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Effects of weathering on the surface and chemical properties of chrysotile asbestos : implications for management of naturally occurring asbestos and carbon dioxide sequestration in ultramafic mine tailings Holmes, Emma


This study focuses on the surface properties of chrysotile asbestos and the effects that naturally occurring acids and different environments, specifically stream and mine tailing environments, have in altering the surface chemistry. Surface reactions are likely the governing factors affecting chrysotile, both as a toxicant and as a carbon sequestration material. This information is important for concerns related to naturally occurring chrysotile asbestos in the environment and carbon dioxide sequestration in chrysotile tailings. FESEM, XRD, ATR FTIR, zeta potential, aqua regia digestion, ICP-MS, and ToF-SIMS were used to examine the bulk and surface properties of chrysotile asbestos. Oxalic acid and hydrochloric acid are effective at removing the magnesium brucite layer, and associated trace metals, and reducing the surface charge of chrysotile asbestos. Fibers treated with these acids are likely less hazardous from a human health perspective. Carbonic acid, a weaker acid, is much less effective at altering the surface properties of chrysotile. Natural weathering in stream and mine tailing environments altered the surface properties of chrysotile asbestos, but the extent remains unknown. It appears that the slow dissolution of magnesium is the rate-limiting step for the mineral carbonation process. The results of zeta potential analysis, a surface specific technique measured on a bulk sample, are supported by ToF-SIMS analysis, a very fine scale surface specific technique measuring a small area of one fiber. Zeta potential analysis is less expensive and time consuming to carry out than is ToF-SIMS and measures the surface characteristics of a larger sample which enables it to better account for the variability within a sample. Covering naturally occuring asbestos deposits with acid producing organic matter could enhace the weathering of chrysotile and likely reduce its toxicity over time, while also acting as a barrier, preventing the fibers from becoming airborne and posing an inhalation hazard. Treating chrysotile mine tailings with naturally occuring acids will release more magnesium, potentially increasing the rate of carbon sequesrtation.

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