Equilibrium Partitioning Data Research Articles

The fate of nitrogen during core-mantle separation on Earth.

Nitrogen, the most dominant constituent of Earth's atmosphere, is critical for the habitability and existence of life on our planet. However, its distribution between Earth's major reservoirs, which must be largely influenced by the accretion and differentiation processes during its formative years, is poorly known. Sequestration into the metallic core, along with volatility related loss pre- and post-accretion, could be a critical process that can explain the depletion of nitrogen in the Bulk Silicate Earth (BSE) relative to the primitive chondrites. However, the relative effect of different thermodynamic parameters on the alloy-silicate partitioning behavior of nitrogen is still poorly known. Here we present equilibrium partitioning data of N between alloy and silicate melt ( ) from 67 new high pressure (P = 1-6 GPa)-temperature (T = 1500-2200 °C) experiments under graphite saturated conditions at a wide range of oxygen fugacity (logfO2 ~ΔIW - 4.2 to - 0.8), mafic to ultramafic silicate melt compositions (NBO/T = 0.4 to 2.2), and varying chemical composition of the alloy melts (S and Si contents of 0-32.1 wt.% and 0-3.1 wt.%, respectively). Under relatively oxidizing conditions (~ΔIW - 2.2 to - 0.8) nitrogen acts as a siderophile element ( between 1.1 and 52), where decreases with decrease in fO2 and increase in T, and increases with increase in P and NBO/T. Under these conditions remains largely unaffected between S-free conditions and up to ~17 wt.% S content in the alloy melt, and then drops off at > ~20 wt.% S content in the alloy melt. Under increasingly reduced conditions (< ~ ΔIW - 2.2), N becomes increasingly lithophile ( between 0.003 and 0.5) with decreasing with decrease in fO2 and increase in T. At these conditions fO2, along with Si content of the alloy under the most reduced conditions (< ~ΔIW - 3.0), is the controlling parameter with T playing a secondary role, while, P, NBO/T, and S content of the alloy have minimal effects. A multiple linear least-squares regression parametrization for based on the results of this study and previous studies suggests, in agreement with the experimental data, that fO2 (represented by Si content of the alloy melt and FeO content of the silicate melt), followed by T, has the strongest control on . Based on our modeling, to match the present-day BSE N content, impactors that brought N must have been moderately to highly oxidized. If N bearing impactors were reduced, and/or there was significant disequilibrium core formation, then the BSE would be too N-rich and another mechanism for N loss, such as atmospheric loss, would be required.

In situ air–water and particle–water partitioning of perfluorocarboxylic acids, perfluorosulfonic acids and perfluorooctyl sulfonamide at a wastewater treatment plant

In situ measurements of air and water phases at a wastewater treatment plant (WWTP) were used to investigate the partitioning behavior of perfluorocarboxylic acids (PFCAs), perfluorosulfonic acids (PFSAs) and perfluorooctyl sulfonamide (HFOSA) and their conjugate bases (PFC−s, PFS−s, and FOSA−, respectively). Particle-dissolved (Rd) and air–water (QAW) concentration ratios were determined at different tanks of a WWTP. Sum of concentrations of C4–12,14 PFC(A)s, C4,6,8,10 PFS(A)s and (H)FOSA were as high as 50pgm−3 (atmospheric gas phase), 2300ngL−1 (aqueous dissolved phase) and 2500ngL−1 (aqueous particle phase). Particle-dissolved concentration ratios of total species, log Rd, ranged from −2.9 to 1.3 for PFS(A)s, from −1.9 to 1.1 for PFC(A)s and was 0.71 for (H)FOSA. These field-based values agree well with equilibrium partitioning data reported in the literature, suggesting that any in situ generation from precursors, if they are present in this system, occurs at a slower rate than the rate of approach to equilibrium. Acid QAW were also estimated. Good agreement between the QAW and the air–water equilibrium partition coefficient for C8PFCA suggests that the air above the WWTP tanks is at or near equilibrium with the water. Uncertainties in these QAW values are attributed mainly to variability in pKa values reported in the literature. The WWTP provides a unique environment for investigating environmental fate processes of the PFCAs and PFSAs under ‘real’ conditions in order to better understand and predict their fate in the environment.

Adsorption of Quaternary Ammonium Compounds onto Activated Sludge

The performance of activated sludge in the removal of tetradecyl benzyl dimethyl ammonium chloride (C14BDMA) by adsorption from aqueous solution was investigated with different PH, contact time, ionic strength and temperature. Equilibrium was achieved within 2 h of contact time. The adsorption capacity increased largely with increasing solution pH and remained constant above pH 9. The ionic strength had a negative effect on C14BDMA removal. The adsorption isotherms were analyzed by Langmuir and Freundlich isotherm models, and equilibrium partitioning data was described well by both models. Kinetics data was best described by the pseudo second-order model. Experimental results indicated that the adsorption was favorable at lower temperatures. Thermodynamic parameters, including the Gibbs free energy (ΔG0), enthalpy (ΔH0), and entropy (ΔS0), were also calculated. These parameters indicated that adsorption of C14BDMA onto activated sludge was feasible, spontaneous and exothermic in the temperature range of 15-35℃. The activated sludge was shown to be an effective adsorbent for C14BDMA.

Biosorption of tetradecyl benzyl dimethyl ammonium chloride on activated sludge: Kinetic, thermodynamic and reaction mechanisms

The biosorption of tetradecyl benzyl dimethyl ammonium chloride (C14BDMA) onto activated sludge was examined in aqueous solution with respect to the contact time, temperature and particle size. Equilibrium reached in about 2h contact time. An decrease in the temperature increases of biosorption capacity of C14BDMA onto activated sludge, which also increases with decreasing particle size. The experimental data fit the pseudo-second-order kinetics model well. The Langmuir and Freundlich models were applied to describe equilibrium isotherms, and the equilibrium partitioning data was described well by both models. Thermodynamic data showed that C14BDMA biosorption onto activated sludge was feasible, spontaneous and exothermic. The Fourier transform infrared (FT-IR) spectrophotometry results show that both physisorption and chemisorption were involved. The measured zeta potential values and the enhanced cation concentration indicate the presence of electrostatic interactions, hydrophobic interactions and ion exchange.

Sorption of quaternary ammonium compounds to municipal sludge

The sorptive behavior of four quaternary ammonium compounds (QACs) – hexadecyl trimethyl ammonium chloride (C 16TMA), dodecyl trimethyl ammonium chloride (C 12TMA), hexadecyl benzyl dimethyl ammonium chloride (C 16BDMA), and dodecyl benzyl dimethyl ammonium chloride (C 12BDMA) – to municipal primary, waste activated, mesophilic digested, and thermophilic digested sludges was assessed at 22 °C. Batch adsorption of all four separately tested QACs to primary sludge reached equilibrium within 4 h. At a nominal, initial QAC concentration of 300 mg/L and a sludge volatile solids concentration of 1 g/L, the extent of adsorption was 13, 88, 67, and 89% for the C 12TMA, C 16TMA, C 12BDMA, and C 16BDMA, respectively, and correlated positively to the QAC hydrophobicity and negatively to their critical micelle concentration. Equilibrium partitioning data were described by the Freundlich isotherm model. The adsorption capacity of the four sludges was very similar. In binary QAC mixtures, QACs with relatively high adsorption affinity and at relatively high aqueous concentrations decreased the adsorption of QACs with a low adsorption affinity. At pH 7, about 40% of the sludge-C 12TMA desorbed, whereas less than 5% of the sludge-C 16BDMA desorbed in 10 days. The effect of pH was negligible on the desorption extent of C 12TMA at a pH range 4–10 over 10 days, whereas increasing the solution pH to 10 resulted in more than 50% desorption of C 16BDMA. Given the fact that approximately 50% of the municipal biosolids are land-applied in the US, the data of this study would help in the assessment of the fate of QACs and their potential effect on human and environmental health.

Hindered Convection of Macromolecules in Hydrogels

Hindered convection of macromolecules in gels was studied by measuring the sieving coefficient (Θ) of narrow fractions of Ficoll (Stokes-Einstein radius, r s = 2.7–5.9 nm) in agarose and agarose-dextran membranes, along with the Darcy permeability ( κ). To provide a wide range of κ, varying amounts of dextran (volume fractions ≤ 0.011) were covalently attached to agarose gels with volume fractions of 0.040 or 0.080. As expected, Θ decreased with increasing r s or with increasing concentrations of either agarose or dextran. For each molecular size, Θ plotted as a function of κ fell on a single curve for all gel compositions studied. The dependence of Θ on κ and r s was predicted well by a hydrodynamic theory based on flow normal to the axes of equally spaced, parallel fibers. Values of the convective hindrance factor ( K c, the ratio of solute to fluid velocity), calculated from Θ and previous equilibrium partitioning data, were unexpectedly large; although K c ≤ 1.1 in the fiber theory, its apparent value ranged generally from 1.5 to 3. This seemingly anomalous result was explained on the basis of membrane heterogeneity. Convective hindrances in the synthetic gels were quite similar to those in glomerular basement membrane, when compared on the basis of similar solid volume fractions and values of κ. Overall, the results suggest that convective hindrances can be predicted fairly well from a knowledge of κ, even in synthetic or biological gels of complex composition.

Theoretical Scales of Hydrogen Bond Acidity and Basicity for Application in QSAR/QSPR Studies and Drug Design. Partitioning of Aliphatic Compounds.

Phenomenological analysis of existing hydrogen bond (HB) donor and acceptor scales and apparent physical considerations have enabled the establishment of new quantitative scales of hydrogen bond basicity and acidity. Chemical structures represented by molecular graphs and the orbital electronegativities of Hinze and Jaffe are utilized as an input data. The scales obtained correlate well with several experimental solvent polarity scales such as and , pK(HB), and ET(30). To demonstrate the applicability of the new quantities, we have applied them to seven equilibrium partitioning data sets: octanol−water, hexadecane−water, chloroform−water, gas−water, gas−octanol, gas−hexadecane, and gas−chloroform partition coefficients. The hydrogen bond descriptors when supplemented by a cavity-forming term and a dipolarity term show high performance in correlations of the partition coefficients of aliphatic compounds. These new HB descriptors can be used in studying hydrogen bonding and fluid phase equilibria as well as...

Theoretical scales of hydrogen bond acidity and basicity for application in QSAR/QSPR studies and drug design. Partitioning of aliphatic compounds.

Phenomenological analysis of existing hydrogen bond (HB) donor and acceptor scales and apparent physical considerations have enabled the establishment of new quantitative scales of hydrogen bond basicity and acidity. Chemical structures represented by molecular graphs and the orbital electronegativities of Hinze and Jaffe are utilized as an input data. The scales obtained correlate well with several experimental solvent polarity scales such as and, pK(HB), and E(T)(30). To demonstrate the applicability of the new quantities, we have applied them to seven equilibrium partitioning data sets: octanol-water, hexadecane-water, chloroform-water, gas-water, gas-octanol, gas-hexadecane, and gas-chloroform partition coefficients. The hydrogen bond descriptors when supplemented by a cavity-forming term and a dipolarity term show high performance in correlations of the partition coefficients of aliphatic compounds. These new HB descriptors can be used in studying hydrogen bonding and fluid phase equilibria as well as scoring functions in ligand docking and descriptors in ADME evaluations.

Surface Complexation Modeling of Phosphate Adsorption by Water Treatment Residual

AbstractUse of water treatment plant residuals (WTR), as a soil amendment is a promising alternative to landfill disposal. Unfortunately, WTR has a propensity to bind with phosphate, which is an important plant nutrient. Phosphate may be added to WTR prior to soil application. This type of pretreatment may convert WTR from a phosphate consumer to a phosphate supplier. The binding of phosphate to WTR is typically attributed to surface complexation with metal oxides. However, attenuated total reflectance Fourier transform infrared (ATR‐FTIR) data and phosphate‐WTR adsorption equilibrium data indicate that phosphate also binds to a cationic polyelectrolyte that is added during water treatment processes. Using the FITEQL optimization program, equilibrium constants and total number of surface sites were determined for the polymer. Results from the FITEQL optimization were used to model binding of phosphate by cationic polymer. Binding of phosphate by hydrous ferric oxide was modeled using a diffuse double layer model, which included surface precipitation (MICROQL). The model was validated through the use of phosphate equilibrium partitioning data at pH values of 6 and 8. The model predicted that a significant fraction of phosphate adsorbed onto WTR is associated with the cationic polymer.

Transport and Sorption of Organic Gases in Activated Carbon

The relationships among adsorption-desorption kinetics, equilibrium partitioning, and fixed-column breakthrough curves are elucidated for airborne benzene and vinyl chloride on activated carbon grains and fibers. An electrobalance is used to measure adsorption/desorption kinetics and to obtain equilibrium partitioning data; column experiments are conducted to determine additional equilibrium partitioning data and to measure breakthrough curves. A porous sphere/cylinder intragrain diffusion model, coupled with a Freundlich isotherm to describe equilibrium partitioning, conforms closely to the experimental kinetic data for both adsorption and desorption. In addition, it is shown that the adsorption isotherm may be accurately predicted based on the asymmetry between adsorption and desorption rates measured in a single kinetic experiment. The parameters extracted from the kinetic experiment, when combined with the appropriate transport equations, can be used to accurately forecast column breakthrough curves.