Solid solution formation between Mn(II) and Mg(II) hydroxides in alkaline aqueous solution
2001 (English)In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 16, no 3, 240-5 p.Article in journal (Refereed) Published
In this work, it is shown that Mn(II) can be incorporated into a solid, variable-composition, hydroxide phase with Mg(II), and that this phase can be characterised as a so-called solid solution. The experiments have been conducted in the 1-10 mM concentration range from initially supersaturated solutions, with a constant ionic medium of 0.1 M Na(Cl). Data were collected at Mg(II):Mn(II) molar ratios ranging from 1:3 to 31:1 and in the temperature range of 50 degreesC to 90 degreesC. The measurements are based on potentiometry and ICP-OES analyses of metal ion concentrations, and they show that the solubilities of the two metal ions are continuously interdependent. To provide a predictive quantitative model for the suppressive effect of Mg(II) upon Mn(II)(aq), the apparent solubility product of Mn(OH)(2)(s) in the presence Mg(Er) was evaluated as a function of temperature, ageing time, [Mg(II)](tot)/[Me(II)](tot), [Mn(II)](tot)/[Me(II)](tot) and [OH.](tot)/[Me(II)](tot), where [Me(II)](tot)=[Mg(II)](tot)+[Mn(II)](tot). The equation describing this interplay is: [GRAPHICS] The corresponding expression, for the apparent solubility product of Mg(OH)(2)(s) in the presence of Mn(II), is: The results of this work can explain the role of Mg(II) as a redox stabiliser of Mn(II) during alkaline oxygen delignification and peroxide bleaching, since by maximising the concentration of Mg(II) at a given high pH, the concentration of aqueous Mn(II) is minimised and the solid-state Mn(II) is buried in a Mg(II)-dominated solid phase.
Place, publisher, year, edition, pages
2001. Vol. 16, no 3, 240-5 p.
manganese, magnesium, hydroxide, ions, aqueous solution, solid solution, potentiometric titration, temperature, solubility, hydrogen peroxide stabilisation, oxygen delignification, pulp bleaching
IdentifiersURN: urn:nbn:se:umu:diva-9001DOI: doi:10.3183/NPPRJ-2001-16-03-p240-245OAI: oai:DiVA.org:umu-9001DiVA: diva2:148672