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82 PCB007 MAGAZINE I MAY 2022 Liquid-Liquid Extraction Liquid-liquid extrac- tion (LLE) or Liquid ion- exchange has been used for metal recover y from mining for many years. But in the early 1970s, a new organic extractant was developed out of wheat by General Mills. is new metal chelat- ing agent is 7-ethyl-undeca- 2,4-dione, trademarked by General Mills as LIX64N and LIX65N. is organic is dis- solved and mixed with kero- sene (~20% dissolution) and has an extremely high affin- ity for copper and zinc. 3 e unique feature of these compounds with respect to metal chelating is that, in the extraction step, the base metal is capable of being loaded to the exclu- sion of ammonia or chlorides, thereby result- ing in essentially a zero carryover of ammonia/ chlorides to the stripping step. Moreover, in the stripping step the extractant does not form a salt with the acid present and hence can be recycled directly to the extraction stage with- out the necessity of further treatment. e extraction and regeneration process are shown in Figure 1. 4 Figure 2 is a diagram of a mixer-separa- tor unit that shows the mixing and separating chamber where the organic phase is less dense and floats on the aqueous phase to extract Figure 1: The LLE process for alkaline or acid etchant Cu recovery. (Source: King Industries) Figure 2: Diagram of a mixer-separator for LLE. (Source: Sigma Engineering)