Introduction: Dissolution and precipitation of feldspar is an important reaction in many environmental systems, as plagioclase feldspar is the most common mineral in the crust. However, the mechanism of dissolution of feldspar has remained in dispute despite twenty or more years of analysis of feldspar dissolution. We are pursuing an approach toward better understanding of feldspar dissolution by investigating reactivity of aluminosilicate glasses of variable composition. In particular, to investigate the effects of Al/Si ratio on plagioclase dissolution without complications of varying Na/Ca content or exsolution, three glasses with varying Al/Si ratio (albite, jadeite, nepheline) were synthesized. Glass powders were then prepared and dissolved at various values of pH in batch reactors under ambient conditions. Solution chemistry was analyzed by inductively coupled plasma -optical emission spectroscopy or -mass spectrometry. In addition, alteration of the glass surface was investigated using Xray photoelectron spectroscopy, secondary ion mass spectrometry, and Fourier transform infrared spectroscopy. Dissolution results: Many similarities in dissolution behavior between plagioclase crystals and this suite of glasses were observed: 1) dissolution was slowest at near-neutral pH and increased under acid and basic conditions, 2) dissolution rate at all pH values increased with increasing Al/Si ratio, 3) the pH dependence of dissolution was higher for the phase with Al/Si = 1 than the phase with Al/Si = 0.3, 4) after acid leaching, the extent of Al-depletion of the altered surface increased with increasing bulk Al/Si ratio from Al/Si = 0.3 (albite) to 0.5 (jadeite), but then decreased in nepheline (Al/Si = 1.0), which dissolved stoichiometrically with respect to Al, and 5) little to no Al depletion of the surface of any glass occurred at pH > 7. However, in contrast with some observations for plagioclase dissolution, log(rate) increased almost linearly with Al content, and n, the slope of the log(rate)pH curve at low pH, varied smoothly from albite to jadeite to nepheline (n = 0.3, 0.6, 1.0 respectively). At high pH, the slope of this curve, m, did not differ between glasses (m = -0.4 + 0.1). Mechanistic interpretation: These results are consistent with an identical mechanism controlling dissolution of nepheline, albite, and jadeite glass, although no Si-rich layer can develop on nepheline because of the lack of Si-O-Si linkages. Such a conclusion is consistent with a transition state for these aluminosilicates at high pH consisting of a deprotonated Q3 hydroxyl group (where Qv refers to an x atom in a tetrahedral site with v bridging oxygens) or a five-coordinate Si site after nucleophilic attack by OH, and, at low pH, a protonated Q4OQ4. At low pH, we infer that Q4OQ4 Al linkages are ratelimiting because they are presumed to hydrolyze more slowly than Qv OQw Si (v,w < 3). According to this model, dissolution rate increases from albite to jadeite to nepheline because hydrolysis of Al-O-Si linkages becomes more energetically favorable as the number of Al atoms per Si tetrahedral increases, a phenomenon documented by geometry optimizations using ab initio methods (for example, Figure 1). However, a model wherein Q4OQ4 Si linkages are faster to hydrolyze than lower connectivity linkages between Si atoms (Qv OQw , v,w < 3) may also explain aspects of this data.

/pdf/role-of-polymerization-in-the-dissolution-of-nepheline-3l2f6z3q8d.pdf

Role of Polymerization in the Dissolution of Nepheline, Jadeite, and Albite Glasses: Toward Better Models for Aluminosilicate Dissolution

Influence of Er3+ ion concentration on optical and photoluminescence properties of Er3+-doped gadolinium-calcium silica borate glasses

A Review on Optical Applications, Prospects, and Challenges of Rare-Earth Oxides

Influence of tungsten on the emission features of Nd3+, Sm3+ and Eu3+ ions in ZnF2–WO3–TeO2 glasses

Eu2+/Sm3+ ions co-doped white light luminescence SrSiO3 glass-ceramics phosphor for White LED

Effect of thermal treatment on excited state spectroscopy of oxyfluoride borosilicate glass activated by Pr3+ ions

Spectroscopic properties of transparent Er-doped oxyfluoride glass–ceramics with GdF3☆

Excited state absorption spectroscopy of ZBLAN:Er3+ glass — Experiment and simulation

Framework influence of erbium doped oxyfluoride glasses on their optical properties

The paper presents a new glass ceramics of the SiO 2 -B 2 O 3 -Na 2 O-LaF 3 system in which nanocrystallization of LaF 3 could be obtained. Thermal stability of glass and the crystallin e phases formed upon heat treatment were determined by DTA/DSC and XRD methods, respectivel y. The effect of incoming of Pr 3+ to LaF 3 crystals in the glassy host has been shown in the emission spectra. The 3 P 0 3 H J emissions have been much stronger in glass-ceramics what supports the suggestion that 3 P 0 1 3+ D 2 non-radiative decay dominates the relaxation of 3 P 0 for Pr ions in the as-made glass. Keywords : oxyfluoride glass-ceramics, LaF 3 , Pr 3+ luminescence, borosilicate glass 1. INTRODUCTION In the recent years, oxyfluoride transparent glass ceramics doped with lanthanide ions based on the aluminosilicate glassy matrix have been studied [1 - 3]. The effect of ceramization leading to LaF 3 nanocrystals formation makes the materials desirable for upconversion, lasers and amplifiers and for active photonic devices due to the high rare earth ion solubility and low phonon energy in LaF

Time resolved spectroscopy of oxyfluoride glass ceramics activated by Pr 3 + ions

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