Method for the preparation of lactic acid and calcium sulphate dihydrate

摘要

The invention relates to a method for the preparation of lactic acid and calcium sulphate, in which (a) an aqueous solution that contains lactate is reacted with sulphuric acid at a temperature that is essentially higher than the transition temperature of calcium sulphate dihydrate (CaSO4.2H2O), with the formation of a mixture that contains calcium sulphate hemihydrate and lactic acid, (b) the mixture from step (a) is subjected to at least one recrystallisation step at a temperature that is essentially lower than the transition temperature of calcium sulphate dihydrate, with the formation of a precipitate of calcium sulphate dihydrate and an aqueous solution of lactic acid, and (c) the precipitate of calcium sulphate dihydrate is separated off from the aqueous solution of lactic acid.