Understanding the regularities of recovering non-ferrous and rare earth metals from standard test solutions by flotation and solvent sublation

Abstract

This paper describes the results of experimental and theoretical studies that looked at ion exchange processes in liquid phase systems containing nonferrous metals, rare earth elements and a surfactant — i.e. sodium dodecylsulphate (NaDS). Ion flotation processes are considered in reciprocal systems containing Co+2 and Ni+2. There is a number of reasons for choosing the above salts: – The problem of removing cations of heavy metals (in particular, Co+2 and Ni+2) from water is of relevance; – At рН 7, these ions do not form hydroxides or hydroxide residue; – Co+2 and Ni+2 bond with NaDS to form easily soluble salts; – Quite a few low-cost analysis techniques are known that can detect these ions. Ion flotation processes were also examined in systems containing rare earth elements, NaCl and surfactants. The influence of Cl– ions on the distribution coefficient in Sm+3 and Eu+3 containing systems was studied by comparing instability constants typical of chlorine compounds and hydroxides. It was found that a rising concentration of NaCl is associated with a rising pH of cations of the rare earth elements of interest at the early stage of recovery and during the peak recovery. The paper considers an innovative technique to examine systems with rare earth elements and surfactants — i.e. solvent sublation. The authors examine the possibility of recovering ions of lanthanides (e.g. erbium) by solvent sublation using NaDS as a collector and isooctyl alcohol as an extractant. Many researchers believe the latter to be the best agent for such studies. The concentration of Er+3 in the standard test solutions was 0.001 mol/l. As the process develops, the concentration of extracted ions asymptotically approaches the value that is typical of a system approaching its steady state. It was established that in these conditions the maximum recovery for Er+3 is reached at рН of 8.0. This research study was funded through a scholarship granted by the President of the Russian Federation to young researchers and postgraduate students under the following project: SP-347.2019.1 “Ion flotation as an innovative and efficient technique to recover rare earth elements while concentrating dilute industrial solutions with possible identification of elements”.