A synergistic combination of dichloromethane and Aliquat 336 for selective extraction of copper, nickel, zinc, and cadmium from industrial waste

The depletion of mineral resources and the escalating environmental pollution caused by industrial waste have underscored the urgent need for efficient metal recovery from these waste streams. This research focuses on the selective extraction of Cu(II), Ni(II), Zn(II), and Cd(II) from industrial lead plant waste, employing a synergistic combination of Dichloromethane (DCM) and Aliquat 336 (A336) and individual solvent extraction using these solvents. The accuracy of the synthesized task-specific ionic liquids (TSILs) (Et₃NC₂NHC₄ and Bu₃NC₂NHC₄) was investigated using FTIR and H-NMR analysis. The structure of the TSIL was optimized by TSIL experiments with a range of anions (Cl^-, NO₃^-, HSO₄^-, and CH₃COO^-) and ammonium cations with varying alkyl chain lengths, and [Bu₃NC₂NHC₄][Cl] was chosen as an extractant to extract the mentioned metals. Subsequently, solvent extraction experiments were conducted to optimize key parameters, including pH, TSIL concentration, TSIL reaction time, phase contact time, and the aqueous-to-organic phase ratio (A/O). The stripping stage used sulfuric acid (H₂SO₄) at varying concentrations. The DCM system demonstrated optimal extraction at a pH of 3, with 150 mg of TSIL, a 5-minute reaction time, a 5-minute contact time, and an A/O ratio of 2:1. The A336 system exhibited similar optimal conditions. Notably, the synergistic combination of DCM and A336 attained the highest extraction efficiency (%E) at a pH of 2, with a 40% DCM fraction in the total organic phase. The concentrations of metal ions in the aqueous phase were specified with atomic absorption spectroscopy. The possibility of metal recovery from the loaded ionic liquid phase using H₂SO₄ was also investigated, demonstrating the reusability of the ionic liquids.