Establishment Of Iodine Speciation Analysis Method And Removal Of Iodine In Aqueous By Iron(Hydro)Oxide

Iodine is a very important element, which widely distributed in the atmosphere, water, rock and soil. It is closely related to people’s physical health. General thyroid disease was owing to lack of iodine. Human being intaking excessive iodine also get spordic and reginational thyroid disease. The radioactive iodine not only cause irreversible damage to the thyroid, but also illuminate human respiratory tract, digestive tract, blood and other systems causing distortion and cancer. The radioactive iodine in the environment is mainly derived from human social activities. As the shortage of world’s energy, the development of nuclear energy has become the preferred strategic objective in many countries. In addition, the extensive application of radioactive iodine in medicine, biology, agriculture and industry also brings radioactive iodine pollution. Therefore, it is of great significance to accurately determine different forms of iodine to deal with the radioactive iodine of waste solid and waste water, to comprehensively utilize iodine and to prevent human being from the harm radioactive iodine. In this study, the speciation analysis method of iodine had been established and the iron (hydro) oxide had been prepared and screened and been applied to adsorb and remove iodine in aqueous. The main research work was as follows:The methods of ultraviolet spectroscopy and ion chromatography in determination of different speciations of iodine were established. The optimized conditions of ultraviolet spectrometry to detect iodate was that:0.2 mL 20% phosphoric acid solutionlmL 100 g/L KI solution was added, then the solution was placed in in the dark for 30 min at room temperature. The absorbance was detected at the wavelength of 350 nm with reagent blank used as reference. The optimized conditions of detection iodine was that:3 drops of bromine was used to oxidate iodine to iodate,0.5 mL 10% formic acid solution was used to remove excessive bromine water and then 2 mL of 20% phosphoric acid and 1 mL 100 g/L KI solution was added, then the solution was placed in the dark for 30 min at room temperature. The absorbance was detected at the wavelength of 350 nm with the reagent blank used as reference. The linear range of I" and IO3- were 0-1.2 mg/L and 0-1.5 mg/L with the determination limit of 1.54μg/L(I-) and 14.8μg /L(IO3-) respectively. The reagent and instrument condition of ion chromatography to detect I- and IO3- were that:The conductivity range was 30μs, the restrain current was 50 mA, and 1.7 mmol/LNaHCO3 and 2.4 mmol/L Na2CO3 were used as eluent, and the velocity was 1.00 mL/min. The linear range of I- and IO3- were 0-50 mg/L with the determination limit of 0.4482 mg/L(I-) and 0.5214 mg/L(IO3-), respectively. The determination method of methyl iodine was studied thought tetraethylenepentamine derivation. The optimal condition of methyl iodide derivation was that:the molar ratio of tetraethylenepentamine to methyl iodide was 5:1, the reaction time was 90 min and reaction temperature was 60℃. The linear range of methyl iodide was 0-112 mg/L with the detection limit of 3.87 mg/L.The result shows that iodine was prone to absorbed by α-FeOOH and iodate was easily absorbed by β-FeOOH The adsorption materials α-FeOOH and β-FeOOH were prepared and optimizated. The preparation conditions of α-FeOOH was that:0.05 mol/L NaOH was droped into 0.05 mol/L Fe(NO3)3 solution until the pH of solution turn to 7, then the solution was aged for two days at 60℃, filtered, dried, washed and dried. The preparation conditions of β-FeOOH was that:0.05 mol/L NaOH was droped into 0.05 mol/L FeCl3 solution until the pH of solution turn to 7, then the solution was aged for two days at 60℃, filtered, dried, washed and dried.The adsorption conditions and saturated adsorption capacity of the α-FeOOH to iodine and β-FeOOH to iodate were discussed. The saturated adsorption capacity of α-FeOOH to iodine was 21.68 mg/g in the condition of that the solid-liquid ratio was 1:165, the adsorption time was 30 min at room temperature and at the pH of 7. The saturated adsorption capacity of β-FeOOH to iodate was 99.94 mg/g in the condition of that solid-liquid ratio was 1:165, the adsorption time was 180 min at room temperature and at the pH of 7. The adsorption thermodynamics of α-FeOOH to I- and β-FeOOH to IO3- were studied. The result showed that the adsorption of α-FeOOH to I- was spontaneous, exothermic and physical reaction, the adsorption of β-FeOOH to IO3- was belonged to spontaneous, endothermic and chemical reaction.