Phase equilibria in the system H2O-NaCl-KCl-MgCl2 relevant to salt cake processing

One of the waste products produced by the recycling of aluminum is salt cake, a mixture of aluminum, salts, and residue oxides. Several methods have been proposed to recycle salt cake; one of these involves high-temperature leaching of salts from the salt cake. The salt composition in salt cake can be approximated as a mixture predominantly of sodium and potassium chloride salts, with lesser amounts of magnesium chloride. In order to better assess the feasibility of recycling salt cake, an experimental study was conducted of phase equilibria in the system H2O-NaCl-KCl-MgCl2 at pressure, temperature, and composition (PTX) conditions appropriate for high-temperature salt cake recycling. These experiments were designed to evaluate the effect of small amounts (2-10 wt.%) of MgCl2 on solubilities of halite (NaCl) and sylvite (KCI) in saturated solutions (30-50 wt.% NaCl + KCl; NaCl:KCl = 1:1 and 3:1) at elevated P and T.