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The nucleophilicities of the oxidants hydroperoxide, hypochlorite, hypobromite, bromite, and peroxymonosulfate were determined by following the kinetics of their reactions with a series of benzhydrylium ions of known electrophilicity (E) in alkaline, aqueous solutions at 20 °C. The reactivities of the oxidants correlate only weakly with their basicities. Analyzing the rate constants by using the relationship log k2 = sN(N + E) gave the parameters N (and sN), which were applied to predict the rates of Weitz-Scheffer epoxidations. [ABSTRACT FROM AUTHOR]

Micellisation of two binary mixtures, sodium decyl sulfate (NaDS)-sodium deoxycholate (NaDC) and sodium decyl sulfate (NaDS)-sodium hyodeoxychlolate (NaHDC), is examined, in consideration with the different molar fractions of the monomers (x = 0.1-0.9). In bile acids, the OH groups attached to steroid skeletons are spatially ecraned, while the sulfate group of NaDS is not ecraned. Thus, NaDC and NaHDC in relation to NaDS have different coordination numbers in the micelle pseudophase. On the basis of stereochemical analysis, rational design shows that the excess Gibbs energy (GE) of formation of the binary mixed micelle throughout the whole composition range can be described with a two-parameter Margules function, while the GE function from the regular solution theories is applicable only in the narrow interval of the bile salts molar fractions (x = 0.5-0.8). Coefficient of activity (hypothetical) of the infinitely diluted mixed micelle of NaDS in the presence of NaDC shows significant thermodynamic stabilization of decyl sulfate ions in comparison with the infinitely diluted hypothetical mixed micelle with NaHDC. This stabilization of decyl sulfate ions is probably due to the cooperative binding of NaDS by parallel OH groups of NaDC. [ABSTRACT FROM AUTHOR]

High-throughput screening (HTS) methods have become decisive for the discovery and development of new biocatalysts and their application in numerous fields. Sulfatases, a broad class of biocatalysts that hydrolyze sulfate esters, are involved in diverse relevant cellular functions (e.g., signaling and hormonal regulation) and are therefore gaining importance, particularly in the medical field. Additionally, various technical applications have been recently devised. One of the major challenges in the field of enzyme development is the sensitive and high-throughput detection of the actual product of the biocatalyst of interest without the need for chromophore analogues. Addressing this issue, a colorimetric assay for sulfatases was developed and validated for detecting sulfate through a two-step enzymatic cascade, with a linear detection range of 3.3 (limit of detection) up to 250 μM. The procedure is compatible with relevant compounds employed in sulfatase reactions, including cosolvents, cations, and buffers. The assay was optimized and performed as part of a 96-well screening workflow that included bacterial growth, heterologous sulfatase expression, cell lysis, sulfate ester hydrolysis, inactivation of cell lysate, and colorimetric sulfate determination. With this procedure, the activity of an aryl and an alkyl sulfatase could be confirmed and validated. Overall, this assay provides a simple and fast alternative for screening and engineering sulfatases from DNA libraries (e.g., using metagenomics) with medical or synthetic relevance. [ABSTRACT FROM AUTHOR]

A unique asymmetric total synthesis of the unnatural enantiomer of pregnanolone, as well as a study of its biological activity at the NMDA receptor, is reported. The asymmetry is introduced by a highly atom-economic organocatalytic Robinson annulation. A new method for the construction of the cyclopentane D-ring consisting of CuI-catalyzed conjugate addition and oxygenation followed by thermal cyclization employing the persistent radical effect was developed. ent-Pregnanolone sulfate is surprisingly only 2.6-fold less active than the natural neurosteroid. [ABSTRACT FROM AUTHOR]

Tubelike Co3O4 was successfully prepared by a facile electrospinning route combined with a subsequent calcining treatment. The as-prepared tubelike Co3O4 was exploited as peroxidase mimics and to activate peroxymonosulfate (PMS) to produce sulfate radicals. The tubelike Co3O4 exhibited intrinsic peroxidase-like activity and high ability of activating PMS to degrade 2,4-dichlorophenol compared with the powders for the high specific surface area and surface Co2+ and adsorbed oxygen contents. Furthermore, the electronic properties of Co3O4 and the catalytic mechanism on H2O2 and PMS were investigated by electron spin resonance test and density functional theory calculation. This study details the insights into Co3O4 nanomaterials for activation of peroxides and application in sustainable remediation. [ABSTRACT FROM AUTHOR]

In this work, a facile synthesis of ceria and sulfated zirconia (SZ) incorporated SBA-15 catalyst was conducted. The supported SZ reveals promising Brønsted/Lewis acid and relatively low base strength, and the base strength of the catalyst is significantly enhanced by introducing highly dispersed ceria into the network of SZ incorporated SBA-15. Systematic study of catalyst activities were carried out in iPrOH/DMSO solvent conversion of glucose to 5-hydroxymethylfurfural (HMF). It is found that the isomerization process of glucose to fructose was promoted by coexisting base and Lewis acid sites, and the dehydration reaction of reactively formed fructose to HMF was directed by Brønsted acid sites. Up to 66.5% HMF yield and 70.8% selectivity can be obtained in a 90 vol % iPrOH-mediated DMSO solvent. Through the reaction system developed in this paper, use of a large amount of environmentally hazardous solvent can be avoided, and a new method of large-scale economically viable processes for biomass conservation is provided. [ABSTRACT FROM AUTHOR]

(-)-6'-β-Fluoro-aristeromycin (2), a potent inhibitor of S-adenosylhomocysteine (AdoHcy) hydrolase, has been synthesized via stereoselective electrophilic fluorination followed by a purine base build-up approach. Interestingly, purine base condensation using a cyclic sulfate resulted in a synthesis of (+)-5'-β-fluoro-isoaristeromycin (2a). Computational analysis indicates that the fluorine atom controlled the regioselectivity of the purine base substitution. [ABSTRACT FROM AUTHOR]

The presence of impurities in solution during crystallization can influence the crystallization kinetics of the desired product. Consequently, this affects the product quality parameters such as the crystal size distribution (CSD), purity, and morphology. This paper focuses on the application of eutectic freeze crystallization (EFC) to the purification of petrochemical brine rich in sulfate salts. The effect of phenol on the CSD, nucleation and growth rates, purity, and morphology of ice and sodium sulfate decahydrate crystals was evaluated using a batch EFC setup. Nucleation and growth rates were obtained from in situ image acquisition and analyses. In the presence of 0.2 wt % phenol, larger crystals were obtained for both ice and sodium sulfate decahydrate due to increased growth rates and reduced nucleation rates. The crystal habit of both ice and salt was not modified by the phenol impurity. Ice crystals presented elongated disk shapes and dendritic habit, and crystal sizes up to 1000 μm were obtained. Salt particles exhibited prismatic shape and monoclinic class as expected for Na2SO4·10H2O. Ice purity of about 97% was obtained before washing in the presence of phenol. Three washing cycles increased the ice purity to 100% implying that impurities were physically adhered on the ice surfaces and not incorporated into the crystal lattice, which deserves additional studies to verify this proposal. X-ray diffraction (XRD) analyses of salt crystals confirmed that Na2SO4·10H2O with the structure of thenardite was crystallized. Any other phase was detected. [ABSTRACT FROM AUTHOR]

Adding ionic species can critically affect the structure of weak polyelectrolyte (PE) chains, whose charge density in aqueous solution can be greatly regulated by bathing solution conditions such as pH and added ions. Distinct from simple ions that can be treated as point charges, multivalent macroions of finite size, including many charged nanoparticles and biopolymers, could show strong electrostatic coupling with PEs and effectively modify the conformation and assembly of PEs in aqueous solution. In this work, we have compared the effects of hydrophilic multivalent macroion of finite size and simple divalent ion on the conformational transition of a model weak polybase, poly(2-vinylpyridine) (P2VP), in dilute aqueous solution. By using fluorescence correlation spectroscopy combined with photon counting histogram analysis, we have examined the swollen-to-collapsed conformational transition and local electric potential of a P2VP chain in ionic aqueous solution at a single-molecule level. Adding inorganic polytungstate ([W12]) macroion bearing eight negative charges per [W12] of ~0.8 nm in diameter at increased concentration from 10-9 to 10-5 mM can lead to a shift of the critical conformational transition pH, pHcr, of P2VP to lower pH values, in an opposite trend to the previously reported effect of adding simple monovalent anion. Conversely, adding simple divalent sulfate anion can lead to a nonmonotonic change of pHcr when increasing its concentration from 0.03 to 15 mM. Additionally, at pH < pHcr where P2VP is highly protonated and adopts a swollen conformation, a monotonic decrease of P2VP size is observed with increased sulfate ionic concentration, exhibiting the typical ionic screening effect. In contrast, the size of the P2VP chain shows little change with increasing [W12] concentration before the precipitation of P2VP from water. To investigate the distinct effects of multivalent ion and macroion on the conformational transition of P2VP in aqueous solution, we have also measured the local proton concentration in the vicinity to a P2VP chain by an attached pH-sensitive fluorescence probe. In both cases, we have observed the monotonic reduction of the local electric potential of a swollen P2VP chain with increased ionic concentration, despite the increased protonation degree of P2VP. The results suggest that counterion condensation of multivalent ion and macroion can modify the effective net charge density of P2VP chains in dilute aqueous solution. However, possibly due to its high multivalency and finite size, multivalent [W12] macroion is much more effective in modifying the local electric environment and structure of P2VP chains at 3-7 orders of magnitude lower concentrations than simple sulfate counterion. [ABSTRACT FROM AUTHOR]

Adsorption isotherm-based statistical thermodynamic models can be used to determine solute concentration and solute and solvent activities in aqueous solutions. Recently, the number of adjustable parameters in the isotherm model of Dutcher et al. J. Phys. Chem. A/C 2011, 2012, 2013 were reduced for neutral solutes as well as symmetric 1:1 electrolytes by using a Coulombic model to describe the solute-solvent energy interactions (Ohm et al. J. Phys. Chem. A 2015, Nandy et al. J. Phys. Chem. A 2016). Here, the Coulombic treatment for symmetric electrolytes is extended to establish improved isotherm model equations for asymmetric 1-2 and 1-3 electrolyte systems. The Coulombic model developed here results in prediction of activities and other thermodynamic properties in multicomponent systems containing ions of arbitrary charge. The model is found to accurately calculate the osmotic coefficient over the entire solute concentration range with two model parameters, related to intermolecular solute-solute and solute-solvent spacing. The inorganic salts and acids treated here are generally considered to be fully dissociated. However, there are certain weak acids that do not dissociate completely, such as the bisulfate ion. In this work, partial dissociation of the bisulfate ion from sulfuric acid is treated as a mixture, with an additional model parameter that accounts for the dissociation ratio of the dissociated ions to nondissociated ions. [ABSTRACT FROM AUTHOR]

Schwertmannite is a ferric oxyhydroxysulfate mineral, which is common in acid sulfate systems. Such systems contain varying concentrations of phosphate (PO43-)an essential nutrient whose availability may be coupled to schwertmannite formation and fate. This study examines the effect of phosphate on schwertmannite stability under reducing conditions. Phosphate was added at 0, 80, 400, and 800 μmoles g-1 (i.e., zero, low, medium, and high loading) to schwertmannite suspensions which were inoculated with wetland sediment and suspended in N2-purged artificial groundwater. pH remained between 2.7 and 4.3 over the 41 day experiment duration. Fe(II) accumulated in solution due to dissimilatory Fe(III)-reduction, which was most pronounced at intermediate PO43- loadings (i.e., in the low PO43- treatment). Partial transformation of schwertmannite to goethite occurred in the zero and low PO43- treatments, with negligible transformation in higher PO43- treatments. Overall, the results suggest that intermediate PO43- loadings provide conditions which facilitate optimal reductive dissolution of schwertmannite. At zero PO43- loading, reductive dissolution appears to be constrained by the rapid transformation of schwertmannite to goethite, which thereby decreases the bioavailability of solid-phase Fe(III). Conversely, at high loadings, PO43- appears to stabilize the schwertmannite surface against dissolution; probably via the formation of strong surface complexes. [ABSTRACT FROM AUTHOR]

Polarized transmitted light observation was used to examine the Krafft point temperature of cesium dodecylsulfate (CsDS) in water over a wide range of concentrations. CsDS shows an elevated Krafft temperature compared to that of sodium dodecyl sulfate (SDS). Unlike SDS, the CsDS solubility temperature remains virtually constant at high concentration. Also, the stable birefringent liquid crystal appears at a much lower concentration for CsDS than for SDS, and the concentration window of its coexistence with isotropic micellar solution is broader. [ABSTRACT FROM AUTHOR]

Isoprene epoxydiol (IEPOX), glyoxal, and methylglyoxal are ubiquitous water-soluble organic gases (WSOGs) that partition to aerosol liquid water (ALW) and clouds to form aqueous secondary organic aerosol (aqSOA). Recent laboratory-derived Setschenow (or salting) coefficients suggest glyoxal's potential to form aqSOA is enhanced by high aerosol salt molality, or "salting-in". In the southeastern U.S., aqSOA is responsible for a significant fraction of ambient organic aerosol, and correlates with sulfate mass. However, the mechanistic explanation for this correlation remains elusive, and an assessment of the importance of different WSOGs to aqSOA is currently missing. We employ EPA's CMAQ model to the continental U.S. during the Southern Oxidant and Aerosol Study (SOAS) to compare the potential of glyoxal, methylglyoxal, and IEPOX to partition to ALW, as the initial step toward aqSOA formation. Among these three studied compounds, IEPOX is a dominant contributor, ~72% on average in the continental U.S., to potential aqSOA mass due to Henry's Law constants and molecular weights. Glyoxal contributes significantly, and application of the Setschenow coefficient leads to a greater than 3-fold model domain average increase in glyoxal's aqSOA mass potential. Methylglyoxal is predicted to be a minor contributor. Acid or ammonium - catalyzed ring-opening IEPOX chemistry as well as sulfate-driven ALW and the associated molality may explain positive correlations between SOA and sulfate during SOAS and illustrate ways in which anthropogenic sulfate could regulate biogenic aqSOA formation, ways not presently included in atmospheric models but relevant to development of effective control strategies. [ABSTRACT FROM AUTHOR]

IR spectroscopy of gas-phase ions is proposed to resolve positional isomers of sulfated carbohydrates. Mass spectrometric fingerprints and gas-phase vibrational spectra in the near and mid-IR regions were obtained for sulfated monosaccharides, yielding unambiguous signatures of sulfated isomers. We report the first systematic exploration of the biologically relevant but notoriously challenging deprotonated state in the near IR region. Remarkably, anions displayed very atypical vibrational profiles, which challenge the well-established DFT (Density Functionnal Theory) modeling. The proposed approach was used to elucidate the sulfate patterns in glycosaminoglycans, a ubiquitous class of mammalian carbohydrates, which is regarded as a major challenge in carbohydrate structural analysis. Isomeric glycosaminoglycan disaccharides from heparin and chondroitin sources were resolved, highlighting the potential of infrared multiple photon dissociation spectroscopy as a novel structural tool for carbohydrates. [ABSTRACT FROM AUTHOR]

Advanced oxidation processes (AOPs), such as hydroxyl radical (HO•)- and sulfate radical (SO4•-)-mediated oxidation, are alternatives for the attenuation of pharmaceuticals and personal care products (PPCPs) in wastewater effluents. However, the kinetics of these reactions needs to be investigated. In this study, kinetic models for 15 PPCPs were built to predict the degradation of PPCPs in both HO•- and SO4•--mediated oxidation. In the UV/H2O2 process, a simplified kinetic model involving only steady state concentrations of HO• and its biomolecular reaction rate constants is suitable for predicting the removal of PPCPs, indicating the dominant role of HO• in the removal of PPCPs. In the UV/K2S2O8 process, the calculated steady state concentrations of CO3•- and bromine radicals (Br•, Br2•- and BrCl•-) were 600-fold and 1-. orders of magnitude higher than the concentrations of SO4•-, respectively. The kinetic model, involving both SO4•- and CO3•- as reactive species, was more accurate for predicting the removal of the 9 PPCPs, except for salbutamol and nitroimidazoles. The steric and ionic effects of organic matter toward SO4•- could lead to overestimations of the removal efficiencies of the SO4•--mediated oxidation of nitroimidazoles in wastewater effluents. [ABSTRACT FROM AUTHOR]

The β-Li2TiO3 crystal is an important material in several energy-related applications, and the control of its morphology and exposed facets is an important issue. Herein, we comprehensively studied the flux growth of β-Li2TiO3 crystals under different conditions and demonstrated the efficient anisotropic growth of {001}-faceted β-Li2TiO3 single crystals from the Na2SO4 flux. By examining the effects of the cation and anion in the alkali metal salt-based flux, we found that Na2SO4 flux is best for growing large, faceted β-Li2TiO3 crystals. In this flux at 1000 °C, the optimal solute concentration is 20 mol % for growing large (∼15.0 μm in lateral size), platy, and faceted β-Li2TiO3 crystals. Observations from varying the holding time and cooling rate indicated that these crystals were anisotropically grown. Transmission electron microscopy images with clear electron diffraction spots revealed that the flux-grown platy β-Li2TiO3 crystals are single crystalline solids with the {001} plane being the dominant facet. This anisotropic crystal growth could be attributed to the concerted effects of the preferential attachment of sodium cations on the {001} faces, and efficient dissolution of β-Li2TiO3 crystals as well as the solvation of the resulting O2- ions in the sulfate anion-based flux. [ABSTRACT FROM AUTHOR]

2-Amino-9H-pyrido[2,3-b]indole (AαC) is the most abundant carcinogenic heterocyclic aromatic amine (HAA) formed in mainstream tobacco smoke. AαC is a liver carcinogen in rodents, but its carcinogenic potential in humans is not known. To obtain a better understanding of the genotoxicity of AαC in humans, we have investigated its metabolism and its ability to form DNA adducts in human hepatocytes. Primary human hepatocytes were treated with AαC at doses ranging from 0.1-50 μM, and the metabolites were characterized by ultra-performance LC/ion trap multistage mass spectrometry (UPLC/MSn). Six major metabolites were identified: a ring-oxidized doubly conjugated metabolite, N2-acetyl-2-amino-9H-pyrido[2,3-b]indole-6-yl-oxo-(β-d-glucuronic acid) (N2-acetyl-AαC-6-O-Gluc); two ring-oxidized glucuronide (Gluc) conjugates: 2-amino-9H-pyrido[2,3-b]indol-3-yl-oxo-(β-d-glucuronic acid) (AαC-3-O-Gluc) and 2-amino-9H-pyrido[2,3-b]indol-6-yl-oxo-(β-d-glucuronic acid) (AαC-6-O-Gluc); two sulfate conjugates, 2-amino-9H-pyrido[2,3-b]indol-3-yl sulfate (AαC-3-O-SO3H) and 2-amino-9H-pyrido[2,3-b]indol-6-yl sulfate (AαC-6-O-SO3H); and the Gluc conjugate, N2-(β-d-glucosidurony1)-2-amino-9H-pyrido[2,3-b]indole (AαC-N2-Gluc). In addition, four minor metabolites were identified: N2-acetyl-9H-pyrido[2,3-b]indol-3-yl sulfate (N2-acetyl-AαC-3-O-SO3H), N2-acetyl-9H-pyrido[2,3-b]indol-6-yl sulfate (N2-acetyl-AαC-6-O-SO3H), N2-acetyl-2-amino-9H-pyrido[2,3-b]indol-3-yl-oxo-(β-d-glucuronic acid) (N2-acetyl-AαC-3-O-Gluc), and O-(β-d-glucosidurony1)-2-hydroxyamino-9H-pyrido[2,3-b]indole (AαC-HN2-O-Gluc). The latter metabolite, AαC-HN2-O-Gluc is a reactive intermediate that binds to DNA to form the covalent adduct N-(2'-deoxyguanosin-8-yl)-2-amino-9H-pyrido[2,3-b]indole (dG-C8-AαC). Preincubation of hepatocytes with furafylline, a selective mechanism-based inhibitor of P450 1A2, resulted in a strong decrease in the formation of AαC-HN2-O-Gluc and a concomitant decrease in DNA adduct formation. Our findings describe the major pathways of metabolism of AαC in primary human hepatocytes and reveal the importance of N-acetylation and glucuronidation in metabolism of AαC. P450 1A2 is a major isoform involved in the bioactivation of AαC to form the reactive AαC-HN2-O-Gluc conjugate and AαC-DNA adducts. [ABSTRACT FROM AUTHOR]

There is interest in the controlled aggregation of gold nanorods (GNRs) for the production of extended nanoassemblies. Prior studies have relied upon chemical modification of the GNR surface to achieve a desired final aggregate structure. Herein we illustrate that control of electrolyte composition can facilitate end-to-end assembly of cetyltrimethylammonium-bromide-coated (CTAB) GNRs. By adjusting either the sulfate anion concentration or the exposure time it is possible to connect GNRs in chain-like assemblies. In contrast, end-to-end assembly was not observed in control experiments using monovalent chloride salts. We attribute the end-to-end assembly to the localized association of sulfate with exposed quaternary ammonium head groups of CTAB at the nanorod tip. To quantify the assembly kinetics, visible-near-infrared extinction spectra were collected over a predetermined time period, and the colloidal behavior of the GNR suspensions was interpreted using plasmon band analysis. Transmission electron microscopy and atomic force microscopy results support the conclusions reached via plasmon band analysis, and the colloidal behavior is consistent with Derjaguin-Landau-Verwey-Overbeek theory. [ABSTRACT FROM AUTHOR]

Phase equilibria in quinary Na, K//Cl, SO4, B4O7-H2O system at 25 °C were investigated by means of translation method. Five invariant points, 16 monovaraint curves, and 18 divariant fields have been determined in the system on quinary composition. A comprehensive phase equilibria diagram for the system was constructed on the basis of obtained data. The diagram was fragmented into divariant cocrystallization fields and trivariant volumes of two different solid phases and individual equilibrium solid phases, respectively. The comparison of obtained results with available experimental data was deliberated. [ABSTRACT FROM AUTHOR]

We report a systematic study of the sulfate-mediated polyol synthesis of Pd decahedra in an attempt to maximize both the conversion and morphology yields. Quantitative analyses of the as-obtained products reveal the presence of nanocrystal populations with distinct ranges of size. Samples collected in the early stage of a standard synthesis indicate that this size distribution is likely caused by the coalescence of the initially formed decahedral nuclei. Kinetic measurements clearly show the impact of the sulfate additive on the initial reduction rate and thus the yield of decahedral nuclei. Based on the mechanistic understanding developed over the course of this work, we were able to significantly improve the conversion and morphology yields of the Pd decahedra synthesis by introducing a second reducing agent after the completion of homogeneous nucleation. The improvement in yields for the Pd decahedra synthesis will increase the availability of these nanocrystals as catalytic materials and as a unique platform for the development of more complex nanostructures. [ABSTRACT FROM AUTHOR]

The water activities of the systems MSO4 + H2O (M = Mn, Co, Ni, Cu, Zn) are essential data needed for simulating the hydrometallurgical process of these metals. In our previous work (J. Chem. Eng. Data, 2014, 59, 97-102), the experimental data of water activity for these binary systems have been reported at 323.15 K. As one part of this series of work, the experimental data of water activity for these systems are reported at 373.15 K. The reliability of the apparatus at 373.15 K was verified by measuring and comparing the water activities of the two reference systems, CaCl2 + H2O and LiCl + H2O. The results showed that the maximal relative deviation of the water activities between the reference systems was 0.054%. The water activities for the concerned five systems were found to be approximately the same at a certain salt molality below 1 M. The water activities of these systems decrease at a certain salt molality more than 1 M in the following sequence: aMnSO4 < aCuSO4(∼aZnSO4) < aCoSO4(∼aNiSO4). Furthermore, the experiment data obtained in this work were compared with the model values reported in the literature. [ABSTRACT FROM AUTHOR]

In the present study, quasi-static reactor and atmospheric simulation chamber experiments were performed to investigate the formation of α-pinene-derived organosulfates. Organosulfates (R-OSO3H) were examined for the reactions between acidified ammonium sulfate particles exposed to an individual gaseous volatile organic compound, such as α-pinene and oxidized products (α-pinene oxide, isopinocampheol, pinanediol and myrtenal). Molecular structures were elucidated by liquid chromatography interfaced to high-resolution quadrupole time-of-flight mass spectrometry equipped with electrospray ionization (LC/ESI-HR-QTOFMS). New organosulfate products were detected and identified for the first time in the present study. Reaction with α-pinene oxide was found to be a favored pathway for organosulfate formation (C10H18O5S) and to yield organosulfate dimers (C20H34O6S and C20H34O9S2) and trimers (C30H50O10S2) under dry conditions (RH > 1%) and high particle acidity and precursor concentrations (1 ppm). The role of relative humidity on organosulfate formation yields and product distribution was specifically examined. Organosulfate concentrations were found to decrease with increasing relative humidity. Mechanistic pathways for organosulfate formation from the reactions between α-pinene, α-pinene oxide, isopinocampheol, or pinanediol with acidified ammonium sulfate particles are proposed. [ABSTRACT FROM AUTHOR]

This study demonstrates the capability of noble metal nanoparticles immobilized on Al2O3 or TiO2 support to effectively activate peroxymonosulfate (PMS) and degrade select organic compounds in water. The noble metals outperformed a benchmark PMS activator such as Co2+ (water-soluble) for PMS activation and organic compound degradation at acidic pH and showed the comparable activation capacity at neutral pH. The efficiency was found to depend on the type of noble metal (following the order of Pd > Pt ≈ Au ≫ Ag), the amount of noble metal deposited onto the support, solution pH, and the type of target organic substrate. In contrast to common PMS-activated oxidation processes that involve sulfate radical as a main oxidant, the organic compound degradation kinetics were not affected by sulfate radical scavengers and exhibited substrate dependency that resembled the PMS activated by carbon nanotubes. The results presented herein suggest that noble metals can mediate electron transfer from organic compounds to PMS to achieve persulfate-driven oxidation, rather than through reductive conversion of PMS to reactive sulfate radical. [ABSTRACT FROM AUTHOR]

Atmospheric oxidation of isoprene under low-NOx conditions leads to the formation of isoprene hydroxyhydroperoxides (ISOPOOH). Subsequent oxidation of ISOPOOH largely produces isoprene epoxydiols (IEPOX), which are known secondary organic aerosol (SOA) precursors. Although SOA from IEPOX has been previously examined, systematic studies of SOA characterization through a non-IEPOX route from 1,2-ISOPOOH oxidation are lacking. In the present work, SOA formation from the oxidation of authentic 1,2-ISOPOOH under low-NOx conditions was systematically examined with varying aerosol compositions and relative humidity. High yields of highly oxidized compounds, including multifunctional organosulfates (OSs) and hydroperoxides, were chemically characterized in both laboratory-generated SOA and fine aerosol samples collected from the southeastern U.S. IEPOX-derived SOA constituents were observed in all experiments, but their concentrations were only enhanced in the presence of acidified sulfate aerosol, consistent with prior work. High-resolution aerosol mass spectrometry (HR-AMS) reveals that 1,2-ISOPOOH-derived SOA formed through non-IEPOX routes exhibits a notable mass spectrum with a characteristic fragment ion at m/z 91. This laboratory-generated mass spectrum is strongly correlated with a factor recently resolved by positive matrix factorization (PMF) of aerosol mass spectrometer data collected in areas dominated by isoprene emissions, suggesting that the non-IEPOX pathway could contribute to ambient SOA measured in the Southeastern United States. [ABSTRACT FROM AUTHOR]

Indolocarbazole-pyridine hybrid foldamers are strongly fluorescent in an extended random conformation, but the fluorescence is completely quenched upon folding to a helical conformation due to the compact stacking between aryl planes in the backbone. Anion binding disturbs the helical conformation, thus regenerating the fluorescence of the foldamers. This unique property has been utilized to develop a fluorescence turn-on probe for anions such as sulfate and fluoride. [ABSTRACT FROM AUTHOR]

Phase formation in the aqueous system of uranyl nitrate, potassium hydroxide, and variable amounts of sulfuric and selenic acids has been investigated. Four different types of crystalline phases with variable S and Se contents were isolated and characterized using single-crystal X-ray diffraction (XRD) and IR spectroscopy. Topological analysis and information-based complexity calculations demonstrated the following: (a) the absence of a continuous solid solution in the system, (b) the absence of isotypic sulfate and selenate phases, and (c) the discovery of two layered topologies unprecedented among inorganic oxysalts. [ABSTRACT FROM AUTHOR]

Sulfate adsorption on mineral surfaces is an important environmental chemical process, but the structures and respective contribution of different adsorption complexes under various environmental conditions are unclear. By combining sulfur K-edge XANES and EXAFS spectroscopy, quantum chemical calculations, and surface complexation modeling (SCM), we have shown that sulfate forms both outer-sphere complexes and bidentate-binuclear inner-sphere complexes on ferrihydrite surfaces. The relative fractions of the complexes vary with pH, ionic strength (I), and sample hydration degree (wet versus air-dried), but their structures remained the same. The inner-sphere complex adsorption loading decreases with increasing pH while remaining unchanged with I. At both I = 0.02 and 0.1 M, the outer-sphere complex loading reaches maximum at pH ~5 and then decreases with pH, whereas it monotonically decreases with pH at I = 0.5 M. These observations result from a combination of the ionic-strength effect, the pH dependence of anion adsorption, and the competition between inner- and outer-sphere complexation. Air-drying drastically converts the outer-sphere complexes to the inner-sphere complexes. The respective contributions to the overall adsorption loading of the two complexes were directly modeled with the extended triple layer SCM by implementing the bidentate-binuclear inner-sphere complexation identified in the present study. These findings improve our understanding of sulfate adsorption and its effects on other environmental chemical processes and have important implications for generalizing the adsorption behavior of anions forming both inner- and outer-sphere complexes on mineral surfaces. [ABSTRACT FROM AUTHOR]

Al3+ ions were introduced into silica framework at 318 K in order to make active Al sites for SO42- by the addition of aqueous sodium silicate solution to aqueous sulfuric acid solution of Al2(SO4)3. The 27Al and 29Si NMR spectra of aluminosilicates were measured at 278 K with reaction time. 29Si NMR spectra were analyzed by the multivariate curve resolution. The addition of Al3+ ions to aqueous silicate solution promoted gel formation. Small amounts of Al3+ ions were incorporated as a four-coordinated complex at early stage of polymerization reaction of silicates and during subsequent reaction six-coordinated Al complex increased, suggesting reversible conversion between 4- and 6-coordinated complexes. SO42- ions interact with positive surfaces of aluminosilicates and are specifically adsorbed on the surface sites of 6-coordinated Al3+ species, which may be stabilized on silicate surfaces as [Al(H2O)5SO4]+. [ABSTRACT FROM AUTHOR]

In recent years in a few Chinese megacities, fog events lasting one to a few days have been frequently associated with high levels of aerosol loading characterized by high sulfate (as high as 30 μg m-3), therefore termed as haze-fog events. The concomitant pollution characteristics include high gas-phase mixing ratios of SO2 (up to 71 ppbv) and NO2 (up to 69 ppbv), high aqueous phase pH (5-6), and smaller fog droplets (as low as 2 μm), resulting from intense emissions from fossil fuel combustion and construction activities supplying abundant Ca2+. In this work, we use an observation-based model for secondary inorganic aerosols (OBM-SIA) to simulate sulfate formation pathways under conditions of haze-fog events encountered in Chinese megacities. The OBM analysis has identified, at a typical haze-fogwater pH of 5.6, the most important pathway to be oxidation of S(IV) by dissolved NO2, followed by the heterogeneous reaction of SO2 on the aerosol surface. The aqueous phase oxidation of S(IV) by H2O2 is a very minor formation pathway as a result of the high NOx conditions suppressing H2O2 formation. The model results indicate that the unique cocktail of high fogwater pH, high concentrations of NO2, SO2, and PM, and small fog droplets are capable of greatly enhancing sulfate formation. Such haze-fog conditions could lead to rapid sulfate production at night and subsequently high PM2.5 in the morning when the fog evaporates. Sulfate formation is simulated to be highly sensitive to fogwater pH, PM, and precursor gases NO2 and SO2. Such insights on major contributing factors imply that reduction of road dust and NOx emissions could lessen PM2.5 loadings in Chinese megacities during fog events. [ABSTRACT FROM AUTHOR]

Spherulitic assemblies have applications as carriers for drug delivery and as targeting vectors. Presently, the driving force behind the formation of spherulites comprising small drug molecules is not fully understood. Herein, the impact of different substrate types on spherulitic crystallization of salbutamol sulfate (SS) was investigated. Freshly cleaved mica, silicon (111) wafer (SiW), uncoated borosilicate glass (UG), silane coated glass (CG), and stainless steel (MS) were used as substrates. It was demonstrated that the spherulite growth can be controlled via the substrate selection. Spherulite formation was inhibited on hydrophilic substrates, such as mica, possibly due to stronger intermolecular interactions between SS and the substrate than SS-SS interactions. Contact angle measurements established that mica possessed the lowest contact angle (15.1 ± 0.5°), and the values of this parameter increased in the order of UC < SiW < CG < MS. Substrate roughness also played a key role in controlling spherulite formation. SiW, UC, and CG had isotropic surfaces with low average roughness, facilitating spherulite formation. Overall, this work demonstrates that it is possible to successfully produce SS spherulites using a single step process at room temperature. Furthermore, the formation of SS spherulites can be tuned by the hydrophobicity of the substrate, an approach that could be applied to assembling spherulites of other small organic molecules. [ABSTRACT FROM AUTHOR]

Oxidation by persulfates at elevated temperatures (thermally activated persulfates) disintegrates bacterial cells and extracellular polymeric substances (EPS) composing waste-activated sludge (WAS), facilitating the subsequent sludge dewatering. The WAS disintegration process by thermally activated persulfates exhibited different behaviors depending on the types of persulfates employed, that is, peroxymonosulfate (PMS) versus peroxydisulfate (PDS). The decomposition of PMS in WAS proceeded via a two-phase reaction, an instantaneous decomposition by the direct reaction with the WAS components followed by a gradual thermal decay. During the PMS treatment, the WAS filterability (measured by capillary suction time) increased in the initial stage but rapidly stagnated and even decreased as the reaction proceeded. In contrast, the decomposition of PDS exhibited pseudo first-order decay during the entire reaction, resulting in the greater and steadier increase in the WAS filterability compared to the case of PMS. The treatment by PMS produced a high portion of true colloidal solids (<1 μm) and eluted soluble and bound EPS, which is detrimental to the WAS filterability. However, the observations regarding the dissolved organic carbon, ammonium ions, and volatile suspended solids collectively indicated that the treatment by PMS more effectively disintegrated WAS compared to PDS, leading to higher weight (or volume) reduction by postcentrifugation. [ABSTRACT FROM AUTHOR]

Hydrated ions are crucially important in a wide array of environments, from biology to the atmosphere, and the presence and concentration of ions in a system can drastically alter its behavior. One way in which ions can affect systems is in their interactions with proteins. The Hofmeister series ranks ions by their ability to salt-out proteins, with kosmotropes, such as sulfate, increasing their stability and chaotropes, such as perchlorate, decreasing their stability. We study hydrated perchlorate clusters as they are strongly chaotropic and thus exhibit different properties than sulfate. In this study we simulate small hydrated perchlorate clusters using a basin-hopping geometry optimization search with empirical potentials. We compare topological features of these clusters to data from both computational and experimental studies of hydrated sulfate ions and draw some conclusions about ion effects in the Hofmeister series. We observe a patterning conferred to the water molecules within the cluster by the presence of the perchlorate ion and compare the magnitude of this effect to that observed in previous studies involving sulfate. We also investigate the influence of the overall ionic charge on the low-energy structures adopted by these clusters. [ABSTRACT FROM AUTHOR]

We demonstrated a new method of synthesizing crystalline organic cation conductors. The conductivities of various organic cations involved in a one-dimensional zinc sulfate framework were studied. The optimized structure (EMIm)2[Zn(SO4)2] exhibited an ionic conductivity of 3.8 x 10-3 S cm-1 at 210 °C, which is comparable to that of highly conductive organic ionic plastic crystals. The high ionic conductivity is attributable to the defect structures of the organic cations in the inorganic frameworks. The pulsed-field gradient solid-state NMR technique revealed that the self-diffusion coefficient of organic cations in the zinc sulfate at 80 °C is comparable to that of the popular ionic liquid EMIm-BF4 at 30 °C, which indicates that liquid-like fast transporting of organic cation is achieved in the robust crystal structure. [ABSTRACT FROM AUTHOR]

Polyoxyethylene(20) cetyl ether (C56H114O21, POELE20) and three sulfate salts (Li2SO4, ZnSO4, and MgSO4) were used as phase-forming material of the aqueous two-phase system, and the binodal data was measured at the three temperatures (288.15, 298.15, 308.15 K). Three classic experienced formulas were used to fit the binodal data, and they had better performance in data association. The tie-line data of studied systems were measured and fitted by the empirical formulas, i.e., Othmer-Tobias and Bancroft equations. It has better performance in data association. For the investigated systems, the influence of the salt type on the binodal curves was studied by the Gibbs free energy of ions hydration and effective excluded volume, and the influence of temperature on the tie-lines and binonal curves was also discussed. First, as it is confirmed, when the salts are of the same anion, salts with higher cation valence will have stronger abilities of salting out; the salting out abilities of salts strengthen with the increasing absolute value of Gibbs free energies of cations. Second, the salting-out abilities of salts enhance with the increase in system effective excluded volume in the investigated systems. Third, the studied aqueous two-phase systems are more prone to formation at the higher temperature than those at lower temperature. Finally, for the tie-lines in the studied systems, the absolute value of slope decreases with the temperature falling. [ABSTRACT FROM AUTHOR]

The crystallization mechanisms and kinetics of micellar sodium dodecyl sulfate (SDS) solutions in water, under isothermal conditions, were investigated experimentally by a combination of reflection optical microscopy (OM), differential scanning calorimetry (DSC), and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). The rates of nucleation and growth were estimated from OM and DSC across temperatures ranging from 20 to -6 °C for 20% SDS-H2O, as well as for 10 and 30% SDS-H2O at representative temperatures of 6, 2, and -2 °C. A decrease in temperature increased both nucleation and growth rates, and the combined effect of the two processes on the morphology was quantified via both OM and ATR-FTIR. Needles, corresponding to the hemihydrate polymorph, become the dominant crystal form at ≤ -2 °C, while platelets, the monohydrate, predominate at higher temperatures. Above 8 °C, crystallization was only observed if seeded from crystals generated at lower temperatures. Our results provide quantitative and morphological insight into the crystallization of ubiquitous micellar SDS solutions and its phase stability below room temperature. [ABSTRACT FROM AUTHOR]

N-Methyl-d-aspartate receptors (NMDARs) display a critical role in various diseases of the central nervous system. The activity of NMDARs can be modulated by neurosteroids. Herein, we report a structure-activity relationship study for perhydrophenanthrene analogues possessing a framework that mimics the steroidal ring system. This study comprises the design, synthesis, and assessment of the biological activity of a library of perhydrophenanthrene 2-sulfates and 2-hemisuccinates (1-10). Their ability to modulate NMDAR-induced currents was tested on recombinant GluN1/GluN2B receptors. Our results demonstrate that such structural optimization leads to compounds that are inhibitors of NMDARs. Notably, compound 9 (IC50 = 15.6 μM) was assessed as a more potent inhibitor of NMDAR-induced currents than the known endogenous neurosteroid, pregnanolone sulfate (IC50 = 24.6 μM). [ABSTRACT FROM AUTHOR]

The classic technique for sulfate analysis in an undergraduate quantitative analysis lab involves precipitation as the barium salt with barium chloride, collection of the precipitate by gravity filtration using ashless filter paper, and removal of the filter paper by charring over a Bunsen burner. The entire process is time-consuming, hazardous, and frequently yields poor results. Titrimetric methods are much faster, but a good indicator has not been found for sulfate titrations. However, because the relative concentrations of ions in solution change during a titration sequence, monitoring conductivity during the progress of a titration produces a signal which can be used to indicate the equivalence point. A conductometric titration protocol has been developed which is relatively rapid, inexpensive, and can produce results as accurate as the classic technique in an undergraduate laboratory. [ABSTRACT FROM AUTHOR]

meta-Phenylenediamine based two linear bis-urea anion receptors, L1 (meta-nitro) and L2 (para-nitro), have been synthesized which showed strong binding affinities toward halides as well as planar and tetrahedral oxyanions. In the presence of excess fluoride anion, L1 self-assembles to entrap a cyclic fluoride-water tetrameric cluster within its tetrameric pillar-like assembly of each urea arm (complex 1a). In the presence of sulfate anion, L1 self-assembles in an identical fashion to entrap the bigger tetrahedral anion (complex 1b), whereas two urea moieties of two different receptor molecules of L1 have been structurally authenticated to be sufficient to stabilize the simple Y-shaped acetate anion in complex 1c. On the other hand, receptor L2, with a bis(para-nitro urea) functional group, especially in the presence of sulfate anion, self-assembles like long straight pillars entrapping sulfate-water-sulfate cluster {SO42--(H2O)3-SO42-} (complex 2a). Additionally, L2 forms a host-guest assembly with the cation and solvent (DMSO) coordinated bromide anion (complex 2b) when treated with excess bromide anion as n-tetrabutylammonium salt. All the complexes have been characterized by powder X-ray diffraction and ¹H NMR and 13C NMR spectroscopy, which are in full support and consistent with solid-state single crystal X-ray diffraction results. [ABSTRACT FROM AUTHOR]

Se-catalyzed disproportionation of bisulfite (HSO3-) is a facile and potential wet flue gas desulfurization. In this paper, the kinetics and mechanism of Se-catalyzed disproportionation of HSO3- were systematically investigated. The Se-catalyzed disproportionation of HSO3- is found to be pseudo-first-order with respect to the HSO3- and Se concentrations, and is zeroth-order with respect to the initial pH value. More importantly, the kinetics of Se-catalyzed disproportionation of HSO3- can be divided into two stages, i.e., a rate-controlling stage and an acceleration stage. In the rate-controlling stage, the reaction rate is slow and the intermediate HSeSO3- forms. This intermediate is decisive to accelerate the HSO3- disproportionation, and thus, it plays an important role in the Se-catalyzed process. Furthermore, a kinetic equation is determined according to the results: r0 = k1[HSO3-]0.94[Se]1.13, where k1 = (10.88 ± 0.04) × 10-2 M-1.07.min-1. This kinetics prediction model is fitted well with the experimental data, indicating that this model can satisfactorily describe the experimental kinetic data of Se-catalyzed disproportionation of HSO3-. [ABSTRACT FROM AUTHOR]

Ultraviolet light (UV) combined with peroxy chemicals, such as H2O2 and peroxydisulfate (PDS), have been considered potentially highly effective disinfection processes. This study investigated the inactivation of Escherichia coli, bacteriophage MS2, and Bacillus subtilis spores as surrogates for pathogens under UV/H2O2 and UV/PDS conditions, with the aim to provide further understanding of UV-based advanced disinfection processes (ADPs). Results showed that one additional log of inactivation of E. coli was achieved with 0.3 mM H2O2 or PDS at 5.2 × 10-5 Einstein.L-1 photo fluence (at 254 nm) compared with UV irradiation alone. Addition of H2O2 and PDS greatly enhanced the inactivation rate of MS2 by around 15 folds and 3 folds, respectively, whereas the inactivation of B. subtilis spores was slightly enhanced. Reactive species responsible for the inactivation were identified to be • OH, SO4.-, and CO3.- based on manipulation of solution conditions. The CT value of each reactive species was calculated with respect to each microbial surrogate, which showed that the disinfection efficacy ranked as • OH > SO4.- > CO3.- ⪢ O2.-/HO2.. A comprehensive dynamic model was developed and successfully predicted the inactivation of the microbial surrogates in surface water and wastewater matrices. The concepts of UV-efficiency and EE/O were employed to provide a cost-effective evaluation for UV-based ADPs. Overall, the present study suggests that it will be beneficial to upgrade UV disinfection to UV/H2O2 ADP for the inactivation of viral pathogens. [ABSTRACT FROM AUTHOR]

The first example of a triple formato/hydroxido/sulfato (FHS) bridge for any metal is reported in compound [Cu2(bpym)(OH)(HCO2)(SO4)(H2O)2]·3H2O (1). Its structure shows the presence of alternating triple FHS bridges and 2,2'-bipyrimidine (bpym) ones. Although in the initial synthesis the sulfate anions were introduced accidentally, here we report the rational synthesis and the magnetic properties of this compound. The magnetic properties show that 1 is an alternating ferro/antiferromagnetic (F/AF) chain compound with predominant antiferromagnetic interactions and were fit to an alternating F/AF S = 1/2 chain with g = 2.103, JAF = -139 cm-1, and JF = 116 cm-1 (α = JF/|JAF| = 0.83). The JAF value found corresponds very well to those previously reported for Cu-bpym-Cu bridges (average value of ca. -150 cm-1). The JF value is also very close to the estimated one (ca. 100 cm-1) from magneto-structural correlations in triply Cu-Cu bridged compounds with both hydroxido and carboxylato bridges in equatorial positions. [ABSTRACT FROM AUTHOR]

In a previous study, we applied quantum chemical methods to study the reaction between sulfur dioxide (SO2) and the sulfate radical ion (SO4-) at atmospheric relevant conditions and found that the most likely reaction product is SO3SO3-. In the current study, we investigate the chemical fate of SO3SO3- by reaction with ozone (O3) using first-principles molecular dynamics collision simulations. This method assesses both dynamic and steric effects in the reactions and therefore provides the most likely reaction pathways. We find that the majority of the collisions between SO3SO3- and O3 are nonsticking and that the most frequent reactive collisions regenerate sulfate radical ions and produce sulfur trioxide (SO3) while ejecting an oxygen molecule (O2). The rate of this reaction is determined to be 2.5 × 10-10 cm3 s-1. We then conclude that SO4- is a highly efficient catalyst in the oxidation of SO2 by O3 to SO3. [ABSTRACT FROM AUTHOR]

Heterogeneous reactions of dinitrogen pentoxide (N2O5) on aerosol particles impact air quality and climate, yet aspects of the relevant physical chemistry remain unresolved. One important consideration is the competing effects of diffusion and the rate of chemical reaction within the particle, which determines the length that N2O5 travels within a particle before reacting, referred to as the reacto-diffusive length (l). Large values of l imply a dependence of the reactive uptake efficiency of N2O5, i.e., γ(N2O5), on particle size. We present measurements of the size dependence of γ(N2O5) on aqueous sodium chloride, ammonium sulfate, and ammonium bisulfate particles. γ(N2O5) on ammonium sulfate and ammonium bisulfate particles ranged from 0.016 ± 0.005 to 0.036 ± 0.001 as the surface-area-weighted particle radius increased from 39 to 127 nm, resulting in an estimated l of 32 ± 6 nm. In contrast, γ(N2O5) on sodium chloride particles was independent of particle size, suggesting a near-surface reaction dominated the uptake of N2O5. Differences in the reactivity of the N2O5 intermediate, NO2+, with water and chloride can explain the observed dependencies. These results allow for parameterizations in atmospheric models to determine a more robust population mean value of γ(N2O5) that accounts for the distribution of particle sizes. [ABSTRACT FROM AUTHOR]

Bacillus sp. TB-90 urate oxidase (BTUO) is one of the most thermostable homotetrameric enzymes. We previously reported [Hibi, T., et al. (2014) Biochemistry 53, 3879-3888] that specific binding of a sulfate anion induced thermostabilization of the enzyme, because the bound sulfate formed a salt bridge with two Arg298 residues, which stabilized the packing between two ß-barrel dimers. To extensively characterize the sulfate-binding site, Arg298 was substituted with cysteine by site-directed mutagenesis. This substitution markedly increased the protein melting temperature by ~20 °C compared with that of the wild-type enzyme, which was canceled by reduction with dithiothreitol. Calorimetric analysis of the thermal denaturation suggested that the hyperstabilization resulted from suppression of the dissociation of the tetramer into the two homodimers. The crystal structure of R298C at 2.05 Å resolution revealed distinct disulfide bond formation between the symmetrically related subunits via Cys298, although the Cβ distance between Arg298 residues of the wild-type enzyme (5.4 Å apart) was too large to predict stable formation of an engineered disulfide cross-link. Disulfide bonding was associated with local disordering of interface loop II (residues 277-300), which suggested that the structural plasticity of the loop allowed hyperstabilization by disulfide formation. Another conformational change in the C-terminal region led to intersubunit hydrogen bonding between Arg7 and Asp312, which probably promoted mutant thermostability. Knowledge of the disulfide linkage of flexible loops at the subunit interface will help in the development of new strategies for enhancing the thermostabilization of multimeric proteins. [ABSTRACT FROM AUTHOR]

The recovery of water during inland desalination processes using reverse osmosis, or RO, is often limited by the solubility of calcium sulfate, or CaSO4. Reducing or eliminating the presence of sulfate from the feedwater will allow the process to be operated at higher recoveries and produce less waste brine. Ion exchange may be used as a pretreatment method for the control and removal of sulfate using a hybrid ion exchange-reverse osmosis (HIX-RO) process. However, for viable application, it is imperative that the process is self-regenerating; that is, the use of external regenerants has to be avoided altogether. Various properties of the ion-exchange resin control the overall selectivity toward sulfate including the resin matrix and basicity of the functional group. Finer control over selectivity is also possible through mixing of characteristically different ion exchange resins. This study focused on how mixing anion exchange resins with different matrix and functional groups may optimize sulfate/chloride selectivity avoiding precipitation of CaSO4 for a specific brackish water. Finally, lab-scale results from an HIX-RO system are presented demonstrating higher RO recovery with no need for an external regenerant. [ABSTRACT FROM AUTHOR]

Aggregation behavior of a series of neat 1-ethyl 3-methylimidazolium alkyl sulfate (alkyl = ethyl, butyl, hexyl, and octyl) ionic liquids has been investigated through combined time-resolved fluorescence spectroscopy, 1-D and 2-D NMR spectroscopy, and fluorescence correlation spectroscopy (FCS). Interestingly, experimentally measured rotational relaxation times (τr) for ethyl, butyl, hexyl and octyl systems are measured to be 2.25, 1.64, 1.36, and 1.32 times higher than the estimated (from Stokes-Einstein-Debye theory) values for the same respective systems. This indicates that the emitting species is not the monomeric imidazolium moiety rather an associated species, and volume of the rotating fluorescing species decreases even though the length of the alkyl moiety on the anions is increased. The shift in the ¹H proton signal as well as a change in the width of the same signal upon dilution of the neat ionic liquids indicates that ionic liquids exist in the aggregated form. Further investigation through the 2D-ROESY experiment shows that interaction between imidazolium and sulfate is relatively stronger in the ethyl system than that of the longer octyl system. FCS measurements independently show that the hydrodynamic volume decreases with an increase in the anion chain length. The NMR and FCS results are consistent with the findings of the fluorescence anisotropy study. [ABSTRACT FROM AUTHOR]

Syntrophic relationships between fermentative and sulfate-reducing bacteria are essential to lignocellulose-based systems applied to the passive remediation of mining-influenced waters. In this study, seven pilot-scale sulfate-reducing bioreactor columns containing varying ratios of alfalfa hay, pine woodchips, and sawdust were analyzed over ∼500 days to investigate the influence of substrate composition on zinc removal and microbial community structure. Columns amended with >10% alfalfa removed significantly more sulfate and zinc than did wood-based columns. Enumeration of sulfate reducers by functional signatures (dsrA) and their putative identification from 16S rRNA genes did not reveal significant correlations with zinc removal, suggesting limitations in this directed approach. In contrast, a strong indicator of zinc removal was discerned in comparing the relative abundance of core microorganisms shared by all reactors (>80% of total community), many of which had little direct involvement in metal or sulfate respiration. The relative abundance of Desulfosporosinus, the dominant putative sulfate reducer within these reactors, correlated to representatives of this core microbiome. A subset of these clades, including Treponema, Weissella, and Anaerolinea, was associated with alfalfa and zinc removal, and the inverse was found for a second subset whose abundance was associated with wood-based columns, including Ruminococcus, Dysgonomonas, and Azospira. The construction of a putative metabolic flowchart delineated syntrophic interactions supporting sulfate reduction and suggests that the production of and competition for secondary fermentation byproducts, such as lactate scavenging, influence bacterial community composition and reactor efficacy. [ABSTRACT FROM AUTHOR]

Gas-liquid scattering experiments were employed to measure the entry and dissociation of the acidic gas DCl into salty glycerol coated with dodecyl sulfate ions (DS- = CH3(CH2)11OSO3-). Five sets of salty solutions were examined: 0.25 and 0.5 M NaCl, 0.25 M MgCl2, 0.25 M CaCl2, and artificial sea salt. DS- bulk concentrations were varied from 0 to 11 mM, generating DS- surface coverages of up to 34% of a compact monolayer, as determined by surface tension and argon scattering measurements. DS- surface segregation is enhanced by the dissolved salts in the order MgCl2 CaCl2 > sea salt > NaCl. We find that DCl penetration through the dodecyl chains decreases at first gradually and then sharply as more chains segregate to the surface, dropping from 70% entry on bare glycerol to 11% for DS- surface concentrations of 1.8 × 1014 cm-2. When plotted against DS- surface concentration, the DCl entry probabilities fall within a single band for all solutions. These observations imply that the monovalent Na+ and divalent Ca2+ and Mg2+ ions do not bind differently enough to the ROSO3- headgroup to significantly alter the diffusive passage of DCl molecules through the dodecyl chains at the same DS- chain density. The chief difference among the salts is the greater propensity for the divalent salts to expel the soluble ionic surfactant to the surface. [ABSTRACT FROM AUTHOR]

The oxidation of SO2(g) on the interfacial layers of microdroplet surfaces was investigated using a spray-chamber reactor coupled to an electrospray ionization mass spectrometer. Four major ions, HSO3-, SO3-, SO4- and HSO4-, were observed as the SO2(g)/N2(g) gas-mixture was passed through a suspended microdroplet flow, where the residence time in the dynamic reaction zone was limited to a few hundred microseconds. The relatively high signal intensities of SO3-, SO4-, and HSO4- compared to those of HSO3- as observed at pH < 3 without addition of oxidants other than oxygen suggests an efficient oxidation pathway via sulfite and sulfate radical anions on droplets possibly via the direct interfacial electron transfer from HSO3- to O2. The concentrations of HSO3- in the aqueous aerosol as a function of pH were controlled by the deprotonation of hydrated sulfur dioxide, SO2·H2O, which is also affected by the pH dependent uptake coefficient. When H2O2(g) was introduced into the spray chamber simultaneously with SO2(g), HSO3- is rapidly oxidized to form bisulfate in the pH range of 3 to 5. Conversion to sulfate was less at pH < 3 due to relatively low HSO3- concentration caused by the fast interfacial reactions. The rapid oxidation of SO2(g) on the acidic microdroplets was estimated as 1.5 106 [S(IV)] (M s-1) at pH ≤ 3. In the presence of acidic aerosols, this oxidation rate is approximately 2 orders of magnitude higher than the rate of oxidation with H2O2(g) at a typical atmospheric H2O2(g) concentration of 1 ppb. This finding highlights the relative importance of the acidic surfaces for SO2 oxidation in the atmosphere. Surface chemical reactions on aquated aerosol surfaces, as observed in this study, are overlooked in most atmospheric chemistry models. These reaction pathways may contribute to the rapid production of sulfate aerosols that is often observed in regions impacted by acidic haze aerosol such as Beijing and other megacities around the world. [ABSTRACT FROM AUTHOR]

A transition-metal-free, K2S2O8-mediated intramolecular oxidative nitrogenation/oxygenation of C(sp³)-H in N-aryl benzylic amines followed by oxidation at the benzylic center has been developed for the synthesis of benzamidine/benzoxazine heterocycles, providing an expedient access to quinazolin-4(3H)-ones, N-aryl-2-arylbenzimidazoles, and 4H-3,1-benzoxazin-4-ones. A considerable amount of work dealing with the mechanistic study to understand the crucial intramolecular cyclization step largely favors an iminium ion as the key intermediate. [ABSTRACT FROM AUTHOR]