Pyrite oxidation: the conservation of historic shipwrecks and geological and palaeontological specimens
| Main Authors: | , |
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| Format: | Article |
| Language: | English Slovak |
| ISSN: | ISSN 1605-8410 |
| Online Access: | http://www.viks.sk/chk/reviews_4_03_26_38.doc |
| Abstract: | Conclusions. In the presence of oxygen and water, pyrite is thermodynamically unstable with respect to oxidation. The relative stability of the material depends on the manner in which internal or external factors affect the kinetics of the reaction. The inescapable fact is that all pyrite is destined to oxidise when water and oxygen are present. The rate at which this takes place will depend on: ˙ Summaries. The role of pyrite oxidation in the degradation of geological and palaeontological collections is well known. The oxidation of pyrite, in the presence of water and oxygen, produces sulphuric acid and hydrates of iron(II) sulphate. Sulphuric acid causes further reactions and the iron(II) sulphate acts as an adsorbent for further water from the atmosphere, thereby promoting further oxidation. In addition to sulphuric acid, the oxidation of pyrite produces copious amounts of iron(II) and iron(III) ions in solution, which oxidises polyethylene glycol (PEG) used to prevent wood shrinkage and degrades cellulose in the timbers. Pyrite oxidation and the consequent production of sulphuric acid is a key factor in the acid wood hydrolysis of historical shipwreck timbers, resulting from the corrosion of iron-hull fastenings in anaerobic hydrogen sulphide-enriched waters and the sediments in which wrecks are often buried. Sulphur produced from bacterial reactions is also consequential. This paper will summarise the chemistry of pyrite oxidation and review the many factors that influence the oxidation rate. Methods of controlling pyrite oxidation have been proposed; some are described. Practical applications are introduced in relation to the overall oxidation process and its attenuation, but are not considered in depth as conservation treatments. The problem of pyrite formation in antique books is also briefly considered. |
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| ISSN: | ISSN 1605-8410 |
