Electrocoagulation electrodes

It is recommended that PVP-I not be used on young children (neonates and babies) (Wissenschaftlicher 1980). Iodide, which is spoiled per operationem between skin and electrocoagulation electrodes, could result in serious burning wounds. Patch-test concentrations are as is and 10% pet. Allergic reactions are considered rare. 

Sengil, I.A. and Ozacar, M., Treatment of dairy wastewaters by electrocoagulation using mild steel electrodes, Journal of Hazardous Materials, 137 (2), 1197-1205, 2006. 

Micro-Thromboses Platelets and leucocytes, like other cells, are known to carry surplus negative charge, and can be electrophoretically deposited at (or around) the anode10 owing to the positive electrode potential. These microthromboses in capillaries in or near the treatment site will result in decreased blood flow and may contribute to a local dystrophy of the tissue. A more pronounced version of this effect can be seen sometimes as electrocoagulation and vascular occlusion (i.e., shut, closed or obstructed vasculature) of the tumor tissue. In other words, ECT cuts off the blood supply to the tumor and causes the tumor cell necrosis. 

Electrochemical technique (also electrocoagulation) is a simple and efficient method for the treatment of drinkable water. Recent results reported by Part-hasarathy and Yang [54,55] have demonstrated that electrocoagulation (EC) using aluminium anodes is effective in defluoridation. In the EC cell, the aluminium electrodes sacrifice themselves to form aluminium ions first. Afterwards the aluminium ions are transformed into AI(OH)3 before being polymerized to Aln(OH)3n. The AI(OH)3 floe is believed to adsorb F strongly as illustrated by the equation. 

N. Mameri, A.R. Yeddou, H. Lounci, D. Belhocine, H. Grib, B. Bariou, Defluoridation of septentrional Sahara water of North Africa by electrocoagulation process using bipolar aluminium electrodes, Water Res. 32 (5) (1998) 1604—1612. 

Based on these fundamentals, many systems and apparatus have been built, being operative on an industrial scale. Different types of reactors have also been designed. The electrodes may be parallel plates [162, 163] or sacrificial Al pellets as anode [164,165]. The feeding of pressurized air has been implemented in many electrocoagulation-electroflotation systems [159,166-168]. Some plants have a press to remove water from the sludge [169,170] and a processing tank with a closed S-shaped one-way flow path [171]. 

Figure 24 Diagram of the electrocoagulation process using soluble anodes. Several couples of electrodes, connected in parallel, can be used in the tank. (From Ref. 162.)... 

Fig. 4.1 Profiles of concentration in a single flow-cell with parallel plane electrodes (a) COD during electrooxidation (b) Aluminum during electrocoagulation...

In a bipolar arrangement, the sacrificial electrodes are placed between the two parallel electrodes without any electrical connection. The two monopolar electrodes are connected to the electric power source with no interconnections between the sacrificial electrodes. This cell arrangement provides a simple setup, which facilitates easy maintenance. When an electric current is passed through the two electrodes, the neutral sides of the conductive plate will be transformed to charged sides, which have opposite charge compared with the parallel side beside it. The sacrificial electrodes are known as bipolar electrodes. It has been reported that EC cell with monopolar electrodes in series connection was more effective where aluminum electrodes were used as sacrificial and iron was used as anode and cathode. And, electrocoagulation with Fe/Al (anode/cathode) was more effective for the treatment process than Fe/Fe electrode pair (Modirshahla et al. 2007). 

Apart from a technical focus on quantifying interactions between the foundation technologies and an economic focus on the relative cost of electrocoagulation, future research also needs to examine reliable means of reducing electrode passivation. 

EC is a simple, efficient, and promising method to remove arsenic form water. Arsenic removal efficiencies with different electrode materials follow the sequence iron > titanium > aluminum. The process was able to remove more than 99% of arsenic from an As-contaminated water and met the drinking water standard of 10p,gL 1 with iron electrode. Compared with the iron electrodes, aluminum electrodes obtained lower removal efficiency. The plausible reason for less arsenic removal by aluminum in comparison to iron could be that the adsorption capacity of hydrous aluminum oxide for As(III) is much lower in comparison to hydrous ferric oxides. Comparative evaluation of As(III) and As(V) removal by chemical coagulation (with ferric chloride) and electrocoagulation has been done. The comparison revealed that EC has better removal efficiency for As(ni), whereas As(V) removal by both processes was nearly same (Kumar et al. 2004). 

It is generally believed that there are three possible mechanisms involved in the process electrocoagulation, electroflotation, and electrooxidation. However, it can be suggested that, during the bipolar EC-EF process, bipolar aluminum electrodes are mainly responsible for electrocoagulation. 

Daneshvar, N., Sorkhabi, H.A., Kasiri, M. (2004). Decolorization of dye solution containing Acid Red 14 by electrocoagulation with a comparative investigation of different electrode connections. J. Hazard. Mater. 112, 55-62. 

Golder, A.K., Samanta, A.N., Ray, S. (2007). Removal of Cr31 by electrocoagulation with multiple electrodes biopolar and monopolar configurations. J. Hazard. Mater. 141, 653-661. 

Gomes, J.A.G., Daida, P., Kesmez, M., Weir, M., Moreno, H., Parga, J.R., Irwin, G., McWhin-ney, H., Grady, T., Peterson, E., Cocke, D.L. (2007). Arsenic removal by electrocoagulation using combined Al-Fe electrode system and characterization of products, J Hazard Mater. 139, 220-231. 

Modirshahla, N., Behnajady, M.S., Kooshaiian, S. (2007). Investigation of the effect of different electrode connections on the removal efficiency of tartrazine from aqueous solutions by electrocoagulation. Dyes Pigm. 74, 249-257. 

Mollah, M., Pathak, S., Patil, P., Vayuvegula, M. (2004). Treatment of orange II azo-dye by electrocoagulation (EC) technique in a continuous flow cell using sacrificial iron electrodes. J. Hazard. Mater. 109, 165-171. 

Yildiz, Y.S., Koparal, A.S., Irdemez, S., Keskinler, B. (2007). Electrocoagulation of synthetically prepared waters containing high concentration of NOM using iron cast electrodes. J. Hazard. Mater. B139, 373-380. 

The electrocoagulation process is characterized by a rapid rate of pollutant removal, compact size of equipment, simplicity in operation, and low capital and operational costs. Moreover, it is particularly more effective in treating oily waste due to accompanying of electroflotation effect. The waste stream of this process requires sufficient conductivity for cell operation and to prevent passivation of the electrode material. 

For technical applications, electrocoagulators are used to charge the solids in contaminated liquid effluents. Metal hydroxides are produced by a system of soluble electrodes (anodes) which, in suitable electrolytes, cause coagulation of particles into larger floes. 

Electrocoagulation Coagulation induced by exposing a dispersion to an alternating electric field gradient between two sacrificial metal electrodes. Electrocoagulation is apparently due to a combination of the alternating electric field and the adsorption on dispersed particles, or droplets, of ions solubilized from the electrodes. See also reference 17. 

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