Cation hydrolysis and the regulation of trace metal composition in seawater |
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| Institution: | 1. Laboratory of Environmental Pollution Analysis, Faculty of Biology, University of Warsaw, Miecznikowa 1, 02–096 Warsaw, Poland;2. AGH University of Science and Technology, Faculty of Geology, Geophysics and Environmental Protection, Department of Mineralogy, Petrography and Geochemistry, Mickiewicza 30, 30-059 Krakow, Poland;3. AGH University of Science and Technology, Faculty of Materials Science and Ceramics, Department of Ceramics and Refractories, Mickiewicza 30, 30-059 Krakow, Poland;4. Faculty of Chemical and Process Engineering, Warsaw University of Technology, Ludwika Warynskiego 1, 00-645 Warsaw, Poland;1. Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Modena e Reggio Emilia, via Campi 103, I- 41125 Modena, Italy;2. Dipartimento di Scienze della Terra, Università degli Studi di Torino, Via Valperga Caluso 35, I-10125 Torino, Italy;3. Interdepartmental Centre “Nanostructure Interfaces and Surfaces NIS”, Via Pietro Giuria 7, I-10125 Torino, Italy;4. Dipartimento di Chimica, Università di Torino, Via Giuria 7, I-10125 Torino, Italy;5. Dipartimento di Scienza ed alta Tecnologia, Università degli Studi dell’Insubria, Via Valleggio 11, I-22100 Como, Italy;6. Dipartimento di Scienze Matematiche e Informatiche, Scienze Fisiche e Scienze della Terra, Università degli Studi di Messina, viale F. Stagno d’Alcontres 31, I-98166 Messina S. Agata, Italy;1. Department of Mining and Materials Engineering, McGill University, 3610 University Street, Montreal, QC, H3A 0C5, Canada;2. Department of Chemical Engineering, McGill University, 3610 University Street, Montreal, QC, H3A 0C5, Canada;1. Lahore College for Women University, Lahore 54000, Pakistan;2. Centre of Excellence in Solid State Physics, University of the Punjab, Lahore 54950, Pakistan;3. Government College for Women University, Sialkot, Pakistan |
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| Abstract: | Thermodynamic calculations have been performed for cation hydrolysis, including temperatures from 2°C to the high values of significance near Mid-Oceanic Ridge Systems (MORS). Eighteen elements with wide range of residence times (t) in seawater (Mn, Th, Al, Bi, Ce, Co, Cr(III), Fe, Nd, Pb, Sc, Sm, Ag, Cd, Cu, Hg, Ni and Zn) have been considered. A model for the regulation of trace metal composition in seawater by cation hydrolytic processes, including those at MORS, is presented. Results show an increase in the abundance of neutral metal hydroxyl species with increase in temperature. During hydrothermal mixing, as the temperature increases, transformation from lower positive hydroxyl complexes to higher or neutral complexes would occur for Cd, Ce, Co, Cr(III), Cu, Mn, Nd, Ni, Pb, Sm and Zn. pH values for adsorption of the metal ion onto solid surfaces have direct relation with pH values of hydrolysis. Co, Mn and Pb could be oxidized to higher states (at Mn-oxide surfaces) that would occur even at MORS. Ce can also be oxidized at 25°C. Solubility calculations show that Al, Bi, Cr(III), Sc, Fe and Th are saturated while Ce, Nd and Sm are not with respect to their oxyhydroxide solids at their concentrations in seawater at 25°C. Cu, Hg, Ni and Zn reach saturation equilibrium at 250°C, whereas Co, Mn and Pb exhibit unsaturation. The results suggest an increase in scavenging capacity of a cation with rise in temperature. |
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