Static electrode reactors

Figure 1. Schematic diagram of the static plasma grafting device. Key 1, glass reactor 2, copper electrodes connected to HF generator 3, device for polymer sustaining 4, fabrics to be treated 5, outlet to vacuum pump 6, gas supply 7, outlet to vacuum gauge.

Following Goodridge [29], Walsh has classified reactors according to the electrode structure motion [4, 8, 17]. In the present case, the cathode may be static or moving with 2- or 3-dimensional character as a subdivision (table 4) and typical cell designs suggested by this classification have been considered elsewhere [4, 5, 8, 17, 20]. 

In many cases of metal-ion removal, there is a need to maintain a very high fractional conversion in a continuous flow-through reactor. This situation may be accomodated via a number of reactors in series flow both CSTR s [36, 37] and PFR s [45] have been considered. The important requirement of design simplicity often dictates the use of a static cathode geometry incorporating porous, 3-dimensional electrode materials [46], One example is reticulated vitreous carbon which has been extensively investigated in our laboratories [45-49] and elsewhere, e.g. [50, 51]. 

Electrochemical reactors can be operated under conditions of constant electrode potential, constant current, or constant cell voltage. The first two are referred to as potentiostatic and galvanostatic modes of operation, respectively. The potenti-static method is characterized by constant values of the kinetic parameters and hence enables integration of the dififerential equations describing the different reactors. On the other hand, galvanostatic operation is characterized by an inevitable change of electrode potential with time, leading to variations in the kinetic parameters. Hence we restrict our treatment to potentiostatic operation. 

There is vast literature detailing the use of different electrochemical reactors used for metal removal [2, 6]. The main types of electrochemical reactors can be classified first according to the kind of electrode as two or three-dimensional. The second classification considers the movement of the electroactive material with relation to a fixed referential. Thus the electrodes can be classified as static or mobile. Figure 1 shows the major electrode classifications according to geometry and fluid dynamics [1]. 

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