活性晶种的性质及其强化铝酸钠溶液晶种分解的机理分析

Properties and intensification mechanism of active seed for seeded precipitation of sodium aluminate solution

活性晶种可以强化铝酸钠溶液晶种分解并显著提高种分分解率。通过碳酸氢钠诱导铝酸钠溶液快速分解制备活性晶种,研究其性质及对种分过程的影响规律,探讨活性晶种强化种分过程的机理。结果表明:碳酸氢钠诱导铝酸钠溶液快速分解制备的活性晶种主要是拜耳石型氢氧化铝,其粒度细、比表面积大、表面能高且表面溶剂化趋势较强,具有很强的促进铝酸钠溶液分解的能力,在晶种添加量仅为1g/L的条件下,铝酸钠溶液种分分解率可达65%以上。晶种强化铝酸钠溶液种分的能力除了随晶种表面积的增大而增强外,还随晶种表面溶剂化趋势的增强和晶种表面Zeta电位的升高而增强。在晶种分解初期,活性晶种诱导铝酸钠溶液中其他铝酸根阴离子向Al(OH)4^-转变,其诱导溶液结构变化的能力随晶种表面积的增大和晶种表面溶剂化趋势的增强而增强。活性晶种特殊的表面性质和晶种诱导铝酸根离子向有利于种分的铝酸根离子形态转变的能力共同决定活性晶种强化铝酸钠溶液种分过程的活性。

Seeded precipitation of sodium aluminate solution can be intensified by adding active seed and the precipitation rate can be increased remarkably.The properties of the active seed prepared by reaction of sodium bicarbonate and sodium aluminate solution were characterized and the influences of the properties on seeded precipitation process were investigated.The results show that the active seed is composed of bayerite with fine particle size,large specific surface area,high surface energy and stronger solvent effect.The precipitation of sodium aluminate solution can be enhanced considerably by adding active seed,and the seeded precipitation rate can reach 65% with only 1g/L of the active seed.Besides the larger surface area,the stronger solvent effect and more positive Zeta potential of the active seed are attributed to promoting the seeded precipitation.The active seed has a higher capability to induce the aluminate ion in sodium aluminate solution converting into Al(OH)4 at the initial period of seeded precipitation,and the capability increases with the seed surface area and solvent effect.The special surface properties and the high capability of inducing aluminate ion conversion may be the cause of the high activity of the active seed on promoting the seeded precipitation of sodium aluminate solution.