Stripping of the metal

Electrical resistance monitors use the fact that the resistance of a conductor varies inversely as its cross-sectional area. In principle, then, a wire or strip of the metal of interest is exposed to the corrodent and its resistance is measured at regular intervals. In practice, since the resistance also varies with temperature, the resistance of the exposed element is compared in a Wheatstone bridge circuit to that of a similar element which is protected from the corrodent but which experiences the same temperature. 

With many other combinations, the composition of the species extracted are mostly uncertain and the equilibria involved are often very complex involving polymeric species, many times. However many of these systems hold promise of offering useful separation schemes since in some of these systems using carboxylic acids, for example, the extraction and back extraction (stripping) of the metal ions can be achieved in the same system simply by controlling the pH of the aqueous medium. 

Cut two flashlight batteries at both ends until you get to their carbon rods. Clean off the rods and wrap an inchwide strip of the metal cover of a battery tightly around one end of each rod. 

The distribution ratios for the extraction of the elements to be recovered (uranium and thorium, for example) may be optimized such that both elements can be efficiently extracted then selectively stripped into HNO3. Optimizing the distribution ratios eliminates the necessity of adding complexing agents to the aqueous phase for selective stripping of the metals. 

Hanging mercury drop electrode (HMDE) A microelectrode that can concentrate traces of metals by electrolysis into a small volume the analysis is completed by voltammetric stripping of the metal from the mercury drop. 

Anodic stripping voltammetry. The initial reduction and collection of metals at the surface of an anode, and the subsequent stripping of the metals by oxidation, resulting in a voltammogram that identifies the metals and their respective concentrations. 

In this figure, Ihc half-cell on the right consists of a strip of the metal M in contact with a solution of M . The half-cell on the left is a SHE. By definition, the potential E observed on the voltmeter is the electrode potential for the M /M couple. In this general example, we assume that the junction potentials across the salt... 

Stripping of the metal from the loaded organic phase is just as important as extraction, and here this process is achieved quite simply by a change in acidity of the system. However, it should be remembered that extractants that extract metals at low pH values will require more concentrated add for stripping. Thus, it is not always a good idea to use the extractant that extracts too well. Also it is important to realize that extraction and separation is only one process in a hydrometallurgical flow sheet, and it is necessary to choose the extractant that will most easily interface with the operations both upstream and downstream. 

Stripping of the metal from the loaded organic phase can be achieved by causing the breakdown of either the anionic metal complex with, for example, water, or the cationic extractant by treatment with a base. The latter will, of course, not work in the case of the qnatemary tetraalkylammonium ions, R4N. ... 

Various means of trace accumulation and determination are used in stripping voltammetry. In the simplest case the analyte is reduced to the metal and accumulated as an amalgam at a stationary mercury electrode (HMDE or TMFE). The determination step proceeds in the reverse direction to the accumulation and is based on the anodic stripping of the metal (reoxidation). This process of ASV is also known as inverse voltammetry and can be illustrated as follows ... 

Octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) is one of the representative extractants developed for the separation and recovery of actinides in the nuclear industry. Nakashima et al. investigated the extraction behavior of trivalent rare-earth metals with CMPO using ILs as an extracting phase and demonstrated that not only the extraction efficiency but also the mutual selectivity was remarkably enhanced, in comparison with that in n-dodecane [8]. Although such advantages were observed in the extraction step, the stripping of the metal ions from the extracting IL phase was difficult due to the unique extraction mechanism in the IL system as follows ... 

To eliminate the tedious operations involved in the preparation of electrodes for weighing to determine the amount of metal deposited or removed, Ehlers and Sease (19) proposed a coulometric coulometer which employs constant current stripping of the metal deposited during the primary electrolysis. The current to be measured is used to deposit copper metal from a copper sulphate electrolyte on a platinum cathode the copper-plated platinum electrode is then reconnected as the anode and the deposited copper stripped off at constant current. The current-time products obtained were suited for the determination of quantities of electricity in the 0.015-75 coulomb range with a standard deviation of0.096 per cent. Castro (20)... 

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