Solvent Extraction of Metal Ions from Sulfate Solutions Obtained in Leaching of Spent Ni-MH Batteries

The nickel metal hydride batteries (Ni-MH) are used in many electronic equipment, like cell phones, computers, cameras as well as hybrid cars. Spent batteries can be a rich source of many metals, especially rare earth elements (REE), such as lanthanum (La), cerium (Ce), neodymium (Nd), praseodymium (Pr), samarium (Sm), gadolinium (Gd). Ni-MH batteries also contain iron (Fe) as well as non-ferrous metals, i.e. nickel (Ni), cobalt (Co), zinc (Zn), manganese (Mn), etc. Leaching of such waste with sulfuric acid solutions is one among many methods recovering of useful metals in hydrometallurgical processes. The main aim of this work was separation of metal ions from pregnant leach liquor (PLL) by solvent extraction using phosphorous compounds and ionic liquids (ILs). The initial pH of the aqueous solution was 0.1. Di (2-ethylhexyl) phosphoric acid (D2EHPA), bis (2,2,4-trimethylpentyl) phosphinic acid (Cyanex 272), and phosphoniumionic liquid – trihexyl (tetradecyl) phosphonium bis (2,4,4-trimethylpentyl) phosphinate (Cyphos IL 104) were used as the selective extractants. The initial concentration of the extractants in an organic phase was equal to 0.1 mol∙dm−3. The obtained results show that the highest extraction efficiency was obtained for Fe(III) and Zn(II) in extraction experiments with 0.1 M D2EHPA at pH of 0.1. Ni(II), Co(II) and REE remained in the aqueous solutions. In the next stage, REE were extracted with the mixture of 0.1 M Cyanex 272 and 0.1 M Cyphos IL 104 at pH equal to 3.8. Finally, Ni(II) and Co(II) ions were efficiently removed from the aqueous phase using 0.1 M solution of Cyphos IL 104 at pH around 5.4.

Characterization of PVC-based polymer inclusion membranes with phosphonium ionic liquids

Membrane techniques can be used to separate different compounds, i.e., toxic metal ions from waste waters. As any other method of separation, also this one, based on polymer inclusion membranes (PIMs), has certain limitations. One of them is the stability of membranes. In the present paper, the dependence of the physical and chemical properties on composition of PVC-based polymer inclusion membranes doped with phosphonium ionic liquids (CYPHOS IL 101, CYPHOS IL 104, CYPHOS IL 105 and CYPHOS IL 109) was studied. The thermal stability of investigated membranes was examined by thermogravimetry together with differential thermogravimetry analysis. Obtained results showed that studied PIMs are stable to the temperature of about 170 °C. The membrane morphology was examined by attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy, as well as scanning electron microscopy (SEM). The visibility of all characteristic bands in the ATR-FTIR spectra confirmed the presence of individual components in the membranes: a polymer, a plasticizer and the carriers. It also suggested that there were no signs of the covalent bond formation between the polymer, the plasticizer and the carrier. Only van der Waals or hydrogen bonds could be present. Moreover, in the SEM images of the investigated PIMs a rough surface without pores was observed.