Sugarcane stillage is rich in tri-carboxylic aconitic acid. To study its purification through anionexchange, selectivity coefficients between aconitate and the major competing minerals were determined on a weak-base resin for different pH. Simulation of solutes separation in column, using mass conservation equations and equilibrium theory, confirmed that resin in sulfate form and pH = 4.5 led to the best separation performances, and showed that a preliminary chloride removal up to 0.5 g L -1 was the most profitable to increase the ionic exchange capacity for aconitic acid. Demineralization of a real stillage by conventional electrodialysis followed by the optimized ion-exchange step, led to an aconitic acid-rich extract.