Rotating cylinder cell

Similar cells based on cylindrical geometry have been proposed. In the stationary version, the electrolyte is pumped through a thin gap between two electrodes formed by the inside of a pipe and a concentric central cylinder. When the central electrode is rotated the cell is again self-pumping and the rotating cylinder cell has many of the attractions of the pump cell. It has been manufactured commercially for the removal of metal ions from dilute solutions. The cylinder cells have a poor space time yield compared with their disc counterparts but have the advantage that they may be modified to include a separator. 

Fig. 2.5 Elementary reactor geometries, (a) Parallel-plate cell, (b) Concentric rotating-cylinder cell, (c) Plate-in-tank cell, (d) Plate cell with non-parallel electrodes.

In the majority of cases, metal is removed from the cathode at intervals, usually by manual peeling or scrapping the deposit. A rotating-cylinder cell for photographic silver recovery is shown in Fig. 7.6. Such cells are available with rotating cathodes (small-scale) or rotating anodes (on a larger scale). 

Tank Cells. A direct extension of laboratory beaker cells is represented in the use of plate electrodes immersed into a lined, rectangular tank, which may be fitted with a cover for gas collection or vapor control. The tank cell, which is usually undivided, is used in batch or semibatch operations. The tank cell has the attraction of being both simple to design and usually inexpensive. However, it is not the most suitable for large-scale operation or where forced convection is needed. Rotating cylinders or rotating disks have been used to overcome mass-transfer problems in tank cells. An example for electroorganic synthesis is available (46). 

Figure 5 The Costar Transwell system with a cell monolayer grown on a porous polycarbonate filter that is mounted onto a removable plastic insert forming the apical chamber. Two other systems, (1) the Costar diffusion chamber system, where a filter-grown (Snap-well) cell monolayer is sandwiched between two chambers of equal volume and the bathing solutions are agitated and/or gassed and (2) filter-grown cell monolayers mounted in a two-chamber rotating cylinder device (Imanidis et al., 1996), are not shown.

Robinson and Walsh have reviewed earlier cell designs. The performance of a 500 A pilot plant reactor for copper ion removal is described. Simplified expressions were derived for mass transport both in single pass [243] and batch recirculation [244]. For a detailed discussion of the principle and the role of the rotating cylinder electrode reactor in metal ion removal the reader is referred to Refs. [13] and [241] (46 references). 

A typical 5 kA Eco cell has a cathode drum with a radius of 0.37 m, a height of 0.74 m and a cathode-membrane gap of about 1 cm. The cathode is rotated at 100-200 rev.min-1. In rotating-cylinder electrode cells, high fractional conversion can be obtained by employing an Eco cascade cell. 

Eco-cell (Originally Ecological Engineering Steetley Engineering Ltd) Outer surface of a rotating cylinder with powdered-metal deposit May be continuous via automatic scrapping and fluidization of metal powder Maybe V V... 

In this cell, the aqueous and the organic phase are brought in contact at the snrface of a microporous membrane filter, the pores of which are filled with the organic phase [20]. The microporous filter is attached to a hollow cylinder filled with the same organic phase. The cylinder is dipped into the aqueons phase and is rotated by a motor. A scheme of the rotating diffusion cell is presented in Fig. 5.12. The cell has a filter with well-defined hydrodynamics on both... 

Rotating cylinder electrode cell High High Small... 

Fig. 2. Schematic diagram of the centrifugal liquid membrane (CLM) apparatus. The glass cylinder cell (i.d. 19 mm) was rotated at a speed of 7000 10,000 rpm. Introduction of 50-200 pi of the organic and the aqueous phase generated a two-liquid layer with a thickness of 50-100 pm for each phase. Reagents can be injected from a small hole at the end side of the cell.

ECO cell — Electrochemical cell which is applied in wastewater treatment. A rotating cylinder employed as cathode and fixed anodes at the periphery are separated by a -> diaphragm. Small disks reaching from the separator up to close to the rotating cathode split the... 

Each of these techniques may be used with numerous cell designs. The design of cell will depend upon the characteristics of the system to be simulated. Commonly, the flow of electrolyte is important and must be known and in such cases, rotating-disc or ring-disc, flow-in-duct, or rotating-cylinder [36, 37] electrodes would be used. 

Using a rotating cylinder electrode is a good way to achieve high rates of mass transport. This is very different, however, from the RDE in that the flow is turbulent rather than laminar. As a result, it is not possible to derive theoretical equations that relate the rate of mass transport to the various parameters in the reaction, and one must resort to empirical correlations. These tend to be critically dependent on dimensions and on the specific configuration of the cell, hence are less reproducible. A typical equation for mass transport to a rotating inner cylinder of radius r is ... 

Fig. 11. Schematic of an electrochemical cell and gold rotating-cylinder anode (RCA) for the indirect destruction of chlorinated organics using Co(III).

High mass-transport coefficients are obtained in cells with a rotating cylinder electrode (RCE) and a small gap between the anode and the cathode, Fig. 4(a). High rates of mass transport are experienced in the turbulent flow regime, so that RCE reactors allow metal deposition at high speed, even from dilute solutions. RCE reactors have been operated at a scale involving diameters from 5 to 100 cm, with rotation speeds from 100 to 1500 rpm and currents from 1 A to 10 kA [79], It... 

Figure 11. Illustration of two alternative designs for the rotating cylinder Hull (RCH) cell, which allows the study of non-uniform current distribution on the cathode, under controlled mass-transport conditions. A anode, C cathode, IC insulating cylinder. Reproduced from Ref. 150 with kind permission of Springer Science and Business Media, and with permission from Ref. 95, Copyright (1996) The Electrochemical Society.

Electrode shown is Pt with Teflon (PTFE)-treated glass frit. [Reprinted from B. Bittins-Cattaneo, E. Cattaneo, P. Konigshoven, and W. Vielstich, Electroanal. Chem., 17, 181 (1991), by courtesy of Marcel Dekker, Inc.] Bottom left (c) Electrochemical cell with a rotating cylinder electrode and sampling with separate inlet to MS. [Reprinted from S. Wasmus, E. Cattaneo, and W. Vielstich, Electrochim. Acta., 35, 111 (1990), with permission from Elsevier Science.]... 

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