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.
Catalysts based on electroless nickel and bi-metallic nickel-molybdenum nanoparticles were synthesized for the hydrolysis of sodium borohydride for hydrogen generation. The catalysts were synthesized by polymer-stabilized Pd nanoparticle-catalyzation and activation of Al 2 O 3 substrate and electroless Ni or Ni-Mo plating of the substrate for selected time lengths. Catalytic activity of the synthesized catalysts was tested for the hydrolyzation of alkaline-stabilized NaBH 4 solution for hydrogen generation. The effects of electroless plating time lengths, temperature and NaBH 4 concentration on hydrogen generation rates were analyzed and discussed. Compositional analysis and surface morphology were carried out for nano-metallized Al 2 O 3 using Scanning Electron Micrographs (SEM) and Energy Dispersive X-Ray Microanalysis (EDAX). The as-plated polymer-stabilized electroless nickel catalyst plated for 10 min and unstirred in the hydrolysis reaction exhibited appreciable catalytic activity for hydrolysis of NaBH 4 . For a zero-order reaction assumption, activation energy of hydrogen generation using the catalyst was estimated at 104.6 kJ/mol. Suggestions are provided for further work needed prior to using the catalyst for portable hydrogen generation from aqueous alkaline-stabilized NaBH 4 solution for fuel cells.
Electrochemical and thermodynamic data obtained from the determination of the corrosion potentials of Cu and Pd in various reducing agents (formaldehyde, hypophosphite and ammonia borane) and their mixtures was used to formulate a stable electroless bath for co-deposition of Cu and Pd on Al2O3 substrate. The electrolessly deposited Pd-Cu catalyst was characterized using SEM, EDAX and BET measurements. The Pd-Cu catalyst on alumina was found to be active for nitrate reduction in aqueous solution. The activity and composition of the catalyst increased with electroless plating time up to 30 minutes whereupon the variation of metal composition was minimal. The BET measurement showed that the electroless plating decreases the BET surface area of the catalyst thereby suggesting a macroporous mechanism for nitrate reduction on electroless Pd-Cu catalyst. The supported electroless Pd-Cu catalyst converted most of the nitrate in solution into preferred nitrogen gas product rather than ammonia.
Catalytic hydrolysis of alkaline NaBH4 solution and ammonia borane using electroless-based transition metal catalysts have been studied. The transition metal catalysts were synthesized by Pd catalyzation and activation of Al2O3 or TiO2 substrates and subsequent electroless plating of the transition metals. Results will be presented on the effect of Pd loading, annealing temperature of the catalyst, electroless plating time on the catalyst activity for hydrogen generations. Kinetic data of the hydrolysis reaction will also be discussed.
The separation of lanthanides and actinides using the liquid-liquid extraction technique poses a major challenge due to the chemical similarities of the two groups of metals. Hence, interest exists in devising a technique to improve the separation factor. The use of an imposed external field (electrochemical) to improve the liquid-liquid extraction has been explored in the literature with limited success due to conductivity issues. In this work, the use of reverse micelle solutions containing water/AOT-HDEHP/n-dodecane for improved electrical conductivity will be explored. The results of a feasibility study of electrochemical modulation of neodymium extraction using the reverse micelles/microemulsions will be presented.
Electrochemical impedance technique was used to determine the effect of molar content of water, Wo, on the reverse micelle solution conductivity. The distribution ratio of Nd in an electrochemically modulated liquid-liquid extraction containing reverse micelles will also be presented. The mechanism of electrochemical modulated liquid-liquid metal ion extraction will be explored.
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