过饱和铝酸钠溶液中氢氧化铝自发成核动力学规律的研究

用电导法和吸光光度法首次对苛性比相同的不同浓度过饱和铝酸钠溶液自发分解过程进行了实时跟踪研究,获得铝酸钠溶解氢氧化铝自发成核动力学方程,探索了H₂O和Na⁺对氢氧化铝自发成核过程的影响.结果表明,过饱和铝酸钠溶液分解为氢氧化铝属化学反应控制过程;H₂O参与了溶液分解过程控制步骤的反应;K⁺和Na⁺等阳离子参与了溶液的重构,但对溶液分解的控制步骤影响不大.

Studies on the Kinetics of Unseeded Nucleation of Aluminum Trihydroxide from Supersaturated Sodium Aluminate Solutions

Under isothermal batch crystallization condition, unseeded nucleation of Al(OH)3 crystals from supersaturated caustic aluminate solution was studied by in situ conductivity and absorbance measurements. The nucleation kinetics of Al(OH)3 crystals were obtained and the influence of H2O and Na+ on the unseeded nucleation were investigated. The experimental results indicate that, when the molar ratio of Na2O to Al2O3 is fixed in Na2O-Al2O3-H2O system. The crystallization of Gibbsite display two kinds of nucleation mechanism with variation of H2O content. When Na2O in the crystallization system is substituted by K2O, the induction period of the crystallization is prolonged, but the active energy and the reaction order are all found to be independent of the alkali ion. It can be concluded that, the nucleation of Al(OH)3 crystals in supersaturated alminate solution is a chemical reaction controlled process, H2O and Na+ take part in the reconstruction of alminate ions though they are not present in the overall-reaction of Al(OH)3 crystallization. H2O is related to the key procedure of the decomposition of supersaturated sodium alminate solution. Yet, Na+ has little effects on the controlling-step.