Separation and recovery of rare earth elements from spent nickel–metal-hydride batteries using synthetic adsorbent

Abstract

The recovery of rare earth elements such as La(III) and Nd(III) from spent nickel–metal hydride (NiMH) battery by novel synthetic adsorbent were investigated. First, layered double hydroxide (LDH)-A (A- anion of carrier) been prepared and characterized by different methods. Second, the separation and recovery of some rare earth elements (La(III) and Nd(III)) from acidic solutions using the synthetic adsorbent were investigated. The adsorption percent of the two metal ions was found to increase with increasing contact time, adsorbent weight and pH from 0 to 1 then it remains constant in the pH range (1–2). La(III) was preferentially adsorbed over Nd(III) in the mixture solution. From characterization of the adsorbent results, the adsorption mechanism of LDH-A adsorbent was proposed with rare earth elements. It was found that the highest separation factor (SLa/Nd) value of 23.2 was obtained with 10g/l (0.1g/10ml) from a mixed solution of 5g/l of each of La(III) and 5g of Nd(III) at pH1 and contact time 2h. Based on the experimental results, a separation method was developed and tested to separate high purity Co(II), Ni(II) and rare earths from Ni-MH batteries leached by 2.0M H2SO4 and the rare earths are leached by 2M HCl. Based on the experimental results, a flow sheet was developed and tested and 1.2g La(III) and 1g Nd(III) were obtained from the leaching process.