Adsorption Of Iodide Research Articles

Facile synthesis of mesoporous Fe-based MOFs loading bismuth with high speed adsorption of iodide from solution

To improve the uptake effect of iodide anions from aqueous solution, mesoporous Fe-based MOFs (Bi@MIL) were prepared by mixing Bi(III) and MIL-101(Fe) in Teflon-lined autoclave using solvothermal synthetic method. The Bi@MIL adsorbents were characterized by IR, XRD, SEM, BET and XPS, indicating the crystal structure of MIL-101(Fe) remained when the addition of Bi(III) species in the synthesis of Bi@MIL was below 5.0%. When the amount of Bi(III) reached 15.0%, mesoporous Fe-based MOFs was obtained. Bi@MIL composites displayed fast adsorption kinetics and the adsorption equilibrium was achieved in 20 min in 200 mg L−1 of iodide anions solution concentration at neutral medium. The pH of solution could affect adsorption of iodide anions and the maximum adsorption capacities occurred at pH 3.

Building High‐Density Au–Ag Islands on Au Nanocrystals by Partial Surface Passivation

AbstractAs an advanced level of control in colloidal synthesis, it is highly desirable to create secondary structures of nanocrystals in a controllable manner for collective properties. Of particular interest is the generation of nanoislands of plasmonic metals (Ag and Au) at a high density around their pre‐existing primary nanocrystals, which may produce abundant hotspots for surface‐enhanced Raman scattering (SERS). Often such secondary structures are difficult to be achieved by direct crystal growth because a conformal growth is favorable due to the lattice match of these metals. Here, this challenge is overcome by developing a partial surface passivation strategy which can effectively shift the crystal growth mode from the “Frank–van der Merwe” mode to the “Volmer–Weber” mode, giving rise to nanoislands as a secondary structure on Au nanocrystals. The key to this strategy is the modification of the Au surface with Ag and subsequent adsorption of iodide at the Ag sites. Further deposition of Au on the modified surface leads to the formation of well‐defined Au–Ag alloy islands of a high density on Au nanocrystals, which exhibit excellent SERS activity. This partial surface passivation strategy is fundamentally important and may inspire further endeavors in pursuit of novel secondary nanostructures and intriguing properties.

Understanding the Effect of Iodide Ions on the Morphology of Gold Nanorods

AbstractThe presence of iodide ions during the growth of gold nanorods strongly affects the shape of the final products, which is proposed to be due to selective iodide adsorption on certain crystallographic facets. Therefore, a detailed structural and morphological characterization of the starting rods is crucial toward understanding this effect. Electron tomography is used to determine the crystallographic indices of the lateral facets of gold nanorods, as well as those present at the tips. Based on this information, density functional theory calculations are used to determine the surface and interface energies of the observed facets and provide insight into the relationship between the amount of iodide ions in the growth solution and the final morphology of anisotropic gold nanoparticles.

Vibration spectroscopic evidence for different interactive modes of iodide on gibbsite in humic acid mediation

Determination of the fate of iodide and associated species is an important scientific question from environmental and nuclear energy perspectives. The chemical kinetics of iodide adsorption on gibbsite was examined in the presence of humic acids (HA). The iodide retention was highest in HA-coated gibbsite (ΓI 15.5 μmol m2−; pH 6.50) and lowest in HA-iodide-gibbsite ternary systems (ΓI 9.56 μmol m2−; pH 6.50). Both inter- and intralayer OH groups have distinguishable IR manifestations for iodide retention on gibbsite. In HA-coated gibbsite, the enhanced iodide retention was ascribed to direct bonding with surface Al-sites.

Modulating iodine adsorption in nanoporous metal-organic framework via cation exchange process

An anionic Zn(II) Metal-Organic Framework, [HDMA]2[Zn2(BDC)3(DMA)2].6DMF (HDMA+: dimethylamonnium, BDC2−: 1,4-benzenedicarboxilate, DMA: dimethylamine, DMF: N,N′-dimethylformamide), was served as a host for encapsulating I2. For comparison of the ad/desorption rates of iodide, the ion exchange process with organic cations have been done. Loading of the exchanged compounds were successfully done by suspending them in a solution of I2 in cyclohexane. Powder X-ray diffraction experiments and IR analysis showed that the exchanged crystalline lattices after adsorption and desorption of iodide remained the same. The delivery of I2 from the compounds performed in ethanol, were determined by UV/vis spectroscopy. Comparison of iodide adsorption and desorption rates in the exchanged compounds showed that presence of different organic cations have effective role in increasing iodine adsorption.

Investigation of gaseous wet methyl iodide adsorption on Ag nanoparticles embedded in organic–inorganic hybrid silica gels

X-ray photoelectron spectroscopy (XPS), single-particle photoluminescence, and lifetimes were adopted to investigate the interaction properties between gaseous wet methyl iodide (CH3I) and Ag nanoparticles (Ag NPs), which are embedded into a propylethylenediamine (NH2CH2CH2NHCH2CH2CH2-, PEDA) anchored silica gel. Based on the obtained XPS resolutions and shifts of binding energies, a stronger interaction of CH3I than Ag NPs toward SiO2, methylation of amines and silanols by CH3I, the partial interaction in the Ag NPs and CH3I interface, condensation of SiO2 and PEDA, and stabilization of Ag NPs by PEDA were explained. In addition, an enhanced luminescence of Ag NP-embedded PEDA-anchored SiO2 gel (Ag NP-PEDA gel) by surrounding CH3I, and Ag NP stabilization by PEDA and CH3I were also observed from the single-particle photoluminescence and lifetimes.

Salt effects in surfactant-free microemulsions.

The weakly associated micellar aggregates found in the so-called "pre-ouzo region" of the surfactant-free microemulsion water/ethanol/1-octanol are sensitive to changes in the system composition and also to the presence of additives like salt. In this work, we study the influence of two salts, sodium iodide and lithium chloride, on aggregates in water/ethanol/1-octanol by molecular dynamics simulations. In both cases, ethanol concentration in the nonpolar phase and at the interface is increased due to a salting out effect on ethanol in the aqueous pseudo-phase. In addition, minor charging of the interface as a consequence of differential adsorption of anions and cations occurs. However, this charge separation is overall weakened by the erratic surface of octanol aggregates, where polar hydroxyl groups and hydrophobic patches are both present. Furthermore, ethanol at the interface shields hydrophobic patches and reduces the preferential adsorption of iodide and lithium.

Magnetite nanoparticles supported on organically modified montmorillonite for adsorptive removal of iodide from aqueous solution: Optimization using response surface methodology

Magnetite nanoparticles supported on organically modified montmorillonite (MNP-OMMTs) were successfully synthesized by a facile coprecipitation method. The surface of natural clay was modified using a cationic surfactant, hexadecyltrimethylammonium. The synthesized MNP-OMMTs were used as an adsorbent to remove iodide from aqueous solutions. The maximum adsorption capacity of the adsorbent was 322.42mg/g, which is much higher than other previously reported adsorbents for removing iodide in aqueous solution. The experimental data were well fitted to a pseudo-second-order kinetic model, and the adsorption behavior followed the Langmuir isotherm. A thermodynamic study indicated that iodide adsorption was spontaneous and endothermic. The individual and combined effects of key process parameters (pH, temperature, and initial iodide concentration) were studied using a response surface methodology. The maximum iodide removal efficiency of 93.81% was obtained under the optimal conditions of pH3.9, a temperature of 41.3°C, and an initial iodide concentration of 113.8mg/L.

Oriented Au nanoplatelets on graphene promote Suzuki-Miyaura coupling with higher efficiency and different reactivity pattern than supported palladium

Facet 111 oriented Au nanoplatelets (20–40nm wide, 3–4nm height) grafted on graphene (Au‾/fl-G) are about three orders of magnitude more efficient than Pd nanoparticles supported on graphene to promote Suzuki-Miyaura coupling. In contrast to Pd catalysis, it is shown here that the product yields in Suzuki-Miyaura coupling catalyzed by Au nanoparticles follow the order chlorobenzene>bromobenzene>iodobenzene. Kinetic studies show that this reactivity order is the result of the poisoning effect of halides for Au that is much higher for I− than Br− and much higher than for Cl−, due to adsorption. This strong iodide adsorption leading to Au catalyst deactivation was predicted by DFT calculations of Au clusters. Au‾/fl-G are about one order of magnitude more efficient than small Au nanoparticles (4–6nm) obtained by the polyol method supported on graphene. Our results can have impact in organic synthesis, showing the advantage of Au‾/fl-G as catalyst for Suzuki-Miyaura couplings.

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.

Sorption of iodide (I−) from aqueous solution using Mg/Al layered double hydroxides

In this article, the authors report the adsorption of iodide by Mg/Al LDHs and thermally activated LDH materials in laboratory scale batch experiments. The optimal Mg/Al cation ratio was 3:1while the percentage iodide uptake increased with increasing adsorbent dose up to 1g/20mL of solution. The effect of initial iodide concentration was investigated using the Langmuir and Freundlich adsorption isotherm models, while the pseudo second order kinetic model appeared to provide the best fit for the experimental data. High iodide uptake of over 80% could be achieved without completely eliminating dissolved or atmospheric carbonate and leaching of 131I from LDHs did not appear to be a significant problem over the period of 28days investigated. These results demonstrate that LDHs, which are already commercially available in large quantities, are a technology that shows considerable promise for the removal of radioiodine from aqueous solution.

Energetics of Adsorbed Methyl and Methyl Iodide on Ni(111) by Calorimetry: Comparison to Pt(111) and Implications for Catalysis

The heat of adsorption and sticking probability of methyl iodide were measured on Ni(111) at 100 and 160 K using single-crystal adsorption calorimetry (SCAC). At 100 K, methyl iodide adsorbs molecularly with a heat of 102 kJ/mol on terrace sites in the low-coverage limit, giving a standard enthalpy of formation (ΔHf°) of CH3I(ad) of −87 kJ/mol. A heat of 122 kJ/mol is also measured on defect sites, probably step edges. Calorimetry of the dissociative adsorption of methyl iodide on Ni(111) at 160 K yielded an integral heat of adsorption of −270 kJ/mol at 0.04 ML, providing the energetics of adsorbed methyl, with ΔHf°[CH3(ad)] = −71 kJ/mol and a CH3–Ni(111) bond enthalpy of 218 kJ/mol. This is 22 kJ/mol stronger than the reported value for H3C–Pt(111) bonds, explaining the greater activity of Ni catalysts for hydrogenolysis in comparison to Pt. The measured energetics for methyl were compared to density functional theory (DFT) calculations from previous literature, showing that these methods systematically ...

Combined DFT and XPS investigation of iodine anions adsorption on the sulfur terminated (001) chalcopyrite surface

The adsorption of iodine anions (iodide and iodate) on the sulfur terminated (001) chalcopyrite surface has been systematically investigated combining first-principles calculations based on density functional theory (DFT) with X-ray photoelectron spectroscopy (XPS) measurements. Based on the total energy calculations and geometric optimization, the thermodynamically preferred site was copper atom for iodide adsorption and iron atom for iodate adsorption, respectively. In the case of Cu site mode, the iodate underwent a dissociative adsorption, where one IO bond of iodate ion was broken and the dissociative oxygen atom adsorbed on the adjacent sulphur site. Projected density of states (PDOS) analysis further clarified the interaction mechanism between active sites of chalcopyrite surface and adsorbates. In addition, full-range XPS spectra qualitatively revealed the presence of iodine on chalcopyrite surface. High resolution XPS spectra of the I 3d peaks after adsorption verified the chemical environment of iodine. The binding energies of 618.8eV and 623.5eV for I 3d5/2 peaks unveiled that the adsorption of iodide and iodate ions on copper-iron sulfide minerals was the result of formation of low solubility metal iodides precipitate. Also two I 3d peaks with low intensity around 618eV and 630eV might be related to the inorganic reduction of iodate to iodide by reducing S2− ion of chalcopyrite.

How specific halide adsorption varies hydrophobic interactions

Hydrophobic interactions (HI) are driven by the water structure around hydrophobes in aqueous electrolytes. How water structures at hydrophobic interfaces and how this influences the HI was subject to numerous studies. However, the effect of specific ion adsorption on HI and hydrophobic interfaces remains largely unexplored or controversial. Here, the authors utilized atomic force microscopy force spectroscopy at well-defined nanoscopic hydrophobic interfaces to experimentally address how specific ion adsorption of halide ions as well as NH4 (+), Cs(+), and Na(+) cations alters interaction forces across hydrophobic interfaces. Our data demonstrate that iodide adsorption at hydrophobic interfaces profoundly varies the hydrophobic interaction potential. A long-range and strong hydration repulsion at distances D > 3 nm, is followed by an instability which could be explained by a subsequent rapid ejection of adsorbed iodides from approaching hydrophobic interfaces. In addition, the authors find only a weakly pronounced influence of bromide, and as expected no influence of chloride. Also, all tested cations do not have any significant influence on HI. Complementary, x-ray photoelectron spectroscopy and quartz-crystal-microbalance with dissipation monitoring showed a clear adsorption of large halide ions (Br(-)/I(-)) onto hydrophobic self-assembled monolayers (SAMs). Interestingly, iodide can even lead to a full disintegration of SAMs due to specific and strong interactions of iodide with gold. Our data suggest that hydrophobic surfaces are not intrinsically charged negatively by hydroxide adsorption, as it was generally believed. Hydrophobic surfaces rather interact strongly with negatively charged large halide ions, leading to a surface charging and significant variation of interaction forces.

Capture of Elemental and Organic Iodine from Dilute Gas Streams by Silver-exchanged Mordenite

The treatment of off-gas streams arising from reprocessing of used nuclear fuel (UNF) is an area of active study by the U.S. Department of Energy. Such off-gas streams contain volatile fission products, including long-lived 129I. Although 129I is released into the off-gas at multiple points within the chemical reprocessing flowsheet, previous research has focused on removal from the dissolver off-gas stream (DOG). The DOG is expected to contain up to 98% of iodine in UNF at ppm levels within the stream. Other off-gas streams will also contain iodine but at substantially lower concentrations. Recent work has shown that compliance with U.S. regulations will likely require capture of iodine from these dilute streams in addition to capture from DOG.In particular, the vessel off-gas (VOG) stream is expected to contain 1-3% of the total iodine inventory at ppb concentrations. A review of literature also indicates that the speciation of iodine in the VOG stream will differ from that of the DOG, with the DOG containing primarily I2 and the VOG containing a mixture of I2 and organic iodine species.Silver-exchanged mordenite (AgZ) has been identified for use in the removal of iodine from off-gas streams. It is an effective capture material for I2 at the concentrations expected in the DOG, but little is known about its performance in gas streams that may contain both I2 and organic iodides at very dilute concentrations.The experiments to be described were designed to separately characterize the adsorption of I2 and methyl iodide on AgZ through extended duration testing. Simulated vessel off-gases containing low levels of either I2 or methyl iodide were contacted with AgZ sorbent beds for up to four months. Through the use of sorbent beds in series and varied sampling times, key parameters such as adsorption rate, decontamination factor, and performance over time could be determined for the capture of each species by AgZ.This paper will discuss the literature relating to the speciation of iodine in the VOG and will discuss the results of adsorption experiments. An examination of the difference between capture of I2 and organic iodides will be conducted, and the impacts of those results on future iodine removal work will be considered.

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.

Experimental measurement and modelling of reactive species generation in TiO2 nanoparticle photocatalysis

The generation of reactive species in titanium dioxide (TiO2) nanoparticle photocatalysis was assessed in a laboratory scale setup, in which P25 Aeroxide TiO2 suspensions were photoactivated by means of UV-A radiation. Photogenerated holes and hydroxyl radicals were monitored over time by observing their selective reaction with probe compounds, iodide and terephthalic acid, respectively. TiO2 aggregate size and structure were characterized over the reaction time. Reactive species quenching was then described by a model, accounting for radiative phenomena, TiO2 nanoparticle aggregation and kinetic reactions. The interaction between iodide and photogenerated holes was influenced by iodide adsorption on TiO2 surface, described by a Langmuir–Hinshelwood mechanism, whose parameters were studied as a function of TiO2 concentration and irradiation time. Iodide oxidation was effectively simulated by modelling the reaction volume as a completely stirred two-dimensional domain, in which irradiation phenomena were described by a two-flux model and the steady state for reactive species was assumed. The kinetic parameters for iodide adsorption and oxidation were estimated and successfully validated in a different experimental setup. The same model was adapted to describe the oxidation of terephthalic acid by hydroxyl radicals. The kinetic parameters for terephthalic acid oxidation were estimated and validated, while the issues in investigating the interaction mechanisms among the involved species have been discussed. The sensitivity of operating parameters on model response was assessed and the most relevant parameters were highlighted.

Preparation of Silver Nanoparticles Film and the Adsorption of Iodide

Iodine and iodine compounds are widely applied in medicaments,dyes,energy materials,food additives etc.The development and utilization of iodine resources have attracted much attention.A large amount of iodide is

Method for direct deconvolution of heat signals in transient adsorption calorimetry

Abstract A method of heat signal analysis is presented for transient adsorption calorimetries including single crystal adsorption calorimetry (SCAC) which uses fast Fourier transforms (FFT) to determine the instrument response function and deconvolute the heat-versus-time signals. The method utilizes a heat signal generated by a laser pulse of known power-versus-time to extract the instrument response function for the calorimeter. The instrument response function is then used to extract the heat power signal from a molecular beam heat pulse of unknown intensity. This method allows for the extraction of the total heat deposited by the molecular beam pulse without any kinetic modeling even in the event of complex reaction dynamics. This method is compared to previous methods used to analyze SCAC data using example data from the two-step dissociative adsorption of methyl iodide on Pt(111). It is found to be equally accurate for extracting total heats and simpler to perform than the previous methods.

Enhanced coagulation with powdered activated carbon or MIEX® secondary treatment: A comparison of disinfection by-product formation and precursor removal

The removal of both organic and inorganic disinfection by-product (DBP) precursors prior to disinfection is important in mitigating DBP formation, with halide removal being particularly important in salinity-impacted water sources. A matrix of waters of variable alkalinity, halide concentration and dissolved organic carbon (DOC) concentration were treated with enhanced coagulation (EC) followed by anion exchange (MIEX® resin) or powdered activated carbon (PAC) and the subsequent disinfection by-product formation potentials (DBP-FPs) assessed and compared to DBP-FPs for untreated samples. Halide and DOC removal were also monitored for both treatment processes. Bromide and iodide adsorption by MIEX® treatment ranged from 0 to 53% and 4–78%, respectively. As expected, EC and PAC treatments did not remove halides. DOC removal by EC/PAC was 70 ± 10%, while EC/MIEX® enabled a DOC removal of 66 ± 12%. Despite the halide removals achieved by MIEX®, increases in brominated disinfection by-product (Br-DBP) formation were observed relative to untreated samples, when favourable Br:DOC ratios were created by the treatment. However, the increases in formation were less than what was observed for the EC/PAC treated waters, which caused large increases in Br-DBP formation when high Br-DBP-forming water quality conditions occurred. The formation potential of fully chlorinated DBPs decreased after treatment in all cases.