Electrochemical degradation pathways

Electrochemical destruction of organics can be an economically viable alternative to incineration, carbon beds, bioremediation, deep well disposal and other methods as destruction to very low acceptable levels is possible [227a], Electrochemical techniques are in fact superior to incineration or deep well disposal as it is a final solution and not a transfer of a toxic material from one environment to another, e.g. to the groundwater or the atmosphere [285], Common destruction pathways include both direct and indirect electrolysis. Many electrochemical degradation pathways remain unclear and may be a mixture of direct and indirect processes depending on the pollutant and its intermediates [84,285a]. 

In the case of the thiopurines the electrochemical processes do not appear to agree at all with the known biological oxidations. However, again in the case of 6-thiopurine not even a complete picture of the metabolites is available. The electrochemical data indicates that thiopurines are very readily oxidized to disulfides and hence to sulfinic or sulfonic acids. In view of well-known sulfide-disulfide transformations in biological situations (e.g., L-cy-steine to L-cystine), it is not unlikely that part of the metabolic degradation pathway for thiopurines might proceed via reactions of the sulfide moiety. 

Reaction Pathway of Electrochemical Degradation of Phenol on Ti/Sn02-Sb Electrodes... 

Ultrasound plays a role in either the chemical degradation pathway or the electrochemical reaction at the electrode based on the frequency used. The increase extent is closely related with the electrode material. It seems that further investigation of the geometry of both electrodes and reactor is needed in order to optimize the ultrasound energy distribution, enhance the degradation efficiency, and reduce the energy consumption. 

Attempts to form surface-confined poly(aniline) have previously been made using 4-aminothiophenol on Au. After oxidation of the monolayer and successive potential scans, this monolayer was found to produce a surface-confined redox active film. Recently, elucidation of the coupling and degradation pathways of this molecule on Au was reported. Radical-radical coupling was found to occur between adjacent aminothiophenol molecules yielding an electrode surface modified with 4 -mercapto-4-aminodiphenylamine. Upon potential scanning of the surface-confined aniline dimer, an electrochemical-chemical-electrochemical (ECE) reaction was found to occur. Oxidation of the quinonediimine resulted in hydrolysis of the dimer to yield a quinone monoimine species. Further oxidation of this molecule then produced the initial 4-aminothiophenol molecule as well as benzoquinone in solution. 

The electrochemical oxidation pathway of tubercidin-5 -monophosphate (TMP) is of interest because TMP, a structural analog of adenosine, is not degraded by enzymes of purine metabolism . It was, therefore, anticipated that the redox rectivity of this compound should reflect its deazapurine structure and should provide considerable insight into structure-reactivity relations of purine derivatives. 

Corrosion is classified, according to the medium that the metal or alloy is exposed to (Table 14.1), as wet and dry corrosion. Corrosion of metals immersed in an aqueous medium is an example of wet corrosion, which proceeds electrochemically. Atmospheric corrosion also belongs to the class of wet corrosion, since it is caused by moisture deposited on the metal surface. Another division of wet corrosion is the degradation of metals and alloys in nonaqueous media by chemical pathways. 

A model developed by Bell Labs researchers (Ref 22) in the late 1970s (Ref 23) details the mechanism by which CAR formation and growth occurs. The first step is a physical degradation of the glass/epoxy bond. Moisture absorption then creates an aqueous medium along the separated glass/epoxy interface that provides an electrochemical pathway and facilitates the transport of corrosion products. 

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