Interaction of radioactive iodine gaseous species with nuclear-grade activated carbons

Carbons from different sources and impregnations were systematically exposed to unfiltered outdoor air and all degraded with respect to radioactive methyl iodide trapping efficiency. The same carbons, exposed to air flows of known contaminant species and concentrations under controlled laboratory conditions, behaved similarly. Local meteorological conditions of high humidity combined with atmospheric pollutants in the test vicinity contributed jointly to the degradation. When service activated carbons were exposed to radiation levels of 10⁷–10⁹ rads, the iodine isotope exchange capacity was regenerated. The efficiency for iodine isotope exchange was vastly improved, but the removal of methyl iodide-127 was only slightly improved or not at all. It was possible to regenerate the iodine isotope-exchange efficiency by reaction with airborne chemical reducing agents such as hydrazine with little or no improvement in methyl iodine-127 retention. The removal of radioactive iodine by impregnated activated carbons depends on three distinguishable reactions:

• 1.(1) adsorption on the carbon networks of the activated carbons,
• 2.(2) iodine isotope exchange with impregnated iodine-127
• 3.(3) chemical combination with impregnated tertiary amines when present. After the carbon is placed in service, the three mechanisms of iodine removal are degraded by the contaminants of the air at different rates; the adsorption process degrades faster than the other two.

     

Adsorption of iodine on hydrogen‐reduced silver‐exchanged mordenite: Experiments and modeling

The adsorption process of iodine, a major volatile radionuclide in the off‐gas streams of spent nuclear fuel reprocessing, on hydrogen‐reduced silver‐exchanged mordenite (Ag⁰Z) was studied at the micro‐scale. The gas‐solid mass transfer and reaction involved in the adsorption process were investigated and evaluated with appropriate models. Optimal conditions for reducing the silver‐exchanged mordenite (AgZ) in a hydrogen stream were determined. Kinetic and equilibrium data of iodine adsorption on Ag⁰Z were obtained by performing single‐layer adsorption experiments with experimental systems of high precision at 373–473 K over various iodine concentrations. Results indicate approximately 91% to 97% of the iodine adsorption was through the silver‐iodine reaction. The effect of temperature on the iodine loading capacity of Ag⁰Z was discussed. The Shrinking Core model describes the data well, and the primary rate controlling mechanisms were macro‐pore diffusion and silver‐iodine reaction. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1024–1035, 2017     

Two Facile Aniline-Based Hypercrosslinked Polymer Adsorbents for Highly Efficient Iodine Capture and Removal

Effective capture and safe disposal of radioactive iodine (¹²⁹I or ¹³¹I) during nuclear power generation processes have always been a worldwide environmental concern. Low-cost and high-efficiency iodine removal materials are urgently needed. In this study, we synthesized two aniline-based hypercrosslinked polymers (AHCPs), AHCP-1 and AHCP-2, for iodine capture in both aqueous and gaseous phases. They are obtained by aniline polymerization through Friedel–Crafts alkylation and Scholl coupling reaction, respectively, with high chemical and thermal stability. Notably, AHCP-1 exhibits record-high static iodine adsorption (250 wt%) in aqueous solution. In the iodine vapor adsorption, AHCP-2 presents an excellent total iodine capture (596 wt%), surpassing the most reported amorphous polymer adsorbents. The rich primary amine groups of AHCPs promote the rapid physical capture of iodine from iodine water and iodine vapor. Intrinsic features such as low-cost preparation, good recyclability, as well as excellent performance in iodine capture indicate that the AHCPs can be used as potential candidates for the removal of iodine from radioactive wastewater and gas mixtures.     

The reaction of polyaniline with iodine

Polyaniline (PANI) (emeraldine) base has been exposed to iodine in an ethanol-water suspension. The conductivity of PANI increased from 10⁻⁹ S cm⁻¹ to 10⁻⁴ S cm⁻¹ already at the molar ratio [I₂]/[PANI] = 1, and a higher content of iodine had only a marginal effect. This is the result of the protonation of PANI base with hydriodic acid, which is a by-product of the oxidation of the emeraldine form of PANI to pernigraniline constitutional units. The reaction is discussed on the basis of FTIR spectra. An alternative reaction, a ring-iodination of PANI, is marginal. Only one iodine atom substitutes a hydrogen atom in about 12 aniline units, even at high iodine concentration, [I₂]/[PANI] = 8. The film of polyaniline base can be used in sensing iodine; after exposure to the iodine vapor, the conductivity of the polyaniline film increased.     

The Synthesis of Covalent Triazine-Based Frameworks via Friedel–Crafts Reactions of Cyanuric Chloride with Thienyl and Carbazolyl Derivatives for Fluorescence Sensing to Picric Acid,Iodine and Capturing Iodine

A multifunctional thiophene-based covalent triazine framework (TTPATTh) with triphenylamine as core is synthesized by Friedel–Crafts reaction of cyanuric chloride with thienyl derivative for the first time. The yield of TTPATTh (99.59%) is far higher than that of the carbazole-based CTF (TTPATCz, 47.03%). TTPATTh and TTPATCz possess high BET surface areas with 1235 and 2501 m² g^–1 as well as high pore volumes with 1.60 and 2.23 cm³ g^–1, respectively. TTPATTh and TTPATCz have high thermal stability with high thermal decomposition temperatures of 514 and 598 °C in nitrogen atmosphere. With the introduction of triazine rings, the fluorescence sensing sensitivities of TTPATTh and TTPATCz to picric acid and iodine are improved significantly. Especially for TTPATTh, the K_sv values reach 5.95 × 10⁵ and 1.61 × 10⁴ L mol^–1, and LODs reach 1.02 × 10^–12 and 1.86 × 10^–12 mol L^–1. To the best of the knowledge, this is the most sensitive value among thiophene-based porous organic polymers to PA and I₂. Furthermore, TTPATTh and TTPATCz can also adsorb iodine in vapor phase, cyclohexane solution and aqueous solution, and release iodine by heating or in ethanol solution. The efficiency of controlling the release of iodine is higher than that in ethanol.     

非平衡碘负离子转化二氧化碳

以直流脉冲负高压电晕放电形式,通过加入电子亲和能较高的碘气,在完全电负性离子体条件下资源化处理CO₂。考察了进气流量、高压放电频率和原料摩尔比对CO₂转化率的影响。结果表明:70℃时,利用碘负离子成功将CO₂还原生成了CI₄,其产率随着CO₂流量的增加而减少。当进气流量0.06 L·min^-1、放电频率9.608 kHz,n(I₂)/n(CO₂)为2.5时,CO₂转化率在碘负离子作用下达到88.71%。另外,对碘负离子和CO₂还原反应机理进行了初步探讨。     

Synthesis of secondary amine-based fluorescent porous organic polymers via Friedel–Crafts polymerization reaction for adsorbing and fluorescent sensing iodine

We present the preparation and characterization of a novel class of secondary amine-based porous organic polymers (POPs: TDPA and TTPBTA), and their iodine adsorption, fluorescence sensing properties for the first time. Two secondary amine-based POPs were synthetized by Friedel−Crafts polymerization reaction catalyzed via methylsulfonic acid with yields of 22.51 and 54.44%. The thermal stability of resulting POPs run up to above 268 and 568°C, and their BET specific surface areas are 56.5 and 2.49 m² g⁻¹, respectively. Their iodine adsorption and fluorescent sensing properties are comparable to that of triphenylamine (TPA)-based (tertiary amine) POPs. The resulting POPs display excellent sorption abilities to iodine molecules with the iodine adsorption capacity of about 3.93 and 1.64 g g⁻¹. Adsorbed iodine is easily desorbed by heating or washing with organic solvents, which make them reusable. They can also adsorb iodine from cyclohexane solution. Moreover, the POPs possess excellent fluorescent sensing property for I₂ with Ksv of 1.85 × 10⁴ and 6.56 × 10⁴ L mol⁻¹, as well as the limits of detection (LODs) of 1.62 × 10⁻¹¹ and 6.86 × 10⁻¹² mol L⁻¹. The performance of adsorbing and fluorescence sensing iodine can be explained by electron transfer mechanism.     

Iodine Pentoxide Nano‐rods for High Density Energetic Materials

The iodine pentoxide is one of the most advanced oxidizers for nanostructured energetic formulations among the thermites due to the highest energy release per volume 25.7 kJ cm⁻³. The size and shape of iodine pentoxide particles have a strong impact on the pressurization rates during the reaction. Although micro‐sized iodine pentoxide particles are commercially available, nano‐sized particles, which are desired for various nano‐energetic applications, are not available on the market. Conventional wet chemical methods are unable to produce iodine pentoxide nanoparticles due to high solubility in water. In this study, we demonstrate fabrication of iodine pentoxide nano‐rods by high energy mechanical treatment of micro‐sized I₂O₅ particles. Tuning the energy dose in high‐energy ball milling is allowing to produce I₂O₅ nano‐rods with diameter of 50–100 nm and length of 300–600 nm. The produced nano‐rods exhibited 10 % smaller decomposition energy compared to the precursor of micro particles. The experiments showed that the nano‐energetic materials prepared with nano‐sized I₂O₅ rods have pressure discharge value of 43.4 MPa g⁻¹ which is two times higher than using commercial iodine pentoxide particles.     

Cationic starch iodophores

Cross‐linked cationic starches N‐(2‐hydroxyl)propyl‐3‐trimethyl ammonium starch chloride (CQS chloride), N‐(2‐hydroxyl)propyl‐3‐trimethyl ammonium starch iodide (CQS iodide), and N‐(2‐hydroxyl)propyl‐3‐trimethyl ammonium starch iodide–iodine (CQS triiodide) with the degree of substitution (DS) according to cationic groups from 0.04 to 0.62, as well as cross‐linked starch–iodine complexes were synthesized and tested as potential antibacterial agents. Cationic starch iodine derivatives were obtained during ion exchange reaction between CQS chloride and iodide or iodide–iodine anions in aqueous solutions. CQS_DS≤0.3 chloride can form several types of iodine complexes, such as the blue amylose–iodine inclusion complex and ionic CQS⁺I^?·(I₂)_m complex (m ≥ 1). The antibacterial activity of modified starches–iodine samples against different pathogenic bacterial cultures and contaminated water microorganisms was evaluated. CQS chloride and CQS iodide were found to be bacteriostatic. A strong antibacterial activity was characteristic of CQS triiodides in which molecular iodine is present in both ionic and inclusion complexes. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Rapid synthesis of cellulose triacetate from cotton cellulose and its effect on specific surface area and particle size distribution

A highly rapid process is described for the preparation of cellulose triacetate and its effect on particle size and surface area of the product. The process involves microwave-assisted rapid synthesis of cellulose triacetate with very low amount of acetic anhydride (10–15% of acetic anhydride is used in conventional methods) in the presence of iodine as a catalyst using a designed reaction vessel. The technique used is simple and rapid; it is also characterized by a high conversion ratio (yield 100%). A small amount of iodine (115 and 230 mg, 1.15 and 2.3% of cellulose weight) was found to be effective in the production of cellulose triacetate using 25, 30 to 40 mL acetic anhydride for 10 g cellulose under microwave irradiation for 2–4 min. The production of cellulose triacetate and the degree of substitution were confirmed by FTIR, Raman, ¹H NMR, and thermogravimetric analysis. The optimal reaction condition was discovered to be 3 min microwave radiation and 30 mL acetic anhydride in the presence of 230 mg iodine for 10 g cellulose. The effects of the amount of acetic anhydride, and amount of catalyst and reaction time on the specific surface area, pore volume, mean pore diameter, and particle size distribution were investigated. The highest surface area obtained was 39.63 m²/g. The specific surface area and particle size distribution are highly dependent on the amount of acetic anhydride and I₂ catalyst. About 10% of the synthesized cellulose acetate showed particle size less than 200 nm.     

NMR and EPR studies of room temperature highly fluorinated graphite heat-treated under fluorine atmosphere

Semi-ionic carbon fluoride obtained by reaction of graphite with a gaseous mixture of IF₅, HF and F₂ was modified by a post-fluorination at various temperatures in the range 100-680 °C. The resulting materials were studied by ¹⁹F-NMR and EPR both at room temperature and at different experimental temperatures from 200 to 360 K and from 100 to 473 K for NMR and EPR experiments, respectively. ¹⁹F-NMR gives information about the residual intercalated iodine fluoride species (IF₅, IF₆⁻ and IF₇) such as the temperature of their removal from the host fluorocarbon matrix and their mobility into the interlayer space. The nature of the C-F bonding was investigated by ¹⁹F-NMR, MAS/¹³C-NMR, FT-IR spectroscopy and X-ray diffraction. The C-F bonding changes from semi-ionic to a mainly covalent character at a fluorination post-treatment temperature close to 450 °C. This transformation coincides with the removal of the iodine fluoride species from the host structure. The densities of the paramagnetic dangling bonds were studied by EPR; this technique allows also to investigate the local environment of the dangling bonds in the fully fluorinated samples (obtained with fluorination post-treatment temperatures higher than 450 °C). As a matter of fact, an hyperfine structure was observed for these samples; it results from interaction of the dangling bond electron with six neighboring fluorine nuclei. The role of the intercalated species (iodine fluoride compounds and HF) on the mechanisms of the extra-fluorination is also discussed.     

Iodine number determination of milk fat and vegetable fats by refractometry

A refractometric method for the estimation of iodine number of milk fat has been suggested. About 0.2 ml of milk fat was iodinated with ca. 10 ml Wijs iodine reagent for 3 min using mercuric acetate as catalyst. The iodinated fat showed a higher refractive index than the original fat. The changes in refractive indices showed a very high correlation with the iodine values of the fats (T=0.9993). The average of the ratios of change in refractive index to iodine number was 50.7×10⁻⁵, from which the iodine number of milk fat can be calculated. The method can also be applied to vegetable fats. The ratios of change in refractive index to iodine number for the oils of peanut, rapeseed, soybean, niger, sesame, and sunflower were similar, and the average was 45.2×10⁻⁵. The ratio for linseed oil was 38.4×10⁻⁵, and for coconut fat it was similar to that of milk fat.     

Effect of oxygen donor alcohol on nonaqueous precipitation synthesis of alumina powders

Monodispersed alumina powders were prepared via nonaqueous precipitation process using aluminum powders as aluminum source, acetic acid as precipitant. Effect of oxygen donor and solvent alcohol such as methanol, ethanol, isopropanol on the preparation of ultrafine alumina powders and the precursor reaction mechanism have been investigated by XRD, FT-IR, TEM, FE-SEM and performance tests of sintered bodies. The intermolecular condensation of methanol with the catalysis of Lewis acid aluminum methoxide leads to hydrolysis of aluminum methoxide, forming amorphous precipitates, dehydration polycondensation of aluminum hydroxide and resulting in serious agglomeration of precipitates and alumina powders, the worst morphology and properties of sintered body. The pulling electron effect and steric hindrance of isopropyl group make the structure of aluminum isopropoxide overwhelmingly stable and relatively arduous to be replaced by precipitant acetic acid, which results in underdeveloped crystallinity and agglomeration of both precipitates and alumina powders, poor morphology and properties of sintered body. The optimized oxygen donor and solvent alcohol is ethanol. Monodispersed, high crystallinity C₄H₇AlO₇ precipitates and alumina powders can be obtained when ethanol is used as oxygen donor and solvent, and the highest relative density, mechanical properties and the most homogeneous microstructure was obtained. The density, flexural strength, volume resistivity, breakdown voltage and thermal expansion coefficient are 99.1% of TD, 128.0?±?2.2?MPa, 9.8?×?10¹⁶ Ω?cm, 45.2?kV/mm and 7.6?×?10^?6 °C^?1, respectively. Precursor reaction mechanism is deduced that aluminum powders react with oxygen donor alcohol to form aluminum alkoxide with the catalyst iodine, and then react with acetic acid to form crystal C₄H₇AlO₇ precipitates. Nonaqueous precipitation method is expected to become a promising candidate for mass production of alumina powders.     

Reverse iodine transfer polymerization of vinyl acetate and vinyl benzoate: synthesis and characterization of homo‐ and copolymers

Homo‐ and copolymers of vinyl esters including vinyl acetate (VAc) and vinyl benzoate (VBz) were synthesized via the reverse iodine transfer radical polymerization technique. Polymerization was carried out in the presence of iodine as the in situ generator of the transfer agent and 2,2′‐azobis(isobutyronitrile) as the initiator at 70 °C. Reverse iodine transfer radical homopolymerization of VAc and VBz led to conversions of 76 and 57%, number‐average molecular weights of 8266 and 9814 g mol^?1 and molecular weight distributions of 1.58 and 1.49, respectively. The microstructure of the synthesized polymers was investigated in detail using gel permeation chromatography, ¹H NMR, ¹³C NMR and distortionless enhancement of polarization transfer (135° decoupler pulse) techniques. Relatively narrow molecular weight distribution and controlled and predictable trend of molecular weight versus conversion were observed for the synthesized polymers, showing that reverse iodine transfer radical homo‐ and copolymerization of VAc and VBz proceeded with controlled characteristics. Results of molecular weight and its distribution along with the ¹H NMR spectra recorded for homo‐ and copolymers indicated that side reactions can occur during the course of polymerization with a significant contribution when VAc, even in a small amount, was present in the reaction mixture. This can result in polymer chains with aldehyde dead end and broadening of the molecular weight distribution. © 2015 Society of Chemical Industry     

Interaction of polydiallyldimethylammonium salts with iodine

The interaction between polydiallyldimethylammonium chloride (PDADMAC) and KI or KBr, followed by changes in conformation of macromolecules, coil compaction, and counterion exchange, was detected by means of turbidimetry and viscometry. In aqueous solutions at presence of KI, PDADMAC rapidly binds iodine by the formation of polymer–iodine complexes PDADMA I^? I_m (m ≤ 4). Spectrophotometric investigations of the interaction in water without KI prove the formation of complexes of polyquaternary ammonium chloride or bromide with iodine only via iodide. These ions can be generated in the polymer‐catalyzed hydrolysis reaction of iodine. By inducing hydrolysis of iodine and binding the eventually formed iodide, PDADMAC acts as an iodine acceptor with self‐strengthening capacity. For the sorption of gaseous iodine, the possibility of direct interaction of its dipoles with the charged groups of the polyelectrolyte is also reasoned. Polydiallyldimethylammonium halides were used to modify activated carbon and employed in a nuclear power station for treatment of outlet gases containing radioactive iodine. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2710–2716, 2006     

Langmuir-Blodgett films containing carotenoid dye. II. Structure and conducting characteristics of ethyl β-apo-8-carotenoate/cadmium stearate LB films

The structure, doping, and electrical conductivity characteristics of ethyl β-apo-8-carotenoate dye (EA8C)/cadmium stearate Langmuir-Blodgett (LB) films were investigated. The EA8C/cadmium stearate mixed multilayer thin films, with the molar ratio of 1 : 4, prepared at subphase pH 6, exhibited well-defined layered structures as determined by X-ray diffraction (XRD) spectra. The mixed LB films went ready doping upon exposure to iodine vapor or dipping in sulfuric acid solution. The UV/VIS and XRD data showed that the incorporated EA8C was thermally stable up to 80°C. The best conductivity characteristics were obtained with the iodine vapor. Thus, the mixed LB films exposed to iodine vapor showed in-plane and transverse conductivities of 10^-6 and 10^-7–10^-8 S/cm, respectively. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 619–624, 1997     

Influence of different initiators on the adhesion properties of photopolymerized epoxides on gold and silicon

Photocuring of epoxides proceeds by a cationic mechanism. The required photoinitiators are iodonium or sulfonium salts with non-nucleophilic anions. The influence of different photoinitiators on the adhesion properties of both a rigid and a soft epoxide is examined. Depending on the substrates to be joined, different decomposition products of the initiators are concentrated in the interphase. This accumulation of decomposition products in the interphase leads to a decreased adhesion. On gold surfaces the sulfur of sulfonium salts is concentrated as expected. But surprisingly the iodine of the iodonium salts is also concentrated on gold. It could be shown by immobilization experiments that organic iodine compounds with the iodine in any oxidation state reacted with gold surfaces. Due to this reaction iodide anions are formed. On silicon surfaces the fluorine of the anions PF₆ ^- and SbF₆ ^- is concentrated due to the high affinity of silicon for fluorine. The iodonium salt with [B(C₆F₅)₄]anion contains no fluorine able to react with the silicon. Therefore, the fluorine cannot be concentrated in the interphase and the joints prepared with the soft epoxide containing this initiator have a higher shear strength compared to adhesives with conventional anions.     

Kinetics of aging process on reduced Ag exchanged mordenite in dry air and humid air

Aging effects of off-gas streams including dry air and humid air on reduced silver exchanged mordenite (Ag⁰Z) were studied. Aged Ag⁰Z was prepared by exposing Ag⁰Z to dry air and humid air at different aging temperatures, time, and water vapor concentrations. Iodine loading capacity on the aged Ag⁰Z was obtained through a continuous-flow adsorption system. Significant iodine loading capacity losses were observed after the Ag⁰Z was exposed to dry air and humid air. Physical and chemical analyses were conducted to observe the physical and chemical changes of Ag⁰Z after being aged. From iodine adsorption data and sample analyses, it was found that iodine loading capacity on the aged Ag⁰Z in dry air and humid air decreases with increasing aging temperatures, time, and water vapor concentrations. The pseudo reaction model describes experimental data well and the oxidation of Ag⁰ is the rate determining step in the aging process.     

Hydrochlorination of oleic acid: Kinetics and Henry's constant

The addition reaction of gaseous hydrogen chloride to oleic acid (hydrochlorination) was investigated. Oleic acid was placed in an autoclave chamber, into which gaseous hydrogen chloride was fed, and the reaction was carried out under batch and semiflow conditions. The hydrochlorination of oleic acid by hydrogen cloride is a gas-liquid reaction involving the initial absorption of hydrogen chloride into a quiescent liquid, accompanied by a reaction of the dissolved gas with the liquid to form chlorostearic acid. The course of the reaction was monitored by withdrawing oil samples at 30-min intervals and determining the iodine value, acid value, and chlorine content. The kinetics of hydrochlorination was studied at constant pressure (40 atm). The experimental data were fitted to an irreversible pseudo zero-order rate equation with the reaction constant k=2.293×10⁻⁷ mol/cm³·s. The solubility of HCl (Henry's constant) in chlorostearic acid was estimated from two types of batch experiments, including a single and double feed of HCl. The mean Henry's constant value for physical absorption was 3218 atm cm³/mol in the pressure range of 11.2–16 atm and at a temperature of 21°C. Similar batch experiments were performed in oleic acid, and the results supported the Henry's constant value determined for chlorostearic acid.     

Slow release polymer–iodine tablets for disinfection of untreated surface water

Simple water treatment devices are designed to treat small amounts of drinking water for home use. This study was undertaken to develop an iodine‐releasing polymeric formulation and examine its potential as a domestic water purifier for untreated surface water. The antimicrobial tablet formulation was made from gum arabic (GA), poly(vinylalcohol) (PVA), ethyl cellulose (EC), and poly(vinylpyrrolidone)‐iodine (PVP‐I). The formulation consisted of a dispersible core tablet surrounded by a hydrophilic coating of EC and poly(ethylene glycol) mixture. These stable, non‐vaporizing, and water‐insoluble tablets slowly release iodine through diffusion over 48 h when suspended in water. The swelling behavior and release were observed to be the functions of excipient composition, iodine loading, and coating materials. Iodine release was determined by UV–VIS spectroscopy and volumetric titrations. The tablets were also assessed for antimicrobial activity against Escherichia coli, Staphylococcus aureus, Listeria monocytogenes Scott A, and Salmonella typhimurium. The disinfection efficiency of the developed tablets was compared with a commercial formulation (Potable Aqua®) as both contain iodine‐releasing active compounds and work on the antimicrobial property of released iodine. The difference between the two formulations is that water‐dispersible Potable Aqua® has a higher amount of free iodine quickly available in water thereby making it a fast‐action emergency water purifier, whereas the developed water‐insoluble polymer–iodine tablets act slowly and require 24 h to show the same disinfection efficacy with lower content of iodine in water. Overnight release of iodine in water from polymer–iodine tablets was effective in 99.9% reduction of an initial cell count of ～ 10⁷ colony forming units (cfu)/mL. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010