Electrochemical Reduction Unit

A patented electrochemical unit that uses sacrificial iron electrodes to generate the ferrous ion is effective in removing hexavalent chromium as well as other heavy metals. In the electrochemical cell, a direct current is conducted through the cell containing a number of carbon steel plate electrodes. This generates the ferrous ion (Fe ) and hydroxyl ion (OH ). The ferrous ion reduces hexavalent chromium to the trivalent state as follows  

Metals other than chromium are removed through a process of adsorption and coprecipitation within insoluble ferrous ion matrix that is formed from the electrodes.38 Since the ferrous ion is a good chelate breaker, the electrochemical unit is also applicable for removal of complexed metals. 

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It has recently been reported that a molecule, claimed to contain a high concentration of conjugated alkyne units, can be prepared by electrochemical reduction of polytetrafluoroethylene (PTFE) [32,33]. The reduction is carried out using magnesium and stainless steel as anode and cathode respectively. The electrolyte solution contains THE (.30 cm ), LiCI (0.8 g) and FeCl2 (0.48 g). A 10 X 10 nm PTFE film, covered with solvent, is reduced to carbyne (10 V for 10 h)... 

Potentially coordinatively unsaturated dithiolene-metal complexes are rare,298-306 and 1 1 dithiolene-transition-metal complexes with no other ligands are, to our knowledge, unprecedented.307 The neutral complex [PdS2C2(COOMe)2]6,308 is homoleptic containing one dithiolene unit for each palladium atom and no other ligands. Electrochemical reduction of the compound depicted in Figue 21 proceeds in four reversible steps. 

Dications 222+ and 232+ were synthesized by hydride abstraction reaction of the corresponding hydro derivatives as stable dark-brown powder. The p/CR+ values for these dications are also extremely high for doubly-charged systems (222+ 11.7 and 232+ 11.7). The electrochemical reduction of 222+ and 232+ exhibited a reduction wave at less negative potentials than that of dication 212+. This wave corresponds to the reduction of two cation units by a one-step, two-electron reduction to form thienoquinoid products. Chemical reduction of 222+ and 232+ afforded the closed-shell thienoquinoid compounds (22 and 23), which exhibited high electron-donating ability. The formation of the closed-shell molecules is in contrast with the result from reduction of dication 212+connected via a / -phenylenediyl spacer. 

The electrochemical reduction of monocation 27 exhibited a reversible wave at -0.70 V upon CV due to the formation of a neutral radical. Although the p R values decrease by increasing the cationic units, the reduction potentials for the tetra- and dications (254 and 262 ) are almost equal to that of 27. The CV waves of 254 and 262 exhibit more current, as compared with that of 27 at the same concentration. Therefore, the first reduction wave of 254+ and 262 is... 

We have therefore been able to prepare the highly stable tetracation 254+ salt despite the presence of four positive charges in the structure. However, this first example for a cyanine-cyanine hybrid with cyanine units at both two termini did not demonstrate the presumed multiple color changes during electrochemical reduction. However, the tetracation 254+ exhibited multiple-electron transfer as a function of the substituted di(l-azulenyl)methylium units and also showed color change during the electrochemical reduction. 

The tetracation 312+ exhibited the idealized electrochemical behavior upon CV and DPV, although the redox interaction among the cation units was still small. Additionally, tetracation 314+, synthesized as a representative for the cyanine-cyanine hybrid, also did not exhibit the presumed multiple-color change during electrochemical reduction. 

The electronic properties of n-conjugated polymers reflect well the basic electron-withdrawing or electron-donating properties of the components of the Ti-conjugated polymer [62]. In view of the electrochemical reduction potential, the thiophene unit and tetrathiafulvalene unit (Nos. 8 and 9 in Table 1) have a similar electronic effect in PAEs. It is reported that poly(arylenevinylene)s are also susceptible to electrochemical reduction [63, 64]. Due to the electron-accepting properties, PAEs are usually inert in electrochemical and chemical (e.g.,by I2 [54]) oxidation. 

The hydrodynamic voltammograms of picric acid and p-nitro-phenol depicted in Figure 12 illustrate the influence of mechanism on the detection process. If the detector potential is set at the potential on the plateau of the voltammogram of p-nitro-phenol, both compounds are detected. If the potential is set at the plateau of the first wave of picric acid, it alone is detected. At more negative potentials the unit response for the polynitroaromatic compounds will be greater than the response for mononitroaromatic compounds since more electrons are involved in the electrochemical reduction of polynitroaromatics. 

Mazur DJ, Weinberg NL. Methods for electrochemical reduction of halogenated organic compounds. United States Patent 4,702,804, 1987. 

The only example would appear to be Os(NO)dppe2, made by electrochemical reduction of [Os(NO)dppe2]+ (see below). It is dark brown and very air-sensitive, giving an ESR spectrum which seems to suggest that the unpaired electron is largely localized on the NO ligand. The very low vNO frequency of 1417 cm"1 suggests that it may contain a bent Os—N—O unit.243... 

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