Rotating Cylinder Electrodes

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. 

Walsh FC, The role of the rotating cylinder electrode reactor in metal ion removal in ref (23), p 101, and references therein... 

Robinson D, Walsh FC (1991) The performance of a 500 Amp rotating cylinder electrode reactor, Part 1. Current-potential data and single pass studies, Hydrometallurgy 26 93 Chem Abstr 114 (1991) 194767w... 

Rotating cylinder electrode cell High High Small... 

The rotating cylinder electrode (Fig. 8) is operated in the turbulent flow regime at Re > 200, although flow can be complicated with vortexing until much higher Re, where tme turbulence develops (4). A Re number >200 is readily achieved at modest rotation rates and cylinder diameters. Therefore the cylinder can be... 

Figure 8 The rotating cylinder electrode, (a) Electrode specimen and mandrel shown as partially disassembled, (b) Typical laboratory setup for the RDE. (From Ref. 3.)...

A. Current and Potential Distributions for the Rotating Cylinder Electrode... 

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 ... 

Recently, Prein and Molander [54], also using a rotating-cylinder electrode, explored the effect of flow velocity (i.e., rotational velocity) on the ECP of Type 304SS in oxygenated water at 288 °C. These workers found that the ECP at low oxygen concentrations is quite sensitive to flow rate, and their data are in semiquantitative agreement with the MPM. 

Reynolds number 134 Rotating cylinder electrode Ruthenium(II) chelates 44... 

Figure 11.12 Schematic representation of a rotating cylinder electrode a) entire cylinder used as working electrode. This geometry provides a uniform current and potential distribution at and below the mass-transfer-limited current, b) band-shape cylindrical coupon used as a working electrode. This geometry is useful for studies conducted at the open-circuit condition.

D. R. Gabe, G. D. Wilcox, J. Gonzalez-Garcia, and R C. Walsh, "The Rotating Cylinder Electrode Its Continued Development and Application," Journal of Applied Electrochemistry, 28 (1998) 759-780. 

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... 

---