The invention provides a method for recrystallizing and purifying desulphurized
gypsum, which mainly comprises the four steps of acid-washing,
dissolution,
crystallization and washing, and specifically comprises the following steps of: removing impurities, reacted with acids, in the desulphurized
gypsum by the aid-washing, dissolving
calcium sulphate in the desulphurized
gypsum into the acid solution at a relatively higher temperature by utilizing the characteristic that the
solubility of the
calcium sulphate in the specific acid solution is remarkably changed with the temperature, performing
solid-liquid separation to remove undissolved
solid-phase impurities at the high temperature, performing cooling recrystallization and the
solid-liquid separation on a
liquid phase at a relatively lower temperature, and washing and
drying a
filter cake to obtain high-purity gypsum, wherein the
liquid phase in the
dissolution and recrystallization processes can be reused. Through the method provided by the invention, the gypsum with relatively higher purity and whiteness can be prepared by selecting a proper solid-to-
liquid ratio, proper temperatures and proper
acid concentration and performing
dissolution and
crystallization for a certain time, and the performance of the desulphurized gypsum is remarkably improved.