Separation of traces of heavy metals from an iron matrix by use of an emulsion liquid membrane

Abstract

An emulsion liquid membrane method has been developed for separating traces of heavy metals from an iron matrix. A 1.0-mL volume of aqueous iron(III) solution (pH 2.0) was emulsified with a mixture of 0.6 mL toluene, 2.4 mL n -heptane, and 80 mg sorbitan monooleate (Span-80). The resulting water-in-oil type emulsion was gradually injected into 25 mL of 1.5 mol L(-1) hydrochloric acid solution containing 30 mmol L(-1) 8-quinolinol and 1.0 mol L(-1) of ammonium sulfate and was dispersed as numerous tiny globules by stirring for 40 min. More than 90% of the iron(III) diffused through the oil layer to the external hydrochloric acid solution with the aid of complexation with 8-quinolinol, whereas trace heavy metals, e.g. Cr(III), Mn(II), Co(II), Ni(II), Cu(II), and Pb(II), remained quantitatively in the internal aqueous phase. After collecting the dispersed emulsion globules, they were demulsified and trace metals in the segregated aqueous phase were determined by graphite-furnace atomic absorption spectrometry. Owing to sufficient removal of the iron matrix trace metal impurities in high-purity iron were successfully determined without interference, as was confirmed by analysis of certified reference materials.

Emulsion liquid membrane for heavy metal removal: An overview on emulsion stabilization and destabilization

“…The ultrasound emulsification studies in production of W/O emulsions resulted globules diameter ranging from 0.01 to 0.1 mm [32,33]. While the emulsion droplets diameter was found to be 50 nm-1.5 m [15,34].…”

“…A rather stable emulsion can therefore be formed in a relatively shorter processing time [23]. Although ultrasound has been proved to be potential for emulsification, but only few studies focused on using this technique for preparing the W/O emulsions as used in ELM processes of heavy metal ions recovery [30][31][32][33][34]. This may be due to the production of W/O emulsions with high viscosity of continuous phase need higher threshold ultrasonic intensity compared to O/W emulsions.…”

“…This was a result of the increases in the ionic strength difference between internal and external phases that resulted in an increase in swelling, which resulted in greater amounts of water to permeate through the membrane causing the internal droplets to swell and coalesce. The osmotic pressure difference between the internal and external phases is most probably responsible for the swelling [34]. Other researcher found that concentration of sulfuric acid for cobalt extraction which gives the lowest breakage is 0.5 M [25].…”

A Novel Liquid Emulsion Membrane Containing TODGA as the Carrier Extractant for Am Recovery from Acidic Wastes

“…Additionally, simultaneous extraction and stripping make the liquid membrane based separation method an attractive proposition as third phase formation becomes a distant possibility. Out of the liquid membrane based separation methods, liquid emulsion membranes (LEM) have been particularly attractive due to faster mass transfer rates and there are several reports on the separation of transition metal ions (18)(19)(20)(21), toxic metal ions (22)(23)(24)(25)(26), and even actinide ions (27,28), though literature on actinide separations is very limited. In case of LEM methods also, the limitations of solvent extraction appear to be alleviated due to lower metal ion loading which is a consequence of simultaneous stripping.…”

Ionic Liquid-based Extraction of Heteropoly Molybdic Acids for the Sensitive Determination of Si, P, and As in High-purity Iron

“…During the course of our study on the separation techniques for the analysis of iron metals, [10][11][12][13] we found that a polyoxyethylene-type nonionic surfactant-coated resin provided the quantitative extraction of heteropoly molybdic acids. 13) The desorption was made by decomposing them with an alkaline reagent and the obtained solution was acidified again to form heteropoly molybdic acids for the determination by high-performance liquid chromatography (HPLC).…”