Effect of aging on aluminum hydroxide complexes in dilute aqueous solutions

摘要: Aqueous aluminum solutions containing 4 x 10/sup -5/ mole/liter and a constant total ionic strength of -2/, but with varying ratios hydroxide to (OH:AL), were prepared. Progress these toward equilibrium conditions over aging periods as much 2 years was studied by determining the composition pH at various time intervals. The solutions, after mixing, supersaturated respect both crystalline amorphous forms oxides hydroxides. compositions determined use timed colorimetric analytical procedure which allowed estimation three separate that have been designated Al(a), Al(b), Al(c). Form Al(a) appeared be composed monomeric species such Al(H/sub 2/O)/sup 6 + +/, Al(OH)(H/sub 5 Al(OH)/sub 2/(H/sub +/ Al(OH)/sup -/. Al(b) polynuclear material perhaps 20-400 atoms per structure. It metastable material. Al(c) remained time, decreased, increased. particles increasing in size ultimately converted particles. After few weeks' aging, hadmore » structure gibbsite. In all only very slowly achieved, required depended on OH:AL ratio how rapidly solution initially prepared (mixing time). From data during study considering consist extremely small solid gibbsite particles, it possible estimate gibbs free energy (001) crystal face (gamma (e), face) (110) (100) faces (f), edge) its saturated solution. These values were: gamma (f) = 140 plus or minus 24 ergs/cm2, (e) 483 84 ergs/cm2.« less