Computer Science
Scientific paper
Jun 1979
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1979gecoa..43..861m&link_type=abstract
Geochimica et Cosmochimica Acta, vol. 43, Issue 6, pp.861-868
Computer Science
9
Scientific paper
Solubility curves were determined for a synthetic gibbsite and a natural gibbsite (Minas Gerais, Brazil) from pH 4 to 9, in 0.2% gibbsite suspensions in 0.01 M NaNO 3 that were buffered by low concentrations of non-complexing buffer agents. Equilibrium solubility was approached from oversaturation (in suspensions spiked with Al(NO 3 ) 3 solution), and also from undersaturation in some synthetic gibbsite suspensions. Mononuclear Al ion concentrations and pH values were periodically determined. Within 1 month or less, data from over-and undersaturated suspensions of synthetic gibbsite converged to describe an equilibrium solubility curve. A downward shift of the solubility curve, beginning at pH 6.7, indicates that a phase more stable than gibbsite controls Al solubility in alkaline systems. Extrapolation of the initial portion of the high-pH side of the synthetic gibbsite solubility curve provides the first unified equilibrium experimental model of Al ion speciation in waters from pH 4 to 9. The significant mononuclear ion species at equilibrium with gibbsite are Al 3+ , AlOH 2+ , Al(OH) + 2 and Al(OH) - 4 , and their ion activity products are * K 50 = 1.29 × 10 8 , * K s 1 = 1.33 × 10 3 , * K s 2 = 9.49 × 10 -3 and * K s 4 = 8.94 × 10 -15 . The calculated standard Gibbs free energies of formation ( G ° f ) for the synthetic gibbsite and the A1OH 2+ , Al(OH) + 2 and Al(OH) - 4 ions are -276.0, -166.9, -216.5 and -313.5 kcal mol -1 , respectively. These G ° f values are based on the recently revised G ° f value for Al 3+ (-117.0 ± 0.3 kcal mol -1 ) and carry the same uncertainty. The G ° f of the natural gibbsite is -275.1 ± 0.4 kcal mol - , which suggests that a range of G ° f values can exist even for relatively simple natural minerals.
Helmke Philip A.
Jackson Marion L.
May Howard M.
No associations
LandOfFree
Gibbsite solubility and thermodynamic properties of hydroxy-aluminum ions in aqueous solution at 25°C does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Gibbsite solubility and thermodynamic properties of hydroxy-aluminum ions in aqueous solution at 25°C, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Gibbsite solubility and thermodynamic properties of hydroxy-aluminum ions in aqueous solution at 25°C will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1777085