Removal Of Iodide Research Articles

Enhanced removal of iodide from aqueous solution by ozonation and subsequent adsorption on Ag-Ag2O modified on Carbon Spheres

In this work, Ag-Ag2O coated on carbon spheres (Ag-Ag2O-CSs) as an effective adsorbent was successfully synthesized, the morphologies and structure of the as-fabricated composites were characterized through SEM, XRD and XPS. Ozonation and subsequent adsorption on Ag-Ag2O-CSs was used to removal of iodide from aqueous solution. Furthermore, the ozonation and adsorption process is slightly influenced in the presence of large concentrations of competitive anions, and the Ag-Ag2O-CSs displayed better adsorption ability at optimum conditions of pH 2.1. The equilibrium isotherms data for iodine adsorption onto Ag-Ag2O-CSs was best fitted with Freundlich isotherm and the adsorption capability was 374. 91mg/g. The adsorption kinetics followed the pseudo-second-order kinetics. The thermodynamic have revealed that the adsorption process is endothermic and favorable.

SBA-15 templating synthesis of mesoporous bismuth oxide for selective removal of iodide

Mesoporous δ-Bi2O3 samples with high surface area and small crystallite sizes were prepared by using different SBA-15 silicas as hard templates. The latter were synthesized hydrothermally using tetraethylorthosilicate (TEOS), sodium metasilicate (SMS), and water glass (WG) as silica sources. The resulting SBA-15 silicas showed high surface area and pore volume. Among SBA-15 samples studied, the WG-generated SBA-15 exhibited the thinnest pore walls and lowest percentage of complementary pores. Interestingly, SBA-15 obtained from WG gave δ-Bi2O3 with the highest surface area and pore volume. This mesoporous δ-Bi2O3 was applied for the removal of iodide from aqueous solutions and was able to adsorb 2.87mmol/g of iodide at ambient conditions. In addition, mesoporous δ-Bi2O3 displayed high selectivity for iodide removal in the presence of chloride. Due to the high toxicity of the radioactive isotopes of iodine, this substance is required to be immobilized before its release to environment. This work presents a promising sorbent for selective capture of iodide from aqueous solutions.

Bimetallic AgCu/Cu2O hybrid for the synergetic adsorption of iodide from solution

To further improve the capacity of Cu2O to absorb I− anions from solution, and to understand the difference between the adsorption mechanisms of Ag/Cu2O and Cu/Cu2O adsorbents, bimetallic AgCu was doped into Cu2O through a facile solvothermal route. Samples were characterized and employed to adsorb I− anions under different experimental conditions. The results show that the Cu content can be tuned by adding different volumes of Ag sols. After doping bimetallic AgCu, the adsorption capacity of the samples can be increased from 0.02 mmol g−1 to 0.52 mmol g−1. Moreover, the optimal adsorption is reached within only 240 min. Meanwhile, the difference between the adsorption mechanisms of Ag/Cu2O and Cu/Cu2O adsorbents was verified, and the cooperative adsorption mechanism of the AgCu/Cu2O hybrid was proposed and verified. In addition, the AgCu/Cu2O hybrid showed excellent selectivity, e.g., its adsorption efficiencies are 85.1%, 81.9%, 85.9% and 85.7% in the presence of the Cl−, CO32−, SO42− and NO3− competitive anions, respectively. Furthermore, the AgCu/Cu2O hybrid can worked well in other harsh environments (e.g., acidic, alkaline and seawater environments). Therefore, this study is expected to promote the development of Cu2O into a highly efficient adsorbent for the removal of iodide from solution.

Synthesis of Cu/Cu2O hydrides for enhanced removal of iodide from water

In order to improve the removal capacity of Cu2O for I− anions from water, Cu/Cu2O hybrids have been synthesized through a facile hydrothermal route, characterized by using SEM, XRD, XPS, and applied to remove I− anions under different experimental environments. The results demonstrate that the Cu content and morphology of samples can be tuned by the adding amount of ammonia. Meanwhile, the possible crystalline mechanism, Cu2O formed firstly and then metallic Cu generated, was presented. With the increasing of Cu doped amount, the removal capacity of Cu/Cu2O hybrids increased significantly from 0.02mmolg−1 to 0.18mmolg−1. Furthermore, a reaction mechanism of I− anions and Cu2O, which generated from the disproportionation reaction of metallic Cu and CuO, has been proposed according to the characterization analyses of the composites before and after adsorption, explaining the highly efficient removal of I− anions. In addition, Cu/Cu2O hybrids showed excellent selectivity for I− anions in the presence of large concentrations of competitive anions such as SO42− and NO3− and could work in an acidic and neutral environment. This study is hopefully to prompt Cu2O to grow up to be a new and highly efficient adsorbent for the removal of iodide from solutions.

Halide removal from aqueous solution by novel silver-polymeric materials

The objective of this study was to analyze the behavior of a new material, silver-doped polymeric cloth (Ag-cloth), in the removal of bromide and iodide from waters. Silver is immobilized on the cloth, guaranteeing selective adsorption of the halide ions as retained silver halides that therefore do not pass into the solution. Results indicate that Ag0 reacts with H2O2 in the first phases of the process, yielding Ag+ and superoxide radical; however, as the process advances, this radical favors Ag+ reduction. Increases in the concentration of H2O2 augment the capacity of the Ag-cloth to remove halides from the medium up to a maximum concentration (55μM), above which the removal capacity remains constant (Xm≅1.3–1.8mg halide/g Ag-cloth). Thus, when there is excess H2O2 in the medium, secondary competitive reactions that take place in the process guarantee a constant Ag+ concentration, which defines the maximum adsorption capacity of Ag-cloth, reducing its ability to remove halides. Ag-cloth has a higher capacity to remove iodide than bromide, and the presence of organic matter or chloride reduces its capacity to remove iodide or bromide from water. The results obtained shown that the capacity of Ag0 with H2O2 significantly varies as a function of the medium pH from 1mg Br−/g Ag-cloth at very low pH to 1.6mg/g Ag-cloth at pH9.

Removal of radioactive iodide from simulated liquid waste in an integrated precipitation reactor and membrane separator (PR-MS) system

A novel integrated precipitation reactor (PR) and membrane separator (MS) system was developed for the removal of radioactive I− from simulated liquid waste. The PR-MS system was evaluated at the lab-scale, the I− removal efficiency reached approximately 97.0% and the concentration factor (CF) value was 1050 when the concentration of added Na2SO3 was 40 mg/L and the CuCl dosage was 260 mg/L. The addition of Na2SO3 played an important role in the removal of dissolved oxygen (DO) and the formation of CuI. These reactions, including the oxidation of SO32−, the dissociation of CuCl, the disproportionation of Cu+, and the formation of CuI and Cu2O, occurred in the PR. Furthermore, the influence of the concentration of added CO32− on copper removal was investigated, and solid-liquid separation and copper removal were simultaneously attained in the MS. The I− removal efficiency gradually decreased from 97.0% to 58.5% and the Cu2+ concentration in the effluent decreased from 18.71 mg/L to 0.719 mg/L with the addition of CO32− at a concentration that ranged from 0 to 80 mg/L. Experimental results show the PR-MS system is of great potential for industrial application on treatment of liquid waste contaminated with radioactive I−.

Chemical RedOx Properties of a Donor-Acceptor Conjugated Microporous Dithienothiophene-Benzene co-Polymer FormedviaSuzuki-Miyaura Cross-coupling

An electron rich conjugated microporous polymer (CMP) was prepared after reacting a dithienothiophene (DTT) derivative and benzene as co-monomers by Suzuki-Miyaura polycondensation. Gas sorption measurements revealed a Brunauer–Emmett–Teller (BET) surface area of 421 m2g−1 for the network. Its chemical oxidation was performed via iodine exposure, which is fully reversible with ammonia treatment resulting in a complete removal of the oxidants. This was observed in a decrease and recovery of the initial porosity due to reversible introduction and removal of iodide within the micropores, which could also be monitored by IR and UV/Vis absorption spectroscopy during the RedOx process.

First principles computational study on the adsorption mechanism of organic methyl iodide gas on triethylenediamine impregnated activated carbon.

We study removal of gas-phase organic methyl iodide (CH3I) from an ambient environment via adsorption onto triethylenediamine (TEDA) impregnated activated carbon (AC). First principles density functional theory (DFT) calculations and ab-initio molecular dynamics (AIMD) simulations were extensively utilized to understand the underlying mechanism for the chemical reaction of CH3I on the surface. Our results suggest that the adsorption energy of CH3I shows substantial heterogeneity depending on the adsorption site, porosity of the AC, and humidity. It is observed that the CH3I dissociative chemisorption is largely influenced by the adsorption site and porosity. Most importantly, it is clearly shown through free energy diagrams that the impregnated TEDA not only reduces the dissociation activation barrier of CH3I but also attracts H2O molecules relieving the AC surface from poisoning by humidity, and also enhances the removal efficiency of CH3I through the chemical dissociation reaction. Our computational study can help to open new routes to design highly efficient materials for removing environmentally and biologically hazardous materials, for example radioactive iodine gas emitted following accidents at a nuclear power plant.

Shape‐Controlled Preparation of Basic Bismuth Nitrate Crystals with High Iodide‐Removal Capacities

AbstractBismuth compounds have generated much interest as agents for the removal of radioactive iodine. In this work, we present the shape‐controlled preparation of basic bismuth nitrate crystals (BBN) in the form of Reuleaux triangles, hexagons, and deformed hexagon disks. Shape control was achieved through modulation of the effect of the shape‐directing agent 2,3‐bis(2‐pyridyl)pyrazine (dpp). The crystals were shown to be capable of iodide removal through reaction with I− to form BiOI. Depending on the degree of saturation, the resultant solids can exhibit colors ranging from yellow (unsaturated) to orange (saturated). Sedimentation of the products facilitates its removal after use. While the removal capacities did not depend on the crystal morphology, the Reuleaux triangle disks exhibited faster reaction rates than the other two shapes. With improved removal capacities of up to 3.6 mmol g−1, fast removal kinetics, good selectivity, and capture irreversibility, the BBN crystals show good potential as agents for radioactive iodine removal.

Comparing a silver-impregnated activated carbon with an unmodified activated carbon for disinfection by-product minimisation and precursor removal

During disinfection, bromide, iodide and natural organic matter (NOM) in source waters can lead to the formation of brominated and/or iodinated disinfection by-products (DBPs), which are often more toxic than their chlorinated analogues. The objective of this study was to compare the efficiency of a silver-impregnated activated carbon (SIAC) with the equivalent unimpregnated granular activated carbon (GAC) for the removal of bromide, iodide and NOM from a matrix of synthetic waters with variable NOM, halide, and alkalinity concentrations, and to investigate the impact on DBP formation. An enhanced coagulation (EC) pre-treatment was employed prior to sample exposure to either carbon adsorbent. Excellent halide removals were observed by the SIAC treatment across the sample matrix, with iodide concentrations consistently reduced to below the method reporting limit (<2μg/L) from as high as 25μg/L, and 95±4% removal of bromide achieved. Bromide removal by unimpregnated GAC was poor, however iodide removal was comparable to that achieved by SIAC. The combination of EC with SIAC treatment removed 77±8% of the dissolved organic carbon (DOC) present, across the sample matrix, which was similar to removals by EC/GAC (67±14%). Combined EC/SIAC treatment reduced both total trihalomethanes (tTHMs) and total dihaloacetonitriles (tDHANs) formation by 97±3%, while also achieving a greater than 74% removal of two chloropropanones and a 92±8% decrease in chloral hydrate (CH), compared to untreated samples, regardless of the sample's starting water quality (bromide, alkalinity and NOM concentration). Combined EC/GAC treatment led to similar DBP removals to EC/SIAC for the fully chlorinated DBPs, however, brominated DBPs were less efficiently removed, or experienced concentration increases.

An investigation into the use of cuprous chloride for the removal of radioactive iodide from aqueous solutions

Cuprous chloride (CuCl) was examined as a precipitant to remove iodide (I−) from aqueous solutions. The effects of the dosage of CuCl, reaction time, initial concentrations of I− and bicarbonate (HCO3−) on I− removal were investigated. The results showed that the optimized removal efficiency of I− reached approximately 95.8% when the dosage was 150mg/L, the initial I− concentration ranged from 5 to 40mg/L and the reaction time was 15min. The removal efficiency decreased from 95.8% to 76.0% with the addition of HCO3− at a concentration in the range of 0–107mg/L. Furthermore, the dissociation of CuCl, the disproportionation reaction of Cu+, the precipitation of cuprous iodide (CuI) and cuprous oxide (Cu2O), and the formations of copper sulfide (CuxS, 1≤x<2) were identified as the primary reactions using the PHREEQC software and the measurements of water quality parameters under various conditions. X-rays photoelectron spectroscopy (XPS) analysis was performed before and after the reaction, helping to elucidate the reaction mechanism. This study can provide a promising method to address radioactive I− pollution in water.

Enhanced removal of iodide from water induced by a metal-incorporated porous metal–organic framework

Silver(I) was successfully loaded into the water-stable MOF, MIL-101(Cr)-SO3H, via ion exchange process. Uniform distribution of –SO3H groups in the porous MOF and strong ionic interaction between –SO3− and silver(I) can prompt the distribution of silver(I) homogeneous in the resulted MIL-101(Cr)-SO3Ag. As a proof-of-concept demonstration, MIL-101(Cr)-SO3Ag was applied to the removal of iodide from aqueous solution, which is the first time to remove such toxicant using MOFs to the best of our knowledge. MIL-101(Cr)-SO3Ag shows a high iodide adsorption capacity of 244.2mgg−1, much higher than that of the unmodified sample (94.1mgg−1). Thus, we provide a convenient approach of loading metal ion in MOFs with the help of organic functional groups for the specific target.

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.

Preparation of Porous Zirconia-Yttria Ceramics by Thermal Removal of Potassium Iodide

Zirconia-8 mol% yttria porous solid electrolytes were obtained by mixing with different amounts (0 to 5 wt.%) of KI prior to sintering. Potassium iodide acts as sacrificial pore former, being removed from the ceramic pellet upon sintering at 1400 °C/2 h. The alkali halide content was evaluated by X-ray fluorescence analysis, the density of the pellets by the Archimedes method, and the pore content by observation in scanning probe (SPM) and scanning electron (SEM) microscopes of polished and etched surfaces. The oxide ion resistivity was determined by impedance spectroscopy analysis in the 5 Hz-13 MHz frequency range from 300 to 500 °C. Porous specimens with high skeletal density were obtained. The higher is the alkali halide content, the higher is the pore volume and the total electrical resistivity. A correlation is found between the pore content, evaluated by SEM and SPM, and the electrical behavior analysis from the impedance plots of the porous specimens.

Preparation of Porous Yttria-Stabilized Zirconia Ceramics By Thermal Removal of Potassium Iodide

Near to full skeletal density ZrO2:8 mol% Y2O3 polycrystalline ceramics with different pore content were prepared by mixing different amounts of KI and thermally removing them during sintering at 1400oC. That removal of the alkali halide was evaluated by thermogravimetric and dilatometric measurements from room temperature to 1500oC. The sintered pellets were analyzed by X-ray diffraction and X-ray fluorescence (XRF) for structural phase identification and KI content, respectively. Images of the polished and thermally etched surfaces were obtained by scanning probe microscopy (SPM) and scanning electron microscopy (SEM) for evaluation of average pore content and distribution. Electrochemical impedance spectroscopy measurements were carried out in the 300-450oC range in the 5 Hz-10 MHz frequency range. The thermal removal of KI starts at its melting point, ~ 680oC and ends at ~ 900oC. No traces of KI are found by XRF analysis in sintered pellets. The final linear shrinkage value is higher for compositions without KI and the temperature of maximum shrinkage rate increases for increasing KI content. The total oxide ion electrical resistivity, extracted from the impedance plots, also increases for increasing KI content. The SPM images observed at polished and thermally etched surfaces of sintered pellets show that the larger is the amount of KI addition, the larger is the average pore size and the smaller is the average grain size. The effect of KI addition before sintering leads, upon sintering, dense porous ceramics with high skeletal density. Moreover, grain growth is inhibited. The impedance spectroscopy results allowed for the evaluation of the bulk and the grain boundary conductivities. The increase in both contributions with the increase in KI addition was correlated to the observation by scanning probe microscopy of the increase of intragranular as well as of intergranular porosity. Other parameters determined after the deconvolution of the impedance plots, namely, the blocking factor, the frequency factor and the descentralization angle showed that the impedance spectroscopy technique is an important tool for the characterization of porous ionic conducting solids.

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.

&lt;b&gt;Preparation of a chitosan-based anionic exchanger for removal of bromide, chloride, iodide and phosphate ions from aqueous solutions

The development of a chitosan anion exchanger, obtained from shrimp shells, and its adsorption capacity for chloride, bromide, iodide and phosphate anions are provided. Dependence of exchange processes with the anions as a function of pH and contact time between exchanger and anions were initially investigated. Results showed that the best adsorption of ions occurred at pH 3.0. Exchange isotherms were then developed by the Langmuir, Freundlich and Dubinin-Radushkevich mathematical models. Results demonstrated that chitosan produced from shrimp shells may be used as feedstock in the manufacture of anion exchange microspheres.

Zeolitic adsorption in course of pollutants mitigation and environmental control

The review focuses on the adsorption and selectivity properties of the inland natural zeolites clinoptilolite and mordenite towards a broad spectrum of environmental pollutants incl. radioactive and compare some of them partially to selected foreign samples. A series of elution experiments into a broad spectrum of individual isomolar metal solutions by means of NH4 +—exchanged clinoptilolite—and mordenite-rich tuffs was done to prove the affinity sequence of both minerals untill the steady-state approaching. Among the all recorded breakthrough profiles onto mordente-rich tuff the ammonium exchanged tuff yielded the best uptake performance towards Cs. Three various clinoptilolite-rich tuff samples (Hungarian, American and Slovakian) were compared to each other in order to evaluate the iodide removal in dynamic regime by using the Ag exchanged tuff.

Removal of iodide from aqueous solutions by polyethylenimine-epichlorohydrin resins

The iodide removal from aqueous solutions (initial I−-concentration: 300–5,000 mg/L) by a low and a high molecular weight polyethylenimine-epichlorohydrin resin was investigated both in absence and presence of background electrolytes (NaCl and Na2SO4, ionic strength due to background electrolyte 0.1 M) using a batch technique, 131I as radioactive tracer and high-resolution γ-ray spectrometry. The experiments in absence of background electrolyte were performed using solutions of initial pH 3 and 7, whereas those in presence using solutions of initial pH 3. The results, which demonstrated the high iodide-removal efficiency of both resins, were modeled using the Langmuir and Freundlich isotherm equations. The experimental data were better reproduced using the Langmuir equation. Using this equation maximum sorption capacity values (Q max) of 638.8 and 603.3 mg/g were obtained for the high molecular weight resin from solutions of initial pH 3 and 7 respectively, whereas the corresponding values for the low molecular weight one were slightly lower (552.4 and 507.5 mg/g respectively). The iodide uptake by the resins strongly depended on the presence of competing anions and especially of sulfates. The examination of sections of the I-loaded resins grains by scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) revealed that iodine was evenly distributed throughout the bulk of the resins and not only bound to their surface.

Hemodialysis in Patients Requiring131I Treatment for Thyroid Carcinoma

Thyroid malignancies can be treated by surgery followed by ablation of the remnant tissue with 131I. As iodide removal from the body occurs by renal extraction, in patients suffering from end-stage renal disease it is necessary to properly evaluate both timing and method of the extracorporeal treatment. We present two patients on regular hemodialysis, admitted in isolation to the Nuclear Medicine Department and treated with 131I for thyroid carcinoma diagnosed during the check-up for transplantation. Both patients underwent two hemodialysis sessions with a portable machine for CRRT (continuous renal replacement therapy), 24 and 48 hours after the administration of 50 mCi of 131I. The nursing staff were monitored with a dosimeter. Radioactivity of the patients, dialysate and urines were measured during hemodialysis. The greater reduction was obtained with the first dialysis, but in both patients a further, though shorter, hemodialysis at 48 hours was necessary for reaching a patient's radioactivity compatible with discharge. Radioactivity measured in the dialysate demonstrated the almost total removal of radioiodine by dialysis alone. In both patients, follow-up exams revealed a complete ablation of thyroid tissue, without signs of local recurrence. The dose of radioactivity of the dialysis staff was below allowable limits. We conclude that a successful reduction of radioactivity, without dispersing its therapeutic efficacy, can be obtained with daily hemodialysis with a CRRT machine in patients in isolation treated with 131I. A therapeutic model is proposed.