Modeling and electrokinetic evidences on the processes of the Al(III) sorption continuum in SiO2(s) suspension

Association of dissolved aluminum with silica: Connecting molecular structure to surface reactivity using NMR

“…According to the data from Carroll et al (2002), the silanol surface coverage is at least $20% for even our highest pH of 8.2, well above the number of sites required for sorption. Our interpretation is supported by recent studies using spectroscopy that show inner-sphere adsorption of metals ions utilize $10% of the surface sites, prior to the onset of precipitating hydroxide-containing phases (Katz and Hayes, 1995;Kuan et al, 2004).…”

“…Surface nucleation of Al(OH) 3 may be facilitated by the large number of surface hydroxyls available for reaction. Kuan et al (2004) found using surface complexation/surface precipitation modeling, in addition to electrokinetic experiments, that reaction of 1 mM Al with silica produced surface precipitation of Al(OH) 3 above pH 4. Our experimental conditions are very similar to those reported by Kuan et al (2004).…”

“…Kuan et al (2004) found using surface complexation/surface precipitation modeling, in addition to electrokinetic experiments, that reaction of 1 mM Al with silica produced surface precipitation of Al(OH) 3 above pH 4. Our experimental conditions are very similar to those reported by Kuan et al (2004). We too suspect that surface-precipitation of Al(OH) 3 occurs at the silica gel-water interface, particularly since the solution chemistry conditions are above gibbsite saturation.…”

An extended X-ray absorption spectroscopy study of copper(II) sorption by oxides

“…The experiments were conducted using three commercial products, which are the most important components in soil, namely Al(OH) 3 (gibbsite, Merck KGaA, Darmstadt; i.e., surface area of 1.5 g m À2 , b1.7 Am in size), MnO 2 (pyrolusite, Aldrich Chemical Company; i.e., surface area of 2.0 g m À2 , b40 Am in size), and SiO 2 (amorphous silica, Cabot, Tuscolca, IL, i.e., surface area of 204 g m À2 , 15-25 nm in diameter) (Kuan et al, 2004) equilibrated with Cu(II) (CuCl 2 solution). Batch experiments were conducted by mixing 2 or 5 g of gibbsite, pyrolusite, and amorphous silica separately with 1 L of 0.5 mM of CuCl 2 solution in 1 L volumetric flasks.…”

The role of pH, metal ions and their hydroxides in charge reversal of protein-coated nanoparticles

“…7 As the surface charge of these hydroxides depends on the pH as well, the pH seems to be the one key parameter that enframes all interactions. 8 In literature, charge inversion is either attributed to the adsorption of unhydrolyzed ions, [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] hydrolyzed ions [25][26][27][28][29][30][31][32][33] or hydroxides. [34][35][36] Which of these species is eventually responsible, remains unclear because the commonly used electrophoretic measurements (e.g.…”