Preparation of a MgCl.sub.2 solution for Nalco's MgCl.sub.2 process from MgSO.sub.4 and other MgSO.sub.4 salts

A method for the beneficiation of mixed salts containing potassium and magnesium sulfates which allows the recovery of anhydrous MgCl.sub.2 and the recovery of potassium sulfate, said method comprising the steps:

• (a) Dissolving a mixed double salt containing magnesium and potassium sulfates in water at a temperature between 50.degree. C. and 90.degree. C. and then filtering the residue from the solution;
• (b) Adding to and dissolving into the filtered solution of (a), a molar equivalent of potassium chloride, the molar equivalent calculated on the solubilized magnesium cation requirement for chloride ion, thereby forming a solution;
• (c) Heating the solution produced in step (b) within the range of 50.degree. C.-90.degree. C. for a period of time to allow equilibrium to be established, thereby forming an equilibrated solution;
• (d) Adding sufficient ethylene glycol to the equilibriated solution of (c) to fully dissolve all MgCl.sub.2 calculated to be present, then removing from solution the K.sub.2 SO.sub.4 which precipitated on the addition of said ethylene glycol;
• (e) Distilling water from the solution of step (d) thereby forming an anhydrous MgCl.sub.2 solution in ethylene glycol and a precipitate of K.sub.2 SO.sub.4, then removing said precipitate from said solution;
• (f) Combining the K.sub.2 SO.sub.4 precipitate of steps (d) and (e) and washing said precipitates with sufficient water maintained below 70.degree. C. to remove entrained ethylene glycol, and recovering the washed K.sub.2 SO.sub.4 ;
• (g) Treating the anhydrous MgCl.sub.2 solution in ethylene glycol formed in step (e) with anhydrous ammonia to form a MgCl.sub.2 ammonia complex which precipitates from the ethylene glycol solution;
• (h) Removing the complex precipitate from the ethylene glycol and washing it with a low boiling solvent for ethylene glycol to remove any ethylene glycol entrained in the precipitate;
• (i) Heating the magnesium chloride ammonia complex to drive off ammonia leaving as a finished product completely anhydrous magnesium chloride.