Sulfuric acid is used in a number of industrial processes, including for example for semiconductor wafer cleaning, as dehydrating agent for the distillation of nitric acid or as solvent, e.g. for aramid processing. The purification of sulfuric acid by distillation is known. Usually, the aim of the distillation is to remove impurities and to concentrate the sulfuric acid to e.g. 96 wt. In those instances, the initial sulruric acid concentration is usually relatively low and the water/acid mixture is below the azeotrope. Thus, conventional one-stage or multi-stage distillation to remove water and impurities to increase the sulfuric acid content is sufficient. However, at sulfuric acid concentrations of approximately 98.5-98.7 wt (depending on pressure and temperature), the sulfuric acid mixture is an azeotrope and cannot be concentrated further by conventional distillation.
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