Mg²⁺/NH<inf>4</inf>⁺ ion exchange kinetics under isothermal supersaturated conditions

Ion Exchange Isothermal Supersaturation process (IXISS) allows the recovery of the salt from the elution solution without any additional reagent or step. This work focuses on the batch elution kinetics of magnesium with ammonium from two commercial resins under supersaturated conditions - i.e., conditions far above from the solubility of magnesium. The Mg2+/NH4+ exchange was measured by chemical analysis and the salt crystallization was monitored by the turbidity of the solution. The stability of the supersaturated solution was evaluated as a function of the functional group and matrix type of the ion exchanger. The effective diffusion coefficients were calculated by fitting the experimental data to the unreacted core model. The values calculated were dependent on the stability of the intraparticular solution.