Disclosed are methods for purifying polyols containing oxyalkylene units that is an alkali metal catalyzed alkoxylation reaction product of an alkylene oxide and an H-functional starter. The methods include neutralizing the alkali metal ions with an aqueous solution comprising water and sulfuric acid, in which: (i) the sulfuric acid is present in an amount of no more than 5% by weight, based on the total weight of the aqueous solution, and (ii) the sulfuric acid is used in an amount of 2% to 10% more than the theoretical amount necessary to neutralize all of the alkali metal ions present. The methods can produce polyols having a low content of 2-methyl-2-pentenal.