High efficiency removal of organic and inorganic iodine with ferrate[Fe(VI)] through oxidation and adsorption

I⁻ is a halogen species existing in natural waters, and the transformation of organic and inorganic iodine in natural and artificial processes would impact the quality of drinking water. Herein, it was found that Fe(VI) could oxidize organic and inorganic iodine to IO₃⁻and simultaneously remove the resulted IO₃⁻ through Fe(III) particles. For the river water, wastewater treatment plant (WWTP) effluent, and shale gas wastewater treated by 5 mg/L of Fe(VI) (as Fe), around 63 %, 55 % and 71 % of total iodine (total-I) had been removed within 10 min, respectively. Fe(VI) was superior to coagulants in removing organic and inorganic iodine from the source water. Adsorption kinetic analysis suggested that the equilibrium adsorption amount of I⁻ and IO₃⁻ were 11 and 10.1 μg/mg, respectively, and the maximum adsorption capacity of IO₃⁻ by Fe(VI) resulted Fe(III) particles was as high as 514.7 μg/mg. The heterogeneous transformation of Fe(VI) into Fe(III) effectively improved the interaction probability of IO₃⁻ with iron species. Density functional theory (DFT) calculation suggested that the IO₃⁻ was mainly adsorbed in the cavity (between the γ-FeOOH shell and γ-Fe₂O₃ core) of Fe(III) particles through electrostatic adsorption, van der Waals force and hydrogen bond. Fe(VI) treatment is effective for inhibiting the formation of iodinated disinfection by-products in chlor(am)inated source water.