Iron removal using hydrochloric acid, hydrochloric acid decolorization technology.

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The hydrochloric acid pickling method refers to the process of using an aqueous solution of hydrochloric acid with a concentration of 5% to 20% to remove the oxide scale and adhered salts from the surface of the workpiece. Hydrochloric acid is currently a widely used pickling raw material in hot-dip galvanizing enterprises. The lower the mass fraction of acid, the longer the pickling time required. Additionally, the temperature of pickling has a significant impact on the pickling speed. When pickling the workpieces, iron salts gradually deposit in the tank. When the iron salt concentration reaches 150–200 g/L, the tank still contains a certain amount of free acid and can be used for some time, but unless the temperature is increased, the pickling speed will **decrease**. At this point, no more new acid can be added; it must all be processed. The resin specifically designed for removing iron from hydrochloric acid exhibits excellent adsorption properties for iron-chloride complexes. It allows for large-scale treatment, is easy to regenerate, and requires simple operation. The concentrated hydrochloric acid treated with this resin has an iron ion concentration of less than 1 ppm and is colorless in appearance. This resin is mainly used for removing iron from industrial hydrochloric acid and reagent-grade hydrochloric acid. It can also be utilized for treating the hydrochloric acid produced as a by-product in paraffin chloride manufacturing plants, with the iron content after treatment meeting the requirements for industrial use.