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”.

The Removal of Rare-Earth Metals from Water-Salt Systems – An Innovative Aspect of the Modern Industry

“…According to the literature data, in the process of ion flotation of metal cations, the increase in removal occurs in the рН range of hydrate formation [30,31], that is the metal cations passing into froth as hydroxides is observed. In a number of papers [1,15,18] it was discovered that to identify the mechanism of metal cations removal by ion flotation one should know the рН of metal hydroxo complexes and рН of hydrate formation. The рН value of Yb(ОН) 2+ hydroxo complexes formation is calculated based on the expression for instability constant.…”

“…According to literature data, an increase of process effectiveness because of valuable components extraction from production wastes is possible when using the ion flotation method in mining industry [18,20]. At that, the decrease of REE toxicity, and the risk of damaging the environment, is presumed.…”

“…At that, the decrease of REE toxicity, and the risk of damaging the environment, is presumed. In papers [18,20,22] the ion flotation method is proposed for REE removal from apatite sulphuric acid processing products.…”

“…To identify the process mechanisms of metal cations removal and separation by ion flotation method, one should know the рН of metal hydroxo complexes formation and рН of hydrate formation, calculated based on the Gibbs energies of hydroxo complexes and metal hydroxides formation (Table 1). The рН value of Yb(ОН) 2+ hydroxo complexes formation can be calculated based on the expression for instability constants [18]. A special feature of Russian raw material sources is the REE low content and complex chemical and mineralogical composition.…”

Ion Flotation of Ytterbium Water-Salt Systems—An Innovative Aspect of the Modern Industry

“…To identify the process mechanisms of metal cation removal and separation by the ion flotation method, it is necessary to know know the pH of metal hydroxo complexes formation and the pH of hydrate formation, calculated based on the Gibbs energies of hydroxo complexes and metal hydroxides formation (Table 1). The pH value of Yb(OH) 2+ hydroxo complexes formation can be calculated based on the expression for instability constants [18]. A special feature of Russian raw material sources is the low REE content and complex chemical and mineralogical composition.…”