Swiss roll

Spiral-wound modules consist of several flat membranes separated by turbulence-promoting mesh separators and formed into a Swiss roll (Figure 16.18). The edges of the membranes are sealed to each other and to a central perforated tube. This produces a cylindrical module which can be installed within a pressure tube. The process feed enters at one end of the pressure tube and encounters a number of narrow, parallel feed channels formed between adjacent sheets of membrane. Permeate spirals roward the perforated central tube for collection. A standard size spiral-wound module has a diameter of about 0.1m, a length of about 0.9 m and contains about 5 m2 of membrane area. Up to six such modules may be installed in series in a single pressure tube. These modules make better use of space than tubular or flat sheet types, but they are rather prone to fouling and difficult to clean. 

The cell used (Fig. 16) is an undivided, so called Swiss-roll cell (Figs. 16 and 17) with a Ni mesh anode and a steel cathode. 

Fig. 16. Swiss roll electrolysis cell [198] (1) separator (2) anode sheet (3) cathode sheet...

Fig. 17. Schematic diagram of the flow system used for batch and continuous oxidation of DAS (Diacetone-L-sorbose) with a swiss roll cell with an anode area of 3 m2...

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. 

To overcome such hurdles, special devices have been proposed and tested, which are based on internal heat recovery of waste heat through the adoption of Swiss roll geometries, such as those reported in Figure 12.7 [52]. 

For laboratory scale conversions a simple beaker-type cell (Fig. 1) is convenient When lower current densities have to be applied or in big scale operations 21,26) the Swiss-roll cell is of advantage. The latter cell (Fig. 2) contains a rolled-up sandwich, consisting of an anode and cathode sheet and a separator net. This allows a high electrode area applied in a small cell volume, which results in the low current densities necessary for efficient electrolyses at the nickel hydroxide electrode. 

Fig. 2 Swiss-roll -cell, arrangement of the electrodes 1 Steel net cathode 2,4 Polypropylene net as insulating separator 3 Nickel net anode 5 Current feeder...

The Swiss-roll cell is commercially available from Dr. Robertson, P. M., Haldenstr. 9, 8185 Winkel, Switzerland... 

The heterogeneously catalyzed Mn02-mediated oxidation of diacetone-L sorbose to diacetone-2keto-L sorbic acid, the latter being a precursor to vitamin C, at nickel anodes and based on the chemical oxidation of the substrate by NiOOH is of technical relevance. The limiting current density in 1 M KOH solution is under operation conditions only 10 A/cm2 leading to relatively poor space-time yields. Robertson and Ibl showed that acceptable space-time yields can by obtained by using thin layer cells of Swiss roll type (193, 194), which leads to an efficient compression of the cell width to fractions of a millimeter. 

A special construction, called Swiss-Roll cell [13] (Fig. 22.12), is used for the application of the NiOOH electrode in the oxidation of primary alcohols to carboxylic acids. 

Figure 22.12 Swiss-Roll cell for the applications of NiOOH electrodes (1 = steel net cathode 2 + 4 = polypropylene net 3 = nickel net anode 5 = current feeder).

Mercury represents a serious environmental risk, and the study of removal of mercury from wastewater has received considerable attention in recent years. Mercury concentration was usually reduced by deposition on a cathode with high surface area. Removal of mercury is studied using extended surface electrolysis which reduces the level of mercury to below acceptable concentrations of 0.01 ppm in wastes by employing a Swiss roll cell with a cadmium-coated, stainless-steel cathode. An industrial cell with a fluidized bed electrode has also been studied. Graphite, as an efficient porous electrode, has been used to remove traces of mercuric ions form aqueous electrolyte solutions. In order to apply the electrochemical method for some effluents, it is necessary to use sodium hypochlorite to convert elemental mercury and less soluble mercury compounds to water-soluble mercuric-chloride complex ions. 

For cells that lack IR loss-increasing membranes, the Swiss-roll cell design (Ibl, 1975) may be the answer. Two metal foils act as electrodes and are separated by two insulating plastic masks that act as turbulence promoters. This cell gives large area and low IR. It is shown in Fig. 11.6. 

Fig. 11.6. Swiss-roll cell. (Reprinted from G. Kreysa, in Ulmann s Encyclopedia of Industrial Chemistry, Vol. 49, p. 200,1985, with permission from Wiley-VCH.)...

Swiss-roll cell — This cell was developed in Switzerland in 1982, and it is used on industrial-scale in case of the NiOOH electrode for the oxidation of primary alcohols to carboxylic acids, as, e.g., in vitamin C production. The electrolyte solution flows axially through the cell (see Figure), which is made up of rolled meshes of the nickel net anode and steel net cathode, separated from each other by polypropylene spacers, around the central current feeder rod. 

Scheme 13. High pressure-promoted cycloaddition between the. syn-bisdienophile 38 and the. vy/i-bisdienc 57 has afforded [21, 132] three fully characterized products, 59, 60, and 61. The 2 1 adduct 59, with syn/entlo-H stereochemistry across both of the newly-formed cyclohexenc rings, is the major component of the reaction mixture. However, a minor 2 1 isomer 61, which has antijendo-H stereochemistry across one of the newly-formed cyclohexene rings, has also been characterized. The conformation adopted by the 3 2 adduct 60 is of considerable interest. H NMR Spectroscopy suggests that the terminal dienophilic units may overlap with each other to afford a Swiss-roll -like conformation...

Cells with three-dimensional electrodes have bipolar electrodes such electrodes are characterized by the feature that one part of the electrode is anode and another part cathode. This can be realized in different ways, such as the pile capillary gap cell (Beck/Guthke cell. Chapter 32) [9,80], the Swiss roll cell [81], and packed- and fluidized-bell cells (Chapter 32) [82-84]. These cells are developed to meet economic demands, such as high space-time yield and simplicity in construction they are discussed in Chapter 31. 

A nickel anode is in alkaline solution protected against corrosion by a layer of nickel oxides. oxide (NiOOH) is capable of oxidizing a number of functional groups primary alcohols may be oxidized to carboxylic acids [158-161], which is of interest for the technical production of an intermediate for vitamin C production [162]. NiOOH chemically oxidizes the substrate and is regenerated electrochemically a large anode surface, which is realized in the Swiss-roll cell (Chap. 31), is thus advantageous. NiOOH electrodes in form of nickel foam electrodes has been found to be useful for the oxidation of diacetone L-sorbose to diacetone 2-keto-L-gulonic acid in the vitamin C synthesis [163]. 

Swiss-roll cell for NiOOH oxidations (Hoffman-La Roche). 

Figure 19. Swiss-roll cell arrangement of the electrodes.

The Swiss-Roll cell with a sandwich construction made from a pair of thin, flexible electrodes, wound with the interposition of a pair of separators for electrical insulation. The cell performance is achieved mainly by high electroactive area. The cathode product is removed by replacing the electrode module. 

The three dimensional form can be best visualised as a swiss roll, where jam represents the water and the sponge is the lipid layer with the polar head interacting with the water. These structures are important in the stabilisation of doughs and batters and in particular in promoting foam stabilisation at the air / water interface. 

Swiss-roll cell This cell, shown in Figure 26.14, has been proposed for both electro-organic syntheses and wastewater treatment [29, 37, 38]. It is fabricated from a multilayer stack of the following sheet materials (a) a polymeric cathode spacer cloth or mesh, (b) a cathode mesh, (c) an ion-exchange membrane, (d) a polymeric anode spacer cloth or mesh, and (e) an anode mesh. These sheets are assembled in the sequence a-b-a-c-de-d-... 

FIGURE 26.14 The Swiss-roll cell [30] (with kind permission from Springer Science and Business Media). 

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