A process for preparing D-glucaro-6,3-lactone from a salt of D-glucaric acid is provided. The process includes: adding a mineral acid to a pre-cooled solution including a salt of D-glucaric acid, water, and acetone to obtain a crude mixture; allowing the crude mixture to rise to a temperature in a range of ≥15° C. to ≤35° C. and stirring the crude mixture; filtrating the crude mixture and washing with an acetone and water solvent mixture to obtain a filtrate; concentrating the filtrate under vacuum pressure to obtain a concentrated filtrate having a water content in a range of ≥20.0 wt. % to ≤40.0 wt. %, relative to an overall weight of the concentrated filtrate; storing the concentrated filtrate at a temperature in a range of ≥0° C. to ≤5° C., and optionally repeating the concentrating and storing steps to obtain a precipitate comprising D-glucaro-6,3-lactone.