DSA electrode

The invention of the ruthenium based DSA electrode by H.B. Beer has had a major impact on the chlorine industry and has stimulated a number of investigations aimed... 

XPS has been used by several authors to identify the surface and bulk composition of ruthenium based, valve metal stabilized DSA electrodes for chlorine evolution. Augustynski et al. [45] investigated the composition of Ru02-Ti02 electrodes before and after electrochemical treatment. They found a surface composition which deviated significantly from that of the bulk. The Ru/Ti ratio corresponded to 0.15 at the surface while in the bulk 0.28 was measured. Similar results were obtained by De Battisti et al. [46] for Ru02-Ti02 electrodes with different composition ratios on Ti substrates. Fig. 10 shows the Ru/Ti ratio for different solution compositions as a function of the depth. 

The key role of RuOa for the electrochemical stability of Ru02 based DSA electrodes for Cl2 evolution was also pointed out by Augustynski et al. [45] on the basis of XPS data. After electrolysis in NaCl solution Augustynski found Cl species on the surface of the DSA electrode and a higher Ru oxide species, most probably Ru03. 

Catanho, M Malpass, GRP Motheo AJ. Photoelectrochemical treatment of the dye reactive red 198 using DSA electrodes. Applied Catalysis B Environmental, 2006 62, 193-200. 

Environmental and Safety f actors. The primary environmental concern for the coaling plant is actually the residual material on the anode structures being returned for recoating. Therefore the anode user must enact effective cleaning procedures prior to shipment. Overall, the DSA [Electrode Corp.) has made chlorine manufacture cleaner, more consistent, simpler, and therefore safer. 

The history of the development of the DSA electrodes is a classic of its kind. The original inventor, Henri Beer, was of the traditional type his work started in a small private laboratory. The first offerof the rights to his invention was made by a large British chemical concern for 25,000. Successful patenting was concerned with the help of deNora of Milan, Italy. World patents have been taken out by Diamond Shamrock of the United States. 

Malpass, G. R. P., Neves, R. S. and Motheo, A. J. (2006) A comparative study of commercial and laboratory-made Ti/Ruo.iTio.yOj DSA electrodes In situ and ex situ surface characterisation and organic oxidation activity. Electrochim. Acta 52, 936-944. 

To achieve a catalytic layer on base materials is the core process for DSA-electrode fabrication. To ensure the layer stability, it is important to try to make the layer better adhesion with the base surface. We have tried several methods in the electrode preparation, including pretreatment, pyrolysis technologies, and electrodeposition. Till now, our research revealed that the electrode service life and the behaviors have been influenced by the electrode preparation methods and technological factors. 

For organic compounds degradation, Ti-base Sn02 electrodes showed better behaviors than any other DSA electrodes, especially for the nanostructure. 

Owing to the success of Ru02-based DSA electrodes in the chlor-alkali industry, a significant amount of study has been carried out on the kinetics and mechanism of chlorine evolution at Ru02-based electrodes over the past 15 years or so. A considerable body of experimental data has therefore been accumulated regarding the chlorine evolution reaction at Ru02 electrodes, which includes E vs. log j plots, reaction order determinations, pH depen-... 

This can sometimes be circumvented by using DSA electrodes, but care must be taken to avoid poisoning of the cathode as a result of traces of metals migrating from the anode to the cathode. Some of these problems are discussed in more detail in Ref. 88. 

As shown by the volcano plots of Figs 25 and 39 [139], Pt and Pt-Ru alloys are among the most active electrocatalysts for the oxygen evolution reaction. However, Ru02, which is also the main component of dimensionally stable anode (DSA) electrodes, is significantly more active (Fig. 25). 

R.C. Carlson, The Effect of Brine Impurities on DSA Electrodes, 14th Annual Chlorine/Chlorate Seminar, ELTECH Systems Corp., Cleveland,OH (1998). 

As described earlier, the DSA electrode is typically a valve metal substrate coated with a noble-metal-based composition. Either to circumvent the basic Beer patents or to achieve better and less expensive anode compositions, considerable efforts have been devoted to the development of novel anode coatings. A wide variety of compositions [14] have been described in the literature, and it is beyond the scope of this chapter to review these developments individually. A generalized formulation of anode materials can be schematically described as Sub/VM - - NM + NNM, where Sub refers to the substrate, VM to the valve metal, NM to the noble metal, and NNM to the non-noble metal. The compositions cited in the literature include the following in various combinations ... 

Bromide. Most salts contain small quantities of bromide. There are no documented effects of bromide on membranes, but it can adversely affect DSA electrodes. The bromine formed by electrolysis also will affect the quality of the chlorine produced. When the bromine content of the chlorine gas becomes too high, there is a need to remove it in some form somewhere in the process. 

The rate of oxygen evolution is lower at high NaCl concentrations. However, recycling the electrolytic solution to the undivided cell is cumbersome, and so the utilization of NaCl decreases. Modem processes use relatively dilute NaCl solutions to improve the utilization of the salt. Many electrolyzers use platinized titanium or DSA electrodes. Operation at high current densities increase the yield because the rates of the loss reactions (24) and (25) are independent of current density. Finally, agitation of the solution promotes undesirable mass transport of OCl to the electrodes. 

Platinum anodes have a limited operational range of oxidation potentials and thus attention has focused on Sn02-coated titanium materials. The tin oxide material, when doped with Sb (approximately 5%) to impart the appropriate electrical conductivity, has oxygen overpotentials some 600 mV greater than those of platinum. Tin oxide gives higher oxidation efficiencies to those of platinum, lead dioxide, ruthenium and iridium oxide (DSA) electrodes and is reported to be stable to corrosion during anodic oxidation. 

Zhou M et al (2011) Treatment of high-salinity reverse osmosis concentrate by electrochemical oxidation on BDD and DSA electrodes. Desalination 277(l-3) 201-206... 

Organic Pollutants in Water Using DSA Electrodes, In-Cell Mediated (via Active Chlorine) Electrochemical Oxidation... 

---