2014-08

2014-08

Alkaline solutions soaking are the most accepted treatment for the desalination of archaeological iron in an attempt to arrest further detrimental corrosion. The process displaces chloride ions (desalination) and diffuses them out of the artifact. The method relies on high concentrations of hydroxide and low concentrations of chloride in the solution. As the treatment progresses, chloride concentration increases decreasing desalination rates and the technique’s effectiveness. Conservators cope with this issue by regularly replacing solutions. This procedure generates significant quantities of waste, and requires personnel and considerable amounts of water and sodium hydroxide. The proposal aimed at investigating the applicability of ion-exchange technology to remove chloride from solution without the need to constantly replace the soaking solutions.

Depending on the volume, mass, shape, composition and condition of the artifacts, hundreds if not thousands of gallons of NaOH solution may be required to optimize and maintain the chloride concentration gradient between the artifact and the treatment solution. It is believed that where an ion-exchange resin is employed, the recirculating solution ensures a constant pH and a maximum chloride release, resulting in a decrease in overall treatment times. The recycle-ability introduced by the utilization of resin would allow for an unprecedented development opportunity for stabilization treatments. A single volume of solution would be continuously recirculated through the resin bed, allowing for considerable reduction in the amount of treatment solution produced and subsequently disposed of, therefor drastically reducing labor, cost and health and safety issues. These benefits would also be applicable to the subcritical treatment resulting in significant up-scaling of the technique. Reductions in volume of solution needed would possibly allow larger artifacts, such as cannon to be treated. Due to their regeneration capability (life-cycle of 5-10 years), ion-exchange systems provide an environmentally friendly, cost-effective and sustainable treatment option for the desalination of metallic cultural heritage.

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