Iodine In Cyclohexane Research Articles

Synthesis of magnetic-responsive imidazole-based poly (ionic liquid)s as a recycle adsorbent for simultaneously removing iodine molecules and iodide ions

Nuclear waste management and nuclear energy generation require the proper disposal of 129I and 131I, which are radioactive isotopes of iodine. For recognition of different types’ iodine, a magnetic poly (ionic liquid)s (Fe3O4@SiO2-MPS-PILs) was formed by the selected imidazole ionic liquid monomer and core–shell Fe3O4@SiO2-MPS via free radical polymerization. The resulting adsorbent containing plenty of imidazole N-heterocycle units, benzene rings, and ionic bonds in the backbones was suitable for simultaneously adsorbing iodine molecules and iodide ions. The adsorption mechanisms for iodine in cyclohexane and iodide ions from aqueous solution were based on charge transfer and ion exchange mechanisms, respectively. The adsorption equilibrium for iodine in cyclohexane was attained at 12 h, and the kinetics of iodine adsorption closely followed the pseudo-second-order model. Iodine adsorption on Fe3O4@SiO2-MPS-PILs was best described by Langmuir model with a maximum iodine adsorption capacity of approximately 714.29 mg g−1. Iodide ions adsorption was best explained with Freundlich model and a maximum adsorption capacity of 335.80 mg g−1 was achieved in an iodide solution with a 500 mg L–1 concentration. Notably, Fe3O4@SiO2-MPS-PILs retained over 90 % of its original adsorption performance after the 5th cycle. This work proves that the adsorbent Fe3O4@SiO2-MPS-PILs was efficient and recyclable, and has good application prospects in the practical treatment of iodine and iodide.

Construction of Ketoenamine-Based Covalent Organic Frameworks with Electron-Rich Sites for Efficient and Rapid Removal of Iodine from Solution.

Porous covalent organic frameworks (COFs) have been widely used for the efficient removal of iodine from solution due to their abundance of electron-rich sites. In this study, two kinds of ketoenamine-based COFs, TpBD-(OMe)2 and TpBD-Me2, are successfully synthesized via Schiff base reaction under solvothermal conditions using 1, 3, 5-triformylphoroglucinol as aldehyde monomer, o-tolidine and o-dianisidine as amino monomers. The ability of TpBD-(OMe)2 and TpBD-Me2 to adsorb iodine in cyclohexane or aqueous solutions has been quantitatively analyzed and interpreted in terms of adsorption sites. TpBD-Me2 possesses two adsorption sites, -NH- and -C=O, and exhibits an adsorption capacity of 681.67 mg/g in cyclohexane, with an initial adsorption rate of 0.6 g/mol/min with respect to COF unit cell. The adsorption capacity of TpBD-(OMe)2 can be as high as 728.77 mg/g, and the initial adsorption rate of TpBD-(OMe)2 can reach 1.2 g/mol/min in the presence of oxygen atoms between the methyl group and the benzene ring. Compared with TpBD-Me2, the higher adsorption capacity and adsorption rate of TpBD-(OMe)2 towards iodine are not only reflected in organic solvents, but also in aqueous solutions. It is proven through X-ray photoelectron spectroscopy and Raman spectroscopy that iodine exists in the form of I2, I3-, and I5- within TpBD-(OMe)2 and TpBD-Me2 after adsorption. This work not only expands the application of COFs in the field of iodine adsorption, but also provides research ideas and important an experimental basis for the optimization of iodine adsorption sites.

Design and synthesis of stable sp2-carbon-linked two-dimensional conjugated covalent organic framework for efficient capture of iodine

The ingenious design of sp2-carbon-linked fully π-conjugated covalent organic frameworks (sp2-c-COFs) with a periodic pore structure and high chemical stability, is vital. However, this remains a significant challenge owing to the poor reversibility of the coupling reactions. Here two novel isoreticular crystalline and highly porous two-dimensional (2D) sp2-c-COFs (COF-p-NEU1 and COF-p-NEU2) are designed and synthesized via a base-catalyzed Knoevenagel polycondensation reaction based on the [C2 + C3] topology diagram. As-prepared polycrystalline COF-p-NEU1 (with 1,3,5-tris(p-formylphenyl)benzene (TFP)) and COF-p-NEU2 (with 1,3,5‐tris‐(4‐formylphenyl) triazine (TFT)) exhibit long-range ordered structures, well-defined nanochannels, and favorable chemical stable, which endow the promising capture performance of COF materials. Meanwhile, the two sp2-c-COF can provide abundant functional units to promote the capture of I2 due to introducing mass nitrogen species into the building block. Therefore, the two nitrogen-rich sp2-c-COFs exhibit a high iodine uptake capacity for iodine vapor and iodine in cyclohexane with 4.58 g g−1 and for 1.31 g g−1 COF-p-NEU1 and 5.87 g g−1 and 1.51 g g−1 for COF-p-NEU2 at 348 K. The results of this study provide a potential path for the design and synthesis of novel sp2-c-COFs materials with high chemical stability and demonstrate the high potential of sp2-c-COF for the capture of radioactive contaminants.

Hierarchical porous carbon with an ultrahigh surface area for high-efficient iodine capture: Insights into adsorption mechanisms through experiments, simulations and modeling

The removal of radioactive iodine species during nuclear accidents and nuclear fuel reprocessing is crucial to nuclear safety, public health and environmental protection. Here, a series of nitrogen-doped porous carbon derived from benzimidazole (NBCs) with well-developed pore structure were prepared. During KOH activation, the potassium salt formed at 600–700 °C is mainly K2CO3 and K2O, and the pore size obtained is mainly microporous. With the temperature increases, the K2CO3 and K2O are converted to KOCN, which generates mesopores. NBCs were subsequently tested for gaseous iodine and solution iodine. The results show that NBC800-2 exhibits the highest iodine vapor adsorption capacity (7873 mg/g) at 75 ℃. Theoretical calculations and experimental data show that the iodine adsorption of NBCs for iodine vapor is mainly determined by pore structure, especially micropores and narrow mesoporous. The effect of nitrogen and oxygen doping on the adsorption capacity of gaseous iodine is limited. In the cyclohexane solution, the adsorption capacity of NBCs for iodine is mainly determined by micropores. In KI/H2O solution, the iodine adsorption mainly depends on micropores and narrow mesopores, which is completely different from the result of iodine adsorption in cyclohexane. This is mainly due to the fact that I3- has a larger diameter than I2, and the adsorption energy of I3- (82.8 kJ/mol) on the carbon surface is higher than that of I2 (58.1 kJ /mol). Moreover, Langmuir model can better describe the adsorption process of iodine in cyclohexane and KI/H2O solution than Freundlich model, which proves that the process is mainly monolayer formation. This study provides insights for the further design and development of adsorbents for iodine capture from nuclear waste and nuclear accidents.

Calix[4]pyrrole-Based Azo-Bridged Porous Organic Polymer for Bromine Capture.

The toxicity, corrosiveness, and volatility of elemental bromine presents challenges for its safe storage and transportation. Purification from other halogens is also difficult. Here, we report an easy-to-prepare calix[4]pyrrole-based azo-bridged porous organic polymer (C4P-POP) that supports efficient bromine capture. C4P-POP was found to capture bromine as a vapor and from a cyclohexane source phase with maximum uptake capacities of 3.6 and 3.4 g·g-1, respectively. Flow-through adsorption experiments revealed that C4P-POP removes 80% of the bromine from a 4.0 mM cyclohexane solution at a flow rate of 45 mL·h-1. C4P-POP also allowed the selective capture of bromine from a 1:1 mixture of bromine and iodine in cyclohexane.

Scale synthesis of spherical porous porphyrinic organic polymers for efficient iodine capture and CO2 adsorption

Introducing electron-rich groups into the covalent organic polymers (COPs) with porous structure can endow the resulting materials with great potentials in waste gas uptake and nuclear pollutant adsorption. In this work, five porphyrin-based COPs with pyrrole and various aldehyde (bithiophenyl-5,5′-dicarbaldehyde, terephthalaldehyde, 2,6-pyridinedicarboxaldehyde, 1,3,5-benzenetricarboxaldehyde and furan-2,5-dicarbaldehyde) as precursors were constructed by a simple and fast one-pot synthesis procedure within 2 ​h. The production scale of them all reached over 5 ​g. These spherical COPs all showed the capability of rapid and efficient capture of iodine in cyclohexane and CO2 in gas. Iodine in cyclohexane solution of 200 ​cm3 ​g−1 can be almost adsorbed 100% within 3 ​h. The admirable COPs synthesized by terephthalaldehyde and pyrrole exhibit extremely high capture capacity of over 760 ​mg ​g−1 for iodine in solution. Besides, the CO2 uptake on five COPs was also impressive, even with a capacity of 79 ​mg ​g−1. The scale synthesis of novel porphyrinic COPs enabled them to become practically available adsorbents especially for iodine capture.

A pillared double-wall metal-organic framework adsorption membrane for the efficient removal of iodine from solution

• Lac-Zn membrane is prepared and featured with a novel pillared double-wall MOF. • The static adsorption capacity for iodine in cyclohexane is 755 mg·g −1 . • The dynamic adsorption capacity for iodine in aqueous solution is 124.9 μmol·g −1 . • Iodine is captured in lac-Zn membrane by nanochannels and charge-transfer interaction. Effective removal of the radioactive iodine from aqueous solution is imperative but still far from the desired level. Here, a pillared double-wall MOF adsorption membrane comprised of {[Zn 3 (DL-lac) 2 (pybz) 2 ]·2.5DMF} n abbreviated as lac-Zn was reported. The synthesis of the lac-Zn membrane is conducted on the polytetrafluoroethylene (PTFE) support via the seed secondary growth method. A smooth and uniform lac-Zn seed layer can be deposited onto the PTFE support with the combination of the vacuum filtration and spin-coating method, and a continuous and well-intergrown lac-Zn polycrystalline film is formed with a thickness of around 25 μm. Lac-Zn polycrystalline film shows good stabality in the irradiation evironment. The maximum static adsorption capacity of the lac-Zn membrane for iodine ions in cyclohexane solution is 755 mg·g −1 , and corresponding dynamic adsorption capacity in aqueous solution is 31.72 mg·g −1 . In the dynamic adsorption of iodine aqueous solution, the iodine removal efficiency decreases from the initial 92.89% to 78.21% at 216 minutes. The iodine ions were captured by the lac-Zn membrane through the formation of I 3 − anions from the solution. The high iodine capture performance of the lac-Zn membrane can be attributed to the confined nanochannels and considerable pore volume providing enough adsorption sites for iodine ions and the abundant π-electron walls in pybz strengthening the affinity towards iodine.

The high-efficiency and eco-friendly PEGylated ionic liquid systems for radioactive iodine capture through halogen bonding interaction

The kinetics of iodine uptake by eco-friendly PEGylated systems was investigated and the resutls showed that most of the systems could capture iodine from the solution of iodine in cyclohexane efficiently. For example, 86% of iodine could be captured in only 3h by PEG200/NaI system. The efficiency of iodine uptake shows high correlation with the inorganic salts used which might be due to the halogen bonding (XB) interaction between the anion of salt with I2. Besides that, the effect of organic solvents and ionic liquids on the iodine capture were also investigated. The results indicated that PEGylated systems are flexible and reobust for iodine capture, furthermore, they might be applied to other areas as solvents.

Zn-MOFs containing flexible α,ω-alkane (or alkene)-dicarboxylates with 1,2-bis(4-pyridyl)ethylene: comparison with Zn-MOFs containing 1,2-bis(4-pyridyl)ethane ligands

Flexible ditopic α,ω-alkane (or alkene)-dicarboxylate bridging ligands provided the following six Zn-MOFs with a 1,2-bis(4-pyridyl)ethylene (bpe) pillar (malonate (1-bpe), succinate (2-bpe), fumarate (3-bpe), glutarate (4-bpe), adipate (5-bpe), and muconate (6-bpe)). Newly-prepared 5-bpe and 6-bpe were structurally characterized. Both 3-bpe and 6-bpe formed three-dimensional (3-D), diamond-like frameworks with a 4-connected uninodal net and a Schläfli symbol of 66. By contrast, 5-bpe formed a 3-D framework of a 6-connected uninodal net with a Schläfli symbol of 412·63. 2-bpe formed a 2-D framework with a 4-connected uninodal net with a Schläfli symbol of 44·62. 3-bpe and 6-bpe showed potential void spaces after solvent removal. Gas sorption analysis with N2, H2, and CO2 at a suitable temperature indicated that 6-bpe was an adsorbent with selectivity for CO2 adsorption at 196 K over N2 and H2. The CO2 uptake at 196 K was 86.68 cm3 g−1 (3.87 mmol g−1). 3-bpe did not exhibit appreciable uptake levels for N2, H2, and CO2, which was possibly due to the relatively rigid nonporous activated form of the framework after solvent removal. Both 3-bpe and 6-bpe exhibited a good encapsulating ability for molecular iodine in cyclohexane. The crystal structure of I2-containing 6-bpe_I2 was elucidated. A comparison with Zn-MOFs containing 1,2-bis(4-pyridyl)ethane ligands is discussed.

Far IR vibrational spectroscopic studies of the chemical dynamics of the pyridine/iodine system in solution

We have analysed the far infrared spectra of a mixture of pyridine and iodine in cyclohexane in such a way as to elucidate more clearly the role of the short time dynamicsof complex formation. We find that the so called ‘νD-I’ band at 90–120 cm−1 (depending on pyridine concentration) has its origins in the rapid spatial fluctuations between donor and acceptor. We detect experimentally the merging of vibrational and chemical reaction coordinates on the (sub ps) time scale of the experiment.

A very useful and mild method for the protection and deprotection of carboxylic acids

3-Methylbut-2-enyl group is a good protecting group of carboxylic acid that can be removed by using iodine in cyclohexane.

Direct measurement of photodissociation, geminate recombination, and vibrational cooling in iodine using picosecond Raman spectroscopy

The photodissociation and geminate recombination of iodine in cyclohexane has been studied by directly monitoring the vibrational coordinates using transient Raman spectroscopy. Energy relaxation as a function of vibrational energy gap has been measured for vibrational spacings of 210 to 130 cm−1. These vibrational levels correspond approximately to v=3 to v=52 with energies 740 to 9300 cm−1 above the zero point level. The results support earlier experiments in that over 100 ps is required to completely relax the vibrational energy.

Chemistry of bis-spiroacetals. Synthesis of the 1,6,8-trioxadispiro[4.1.5.3]pentadecane ring system

The syntheses of the unsaturated keto epoxide (4) and saturated keto epoxide (18) are described. In both cases, the key step was the nucleophilic addition of the acetylene (10) to δ-valerolactone. Cyclisation of the keto epoxide (18) in the presence of a catalytic amount of camphorsulphonic acid in dichloromethane led to isolation of a single saturated bis-spiroacetal (21). This selectivity can be explained by the preference of spiroacetals to adopt the conformation in which the ring oxygens are axial to the adjacent ring thus gaining stability from the anomeric effect. Analogous protic or Lewis acid-catalysed intramolecular cyclisation of the unsaturated keto epoxide (4) was not successful under a variety of reaction conditions. The unsaturated bis-spiroacetal (24), however, was prepared by an alternative strategy involving an acid-catalysed cyclisation of (22) to form the unsaturated spiroacetal (23) followed by subsequent conversion into a bis-spiroacetal utilising an oxy-radical generated by photolysis. Formation of the unsaturated bis-spiroacetal (24) from (23) was achieved via a Barton-type reaction involving irradiation of a solution of the spiroacetal (23), iodobenzene diacetate, and iodine in cyclohexane at room temperature.

On the fluorescence quenching of pyrene by iodine

Fluorescence quenching of the excited state of pyrene by iodine in cyclohexane and methano is studied. Quenching rate constants for deactivation of K Q = 2.20±0.02 × 10 10 mol −1 s −1 dm 3 and K Q = 1.63±0.06 × 10 10 mol −1 s −1 dm 3 are measured for pyrene in cyclohexane and methanol, respectively. These values are discussed in terms of a diffusion-controlled mechanism. Exchange quenching process in cyclohexane, giving an “effective” encounter distance of about 13.3 Å is proposed.

Study of Molecular Complexes by Refractometry

Abstract The refractive index measurement technique is used to investigate molecular complex formation in liquid solutions and the association constants are determined directly. The association constants at 25 °C and heats of complexation for naphthalene–phenol, benzene–tetracyanoethylene, p-xylene–tetracyanoethylene, hexamethylbenzene–tetracyanoethylene, and triethylamine–iodine in cyclohexane are 8.2, 2.2, 8.6, 231, and 4620 dm3 mol−1 and 19.25, 11.30, 18.00, 32.21, and 51.46 kJ/mol, respectively. These values agree well with the literature data obtained by spectroscopic methods.

Synthetic studies on terpenoids. Part 7. Synthetic studies leading to the total synthesis of eudesmane sesquiterpenes

The synthesis of two naturally occurring sesquiterpenes, (±)-junenol (1) and (±)-acolamone (2), from the bicyclic ketone (3) is described. The introduction of an isopropyl chain at C-7 of the bicyclic ketone was attempted by three different procedures and yielded ketone (5) which, on reduction with sodium and ethanol, gave the alcohol (12). This, on oxidation with lead tetra-acetate and iodine in cyclohexane, yielded the cyclic ether (13) and regenerated the ketone (5). Oxidation of compound (13) with chromium(VI) oxide in acetic acid afforded the keto-acid (15) which, on oxidative decarboxylation with lead tetra-acetate, furnished acolamone which was reduced with sodium borohydride in ethanol to (±)-junenol.

Kinetics and mechanism of the reaction of iodine with bis(N, N-di-n-butyldithiocarbamato)zinc(II)

The reaction of bis(N,N-di-n-butyldithiocarbamato)zinc(II), Zn(n-Bu 2dtc) 2, with iodine in cyclohexane was studied employing a stopped-flow technique under pseudo-first-order conditions with excess Zn(n-Bu 2dtc) 2. The rate data indicate that the reaction proceeds via the formation of a charge-transfer complex Zn(n-Bu 2dtc) 2·I 2, and obeys second-order kinetics for the concentration of Zn(n-Bu 2dtc) 2. These results are interpreted by a mechanism that involves a bimolecular reaction between the charge-transfer complex and the parent Zn(n-Bu 2dtc) 2 compound. The thermodynamic parameters for the formation of the charge-transfer complex were determined (K = 1.47 X 10 2 M −1, ΔH° = −30.2 kJ mol −1, ΔS° = −59.4 J mol −1 deg −1 at 25 °C) and the transition state in the bimolecular pathway is proposed.

The Kinetics and Mechanisms of Reaction of Iodine with Bis(N,N-diethyldithiocarbamato)dimethyltin(IV) and Related Compounds

Abstract The reactions of Me2SnL(S2CNEt2) (L=S2CNEt2 (1) and I (2)) with iodine in cyclohexane were investigated employing a stopped-flow technique. The kinetic data indicate that the reaction in the presence of a large excess of 1 or 2 proceeds via a charge-transfer complex of Me2SnL(S2CNEt2)·I2, which decomposes in the ratedetermining step to yield Me2SnI(L) and unstable I(S2CNEt2). This unstable intermediate reacts with the excess 1 or 2 to afford Me2SnI(L) and tetraethylthiuramdisulfide (3). The reaction of 1 with a large excess of I2was also kinetically studied to reveal the formation of the 1 : 2 complex, Me2Sn(S2CNEt2)2·2I2, as an intermediate; this intermediate then undergoes a simultaneous degradation to afford Me2SnI2 and 3. The transition state in the reaction is discussed.

Alpha-Particle Radiolysis of the Cyclohexane-Sulfur System

a comparison of the effect of Co0? y-radiolysis and Po210 a-radiolysis of solutions of iodine in cyclohexane has shown the existence of a marked effect of LET; with the aid of Fricke's (4) one-radical model, with which the experimental data were quite consistent, it was deduced that the radius of the a-particle track lay between 10 and 20 A, in good agreement with the values usually assumed for aqueous systems. It is suggested that elemental sulfur is an efficient protecting agent when present in colloidal aqueous suspensions (5, 6), and it has been shown (7) that it has a significant effect on the y-radiolysis of cyclohexane. The effect in the latter case is less than in the aqueous system, despite the fact that the sulfur is present in true solution. It is probable that the large effect in the aqueous system is due to the presence of thionic acids formed during the preparation of the colloidal sulfur; furthermore, specifically colloidal (rather than radiolytic) effects cannot be ruled out.

Charge-transfer complexes in the scavenging by iodine of radicals formed on pulse radiolysis of cyclo hexane

Pulse radiolysis of solutions of iodine in cyclo hexane resulted in the formation of a transient absorption with wavelength maximum at 3300 Å. This transient spectrum was assigned to the C 6 H 12 ... I' charge-transfer complex. The spectrum and extinction coefficients of the complex over the wavelength range 2500 to 6500 Å were obtained, the coefficient at 3300 Å being 2025 1. mole -1 cm -1 . Hydrogen iodide in cyclo hexane gave rise to the same transient absorption. Pulse radiolysis of cyclo hexane and cyclo hexyl iodide alone gave rise to different transient spectra attributed to the cyclo hexyl radical, absorbing in the ultraviolet, extinction coefficient 3401. mole -1 cm -1 at 2550 Å and the C 6 H 11 .. .I* charge-transfer complex, absorption maximum 3900 A, extinction coefficient ~ 10 3 to 10 4 1. mole -1 cm -1 , respectively. During the course of the investigations rate constants were obtained for the following reactions: C 6 H 11 + I 2 C 6 H 11 I + I', k II = 7 x 10 9 1. mole -1 s -1 , 2C 6 H 12 ...I' -> 2C 6 H 12 + I 2 , k II = 1.06 x 10 10 1. mole -1 s -1 , or 21' -> I 2 , a C 6 H 10 + C 6 H 12 2C 6 H 11 k 11a + k 11b =2.5 x 10 9 1. mole -1 s -1 bC 12 H 22 Dilute solutions of iodine (10 -4 M) in cyclo hexane yielded experimental evidence for neutral radical intermediates only. There were, however, indications that ionic radical intermediates occur in more concentrated solutions ( > 10 -3 M). :