Improving Extraction Performance of D2EHPA for Impurities Removal from Spent Lithium-Ion Batteries Leaching Solution by TPC[4]

To reduce reagent consumption, wastewater discharge, and production cost of Mn²⁺ recovery and impurities (Zn²⁺/Cu²⁺/Ca²⁺) removal from an acid leaching solution of spent lithium-ion batteries, a mixed extractant (TPC[4]+D2EHPA) was synthesized, and the extraction performances for Mn²⁺ and impurities were systematically investigated. The synthesis experimental results demonstrated that TPC[4] can be synthesized in a simple and high yield way with cheap raw materials. Extraction tests indicated that the separation coefficients of Mn²⁺, Cu²⁺, and Zn²⁺ to Ni²⁺ and Co²⁺ by D2EHPA were significantly enlarged by the addition of TPC[4], which can mainly be attributed to the enhancement in the differences of binding abilities for cationic complexes with different sizes. Furthermore, the loading capacities of Mn²⁺ and impurities (Cu²⁺, Zn²⁺) were also enlarged, and the stripping of these cations could easily be achieved with dilute acid. Compared with traditional Mn²⁺ and an impurities extraction process with D2EHPA alone, the addition of TPC[4] saved about 10.36% of the saponification alkali (NaOH), 10.36% of the washing acid (H₂SO₄), ～20% of the washing water, and more than 4.56% of the organic loss. From both economic and environmental perspectives, the mixed solvent of D2EHPA+TPC[4] is an excellent application prospect.