Determination of iodine in organic iodine compounds by the non-equilibrium isotopic exchange method

A new type of the isotope exchange method of analysis is proposed. The method can be applied to the exchange system in which the rate of the exchange reaction is rather slow but measurable, before the exchange equilibrium is attained. The validity of the principle of the method is verified experimentally with several exchange systems of RyI+KI^*⇌RyI^*+KI (RyI stands for alkyl, alkylene or benzyl iodide) type. The iodine content of the organic iodine compounds can be determined with an error of ±4%.     

Radiation effects on gaseous iodine at very low concentrations</p> </p>

Summary Exploratory experiments have been carried out to investigate the effects of gamma-radiation on iodine aerosols under various chemical conditions. The results indicate that iodide ions (I^-) in aerosol can be readily oxidized to I₂ and HIO, and some iodide ions may be converted to organic iodine when organic additives are present in the KI solution from which the aerosol is generated. The results also suggest that the chemical transformation of irradiated iodine aerosol depends on the chemical environment both carrier gas and iodide solution.</p> </p>     

Isotope exchange of iodine in iodide-iodate melts studied by radio paper chromatography

The isotopic exchange reaction of iodine in fused NaI–NaIO₃ and KI–KIO₃ systems, which does not proceed until the mixture is melted, is found to be almost instantaneous in homogeneous melts. The equilibrium is attained within a period of less than 5 min at a temperature 5°C above the melting temperature of each composition for both systems. No noticeable exchange is observed even after heating the samples for 30 min at a temperature 20°C below the corresponding melting point. A single-step bimolecular association-dissociation mechanism is proposed for the exchange.     

A simplified method for the amplification of iodine

The sample solution is treated so that all iodine is present in the elemental state. This iodine is extracted into chloroform and thereby separated with very high selectivity from almost any matrix. Until now, in order to apply amplification via oxidation to iodate and reaction with iodide, a reextraction into a sodium hydroxide solution was necessary. In the new procedure the organic phase is shaken with bromine water. Thereby, the iodate formed moves completely into the water phase while the bromine accumulates in the chloroform. Remaining bromine in the water is destroyed with some formic acid. No buffer is needed, because the acid establishes the correct conditions for this reaction and also that between iodate and iodide. The iodine formed in sixfold amount can now be titrated visually or photometrically with thiosulfate or subjected to a second amplification cycle. The new procedure eliminates the reextraction, and the addition of some reagents especially sodium hydroxide which is the main contributor of extraneous iodine. Thus, the blank is reduced by a factor of 10 or more and is also more constant. Iodine at lower levels (< 1 μg/ml) can be determined and with higher reliability.     

碘化法提金工艺中碘及碘离子连续测定研究

建立了一种碘化法提金液中碘及碘离子的连续测定方法,调节溶液酸度,用硫代硫酸钠滴定溶液中碘,在滴定完碘的溶液中,以曙红为指示剂,以硝酸银定量滴定溶液中的碘离子,扣除碘生成的碘离子即可得到溶液中的碘离子。采用定量模拟碘化法提金液验证方法的有效性,同时进行加标回收及精密度实验,加标回收率为98.1%~103%,相对标准偏差(RSD,n=10)在0.19%~0.67%,方法精密度好,可满足碘化提金液中碘及碘离子的分析测定。     

煤中碘的淋滤行为研究

用不同pH值溶液对煤进行动态淋滤实验,用电感耦合等离子体质谱(ICP-MS)测定不同pH值淋滤液在不同时间段获取的淋出液中碘的浓度,以及煤和淋滤后残留煤的高温热水解溶液中碘的含量。结果表明,淋滤液pH值、淋滤时间、煤中碘的赋存形态及在煤中的赋存部位对碘的淋出有重要影响。淋滤液的酸性越强,煤中碘的淋出越多,pH值为2.0和pH值为4.0溶液对煤中碘的淋出率(η)分别为7.22%和6.20%;但pH值为2.0溶液的淋出液中碘的量小于pH值为4.0溶液的淋出液中碘的量,其百分率(w_x)分别为1.920 0%和5.420 0%。pH 2.0淋滤液,在前30 h内淋出液中碘的平均浓度为10.9 μg/L;而pH值为4.0淋滤液,在前110 h内淋出液中碘的平均浓度为10.6 μg/L;pH值为6.0和pH值为7.5溶液能淋出煤中碘很少。在酸性溶液作用下,首先被淋出的碘是存在煤颗粒表面少量的水溶态和离子交换态碘及大部分碳酸盐态和铁锰氧化物结合态碘,然后煤基质内部的部分水溶态和离子交换态碘及少量的碳酸盐结合态及铁锰氧化物结合态碘等才被淋出。     

Separation of131I by isotopic and non-isotopic liquid ion exchange

A study is presented on the use of isotopic and non-isotopic ion exchange in a heterogeneous liquid-liquid system for the separation of¹³¹I from water. The method is based on the reaction between radioiodide in the aqueous phase and trioctylmethylammonium iodide or chloride in the organic phase. The effect of some important experimental parameters on the separation efficiency is discussed. It has been found that under optimum conditions the method of isotopic ion exchange can be used for the radiochemical determination of iodine in water.     

Anion-radical mechanism of bromine exchange by iodine in furan derivatives

The kinetics of bromine exchange by iodine in furan derivatives were studied; it is shown that the reaction is reversible and inhibited by oxidizing agents. Chloro derivatives of furan do not undergo this reaction. A cryptoreductive mechanism is proposed; the first stepof this mechanism consists of electron transfer to the halofuran molecule with subsequent reversible dissociation of the anion radical — inclusion of the iodide anion in the dissociation equilibrium leads to the substitution product.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1601–1606, December, 1976.     

The determination of bromine and iodine in environmental water samples by thermal neutron activation and isotope exchange

A routine-method for the determination of bromine and iodine in environmental water by neutron activation is presented. The elements are isolated by isotope exchange between the irradiated sample and a solution of Br₂ or I₂ CCl₄. The method is not sensitive to the chemical species in which the halogen is present. The lower limit of the determination is 1.0 μg Br·1⁻¹ and 0.1 μgI·1⁻¹.     

Immobilization of fission iodine by reaction with insoluble natural organic matter

Iodine-129 is a fission product and highly mobile in the environment. Along with other stable isotopes of iodine, ¹²⁹I is released during reprocessing of nuclear fuel and must be trapped to prevent the release of radioactivity to the environment. Past studies have provided evidence that iodine can become associated with natural organic matter (NOM). This research explores the use of NOM (sphagnum peat and humic acid) to sequester iodine from the vapor and aqueous phases. NOM-associated iodine may be stable for geological storage. NOM-sequestered iodine can be recovered by pyrolysis to prepare target materials for transmutation. The nature of the NOM-iodine association has been explored.     

Experimental and theoretical insights into copper phthalocyanine-based covalent organic frameworks for highly efficient radioactive iodine capture

Exploring efficient materials for capturing radioactive iodine in nuclear waste is of great significance for the progress of nuclear energy as well as the protection of ecological environment. Covalent organic frameworks (COFs) have emerged as promising adsorbents because of their predesignable and functionalizable skeleton structures. However, it remains a grand challenge to achieve large scale preparation of COFs. In this work, we developed a mild and efficient microwave irradiation method instead of the traditional solvothermal method to prepare copper phthalocyanine-based covalent organic frameworks (Cu_xPc-COFs) within only 15 min. The nitrogen-rich 1,2,4,5-tetracarbonitrilebenzene (TCNB) was selected as the solely organic ligand to construct copper phthalocyanine-based 2D conjugated COFs. The resultant Cu_xPc-COFs exhibited excellent iodine enrichment with 2.99 g/g for volatile iodine and 492.27 mg/g for iodine-cyclohexane solution, respectively, outperforming that of many porous materials. As indicated by spectroscopic analysis and DFT calculations, this impressive adsorption performance can be attributed to the charge transfer arising from nitrogen-rich phthalocyanine structures and electron-rich π-conjugated systems with iodine molecules. Moreover, the strong electrostatic interaction between Cu(II) on chelate centers and polyiodide anions (I_x^?) also play an important role in the firmly trapping radioactive iodine. Therefore, this study provides a facile and intelligent approach to implement metal-based COFs for the remediation of toxic radioactive iodine.     

Radiochemical studies of the retention of volatile iodine in aqueous solutions

Volatile molecular iodine and organic iodine species would be generated under radiation in the gas space and sump of nuclear power plant containments during a severe accident involving core melt. Engineered and currently installed safety systems might not effectively retain highly volatile iodine species. Fast and efficient conversion to non-volatile species within the containment would lower the potential risk of a significant release into the environment and therefore, methods must be sought to reduce iodine volatility to a minimum or, ideally, to remove it completely. This paper presents the results of an experimental programme to obtain a fast and efficient reduction of highly volatile organic iodide species in aqueous solution into iodide ions.     

Use of a heterogeneous isotope exchange method for preparation of rose bengal labelled by radioisotopes of iodine

A new method of preparation of rose bengal labelled by radioisotopes of iodine has been developed. The method is based on heterogeneous isotope exchange between rose bengal absorbed on a solid carrier and electrophilic species of radioiodine in HCl solutions. Low specific activity solutions can be used in the method. The method can also be used for preparation of other labelled derivatives of diiodofluorescein.     

Nano-structured calcium silicate hydrate functionalised with iodine

Nano-structured calcium silicate hydrate can physisorb or chemisorb iodine, making it interesting for medical or materials science applications, where a slow, controlled release of iodine is desired. It was found that iodine can be sorbed and released by applying the elemental halogen in solution, either as a gas or as a solid. At ambient temperatures the sorption and desorption process is quantitative and physical, meaning that the same amount of iodine is taken up and released. At temperatures above 32.5 °C (305.7 K) iodine reacts with the calcium silicate hydrate forming a complex, which is stable above the sublimation temperature of iodine. The formation energy for the iodine calcium silicate hydrate complex was established to be 41.8 ± 0.8 kJ mol⁻¹ by calorimetry and the nature of the complex was investigated using X-ray photoelectron spectroscopy.     

Isotope exchange of iodine between sodium iodide [Na131I] and [4-127I]iodoantipyrine via organic medium

The present investigation deals with a study of the isotope exchange reaction of iodine between sodium iodide [Na¹³¹I] and [4-¹²⁷I]iodoantipyrine in organic medium, using different iodinating radioiodine reagents of different carrier-iodine concentration. A maximum saturation yield over 90% of pure [4-¹³¹I]iodoantipyrine has been obtained by performing the isotope exchange reaction in ethanol at 80°C in 30 min. The same yield has been obtained using the same concentrations by performing the reaction at room temperature (17–20°C) for 3 h. Also the rate of the isotope exchange reaction was found to be carrier-iodine dependent as well as time and temperature dependent. According to these results and reaction conditions, a kit form method was elaborated for the synthesis of [4-¹³¹I]iodoantipyrine as well as [4-¹²³I]iodoantipyrine.     

Interaction of iodine species with glycogen at high concentrations of iodine

Glycogen–iodine (GI) complex formation has been studied at different concentrations of iodine and glycogen. For each glycogen concentration (0.25, 0.125, 0.0625, 0.0313 g/L), the iodine concentration was varied from 0.0317 to 1.59 g/L and the absorbance readings were taken at 453 and 560 nm (GI wavelengths of maximum absorbance). The 453 nm absorbance curves for the GI solution (GI complex and unreacted iodine), and that of the pure iodine solution (without glycogen) level off at a high iodine concentration, and give a peak in the subtracted curve. The 560 nm curves consistently increase in absorbance, and no peak is noticed in the subtracted curve. The spectra of concentrated iodine solutions in water and alcohol suggest the formation of neutral iodine clusters. We suggest that these iodine clusters do not react with glycogen, and that the GI complex formation takes place by the addition of I₂ molecules. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 927–931, 1997     

Simultaneous microdetermination of iodine and sulfur in organic compounds

A simple and rapid method for the simultaneous microdetermination of iodine and sulfur in organic compounds is described. The procedure utilizes the Schöniger flask method for the combustion, the iodide ions titration with 0.01 N mercuric perchlorate solution and diphenylcarbazone as indicator and the sulfate ions titration with 0.01 M barium perchlorate solution and dimethylsulfonazo III as indicator. The results obtained are in good agreement with calculated values.     

Determination of thiourea and its organic derivatives with iodine trichloride

Thiourea and its organic derivatives and thiosemicarbazide are determined in water, methanol or glacial acetic acid medium by reaction with an excess of iodine trichloride in the presence of mercuric chloride. The reaction is complete in 15 min. The excess of iodine trichloride is evaluated by adding potassium iodide and titrating the liberated iodine with thiosulphate. A variety of organic thioureas can be determined with an average accuracy and precision of 0.2%.     

Determination of formates by oxidation with iodine

A selective determination of formates based on oxidation with iodine at 100° in presence of potassium hydrogen tartrate, and final titration with thiosulphate solution, is described. The error is below 0.5% for 25–90 mg of formic acid. Few other organic acids interfere.     

Exchange of halogen bonded on aromatic core. Heterogeneous catalysis—I : Reaction mechanism of iodine exchange in o-iodobenzoic acid

Reaction mechanism of halogen exchange between arylhalogenide and halogenide anion is studied in a case when the aromatic core is inactivated with respect to the S_NAr substitution by other substituents. The exchange of iodine between o-iodobenzoic acid and ¹³¹I labelled NaI serves as a modelling reaction. The reaction was found to proceed heterogeneously on a glass surface. In the case of a rapid course of the surface reaction the reaction mechanism is more complicated and the equation derived by McKay cannot be applied for expressing the time dependence of the degree of isotopic exchange. Reaction mechanism was proposed for this reaction and compared with experimental data.