Current density additive effects

In addition to the influence of the electrode material and current density, the effect of additives on the bubble behavior and size has been investigated. Venczel25 added gelatin, glycerine, and beta-naphthochinolin to his electrolyte in most cases the bubble size decreased and in some cases a frothy mixture resulted. The... 

In addition to current density, additives, and the electrode itself, other process characteristics affect bubble size and behavior. Landolt et al29 found that the bubble size decreased with flow rate in the interelectrode area in fact, they achieved current densities much higher than those which in stagnant electrolyte would produce anode effect. Electrode orientation and configuration must also affect bubble size.30... 

For economical and complete cathodic protection against external corrosion without harmful effects on nearby installations, the storage tank to be protected must have good coating and therefore require a low protection current density. In addition, it must have no electrical contacts with other buried installations, such as... 

Because these variables have a very pronounced effect on the current density required to produce and also maintain passivity, it is necessary to know the exact operating conditions of the electrolyte before designing a system of anodic protection. In the paper and pulp industry a current of 4(KX) A was required for 3 min to passivate the steel surfaces after passivation with thiosulphates etc. in the black liquor the current was reduced to 2 7(X) A for 12 min and then only 600 A was necessary for the remainder of the process . From an economic aspect, it is normal, in the first instance, to consider anodically protecting a cheap metal or alloy, such as mild steel. If this is not satisfactory, the alloying of mild steel with a small percentage of a more passive metal, such as chromium, molybdenum or nickel, may decrease both the critical and passivation current densities to a sufficiently low value. It is fortunate that the effect of these alloying additions can be determined by laboratory experiments before application on an industrial scale is undertaken. 

The recovery of copper powder from wastewater of electronic industries was investigated in three-phase inverse fluidized-bed electrode reactors(0.102m ID x 1.0m). Effects of gas and liquid velocities, current density, distance between the two electrodes and amount of fluidized particles on the recovery of copper powder were examined. The addition of a small amount of gas or fluidized particles into the reactor resulted in the decrease in the powder size of copper recovered as well as increase in the copper recovery. The value of copper recovery exhibited a maximum with increasing gas or liquid velocity, amount of fluidized particles or distance between the two electrodes but increased with increasing current density. 

Effects of current density(I) on the recovery of copper in the reactor can be seen in Fig. 5. As can be seen, the value of R increased gradually with increasing ciurent density, since the mass transfer rate of copper ion is proportional to the current density. Effects of amount of fluidized particles on the recovery of copper can be seen in Fig. 6. Note that the addition of a small amount of fluidized particles (W=1.0wt.%) to the reactor could increase the copper recovery up to 10 25%. It has been mderstood that the contacting of fluidized solid particles with the cathode plate could clean the siuface as well as decrease the diffusion layer of copper ion, which results in the increases of reaction rate and current efficiency, thus, the recovery of copper could be increased. 

We consider that the practical electrode s efficiency at operation under high current density conditions and during service life is determined by the state of the particles of conductive additive s surface. With reference to this, we can point out two main factors effecting fundamentally reliable operation of the NiOx electrode. 

As was previously mentioned, PtRu alloys exhibit improved performance over pure Pt alloys.117,118 This is primarily a result of the ability of Ru to dissociate H20 for reaction with CO adsorbed on Pt sites.115,116 That CO oxidation on pure Ru is unfavorable indicates that on the bimetallic surface, CO is oxidized only on the Pt sites.119 Thus, CO is oxidized on Pt sites adjacent to Ru sites, where water is activated.120,121 This is known as a bifunctional mechanism. In addition, the presence of Ru atoms reduces the adsorption energy of CO on neighboring Pt atoms, lowering the activation energy of CO oxidation.122 This effect is purely electronic and is less significant than the bifunctional effect of Ru.123 One significant limitation of PtRu is the weak adsorption of methanol on Ru, particularly at room temperature.117,124 The weak adsorption severely hinders methanol decomposition, which is evident in Fig. 7 by the drop in current density for PtRu electrodes with high Ru composition.125... 

These are the use of the geminal dialkyl effect, the decrease of the current density and especially the use of an electrophilic double bond that increases the addition... 

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