Diaphragm oxidation

For forced-convection studies, the cathodic reaction of copper deposition has been largely supplanted by the cathodic reduction of ferricyanide at a nickel or platinum surface. An alkaline-supported equimolar mixture of ferri- and ferrocyanide is normally used. If the anolyte and the catholyte in the electrochemical cell are not separated by a diaphragm, oxidation of ferrocyanide at the anode compensates for cathodic depletion of ferricyanide.3... 

Electrochemical Generation of Chlorine Dioxide from Chlorite. The electrochemical oxidation of sodium chlorite is an old, but not weU-known method of generating chlorine dioxide. Concentrated aqueous sodium chlorite, with or without added conductive salts, is oxidized at the anode of an electrolytic cell having a porous diaphragm-type separator between the anode and cathode compartments (122—127). The anodic reaction is... 

Diaphrag m Cell Technology. Diaphragm cells feature a porous diaphragm that separates anode and cathode compartments of the cell. Diaphragms should provide resistance to Hquid flow, requite minimum space between anode and cathode, produce minimum electrical resistance, and be durable. At the anode, which is generally a DSA, chloride ions are oxidized to chlorine (see eq. 1) and at the cathode, which is usually a woven steel wine mesh, water is reduced to hydrogen. 

In a review of incidents involving explosive reactivity of liquid chlorine with various organic auxiliary materials, two involved hydrocarbons. A polypropylene filter element fabricated with zinc oxide filler reacted explosively, rupturing the steel case previously tested to over 300 bar. Zinc chloride derived from the oxide may have initiated the runaway reaction. Hydrocarbon-based diaphragm pump oils or metal-drawing waxes were violently or explosively reactive [8], A violent explosion in a wax chlorination plant may have involved unplanned contact of liquid chlorine with wax or chlorinated wax residues in a steel trap. Corrosion products in the trap may have catalysed the runaway reaction, but hydrogen (also liberated by corrosion in the trap) may also have been involved [9],... 

It is commercially advantageous to operate cells with no diaphragm since the cell diaphiagm is the weakest point in the system. Achievement of this aim rests upon finding an anode reaction that destroys neither the substrate nor the product. Russian workers [63] showed that up to 90 % yields of adiponitrile can be obtained at a graphite cathode in an undivided cell with an iron oxide anode, provided that phosphate and tetraalkylammomum ions are present. Further research contributions from Monsanto, BASF and Japanese companies led to the present system for hydrodimerization of acrylonitrile using an undivided cell [64,65]. 

Alternatively, low-grade stibnite ore is converted to its oxide which is then reduced with carbon. Tetrahedrite may be treated with sodium sulfide solution. The solution containing thioantimonate formed is then electrolyzed in a diaphragm cell using a steel cathode and lead anode. The metal is further refined by oxidation or electrorefining process. 

Sensors Di 200 and Di 2000 with aiuminum oxide diaphragms, which are particuiariy overioad-free, with the MEMBRANOVAC DM 11 and DM 12 units. 

Since the products of the electrolysis of aqueous NaCl will react if they come in contact with each other, an essential feature of any chloralkali cell is separation of the anode reaction (where chloride ion is oxidized to chlorine) from the cathode reaction (in which OH- and H2 are the end products). The principal types of chloralkali cells currently in use are the diaphragm (or membrane) cell and the mercury cell. 

Figure 19.11—Karl Fischer coulometric cell, model DL-37. The diaphragm (membrane) is used 10 avoid oxidation ot the reduced ions created at the surface of the cathode. (Reproduced by permission of Mettler Toledo.)...

The interior of the furnace was lined with platinum foil to limit any reaction of the oxide vapors with the alumina furnace walls. Three perforated platinum foil diaphragms were placed at intervals inside the furnace to act as heat shields and to ensure thorough mixing of the oxide vapor-air mixtures. 

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