Particulate cathode

Hu and Bautista used a fluidized-bed electrochemical reactor to recover chromium from dilute solutions [20]. The particulate cathode bed contained chromium particles (20-mesh, 450-600 pm diameter) and carbon rod current feeders which projected into the center of the fluidized bed. The lead tube anode was separated from the cathode by a porous Vycor glass tube which was selective to hydrogen ions. Current effieiency for chromium deposition varied from 8 to 22% and increased with increasing chromium concentrations and current density. The conversion ratio (the ratio of the amount of Cr(III) formed to Cr(VI) consumed) was 0.77. 

Figure 15. Basic scheme of the electrolyser with a moving particulate cathode, developed by Bergakademie Freiberg, FRG. 1 Cylindrical steel mantle, 2 layer of polypropylene or hard rubber, 3 electrolysed solution, 4 perforated lead anode, 5 cathodic current lead, 6 bed of metal spheres, 7 diaphragm, 8 supporting wheels.

Fig. 2.19 ConfiguratLons for three-diineiiaonal electrode. Only tKe cathode is shown as thr -dimen ional If the electrotyie how is suffictently high, fluidiaAtion of a particulate cathode bed may occur (a) Current how parallel to electrolyte how, (b) Curtent flow perpendicular to electrolyte flow.

In operation, a spark source is normally first flushed with argon to remove loose particulate matter from any previous analysis. The argon flow is then reduced, and the cathode is preheated or conditioned with a short bum time (about 20 sec). The argon flow is then reduced once more, and the source is ran for sufficient time to build a signal from the sample. The spark is then stopped, and the process is repeated as many times as necessary to obtain a consistent series of analyses. The arc source operates continuously, and sample signal can be taken over long periods of time. 

Electrodialysis. Electro dialysis processes transfer ions of dissolved salts across membranes, leaving purified water behind. Ion movement is induced by direct current electrical fields. A negative electrode (cathode) attracts cations, and a positive electrode (anode) attracts anions. Systems are compartmentalized in stacks by alternating cation and anion transfer membranes. Alternating compartments carry concentrated brine and purified permeate. Typically, 40—60% of dissolved ions are removed or rejected. Further improvement in water quaUty is obtained by staging (operation of stacks in series). ED processes do not remove particulate contaminants or weakly ionized contaminants, such as siUca. 

Aluminum reduction plants Materials handling Buckets and belt Conveyor or pneumatic conveyor Anode and cathode electrode preparation Cathode (haldng) Anode (grinding and blending) Particulates (dust) Hydrocarbon emissions from binder Particulates (dust) Exhaust systems and baghouse Exhaust systems and mechanical collectors... 

The cast grids are made into battery anode and cathode plates by the application of a lead oxide paste of 70 percent lead oxide (PbO) and 30 percent metallic lead. Lead ingots are tumbled in a ball mill with airproducing lead oxide and fine lead dust (referred to as leady oxide ). Leady oxide particulates are entrained in the mill exhaust air, which is treated sequentially by a cyclone separator and fabric filter. The used fabric filter bags are shipped to a RCRA-permitled commercially operated ha2ardous waste landfill located in Colorado. The leady oxide production process does not produce wastewater. 

Song HS, Kim WH, Hyun SH, and Moon J. Influences of starting particulate materials on micro structural evolution and electrochemical activity of LSM-YSZ composite cathode for SOFC. J. Electroceram. 2006 17 759-764. 

Visual detection of surface layers on cathodes using microscopy techniques such as SFM seems to be supportive of the existence of LiF as a particulate-type deposition.The current sensing atomic force microscope (CSAFM) technique was used by McLarnon and co-workers to observe the thin-film spinel cathode surface, and a thin, electronically insulating surface layer was detected when the electrode was exposed to either DMC or the mixture FC/DMC. The experiments were carried out at an elevated temperature (70 °C) to simulate the poor storage performance of manganese spinel-based cathodes, and degradation of the cathode in the form of disproportionation and Mn + dissolution was ob-served. °° This confirms the previous report by Taras-con and co-workers that the Mn + dissolution is acid-induced and the electrolyte solute (LiPFe) is mainly responsible. 

Walter Kanfmarm also reported the determination of the charge-to-mass ratio of cathode rays (abont 10 emu g- ) in a paper he submitted in April 1897 (7). Kanfmarm also based his result on magnetic deflection measurements however, he concluded that the hypothesis of cathode rays as emitted particles could not explain his data. (One of the outstanding questions in the study of cathode rays in the late 1890s was whether they were particles or electromagnetic waves. Thomson and Kanfmarm were typical of their coimtrymen most British researchers leaned toward the particulate hypothesis and most Germans toward waves.) Today Kanfmarm is better known for his careful measurements of the velocity-dependent mass of the electron published over several years beginning in 1901 these results were later explained by special relativity. 

A second effect of high fly ash resistivity is observed when the difference in potential across the collected dust layer rises to too high a value. A back corona can form as the EMF differential breaks down due to sparking across the dust layer. High currents flow between the wire cathode and plate anode thereby destroying the ability of the ESP to charge particulates. 

The importance of membrane surface characteristics on performance is illustrated by Figure 6.15. The feed solution in this example was a cathodic electrocoat paint solution in which the paint particulates had a net positive charge. As a result, membrane flux declined rapidly with the positively charged membranes but much more slowly with essentially identical membranes that had been treated to give the surface a net negative charge [13]. 

Some commonly used batteries are shown in Table 15.5, and two are drawn schematically in Fig. 15.10. From these it can be seen that important components are the container, the anode/cathode compartment separators, current collectors to transport current from the electrode material (usually a porous, particulate paste), the electrode material itself, and the electrolyte. It should be noted that the electrode reactions can be significantly more complex than those indicated in Table 15.5, and there will probably be parallel reactions. By stacking the batteries in series, any multiple of the cell potential can be obtained. 

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