Iodate

Abstract: In aqueous oxidative processes with ozone (O3), chlorine, or chloramine, naturally occurring iodide (I-) can easily be oxidized to hypoiodous acid (HOI) which can react with natural organic matter (NOM) or be further oxidized to iodate (IO3-). Such processes can be of importance for the geochemistry of iodine and for the fate of iodine in industrial processes (drinking water treatment, aquacultures). Whereas IO3- is the desired sink for iodine in drinking waters, iodoorganic compounds (especially iodoform, CHI3) are problematic due to their taste and odor. To assess the sink for iodine during oxidation of natural waters, we determined the kinetics of several oxidation reactions of HOI. Ozone, chlorine, and chloramine have been tested as potential oxidants. Ozone oxidized both HOI and hypoiodite (OI-) (kO3+HOI = 3.6 × 104 M-1 s-1; kO3+OI− = 1.6 × 106 M-1 s-1) in a fast reaction. Chlorine species oxidized HOI by a combination of second- and third-order reactions (k‘ ‘HOCl+HOI = 8.2 M-1 s-1; k‘ ‘‘HOCl+HOI = ...

Abstract: — A solution of 0.6 M iodide and 0.1 M iodate in 0.01 M borate buffer (pH 9.25) can be used as a chemical actinometer to measure the incident fluence from a low-pressure mercury lamp that puts out more than 85% of its energy at 254 nm. The actinometric solution is optically opaque to light below 290 nm and is optically transparent to wavelengths greater than 330 nm. Hence, the solution absorbs all of the germicidal wavelengths but little if any of the ambient light normally present in the laboratory. Iodate acts as an electron scavenger and prevents the back reaction of the free electron with the iodine atom following UV excitation of KI. Irradiation results in the linear formation of triiodide, which is quantitated by measuring its absorbance at 352 nm. The quantum yield for this system is approximately 0.75 0.03 at 20.7AoC or approximately three times greater than that obtained previously using nitrous oxide as an electron scavenger. A model is proposed to account for this difference. A precise expression to account for the concentration and temperature dependence of the quantum yield is given by pH = 0.75(1 + 0.23[C - 0.577])(1 + 0.02[T - 20.7]) where C is the concentration of iodide and T is the temperature. The concentration of iodide can be obtained from the absorbance at 300 nm prior to irradiation using 1.061 MJ cm−1 as the molar extinction coefficient. This actinometric system meets the quality criteria established by the International Union of Pure and Applied Chemistry with the caveat that it is designed to measure only germicidal radiation (i.e. wavelengths less than 290 nm).

Abstract: Three new molybdenyl iodates, KMoO3(IO3) (1), RbMoO3(IO3) (2), and CsMoO3(IO3) (3), have been prepared through the hydrothermal reactions of MoO3 with AIO4 (A = K, Rb, or Cs) at 180 °C. These compounds are isolated as nearly colorless, air-stable crystals. Single-crystal X-ray diffraction experiments reveal that 1 possesses a corrugated layered structure constructed from molybdenum oxide chains that are bridged by iodate anions. The puckering of the layers is caused by the alignment of bent molybdenyl (MoO22+) groups along one side of the molybdenum oxide chains. The K+ cations separate these layers from one another and serve to balance charge. In contrast, compounds 2 and 3, which are isostructural, form three-dimensional structures with small cavities filled with Rb+ or Cs+ cations. The differences between the structures of 1 and those of 2 and 3 are due to rotation of the molybdenyl units as translation occurs down the molybdenum oxide chains in order to accommodate the increased size of the Rb+ and Cs...

Abstract: Potassium periodate (PI, KIO4) was readily activated by Fe(II) under acidic conditions, resulting in the enhanced abatement of organic contaminants in 2 min, with the decay ratios of the selected pollutants even outnumbered those in the Fe(II)/peroxymonosulfate and Fe(II)/peroxydisulfate processes under identical conditions. Both 18O isotope labeling techniques using methyl phenyl sulfoxide (PMSO) as the substrate and X-ray absorption near-edge structure spectroscopy provided conclusive evidences for the generation of high-valent iron-oxo species (Fe(IV)) in the Fe(II)/PI process. Density functional theory calculations determined that the reaction of Fe(II) with PI followed the formation of a hydrogen bonding complex between Fe(H2O)62+ and IO4(H2O)-, ligand exchange, and oxygen atom transfer, consequently generating Fe(IV) species. More interestingly, the unexpected detection of 18O-labeled hydroxylated PMSO not only favored the simultaneous generation of ·OH but also demonstrated that ·OH was indirectly produced through the self-decay of Fe(IV) to form H2O2 and the subsequent Fenton reaction. In addition, IO4- was not transformed into the undesired iodine species (i.e., HOI, I2, and I3-) but was converted to nontoxic iodate (IO3-). This study proposed an efficient and environmental friendly process for the rapid removal of emerging contaminants and enriched the understandings on the evolution mechanism of ·OH in Fe(IV)-mediated processes.