 Instrumentation > 861503 Scientific Instruments @ 49%
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