Combined effect of amino and carboxyl group in α-alanine on
seeded precipitation of sodium aluminate solution
seeded precipitation of sodium aluminate solution
(School of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China)
Abstract: α-alanine was adopted as a new additive to elucidate the seeded precipitation mechanism of sodium aluminate solution. α-alanine has the inhibitory effect at the initial period of reaction, but the favorable effect in subsequent reaction. The combined effect of amino and carboxyl group in α-alanine was confirmed by investigating the effect of propionic acid, ethamine and the mixture of propionic acid and ethamine (mole ratio 1׃1) on the precipitation of sodium aluminate solution, respectively. The inhibitory effect derives from the adsorption of amino or carboxyl group in α-alanine on the active surface sites of gibbsite, which was confirmed by the alleviating inhibitory effects of propionic acid, ethamine and α-alanine due to the double crystal seed mass. The semi-quantitative IR spectrum analysis of the relative concentrations of Al2O(OH)62− with the band at about 550 cm−1 and polynuclear aluminate ion with the bands at about 880 cm−1 and 635 cm−1, indicates that the dynamic balance among some aluminate species present in sodium aluminate solution is broken due to the addition of α-alanine, thus resulting in the change of the seeded precipitation ratio of sodium aluminate solution.
Key words: α-alanine; sodium aluminate solution; seeded precipitation