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Electrochemical Extraction and Refining Processes
Published in Alan Cottrell, An Introduction to Metallurgy, 2019
Arranged in order of their electrode potentials, the elements form the electrochemical series. Any metal will displace from aqueous solution the ions of a metal more noble than itself in the series; e.g. when iron is put into copper sulphate solution it becomes coated with metallic copper. Hydrogen is more noble than many of the metals in the series. In such cases, when positive ions arrive from solutions at a cathode and collect electrons there hydrogen gas is formed rather than metal deposited. This limits aqueous extraction and refining processes to the more noble metals.
Batteries and alternative sources of energy
Published in John Bird, Science and Mathematics for Engineering, 2019
The electrochemical series is representative of the order of reactivity of the metals and their compounds: (i) The higher metals in the series react more readily with oxygen and vice versa.(ii) When two metal electrodes are used in a simple cell the one that is higher in the series tends to dissolve in the electrolyte.
Batteries and alternative sources of energy
Published in John Bird, Electrical and Electronic Principles and Technology, 2017
The electrochemical series is representative of the order of reactivity of the metals and their compounds: The higher metals in the series react more readily with oxygen and vice-versa.When two metal electrodes are used in a simple cell the one that is higher in the series tends to dissolve in the electrolyte.
Colorimetric optical chemosensor of toxic metal ion (Hg2+) and biological activity using green synthesized AgNPs
Published in Green Chemistry Letters and Reviews, 2018
Abul Kalam, Abdullah G. Al-Sehemi, Sulaiman Alrumman, Mohammed Assiri, Mahmoud Fawzy Mahmoud Moustafa, Pankaj Yadav, Mehboobali Pannipara
Colorimetric trial was accomplished to the primary detection of metal ions. Figure 4(a) represents the performance of different metal ions (Cd2+, Fe2+, Co2+, Pb2+, Ni2+, Mn2+, Hg2+) with synthesized AgNPs and absorption spectra were chronicled. Figure 4(c) displays the color change side view of various metal ions (10−3 M) by the addition of green synthesized AgNPs (TE-3). The brown color of green synthesized AgNPs turned into colorless with Hg2+ among the other metal ions which corroborated the selective sensing of Hg2+ ion. In addition, the colorimetric sensing was also tested by using a paper-based device. Figure 4(b) represents that the color of AgNPs was quickly envisaged through naked eye within a few seconds. It is clear from the absorption spectra as well as color of green synthesized AgNPs that the green synthesized AgNPs are extremely selective to mercury ion over other metal ions. Moreover, the selectivity of Hg2+ ion with AgNPs was analyzed using absorption spectra and naked eye. Figure 5(b) represents that the color of AgNPs deviates from the variation of concentration of Hg2+ ion. The absorption spectra of AgNPs with different concentrations of Hg2+ ion (100.1 µ M) are shown in Figure 5(a). It is clear from the spectra that by increasing the concentration of Hg2+ ions, the absorption spectra decrease simultaneously. Electrochemical series could be used for the explanation of colorimetric sensing mechanism of Hg2+ ion. According to the electrochemical series, metals with higher electrochemical reduction potential act as better oxidizing agents. As we know that, the standard reduction potential of Ag+ and Hg2+ is 0.80 V and 0.92 V, respectively. Figure 5(a) inset represents a good linear correlation between the net adsorption (ΔA) value and the concentration of Hg2+ over the concentration range from 0.1 to 10 µM (R2 = 0.98124). Table 1 represents the comparative LOD of Hg2+ ion using green synthesized AgNPs. The results revealed that LOD obtained in the present study is the lowest as compared to that of the previously reported green synthesized AgNPs.