Clay supported extractants for hydrometallurgical applications.
This project investigated the feasibility of derivatizing a montmorillonitic
clay, with commercial liquid extractants to obtain a material with the metal extraction
properties of the liquid extractant that can be applied directly into metal leaching
The intercalation of several commercial liquid-liquid extractants:
alkylphosphoric acid (DEHP A), carboxylic acid (Versatic 1 0), l3-hydroxyoxime
(Acorga M-5640), substituted hydroxyquinoline (Kelex 100) and l3-diketone (LIX
54) was carried out. The alkylphosphoric extractant, DEHPA, was taken as a model
for obtaining data on parameters that influence the adsorption of the molecule onto
the clay. The variables studied were the kinetics of adsorption, effect of composition
of the selected solvent media (EtOHIH20) and interlayer cations both inorganic (Na+,
Ca2+ and Cu2+) and organic (alkylammonium). Optimum conditions obtained for the
alkylphosphoric extractant were then applied to the other extractants.
X-ray powder diffraction and FTIR characterisation confirmed that the
extractant molecule was adsorbed in the interlayer spaces of the clay. The adsorption
process showed fast kinetics (five to fifteen minutes), was strongly related to the
water content of the solvent media and to the nature of the interlayer cation. The
mechanisms for the adsorption of the extractant on the homoionic inorganic and
organic clays are discussed.
All the intercalated materials extract copper and nickel ions from solution and
the metal loadings are similar to materials such as Solvent Impregnated Resins (SIR).
The loading isotherms and maximum loading capacities indicate the formation of
both 2: 1 and the charged 1: 1 extractant:metal complexes. Extractant losses from the
alkylphosphoric intercalated montmorillonites during use compare very favourably
with similar liquid-liquid systems or SIR's containing the same extractant.
Attempts to agglomerate the resulting intercalated material to obtain pellets
between 1 and 2 mm in diameter were made using different inorganic and organic
polymeric binders. The most effective binder was a crosslinked polyester obtained by
in-situ polymerisation on the clay. The resulting clay-extractant pellets retained their
metal extraction properties with acceptable mechanical properties, but the process
requires further optimisation.