Adsorption Of Iodide Research Articles

Mass Production of Source Core for Iodine-125 Seed

Nowadays, brachytherapy using a sealed source called a ‘seed’ has drawn attention for the treatment of various cancers. Generally, Iodine-125 (I) has been used for the seed in the radiation therapy of eye disease and prostate cancer. I has a half-life of 59.4 days, and emits 27 keV and 31 keV X-rays, and a 35 keV γ-ray through an internal conversion process. An I seed of 4.5 mm (l) × 0.8 mm (O) has a structure composed of an inner source core and an outer shell capsule. I is adsorbed on the source core’s surface and a titanium capsule surrounds it. The seed is directly inserted into the human body to treat cancer cells, and the seed may be permanently left in tissues owing to the low activity and the excellent biocompatibility of Ti capsule (Fig. 1). The diverse materials and preparation of the source core have been reported for many years, for example, a palladium (Pd) coated silver wire, a silver (Ag) rod and a porous ceramic tube etc. The Korea Atomic Energy Research Institute (KAERI) previously used a bare ceramic rod and an Ag+Al2O3 rod 12 as the core. With regard to the preparation of an I seed, the electro deposition technique was used for adsorption of iodine on the silver surface. In addition, a chemical adsorption on the Pd coated silver wire, the impregnation into ceramics and iodine substitution after forming an intermediate having chloride (Cl) or bromide (Br) were reported. In our previous investigation, the effect of the various intermediates (N3 −, CO3 , C2O4 , AsO4 , Cl− and PO4 ) using each set of 10 Ag rods were reported. Among them, Ag rods modified using phosphate (PO4 ) showed the highest adsorption ability with the good substitution effect of iodine. On the basis of this technique, the studies on mass production using 100 Ag rods and leachability test of a finished source core prior to encapsulation were performed in this work. The uniformity of iodide adsorption on every silver rod in the same batch is important for mass production to reduce the number of abandoned rods. For this reason, we developed a cutting device (Fig. 2) precisely manufacturing the silver rods in 3 mm (l) and compared the iodide adsorption with the handmade rods. A silver wire of 0.5 mm (O) passes through a syringe needle (d) of 0.584 mm (O), and the wire is softened through the heating part (b). The length of this wire is adjusted with the help of micrometer (c) and can quickly cut to a uniform shape by using a steel blade (a). In the case of handmade rods, the wire was cut by using scissors, and both ends were manually polished with sandpaper.

Ion interactions with the air-water interface using a continuum solvent model.

Explaining and predicting the distribution of ions at the air-water interface has been a central challenge of physical chemistry for nearly a century. In essence, the problem amounts to calculating the change in the solvation energy of an ion as it approaches the interface. Here, we generalize our recently developed model of ionic solvation energies to calculate this interaction. The change in the Born energy as well as the static polarization response of the ion is included by using the conductor-like screening model (COSMO), which treats the ions quantum mechanically. Approximate expressions for the dispersion repulsion, cavity attraction, and surface potential contributions are also included. This model reproduces the surface tensions of electrolyte solutions and is consistent with ab initio molecular dynamics (MD) simulation. The model provides clear physical insight into iodide's adsorption. Unlike alternative models, no parameters are deliberately adjusted to reproduce surface tensions, and all of the important contributions to the interactions are included. Solving this problem has important direct implications for atmospheric chemistry and bubble properties. It also has important indirect implications for the more complex interactions of ions with protein and mineral surfaces. These play a fundamental role in a vast number of biological and industrial processes. The model is conceptually simple and has low computational demand, which facilitates its extension to these important applications.

On the role of ultrasound and mechanical stirring for iodide adsorption by calcined layered double hydroxides

Improving the adsorption of long-term radioactive species in the underground disposal of waste waters from nuclear reactors is a key issue. The natural metal oxides or hydroxides underground have the low retention ability of anionic species. Here, calcined Mg/Al LDHs were used as adsorbents. The influence on the adsorption capacity of different intercalated guest anions (carbonate (CO32−) and nitrate (NO3−)) in the parent LDH was investigated, along with the effect of ultrasonication. Two Mg/Al molar ratios (3/1 and 2/1) were compared. Adsorption capacity was strongly affected by material textural properties, and the carbonate LDH-derived mixed oxides showed the largest adsorption capacity. Mixed oxides with an Mg/Al molar ratio equal to 3 presented higher iodide adsorption due to their lower charge density. The adsorption assisted by ultrasound increased iodide removal efficiency by reducing internal diffusion limitation. Two models were used to determine adsorption capacity: Langmuir and Freundlich. The iodide adsorption was best fitted by the Langmuir equilibrium model.

Adsorption Energy oftert-Butyl on Pt(111) by Dissociation oftert-Butyl Iodide: Calorimetry and DFT

Dissociative and molecular adsorption of tert-butyl iodide on Pt(111) has been studied by single-crystal adsorption calorimetry (SCAC), photoelectron spectroscopy (XPS), reflection/adsorption infrared spectroscopy (RAIRS), and density functional theory (DFT) calculations. Up to a t-BuI total coverage of 0.07 ML, t-BuI adsorbs dissociatively at 100 K to form t-Buad plus Iad, with an integral heat of reaction of 223 kJ/mol. At higher coverage, up to a total coverage of 0.15 ML, t-BuI adsorbs molecularly directly to the Pt surface atoms with an average heat of adsorption of 91 kJ/mol. At 0.15 ML, the first layer is saturated. Between 0.15 and 0.38 ML, t-BuI adsorbs molecularly on top of the first layer with a constant heat of adsorption of 44.5 ± 1.9 kJ/mol. The standard enthalpy of formation of adsorbed tert-butyl on Pt(111) at 1/25 ML coverage is estimated from the heat measurements to be −168 ± 20 kJ/mol, giving a (CH3)3C–Pt(111) bond enthalpy of 216 ± 20 kJ/mol. DFT calculations were performed using the GGA-PBE and optB86b vdW density functionals to determine the heats of reaction and binding energies of relevant adsorbates. Comparison to the measured energies shows that optB86b vdW-DF is more accurate than GGA-PBE for describing the adsorption and bonding of t-buI and t-Bu on Pt(111) because these energies contain large contributions from dispersion forces.

Surface treatments of silver rods with enhanced iodide adsorption for I-125 brachytherapy seeds

This study described an effective method to load 125I on silver rods for the preparation of a brachytherapy source. We tested various ligands on the silver rod surface to screen the one with the highest adsorption and specific radioactivity. In addition, we investigated the effect of surface etching to increase the adsorption capability followed by the extended surface area. We also found that the use of an oxidant during iodide adsorption can increase the loading significantly. The maximum activity of 137.90MBq/rod (3.7269mCi/rod) was achieved on the etched silver rods with phosphate ligand and hydrogen peroxide as an oxidant. In addition, this is 4.5-fold higher than that of the conventional chloride treatment method.

Surface kinetics and energetics from single crystal adsorption calorimetry lineshape analysis: Methyl from methyl iodide on Pt(1 1 1)

The first use of single crystal adsorption calorimetry (SCAC) to probe the kinetics of surface chemical reactions is presented. It is applied to study a common situation encountered in catalytic mechanisms, wherein a gas quickly populates a molecularly adsorbed state that then converts to more stable products on a slower timescale (10–1000ms). We show that for such a two-step process, detailed analysis of the heat-detector signal’s time-response lineshape to a single pulse of gas provides the rate constant for the second step and the heats of reaction for both of the elementary reactions. We apply this analysis to the dissociative adsorption of methyl iodide (CH3I) on Pt(111) at 270K, to measure the heats of reaction for the elementary steps involved and the rate constant for the slow step, all as a detailed function of coverage. At low coverage, the reaction is CH3Ig→CH3Iad→CH3,ad+Iad, followed at high coverage by CH3,ad→CHad+2Had and CH3,ad+Had→CH4,g (above 0.08ML total CH3,ad plus Iad). These results provide the rate constant for the dissociation of CH3Iad and the heats of formation of both CH3,ad and CHad. These two heats agree with values determined at 320K where the rates are so fast that lineshape analysis is not needed, proving the validity of the lineshape analysis method introduced here for analyzing SCAC data.

Surface free energy analysis of adsorbents used for radioiodine adsorption

In this work, the surface free energy of biomass-based activated carbons, both fresh and impregnated with triethylenediamine, has been evaluated. The contribution of Lifshitz van der Waals components was determined by the model proposed by van Oss et al. The results obtained allowed predicting the most probable configurations of the impregnant onto the carbon surface and its influence on the subsequent adsorption of radioactive methyl iodide.

Fundamental Studies of Methyl Iodide Adsorption in DABCO Impregnated Activated Carbons

Methyl iodide capture from a water vapor stream using 1,4-diazabicyclo[2.2.2]octane (DABCO)-impregnated activated carbons is, for the first time, fundamentally described here on the atomic level by means of both molecular dynamics and grand canonical Monte Carlo simulations. A molecular dynamics annealing strategy was adopted to mimic the DABCO experimental impregnation procedure in a selected slitlike carbon pore. Predictions, restricted to the micropore region, are made about the adsorption isotherms of methyl iodide, water, and nitrogen on both impregnated and bare activated carbon models. Experimental and simulated nitrogen adsorption isotherms are compared for the validation of the impregnation strategy. Selectivity analyses of the preferential adsorption toward methyl iodide over water are also reported. These simulated adsorption isotherms sum up to previous experimental studies to provide an enhanced picture for this adsorption system of widespread use at nuclear plant HVAC facilities for the capture of radioactive iodine compounds.

Energetics of Adsorbed CH3 on Pt(111) by Calorimetry

The enthalpy and sticking probability for the dissociative adsorption of methyl iodide were measured on Pt(111) at 320 K and at low coverages (up to 0.04 ML, where 1 ML is equal to one adsorbate molecule for every surface Pt atom) using single crystal adsorption calorimetry (SCAC). At this temperature and in this coverage range, methyl iodide produces adsorbed methyl (CH(3,ad)) plus an iodine adatom (I(ad)). Combining the heat of this reaction with reported energetics for Iad gives the standard heat of formation of adsorbed methyl, ΔH(f)(0)(CH3,ad), to be −53 kJ/mol and a Pt(111)–CH3 bond energy of 197 kJ/mol. (The error bar of ±20 kJ/mol for both values is limited by the reported heat of formation of I(ad).) This is the first direct measurement of these values for any alkyl fragment on any surface.

Thermodynamics of iodide adsorption at the instantaneous air-water interface

We performed molecular dynamics simulations using both polarizable and non-polarizable force fields to study the adsorption of iodide to the air-water interface. A novel aspect of our analysis is that the progress of ion adsorption is measured as the distance from the instantaneous interface, which is defined by a coarse-graining scheme proposed recently by Willard and Chandler ["Instantaneous liquid interfaces," J. Phys. Chem. B 114, 1954-1958 (2010)]. Referring structural and thermodynamic quantities to the instantaneous interface unmasks molecular-scale details that are obscured by thermal fluctuations when the same quantities are referred to an average measure of the position of the interface, such as the Gibbs dividing surface. Our results suggest that an ion adsorbed at the interface resides primarily in the topmost water layer, and the interfacial location of the ion is favored by enthalpy and opposed by entropy.

이온교환수지와 활성탄의 혼합수지를 이용한 과염소산 이온의 탈착 특성 연구

Perchlorate () is the material that is used as propellants of rockets and material of explosive as a form of ammonium perchlorate salts. Ammonium perchlorate solution of high concentration is recovered from expired rocket through demilitarization process by the water-jet method. If people take perchlorate in food and water, it interferes with adsorption of iodide which is the substance needed to synthesize thyroid hormone in the thyroid gland. It has an bad influence upon disturbing pregnancy and synthesis of growth hormone. So the effective method is necessary to remove perchlorate anion in water. By considering economic aspect, we studied effective desorption (regeneration) of perchlorate anion from adsorbent with studies on removal and adsorption of perchlorate anion. Desorption experiment was conducted as batch type. Depending on various conditions (concentration, pH, cation anion form) elution, we evaluated amount, efficiency of desorption(amount of adsorption/desorption 100). Also, research confirmed the efficiency of mixed resins between anion exchange resin and activated carbon and expected synergic effect from advantages of both adsorbents.

Characterization and iodide adsorption behaviour of HDPY+ modified bentonite

Owing to its favourable physical, chemical and rheological properties, densely compacted bentonite or bentonite-sand mix is considered as a suitable buffer material in deep geological repositories to store high level nuclear waste. Iodine-129 is one of the significant nuclides in the high level waste owing to its long half life and poor sorption onto most geologic media. Bentonite by virtue of negatively charged surface has negligible affinity to retain iodide ions. As organo-bentonites are known to retain iodide ions, the present study characterizes hexadecylpyridinium chloride (HDPyCl.H2O) treated bentonite from Barmer India (referred as HDPy+B) for physico-chemical properties, engineering properties and the iodide adsorption behavior of the organo clay. Batch experiments revealed that HDPy+ ions are largely retained (94 % retention) via cation exchange; the ion-exchange process neutralizes the negative surface charge and bridges clay particles leading to reduction in Atterberg limits, clay content and sediment volume. The organo clay retains iodide by Coulombic attraction (at primary sites) and anion exchange (at secondary sites). The free-energy change (ΔGo = −25.5 kJ/mol) value indicated that iodide retention by organo clay is favored physical adsorption process. Iodide adsorption capacity of organo clay decreased significantly (85–100 %) on dilution with 50–80 % bentonite. On the other hand, dilution of bentonite with 50 % organo clay caused 58 % reduction in swell potential and 21 % reduction in swell pressure.

Iodide Adsorption onto Three Organic–Inorganic Composite Adsorbents

Composite adsorbents, Ca(ALG)2-Cu2O, Ca(ALG)2-AgCl and Ca(ALG)2-Ag, were prepared using Cu2O, AgCl and Ag as the adsorption-active components and calcium alginate as the matrix material. The adsorption of iodide from aqueous solutions onto these adsorbents was investigated as a function of initial solution pH, temperature and co-existing NaCl. The loading of the adsorption-active components in the composite adsorbents is much higher than that in the reported composite adsorbents. In neutral solutions, the equilibrium adsorption amount follows the order of Ca(ALG)2-AgCl >> Ca(ALG)2-Ag >> Ca(ALG)2-Cu2O. The adsorption by Ca(ALG)2-AgCl is insensitive to pH, while the adsorption by Ca(ALG)2-Cu2O and Ca(ALG)2-Ag is pH dependent. The effect of temperature on the adsorption is more pronounced for Ca(ALG)2-Cu2O than for Ca(ALG)2-AgCl and Ca(ALG)2-Ag. The co-existing NaCl does not affect the adsorption by Ca(ALG)2-AgCl very much; however, it suppresses the adsorption by Ca(ALG)2-Ag, and especially, Ca(ALG)2-Cu2O. ...

Solid-State NMR and TGA Studies of Silver Reduction in Chabazite

Silver-exchanged molecular sieves have shown great promise in applications ranging from antimicrobial materials to the adsorption of xenon and iodide, two key contaminants emitted from nuclear reactors. In this work, solid-state 27Al and 29Si MAS NMR and TGA were used to study silver reduction in silver-exchanged chabazite under various thermal conditions. The solid-state NMR results for both 27Al and 29Si show that there are no major changes in the chabazite during silver reduction in an argon stream; however a progressive structural change does take place in the hydrogen stream. The structural change likely involves breaking the silicon oxygen bond of the Si-O-AI fragment of chabazite, leading to the formation of extra-framework aluminum oxide. The TGA results at temperatures up to 600 degrees C indicate that silver reduction is less complete in an argon stream than in a hydrogen stream. In this paper we propose that silver reduction occurs via the following reactions: 2(Ag + ZO-)+H2O --> 1/2O2+2Ag0 + 2ZOH and nAg + mAg = Ag(m+n)n+ (in an argon stream); and Ag(+) + ZO(-) + 1/2H2 = Ag0 + ZOH and 2ZOH = ZO(-) + Z(+) + H2O (in a hydrogen stream).

Electrostatically mediated adsorption by nanodiamond and nanocarbon particles

Nanodiamond (ND) and other nanocarbon particles are popular platforms for the immobilization of molecular species. In the present research, factors affecting adsorption and desorption of propidium iodide (PI) dye, chosen as a charged molecule model, on ND and sp 2 carbon nanoparticles were studied, with a size ranging from 75 to 4,305 nm. It was found that adsorption of PI molecules, as characterized by ultra- violet-visible spectroscopy, on ND particles is strongly influenced by sorbent-sorbate electrostatic interactions. Different types of NDs with a negative zeta potential were found to adsorb positively charged PI molecules, while no PI adsorption was observed for NDs with a positive zeta potential. The type and density of surface groups of negatively charged NDs greatly influenced the degree and capacity of the PI adsorbed. Ozone-purified NDs had the highest capacity for PI adsorption, due to its greater density of oxygen containing groups, i.e., acid anhydrides and carboxyls, as assessed by TDMS and TOF-SIMS. Single wall nanohorns and carbon onion particles were found to adsorb PI regardless of their zeta potential; this is likely due to p bonding between the aromatic rings of PI and the graphitic surface of the materials and the internal cavity of the horns.

Microwave assisted synthesis of a new lead(ii) porous three-dimensional coordination polymer: study of nanostructured size effect on high iodide adsorption affinity

A three-dimensional (3D) porous coordination polymer, [Pb(4-bpdh)(NO3)(H2O)]n (HMTI-1), has been synthesized under microwave-irradiation (MW) of identical reaction mixtures of Pb(II) salt and 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene (4-bpdh) at different powers. The microwave synthesis of HMTI-1 has been compared to its conventional synthesis. It has been found that by using MW synthesis HMTI-1 can be obtained in a much shorter synthesis time with improved yield and physical properties. Compound HMTI-1 is stable up to 300 °C in the static atmosphere of nitrogen and useful for loading and unloading of guests. In this compound, we successfully loaded the porous crystals and nano-HMTI-1 with I2 by suspending them in a solution of I2 in cyclohexane. The delivery of I2 from HMTI-1⊃3I2 performed in ethanol, a nonaromatic solvent, at room temperature was determined by UV/vis spectroscopy. A comparison of adsorption and desorption rates of iodide between nano and bulk compounds was also conducted.

Reversible crystal-to-crystal transformation in nano-porous three-dimensional lead(ii) MOFs; study of solvent attendance on iodide adsorption affinity

A reversible crystal to crystal transformation of a new porous 3D lead(II) coordination polymer with the ligand 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene (4-bpdh), [Pb(4-bpdh)(NO3)2]n (HMTI-2) to [Pb(4-bpdh)(NO3)2(H2O)]n (HMTI-1), by hydration and dehydration, has been observed. Powder X-ray diffraction experiments and IR analysis showed that the compounds obtained by hydration and dehydration have same crystalline lattice. Among the proposed methods for the removal of dyes and toxic materials such as iodine from contaminated water, removal by adsorption technologies is regarded as one of the competitive methods because of high efficiency, economic feasibility and simplicity of operation. In this work, we successfully loaded compounds HMTI-2 and HMTI-1 with I2 by suspending them in a cyclohexane solution of I2. The delivery of I2 from compounds HMTI-2 and HMTI-1 in ethanol at room temperature was determined by UV-vis spectroscopy. Adsorption and desorption rate of iodide in HMTI-1 and HMTI-2 shows that present of H2O molecules have effective role in increase of iodine adsorption in HMTI-1.

Influence of carbon xerogel textural properties on the dynamic adsorption of methyl iodide

X-ray microtomography coupled to image analysis has been used to study the influence of the adsorbent pore texture and the experimental conditions on the dynamic adsorption of methyl iodide in packed filters. By applying this imaging technique the internal axial adsorption profiles for increasing exposure times to the gas stream are analysed. This experimental technique establishes a new technology to study in situ the dynamic adsorption of volatile compounds. Resorcinol–formaldehyde based carbon xerogels have been used as adsorbents, as their pore texture can be tuned by changing the synthesis conditions. The textural characteristics of the adsorbents (surface areas and pore volumes) have been assessed by using nitrogen and carbon dioxide adsorption as well as mercury porosimetry. The methyl iodide dynamic adsorption results show that, for the same gas flow rate and CH 3I inlet concentration, the adsorbed amount is highly dependent on large pore volumes. Thus, samples with almost the same micropore volumes (adsorption volumes) have different methyl iodide adsorption capacities, which are related to, the above mentioned, large pores. The influence of both the gas carrier flow rate and the methyl iodide inlet concentration on the adsorption can be explained using the so-called linear driving force model. This approach takes into account the fact that internal transport limitations are directly related to the pore texture. Moreover, the simulation of the dynamic adsorption process has allowed relating the simulated axial concentration profiles to the experimental X-ray microtomography data.

Adsorption of iodide ions on a calcium alginate–silver chloride composite adsorbent

A composite spherical adsorbent for iodide ions was prepared with silver chloride as an adsorption active component, and calcium alginate as a carrier. The adsorbent had an adsorption active component content of 0.96 mmol g −1, a water content of 83%, and a point of zero charge (PZC) of 7.2. The kinetics and thermodynamics of iodide adsorption onto the adsorbent in aqueous solutions were investigated comprehensively, by considering the effects of initial iodide concentration, temperature, solution pH, and coexisting NaCl. The results exhibited that the initial adsorption rate increases with the increase in initial iodide concentration and temperature. In general, the equilibrium adsorption amount was found to be insensitive to coexisting NaCl, and initial solution pH in a range of 1–6. The dominant adsorption mechanism has been proved to be the precipitation transformation reaction. The composite adsorbent used in this study is easy to prepare, avoiding silver chloride from leaching, and has been proved to be an effective iodide adsorbent with an adsorption capacity of 1.1 mmol g −1.

Kinetics of fission products accumulation on structural materials

The aim of the present work was to reveal the kinetics of the accumulation of some possible contaminant on the surfaces of structural materials (zirconium alloys and 08H18N10T stainless steel) in the primary circuit of Paks NPP. The kinetics of adsorption and desorption of iodide, caesium and cerium ions were investigated by quartz crystal microbalance (QCM) installed into a flow cell. The results on thin layers were confirmed by immersing experiments, using radiotracer technique and γ-spectrometry to detect the traced ions on the surfaces. Experiments were carried out in electrolyte solution which was similar to the cooling water. All measurements were carried out at room temperature. Both adsorption and desorption were found to be fast, taking only several seconds; time constants were also evaluated.