Gas Solution Research Articles

New General Models for Evaluating Interactions in Non-Regular Solutions and Adsorption Energies Based on Both Hansen's and Drago's Parameters

New General Models for Evaluating Interactions in Non-Regular Solutions and Adsorption Energies Based on Both Hansen's and Drago's Parameters

The factors that influence solubility in perfluoroalkane solvents

Data on the solubility of neutral compounds in perfluoro-hexane, -heptane, and –octane have been obtained from the literature. It is shown that water-solvent and gas-solvent partition coefficients, P and K respectively, are effectively the same for all three perfluoroalkanes. Linear free energy relationships, LFERs, have been set up for these partition coefficients, as log P and log K. Comparison of the LFER coefficients in the log K equation for perfluoroheptane with those for a large number of other solvents shows that perfluoroheptane is an unusual solvent, in that small nonpolar solutes are more soluble than in other solvents. The comparative solubility of small nonpolar gaseous compounds in perfluoroheptane is due to a combination of cavity and interaction terms. Calculations using Pierotti's version of Scaled Particle Theory indicates that the solute-perfluoroheptane unfavourable cavity term is always smaller than that for solution in other solvents, which by itself would lead to enhanced solubilities in perfluoroheptane, as shown by small nonpolar solutes. As the solute becomes larger and more polar, the favourable interaction terms in other organic solvents become much larger than the corresponding interaction terms in perfluoroheptane. This results in the larger and/or more polar gaseous solutes being much more soluble in other organic solvents than in perfluoroheptane.

On the emergence of diel solute signals in flowing waters

AbstractBiota imprint their stoichiometry on relative rates of elemental cycling in the environment. Despite this coupling, producer‐driven diel solute variation in rivers and streams is more apparent for some solutes (e.g., dissolved oxygen—DO) than others (e.g., nitrate— ). We hypothesized that these differences arise from atmospheric equilibration, with signals emerging and evolving differently for gaseous and nongaseous solutes. Measurements of DO and NO3 in a spring‐fed river, where constant inputs isolate in‐stream processing, support this hypothesis, as do results from reactive transport modeling of river solute dynamics. Atmospheric equilibration dramatically shortens the benthic footprint over which signals integrate, facilitating emergence of diel DO signals in response to in‐stream metabolism. In contrast, upstream influences persist much further downstream for nongaseous solutes, confounding and potentially obscuring the diel signals from in‐stream assimilatory processing. Isolating diel NO3 signals from in‐stream processing requires a two‐station approach wherein metabolic impacts on solute variation are measured by difference between upstream and downstream sensors. Notably, two‐station inference improves markedly when hydraulic controls on signal propagation such as dispersion and storage are explicitly considered. We conclude that the absence of diel signals at a single station for nongaseous solutes such as cannot be interpreted as lack of autotroph demand or element coupling. As advances in sensors enable the acquisition of an increasingly rich array of solute signals, controlling for differences in the emergence and downstream evolution of gaseous versus nongaseous solutes will dramatically improve inferences regarding the timing and magnitude of coupled elemental processing.

A simple and timesaving method for the mass-transfer assessment of solvents used in physical absorption

A simple dynamic absorption procedure to assess the mass-transfer performances of a solvent toward a selected gaseous solute is presented. Absorption was operated semi-continuously at transient state until the equilibrium was reached without solvent recirculation. Four volatile organic compounds (VOC) more or less hydrophobic (toluene, acetone, dichloromethane, isopropanol) were absorbed in water and two heavy organic solvents (Bis(2-ethylhexyl) adipate DEHA and polydimethylsiloxane PDMS). A numerical resolution procedure was developed to simulate the gas–liquid mass-transfer and to deduce the VOC partition coefficients, expressed as the Henry’s law constants, as well as the overall liquid-phase mass-transfer coefficients. The overall liquid-phase mass-transfer coefficients were correlated to the diffusion coefficients using the Higbie penetration theory. The results confirm the high selectivity of water whereas the two organic solvents, especially DEHA, exhibit rather good affinity with all VOC even if the Henry’s law constants of the most soluble and the less soluble compounds for those solvents differ by 1 or 2 orders of magnitude. The liquid-film mass-transfer coefficients in the two organic solvents, even being more viscous, are larger than in water which confirms their good potential for hydrophobic VOC treatment.

Physical–chemical properties of gas–liquid contactors in packed absorption column

The burning of combustible material that produces emissions released to the atmosphere results in unfavorable climate change due to emissions of CO2, NOx, and acid rain by SOx, endangering the health of the population. The treatment of combustion gases by means of a packed absorption column with a high-efficiency liquid–gas contactor material reduces pollutant emissions to the atmosphere, where combustion gases make contact with aqueous amine solution of mono ethanol amine (MEA), using different structured packing materials which can be metallic, polymeric, or ceramic. The objective of this work is to study which one of these three types of materials of gas–liquid contactors presents the lowest deterioration in the presence of combustion gases flowing countercurrent to MEA. The materials were evaluated according to the Standard Test Methods ASTM G31-2004 for corrosion testing, ASTM E8-1998 for tension testing, ASTM E384-1990 for microhardness testing, ASTM G5-1999 for potentiodynamic and potentiostatic testing, and the procedure of NRF-194 PEMEX-2007. The properties studied were the tensile strengths, the hardness values, and the elastic moduli, before and after structured packing materials made contact with combustion gases in MEA aqueous solution. The results showed that in acidic and basic mediums, the metallic material was the most resistant to abrasion; it has the highest tensile strength, and presents more resistance during the stress test. The hardness results for the materials were metallic: 190 KH, polymeric: 20 KH, and ceramic: 700KH. The respective corrosion resistances in the presence of MEA were 1.63 × 10−3, 3.76 × 10−3, and 1.42 × 10−2 mm/year.

Virial equations of state for gaseous ammonia, water, carbon dioxide, and their mixtures at elevated temperatures and pressures

The available reference and experimental data on densities of the gaseous solutions, NH3–CO2, NH3–H2O, CO2–H2O, NH3–CO2–H2O and their components, NH3, CO2, H2O have been described as accurately as possible by virial equations of state in the temperature range from ~150 to 300°C and pressure range from 1 to 280 bar. More accurate and reliable values of the gas compressibility for the ternary NH3–CO2–H2O system and new data on the virial coefficients have been obtained. It was concluded that the obtained results are of interest for physical chemical simulations of many natural and technological processes particularly in the production of carbamide and other substances on the basis of urea.

Interfacial area measurements and surface area quantification for spray absorption

Abstract Sprays are widely used in the chemical industry for absorption operations such as gas conditioning and flue gas desulphurization. Despite the wide usage, spray absorption is poorly understood. For absorption applications, the rate of transfer of solute gas into all of the liquid drops is a strong function of the surface area of drops and hence the dropsize. Experimental measurements of dropsize at multiple locations within the spray plume and robust computation of the cumulative surface area of the drops is required to ascertain the liquid surface area availability. Further, the efficiency of spray contactors can be conveniently expressed in terms of the effective gas–liquid interfacial area measured using the standard chemical technique. The liquid surface area and the effective gas–liquid contact area inside spray columns can differ from each other on account of the large degree of absorption occurring during the process of atomization, and the internal stagnancy of small drops. Further, drop break-up, drop-drop interactions, collision of the spray plume with the column wall, and wall flow affect the liquid surface area availability and the effective gas–liquid contact area to varying degrees. As a result, it is essential to quantify both, the liquid surface area as well as the effective gas–liquid area inside spray columns to gain a fundamental understanding. Present study addresses this gap. Dropsize measurements using a Phase Doppler Interferometer (PDI), robust cumulative drop surface area quantification, and effective interfacial area measurements with the CO2-0.1 N NaOH system inside a 0.2 m ID laboratory spray column are presented. The effect of L/G ratio and gas–liquid contact height on the effective interfacial area and the cumulative drop surface area are elucidated. The effective interfacial area measurements are compared to results of previous researchers. Further, a methodology to compare the cumulative drop surface area with the effective interfacial area measurements is presented. Results from the study shows that a great degree of mass transfer does occur in the region in the vicinity of the nozzle tip. A large difference is observed in the cumulative drop surface area and the effective interfacial area on account of the large degree of CO2 absorption taking place during the process of atomization and the large number of internally stagnant drops. This work provides a fundamental insight into spray absorption and will guide in nozzle selection and robust design of spray columns.

Evolution of size and composition of a multicomponent gas bubble in liquid solution

The equations describing the transient and steady stages of size and composition evolution for a gas bubble which grows or shrinks due to the diffusion of several gases dissolved in liquid solution have been derived. The diffusion fluxes for gases in the liquid mixture caused by the bubble growth or dissolution were assumed to be quasistationary and the mixture of the gases in the bubble was treated as ideal. The analytical solutions for the obtained evolution equations have been found for bubbles of any size with an arbitrary number of components in the case of equal products of diffusivities and solubilities of dissolved gases in the liquid solution, and for sufficiently large binary bubbles for which capillary effects can be neglected.

Radon, CO2 and CH4 as environmental tracers in groundwater/surface water interaction studies − comparative theoretical evaluation of the gas specific water/air phase transfer kinetics

The applicability of radon as environmental tracer in groundwater/surface water interaction studies has been documented in a considerable number of publications. In some of these reports it has also been suggested to validate the radon based results by using CO2 and CH4 as supplementary tracers. The on-site measurement of the three gaseous parameters relies on their extraction from the water followed by the measurement of their concentration by means of mobile gas-in-air detectors. Since most related practical applications require the recording of time series, a continuous extraction of the gases from (e.g.) a permanently pumped water stream is necessary. A precondition for the sound combined interpretation of the resulting time series is that the individual temporal responses of the extracted gas-in-air concentrations to instantaneously changing gas-in-water concentrations are either identical or in reproducible relation to each other. The aim of our theoretical study was the comparison of the extraction behavior of the three gaseous solutes with focus on the individual temporal responses to changing gas-in-water concentrations considering in particular the gas specific water/air phase transfer kinetics. We could show that the overall mass transfer coefficients of radon, CO2 and CH4 result in a virtually similar temporal response to aqueous concentration changes, thus confirming the straightforward combined measurement/utilization of the dissolved gases as environmental tracers in groundwater/surface water interaction studies.

Application of artificial neural networks for estimation of solubility of acid gases (H2S and CO2) in 32 commonly ionic liquid and amine solutions

In the present study, the potential use of a model based on an artificial neural network (ANN) was investigated to predict the solubility of acid gases (H2S and CO2) in 32 commonly single and mixed amine and ionic liquid (IL) solutions over wide ranges of operating conditions. Temperature, partial pressure of acid gas (H2S or CO2), overall mass concentration, apparent molecular weight, critical temperature and critical pressure of solution were chosen as input variables of the proposed network. A collection of 733 experimental data points for H2S solubility (including train, test and validation data points) have been gathered from the literature to develop the network. The best parameters of the developed ANN containing the number of neurons, numbers of hidden layer and transfer function were acquired by using these data points. To evaluate the network accuracy, regression analysis with a data set including 169 data points for H2S solubility which were not considered in the training, testing and validation stages was applied. Furthermore, the extrapolation capability of the network was investigated by an extra data set (114 data points for CO2 solubility). The optimized network was trained by the Levenberg–Marquardt back-propagation algorithm with two hidden layers including 8 and 4 neurons and Tan-sigmoid transfer function for the hidden and output layers. The model results show that developed ANN model has ability to estimate accurately the solubility of acid gases in different solutions with Mean Relative Error (MRE) value of 3.104 and correlation coefficient (R2) of 0.997.

Absorption of combustion gases in boron solutions and recovery as industrial products

In this study, it is aimed that to reduce environmental effects of CO2 (as a greenhouse gas), to achieve absorption of CO2 in boron solutions and to yield a mixture product with boron compounds and the NaHCO3 which is raw material input especially in glass industry. In the laboratory scale experiments using autoclave, with different pressure, solid/liquid ratio, and different reaction times, absorption of CO2 in the boron solutions were examined and the Na-borate compounds containing NaHCO3 were produced. The characterization of the products was determined by XRD inspections and chemical analysis. In the studies, maximum 92.4% NaHCO3 bearing borate compounds was obtained. As a result of the purification of these products it was reached pure NaHCO3 by 99%.

Influence of (phenol and sodium sulfate) on the solubility of carbon dioxide in water

New experimental results are presented for the solubility and the partial molar volume of carbon dioxide in an aqueous solution of phenol and sodium sulfate at temperatures of about (314, 354, and 395)K and pressures up to about 10MPa. The composition of the solvent expressed as molality in water is about 0.5mol·(kgH2O)−1 for phenol as well as for sodium sulfate. The experimental work is a continuation of investigations on the influence of organic components and strong electrolytes on the solubility of carbon dioxide in water. It extends a data base for developing and testing thermodynamic models to describe the solubility of gases in salt-free and salt-containing aqueous solutions of organic compounds. The experimental results are compared to prediction and correlation results from a thermodynamic model. That model is a combination of a model for the solubility of CO2 in aqueous solutions of sodium sulfate on one side and a model for the solubility of CO2 in aqueous solutions of phenol on the other side. When ternary interactions between CO2, phenol, and sodium sulfate are neglected, the model allows prediction of the pressure that is required to dissolve a given amount of CO2 in the mixed aqueous solution. The prediction results reveal a reasonable agreement. However (and as in previous investigations with N,N-dimethylformamide instead of phenol as the organic solvent component or with sodium chloride instead of sodium sulfate as the dissolved electrolyte) adjusting a ternary parameter for interactions between the three solutes (i.e., CO2, phenol, and sodium sulfate) results in a correlation that allows description of the new experimental results almost within experimental uncertainty.

Fabrication and characterization of porous polyetherimide/montmorillonite hollow fiber mixed matrix membranes for CO2 absorption via membrane contactor

Asymmetric PEI hollow fiber mixed matrix membranes (MMMs) with improved structure and wetting resistance were fabricated via wet phase inversion method. The effects of incorporating hydrophobic MMT into polymer matrix in different loadings on the membrane properties were investigated. The membranes were characterized in terms of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), gas permeation test, hydrophobicity, wetting resistance and mechanical stability. All membranes possessed finger-like structures differing in skin layer thickness which increased with clay loading. The results revealed that the MMMs have significantly smaller pore size, higher porosity, hydrophobicity, LEPw and mechanical stability than plain PEI membrane. The membranes were further characterized by CO2 absorption test via contactor system using distilled water as absorbent and pure CO2 as solute gas. The results showed that the CO2 absorption performance increased with addition of MMT nano-clay. The membrane containing 1wt% MMT recorded the highest absorption flux of 2.35×10−3molm−2s−1 at the liquid velocity of 3ms−1, almost 135% higher than the flux of plain membrane at the same velocity. Comparatively, the flux of MMM was superior to several in-house made and commercial membranes.

Uncovering Implicit Assumptions: a Large-Scale Study on Students’ Mental Models of Diffusion

Students’ mental models of diffusion in a gas phase solution were studied through the use of the Structure and Motion of Matter (SAMM) survey. This survey permits identification of categories of ways students think about the structure of the gaseous solute and solvent, the origin of motion of gas particles, and trajectories of solute particles in the gaseous medium. A large sample of data (N = 423) from students across grade 8 (age 13) through upper-level undergraduate was subjected to a cluster analysis to determine the main mental models present. The cluster analysis resulted in a reduced data set (N = 308), and then, mental models were ascertained from robust clusters. The mental models that emerged from analysis were triangulated through interview data and characterised according to underlying implicit assumptions that guide and constrain thinking about diffusion of a solute in a gaseous medium. Impacts of students’ level of preparation in science and relationships of mental models to science disciplines studied by students were examined. Implications are discussed for the value of this approach to identify typical mental models and the sets of implicit assumptions that constrain them.

Examination of hydrogen-bonding interactions between dissolved solutes and alkylbenzene solvents based on Abraham model correlations derived from measured enthalpies of solvation

Enthalpies of solution at infinite dilution of 48 organic solutes in mesitylene and 81 organic solutes in p-xylene were measured using isothermal solution calorimeter. Enthalpies of solvation for 92 organic vapors and gaseous solutes in mesitylene and for 130 gaseous compounds in p-xylene were determined from the experimental and literature data. Abraham model correlations are determined from the experimental enthalpy of solvation data. The derived correlations describe the experimental gas-to-mesitylene and gas-to-p-xylene solvation enthalpies to within average standard deviations of 1.87kJmol−1 and 2.08kJmol−1, respectively. Enthalpies of XH⋯π (XO, N, and C) hydrogen bond formation of proton donor solutes (alcohols, amines, chlorinated hydrocarbons etc.) with mesitylene and p-xylene were calculated based on the Abraham solvation equation. Obtained values are in good agreement with the results determined using conventional methods.

Structured Packing Evaluation in Sour Gases Treatment from Kiln Emissions

The burning of pieces manufactured with clays to be used in the construction industry, contributes to environmental imbalance because it contains combustible materials that produce emissions released in the atmosphere. Up to now kilns have been used with combustion processes precarious and fuels highly polluting, which favor climate change emissions for CO2, NOx and acid rain by SOx, endangering the health of those living near these facilities. The treatment of combustion gases by means of a packed absorption column with a high efficiency liquidgas contactor reduces pollutant emissions to the atmosphere, when combustion gases are in contact with aqueous amine solution of Mono Ethanol Amine (MEA). The objective of this work is to study which one of three materials presents the lowest deterioration in the presence of combustion gases with MEA. The materials were tested according to American Society for Testing Materials ASTM G31-2004 corrosion testing, and the procedure NRF-194 PEMEX-2007. The properties studied were tensile strength, hardness and elastic modulus, before and after structured packing materials were in contact with combustion gases in MEA aqueous solution. The results showed that in acid and basic medium, the metallic material was the most resistant to abrasion; it has the major tensile strength, and presented more resistance in the stress test.

Prediction of Solubilities and Partition Coefficients in Polymers Using COSMO-RS

Recent results concerning the prediction of thermodynamic properties of solutes in polymers are presented. In particular, the computation of vapor–liquid and gas–liquid equilibria (i.e., liquid and gas solubilities) in different polymers and partition coefficients between the polymer and a solvent phase are addressed. Calculations have been carried out using COSMO-RS theory which combines quantum-chemical calculations with efficient statistical thermodynamics for intermolecular interactions. Predictions for vapor–liquid equilibria and for partition coefficients have been improved by incorporation of polymer-specific entropic contributions due to free volume effects. It is demonstrated that a high predictive accuracy is obtained if the polymer is sufficiently characterized by its composition, density, and crystallinity. The approach is currently limited to gaseous and liquid solutes and to linear, i.e. non-cross-linked polymers without any significant swelling.

Edible coatings as encapsulating matrices for bioactive compounds: a review.

Edible coatings can extend the shelf-life of many foods, controlling moisture and solute migration, gas exchange and oxidative reaction rates. Besides, edible coatings can be used as carriers of bioactive compounds to improve the quality of food products such as antioxidants, antimicrobials, flavors and probiotics. These approaches can be useful to extend shelf-life as well as provide a functional product. When edible coatings are used as a matrix holding bioactive compounds remarkable benefits arise; off odors and flavors can be masked, bioactive compounds are protected from the environment, and controlled release is allowed. In this sense, the present review will be focused on analyzing the potential use of encapsulation with edible coatings to incorporate bioactive compounds, solving the disadvantages of direct application.

A predictive model for the transport of copper by HCl-bearing water vapour in ore-forming magmatic-hydrothermal systems: Implications for copper porphyry ore formation

The solubility of copper chloride and metallic copper in low-density homogenous HCl-bearing aqueous fluids was investigated experimentally at temperatures between 350 and 550°C. Analysis of the resulting data and those on the solubility of copper chloride reported in Archibald et al. (2002) for temperatures between 280 and 320°C suggests that at temperatures <450°C, the solubility of copper chloride is controlled by a species having a Cu:Cl ratio of 1:1. The data also suggest that the solubility of copper chloride is controlled by the formation of hydrated copper clusters, i.e., CuCl:(H2O)n, and increases exponentially with H2O fugacity rather than linearly, as previously assumed. The hydration number (n) of the predominant cluster increases systematically with increasing pressure, and each of the gaseous solutions investigated at temperatures <450°C contains a mixture of clusters with different hydration numbers that predominate at different pressures. A model is proposed for the quantitative evaluation of the stability of these clusters based on the observation that the Gibbs free energy of formation of the clusters determined from the experimental data shows a strong linear correlation with reciprocal temperature. This model reliably predicts the fugacity of copper in chlorine-bearing water vapour determined from solubility and liquid–vapour partitioning reported in the literature.At temperatures above 450°C, the stoichiometry of the dominant form of the dissolved copper chloride changes from copper monochloride (Cu:Cl=1:1) to copper dichloride (Cu:Cl=1:2) and the hydration numbers of the corresponding clusters are constant for the range of temperatures and pressures investigated. We did not manage to determine the valence state of copper in these species, and therefore interpreted our stability data separately for two alternative sets of hydration clusters, namely; one containing monovalent copper (CuCl:HCl or CuCl2H), and the other containing divalent copper dichloride (CuCl2).The model developed in this study was used to evaluate the solubility of chalcopyrite in HCl-bearing, low density aqueous fluids for temperatures ranging between 300 and 800°C. This evaluation showed that, even for a relatively modest proportion of HCl (0.5vol%), the concentration of copper in low-density fluids in equilibrium with this mineral can reach thousands of ppm at temperatures between 550 and 700°C and fO2 conditions similar to those of porphyry copper ore-forming systems.

Hydrodynamic and absorption studies of carbon dioxide absorption in aqueous amide solutions using a bubble column contactor

The present work analyses the carbon dioxide absorption process in aqueous n-alkylpyrrolidones solutions, from the point of view of hydrodynamic studies as well as mass transfer, using a bubble column contactor. An analysis of the influence of solute concentration and gas flow-rate is complemented by the study of the effect caused by the alkyl group on the hydrodynamics and mass transfer. The presence of this kind of substance produces a decrease in mass transfer rate, but on the basis of interfacial area and mass transfer coefficient values, ethyl-2-pyrrolidine (EP) shows suitable characteristics to replace methyl-2-pyrrolidine (MP) in gas separation processes due to its lower safety problems.