Organic Additives In The Decomposition Of Sodium Aluminate Solution

Effects of temperature on secondary nucleation and agglomeraton were studied during precipitation process of sodium aluminate solution. Effects of surfactants on particle size and productivity of aluminium hydroxide were also studied in these processes. The suitable temperature which plays main role on secondary nucleation and agglomeraton was determined. Effects of surfactants on seed precipitation and carbon dioxide decomposition of sodium aluminate were investigated.Several processes such as secondary nucleation , agglomeration, growth, rupture and attrition occur in seed precipitation process of sodium aluminate solution, Secondary nucleation or agglomeraton preferably takes place depending on precipitation condition. Results showed that secondary nucleation was main process when 100g. L-1 coarse seeds was added and the solution temperature was 60 C , whereas agglomeraton was main process when lOOg. L-1 smaller seeds was added and the solution temperature was 80C. The initial solution caustic ratio a* was 1. 375 and conceration of Al2O3 140g. L-1.Results showed that adding proper surfactants intensified agglomeraton of small particles, effective collision was increased among aluminium hydroxide particles, agglomeraton and anti-rupture ability was promoted, ability of small particles agglomeraton was intensified. The surfactants mixture was much more effective than cationic or nonionic surfactants for small particles agglomeraton. During seed precipitation, when the amount of mixture-3 was 0. 2g. L-1, the volume percent of particle with diameter larger than 45 m was increased 9% and precipitation rate was increased by 3. 5% in pure solution, and when the amount of mixture-2 was 0. 2g. L-1, the volume percent of particle with diameter larger than 45 u m was increased 7% in industry solution. During carbon dioxide decomposition, by adding 0. 1g. L-1 mixture-3 the volume percent of particle with diameter larger than 45 m increased 20%, and when the amount of mixture-1 was 0.1 g. L-1 the volume percent of particle with diameter larger than 45 u m increased 8% in industry solution.By using surfactant , large particle of aluminium hydroxide was obtained. However, they had low strength and their attrition index was high, so they do not meet the specification of sandy aluminium hydroxide, Further studies are needed.