CL Resin

CL Resin, used for the separation of chloride and iodide, is based on an extractant selective for the platinum group metals, gold and silver. The selectivity for halides is introduced by loading the resin with silver(I) ions.

For practical reasons, sulfuric acid was chosen as extraction medium. The CL Resin has high selectivity for Pd(II) and Ag(I), whereas the DW values of the other tested metal ions are low. DW values for Ag(I) remain high over a wide pH range (from 1M H2SO4 to dilute sulfuric acid, pH 5). Ag(I) is therefore extracted and remains fixed on the resin over a wide range of pH values.

The loading of the CL Resin with silver cations provides the mechanism for selectivity of halides which form sparingly soluble complexes with Ag(I). DW values for chloride and iodide on the silver loaded CL Resin in 1M H2SO4 were determined to be 1600 and 1980, respectively. Iodine and chloride are thus well retained under those conditions. The CL Resin used for the DW experiments was loaded with 20 mg Ag(I) per gram of CL Resin prior to the extraction experiments, which corresponds to a typical working capacity for the CL Resin. The capacities for chloride and iodide of the silver loaded resin under these conditions are: 16.3 +/- 1.6 mg iodide per 2 mL column (approx. 25 mg iodide per g resin) and 4.3 +/- 0.2 mg chloride per 2 mL column (approx. 6.5 mg chloride per g resin). Higher capacities for halides may be obtained by increasing the silver load of the CL Resin.

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