Nanofiltration for the concentration of heat stable salts prior to MEA reclamation

While monethanolamine has shown great potential as a solvent for the capture of carbon dioxide, impurities can build within the solution over time, leading to increased viscosity and corrosivity. Classically, these impurities are removed by a combination of neutralization and either thermal reclamation, ion exchange or electrodialysis. In this work, we evaluate the use of nanofiltration to concentrate the heat stable salts within the solution prior to such reclamation. This allows the recirculating solvent to operate with low concentrations of these impurities, while providing a low volume, concentrated solution for reclamation. Results show that nanofiltration can reject greater than 80% of the heat stable anions, while allowing the monoethanolamine to permeate through the membrane, for return to the process. Rejection of the MEA itself is less than 7%. The nanofiltration operation is only effective on lean solvent with CO2 loadings of less than 0.2 and neutralization would be required upstream to deprotonate the amine. The two membranes tested (Koch MPF-34 and MPF-36) appeared stable to exposure to the solvent for over four months.

Degradation of organic dyes by P25-reduced graphene oxide: influence of inorganic salts and surfactants

Treatment of coloured effluent treatment is a major issue for the textile industry. In this study, catalyst P25-graphene was prepared and applied for degrading dye from an aqueous solution. Three types of dyes were selected to determine the feasibility of the catalyst for the dye degradation, including sulphonic, azoic, and fluorescent dyes. P25-graphene catalyst showed good ability to degrade all selected dyes. The influence of inorganic salts and surfactants on the photocatalytic degradation of rhodamine B using catalyst P25-graphene was also investigated. The degradation of rhodamine B was suppressed by the presence of NaCl, but the effect of Na2SO4 was negligible. The degradation of rhodamine B was significantly suppressed by all three types of surfactant, namely anionic, cationic and non-ionic surfactants. NMR technique was used to investigate the mechanisms associated with this suppression.

Novel imidazolinium ionic liquids and organic salts

The preparation and physical properties of a novel family of ionic liquids and organic salts based on the imidazolinium cation are described, and compared with their imidazolium analogues in some cases. Ionic liquids were obtained with the triflate, formate and salicylate anions, while > 100 °C melting points were observed with acetate and several other benzoate derivatives. The triflate salt was less ion-conductive than the corresponding imidazolium salt, but less so than expected on the basis of its viscosity, suggesting a contribution from proton conductivity. The electrochemical window of the imidazolinium was slightly extended in the reductive direction, due to the lower proton activity produced by the cation in this case. Imidazolinium salts are also known to exhibit anti-corrosion properties and hence a preliminary study of this property is also reported; 2-methylimidazolinium 4-hydroxycinnamate was found to show strong anodic corrosion inhibition on mild steel.

Elucidation of transport mechanism and enhanced alkali ion transference numbers in mixed alkali metal-organic ionic molten salts

Mixed salts of Ionic Liquids (ILs) and alkali metal salts, developed as electrolytes for lithium and sodium batteries, have shown a remarkable ability to facilitate high rate capability for lithium and sodium electrochemical cycling. It has been suggested that this may be due to a high alkali metal ion transference number at concentrations approaching 50 mol% Li(+) or Na(+), relative to lower concentrations. Computational investigations for two IL systems illustrate the formation of extended alkali-anion aggregates as the alkali metal ion concentration increases. This tends to favor the diffusion of alkali metal ions compared with other ionic species in electrolyte solutions; behavior that has recently been reported for Li(+) in a phosphonium ionic liquid, thus an increasing alkali transference number. The mechanism of alkali metal ion diffusion via this extended coordination environment present at high concentrations is explained and compared to the dynamics at lower concentrations. Heterogeneous alkali metal ion dynamics are also evident and, somewhat counter-intuitively, it appears that the faster ions are those that are generally found clustered with the anions. Furthermore these fast alkali metal ions appear to correlate with fastest ionic liquid solvent ions.

Modelling solute transport in structured soils: performance evaluation of the ADR and TRM models

The movement of chemicals through the soil to the groundwater or discharged to surface waters represents a degradation of these resources. In many cases, serious human and stock health implications are associated with this form of pollution. The chemicals of interest include nutrients, pesticides, salts, and industrial wastes. Recent studies have shown that current models and methods do not adequately describe the leaching of nutrients through soil, often underestimating the risk of groundwater contamination by surface-applied chemicals and overestimating the concentration of resident solutes. This inaccuracy results primarily from ignoring soil structure and nonequilibrium between soil constituents, water, and solutes. A multiple sample percolation system (MSPS), consisting of 25 individual collection wells, was constructed to study the effects of localized soil heterogeneities on the transport of nutrients (NO−3, Cl−, PO3−4) in the vadose zone of an agricultural soil predominantly dominated by clay. Very significant variations in drainage patterns across a small spatial scale were observed (one-way ANOVA, p < 0.001 indicating considerable heterogeneity in water flow patterns and nutrient leaching. Using data collected from the multiple sample percolation experiments, this paper compares the performance of two mathematical models for predicting solute transport, the advective-dispersion model with a reaction term (ADR), and a two-region preferential flow model (TRM) suitable for modelling nonequilibrium transport. These results have implications for modelling solute transport and predicting nutrient loading on a larger scale.

Selective determination of amino acids using flow injection analysis coupled with chemiluminescence detection

The determination of the amino acids proline, histidine, tyrosine, arginine, phenylalanine and tryptophan using flow injection analysis (FIA) with chemiluminescence detection is described. Proline was the only amino acid to exhibit chemiluminescence with the tris(2,2-bipyridyl)ruthenium(III) reaction at pH 10. While, histidine was found to selectively enhance the reaction of luminol with Mn(II) salts in a basic medium. Acidic potassium permanganate chemiluminescence was able to selectively determine tyrosine at pH 6.75. Low pressure separations using a C18 guard column allowed the simultaneous determination of tyrosine and tryptophan or phenylalanine and tryptophan with acidic potassium permanganate and copper(II)–amino acid–hydrogen peroxide chemiluminescence, respectively. Precision for each method was less than 3.9% (R.S.D.) for five replicates of a standard (1×10−5 M) and the detection limits ranged between 4×10−9 and 7×10−6 M. Preliminary investigations revealed that the methodology developed was able to selectively determine the individual amino acids in an equimolar mixture of the 20 naturally occurring amino acids.

Single enatiomer free-radical chemistry - Lewis acid-mediated reductions of racemic halides using chiral non-racemic stannanes

Additions of one to two equivalents of Lewis acids that include magnesium salts to free-radical reduction reactions involving ester functionalized radicals and (1R,2S,5R)-menthyldiphenyltin hydride 4, bis((1R,2S,5R)-menthyl)phenyltin hydride 5, tris((1R,2S,5R)-menthyl)tin hydride 6, bis((1R,2S,5R)-menthyl)-[8-(N,N-dimethylamino)naphthyl]tin hydride 12, bis((1R,2S,5R)-menthyl)-[1-((S)-N,N-dimethylaminoethyl)phenyl]tin hydride 13 or 3α-dimethylstannyl-5α-cholestane 14 result in remarkable enantioselectivities. Examples include (S)-naproxen ethyl ester 16, produced in 74% yield and greater than 99% ee at −78°C from the bromide and 5 in the presence of MgBr₂, and ethyl (R)-N-trifluoroacetyl-_D-phenylglycinate 18, obtained in 78% yield and 99% ee under identical conditions. Kinetic and computational studies provide insight into the origins of these observations.

Cross-adaptation and bitterness inhibition of L-Tryptophan, L-Phenylalanine and urea : further support for shared peripheral physiology

A previous study investigating individuals' bitterness sensitivities found a close association among three compounds: L-tryptophan (L-trp), L-phenylalanine (L-phe) and urea (Delwiche et al., 2001, Percept. Psychophys. 63, 761-776). In the present experiment, psychophysical cross-adaptation and bitterness inhibition experiments were performed on these three compounds to determine whether the bitterness could be differentially affected by either technique. If the two experimental approaches failed to differentiate L-trp, L-phe and urea's bitterness, then we may infer they share peripheral physiological mechanisms involved in bitter taste. All compounds were intensity matched in each of 13 subjects, so the judgments of adaptation or bitterness inhibition would be based on equal initial magnitudes and, therefore, directly comparable. In the first experiment, cross-adaptation of bitterness between the amino acids was high (>80%) and reciprocal. Urea and quinine-HCl (control) did not cross-adapt with the amino acids symmetrically. In a second experiment, the sodium salts, NaCl and Na gluconate, did not differentially inhibit the bitterness of L-trp, L-phe and urea, but the control compound, MgSO4, was differentially affected. The bitter inhibition experiment supports the hypothesis that L-trp, L-phe and urea share peripheral bitter taste mechanisms, while the adaptation experiment revealed subtle differences between urea and the amino acids indicating that urea and the amino acids activate only partially overlapping bitter taste mechanisms.

The effect of zinc on human taste perception

Zinc salts are added as a nutritional or functional ingredient in food and oral care products. The 1st experiment in this study investigated the taste and somatosensory effect of zinc salts (chloride, iodide, sulfate, bromide, acetate). The zinc salts had very little taste (bitter, salty, savory, sour, sweet), and the taste that was present was easily washed away with water rinses. The major oral quality of zinc was astringency, and the astringency lingered beyond expectoration. The 2nd experiment combined zinc salts with prototypical stimuli eliciting basic tastes. Zinc was a potent inhibitor of sweetness and bitterness (>70% reduction in taste) but did not affect salt, savory, or sour taste.

Spatial and temporal distribution of solute leaching in heterogeneous soils: analysis and application to multisampler lysimeter data

Accurate assessment of the fate of salts, nutrients, and pollutants in natural, heterogeneous soils requires a proper quantification of both spatial and temporal solute spreading during solute movement. The number of experiments with multisampler devices that measure solute leaching as a function of space and time is increasing. The breakthrough curve (BTC) can characterize the temporal aspect of solute leaching, and recently the spatial solute distribution curve (SSDC) was introduced to describe the spatial solute distribution. We combined and extended both concepts to develop a tool for the comprehensive analysis of the full spatio-temporal behavior of solute leaching. The sampling locations are ranked in order of descending amount of total leaching (defined as the cumulative leaching from an individual compartment at the end of the experiment), thus collapsing both spatial axes of the sampling plane into one. The leaching process can then be described by a curved surface that is a function of the single spatial coordinate and time. This leaching surface is scaled to integrate to unity, and termed S can efficiently represent data from multisampler solute transport experiments or simulation results from multidimensional solute transport models. The mathematical relationships between the scaled leaching surface S, the BTC, and the SSDC are established. Any desired characteristic of the leaching process can be derived from S. The analysis was applied to a chloride leaching experiment on a lysimeter with 300 drainage compartments of 25 cm2 each. The sandy soil monolith in the lysimeter exhibited fingered flow in the water-repellent top layer. The observed S demonstrated the absence of a sharp separation between fingers and dry areas, owing to diverging flow in the wettable soil below the fingers. Times-to-peak, maximum solute fluxes, and total leaching varied more in high-leaching than in low-leaching compartments. This suggests a stochastic–convective transport process in the high-flow streamtubes, while convection–dispersion is predominant in the low-flow areas. S can be viewed as a bivariate probability density function. Its marginal distributions are the BTC of all sampling locations combined, and the SSDC of cumulative solute leaching at the end of the experiment. The observed S cannot be represented by assuming complete independence between its marginal distributions, indicating that S contains information about the leaching process that cannot be derived from the combination of the BTC and the SSDC.

Removal of arsenic from contaminated soils using different salt extractants

This study presents an environmental-friendly and cost effective method for the extraction of arsenic from contaminated soils.
Laboratory experiments using inorganic salts, potassium phosphate (KH2PO4), potassium chloride (KCl), potassium nitrate (KNO3), potassium sulfate (K2SO4), and sodium perchlorate (NaClO4) were evaluated as arsenic extractants. An Andosol soil was artificially contaminated with arsenite [As(III)] and arsenate [As(V)]. The soil was washed in a batch process with different salt solutions in the pH range 3–11 for 24 hours at 20◦C. Among the various potassium and sodium salts tested, KH2PO4 was found to be highly effective in extracting arsenic from As(III)-soil attaining more than 80% and 40% from As(V)-soil in neutral pH range. Other salts were particularly ineffective in extraction of arsenic from both soils. More arsenic was extracted more from the As(III)-soil than the As(V)-soil.

Synthesis, characterization and enantioselective free radical reductions of (1R,2S,5R)-menthyldiphenylgermane and its enantiomer

(1R,2S,5R)-Menthyldiphenylgermane and its enantiomer have been prepared in a few steps from germanium tetrachloride. The initial step in this sequence, namely the reaction between germanium tetrachloride and menthylmagnesium chloride, produces menthylgermanium trichloride, which is the exclusive product of this Grignard reaction, presumably due to the bulk of the menthyl group. When used at a low temperature (−78 °C) and in conjunction with Lewis acids, such as magnesium salts, these chiral germanes are capable of reducing ester functionalized radicals in high enantioselectivity, but in low-moderate yield. For example, (R)-naproxen ethyl ester was obtained in 15% yield and 99% ee by reaction in toluene of 2-bromonaproxen ethyl ester with (1R,2S,5R)-menthyldiphenylgermane in toluene at −78 °C in the presence of magnesium bromide. At 80 °C, (1R,2S,5R)-menthyldiphenylgermane reacted with primary alkyl radicals with a rate constant of 1.02 × 10⁶ M⁻¹ s⁻¹. Kinetic studies reveal the Arrhenius expression for this reaction to be: log(k/M⁻¹ s⁻¹) = (11.1 ± 0.4) − (34.6 ± 3.1)/θ where θ=2.3RT kJ mol⁻¹.

Optimization of process parameters for the production of naringinase by Aspergillus niger MTCC 1344

Aspergillus niger MTCC 1344 was used to produce extracellular naringinase in a complex (molasses, yeast extract and salts) medium. An initial medium pH 4.5 and cultivation temperature 30 °C were optimal for enzyme production. Among various carbon and organic nitrogen sources used, molasses and peptone were the most effective for enzyme yield. The rate of enzyme production was enhanced when metal ions were added to the medium. Fermentation conditions are described which produced a higher rate of enzyme synthesis. An increase in initial sugar concentration from 6 to 10 g l⁻¹ in the fermentation medium produced decreased naringinase synthesis while cell mass growth increased with the increase of sugar concentration. At a higher sugar level (10 g l⁻¹) the production of cell mass decreased.