Henry's Law Constants Research Articles

A QSPR Model for Henry's Law Constants of Organic Compounds in Water and Ethanol for Distilled Spirits.

Henry's law describes the vapor-liquid equilibrium for dilute gases dissolved in a liquid solvent phase. Descriptions of vapor-liquid equilibrium allow the design of improved separations in the food and beverage industry. The consumer experience of taste and odor are greatly affected by the liquid and vapor phase behavior of organic compounds. This study presents a machine learning (ML) based model that allows quick, accurate predictions of Henry's law constants (kH) for many common organic compounds. Users input only a Simplified Molecular-Input Line-Entry System (SMILES) string or a common English name, and the model returns Henry's law estimates for compounds in water and ethanol. Training was performed on 5,690 compounds. Training data were gathered from an existing database and were supplemented with quantum mechanical (QM) calculations. An extra trees regression model was generated that predicts kH with a mean absolute error of 1.3 in log space and an R2 of 0.98. The model is applied to common flavor and odor compounds in bourbon whiskey as a test case for food and beverage applications.

Simulation of lithium hydroxide decomposition using deep potential molecular dynamics.

Chemical reactions and vapor-liquid equilibria for molten lithium hydroxide (LiOH) were studied using molecular dynamics simulations and a deep potential (DP) model. The neural network for the model was trained on quantum density functional theory data for a range of conditions. The DP model allows simulations over timescales of hundreds of ns, which provide equilibrium compositions for the systems of interest. Single-phase NPT simulations of the liquid show the decomposition of LiOH into lithium oxide (Li2O) and dissolved water (H2O). These DP results were validated by direct abinitio molecular dynamics simulations that confirmed the accuracy of the model with respect to reaction kinetics and equilibrium properties of the melt. The reactive vapor-liquid behavior of this system was subsequently studied using direct coexistence interfacial DP simulations. Partial pressures of H2O in the vapor are found to be in close agreement with available experimental measurements. By fitting temperature-dependent expressions for the reaction equilibrium and Henry's law constants, the equilibrium composition for any given initial composition and temperature can be quantitatively modeled. For high initial concentrations of Li2O or H2O, mixtures of LiOH + Li2O/H2O are found to undergo phase separation. The present study illustrates how DP-based molecular dynamics simulations can be used for quantitative modeling of multiphase reactive behavior with the accuracy of the underlying abinitio quantum chemical methods.

Interactions between volatile air pollutants and atmospheric water production – Effects of chemical properties, mechanisms, and transfer processes

Regional water scarcity is among the most urgent challenges of global climate change. Atmospheric water harvesting is a promising method to mitigate these challenges, and the atmospheric water generator (AWG) is already an established technology. Although this method can produce over 10,000 L of water per day, the water's quality has not been studied in depth. Air pollutants, especially volatile organic compounds (VOCs), are potential contaminants of water produced from air. We evaluated the chemical and physical parameters of different VOCs that might influence their ability to be transferred from air to AWG water. Our findings strongly suggest that the ability to form hydrogen bonds is a key factor in this transfer. Henry's law constant, polarity, and intrinsic solubility were the main predictors of a VOC's transfer to AWG water. Hence, aliphatic or aromatic compounds (such as benzene or octane) were not found at significant concentrations in AWG water (e.g. above WHO guidelines), whereas ammonia and alcohol compounds were. This should be taken into consideration when analyzing potential contaminants in harvested atmospheric water. The condensation process itself was also found to enhance the transfer of VOCs into water droplets, and higher relative humidity (%RH) also increased VOC transfer. Gas-phase infrared spectrum analysis of VOCs at different %RH revealed possible interactions between water vapor and specific VOCs in the air. However, our main conclusion from this study is that VOC transfer from the air into AWG water occurs predominantly via dissolution in the condensed droplets, and strongly depends on their chemical properties of polarity and hydrogen-bond formation.

Selectivities of Carbon Dioxide over Ethane in Three Methylimidazolium-Based Ionic Liquids: Experimental Data and Modeling.

This work focused on the solubility of ethane in three promising ionic liquids {1-Hexyl-3-methylimidazolium bis(trifluormethylsulfonyl) imide [HMIM][Tf2N], 1-Butyl-3-methyl-imidazolium dimethyl-phosphate [BMIM][DMP], and 1-Propyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl)-imide [PMIM][Tf2N]}. The solubilities were measured at 303.15 K to 343.15 K and pressures up to 1.4 MPa using a gravimetric microbalance. The overall ranking of ethane solubility in the ionic liquids from highest to lowest is the following: [HMIM][Tf2N] > [PMIM][Tf2N] > [BMIM][DMP]. The Peng-Robinson equation of state was used to model the experimental data using three different mixing rules: van der Waals one, van der Waals two, and Wong-Sandler mixing rules combined with the Non-Random Two-Liquid model. The average absolute deviations for the three mixing rules for the ionic liquids at the three temperatures were 4.39, 2.45, and 2.45%, respectively. Henry's Law constants for ethane in [BMIM] [DMP] were the highest (lowest solubility) amongst other ionic liquids studied in this work. The solubility ranking for the 3 ILs was confirmed by calculating their overall polarity parameter (N) using COSMO-RS. The selectivity of CO2 over C2H6 was estimated at three temperatures, and the overall ranking of the selectivity was in the following order: [PMIM][Tf2N] > [BMIM][DMP] > [HMIM][Tf2N] > Selexol. Selexol is an efficient and widely used physical solvent in gas sweetening. It has lower selectivity than the three ionic liquids studied. [PMIM][Tf2N], a promising solvent, has the highest selectivity among the three ILs studied and would, therefore, be the best choice if, in addition to carbon dioxide capture, ethane co-absorption was to be avoided. The enthalpy and entropy of solvation at infinite dilution were also estimated.

Oil sands process-affected water composition effect on Henry's law constants for polycyclic aromatic compounds: Theory and experiment

Oil sands process-affected water (OSPW) is a source of atmospheric emission for polycyclic aromatic compounds (PACs), compounds known to have toxic effects on humans. Estimating emissions and assessing the chemical fate of PACs requires measured or predicted physical-chemical properties such as Henry's law constants (H), that can be used to predict chemical transfer into the atmosphere. OSPW is a complex water-based mixture that is highly variable in composition and nature and contains both organic and inorganic ions. This study uses COSMO-RS solvation theory to estimate and compare Henry's law constants for a set of PACs in both water and theoretically modelled OSPW, to assess the expected deviation that occurs from pure water H values due to the ionic content within OSPW. Experimental measurements of Henry's law constants for PACs in pure water and OSPW using EVA-coated passive dosing and sampler beads were also made in support of our theoretical predictions. For the theory work, OSPW composition data for the Athabasca oil sands in Alberta were used to model a simulated OSPW environment with realistic sodium, chloride, fluoride, sulfate, potassium, bicarbonate, and naphthenic acid concentrations. Theory results indicate that the combined presence of these ions at OSPW concentrations has a negligible effect on H values, causing on average a 3% or 0.014 log unit deviation. By comparison, temperature has a much larger influence on H values, with estimations showing an average 0.20 log unit increase for a 5 °C increase in temperature. The experimental results demonstrate that Henry's law constants can be accurately and precisely measured with this technique in pure water but with less precision in OSPW. Nevertheless, the experimental results support the conclusion that Henry's law constants for OSPW can be accurately estimated assuming a pure water phase.

Vapor‐liquid interfacial properties of binary mixtures from molecular simulation and density gradient theory

AbstractProperties of the vapor‐liquid interface of 16 binary mixtures were studied using molecular dynamics simulations and density gradient theory in combination with the PCP‐SAFT equation of state. All binary combinations of the heavy‐boiling components (cyclohexane, toluene, acetone, and carbon tetrachloride) with the light‐boiling components (methane, carbon dioxide, hydrogen chloride, and nitrogen) were investigated at 0.7 times the critical temperature of the heavy‐boiling component in the whole composition range. Data on the surface tension, the enrichment, the relative adsorption, and the interfacial thickness, as well as for the vapor‐liquid equilibrium and Henry's law constant are reported. The binary interaction parameters were fitted to experimental data in a consistent way for all systems and both methods. Overall, the results from both methods agree well for all investigated properties. The interfacial properties of the different studied systems differ strongly. We show that these differences are directly related to the underlying phase equilibrium behavior.

Carbon Dioxide Solubility in Three Bis Tri (Fluromethylsulfonyl) Imide-Based Ionic Liquids.

This study delves into the necessity of mitigating carbon dioxide (CO2) emissions, focusing on effective capture methods to combat global warming by investigating the solubility of CO2 in three ionic liquids (ILs), 1-Decyl-3-MethylimidazoliumBis (Trifluromethylsulfonyl Imide) [IL1], 1-Hexadecyl-3-Methyl imidazoliumBis (Trifluromethylsulfonyl Imide) [IL2] and Triethytetradecyl Ammonium Bis (Trifluromethylsulfonyl Imide) [IL3]. Solubility experiments were conducted at (30, 50 and 70) °C with pressures up to 1.5 MPa. The research shows [IL2] as the superior candidate for CO2 capture, with its longer alkyl chain, and is confirmed by its lower Henry's Law constant. Utilizing the Peng Robinson equation of state, the study correlates well with the solubility measurements using three mixing rules. The study reveals promising results for IL1, IL2 and IL3 surpassing all other published ionic liquids including Selexol/Genesorb 1753, except for 1-Methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)imide. Insights into the enthalpy and entropy of absorption underscore the significant impact of IL structure on CO2 solubility, emphasizing the potential of tailored ILs for advanced carbon capture strategies. In summary, this research highlights [IL2] as the optimal choice for CO2 capture, offering valuable contributions to the ongoing efforts in combating climate change.

Evaluation of the vacuum effect on headspace solid-phase microextraction of volatile organic compounds from aqueous samples using finite element analysis modeling

Headspace solid-phase microextraction (HSSPME) of volatile organic compounds (VOCs) from aqueous samples under vacuum conditions (Vac-HSSPME) allows increasing extraction rates and decreasing detection limits compared to HSSPME under atmospheric pressure. The positive effect of the vacuum on HSSPME of an analyte can be quickly estimated using its Henry's law constant (HLC). According to the two-layer model of evaporation, substantial positive effect of the vacuum can be expected for analytes with HLC lower than 1.6·10−4 atm m3 mol−1 (0.0065 at 25 °C), but the model does not consider possible effects of other important extraction parameters. This research was aimed at the evaluation of the possible effect of vacuum on the equilibration time and extracted amounts of analytes with various HLC and fiber coating-headspace distribution constants (Kfh) using the computational model recently developed in COMSOL Multiphysics® software. It has been proven that HSSPME under vacuum provides faster equilibration of VOCs with all studied Kfh and HLC. The largest vacuum effect on the extracted analyte amount was 3.9–4.0 times at logKfh = 6 and HLC = 10−6–10−3. The substantial (≥1.5 times) vacuum impact should not be expected for analytes with logKfh < 5 for 15-min extraction and logKfh < 5.5 for 30-min extraction. The vacuum impact should be more pronounced when using fiber coatings with a stronger affinity to analytes. The obtained results will be useful for the development of new methods based on Vac-HSSPME and evaluation whether HSSPME is reasonable to conduct under vacuum conditions for faster equilibration and/or lower detection limits.

PACMAN: A Robust Partial Atomic Charge Predicter for Nanoporous Materials Based on Crystal Graph Convolution Networks.

We report a fast and easy method (PACMAN) to assign partial atomic charges on metal-organic framework (MOF) and covalent-organic framework (COF) crystal structures based on graph convolution networks (GCNs) trained on >1.8 million high-fidelity partial atomic charge data obtained from the Quantum Metal-Organic Framework (QMOF) database. The developed model shows outstanding performance, achieving a mean absolute error (MAE) of 0.0055 e (test set performance) while maintaining consistency with DDEC6, Bader, and CM5 charges across diverse chemistry and topologies of MOFs and COFs. We find that the new method accurately assigns partial atomic charges for ion-containing nanoporous materials, which has not been possible in previous machine learning (ML) models. Grand canonical Monte Carlo (GCMC) simulation results for CO2 and N2 uptakes and the Widom particle insertion calculation for Henry's law constant of water results based on PACMAN and the original DDEC6 charges show excellent agreements compared to other ML models reported in the literature. The runtime analysis of the new method demonstrates that the partial atomic charges of MOF and COF structures with up to 500 atoms can be obtained in less than 10 s. An easy-to-use web interface has been developed to facilitate the adoption of the developed model.

CO2 absorption using two morpholine protic ionic liquids: measurement, model, and quantum chemical calculation

Two kinds of protic ionic liquids, N-methylmorpholinium formate ([NMMH][For]) and N-ethylmorpholinium formate ([NEMH][For]), were synthesized by the acid-base neutralization method. The solubility of carbon dioxide (CO2) in the two ionic liquids was measured at temperatures of 298.15 to 338.15 K and pressures of up to 900 kPa. The solubility increases linearly with pressure, indicating that CO2 is physically absorbed in ionic liquids. The solubility of CO2 in [NEMH][For] is higher than that of [NMMH][For]. Absorption behavior was investigated by thermodynamic properties, such as the Henry's law constant, partial molar Gibbs free energy, partial molar enthalpy, and partial molar entropy. The Pitzer's model and the Soave-Redlich-Kwong (SRK) cubic equation of state were used to fit the solubility data, respectively. The Pitzer's model is found to have better prediction accuracy. The interaction of two protic ionic liquids with CO2 was analyzed using quantum chemistry. The molecular mechanism of CO2 absorption by two protic ionic liquids was explained from the microscopic point of view. CO2 + [NEMH][For] has more hydrogen bonds and a higher interaction energy. The cation–anion interaction of [NEMH][For] diminishes in the presence of CO2, resulting in an increase in the cation–anion distance. These factors result in higher solubility of CO2 in [NEMH][For].

Bacteria in clouds biodegrade atmospheric formic and acetic acids

Abstract. Formic and acetic acids are major organic species in cloud water and affect precipitation acidity. In atmospheric models, their losses are limited to chemical oxidation in the gas and aqueous phases and deposition processes. Previous lab studies suggest that these acids can be efficiently biodegraded in water by atmospherically relevant bacteria. However, the importance of biodegradation as a loss process in the atmospheric multiphase system has not been fully assessed. We implemented biodegradation as a sink of formic and acetic acids in a detailed atmospheric multiphase chemistry model. In our model, biodegradation is considered in 0.1 % of cloud droplets according to atmospheric bacteria concentrations of 0.1 cm−3. We predict that up to 20 ppt h−1 formic acid and 5 ppt h−1 acetic acid are biodegraded. This translates into a concentration change of 20 % and 3 % in addition to that caused by chemical losses. Our sensitivity studies suggest that acetic acid is most efficiently biodegraded at pH &gt; 5, whereas biodegradation is least efficient for formic acid under such conditions. This trend can be explained by the fact that formic acid partitions more efficiently into the aqueous phase due to its higher Henry's law constant (KH,eff(HCOOH)=2×105 M atm−1 vs. KH,eff(CH3COOH)=3×104 M atm−1 at pH = 5). Therefore, under such conditions, formic acid evaporates less efficiently from bacteria-free droplets, resulting in less formic acid in the gas phase for dissolution bacteria-containing droplets to replenish biodegraded acid. Our analysis demonstrates that previous estimates of the importance of atmospheric biodegradation were often biased high as they did not correctly account for such uptake limitation in bacteria-containing droplets. The results suggest that, under specific conditions, biological processes can significantly affect atmospheric composition and concentrations in particular volatile, moderately soluble organics.

Online headspace monitoring of volatile organic compounds using proton transfer reaction-mass spectrometry: Application to the multiphase atmospheric fate of 2,4-hexadienedial

Chemical processes in clouds have been suggested to contribute significantly to the mass of organic aerosol particles in the atmosphere. Experimental and theoretical evidence suggest that organic mass production in clouds can be substantial and depends on the concentration of organic precursor compounds available in the gas phase. The present study aims at studying the aqueous phase reactivity of one of these overlooked precursors, i.e. 2,4-hexadienedial, an important and toxic intermediate in the atmospheric oxidation of aromatic species. Cautious synthesis and purification of 2,4-hexadienedial was performed. Its effective Henry's law constant was measured using a new simple and fast method based on online flow-injection analysis. The reactivity of 2,4-hexadienedial in the aqueous phase relevant to atmospheric conditions was studied, including hydrate formation, photolysis, ∙OH- and SO4∙--oxidation as well as reaction with NH3. The results revealed a low hydration constant compared to other dicarbonyls (Khyd1 = 7 × 10−2) and no dihydrate formation, indicating in an intermediate solubility (KH = 1.0 × 104 M atm−1) and high absorption cross sections (σ278nm > 10−16 cm2 molecule−1). Compared to its gas phase photolysis, its aqueous phase photolysis showed low quantum yields (Φ290–380nm = 0.9 %), and a significant red shift of the absorbance maximum, leading to a fast aqueous photolysis kinetics (Jaq,atm = 8.7 × 10−5 s−1) under atmospheric solar radiation, but no triplet state formation was detected. Radical oxidation experiments revealed extremely rapid oxidation kinetics (k∙OH = 1.10 × 1010 M−1 s−1 and kSO4∙- = 1.4 × 109 M−1 s−1) driven by fast addition of the radicals to the unsaturated bonds. In contrast, the reaction with aqueous NH3 (kNH3 = 2.6 × 10−3 M−1 s−1) was found slower than glyoxal and 2-butenedial, likely due to the hyperconjugation of 2,4-hexadienedial. Using these new data complemented with assumed aqueous phase kinetics (for NO3, 3C* and 1O2 reactions) and previous gas-phase kinetic ones, the multiphase atmospheric fate of 2,4-hexadienedial was established under atmospheric conditions reported from previous field measurements and models. The results revealed a short day lifetime (∼1 h) and a long night lifetime (>12 h). It was shown that daytime atmospheric chemistry of 2,4-hexadienedial can be influenced by aqueous-phase reactivity during cloud events, up to ∼50 % under thick cloud conditions (Liquid Water Content >2000 g/m3), indicating that even a compound of intermediate solubility can be strongly affected by condensed-phase reactivity. Besides its fast aqueous phase reactivity towards ∙OH and photolysis, its daytime condensed-phase reactivity may be driven by reactions with dissolved triplet states (3C*), up to 35 %, highlighting the need to study further the kinetics, the nature and concentrations of dissolved 3C* under various atmospheric conditions. In addition, the molecular properties and atmospheric behavior of 2,4-hexadienedial were found different from those of glyoxal and 2-butenedial, highlighting the need for detailed atmospheric reactivity studies of polyfunctional compounds, in particular unsaturated compounds.

Investigation of effective CO2 capture by ternary deep eutectic solvents based on superbase

The absorption and separation of CO2 is one of the main strategies to reduce carbon emissions and mitigate global climate change. In this context, a series of ternary superbase/betaine-based deep eutectic solvents (DESs) were synthesized to capture CO2, and their density, viscosity and thermal stability were investigated. The effects of temperature, pressure, different hydrogen bond donors (HBDs) and alkalinity of the superbase on their CO2 affinity were evaluated by the isovolumetric saturation method. The uptake of CO2 by the DES synthesized from betaine, 1,2-propanediol and 1,8-diazabicyclo(5.4.0)undec-7-ene reached a maximum of 1.5071 mol·kg−1 at 303.15 K and a pressure of 0.187 MPa. The simultaneous chemical and physical adsorption of CO2 by the ternary DESs was verified by FTIR spectroscopy, and the absorption mechanism was also proposed. The reaction equilibrium thermodynamic model (RETM) was improved to obtain the “Active DES” model, which was correlated with the experimentally determined CO2 solubility. The reaction equilibrium constants and Henry's law constants were obtained for each ternary system. The ternary superbase/betaine DESs proposed in this paper are green, economical and high-performance absorbers for capturing CO2.

Evaluation of GC-EI&CI-TOFMS for Nontarget Analysis of Industrial Wastewater Using Hydrophilic-Lipophilic-Balanced SPME.

The evaluation of nontarget analysis (NTA) techniques for the monitoring of wastewater is important as wastewater is an anthropogenic pollution source for aquatic ecosystems and a threat to human and environmental health. This study presents the proof-of-concept NTA of industrial wastewater samples. A prototype hydrophilic-lipophilic-balanced (HLB) SPME and gas chromatography interfaced with time-of-flight high-resolution mass spectrometry (GC-TOFMS) with electron ionization (EI) and chemical ionization (CI) in parallel are employed. The HLB-SPME consists of a poly(divinylbenzene-co-N-vinylpyrrolidone) structure, allowing the extraction of hydrophilic as well as lipophilic substances. As the combination of parallel CI and EI data provides a comprehensive data set as a unique feature, this study is strongly focused on the compound identification procedure and confidence reporting of exemplary substances. Furthermore, the use of three different CI reagent ions, including [N2H]+/[N4H]+, [H3O]+, and [NH4]+, enables a broad range of analytes to be ionized in terms of selectivity and softness. The complementary information provided by EI and CI data allows a level 3 identification or higher in 69% of cases. The polarity coverage based on the physicochemical properties of the analytes (such as volatility, water solubility, hydrophilicity, and lipophilicity) was visualized by using Henry's law and octanol-water partitioning constants. In conclusion, the presented approach is shown to be valuable for water analysis and allows enhanced and accelerated compound identification compared to utilizing only one type of ionization.

CO2 solubility and absorption rate analysis of a mixed poly(oxymethylene) dimethyl ethers (PODE3–5) solution

Efficient and economical carbon capture is critical to counteract the diverse problems of global warming. In this work, the solubility of carbon dioxide (CO2) in different poly(oxymethylene) dimethyl ethers (PODE) solutions was experimentally investigated at temperatures from 278.15 to 308.15 K and pressures up to 1.2 MPa. The Henry's law constants of CO2 in the PODE system were determined and compared with other types of physical absorbents, which revealed PODE3–5 has great CO2 absorption ability in terms of molar and mass fraction. Meanwhile, the initial absorption rate of the physical absorption process of PODE3–5 was calculated and compared with commercially available absorbents using a gas absorption rate relationship. It was shown that the absorption rate of PODE3–5 in the CO2 absorption process is faster than that of other commercial absorbents. The CO2 solubility data of PODE3–5 were also correlated using the Jou-Mather model and the perturbed-chain statistical association fluid theory (PC-SAFT) equation of state model, and the recycling performance of the PODE3–5 absorbent was tested.

Global environmental and toxicological impacts of polybrominated diphenyl ethers versus organophosphate esters: A comparative analysis and regrettable substitution dilemma

The prevalence of organophosphate esters (OPEs) in the global environment is increasing, which aligns with the decline in the usage of polybrominated diphenyl ethers (PBDEs). PBDEs, a category of flame retardants, were banned and classified as persistent organic pollutants (POPs) through the Stockholm Convention due to their toxic and persistent properties. Despite a lack of comprehensive understanding of their ecological and health consequences, OPEs were adopted as replacements for PBDEs. This research aims to offer a comparative assessment of PBDEs and OPEs in various domains, specifically focusing on their persistence, bioaccumulation, and toxicity (PBT) properties. This study explored physicochemical properties (such as molecular weight, octanol-water partition coefficient, octanol-air partition coefficient, Henry's law constant, and vapor pressures), environmental behaviors, global concentrations in environmental matrices (air, water, and soil), toxicities, bioaccumulation, and trophic transfer mechanisms of both groups of compounds. Based on the comparison and analysis of environmental and toxicological data, we evaluate whether OPEs represent another instance of regrettable substitution and global contamination as much as PBDEs. Our findings indicate that the physical and chemical characteristics, environmental behaviors, and global concentrations of PBDEs and OPEs, are similar and overlap in many instances. Notably, OPE concentrations have even surged by orders of several magnitude compared to PBDEs in certain pristine regions like the Arctic and Antarctic, implying long-range transport. In many instances, air and water concentrations of OPEs have been increased than PBDEs. While the bioaccumulation factors (BAFs) of PBDEs (ranging from 4.8 to 7.5) are slightly elevated compared to OPEs (−0.5 to 5.36) in aquatic environments, both groups of compounds exhibit BAF values beyond the threshold of 5000 L/kg (log10 BAF > 3.7). Similarly, the trophic magnification factors (TMFs) for PBDEs (ranging from 0.39 to 4.44) slightly surpass those for OPEs (ranging from 1.06 to 3.5) in all cases. Metabolic biotransformation rates (LogKM) and hydrophobicity are potentially major factors deciding their trophic magnification potential. However, many compounds of PBDEs and OPEs show TMF values higher than 1, indicating biomagnification potential. Collectively, all data suggest that PBDEs and OPEs have the potential to bioaccumulate and transfer through the food chain. OPEs and PBDEs present a myriad of toxicity endpoints, with notable overlaps encompassing reproductive issues, oxidative stress, developmental defects, liver dysfunction, DNA damage, neurological toxicity, reproductive anomalies, carcinogenic effects, and behavior changes. Based on our investigation and comparative analysis, we conclude that substituting PBDEs with OPEs is regrettable based on PBT properties, underscoring the urgency for policy reforms and effective management strategies. Addressing this predicament before an exacerbation of global contamination is imperative.

Prediction of pair interactions in mixtures by matrix completion.

Molecular simulations enable the prediction of physicochemical properties of mixtures based on pair-interaction models of the pure components and combining rules to describe the unlike interactions. However, if no adjustment to experimental data is made, the existing combining rules often do not yield sufficiently accurate predictions of mixture data. To address this problem, adjustable binary parameters ξij describing the pair interactions in mixtures (i + j) are used. In this work, we present the first method for predicting ξij for unstudied mixtures based on a matrix completion method (MCM) from machine learning (ML). Considering molecular simulations of Henry's law constants as an example, we demonstrate that ξij for unstudied mixtures can be predicted with high accuracy. Using the predicted ξij significantly increases the accuracy of the Henry's law constant predictions compared to using the default ξij = 1. Our approach is generic and can be transferred to molecular simulations of other mixture properties and even to combining rules in equations of state, granting predictive access to the description of unlike intermolecular interactions.

Size-dependent acidity of aqueous nano-aerosols.

Understanding the accurate acidity of nano-aerosols is important for the research on atmospheric chemistry. Herein, we propose the contributions from both the aerosol size and multiphase buffer effect to the steady-state acidity of nano-aerosols at a constant aerosol water content (AWC) through molecular simulations. As increasing of the aerosol size, the solvation free energy (SFE, ΔGs) became more negative (decreasing by 3-130 kcal mol-1 for different types of species) and Henry's law constant (H) apparently increased (from e6 to e16 mol m-3 Pa-1) in the nano-aerosols compared to that in bulk solutions. The lower SFE led to lower solute pKa and pKb values; thus, the acidity of HSO4- and HNO3 and the alkalinity of NH3 showed positive relations with the aerosol size. The lower H also increased the pKa of gaseous solutes, leading to a decrease in the acidity of HNO3 and a shift from alkaline to acidic for the NH4+/NH3 buffer pair in the nano-aerosols. The present study revealed the relationship between aerosol acidity and solvent size from a microscopic perspective. Specifically, the acidity of aerosols containing HSO4-/SO42- and HNO3/NO3- decreased with an increase in their radii, whereas aerosols containing NH4+/NH3 exhibited an opposite trend. This phenomenon can be attributed to the disappearance of the interfacial effect with an increase in the size of the aerosols. The above conclusions are of great significance for studying the pH-dependent multi-phase chemical processes in aerosols.

Air‐Sea Gas Exchange and Its Potential Influence on the Regional Fate of Polycyclic Aromatic Hydrocarbons in the East China Marginal Sea

AbstractTo investigate the air‐sea gas exchange and its potential influence on the regional fate of polycyclic aromatic hydrocarbons (PAHs) in the East China Marginal Seas (ECMS), which consist of the East China Sea (ECS) and Yellow Sea (YS), we collected air and surface seawater samples of this area in the summer 2018 and winter 2019, respectively. Generally, PAHs underwent a strong volatilization process in the ECMS in both summer and winter. Good correlations between wind speed and the magnitude of air‐sea gas exchange were found for low molecular weight PAHs, suggesting the rate of their air‐sea gas exchange was influenced by the static stability of overlying atmosphere. However, such an influence for high molecular weight PAHs was constrained by their low Henry's law constant. Dissolved concentration of PAHs in surface seawater was another key factor regulating their air‐sea gas exchange, which not only influenced the rate of air‐sea gas exchange but also was involved in the exchange direction. Higher air‐sea gas exchange fluxes of PAHs in winter were attributed to their increasing dissolved concentrations in seawater during this season. A mass conservation analysis revealed a huge volatilization loss of PAHs from seawater to atmosphere, suggesting air‐sea gas exchange might be a key process to modulate the distribution and occurrence of PAHs in the ECS and YS. Such a loss of PAHs in seawater might be compensated by the sediment resuspension, which implied that the sedimentary deposit could serve as a secondary source of PAHs in seawater and overlying atmosphere.

Analytical model for assessing mass transfer of VOC in liquid desiccant dehumidifier: A broad-range response to Henry's law constant

Removing indoor volatile organic compounds (VOCs) is crucial for human health. Liquid dehumidification is considered as a promising way for VOC removal. The methods for predicting its performance are limited to numerical simulations or experiments, which are time-consuming, expensive, effort-intensive, and unintuitive. Although analytical method is advantageous for resolving these problems, existing analytical models focus primarily on single-VOC benzene, neglecting the effect of Henry's law constant (HLC) and leading to inaccurate predictions for other VOCs. In this study, considering the effect of HLC, a new analytical model with a broad-range response to HLC is proposed. Moreover, a correction method is proposed to enhance the application range and precision of analytical model. Thus, the definition domain of the proposed model is segmented into various zones, considering accuracy and key parameters. The validity of the proposed model is demonstrated under two conditions: HLCs are on the orders of 10–4 and 10–5. Results show that the proposed analytical solutions show good agreement with published data with a deviation within ±20%. Thus, the proposed model exhibits a broad-range response to HLC, resolving the limitation of existing analytical solution. This study provides an analytical method for assessing VOC removal using liquid dehumidifier.