Nature of the silver precipitation obtained by cementation from thiosulphate solutions |
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| Authors: | O Kuntyi G Zozulya I Saldan V Kree S Korniy and B Stel’makhovych |
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| Institution: | (1) School of Engineering of Bilbao, Chemical and Environmental Engineering Department, University of the Basque Country, UPV-EHU, Alameda Urquijo, s/n, 48013 Bilbao, Spain |
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| Abstract: | The morphology and composition of the deposits formed on the surface of magnesium disk during cementation from thiosulphate
solutions (0.0025–0.1M) Ag(S2O3)2]3− + 0.5M S2O3
2− have been studied. A porous deposit with low adhesion is formed on the surface of the magnesium metal substrate. Within a
wide range of Ag(S2O3)2]3− ion concentrations, sulfur as well as silver are constituents of the deposit at the initial stages of cementation and at
the end of the reaction. This is attributed to the electrochemical behaviour of magnesium in thiosulphate solutions resulting
in the exceeding of current limit on cathode for pure silver reduction. Hence, parallel electrochemical reactions take place
that are very close in their values to the standard redox potentials of reduction of Ag(S2O3)2]3− ions to Ag0 and S2O32− ions to S2−. Sulfur content in the cement deposits increases with the decrease in Ag(S2O3)2]3− ion concentration and increase in cementation time. This tendency is also observed with the decreasing solution temperature. |
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