Concentration In Aqueous Phase Research Articles

Methylmercury sorption onto engineered materials.

Four commercially available sorbents (BioChar (BC), ThiolSAMMS® (TS), SediMite (SM), and Organoclay™ PM-199 (OC-199)) were tested for their ability to sorb methylmercury (MeHg) and MeHg complexed with dissolved organic matter (DOM). Testing sorption behavior with DOM is more representative of the environmental conditions and mercury speciation expected during in-situ remediation efforts. Isotherms were fit using a robust, iterative re-weighting scheme. This fitting approach improves upon the traditionally used indirect sorption method by removing the dependence between aqueous and solid phase concentrations in isotherm fitting. Developed isotherms show that without DOM, BC, TS, and SM adsorbed similar amounts of MeHg while OC-199 sorbed substantially less MeHg. Below an equilibrium concentration of 5.6 ng L-1 BC was the best performing sorbent, between 5.6 and 20.9 ng L-1 SM sorbed the most MeHg, and above an equilibrium concentration of 20.9 ng L-1 TS outperformed the other sorbents. BC and OC-199 showed indication of MeHg sorption saturation over the tested concentration range of 3.5-680 ng L-1. With DOM, SM outperformed the other sorbents at equilibrium concentrations less than 0.98 ng L-1 and TS was the superior MeHg:DOM sorbent at higher concentrations. MeHg:DOM sorption was controlled by DOM-sorbent interactions. DOM decreased MeHg sorption onto BC and SM whereas TS exhibited similar sorption with and without DOM. OC-199 had slightly higher MeHg uptake with DOM. East Fork Poplar Creek (EFPC), an industrially Hg contaminated site, was used as a case study example to build a relationship between aqueous and fish MeHg concentrations and subsequently compare the cost of sorbent materials required to meet regulatory objectives. For this case study, SM provided the most cost-effective sorbent option for in-situ remediation efforts to reduce aqueous MeHg concentrations.

Extraction of Rare Earth Elements from Hydrochloric Acid Solutions with Carbamoylmethylphosphine Oxides in the Presence of Quaternary Ammonium Dinonylnaphthalenesulfonates

Interphase distribution of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y between aqueous HCl solutions and solutions of carbamoylmethylphosphine oxides in the presence of binary extractants, quaternary ammonium dinonylnaphthalenesulfonates, has been studied. It has been shown that the efficiency of extraction of rare earth elements(III) (REE) with carbamoylmethylphosphine oxides increases considerably in the presence of binary extractant in organic phase. The stoichiometry of extracted complexes has been determined, effect of cation nature of the binary extractant, organic solvent, structure of carbamoylmethylphosphine oxides, and HCl concentration in aqueous phase on efficiency of REE(III) recovery into organic phase has been considered.

The Synthesis and Investigation of Liquid-Liquid Extraction Capability of N-Diphenylphosphino-N-ethylaniline and Its Chalcogenide Derivatives

The aminophosphine ligand was synthesized by the reaction of N-ethylaniline with chlorodiphenylphosphine in the presence of triethylamine at low temperature. Oxidation of the ligand with elemental sulfur or selenium afforded the corresponding aminophosphine sulfide and selenide. The compounds were characterized by elemental analyses, IR, 1H and 31P NMR. N-diphenylphosphino-N-ethylaniline and its chalcogen derivatives were used as ligands in solvent extraction of metal picrates such as Cd2+ and Ni2+ from the aqueous to the organic phase. Influences of parameters such as pH of the aqueous phase, solvent, extraction time, and extradant concentration were investigated to determine the extraction ability of ligands for metal ions. Results of the experiments showed that an extractability of 95.5 and 97.8%, respectively for Ni2+, and Cd2+ at pH 2 could be achieved.

Evaluation of laminar flow of surfactant-stabilized bitumen-in-water emulsion in pipe using computational fluid dynamics: Effects of water content and salinity

Laminar flow of oil-in-water (O/W) emulsion in a horizontal pipe has been simulated to quantify the effect of salinity of aqueous phase and water content on flow characteristics using computational fluid dynamics (CFD). Bitumen was dispersed in aqueous solution containing surfactant at different NaCl concentrations and water contents. Rheological parameter was obtained from the viscosity-shear rate profiles of the fluid. Numerical modeling and simulation was performed using a finite element simulation software. The case was simplified by considering the O/W emulsion as a stable, pseudo-homogeneous (single-phase) fluid within the conditions investigated. At flow reference temperature, Tref = 30 °C, the pressure drop obtained from emulsion with 30% water content was 931 Pa, compared to 84.6 Pa which was obtained from 50% water content (i.e. reference fluid without NaCl). In addition, the pressure drop of 239 Pa, 142 Pa, 124 Pa, and 82.9 Pa was obtained from O/W emulsion samples containing 70000 ppm, 40000 ppm, 20000 ppm, and 10000 ppm salinity in the aqueous phase, respectively. Furthermore, the maximum dynamic viscosity imposed by the fluid, was calculated as ≈81000 cP for the sample containing 30% water content compared to ≈14000 cP from the reference fluid. The dynamic viscosity obtained from 70000 ppm salinity content was ≈34000 cP compared to ≈20000 cP, ≈16000 cP, and ≈13000 cP calculated for 40000 ppm, 20000 ppm, and 10000 ppm salinity, respectively. Moreover, large reduction in pressure drop (99%) and dynamic viscosity (60–90%), regardless of the water content and salinity were obtained from the simulation.

IN VIVO CHARACTERIZATION OF LESS PAINFUL PROPOFOL NANOEMULSION USING PALM OIL FOR INTRAVENOUS DRUG DELIVERY

Objective: The objective of present work was to evaluate the effectiveness of propofol in nanoemulsion based palm oil that called as NEMS™, which was a choice of anesthetic drug to induce and maintenance general anesthesia to reduce pain on injection activity and also to evaluate the in vivo characterization of propofol in NEMS™.
 Methods: Preparation of propofol nanoemulsion using NEMS™ technology has been performed for propofol 1% in NEMS™ (P1%), and propofol 2% in NEMS™ (P2%). Determination of free propofol concentration in aqueous phase was conducted using HPLC and rat paw lick test was evaluated as in vivo test to assay the intensity of pain on injection site. The sleep recovery test was conducted to evaluate the pharmacological effect and erythrocyte hemolysis test also conducted to ensure the safety of propofol in NEMS™. All of the test results were compared with Diprivan®1% as a positive standard.
 Results: The contents of free propofol in formulation P1% and Diprivan®1% in aqueous-phase were 6.20±0.03 µg/ml and 15.02±0.33 µg/ml, respectively (*P<0.05). The rat paw lick test showed that the formulation P1% was significantly (*P<0.05) less painful when compared to Diprivan®1%. There were no significant differences in pharmacological effect for all of the formulations (*P>0.05). The erythrocyte haemolysis test show that all formulation still safe for our blood.
 Conclusion: Palm oil can be used as a carrier for propofol and it was successfully reduced the free propofol contents and the intensity of pain on injection site in rats.

Rheology and structure of oleogelled water-in-oil emulsions containing dispersed aqueous droplets as inactive fillers

The effect of dispersed aqueous droplets on the structure and rheology of rice bran wax (RBX) oleogels was investigated. Water-in-oil (W/O) emulsions containing up to 50 wt% water dispersed in canola oil were generated with polyglycerol polyricinoleate (PGPR) as the oil-soluble surfactant. The presence of both the RBX and PGPR resulted in oleogelled W/O emulsions stable against coalescence and phase separation for at least 28 days. The key contributor to emulsion structure and stability was the wax crystal network itself as the droplets behaved as an inactive filler. The oleogelled emulsions demonstrated structural weakening with increasing water content in terms of rigidity and thixotropic behaviour, both of which were attributed to the decrease in RBX content. Importantly, emulsion elastic modulus was near identical to its corresponding control where the dispersed phase was replaced by an equivalent wt% of continuous phase oil instead. Overall, this study demonstrated that even with dispersed droplets behaving as an inactive filler, it is possible to generate kinetically-stable oleogelled W/O emulsions with a high aqueous phase content.

Chiral extraction of amino acid and mandelic acid enantiomers using chiral diphosphine ligands with tunable dihedral angles

Chiral diphosphine ligands with different dihedral angles (CnTunaPhos, n = 1–6) were synthesized and adopted as chiral selectors to recognize amino acids and mandelic acid. The influences of dihedral angles, organic solvents, pH of aqueous phase and chiral extractant concentration on enantioselectivities (α) were investigated. The results revealed that CnTunaPhos is more efficiency than MeO-BIPHEP for its rigidity in stereochemistry. The enantioselectivities of chiral diphosphine ligands can be improved by regulating dihedral angles. The most efficient CnTunaPhos for Phenylalanine (Phe), homophenylalanine (Hphe), 4-nitro-phenylalanine (Nphe) , 3-chloro-phenylglycine (Cpheg), mandelic acid (MA) and 2-Cl-mandelic acid (CMA) were C6TunaPhos-Cu, C6TunaPhos-Cu, C4TunaPhos-Pd, C5TunaPhos-Cu, C4TunaPhos-Cu and C2TunaPhos-Cu, respectively. In addition, the possible recognition mechanisms of CnTunaPhos-metal complexes toward amino acid and mandelic acid were discussed. The results of our work may provide important reference for the design of efficient chiral extractants.

A novel electro-catalytic membrane contactor for improving the efficiency of ozone on wastewater treatment

A novel electro-catalytic membrane contactor was designed to break the two constrains in O3 wastewater treatment technology simultaneously: the mass transfer of O3-water and the decomposition rate of O3 into OH. In the electro-catalytic membrane contact ozonation (ECMCO) process, O2 and O3, in the gas chamber, diffuse through the hydrophobic membrane into the water phase; O2 is electro-reduced to H2O2 that catalyzes O3 producing OH to degrade organic compounds rapidly. The removal rate of nitrobenzene (NB) was significantly improved by the combination of membrane contactor and electro-catalytic process. The removal rates of NB in 120 min were 85%, 55% and 23% for ECMCO, membrane contact ozonation and electrolysis, respectively. O3 concentration and current density had positive effects on the removal of NB, which was related to the accumulated H2O2 concentration in aqueous phase. Gas flow had slight positive effects on NB removal when it was lower than 50 mL/min. The pH of the feed may affect the production and the form of H2O2 and hence the removal of NB. The highest removal rate in 120 min was up to 95.7% at the initial pH of 4.5. Mass transfer and electrolysis are synthetic in ECMCO process. On one hand, the mass transfer of O3 increased by 2 times due to the electro-catalytic production of H2O2. On the other hand, the existence of O3 promoted the production of H2O2. ECMCO has great potential on promoting mass transfer and decomposition of O3 into OH for the industrial application of O3.

In Situ Monitoring and Kinetic Analysis of the Extraction of Nitric Acid by Tributyl Phosphate in N-Dodecane Using Raman Spectroscopy

ABSTRACTUnderstanding the fundamental rates of transfer and complex formation is crucial in maintaining optimal efficiency and effectivity in solvent extraction. Methodologies to analyze solvent extraction systems are lacking in that they are commonly performed off-line in subsequent experiments. Thus, a method to proficiently investigate solvent extraction systems in a Lewis cell using in situ Raman spectroscopy paired with chemometric modeling has been developed to allow for on-line analysis and monitoring. Forward and reverse interfacial transfer coefficients for the extraction of nitric acid by tributyl phosphate, a process crucial to used nuclear fuel reprocessing, were measured by spectroscopic monitoring of both phases simultaneously in a two-phase solvent extraction system. Concentration data was derived from the chemometric modeling using Raman spectra. The concentration data was fit to a nonlinear least squares regression model to allow for the calculation of the transfer coefficients in the system. The reverse interfacial transfer coefficient, kr, was determined along with the parameter 95% confidence intervals and 95% prediction intervals. The forward interfacial transfer coefficient, kf, was then back calculated from kr and the aqueous phase and organic phase equilibrium concentrations. The average calculated values of kr and kf were 2.56 (± 0.50) × 10−5 m s−1 and 4.75 (± 1.13) × 10−6 m s−1, respectively. The information obtained regarding solvent extraction parameters and transfer can be applied in the study of systems of higher complexity, involving complex formation and their transfer across a liquid:liquid interface.

Calibration parameters for the passive sampling of organic UV filters by silicone; diffusion coefficients and silicone–water partition coefficients

In recent years, organic ultraviolet filters (UVFs) received considerable attention as a group of emerging contaminants, including in Australia where the use of UVFs is particularly relevant. Passive sampling using polymers has become widely used for routine monitoring of chemicals in the aquatic environment. Application of passive samplers for monitoring chemicals in the water relies on calibration data such as chemical's polymer-water partition coefficient (Kpw) and diffusion coefficients in the sampling material (Dp), for understanding uptake and kinetic limitations. In the present study, Kpw and Dp for nine UVFs were estimated. Kpw values were determined in different water – polymer partition experiments where (1) a given mass of chemicals was dosed into the water and (2) into the polymer. Diffusion coefficients were determined using the stacking method. The estimated log Kpw and log Dp ranged from 2.9 to 6.4 L kg−1 and -11.1 to −10.5 m2s-1, respectively. The sufficient high Dp allows application of kinetic models that only consider water boundary-controlled uptake for converting silicone sampler uptake into an aqueous phase concentration using the presented Kpw.

Inactivation Effect of Colletotrichum Gloeosporioides by Long-Lived Chemical Species Using Atmospheric-Pressure Corona Plasma-Activated Water

In this paper, atmospheric-pressure air and oxygen corona plasma jets under water surface have been used to generate plasma-activated water (PAW) to inactivate colletotrichum gloeosporioides ( C. gloeosporioides ) suspension. The atmospheric-pressure plasma jets in the water were characterized by measuring: 1) the electrical and optical properties for evaluating the plasma efficiency and 2) the physicochemical properties of PAW, including pH value, oxidation-reduction potential value, and the concentration of hydrogen peroxide, nitrite, and ozone. The aim of this paper is to investigate the effects of long-lived reactive oxygen and nitrogen species (RONS) and environmental factor (acidity) in PAW on fungicidal property. The results of antifungal activity show that the inactivation rate of C. gloeosporioides is higher using air-PAW than oxygen-PAW, and increases with increasing reaction time when preparation time of PAW is fixed as 30 min. This correlates well with measurements of the aqueous-phase long-lived RONS concentration such as nitrate and ozone, suggesting these species play crucial roles in the inactivation process.

Optimization of infrared-assisted extraction of bioactive lactones from Saussurea lappa L. and their effects against gestational diabetes

Background: Saussurea lappa (S. lappa, Asteraceae) have immunomodulatory effects and used in the management of many metabolic disorders. Gestational diabetes is one of the metabolic disorders affecting globally one in seven pregnant women. Objectives: The aim of the current study is to optimize an infrared-assisted extraction (IR-AE) method for S. lappa bioactive constituents, phytochemically investigate its content, isolate its most active constituent, and to assess their biological effects against gestational diabetes. Materials and Methods: To optimize IR-AE conditions, four main factors were studied including solvent concentration, extraction time, powder size, and IR power in the yielded extract (SL-IR). Reversed-phase high-performance liquid chromatography coupled with bio-guided fractionation and isolation procedures using 1H and 13C NMR method were utilized. Solid–liquid (SL-SLE) and ultrasound (SL-US) extraction methods were also done. Results: The optimal IR-AE extraction conditions were found to be 20% aqueous phase concentration, 60-min extraction time, 70 mesh powder size, and 70 W IR power. Phytochemically, four major lactones were identified, including costunolide, dehydrocostuslactone, isoalantolactone, and alantolactone (ATL). ATL was the most active lactone. SL-IR, SL-US, SL-SLE, or ATL showed a significant (P Abbreviations used: IR-AE: Infrared-assisted extraction; SL: Saussurea lappa, S. lappa; SL-IR: Saussurea lappa infrared extract; SL-US: Saussurea lappa ultrasound extract; SL-SLE: Saussurea lappa solid–liquid extract; ATL: Alantolactone; NDC: Nondiabetic control; DC: Diabetic control; MTF: Metformin; TBARS: Thiobarbituric acid; GSH: Reduced glutathione; CAT: Catalase; APA: Adequate for pregnancy age; LPA: Large for pregnancy age; SPA: Small for pregnancy age.

Rayleigh-Bénard-Marangoni convection characteristics during mass transfer between liquid layers

Rayleigh-Bénard-Marangoni convection (RBM convection) induced by the mass transfer has a great influence on the performance of real chemical engineering process. However, the researches of RBM convection characteristics during mass transfer across the interface in liquid-liquid system and their influence on the interface morphology are still limited. In this research, a visualization experiment via the amplified shadowgraph method is conducted to investigate the mass transfer in water-toluene-acetone system in a vertical slit. The convective structure of RBM and its evolution are visually observed. The effects of the initial acetone concentration of aqueous phase and toluene phase, and the thickness of toluene layer on the RBM characteristics and the morphology of the liquid-liquid interface are investigated. The experimental results show that these structures are induced by the interface tension difference along the interface and the vertical density difference caused by non-uniform mass transfer at the interface. As a result of the mass transfer at the interface, the density stratification occurs at the top of the aqueous phase, where the light liquid layer supports heavy one. In addition, non-uniform mass transfer produces perturbation at the top of the aqueous phase, which induces the Rayleigh-Taylor instability at the " interface” between the heavy and light liquid layer. Consequently, a wave-shaped-mound " interface” in the upper aqueous phase is formed as the heavy liquid comes down into the light one, and it can be further evolved into a plume flow with the enhancement of the imbalance between density and pressure at the " interface”. Due to the difference in mass transfer characteristic caused by different concentration gradients in the plume " interface”, the plumes can also evolve into weak plumes and strong plumes. Under the large acetone concentration gradient, a number of RBM convective structures are generated near the interface in a short time and the convective cloud is formed due to the dramatic interaction and coalescence between these structures. With the weakening of mass transfer, the convective cloud disappears and the strong plume is gradually formed. In addition, the strength of RBM convection is demonstrated to be positively correlated with the acetone concentration gradient across the aqueous solution- toluene interface. In addition, the roughness of the interface and its unsteady fluctuation grow up with the increase of acetone concentration gradient across the interface.

Simulation of the fate and transport of boron nanoparticles in two-dimensional saturated porous media

The wide production and application of engineered nanomaterials (ENMS) inevitably lead to their release in the groundwater environment. However, the release and transport of boron nanoparticles in the multi-dimensional subsurface remain largely unknown. In this work, a multi-dimensional numerical simulator for the transport of boron nanoparticles in the saturated porous media was first developed and validated. Hypothetical scenarios for the release of boron nanoparticles into a layered two-dimensional (2D) and heterogeneous 2D saturated porous media were then explored, and compared with the fullerene nanoparticles. The results demonstrated that the soil heterogeneity influenced the fate of nanoparticles, with high permeable layers and high aqueous-phase concentration. Besides, the boron nanoparticles tend to accumulate at the inlet zones, where it was closer to a nanoparticles source. Different layers of interface interaction also impact the concentration of nanoparticles. In general, the mobility and aqueous-phase concentration of fullerene nanoparticles were higher than those of the boron nanoparticles. In addition, the mobility of boron nanoparticles was found to be sensitive to release concentration, soil porosity and nanoparticle aggregate size.

Rheology of Water-in-Crude Oil Emulsions: Influence of Concentration and Temperature

The effect of aqueous phase content and temperature North Sea crude oil emulsion viscoelastic behavior has been studied. Heavy crude oil from the North Sea is of high viscosity and is capable of forming stable water-in-crude oil (w/o) emulsions without introducing any synthetic surfactants. The aqueous phase volume content was varied from 1 to 40%, and the temperature was varied from 0 to 30 °C. The w/o emulsion viscosity increased sharply when the aqueous phase content exceeds 20%, being more pronounced at the lower temperatures. The viscosity flow curves for emulsions containing more than 20% aqueous phase demonstrate non-Newtonian behavior, in contrast to crude oil, which is Newtonian. The coefficients in the master curve describing the viscosity-temperature dependence were determined. Oscillatory rheological tests showed that the loss modulus substantially exceeds the storage modulus which indicates the liquid-like state of the emulsions.

Separation of terbium from aqueous phase employing hollow fibre supported liquid membrane with EHEHPA as carrier

ABSTRACTHollow fibre membrane (HFM) operation in supported liquid membrane mode has been successfully employed for the separation of terbium from lean aqueous media by using EHEHPA (PC88A) as an extractant. The effects of different process parameters such as aqueous-phase acidity, extractant concentration, phase ratio and flow rate were evaluated to optimize the condition for effective transport of terbium from a lean nitrate aqueous medium. Diffusional parameters were evaluated to establish the rate-determining step in Tb(III) transport from the feed side to the strip phase. Under optimized conditions of 1 M PC88A, 0.1 M HNO3 as aqueous feed phase, 100 mL/min flow rate and phase ratio of 62:1, recovery of terbium was >95% from lean source. The process was successfully demonstrated in continuous mode of operation for concentrating the Tb(III) value from ppm to g/L under circulation mode while processing 30 L of aqueous phase. Considering the fast transport of terbium, three cycles HFM-SLM approach was proposed to concentrate Tb from 30% to 95%.

Prospective acid microemulsions development for matrix acidizing petroleum reservoirs

The oil exploration and drilling processes cause damage to the reservoir that result in decreasing production. Well stimulation processes are performed to repair this damage and restore the oil flow. Among them, matrix acidizing aims to unblock the pores by dissolving the rock, organic or inorganic scale through reaction with the injected acid, causing the dilation of the deeper pores to form long wormholes that provide a path for oil to flow from the reservoir to the production well. In this work, acid microemulsions were developed aiming to improve the stimulation process and reduce the problems caused by using acidic solutions, such as fast reaction with the reservoir rocks. The solvents used as the oil phase were kerosene and Solbrax Eco 175/235, while the aqueous phase consisted of hydrochloric acid (32%) and commercial nonionic surfactants based on ethoxylated lauryl alcohol containing different ethylene oxide units in their chains, and the cosurfactants were propanol and butylglycol. Initially, pseudo-ternary phase diagrams were constructed with the described components to determine the best concentrations of surfactant, cosurfactant, oil phase and aqueous phase to obtain microemulsions. The acidic microfluids prepared were characterized in terms of appearance, stability, particle size, density, viscosity, pH and type of emulsion. The most stable systems were selected for performance testing, where the rock-fluid reaction rate was measured. The results showed that a stable acid microemulsion was formed at room temperature, but not all the hydrochloric acid remained in the microemulsion. The best systems to retard the rock-fluid reaction rate were those containing ethoxylated lauryl alcohol with 1 unit of ethylene oxide.

Occurrence of antibiotics, estrogenic hormones, and UV-filters in water, sediment, and oyster tissue from the Chesapeake Bay

Globally, the occurrence of contaminants of emerging concern (CECs) in the environment has raised critical questions on ecological and human health, but few efforts have focused on the Chesapeake Bay, the largest estuary in the United States. Here, 43 antibiotics, 3 estrogenic hormones, and 5 ultraviolet-filters (UV-filters), which are active ingredients in a variety of personal care products, were measured in water, sediment, and oyster tissue from 14 sites along the Eastern Shore of the Chesapeake Bay in Maryland. Fluoroquinolone, macrolide, and sulfonamide antibiotics were detected in water samples. As both human- and animal-labeled antibiotics were found, wastewater effluent and agricultural runoff were identified as potential sources. The highest aqueous-phase concentrations were recorded for norfloxacin (94.1 ng/L), enrofloxacin (17.8 ng/L), sulfamethoxazole (14.8 ng/L), and clarithromycin (9.7 ng/L). Estrone and four UV-filters, namely 2-ethylhexyl-4-methoxycinnamate, benzophenone-3, homosalate, and octocrylene, were frequently detected in Chesapeake Bay water (93–100%), sediment (100%), and oyster tissue (79–100%). High sediment-phase concentrations of estrone (58.4 ng/g) and 17β-estradiol (11.5 ng/g) were detected at the mouth of the Manokin River. Homosalate and benzophenone-3 were present at concentrations as high as 187.9 and 113.7 ng/L in water, 74.2 and 10.8 ng/g in sediment, and 158.3 and 118.0 ng/g in oyster tissue, respectively. These results demonstrate the ubiquitous presence of CECs in the Chesapeake Bay, confirm UV-filter bioaccumulation in oysters, and suggest the need for improved CEC removal during municipal wastewater treatment and agricultural waste management within the Chesapeake Bay watershed.

Solutal convection in porous media: Comparison between boundary conditions of constant concentration and constant flux

We numerically examine solutal convection in porous media, driven by the dissolution of carbon dioxide (CO2) into water---an effective mechanism for CO2 storage in saline aquifers. Dissolution is associated with slow diffusion of free-phase CO2 into the underlying aqueous phase followed by density-driven convective mixing of CO2 throughout the water-saturated layer. We study the fluid dynamics of CO2 convection in the single aqueous-phase region. A comparison is made between two different boundary conditions in the top of the formation: (i) a constant, maximum aqueous-phase concentration of CO2, and (ii) a constant, low injection-rate of CO2, such that all CO2 dissolves instantly and the system remains in single phase. The latter model is found to involve a nonlinear evolution of CO2 composition and associated aqueous-phase density, which depend on the formation permeability. We model the full nonlinear phase behavior of water-CO2 mixtures in a confined domain, consider dissolution and fluid compressibility, and relax the common Boussinesq approximation. We discover new flow regimes and present quantitative scaling relations for global characteristics of spreading, mixing, and a dissolution flux in two- and three-dimensional media for both boundary conditions. We also revisit the scaling behavior of Sherwood number (Sh) with Rayleigh number (Ra), which has been under debate for porous-media convection. Our measurements from the solutal convection in the range 1, 500<Ra<135, 000 show that the classical linear scaling Sh ~ Ra is attained asymptotically for the constant-concentration case. Similarly linear scaling is recovered for the constant-flux model problem.

Occurrence and partitioning behavior of perfluoroalkyl acids in wastewater effluent discharging into the Long Island Sound

Perfluoroalkyl acids (PFAAs) were measured in aqueous and suspended particulate matter (SPM) fractions in the final effluents from 12 wastewater treatment facilities located around the Connecticut shoreline. Aqueous phase concentrations ranged from 53 to 198 ng/L for ∑PFAAs with ≤7 perfluorinated carbons (CF2) and 2–73 ng/L for >7 CF2 PFAAs. Predominant PFAAs associated with effluent derived SPM were perfluorodecanoic acid and perflurorooctane sulfonic acid, detected in 48% and 52% of samples in concentrations ranging from <LOQ–1770 ng/g and <LOQ–2750 ng/g respectively. Based on the range of concentrations detected and the average flow of final effluent to the Long Island Sound (LIS), average total annual PFAA mass loads from wastewater treatment facilities to the LIS is estimated in the range of 70–315 kg/year, with 4–100 kg/year consisting of >7 CF2 PFAAs. Partitioning coefficients (log KOC) derived for effluent water and SPM phases (4.2 ± 0.3, 4.4 ± 0.4, 5.1 ± 0.2 and 5.3 ± 0.2 for PFOA, PFNA PFDA and PFUnA; 4.5 ± 0.2 and 5.2 ± 0.2 for PFOS and PFHsX respectively) were found to be of similar magnitude to aeration tank particles, though 0.5 to 2 log units greater than sludge solids and to natural system particulates including riverine SPM, estuarine SPM and sediments. Results from this study suggest that effluent derived suspended particulate matter could be an effective vector in the transport of long-chained PFAAs through wastewater treatment into receiving waters, and a potential vector to the local food chain.