Neodymium and gadolinium extraction from molten fluorides by reduction on a reactive electrode

This work describes the electrochemical extraction on a reactive cathode (Cu, Ni) of two lanthanides Ln (Ln = Nd and Gd) from molten LiF-CaF2 medium at 840 and 920°C for Nd and 940°C for Gd. Extraction runs have been performed and the operating conditions (cathodic material and temperature) optimised. The titration of the Nd and Gd concentrations in the melt during extraction used square wave voltammetry. At the end of each run, the residual Ln content was checked by ICP-AES; the extraction efficiencies of the two lanthanides were found to be more than 99.8% on both reactive substrates

Dynamics of electrocrystallization of dendritic zinc deposits in galvanostatic and potentiostatic modes

In the work the dynamics of growth of zinc dendritic deposits in the galvanostatic and potentiostatic modes from an electrolyte containing 0.3 mol/L of ZnO, and 4 mol/L of NaOH has been studied. It has been shown that in galvanostatic conditions decrease in the elongation rate of dendrites and change in the deposit structure from dendritic to compact accompanied by increasing density and decreasing through-thickness porosity are observed. In potentiostatic conditions dendrites grow at a constant rate and the structure of the deposit varies little. The results have been confirmed by electron microscopic studies of morphology of zinc particles

Rapid and Efficient Arsenic Removal by Iron Electrocoagulation Enabled with in Situ Generation of Hydrogen Peroxide.

Millions of people are exposed to toxic levels of dissolved arsenic in groundwater used for drinking. Iron electrocoagulation (FeEC) has been demonstrated as an effective technology to remove arsenic at an affordable price. However, FeEC requires long operating times (∼hours) to remove dissolved arsenic due to inherent kinetics limitations. Air cathode Assisted Iron Electrocoagulation (ACAIE) overcomes this limitation by cathodically generating H2O2 in situ. In ACAIE operation, rapid oxidation of Fe(II) and complete oxidation and removal of As(III) are achieved. We compare FeEC and ACAIE for removing As(III) from an initial concentration of 1464 μg/L, aiming for a final concentration of less than 4 μg/L. We demonstrate that at short electrolysis times (0.5 min), i.e., high charge dosage rates (1200 C/L/min), ACAIE consistently outperformed FeEC in bringing arsenic levels to less than WHO-MCL of 10 μg/L. Using XRD and XAS data, we conclusively show that poor arsenic removal in FeEC arises from incomplete As(III) oxidation, ineffective Fe(II) oxidation and the formation of Fe(II-III) (hydr)oxides at short electrolysis times (<20 min). Finally, we report successful ACAIE performance (retention time 19 s) in removing dissolved arsenic from contaminated groundwater in rural California

Reactors for microbial electrobiotechnology

From the first electromicrobial experiment to a sophisticated microbial electrochemical process - it all takes place in a reactor. Whereas the reactor design and materials used strongly influence the obtained results, there are no common platforms for MES reactors. This is a critical convention gap, as cross-comparison and benchmarking among MES as well as MES vs. conventional biotechnological processes is needed. Only knowledge driven engineering of MES reactors will pave the way to application and commercialization. In this chapter we first assess the requirements on reactors to be used for bioelectrochemical systems as well as potential losses caused by the reactor design. Subsequently, we compile the main types and designs of reactors used for MES so far, starting from simple H-cells to stirred tank reactors. We conclude with a discussion on the weaknesses and strengths of the existing types of reactors for bioelectrochemical systems that are scored on design criteria and draw conclusions for the future engineering of MES reactors. [GRAPHICS]

Design and development of a water vapor electrolysis unit

Design and development of water vapor electrolysis unit for oxygen productio

Static feed water electrolysis module

An advanced static feed water electrolysis module (SFWEM) and associated instrumentation for generating breathable O2 was developed. The system also generates a H2 byproduct for use in an air revitalization system for O2 recovery from metabolic CO2. Special attention was given to: (1) eliminating water feed compartment degassing, (2) eliminating need for zero gravity condenser/separators, (3) increasing current density capability, and (4) providing a self contained module so that operation is independent of laboratory instrumentation and complicated startup/shutdown procedures

Preprototype independent air revitalization subsystem

The performance and maturity of a preprototype, three-person capacity, automatically controlled and monitored, self-contained independent air revitalization subsystem were evaluated. The subsystem maintains the cabin partial pressure of oxygen at 22 kPa (3.2 psia) and that of carbon dioxide at 400 Pa (3 mm Hg) over a wide range of cabin air relative humidity conditions. Consumption of water vapor by the water vapor electrolysis module also provides partial humidity control of the cabin environment. During operation, the average carbon dioxide removal efficiency at baseline conditions remained constant throughout the test at 84%. The average electrochemical depolarized concentrator cell voltage at the end of the parametric/endurance test was 0.41 V, representing a very slowly decreasing average cell voltage. The average water vapor electrolysis cell voltage increased only at a rate of 20 mu/h from the initial level of 1.67 V to the final level of 1.69 V at conclusion of the testing

AC field effect flow control of EOF in complex microfluidic systems with integrated electrodes

In this work, we demonstrate that positive net flow can be induced and controlled with relatively low potential due to the parallel alignment of the integrated channel electrodes. Therefore, we present a novel method to exquisitely control Electro Osmotic Flow (EOF) by using integrated electrodes fabricated beneath a meandering channel geometry (Figure 1). Equation 1 describes EOF velocity for AC-driven flow, where εo and εr respectively are the permittivity of vacuum and that of water, ζ the zeta potential at the solid liquid interface, η the viscosity, Ex the electric field

Surface micromachined electrostatically actuated micro peristaltic pump

An electrostatically actuated micro peristaltic pump is reported. The micro pump is entirely surface micromachined using a multilayer parylene technology. Taking advantage of the multilayer technology, the micro pump design enables the pumped fluid to be isolated from the electric field. Electrostatic actuation of the parylene membrane using both DC and AC voltages was demonstrated and applied to fluid pumping based on a 3-phase peristaltic sequence. A maximum flow rate of 1.7 nL min^–1 and an estimated pumping pressure of 1.6 kPa were achieved at 20 Hz phase frequency. A dynamic analysis was also performed with a lumped-parameter model for the peristaltic pump. The analysis results allow a quantitative understanding of the peristaltic pumping operation, and correctly predict the trends exhibited by the experimental data. The small footprint of the micro pump is well suited for large-scale integration of microfluidics. Moreover, because the same platform technology has also been used to fabricate other devices (e.g. valves, electrospray ionization nozzles, filters and flow sensors), the integration of these different devices can potentially lead to versatile and functional micro total analysis systems (µTAS)

Static Feed Water Electrolysis Subsystem Testing and Component Development

A program was carried out to develop and test advanced electrochemical cells/modules and critical electromechanical components for a static feed (alkaline electrolyte) water electrolysis oxygen generation subsystem. The accomplishments were refurbishment of a previously developed subsystem and successful demonstration for a total of 2980 hours of normal operation; achievement of sustained one-person level oxygen generation performance with state-of-the-art cell voltages averaging 1.61 V at 191 ASF for an operating temperature of 128F (equivalent to 1.51V when normalized to 180F); endurance testing and demonstration of reliable performance of the three-fluid pressure controller for 8650 hours; design and development of a fluid control assembly for this subsystem and demonstration of its performance; development and demonstration at the single cell and module levels of a unitized core composite cell that provides expanded differential pressure tolerance capability; fabrication and evaluation of a feed water electrolyte elimination five-cell module; and successful demonstration of an electrolysis module pressurization technique that can be used in place of nitrogen gas during the standby mode of operation to maintain system pressure and differential pressures