BASIC PHYSICAL AND CHEMICAL PROPERTIES OF REILLEX^TM-HPQ ANION EXCHANGE RESIN AND ITS SORPTION BEHAVIOR OF HALIDES IN AQUEOUS NITRIC ACID SOLUTION

ABSTRACT

The Reillex™-HPQ anion exchange resin has a good potential toward the pretreatment of liquid nuclear wastes. In this work, a short procedure was devised to convert 99.997% of the resin from its chloride form to the nitrate form as a foundation of all quantitative measurements. It is determined that the resin can be dried to a constant mass at 60°C in 28 hours and the electrostatic effect during weighings can hence be eliminated. The weight ratio between resins dried at 110°C and 60°C is 0.927±0.005 (one standard deviation). The resin has an apparent pK_a of 3.36±0.05. The sorption capacity from primarily the weakly basic ionogenic sites (RNH⁺) is 1.08±0.04 meq/g for resins dried at 60°C. In highly basic solutions, the resin became unstable and started to release a substantial amount of methanol. In nitric acid solutions, the selectivity sequence of halide ions versus nitrate and pertechnetate ions is: TcO₄ ⁻ > I⁻ > NO₃ ⁻ > Br⁻ > Cl⁻ > F⁻. The HPQ resin showed no sorption of fluoride ions. Although the sorption of chloride ions is also low the data can be modelled well by an equation similar to the Freundlich isotherm at a pH range between 2.0 and 3.0. Both bromide and iodide ions showed moderate sorptions when [HNO₃] ≤, 1.00 M and the sorption data can be fitted well to an equation closely related to the Temkin isotherm.