Naslov
Deposition and dissolution of metal sulfide layers at a Hg electrode surface in seawater electrolyte conditions

Autori
Milanović, Ivana ; Krznarić, Damir ; Bura-Nakić, Elvira ; Ciglenečki, Irena

Izvornik
Environmental chemistry (1448-2517) 11 (2013), 2; 167-175

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
sulfide; metal sulfides; FeS; voltammetry; Hg electrode

Sažetak
Cyclic voltammetry on the Hg electrode was used to investigate metal ion (Zn, Cd, Cu, Fe, Pb, Co) influence on the HgS deposition/dissolution process in seawater conditions. Hg electrode, due to exchange between Hg2+ from an HgSlayer and free metal (M2+) from solution (HgSlayer + M2+ + 2e-  MSlayer + Hg0), becomes the site for surface metal sulfide (MS) formation. The exchange reaction is reversible, and the surface-formed MSlayer stays at the Hg electrode more negative than HgS reduction (MSlayer + 2e- + H+ → M0 + HS). The potentials of both electrode reactions: formation and reduction of the MS layers are controlled by MS solubility product. In solutions containing excess of free metal in comparison to the free sulfide, exchange reaction produces MS voltammetric peak, which can be misrepresented for dissolved sulfide species. This work indirectly confirmed that FeS electrochemical signal, usually recorded in an iron and sulfide rich environment at around -1.1 V vs. Ag/AgCl, is not due to FeS reduction. Relationship between studied MS reduction peak potentials and solubility products shows that FeS layer formed by electrochemical exchange reaction with HgS should be reduced at the Hg surface approximately 100 mV more negative than free Fe2+.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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