Diol Additives On The Process Of Sodium Aluminate Solution

It has been proved that the organic additives can change the process of precipitation, improve the precipitation ratio and increase the particle size during the seed precipitation of sodium aluminate solution. However, it's difficult to design effective additives because the interaction between additives and aluminium hydroxide has not revealed theoretically. Researches about the effect of non-ionic surfactant-1, 2-Octanediol and 1, 8-Octanediol on the seed precipitation of sodium aluminate solution were performed in the paper. By analyzing the changes of precipitation ratio, particle size, SEM and XRD measurements, the effect of dihydric alcohols on the seed precipitation of sodium aluminate solution were inverstigated on different conditions of experimental temperature, caustic concentration of liquor, the concentration of additives and seeds.It was found that 1, 2-Octanediol has inhibitory effect on the precipitation by physical adsorption on the active sites of seed surface. When the concentration of 1, 2-Octanediol in the solution is less than 1.25mmol/L, the inhibitory effect on gibbsite precipitation is limited and the particle size is about the same as that without additive. However, when the concentration of 1, 2-Octanediol in the solution is more than 1.5mmol/L, the inhibitory effect is large and the particle size is decreased. Lower temperature and higher caustic concentration of liquor will greatly increase the inhibitory effect and decrease the particle size. Secondary nucleation happens and is intensified on the condition of lower temperature and higher caustic concentration of liquor which is in favor of increasing the agglomeration period. The agglomeration and growth of gibbsite in sodium aluminate solution are alternated with the added of 1, 2-Octanediol.1, 8-Octanediol can enhance the precipitation and enlarge the particle size. It can increase the agglomeration period on the condition of lower temperature and higher caustic concentration of liquor.The dihydric alcohol with two adjacent hydroxyl groups has inhibitory effect on the precipitation by physical adsorption on the active sites of seed surface. The dihydric alcohol with two terminal hydroxyl groups can enhance the precipitation by one of the hydroxyl groups stayed in the sodium aluminate solution.