Abstract:Influence of supersaturation on the structure of a series of freshly prepared supersaturated sodium aluminate solutions with medium concentration was investigated by solution X-ray diffraction. Experimental results show that the basic Al-containing species in all kinds of supersaturated solution is four-coordinated ions. Opposite to Al—O distance contracted in highly concentrated solution, a little expand of the Al—O distance from 1.75℃ to 1.85℃ occurs with increasing supersaturation, which is consistent with the occurrence of oligomeric aluminate species. Meanwhile, O—O distance in the first shell of H₂O—H₂O(OH) in supersaturated sodium aluminate solution is obviously longer than in hydroxide sodium solution and becomes longer and longer with increasing supersaturation. Na—O bond length is about 2.4℃ and changes little with supersaturation. The reason for Al—O bond expanding with supersaturation and its influence on the stability of solution was discussed. 

Key words:  solution X-ray diffraction; sodium aluminate solution; structural property