Integrated Diffusion Dialysis—Precipitation to Separate and Recover Sulfuric Acid and Iron from Spent Iron Pickling Bath: Precipitation in Diverse Media

This study investigates a hydrometallurgical process for the separation of sulfuric acid and iron from iron pickling baths at the El Hadjar plant in Algeria. The process utilizes an integrated system consisting of diffusion dialysis (DD) to reduce acidity, followed by the precipitation of ferrous ions in various media: hydroxide, carbonate, sulfide, and phosphate. Thermodynamic predictions were made through calculations and plotting log S as a function of pH to identify optimal pH conditions that favor iron precipitation. The results indicate a recovery yield of approximately 87% for sulfuric acid and nearly 99% for iron in phosphate and sulfide medium, as well as 95% in hydroxide and 91% in carbonate medium. Infrared analysis of the different iron precipitates indicate excellent quality, further confirming the effectiveness of this process. This integrated method enhances acid recovery and waste minimization while providing a sustainable solution for the steel industry, demonstrating effective and selective separation through diffusion dialysis coupled with precipitation.