Characterization of hydroxyl-bearing magnesium fluoride containing physically bound water

Abstract

Most electrolytic zinc plants have to deal with dissolved magnesium in their process liquors, as zinc sulphide concentrates contain small amounts of magnesium. Applied magnesium bleed methods are generally expensive and environmentally unfriendly. Recently, a new approach was suggested and discussed, which involves selective magnesium fluoride precipitation from purified zinc sulphate solutions. X-ray fluorescence measurements of these precipitates indicated that the ratio Mg:F is not 1:2 as would be expected if the precipitate was MgF 2 , which should be formed on a theoretical basis. It was inferred that fluoride was partly substituted by hydroxyl groups. Analytical techniques such as infrared absorption spectrometry, X-ray diffraction, and thermogravimetry were combined in order to verify this hypothesis. The precipitate indeed appeared to be a magnesium fluorohydroxide compound containing physically bound water. The results contribute to the understanding of the required operating conditions of the proposed process.

Synthesis and characterization of MgF2–CoF2 binary fluorides. Influence of the treatment atmosphere and temperature on the structure and surface properties

“…98)), hence any changes in the unit cell parameters caused by the replacement of F À by OH À would be slight. However, they should be noticeable because the introduction of OH À groups into the MgF 2 structure results in a small increase in the lattice constant a and a decrease in the c constant, as proved by Booster et al 84 We have not observed such changes, hence our conclusion is that the proposed Mg(OH) 2Àx F x groups are the only surface complexes. A conclusion that similar complexes are present on the surface of CoF 2 seems to be interesting.…”

“…79 and 83) and by many earlier reports on hydroxylated MgF 2 . 1,35,36,40,[47][48][49][84][85][86][87] Verdier et al 79,83 ascribed them to the Mg(OH) 2Àx F x species. The presence of surface complexes of such a type is indicated by the values of DE F 1s -Mg 2p that are equal to 634.5-634.7 eV, which in the case of crystalline MgF 2 are about 633 eV and in that of Mg(OH) 2Àx F x they range between 634.5 and 635.0 eV.…”

Synthesis and structure of magnesium hydroxide fluoride, Mg(OH)F: a topological intermediate between brucite- and rutile-type structures

“…They noted that the variation in the cell parameters with OH substitution in sellaite may lead to the formation of a structurally continuous series between the endmembers and the intermediate structure, which has the formula Mg(OH)F. Although there have been reports of Mg(OH,F) 2 solid solutions, relating primarily to crystallization behaviour in concretes (e.g. Booster et al, 2002), and Mg(OH,F) 2 formation in aqueous systems (Booster et al, 2003), Mg(OH)F is a distinct phase as demonstrated by the TÀX diagrams of Crane and Ehlers (1969). Fluorine can be incorporated into brucite (and OH into sellaite) to a very considerable degree, but in the region of composition space around 1:1 OH:F a separate phase exists.…”

Influences of Oxygen Ion Beam on the Properties of Magnesium Fluoride Thin Film Deposited Using Electron Beam Evaporation Deposition

“…Dumasp's research showed that the use of Ar as an ion source to assist gas deposition increased the bulk density of MgF 2 films, but excessive particle energy led to a change in the stoichiometric ratio of Mg and F, resulting in F atom vacancies, which led to the absorption of ultraviolet and visible parts [12,13]. These studies further show that excessive Ar + ion energy can lead to more serious moisture absorption problems when MgF 2 thin films are evaporated by an electron gun [14].…”