Electrochemical Impedance Spectroscopy (EIS) Characterization of Water/Sodium Bis(2-Ethylhexyl) Sulfosuccinate-HDEHP/n-Dodecane Reverse Micelles for Electroextraction of Neodymium

Abstract

The extraction and separation of metal ions in the lanthanide series using the liquid-liquid extraction (LLX) technique poses a major challenge due to the chemical similarities of the metals and hence interest exists in devising a technique to improve the separation factor. In this work, sodium bis(2-ethylhexyl) sulfosuccinate (AOT) is explored for improved organic phase conductivity to aid the use of an imposed external field to improve the LLX. The electrochemical impedance spectroscopy (EIS) technique was used to determine the effect of molar water content, AOT and HDEHP (bis(2-ethylhexyl) phosphoric acid) concentration, and the temperature on the reverse micelle solution conductivity. Results showed that as AOT concentration and water content increases, conductivity increases until the reverse micelles collapse. The addition of HDEHP caused a significant drop in solution conductivity. For a mixed AOT and HDEHP system and at a small applied external field range of 0-1.4 kV m −1 and 60 rpm stir rate, a significant improvement in Nd extraction was observed relative to the traditional LLX using HDEHP only. With AOT only, a 40% improvement in extraction was observed with applied field relative to the absence of field. Cost consideration favors the use of mixed AOT and HDEHP at a slow stir rate for improved Nd extraction.

Micelle Mediated Extraction of Neodymium and Electrochemical Characterization of AOT Reverse Micelles

“…At higher temperature, increased Brownian motion reduced the time micelles are in a fixed position, spreading out the conductive regions and thus reducing the resistance of transfer, increasing conductivity. Moreover, it theorized that beyond certain temperatures, the increased Brownian motion reduces the viscosity of the system, also increasing conductivity [22]. Similar results were found by [20].…”

“…Electrochemical Impedance Spectroscopy Characterization of Water/AOT-HDEHP/n-Dodecane Reverse Micelles Systems A conductive organic phase is necessary for electrochemical extraction of metals. In a work that has been submitted for publication [22], the conductivity of the organic solvent used in the extractions was increased with AOT reverse micelles. The effect of molar water content (W o ), HDEHP, and temperature were tested for their effect on conductivity.…”

“…With a mixture of both AOT and HDEHP, there is an improvement in percent extraction when a field is applied in comparison to the absence of imposed field. The effect of mixed AOT and HDEHP is greater than the combined effect of the individual components at the stir rate of 60 rpm [22].…”

Investigations into the Extraction of Copper (II) using Methyl Isobutyl ketone solvent

“…[3] Solvent extraction with organic compounds (extractants) is the most promising method for the recovery of metals from industrial waste compared to other methods due to high productivity, economic feasibility, high speed, and simple process design. [4][5][6][7][8][9][10][11][12][13][14][15] Organophosphorus extractants are becoming increasingly important in hydrometallurgical processes [16] due to their high selectivity, good solubility of both extractants and their metal complexes in nonpolar solvents, high degree of stripping, chemical stability, acid resistance, and low cost. However, a significant disadvantage of liquid organophosphorus extractants is their high toxicity.…”

Extraction of Palladium(II) with a Magnetic Sorbent Based on Polyvinyl Alcohol Gel, Metallic Iron, and an Environmentally Friendly Polydentate Phosphazene-Containing Extractant

“…Solvent extraction with organic compounds (extractants) is the most promising method for the recovery of metals from industrial waste compared to other methods due to high productivity, economic feasibility, high speed, and simple process design [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. Organophosphorus extractants are becoming increasingly important in hydrometallurgical processes [ 22 ] due to their high selectivity, good solubility of both extractants and their metal complexes in nonpolar solvents, high degree of stripping, chemical stability, acid resistance, and low cost.…”