What are the preparation methods of anhydrous magnesium sulfate

       There are various methods for preparing anhydrous magnesium sulfate (MgSO ₄), including sulfuric acid method, recrystallization method, and brine method. The following are detailed descriptions of these methods:
       1、 Sulfuric acid method
       The sulfuric acid method is one of the commonly used methods for preparing anhydrous magnesium sulfate, with the following main steps:
       Raw material preparation: Prepare magnesium oxide (MgO), magnesium hydroxide (Mg (OH) ₂), or magnesium carbonate (MgCO3).
       Reaction process: The above raw materials are reacted with sulfuric acid (H ₂ SO ₄) to produce magnesium sulfate heptahydrate (MgSO ₄ · 7H ₂ O).
       Dehydration treatment: Heat the generated magnesium sulfate heptahydrate at 200 ° C to remove its crystal water and convert it into anhydrous magnesium sulfate.

       2、 Recrystallization method
       The recrystallization method is suitable for purifying anhydrous magnesium sulfate from industrial magnesium sulfate, and the main steps are as follows:
       Dissolve: Add industrial magnesium sulfate (MgSO ₄· 7H ₂ O) into the dissolution tank and dissolve in water.
       Purification: Removing impurities such as heavy metal sulfates by settling or filtering.
       Concentration and crystallization: Concentrate the filtrate, then cool and crystallize to obtain refined magnesium sulfate heptahydrate.
       Dehydration: Dry refined magnesium sulfate heptahydrate at 200 ° C to remove crystal water and obtain anhydrous magnesium sulfate.
       3、 Sea lake bitter brine method
       The sea lake bittern method uses bittern from salt lakes or seawater to prepare anhydrous magnesium sulfate, with the main steps as follows:
       Bitter brine evaporation: The bitter brine from salt lakes or seawater that has been sun dried is naturally evaporated and concentrated to obtain crude magnesium sulfate.
       Dissolve and Clarify: Dissolve crude magnesium sulfate in water at 80-90 ° C, and then clarify at 60-70 ° C.
       Cooling crystallization: Cool the clarified solution to 20-25 ° C to crystallize magnesium sulfate heptahydrate.
       Separation and drying: Magnesium sulfate heptahydrate obtained by centrifugal separation is then dried at 200 ° C to obtain anhydrous magnesium sulfate.
       There are various methods for preparing anhydrous magnesium sulfate, with sulfuric acid method and recrystallization method being common industrial production methods, while the sea lake bittern method utilizes natural resources and has cost advantages. The selection of an appropriate preparation method needs to be determined based on the source of raw materials, production scale, and product quality requirements.