Freundlich Partition Research Articles

Combining Experimental Sorption Parameters with QSAR to Predict Neonicotinoid and Transformation Product Sorption to Carbon Nanotubes and Granular Activated Carbon.

We recently discovered that transformation of the neonicotinoid insecticidal pharmacophore alters sorption propensity to activated carbon, with products adsorbing less than parent compounds. To assess the environmental fate of novel transformation products that lack commercially available standards, researchers must rely on predictive approaches. In this study, we combined computationally derived quantitative structure–activity relationship (QSAR) parameters for neonicotinoids and neonicotinoid transformation products with experimentally determined Freundlich partition constants (log KF for sorption to carbon nanotubes [CNTs] and granular activated carbon [GAC]) to model neonicotinoid and transformation product sorption. QSAR models based on neonicotinoid sorption to functionalized/nonfunctionalized CNTs (used to generalize/simplify neonicotinoid-GAC interactions) were iteratively generated to obtain a multiple linear regression that could accurately predict neonicotinoid sorption to CNTs using internal and external validation (within 0.5 log units of the experimentally determined value). The log KF,CNT values were subsequently related to log KF,GAC where neonicotinoid sorption to GAC was predicted within 0.3 log-units of experimentally determined values. We applied our neonicotinoid-specific model to predict log KF,GAC for a suite of novel neonicotinoid transformation products (i.e., formed via hydrolysis, biotransformation, and chlorination) that do not have commercially available standards. We present this modeling approach as an innovative yet relatively simple technique to predict fate of highly specialized/unique polar emerging contaminants and/or transformation products that cannot be accurately predicted via traditional methods (e.g., pp-LFER), and highlights molecular properties that drive interactions of emerging contaminants.

Interactions among Glyphosate and Phosphate in Soils: Laboratory Retention and Transport Studies.

The purpose of this study was to determine the effect of PO on the sorption and transport of glyphosate [-(phosphonomethyl) glycine, GPS] in soils. The results of batch experiments indicated significant competition between PO and GPS in two different soils, with PO being preferentially sorbed. The 24-h Freundlich partitioning coefficients for GPS sorption were decreased by 50 to 60% with PO in solution. High sorptive capacities exhibited by soils in the presence of PO suggest the existence of both competitive and ion specific sites in either soil. Miscible displacement transport studies indicated limited effects of competition when GPS was applied in conjunction with or subsequent to pulses of PO. However, when a PO pulse was applied after the application of a GPS pulse, a secondary GPS breakthrough was observed where an additional 4% of the applied herbicide mass was recovered in the effluent solution. This is likely attributed to the PO-mediated displacement of GPS bound to competitive sites. These results are further emphasized by the distribution of residual herbicide in this column, with enrichment of mass at lower depths in the column and a corresponding decrease in GPS mass closer to the column surface. These results indicate that the timing of inorganic P fertilizers relative to GPS applications has a significant impact on the fate of the herbicide in soils. In particular, these findings suggest that GPS may be more liable to leaching in scenarios in which P fertilizers are applied after the application of GPS-based herbicidal formulations.

Influence of soil variability on single and competitive interaction of ammonium and potassium: experimental study on seven different soils

Ammonium and potassium are nutrients that generally co-exist together in soils in municipal wasteland. The main objective of this study is to investigate the interactive effects of NH4+ and K+ on their sorption characteristics in seven different soils. The adsorption parameters (Freundlich partition coefficient KF and maximum contaminant adsorbed by solid Qm) of both the isotherms for single and competitive interactions were correlated with soil-specific parameters (total specific surface area (SSA) and cation exchange capacity (CEC)). To depict the significant variation of the ions in the presence of other ions, percentage reduction of the isotherm parameters was calculated. Both the ions exhibited a competitive mode of inhibition in the presence of one another. However, the effects varied with soils and the range of concentration. The study demonstrated that at lower concentration, the NH4+ and K+ ion competed equally in all the soils. However, after a certain range of concentration unique for each soil, NH4+ retention was found to be marginally higher than K+. The study also signified some analogous values of the Freundlich and Langmuir isotherm parameters for soils like F Bent and Kao, which contradicted other experimental findings. This study can be useful for predicting fate of potassium and ammonium for risk assessment of contaminated sites and hence, in design or analysis of certain waste contaminant barrier under concept of sponge city.

Influences of activated sludge surface properties on adsorption of aqueous fullerene C60 nanoparticles

Rapid increases in the amounts of fullerene C60 nanoparticles (nC60) being produced and used will inevitably lead to increases in the amounts released into the aquatic environment. This will have implications for human and ecosystem health. Wastewater treatment plants are key barriers to nC60 being released into aquatic systems, but little information is available on how adsorption processes in wastewater treatment plants affect the fates of nC60. We investigated the effects of the surface properties of activated sludge on the adsorption of nC60 and related mechanisms by modeling the adsorption kinetics and equilibrium process and performing correlation analyses. The adsorption of nC60 closely followed the pseudo-second-order kinetic model (R > 0.983), the Freundlich isotherm model (R > 0.990), and the linear partitioning isotherm model (R > 0.966). Different adsorption coefficients, 1.070–4.623 for the Freundlich partitioning model and 1.788–6.148 for the linear partitioning model, were found for different types of activated sludge. The adsorption coefficients significantly positively correlated with the zeta (ζ) potential (R = 0.877) and hydrophobicity (R = 0.661) and negatively correlated with particle size (R = −0.750). The results show that nC60 adsorption is strongly affected by the surface properties of activated sludge because changes in surface properties cause changes in the electrostatic and hydrophobic interactions that occur.

수중의 구리 제거를 위한 질석흡착제의 표면개질 연구

본 연구는 팽창질석에 글리세롤과 황산으로 코팅하여 <TEX>$580^{\circ}C$</TEX>에서 가열시킨 코팅질석(MEVs)을 사용해 수용액 상의 구리이온을 더 효과적으로 흡착제거 할 수 있는가를 평가하고자 하였다. 수용액 상의 구리이온의 제거양상을 살펴보기 위해 batch kinetic test와 batch sorption test가 실시되었다. 그 결과, 구리 제거속도(<TEX>$K_{obs}$</TEX>, 1/hr)는 MEVs가 1g(25g/L)일 때 0.579, 2g(50g/L)일 때 0.878, 3g(75g/L)일 때 3.459, 4g(100g/L)일 때 6.578이었고, 초기pH는 3.26이었다. 농도에 따른 제거실험에서 구리 제거속도는 3mg/L일 때 1.96, 5mg/L일 때 1.375, 8mg/L일 때 1.25, 10mg/L일 때 1.04었고, 초기 pH는 각각 3.46, 3.26, 3.10, 2.96이었다. 초기 pH에 따른 구리의 제거속도는 pH 3~pH 5에서 0.263~0.525의 범위를 보였다. 이 결과는 초기구리농도와는 반비례하고 초기 pH와는 비례하는 양상을 보였다. Batch sorption test에서 Langmuir 모델의 최대 흡착용량(<TEX>$Q_{max}$</TEX>)과 Linear, Freundlich 모델의 분배계수는 각각 0.761mg/g, 0.494L/g, 0.729L/g(1/n = 0.476)였다. 이 결과는 글리세롤 코팅질석이 여러 형태의 수용액에 존재하는 구리이온을 효과적으로 제거할 수 있다는 것을 보여준다. The main objective of this study was to evaluate the removal properties of Cu from existing exfoliated vermiculite (EV) coated with a mixed solution of sulfuric acid and glycerol on the <TEX>$580^{\circ}C$</TEX> in heating, which uses coated with glycerol of copper ions can be removed more effectively. Serial batch kinetic tests and batch sorption tests were conducted to determine the removal characteristics for Cu in aqueous solution. The result of batch kinetic test shows that removal rate, <TEX>$K_{obs}$</TEX> (1/hr), of Cu are 0.579, 0.878, 3.459, and 6.578 for MEV weight 1 g (25 g/L), 2 g (50 g/L), 3 g (75 g/L), 4 g (100 g/L), respectively. In this case the initial pH of the solution was 3.26. The removal experiment according to the concentration, <TEX>$K_{obs}$</TEX> (1/hr), of Cu are 1.96, 0.878, 1.25, and 1.04 for the initial concentration of 3 mg/L, 5 mg/L, 8 mg/L, 10 mg/L, and the initial pH of the solution are 3.46, 3.26, 3.10, 2.96, respectively. Influence of initial pHs on Cu removal were tested under 1g of MEV with 5 mg/L of Cu solution. <TEX>$K_{obs}$</TEX> (1/hr) were increased from 0.263 (pH 3) to 0.525 (pH 5). It leads to the conclusion that the removal rates are inversely proportional to the initial Cu concentration and are increased proportional to the initial pHs. Sorption capacity of MEV was determined by batch sorption tests. The maximum sorption capacity (<TEX>$Q_{max}$</TEX>) obtained from Langmuir was 0.761 mg/g, Linear and Freundlich partition coefficients were 0.494 L/g and 0.729 L/g (1/n = 0.476). These results show that the MEV could be used as an excellent adsorbent for copper contained in various types of aqueous solutions.

Modification of Vermiculite for the Preparation of Floating Adsorbent for Phosphate in Wastewater.

Floating adsorbents made from exfoliated vermiculite (EV) were tested for their ability to remove phosphate in aqueous solution. The modified vermiculites (MEV) were prepared with EV/glycerol ratio of 1/4 where glycerol contained 4 mol% H2SO4 and heated until designated temperatures. The highest specific surface area of 58.6 m(2)/g and carbon content of 62.2% were obtained for MEV heated at 580 °C and 380 °C, respectively. The dry density of MEV was decreased from 1.78 g/cm(3) (EV) to 0.25 g/cm(3), indicating these adsorbent floating characteristic. The MEV heated at 380 °C showed the highest Freundlich partition coefficient of 45.7 L/kg and the highest Langmuir sorption capacity of 714.3 mg/kg among other MEVs (476.2 mg/kg for MEV-580 and 181.8 mg/kg for MEV-780). Removal of phosphate using MEV heated at 380 °C was well explained by pseudo-second-order model and model parameters were comparable to other phosphate adsorption tests.

Sorption parameters as a predictor of arsenic phytotoxicity in Australian soils

Arsenic (As) is a mobile and ecotoxic metalloid that is of serious concern to the environment. In this study, As phytotoxicity was studied using a dose–response approach for seven contrasting soils considering 3 end-points (shoot biomass, root elongation and chlorophyll content) and focusing on predictors of toxicity. Root elongation study was carried out for 4days using both Cucumis sativus L. (cucumber) and Triticum aestivum L. (wheat) and shoot end-points with a 4week a pot study using cucumber only. Root elongation of cucumber was a substantially less sensitive indicator to As than data from the 4weeks pot study. Effective concentrations (50%)(EC50) from cucumber root elongation studies were overall 1.6 times higher than the 4week shoot data. Cucumber was however considerably more sensitive to wheat. Given the large discrepancy in phytotoxicity end points for 7 soils, root elongation data for ecotoxicological assessment should be treated with some caution. Arsenic phytotoxicity was strongly related to the sorption constants of each of the seven soils in our study. Both root elongation and shoot data were related strongly to Freundlich partitioning constants (Kf) (L/kg). Wheat and cucumber root elongation had R2 values 0.90 and 0.91 respectively, while cucumber shoot data was 0.79. The Kf values were related to soil pH and also EC50 data and, thus, shows that As phytotoxicity in our study was primarily controlled by sorption reactions. The rate of As bioaccumulation to cucumber shoots depended heavily on the soil under consideration. Chlorophyll and carotenoid content of cucumber shoots increased with As content in 3 soils and decreased in other soils.

Using soil properties to predict in vivo bioavailability of lead in soils

Soil plays a significant role in controlling the potential bioavailability of contaminants in the environment. In this study, eleven soils were used to investigate the relationship between soil properties and relative bioavailability (RB) of lead (Pb). To minimise the effect of source of Pb on in vivo bioavailability, uncontaminated study soils were spiked with 1500mg Pb/kg soil and aged for 10–12months prior to investigating the relationships between soil properties and in vivo RB of Pb using swine model. The biological responses to oral administration of Pb in aqueous phase or as spiked soils were compared by applying a two-compartment pharmacokinetic model to blood Pb concentration. The study revealed that RB of Pb from aged soils ranged from 30±9% to 83±7%. The very different RB of Pb in these soils was attributed to variations in the soils’ physico-chemical properties. This was established using sorption studies showing: firstly, Freundlich partition coefficients that ranged from 21 to 234; and secondly, a strongly significant (R2=0.94, P<0.001) exponential relationship between RB and Freundlich partition coefficient (Kd). This simple exponential model can be used to predict relative bioavailability of Pb in contaminated soils. To the best of our knowledge, this is the first such model derived using sorption partition coefficient to predict the relative bioavailability of Pb.

Characterization of Ammonium Sorption by Beef Cattle Feedyard Manure

Ammonia (NH3) emissions from beef cattle feedyards represent a loss of agronomically important N and can potentially affect the environment. Sorption of ammonium (NH4+) and NH3 by mineral and organic solids decreases the proportion of free, aqueous ammoniacal N, which reduces volatilization potential. In the U.S., the High Plains region of Texas is subject to arid conditions with widely fluctuating temperatures. Furthermore, feedyard manure contains little soil and has high dry matter (DM) content; therefore, it is unclear if sorption parameters determined for soils or liquid manure systems are valid for feedyards. Our objectives were to use batch equilibration experiments to characterize NH4+ sorption by two feedyard manures. Kinetic and isotherm studies with (NH4)2SO4/0.01 M CaCl2 solutions revealed that feedyard manures could sorb up to 227 cmol kg-1 NH4+-N and that sorption was rapid and linearly related to NH4+ concentration. The Freundlich partitioning coefficient (Kp) for NH4+ sorption averaged 13.3 L kg-1. From 58% to 96% of the sorbed NH4+ was readily desorbable with 0.01 M CaCl2, and up to 81% was volatilized as NH3 when manures were air-dried. Temperature influenced sorption, with 112% more NH4+ sorption at 4C than at 22C. These results indicate that NH4+ sorption by manure on feedyard surfaces may temporarily reduce NH3 volatilization, particularly during winter.

Validation and Uncertainty Analysis of an Ammonia Emission Model for Broiler Litter

A mechanistic emission model was previously developed at laboratory scale to estimate ammonia emission fluxes from broiler litter. The overall model inputs include air temperature, air velocity, and litter properties such as litter nitrogen content, moisture content, and pH. The model outputs are predicted ammonia emission fluxes from litter. Considerable uncertainties may exist in measurement values of model inputs and outputs as well as model parameters. The purpose of this study was to perform model validation in the presence of measurement and model parameter uncertainties. A validation metric based on the mean and covariance in the measurement and in the model parameters was used to validate the ammonia emission model of broiler litter. The core model was validated given the uncertainties in the model prediction due to uncertainties of parameters (the Freundlich partition coefficient Kf and the mass transfer coefficient KG) and the uncertainties in the measurements. The significant level for the core model validation was 17.8%. The Kf submodel was validated at the given uncertainties of pH and temperature, and the significant levels were from 12.0% to 49.4%, which provided high confidence on the Kf submodel. At the given uncertainty levels of air velocity and temperature, the KG submodel passed the validation test (p > 0.05) when air velocities were low and failed the validation test (p < 0.05) when air velocities were high. The failure of the KG submodel at high air velocity levels may have been caused by significant loss of nitrogen and moisture content from the litter surface.

Modeling Ammonia Emissions from Broiler Litter at Laboratory Scale

The objectives of this study were to develop a mechanistic emission model to estimate ammonia flux from broiler litter and to evaluate the model at laboratory scale. In the proposed model, the ammonia flux is essentially a function of the litter's total ammoniacal nitrogen (TAN) content, moisture content, pH, and temperature, as well as the Freundlich partition coefficient (Kf), mass transfer coefficient (KG), ventilation rate (Q), and emission surface area (A). The Freundlich partition coefficient (Kf) was used as a fitting parameter in the model. A dynamic flow-through chamber system and a wind tunnel were designed to measure ammonia fluxes from broiler litter. The dynamic flow-through chamber experiments evaluated the proposed model with various litter samples under a constant temperature and wind profile. The wind tunnel experiments evaluated the proposed model under various temperatures and wind profiles. Model parameters such as Kf and KG were estimated. The results from the two experiments were consistent with each other. The estimated KG ranged from 1.11 to 27.64 m h-1, and the estimated Kf ranged from 0.56 to 4.48 L kg-1. A regression sub-model was developed to estimate Kf as function of litter pH and temperature, which indicated that Kf increased with increasing litter pH and decreased with increasing temperature. The proposed model was used to estimate the equilibrium gas phase ammonia concentration (Cg,0) in litter, and the model-predicted values were compared with the observed values. The normalized mean error (NME), the normalized mean square error (NMSE), and fractional bias (FB) were calculated to be 25%, 12%, and -0.3%, respectively, for all 94 measurements, and the model was able to reproduce 80% of the variability of the data. Sensitivity analysis of the model showed that ammonia flux is very sensitive to litter pH and to a lesser extent temperature. The relative sensitivity of pH or temperature increases as the pH or temperature increases.

Lead and Zinc Partition Coefficients of Selected Soils Evaluated by Langmuir, Freundlich, and Linear Isotherms

The paper outlines some approaches that should be considered in the calculation of partition coefficients based on Langmuir, Freundlich and Linear isotherms. It was found that the Langmuir partition coefficient (K Lg ), whose calculation involved the maximal amount of lead (Pb) and zinc (Zn) adsorbed and their appropriate bonding term energy, seemed more “precise” than the Freundlich (K F ) and Linear (K Li ) based partition coefficients. The Freundlich partition coefficients were decidedly lower than the Langmuir and Linear ones and appeared to “resist” to changes of equilibrium lead and zinc equilibrium concentrations. This feature may lead to a potential underestimation of calculated K F coefficients due to the heterogenic nature of soil adsorptive surface. The “adequate” Linear partition coefficient should unconditionally be obtained from the slope of the C‐type plot (isotherm) of the amount adsorbed versus its solution concentration. This step will occur when the Freundlich exponent n = 1. Langmuir partition coefficient (K Lg ) as a convenient and reliable parameter to be applied for soil adsorption capacities assessment should be recommended.

Optimal Solid‐to‐Solution Ratios for Organic Chemical Sorption Experiments

AbstractThe presence of organic chemicals in natural systems requires an understanding of how these chemicals distribute themselves between the different phases of the environment. Partition coefficients (K) then are an important parameter for environmental fate studies. One experimentally critical parameter in the estimation of K for solid‐liquid systems is the solid‐to‐solution ratio. Recommendations for a solid‐to‐solution ratio have ranged widely. Our objective was to derive a relationship for the variance of K, based on the analytical precision of the experimental variables, that could be used to determine the optimal solid‐to‐solution ratio for linear and Freundlich‐type partitioning. The optimal solid‐to‐solution ratio occurred at 55% sorption for linear and Freundlich partitioning when the Freundlich constant was between 0.8 and 1.

Thermodynamics of Organic Chemical Partition in Soils. 1. Development of a General Partition Model and Application to Linear Isotherms

A general thermodynanmic partition model for organic carbon-based linear and nonlinear sorption from solution was formulated in order to characterize sorbate partial molar free energies. The partial molar free energies are considered as the sum of two components: the Flory combinatorial entropy of mixing and a residual free-energy component. By using appropriate concentration units in the solution and sorbed phases, the conventional Freundlich partition coefficient was found to be related to the aqueous-phase activity coefficient and sorbate solubility (corrected for crystal energy effects, if any) in the humic phase. The Freundlich exponent was related to the variation of sorbate partial molar free energy with loading

Sorption of Polycyclic aromatic hydrocarbons by natural estuarine colloids

The sorptive behaviour of natural estuarine colloids was investigated with benzene, naphthalene and anthracene. The equilibrium sorption isotherms were linear. Freundlich partition coefficients normalized to the organic content of the colloids for benzene, naphthalene, and anthracene were 920, 4060 and 510000, respectively. These values are at least an order of magnitude higher than those reported for corresponding soil/sediment systems. This suggests that hydrophobic compounds are more strongly bound to estuarine colloidal organic material. The effect of pH on sorption waas also studied. A significant decrease in sorption was observed when the ambient pH (8·01) of natural water was decreased by a factor of 2. The experimentally determined K oc values were regressed against the water solubilities of PAHs and compared with a corresponding predictine relationship developed for a soil/sediment system. Such information greatly facilitates prediction of PAH phase partitioning in natural waters.