过饱和铝酸钠溶液均相成核机理研究

Investigation of the Self-nucleation of Gibbsite Al(OH)_3 Crystals from Homogeneous Supersaturated Caustic Solutions

首次采用自行研制的电导率在线跟踪仪,实时检测均相铝酸钠溶液自发成核过程中溶液电导率的变化规律,自动、准确地确定了成核反应诱导期。测得323 K下,饱和度S>3.8的均相铝酸钠溶液自发成核过程的固-液界面能γ=48±3 mJ/m2,临界成核粒径rc=1.1±0.2 nm,表观反应级数n=4±1。

Precipitation of supersaturated caustic solution in the industrial Bayer process is usually seeded.The study of unseeded liquors is necessary for the determination of the critical stable nucleus size,interfacial tension,the order of nucleation and so on.Homogeneous nucleation of Al（OH）3 crystals from synthetic,optically clear caustic aluminate solutions has been investigated under isothermal,batch crystallization conditions with the application of a novel conductivity analyzer and conductometric detection cell. The nucleation kinetics showed a forth-order dependence upon Al（III） relative supersaturation, and interracial energy of 48±3 mJ/m^2 , the critical nucleus size of 1.1±0.2 nm, which agreed well with literature.