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Silicate minerals
About: Silicate minerals is a research topic. Over the lifetime, 1794 publications have been published within this topic receiving 67064 citations.
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TL;DR: In this article , the authors describe the retrieval and regression of the dissolution rates of the primary rock-forming silicates, including quartz and other SiO2 polymorphs, feldspars, pyroxenes, amphiboles, micas, volcanic glass, and olivines.
13 citations
TL;DR: In undersaturated solutions, dissolution rates for uranyl phosphate, oxyhydroxide, and silicate minerals can be predicted within 1-2 orders ofmagnitude from pH ∼5-10 on the basis of pH/carbonate concentration, and faster dissolution rates were attributed to the formation of binary and ternary uranyl carbonate complexes.
Abstract: Uranyl phosphate minerals represent an important secondary source of uranium release at contaminated sites. In flow-through column experiments with background porewater (BPW) of typical freshwater aquifer composition (pH 7.0, ∼0.2 mM total carbonate (TC)), dissolution of K-ankoleite (KUO2PO4·3H2O), Na-autunite (NaUO2PO4·3H2O), and Ca-autunite (Ca(UO2)2(PO4)2·6H2O) was controlled by mineral solubility at steady-state U release. Effluent concentrations indicated exchange with BPW cations, and postreaction characterization showed alteration of the initial mineral composition, changes in structure (decreased crystallinity, increased disorder, and distortion of U-P mineral sheets) and possible neoformation of phases of similar structure. Increasing the BPW pH and TC to 8.1-8.2 and 2.2-3.7 mM, respectively, resulted in mineral undersaturation and produced ca. 2 orders-of-magnitude higher U and P release without reaching steady state. Minerals incorporated less BPW cations into their structures compared to low carbonate BPW experiments but showed structural disorder and distortion. Faster dissolution rates were attributed to the formation of binary and ternary uranyl carbonate complexes that accelerate the rate-determining step of uranyl detachment from the uranyl-phosphate layered structure. Calculated dissolution rates (log Rs between -8.95 and -10.32 mol m-2 s-1), accounting for reaction and transport in porous media, were similar to dissolution rates of other classes of uranyl minerals. In undersaturated solutions, dissolution rates for uranyl phosphate, oxyhydroxide, and silicate minerals can be predicted within 1-2 orders-of-magnitude from pH ∼5-10 on the basis of pH/carbonate concentration.
13 citations
01 Jan 2008
13 citations
TL;DR: The J-M Reef is an interval of disseminated sulfides in the Lower Banded series of the Stillwater Complex that is enriched in the platinum group elements (PGE).
13 citations