Extraction of zinc from spent pickle liquor using primary amine extraction system

Spent pickle liquor is a hazardous liquid containing zinc and iron ions, and other environmentally harmful elements. Therefore, its discharge is prohibited because of ecological and environmental issues. A novel cleaning process for the recovery of Zn from spent pickle liquor using solvent extraction was proposed. The extraction system comprised a secondary carbon primary amine (N1923), isooctanol, and sulfonated kerosene. Spent pickle liquor after ultrasonic enhanced reduction pretreatment was studied experimentally, and effective parameters such as the extractant concentration, organic phase composition, and phase ratio (O/A) on the extraction were investigated. The extractant N1923 was found to selectively extract Zn(II) from the spent pickle liquor and retain Fe(II) in the raffinate. The concentration of Zn(II) ions in raffinate obtained using three-stage counter-current extraction was only 0.01 g/L. The raffinate could be further used to prepare an iron salt water purifier. A solution of H2SO4 was used to strip Zn from the loaded organic phase, yielding a Zn-rich solution containing 5.39 mol/L Zn, which could be used to prepare ZnO. The unloaded organic phase was recycled, and no emulsification or scale accumulation was observed during the process. The structure of the extracted complex was determined using the slope and loading capacity methods, and combined with FT-IR analysis. The main reaction that occurs during the extraction process is the anion-exchange reaction, with a stoichiometric ratio of N1923 to zinc ions of 1, resulting in an extracted complex of RNH3ZnCl3. Overall, the process provided an efficient, low-consumption, convenient, safe, and sustainable method for recovering Zn from spent pickle liquor and laying the foundation for industrial applications.