晶种对铝酸钠溶液耦合分解行为的影响

Effects of seed on coupling-precipitation behavior from sodium aluminate solution

采用铝酸钠溶液耦合分解的方法制备一水软铝石,即在碳酸化分解的条件下加入一水软铝石晶种进行铝酸根聚合结晶过程诱导,研究晶种对耦合分解率和产物中一水软铝石含量的影响。结果表明:耦合分解产物为三水铝石与一水软铝石的混合物,改变晶种属性能够调控耦合分解率和产物组成,晶种的主要作用是促进一水软铝石的诱导结晶。随着晶种系数(S)在0.1～0.8范围内的增加,分解率随之降低;当晶种系数S由0.1增加到0.4时,一水软铝石在产物中的质量分数急剧增加至76%左右;当S>0.4后,一水软铝石的质量分数不再发生明显变化,且随着晶种粒度的减小,分解率有所提高,6.5h后,分解率均达到90%左右,但产物中一水软铝石含量却随之降低。经过机械活化后的晶种,活性增强,使分解率和一水软铝石含量均有所提高。

The boehmite was prepared from sodium aluminate solution by coupling-precipitation,the carbonization and seed precipitation were adopted to induce the reaction and crystallization of aluminate ions.The effects of seed on precipitation rate and mass fraction of boehmite were investigated.The results indicate that the products are constituted by boehmite and gibbsite.The seeds can influence the precipitation rate and composition of alumina hydrates,especially have obvious effects on the induced crystallization of boehmite.With increasing the seed coefficient S in the range of 0.1-0.8,the precipitation rate decreases.However,the mass fraction of boehmite increases dramatically with seed coefficient changing from 0.1 to 0.4,and gets the maximum value of 76%.When the seed coefficient is more than 0.4,it has no obvious change.As the seed diameters decreases the precipitation rate increases while the mass fraction of boehmite decreases.After 6.5 h,the precipitation rate reaches 90% approximately.The activity of seed is enhanced by mechanical activation,which results in the increases of precipitation rate and the mass fraction of boehmite.