Electrolyte streaming

Nagel, V. Gilmore, M. Scott, S. Bateman pulsed column pilot-plant campaign to extract cobalt from the nickel electrolyte stream at Anglo Platinum s base metal refinery. International Solvent Extraction Conference, Cape Town, South Africa, Mar. 17-21, 2002, pp 970-975. 

Swiss Roll Cell This cell has been developed in Switzerland [89]. A commercial application is one oxidation step at a NiOOH anode in alkaline solution for the vitamin C production [22]. Mesh electrodes of stainless steel (cathode 1) and nickel (anode 3) are rolled up together with spacers of polypropylene mesh (2,4) on the central current feeder (5) and mounted in a cylinder (cells up to 1 m diameter, 200 m active area). The electrolyte streams axially through the cell. 

Incidentally, the elemental copper formed by Eq. 13.21 is the chief source of the copper present in anode slimes. Electrolyte is continually recirculated through the electrolysis cells to minimize the buildup of impurities. When the copper content of the electrolyte reaches 40-50 g/L (from the initial 12-18 g/L), it must be purified before reuse. The concentrations of copper, arsenic, antimony, bismuth, and nickel must all be substantially decreased. A small portion (ca. 2-3% of the total volume, per day) of the electrolyte stream is continuously bled from the main electrolyte stream for this purpose. 

First, we have to consider a flow on a rough and porous electrode of length L (cm) and a cross-sectional area A (cm2) immersed in a torrent of electrolyte with a volumetric flow rate 9 (cm3 s ). The linear flow rate of the electrolyte stream, v (cm s 1), is given by... 

G. Nagy, Z. Feher, E. Pungor, Application of silicone rubber-based graphite electrodes for continuous flow measurements. 2. Voltammetric study of active substances injected into electrolyte streams, Anal. Chim. Acta 52 (1970) 47. 

Solid-phase microextraction (SPME) is a miniaturized variation of the SPE, based on the partitioning of the analytes between the sample matrix and the stationary phase, which is coated on a fused-silica fiber. SPME with CE has been applied in environmental analysis to determine PAHs in water, and pesticides in vegetables. Trapped analytes can be desorbed by an organic solvent or directly into the CE electrolyte stream, via an adapter. 

Since current leakage through an electrolyte depends on the existence of a continuous path, another technique for the prevention of leakage currents is the use of current breakers at the cells. Their purpose is to physically break the electrolyte stream in order to interrupt the electrical path. Figure 8.10 shows the design used with some diaphragm cells. The liquor from each cell is collected in a cup (C). The demister... 

The potentiometric technique for FIA monitoring has also been achieved by using ion-selective electrodes (ISEs - see subsection 2.1.1) assembled in a tubular reservoir (with the working electrode positioned at different points in the system). The use of a series of cascading ion-selective electrodes allows the simultaneous determination of various species [342]. To minimize the thickness of the static layer on the electrode surface and achieve an optimum wash-out effect preventing changes at the sensor membrane it is customary to use cascade-type cells in which a small portion of the carrier electrolyte stream is pumped tangentially to the electrode surface [343]. 

Fig. 4.2 Schematic of an air-breathing microfluidic fuel cell with F-shaped microchannel. The cathode is designed to capture oxygen from the ambient air using a gas diffusion electrode in contact with a blank electrolyte stream on the opposite side. Reprinted with permission from Jayashree et aL [29]. Copyright 2005 American Chemiceil Society...

Figure 9.5 Membraneless LFFCs with air-breathing cathodes, (a) Schematic illustration for the arrangement of fuel and electrolyte streams in the channel. Adapted from Ref. [32]. (b) Cross section and carrier...

This approach to on-line matrix separation/preconcentration is based on passing an electrolyte stream through an anodic stripping voltanunetry (ASV) cell and injecting the sample into this stream. When the ASV cell is set at an appropriate potential, the analyte is preferentially deposited... 

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