Bulk Dissolution Rates of Cadmium and Bismuth Tellurides As a Function of pH, Temperature and Dissolved Oxygen

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• 作者：Marc Biver ; Montserrat Filella
• 刊名：Environmental Science & Technology
• 出版年：2016
• 出版时间：May 3, 2016
• 年：2016
• 卷：50
• 期：9
• 页码：4675-4681
• 全文大小：415K
• 年卷期：0
• ISSN：1520-5851

文摘

The toxicity of Cd being well established and that of Te suspected, the bulk, surface-normalized steady-state dissolution rates of two industrially important binary tellurides–polycrystalline cadmium and bismuth tellurides– were studied over the pH range 3–11, at various temperatures (25–70 °C) and dissolved oxygen concentrations (0–100% O₂ in the gas phase). The behavior of both tellurides is strikingly different. The dissolution rates of CdTe monotonically decreased with increasing pH, the trend becoming more pronounced with increasing temperature. Activation energies were of the order of magnitude associated with surface controlled processes; they decreased with decreasing acidity. At pH 7, the CdTe dissolution rate increased linearly with dissolved oxygen. In anoxic solution, CdTe dissolved at a finite rate. In contrast, the dissolution rate of Bi₂Te₃ passed through a minimum at pH 5.3. The activation energy had a maximum in the rate minimum at pH 5.3 and fell below the threshold for diffusion control at pH 11. No oxygen dependence was detected. Bi₂Te₃ dissolves much more slowly than CdTe; from one to more than 3.5 orders of magnitude in the Bi₂Te₃ rate minimum. Both will readily dissolve under long-term landfill deposition conditions but comparatively slowly.