Recovery of Iodine as Triiodide by Strongly Basic Anion Exchange Resins; Development of Chromatographic Method

The present study outlines a general process to recover iodine from brine water or wastewater by strongly basic anion exchange resins. At first, iodide anions were oxidized to iodine or triiodide (the appropriate amount of H2O2 and HCl was added to the solution to adjust the Eh and pH). The static capacity of the resin obtained from isotherm experiments (D-R model) was equal to 2413.6 mg/g (pH=2 and H2O2 concentration = 3.3 times higher than the stoichiometry amount). The pseudo-second-order kinetics showed an excellent agreement with kinetics data. The results of Kinetics and isotherm studies for iodide adsorption (without pre-oxidation) showed the same mechanism with lower static capacity (466.3 mg/g). The dynamic iodine adsorption capacity of the resin was 2233.8 mg/g (weight  of dry resin = 2 g, length of bed = 10 cm, and flow rate of solution = 5 mL/min). Three common models, including the Yoon-Nelson, Thomas, and Dose-Response models, were fitted on the experimental data for breakthrough curve studies. The operational parameters of the length of the column, the flow rate of the solution, and the initial concentration of iodine were optimized, too. NaOH and NaCl solutions were used for the iodine desorption and the recovery of the resin. Using this process, about all of the iodine was adsorbed by the resin, and more than 99% of desorbed iodine in the eluent solution was precipitated (pH =2.4). Finally, and after drying, the solid iodine was obtained and the purity of it was higher than 99%.