Elucidation of the Structures of Aluminate Ions during the Dissolution of Gibbsite in Choline and Verification of hydrated ion model

Abstract The equilibrium solubility of gibbsite in choline was measured and thee quilibrium constant was obtained. Gibbsite was more likely to dissolve in choline compared with NaOH and the dissolution enthalpy was 17.845 kJ/mol. Ion solvation model which can express the equilibrium solubility within the entire alkali concentration range was established and verified by measuring conductivity, solubility parameters. The hydration ion number was obtained 4.83 at 70℃ which was reasonable. The ionic composition of the aluminate solution was studied in choline. With the increase of alkali concentration, Al(OH)5- and double oxygen bridged dimer Al2O8H64- appear and coexist with tetracoordinated Al(OH)4-.