Homogeneous nucleation of Al(OH)3 crystals from supersaturated sodium aluminate solution investigated by in situ conductivity

Abstract

The homogeneous nucleation process of Al(OH)3 crystals from supersaturated sodium aluminate solution was investigated by a homemade online conductance testing system. Combined with the turbidity and equivalent circuit of conductometry, the conductance curve was divided into five regions, where the charge and discharge region, adsorption region and ionic polymerization region were identified as induction period in the decomposition process of sodium aluminate solution. According to the homogenous nucleation theory, the nucleation kinetics during the decomposition process was studied with the intermediate concentration solution at 333K. The results showed that the solid–liquid interfacial energy was 26.1mJ·m−2, critical nucleation radius was 2.6–3.8nm and the apparent reaction order was 2.9. Meanwhile, UV–vis spectra of sodium aluminate solution in homogeneous process were investigated with decomposition time, where three peaks were observed at 220, 260, and 370nm, respectively. Combined with the conductance curve, the ionic structure change and nucleation mechanism have been discussed.