Sulfuric acid recovery through solvent aided decomposition of ammonium sulfate

A process for the recovery of sulfuric acid through ammonium sulfate (1) is described. This process is based on extraction-aided disproportionation of arrmonium hydrogen sulfate to ammonium sulfate and sulfuric acid. Acid-base couple solvents were found to be more suitable for this process than oxygenated solvents as they can operate at higher temperatures and concentrations. A solvent composed of 0.50M methyl tricaprylyl ammonium salt of dinonyl naphthalene sulfonic acid in aromatics-free white spirits, was chosen. Sulfuric acid, at a concentration of about 35%, can be obtained from the H₂SO₄-(NH₄)₂SO₄-H₂O system. This disproportionation may be applied to recover sulfuric acid from gypsum. CaSO₄ is converted in reaction with carbon dioxide, ammonia and water to CaCO₃ and arrmonium sulfate, which is thermally decomposed to ammonia and arrmonium hydrogen sulfate. The overall process is equivalent to the displacement of H₂SO₄ from CaSO₄ by means of CO₂ and thermal energy.