Iodate Ions Research Articles

Removal of iodide from water by chlorination and subsequent adsorption on powdered activated carbon

Chlorine oxidation followed by treatment with activated carbon was studied as a possible method for removing radioactive iodine from water. Chlorination time, chlorine dose, the presence of natural organic matter (NOM), the presence of bromide ion (Br−), and carbon particle size strongly affected iodine removal. Treatment with superfine powdered activated carbon (SPAC) after 10-min oxidation with chlorine (1 mg-Cl2/L) removed 90% of the iodine in NOM-containing water (dissolved organic carbon concentration, 1.5 mg-C/L). Iodine removal in NOM-containing water increased with increasing chlorine dose up to 0.1 mg-Cl2/L but decreased at chlorine doses of >1.0 mg-Cl2/L. At a low chlorine dose, nonadsorbable iodide ion (I−) was oxidized to adsorbable hypoiodous acid (HOI). When the chlorine dose was increased, some of the HOI reacted with NOM to form adsorbable organic iodine (organic-I). Increasing the chlorine dose further did not enhance iodine removal, owing to the formation of nonadsorbable iodate ion (IO3−). Co-existing Br− depressed iodine removal, particularly in NOM-free water, because hypobromous acid (HOBr) formed and catalyzed the oxidation of HOI to IO3−. However, the effect of Br− was small in the NOM-containing water because organic-I formed instead of IO3−. SPAC (median particle diameter, 0.62 μm) had a higher equilibrium adsorption capacity for organic-I than did conventional PAC (median diameter, 18.9 μm), but the capacities of PAC and SPAC for HOI were similar. The reason for the higher equilibrium adsorption capacity for organic-I was that organic-I was adsorbed principally on the exterior of the PAC particles and not inside the PAC particles, as indicated by direct visualization of the solid-phase iodine concentration profiles in PAC particles by field emission electron probe microanalysis. In contrast, HOI was adsorbed evenly throughout the entire PAC particle.

A possible candidate to be classified as an autocatalysis-driven clock reaction: kinetics of the pentathionate-iodate reaction.

The pentathionate-iodate reaction has been investigated by spectrophotometrically monitoring the formation of the total amount of iodine at 468 nm in the presence of phosphoric acid/dihydrogen phosphate buffer. We noticed that iodine forms only after a fairly long time lag, and the inverse of time necessary to produce a certain amount of iodine is linearly proportional to the initial concentration of iodate ion and the square of the hydrogen ion concentration, while depending complexly on the concentration of substrate pentathionate. This reaction can therefore be treated as a clock reaction but differs from the original Landolt reaction in the sense that substrate pentathionate and the clock species iodine coexist for a relatively long time--due to their relatively slow direct reaction--depending on the experimental circumstances. Furthermore, we also provided experimental evidence that iodide ion acts as an autocatalyst of the system. A 14-step kinetic model is proposed in which the mechanisms of the pentathionate-iodine, bisulfite-iodate, and the well-known Dushman reactions are combined. A thorough analysis revealed that the direct pentathionate-iodate reaction plays a role only to produce iodide ions via a finite sequence of reactions, and once its concentration reaches a certain level, the reaction is almost exclusively governed by the pentathionate-iodine and the Dushman reactions. As expected, a strong catalytic effect of the buffer composition is also found that can readily be explained by its well-known catalytic influence on the original Dushman reaction.

Highly Efficient Water Oxidation on Rutile Titanium(IV) Oxide Powder in the Presence of Iodate Ions as Reversible Electron Acceptors

Abstract A high apparent quantum yield (AQY) of 25 ± 1% (at 365 nm) for water oxidation in the presence of iodate ions was achieved using a rutile titanium(IV) oxide that has relatively low density of surface defects.

Aspects of Periodate Oxidation of Carbohydrates for the Analysis of Pyrolysis Liquids

Periodate oxidation of carbohydrates in acid, neutral, and alkaline media has been studied in order to develop a simple and fast determination method of sugars and their derivatives, such as levoglucosan, in fast pyrolysis liquids. The carbohydrates oxidized are as follows: D-glucose, D-cellobiose, D-cellotriose, D-fructose, D-sucrose, and levoglucosan. The reaction products have been analyzed with two methods: iodometric titration for iodate ions and potentiometric titration for formic acid.

Effect of chemical reaction causing contact angle variation, on the spontaneous motion of an I2-containing nitrobenzene droplet

Spontaneous motion of nitrobenzene droplet including only iodine (potassium iodide-free) in cation surfactant aqueous solution was investigated. For quantitative clarification of the motion mechanism, the contact angle of droplet and the concentrations of iodic components in this system, i.e. I2, I−, IO3−, and I3−, were measured. A disproportionate reaction of iodine in the alkaline conditions to produce iodide and iodate ions was identified, inducing the reduction of the droplet contact angle. A significant relation between running distance of spontaneous droplet motion and the droplet contact angle was found. The mechanism of motion was discussed based on these results.

Simultaneous determination of free and total glycerol in biodiesel by capillary electrophoresis using multiple short‐end injection

A rapid method for the simultaneous determination of free glycerol (FG) and total glycerol (TG) in biodiesel by CE using a short-end multiple injection (SE/MI) configuration system is described. The sample preparation for FG involves the extraction of glycerol with water and for TG a saponification reaction is carried out followed by extraction as in the case of FG. The glycerol extracted in both cases is submitted to periodate oxidation and the iodate ions formed are measured on a CE-SE/MI system. The relevance of this study lies in the fact that no analytical procedure has been previously reported for the determination of TG (or of FG and TG simultaneously) by CE. The optimum conditions for the saponification/extraction process were 1.25% KOH and 25°C, with a time of only 5 min, and biodiesel mass in the range of 50.0-200.0 mg can be used. Multiple injections were performed hydrodynamically with negative pressure as follows: 50 mbar/3s (FG sample); 50 mbar/6s (electrolyte spacer); 50 mbar/3s (TG sample). The linear range obtained was 1.55-46.5 mg/L with R(2) > 0.99. The LOD and LOQ were 0.16mg/L and 0.47mg/L, respectively for TG. The method provides acceptable throughput for application in quality control and monitoring biodiesel synthesis process. In addition, it offers simple sample preparation (saponification process), it can be applied to a variety biodiesel samples (soybean, castor, and waste cooking oils) and it can be used for the determination of two key parameters related to the biodiesel quality with a fast separation (less than 30 s) using an optimized CE-SE/MI system.

Double beryllium iodate dihydrates, M2Be(IO3)4·2H2O (M = K, NH4+, Rb): Preparation, X-ray powder diffraction and vibrational spectra

The solubilities in the three-component systems MIO3–Be(IO3)2–H2O (M=K, NH4+, Rb, Cs) were studied at 25°C by the method of isothermal decrease of supersaturation. It has been established that double salts, K2Be(IO3)4·2H2O, (NH4)2Be(IO3)4·2H2O, and Rb2Be(IO3)4·2H2O, crystallize from the ternary solutions within wide concentration ranges. Both the X-ray powder diffraction and the spectroscopic studies (infrared and Raman) reveal that the title compounds are isostructural. They crystallize in the monoclinic space group P2/m with lattice parameters: K2Be(IO3)4·2H2O – a=14.218(5)Å, b=6.747(2)Å, c=5.765(2)Å, β=98.74(4)°, V=546.6(2)Å3; (NH4)2Be(IO3)4·2H2O – a=14.414(4)Å, b=6.838(2)Å, c=5.947(2)Å, β=99.52(4)°, V=578.0(2)Å3; Rb2Be(IO3)4·2H2O – a=14.423(4)Å, b=6.867(2)Å, c=5.743(3)Å, β=98.15(3)°, V=562.9(3)Å3.Infrared spectroscopic experiments show that comparatively strong hydrogen bonds are formed in the potassium and rubidium salts as deduced from the wavenumbers of νOD of matrix-isolated HDO molecules (isotopically dilute samples) owing to the strong Be–OH2 interactions (synergetic effect). However, the IO3− ions in the ammonium compound are involved in hydrogen bonds with NH4+ ions additionally to those with water molecules and as a result of these intermolecular interactions the proton acceptor strength of the iodate ions decreases (anti-cooperative effect), thus leading to the formation of weaker hydrogen bonds in this compound (bonds of moderate strength) as compared to those formed in the potassium and rubidium ones. The normal vibrations of other entities (IO3− ions and BeO4 tetrahedra (skeleton vibrations)) are also discussed.

Diazotization-coupling reaction-based selective determination of nitrite in complex samples using shell-isolated nanoparticle-enhanced Raman spectroscopy

A simple, rapid and selective method based on diazotization-coupling reaction for determination of nitrite ion in complex samples using shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) was developed. Based on diazotization-coupling reaction, nitrite was transformed into azo dye, which has strong SHINERS activity. Subsequently the concentration of nitrite ion can be determined indirectly from the SHINERS of azo dye. The SHINERS active substrate was composed of gold nanoparticle as core with an ultrathin silica shell having pinhole on the surface. Various factors that influence reaction and SHINERS intensity were investigated. Under the optimal conditions, the linearity was observed in the range of 0.5–6.0mgL−1 with good correlation coefficient (r2>0.9793). The relative standard deviations (RSDs) for five replicate measurements were less than 14.5%. The limit of detections of the method (S/N=3) were 0.07, 0.08 and 0.10mgL−1 at 1137, 1395 and 1432cm−1, respectively, without sample preconcentration. The selectivity of the proposed method was also tested. The performance of SHINERS to determine the concentration of nitrite in food, biological and environmental samples was evaluated. The results indicate that SHINERS shows great potential as a useful analytical tool for trace analysis of nitrite in real samples. This proposed method provides a practical protocol for determination of compounds with weak Raman response, and can be expanded for the indirect detection of iodate ion, phenols and aromatic amines.

A simple and sensitive analytical method for the determination of thiamine in pharmaceutical preparations

A simple and sensitive method for spectrophotometric determination of thiamine with leucocrystal violet was elaborated. Spectrophotometric quantification based on the following reaction sequence: thiamine was oxidized with potassium iodate(V) to the colourless product and a stoichiometric amount of iodide ions was formed. The latter reacted with the excess of iodate(V) ions in acidic medium, to form free iodine which oxidized leucocrystal violet to the crystal violet dye. The absorbance of the crystal violet dye formed was measured at pH 4.1 ± 0.1 and 589 nm. The measured absorbance obeyed Beer’s law over the thiamine concentration range 0.4-2.4 μg/mL. The linear regression coefficients were a = 0.3339, b = −0.0001, and r = 0.9998 (for the general form of the linear equation y = ax + b). The apparent molar absorptivity of the coloured compound was 1.12 × 105 L/mol cm for thiamine. The limit of detection and limit of thiamine determination were found to be 0.19 and 0.26 μg/mL, respectively. Optimum reaction conditions providing maximum and constant absorbance were optimized. The procedure was successfully used to the determination of vitamine B1 in pharmaceutical formulations. The obtained results were compared with those obtained by the method proposed by Polish Standard.

Hydrogen and Oxygen Evolution Photocatalysts Synthesized from Strontium Titanate by Controlled Doping and Their Performance in Two-Step Overall Water Splitting under Visible Light

A visible-light-induced two-step overall water splitting was achieved by combining two types of photocatalysts prepared by introducing foreign elements into the identical mother structure with a controlled electronic band structure. Strontium titanate (SrTiO3) was selected as the mother structure and was doped with either vanadium (and sodium) or rhodium to introduce visible light sensitivity. By utilizing these two types of SrTiO3-based photocatalysts, simultaneous liberation of hydrogen (H2) and oxygen (O2) with a molar ratio of ∼2:1 was achieved in the presence of iodate ion (IO3–)/iodide ion (I–) as a redox mediator under irradiation with only visible light (>420 nm).

Visible-light-driven nonsacrificial water oxidation over tungsten trioxide powder modified with two different cocatalysts

Tungsten trioxide (WO3) powder was studied as a photocatalyst for water oxidation under visible light (λ > 420 nm). WO3 modified with nanoparticulate Pt species (more specifically, PtOx) as cocatalysts is capable of photocatalyzing water oxidation under visible light in the presence of iodate (IO3−) ions as an electron acceptor under near-neutral pH conditions (pH ≈ 5.9). When PtOx/WO3 was further modified with a very small amount (0.001 wt%) of a metal oxide (e.g., MnOx, CoOx, RuO2 or IrO2) as a secondary cocatalyst, the water oxidation activity was improved. Among the metal oxide cocatalysts examined, RuO2 was found to give the highest performance, with an apparent quantum yield of 14.4% at 420 nm. The results of photocatalytic reactions and photoelectrochemical analyses suggest that the main roles of the loaded PtOx and RuO2 on WO3 are to promote the reduction of IO3− and water oxidation, respectively.

Characterization of Intracellular Iodine Accumulation by Iodine-Tolerant Microalgae

Abstract High iodine concentrations are thought to be toxic to algal growth. However, in this study, among tested 10 algae, 6 species (Bellerochea sp., Chlamydomonas reinhardtii, Dunaliella tertiolecta, Isochrysis galbana, Skeletonema costatum, Tetraselmis sp.) exhibited high iodine tolerance and 2 species showed positive growth responses (Emiliania huxleyi, Gephyrocapsa oceanica). On the other hand, growth of Chlorella kessleri and Chaetoceros sociale were strongly inhibited. Interestingly, the effect of iodine differed among algal species and between the molecular forms of iodine, namely iodide (I−) or iodate (IO3−) ions. Neutron activation analysis indicates that E. huxleyi intracellularly accumulated more iodine when grown in KIO3 than when grown in KI. Such high intracellular iodine accumulation may stimulate the growth. Moreover, E. huxleyi accumulated ca.10 times more iodine than that found in seawater, suggesting that microalgae can be used in iodine-related industries for extracting iodine from seawater and iodine-containing wastewater.

Determination of Inorganic Anions by Capillary Ion-exchange Chromatography Using Polyethylenimine-coated Octadecyl-bonded Phases

The utility of a cationic polymer polyethylenimines (PEI) for coating some commercially available silica-based stationary phases packed in capillaries of 0.32 mm i.d. and 10 cm long was studied for the separation and direct UV detection of inorganic anions (iodate, bromate, nitrite, bromide, and nitrate ions). With a super-endcapped octadecylated silica stationary phase, which yielded the best separation in terms of resolution and retention time of individual anions, the effect of the pH and composition of the eluent on the elution behavior of individual anions was studied. The relative standard deviations of the retention time, peak area and peak height for 60 successive injections (running time of more than 10 h) were not more than 1.32, 2.30 and 1.94, respectively, with the exceptions of the peak area and peak height of the bromate ion. The detection limits at 210 nm ranged from 1 to 7 ppm. This method was successfully applied to determine concentrations of nitrate ions present in pills and beverage samples.

Determination of iodate in food, environmental, and biological samples after solid-phase extraction with Ni-Al-Zr ternary layered double hydroxide as a nanosorbent.

Nanostructured nickel-aluminum-zirconium ternary layered double hydroxide was successfully applied as a solid-phase extraction sorbent for the separation and pre-concentration of trace levels of iodate in food, environmental and biological samples. An indirect method was used for monitoring of the extracted iodate ions. The method is based on the reaction of the iodate with iodide in acidic solution to produce iodine, which can be spectrophotometrically monitored at 352 nm. The absorbance is directly proportional to the concentration of iodate in the sample. The effect of several parameters such as pH, sample flow rate, amount of nanosorbent, elution conditions, sample volume, and coexisting ions on the recovery was investigated. In the optimum experimental conditions, the limit of detection (3s) and enrichment factor were 0.12 μg mL−1 and 20, respectively. The calibration graph using the preconcentration system was linear in the range of 0.2–2.8 μg mL−1 with a correlation coefficient of 0.998. In order to validate the presented method, a certified reference material, NIST SRM 1549, was also analyzed.

Spectrophotometric method for the determination of ketoconazole based on amplification reactions

This paper describes a sensitive spectrophotometric method developed for determination of Ketoconazole (KC) in tablets based on amplification reactions. Ketoconazole was oxidized with periodate, resulting in formation of KC2+ and iodate ions. After masking the excess periodate with molybdate, the iodate was treated with iodide to release iodine. The liberated iodine was transformed to ICl2− species and extracted as ion-pair with rhodamine 6G into toluene for spectrophotometric measurement at 535nm. A linear calibration graph was obtained between 0.2136μg/mL and 1.7088μg/mL of Ketoconazole with a molar absorptivity of 5×105mol·L−1cm−1. The procedure was successfully applied for the determination of ketoconazole in tablet formulation.

Is Iodate a Strongly Hydrated Cation?

We show, through a combination of density function theory-based molecular dynamics simulations (DFT-MD) and experimental X-ray absorption fine structure spectroscopy (XAFS) studies, that the iodate ion (IO3–) contains a local region that is strongly hydrated as a cation. The local region adjoining the I atom is sufficiently electropositive that three hydrating waters are oriented with their O atoms directly interacting with the iodine atom at an I–OH2O distance of 2.94 Å. This is the orientation of water hydrating a cation. Further, approximately 2–3 water molecules hydrate each O of IO3– through their H atoms in an orientation of the water that is expected for an anion at an I–OH2O distance of 3.83 Å. We predict that this structure persists, although to a much lesser degree, for BrO3–, and ClO3–. This type of local microstructure profoundly affects the behavior of the “anion” at interfaces and how it interacts with other ionic species in solution.

Spectrophotometric determination of L-ascorbic acid in pharmaceuticals

A simple and sensitive spectrophotometric method for the determination of L-ascorbic acid with leuco crystal violet is proposed. The determination is based on the oxidation of analyte by potassium iodate. The colourless oxidation products were formed in the quantity equivalent to iodide ions. The iodide ions react with the excess of iodate ions in acidic medium, to form free iodine which oxidized leuco crystal violet (LCV) to the liberated crystal violet (CV +) dye, showing maximum absorption at 588 nm. The absorbance was measured at pH of 4.1–4.2 in 1 cm cuvettes. Beer’s law was obeyed in the concentration range 0.5–4.0 μg/mL. The molar absorptivity of the coloured compound is 4.14 × 104 L/mol cm for L-ascorbic acid. The analytical parameters were optimized and the method was successfully applied to the determination of L-ascorbic acid in pharmaceuticals. The results were compared with those obtained by methods proposed in Polish Standard.

Ultrasound-Assisted Synthesis of Hybrid Phosphomolybdate–Polybenzidine Containing Silver Nanoparticles for Electrocatalytic Detection of Chlorate, Bromate and Iodate Ions in Aqueous Solutions

Herein, we report a hybrid electroactive material composed of silver nanoparticle-embedded polybenzidine matrix containing phosphomolybdic acid as the active inorganic component by an ultrasound-assisted method for the electrochemical detection of chlorate, bromate and iodate ions in aqueous solutions. The prepared hybrid material was characterised for its physicochemical properties: X-ray diffraction and transmission electron microscopy analyses provided evidence for the presence of silver nanoparticles (∼12 nm) in the hybrid material. The synthesized hybrid material was successfully fabricated on a glassy carbon electrode, and cyclic voltammetry was used to probe its electrochemical properties in 1 M H2SO4 solution. Amperometry was employed in order to find out the detection limits of chlorate, bromate and iodate ions in aqueous solutions. This hybrid electrochemical interface showed the lowest detection limits of 86.3 nM, 1.45 μM and 1.66 μM for bromate, iodate and chlorate, respectively. Phosphomolybdate anion (PMo12) present in the hybrid material acted as both effective mediator and the source of mobile protons at the electrochemical interface. Silver nanoparticles present in the hybrid material further influenced the electroactivity of the modified electrode.

Quantitative determination of some water-soluble B vitamins by kinetic analytical method based on the perturbation of an oscillatory reaction

A novel procedure for kinetic determination of some water-soluble vitamins of the B-group (thiamine (B1), riboflavin (B2), niacin (B3) and pyridoxine (B6)) by the concentration perturbations of the Bray-Liebhafsky (BL) oscillatory chemical system involving the catalytic decomposition of hydrogen peroxide in the presence of both hydrogen and iodate ions is proposed and validated. The method uses a Pt electrode for potentiometric monitoring of the concentration perturbations of the BL matrix in a stable non-equilibrium stationary state close to the bifurcation point. The proposed method relies on the linear relationship between maximal potential displacements, ΔEm, caused by the additional known quantities of a B species. Under the optimal established analytical conditions, linear calibration curves were obtained over the range of 0.01-1.0, 0.016-0.128, 5.0-50.0 and 0.05-2.5 μmol with the limits of detection of 0.01, 0.018, 2.6 and 0.03 μmol, as well as analytical throughput of 30, 5, 12 and 20 determinations per hour, for B1, B2, B3 and B6, respectively. The used technical approach also provides simple, effective and convenient method to assay the pharmaceutical formulations containing B1 together with other active principles such as nicotinamide and vitamin B12 as well as B3.

Structures of chaos in open reaction systems

By numerically simulating the Bray-Liebhafsky (BL) reaction (the hydrogen peroxide decomposition in the presence of hydrogen and iodate ions) in a continuously fed well stirred tank reactor (CSTR), we find "structured" types of chaos emerging in regular order with respect to flow rate as the control parameter. These chaotic "structures" appear between each two successive periodic states, and have forms and evolution resembling to the neighboring periodic dynamics. More precisely, in the transition from period-doubling route to chaos to the arising periodic mixture of different mixed-mode oscillations, we are able to recognize and qualitatively and quantitatively distinguish the sequence of "period-doubling" chaos and chaos consisted of mixed-mode oscillations (the "mixed-mode structured" chaos), both appearing in regular order between succeeding periodic states. Additionally, between these types of chaos, the chaos without such recognizable "structures" ("unstructured" chaos) is also distinguished. Furthermore, all transitions between two successive periodic states are realized through bifurcation of chaotic states. This scenario is a universal feature throughout the whole mixed-mode region, as well as throughout other mixed-mode regions obtained under different initial conditions.