Behaviour of Ion Exchange Resins and Corrosion Inhibitors in Dilute Chemical Decontamination

Abstract

Ethylene diamine tetra acetic acid (EDTA) is a versatile complexing agent and is being employed in decontamination formulations. The dilute chemical decontamination (DCD) process employs ion exchange resins for regeneration of complexants, collection of metal ions/active isotopes and for removal of the decontaminating chemicals. In this work the interactions of EDTA on cation and anion exchange resins have been studied. The pickup of EDTA on cation exchange resin is by ion exchange mechanism and not possibly by precipitation at the low pH existing in ion exchange resin matrix. A mathematical relationship has been worked out to calculate the amount of EDTA adsorbed per unit volume of the cation exchange resin at a given pH. In addition, the behaviour of DTPA, HEEDTA and NTA on cation exchange resin has been evaluated. The chromatographic behaviour of OH- form of strong base anion exchange resin for a formulation containing EDTA, oxalic acid and citric acid has been reported and its relevance to the decontamination process has been discussed. Even though the corrosion rate of DCD is very low on most of the materials of construction, influence of time, temperature and the composition of the formulation on carbon steel is studied. Different classes of inhibitors were evaluated for reducing carbon steel corrosion.