C.Smith IER Lesson
•
1 gostou•491 visualizações
Lesson designed to explain ion exchange resin technology to fellow students in a class on masonry.
Recomendados
Recomendados
Mais conteúdo relacionado
Mais procurados
Mais procurados (20)
Destaque
Destaque (13)
Semelhante a C.Smith IER Lesson
Semelhante a C.Smith IER Lesson (20)
Mais de Caitlin Smith
Mais de Caitlin Smith (13)
C.Smith IER Lesson
- 1. Chemistry 101: Utilizing Ion Exchange Resins to Chemically Clean Masonry HSPV 743 - Conservation Seminar: Masonry Caitlin Smith Spring 2009 Disclaimer: I am not now, nor have I ever been, a chemist…
- 2. Ion Exchange Resins Introduction Natural Ion-Exchangers have been around since the dawn of time... Source: Robert Kunin, Ion Exchange Resins(New York: John Wiley & Sons, Inc.,1958), 2-3.
- 4. Ion Exchange Resins Chemistry Basic polymeric chain matrix Fixed ionic groups and exchangeable counterions Water activates ionisation Structure makes it INSOLUBLE in water!!! Cation Exchange – R–A- H+ + Cation+ -> – R–A- Cation+ + H+ Anion Exchange – R–C+ OH- + Anion- -> – R–C+ Anion- + OH- E = What?! Source: Andrei A. Zagorodni, Ion Exchange Materials Properties and Applications (Oxford, UK: Elsevier BV, 2007), 20.
- 5. Ion Exchange Resins Chemistry Show and Tell Source: Andrei A. Zagorodni, Ion Exchange Materials Properties and Applications (Oxford, UK: Elsevier BV, 2007), 84, 155.
- 6. Ion Exchange Resins Masonry Trends 1940s – Synthetic Resins 1970s – Adapted for Conservation Expanding the technology Focus on improving field applications Development of commercial industry I <3 Chemistry Source: Robert Kunin, Ion Exchange Resins (New York: John Wiley & Sons, Inc.,1958), 83; IN SITU Conservation Restoration & Preservation Materials & Equipment, http://www.insituconservation.com/catalog/advanced_search_result.php?osCsid=615d56153b725c042caace82fd01187 5&keywords=ion+exchange&categories_id=&inc_subcat=1&x=0&y=0 (accessed April 13, 2009).
- 7. Ion Exchange Resins Advantages Requires less water than other cleaning treatments Does not alter morphology (no mechanical action) Does not alter porosity of entire material, only acts on surface Replaces harmful ions with inocuous ones Can act as a natural consolidant Can be regenerated and reused Cleaning action easily controlled by operator Easy application A + Source: Robert Kunin, Ion Exchange Resins (New York: John Wiley & Sons, Inc.,1958), 86, 328, 329.
- 8. Ion Exchange Resins Disadvantages Can be damaging to surface of calcareous stones Could cause alternation and dissolution of rock-forming minerals May not be able to contain ions of a certain size May not be cost effective May require multiple applications to remove high concentrations Could be too acidic D- Source: Nicola Berlucchi, Ricardo GinanniCorradini, Roberto Bonomi, EdoardoBemporad, and Massimo Tisato, “’La Fenice’ Theatre – Foyer and Apollinee Rooms – Consolidation of Fire-Damaged Stucco and Marmorino Decorations by Means of Combined Applications of Ion-Exchange Resins and Barium Hydroxide,” in Proceedings of the 9th International Congress on Deterioration and Conservation of Stone, Venice, June 19-24, 2000, vol. 2, ed. Vasco Fassina (Amsterdam, The Netherlands: Elsevier Science B.V., 2000), 27.
- 9. Ion Exchange Resins Cleaning Desulfation/Encrustation Removal Target calcium-containing salts 2R+––OH- + Ca SO4 -> R+2 ––SO42- + Ca ( OH )2 Target calcareous crusts, including gypsum Focus on calcareous substrates: limestone, marble, and gypsum Source: VivianaGuidetti and MaciejUminski, “Ion exchange resins for historic marble desulfatation and restoration,” in Proceedings of the 9th International Congress on Deterioration and Conservation of Stone, Venice, June 19-24, 2000, vol. 2, ed. Vasco Fassina (Venice: Elsevier Inc., 2000), 331.
- 10. Ion Exchange Resins Cleaning Source: VivianaGuidetti and MaciejUminski, “Ion exchange resins for historic marble desulfatation and restoration,” in Proceedings of the 9th International Congress on Deterioration and Conservation of Stone, Venice, June 19-24, 2000, vol. 2, ed. Vasco Fassina (Venice: Elsevier Inc., 2000), 332. Consolidation/Stabilization Calcium carbonate forms a natural consolidant when: Ca ( OH )2 + CO2 -> CaCO3 + H2 O Stabilization of clay minerals by replacing ions reduces swelling capacity
- 11. Ion Exchange Resins Cleaning Removal of Biological Growth Target and remove water soluble phosphates in an effort to remove biological growth and prevent re-growth Source: Caitlin Smith, April 9, 2009. Source: Andrei A. Zagorodni, Ion Exchange Materials Properties and Applications (Oxford, UK: Elsevier BV, 2007), 48.
- 12. Ion Exchange Resins Evaluation Properties: Rheological Adhesion to substrate Fissuration on drying Water retention Quantity of ions removed Tests run: Ion chromatography EDS/SEM Water absorption Morphology Thin-section light microscopy CIELab Source: Robert Kunin, Ion Exchange Resins (New York: John Wiley & Sons, Inc.,1958), 86, 328, 329.
- 13. Ion Exchange Resins Questions? I will not run over my time… I will not run over my time I will not run over my time I will not run over my time I will not run over my time I will not run over my time I will not run over my time I will not run over my time I will not run over my time I will not run over my time I will not run over my time I will not run over my time I will not run over my time I will not run o… The End
Notas do Editor
- You guys know that everything in the world is made up of atoms and molecules. Well, an ion is simply an atom or molecule which has lost or gained one or more electrons, giving it a positive or negative electrical charge. Ion-exchangers are materials that are able to exchange ions within their structure with ions outside their structure, and it is always an even exchange where it gains the same number of ions as it loses, and the new ions are always of the same charge as the old ones. All exchangers fall into one of three categories: cationic, anionic, or mixed type (cationic + anionic). The exchange type is determined by the type of ion (which are again classified by electrical charge) that the material exchanges.The overall exchange process consists of five stages: (1) diffusion of ions through the solution to the surface of the exchange particles, (2) diffusion of these ions through the gel particle, (3) the exchange of these ions with those already in the exchanger, (4) diffusion of these displaced ions through the exchanger, and (5) diffusion of these displaced ions through the solution.
- The basic chain (polymeric matrix) structure of ion-exchangers makes the exchange reaction possible. The chain contains fixed ionic groups in equilibrium with a counterions of an opposite charge, each attached to the chain with covalent links. The counterion is the exchangeable part of the structure and, according to its electrical charge, is classified as either cationic (positive) or anionic (negative). The reaction mechanism for cations and anions is as follows:– R–A- H+ + Cation+ → – R–A- Cation+ + H+ – R–C+ OH- + Anion- → – R–C+ Anion- + OH-From these equations it is apparent that counterions are always the opposite charge of the fixed groups or sites, or in other words they compensate for the fixed charge. Cation exchange materials are materials that possess negatively charged fixed groups or sites and exchangeable ions of the opposite charge (cations). Anion exchange materials possess positively charged fixed groups or sites and exchangeable ions of the opposite charge (anions).Coss-linking of the polymeric chains makes ion exchange resins insoluble in water. When dry, the functional groups in ion-exchangers are non-ionised. When in water, cross-linked functional polymers become ionized and swell to hold a high water content.
- So here are some resins in different forms. A resin’s ionic form is determined by the counterions that are present. For example, here we have cation exchangers in sodium form, meaning they contain exchangeable Na+ ions, and cation exchangers in H+ form.
- Since I hit you right off the bat with chemistry, I will spare you the history of ion-exchange technology, suffice it to say that by the 1940s, we were capable of synthesizing extremely stable and versatile resins. These “tailor-made” resins could be targeted for very spec By the 1970s, conservationists were adapting resins for use in heritage-related cleaning studies. Since this time, ion-exchange has become widely accepted as a method for salt removal, particularly in carbonate rocks. The studies tend to be connected to more general studies into methods for removing gypsum crusts.Conservators have moved away from traditional methods of ion-exchange, such as the ion-exchange column, to various poultice and gel mixtures. Recent studies do not focus on the applicability of resins, but instead what can be added to them to make them better suited for on-site applications. Slowly resins are being taken out of the lab, and into the buildings. Also in response to these trends, a number of commercial products are being designed and sold specifically for heritage projects. In particular, the European companies Syremont, C.T.S., and InSitu are marketing products for desulfating and the removal of calcareous encrustations.
- One of the most common targets for desulfation are calcium-containing salts, like calcium sulfate. Conservators concern themselves with these materials for several reasons. Salts like calcium sulfate are partially soluble in water, causing them to cycle through periods of solubility and re-crystallization within masonry exposed to external moisture sources. In stones with low porosity, the salts may accumulate on the surface and mix with atmospheric particles to form dark grey excretions. In stones with a higher porosity, the salts migrate through the surface. When it crystallizes, the force of the expansion causes mechanical compression, and can eventually lead to break-up of the stone surface. Environmental pollution is a major contributing factor to this sulfatation process, particularly in urban areas. Sulfur dioxide in the air reacts with moisture, oxygen, and calcium carbonate (limestone and marble) to create calcium sulfate dihydrate (gypsum). Due to the higher specific volume and solubility of calcium sulfate in comparison to calcium carbonate, calcium sulfate has the ability to incur a lot of damage in a relatively short period of time.