Volume Fraction Of Cosolvent Research Articles

Encapsulation of Nanoparticles into Preformed Block Copolymer Micelles Driven by Competitive Solvation: Experimental Studies and Molecular Dynamic Simulations

We investigate the encapsulation of polymer-tethered nanoparticles (NPs) inside block copolymer (BCP) micelles, which turns to the mutual stabilization of BCP micelles and NPs by each other. It has been demonstrated, for the first time, that in the presence of cosolvent, which is selective for the core-forming block, the encapsulation of polymer-tethered NPs into the core of preformed BCP micelles is feasible. Furthermore, interestingly, in a certain range of cosolvent volume fraction, NP/BCP hybrid micelles comprising a single NP in the micelle core could be obtained. Significantly, in the presence of cosolvent the NP-loaded hybrid micelles remain intact, whereas the NP-free (empty) micelles undergo further transformations. The experimental observations are additionally supported by the results obtained from the molecular dynamic simulation. In particular, our modeling recognizes mechanisms for the formation of NP/BCP hybrids, which include a one-by-one adsorption of individual BCP chains onto the NP surface, fusion of NP with the preformed BCP micelles, or a combination of both mechanisms. The present work provides new opportunities for the fabrication of BCP-based hybrid nanomaterials having potential applications in drug delivery, diagnostics, catalysis, energy harvesting materials, optical devices, etc.

Implementation of a choline bis(trifluoromethylsulfonyl)imide aqueous electrolyte for low temperature EDLCs enabled by a cosolvent

We report a carbon/carbon capacitor based on micro/mesoporous carbon electrodes with cost-effective and eco-friendly aqueous choline bis(trifluoromethylsulfonyl)imide (ChTFSI) electrolyte with a cosolvent enabling low-temperature operation down to −30 °C. For this purpose, a MgO-templated hierarchical carbon (MP98B) with an average mesopore diameter of 3.5 nm was prepared by pyrolysis of magnesium citrate hydrate at 900 °C. To reach lower temperatures, the melting point and viscosity of the aqueous electrolyte were reduced by mixing water (W) with an organic solvent (methanol, M, or isopropanol, I) of high dielectric constant and low viscosity. 5 mol kg−1 (5 m) ChTFSI in an optimized volume fraction of cosolvent, M0.75W0.25, and I0.75W0.25, showed the highest conductivity; the higher conductivity in M0.75W0.25 (22.8 and 3.1 mS cm−1 at 20 and −30 °C, respectively) than in I0.75W0.25 (8.5 and 0.5 mS cm−1 at 20 and −30 °C, respectively) is attributed to the lower viscosity of the M0.75W0.25 solution. The electrochemical stability window (ESW) of 5 m ChTFSI in M0.75W0.25 and I0.75W0.25 (1.6 V) on an MP98B electrode was determined by applying the S-method. Meanwhile, by adjusting the mass ratio of the two electrodes, a MP98B/MP98B capacitor using the 5 m electrolyte in M0.75W0.25 could operate with a good life span up to 1.6 V while exhibiting a better charge propagation, greater specific capacitance, and higher specific energy than in I0.75W0.25.

Selectivity limits of and opportunities for ion pair chromatographic separation of oligonucleotides

Here it was investigated how oligonucleotide retention and selectivity factors are affected by electrostatic and non-electrostatic interactions in ion pair chromatography. A framework was derived describing how selectivity depends on the electrostatic potential generated by the ion-pair reagent concentration, co-solvent volume fraction, charge difference between the analytes, and temperature. Isocratic experiments verified that, in separation problems concerning oligonucleotides of different charges, selectivity increases with increasing surface potential and analyte charge difference and with decreasing co-solvent volume fraction and temperature. For analytes of the same charge, for example, diastereomers of phosphorothioated oligonucleotides, selectivity can be increased by decreasing the co-solvent volume fraction or the temperature and has only a minor dependency on the ion-pairing reagent concentration. An important observation is that oligonucleotide retention is driven predominantly by electrostatic interaction generated by the adsorption of the ion-pairing reagent. We therefore compared classical gradient elution in which the co-solvent volume fraction increases over time versus gradient elution with a constant co-solvent volume fraction but with decreasing ion-pair reagent concentration over time. Both modes decrease the electrostatic potential. Oligonucleotide selectivity was found to increase with decreasing ion-pairing reagent concentration. The two elution modes were finally applied to two different model antisense oligonucleotide separation problems, and it was shown that the ion-pair reagent gradient increases the selectivity of non-charge–based separation problems while maintaining charge-difference–based selectivity.

Micellization of Sequence-Controlled Polyurethane Ionomers in Mixed Aqueous Solvents.

While the impact of compositional parameters such as block length and ionic content on the micellization of (polymeric) amphiphiles is widely investigated, the influence of monomer sequence has received far less attention until recently. Here, we report the synthesis of two sequence-controlled polyurethane ionomers (PUIs) prepared via a stepwise coupling-deprotection strategy, and compare their solution association in aqueous–organic mixtures. The two PUIs are highly similar in mass and overall composition, yet differ markedly in the sequence of building blocks. PUI-A2 comprises a polytetrahydrofuran (pTHF) block connected to an alternation of isophorone diamine (IPDA) and dimethylolpropionic acid (DMPA) units that together are also arranged in a blockwise manner. The result is a macromolecular structure with a comparatively hydrophobic tail (pTHF) and a hydrophilic headgroup, which structure is reminiscent of those of traditional surfactants, albeit much larger in size. PUI-S2 instead resembles a bolaamphiphilic architecture with a pTHF midblock connected on either end to a singly charged segment comprising DMPA and IPDA. We detect micellization below a threshold cosolvent volume fraction (φsolv) of 0.4 in aqueous–organic mixtures with tetrahydrofuran (THF), ethanol, and isopropyl alcohol. We use scattering tools to compare the aggregation number (Nagg) and hydrodynamic radius (Rh) of PUI-S2 and PUI-A2 micelles. Irrespective of the solvent composition, we observe in the micellar window of φsolv < 0.4, lower Nagg for PUI-S2 micelles compared to PUI-A2, which we attribute to packing restraints associated with its bolaamphiphilic architecture. The increase in micellar size with increasing φsolv is much more pronounced for PUI-S2 than for PUI-A2. The micellar mass decreases with increasing φsolv for both PUIs; the effect is modest for PUI-S2 compared to PUI-A2 and is not observed in the most apolar cosolvent studied (THF). Upon the approach of the micellization boundary φsolv ≈ 0.4, both types of PUI micelles become less compact in structure, as (in most cases) PUIs are released and as micellar dimensions increase.

Supercritical fluid-assisted crystallization of CH3NH3PbI3 perovskite films

Crystallization of CH3NH3PbI3 perovskite films was performed in supercritical carbon dioxide with and without organic cosolvents. Post deposition crystallization of the films was performed in a binary, single phase supercritical fluid at constant conditions (45℃, 1200 psi) but with varying cosolvent volume fractions up to 2 %. Organic cosolvents with varying polarity, propensity for hydrogen bonding and strength of solvation were used and the resulting perovskite film morphology, crystal structure and optical absorption spectra were measured. It was determined that the cosolvents can provide selective interactions with one or both of the perovskite precursor compounds resulting in different film morphologies ranging from uniform films containing large grains to films exhibiting large cubic or hexagonal crystals or preferential crystallographic orientations. The use of supercritical fluids to enhance or tune crystallization in solid-state thin films could have broad applications toward the realization of high efficiency photovoltaic devices.

Co-Nonsolvency Response of a Polymer Brush: A Molecular Dynamics Study

Using molecular dynamics simulations, we study the response of a polymer brush exposed to co-nonsolvent (CNS), which acts as a preferential solvent for the polymer. We investigate a broad range of attractions between CNS and monomers and of grafting densities over the full range of cosolvent volume fractions. We compare our simulation results with the recently proposed adsorption–attraction model for co-nonsolvency in polymer brushes. The brush layer collapses with increasing CNS concentration into a more compact layer and followed by a reswelling toward sufficiently high CNS concentrations. As the strength of attraction of CNS toward the brush increases, the collapse transition becomes discontinuous. Increasing the grafting density leads to higher sensitivity with respect to CNS but also to a weaker collapse behavior as predicted from the analytical model. In the narrow collapse region, two states of the brush layer coexist, as can be expected from the type-II phase-transition behavior. The coexistence states are identified by analyzing the density profiles. Here, a dense layer is formed at the substrate, which is covered by a swollen layer. Both collapse and coexistence behaviors are even more pronounced in polydisperse brushes, indicating the robust nature of the co-nonsolvency effect in polymer brushes.

High-Pressure Electrochemistry: The Electrochemical Reduction of Carbon Dioxide into Usable Fuels and Chemicals

Currently, the United States ranks second internationally in terms of absolute carbon dioxide (CO2) emissions per year, exceeded only by China. Nearly 30% of these emissions come from coal- and natural gas-fired power plants. Carbon capture and storage (CCS) technologies can potentially reduce net CO2 emissions from power sectors; however, efforts, to date, have not been widely adopted due to high CO2 sequestration cost (over $60 per metric ton of CO2 captured). Electrochemical fixing of CO2 in stable high value marketable chemical products can potentially reduce net CO2 capture costs. Further, electrochemical systems can be powered by renewable electricity sources, thereby ensuring that no additional CO2 is produced in the process of CO2 removal. At present, all electrochemical-based carbon utilization technologies suffer from low product yield and rates, making them impractical for commercial applications. This poster will summarize our recent findings on CO2 reduction obtained from a high pressure electrochemical reactor. The motivation for using a high-pressure electrochemical reactor is to overcome two major limitations: (1) the low-current density caused by low CO2 solubility in ambient conditions; and (2) the low selectivity for CO2 reduction caused by the competing proton reduction to hydrogen. Particularly, the poster will summarize the results on CO2 reduction currents on Cu and Ag electrocatalysts as a function of CO2 partial pressure, co-solvent volume fraction, inter electrode spacing, and salt concentration.

Effect of Polyethyleneglycols (PEG) on Solubility of CoIII5,10,15,20-Tetra(4-carboxyphenyl)porphyrin and Methylimidazolyl Axial Complex at 298.2 K: Experiment and Modeling

The solubility of CoIII 5,10,15,20-tetra(4-carboxyphenyl)porphyrin and axial complex with methylimidazole in the mixtures of triethyleneglycol-water and tetraethyleneglycol-water was measured in the whole range of polyethyleneglycols (PEG) fractions at 298.2 K using the isothermal saturation method. The composition of the mixture at which the maximal solubility was observed has been revealed. The cosolvent force of PEGs was quantified according to the linear logarithmic model proposed by Yalkowsky applied in the ranges (cosolvent volume fraction, f): 0 ≤ fPEG ≤ 0.24 in triethyleneglycol-water and 0 ≤ fPEG ≤ 0.3 in tetraethyleneglycol-water mixtures. A mathematical approach based on the tenets of the molecular association theory and a simple lattice model (ASL = association solution + lattice) was used to estimate the solubility values of the investigated porphyrins in water-PEG solutions. The ASL model appeared to present a simple means of estimating the solubility of CoIII5,10,15,20-tetra(4-carboxyphenyl)porphyrin and axial complex with methylimidazole in polyethyleneglycol-water mixtures using a single variable parameter.

Measuring Aqueous Solubility in the Presence of Small Cosolvent Volume Fractions by Passive Dosing

A new passive dosing method was developed to determine aqueous solubility of hydrophobic chemicals. In the passive dosing method, chemical crystals were loaded to a polydimethylsiloxane (PDMS) phase to maintain the maximum chemical activity and to prevent direct contact of chemical crystals with the aqueous solution. Eight polycyclic aromatic hydrocarbons (PAHs) were chosen covering their literature aqueous solubility from 0.001 to 30 mg L(-1). Values of the aqueous solubility for less hydrophobic PAHs (naphthalene, 2-methylnaphthalene, and fluorene) were measured by an Organization for Economic Co-ordination and Development (OECD)-recommended generator column method and those for more hydrophobic PAHs (anthracene, chrysene, and benzo(a)pyrene) were measured by the passive dosing method. For phenanthrene and pyrene, both methods were used for comparison. The results obtained by the passive dosing method were very close to those obtained by the generator column method. Aqueous solubilities in deionized water for more hydrophobic PAHs obtained using the passive dosing method agreed very well with values reported in the literature, suggesting the utility of the passive dosing method for the determination of aqueous solubility for highly hydrophobic chemicals. Because hydrophobic chemicals are often introduced in aqueous solutions by using a cosolvent, the solubility enhancement for PAHs at low cosolvent volume fractions was also evaluated. Three cosolvents (dimethyl sulfoxide, ethanol, and acetone) were chosen and their volume fractions in water were between 0.2% and 2%. The enhancement of the aqueous solubility could be well explained quantitatively by using a log-linear cosolvency model. The measured values of cosolvency power at the range of volume fraction investigated (σ(0.02)) correlated very well with log K(ow) of the PAHs. The combination of the log-linear model and semiempirical relationships between σ(0.02) and log K(ow) would be useful for the prediction of the solubility enhancement of hydrophobic chemicals.

Investigation of Effects of the Cosolvent Methanol on the Apparent Solubility of a Suite of Chlorobenzenes Using Headspace Solid-Phase Microextraction (HS-SPME)

Cosolvent effects have historically been considered as negligible at cosolvent spiking concentrations below 1 %. Headspace solid-phase microextraction (HS-SPME) was used to determine the effect of the cosolvent methanol (MeOH) on apparent solubility of three chlorobenzenes (CBs) (1,2,4,5-tetrachlorobenzene, pentachlorobenzene, and hexachlorobenzene). All CBs exhibited a ln-linear decreasing relationship between cosolvent volume fraction and extracted mass. However, there were no statistical differences in measured headspace CB concentration at cosolvent additions of 1 % or less compared to controls. This study validated the use of MeOH volumes of 1 % and lower for batch studies using HS-SPME. Ninety-six hour incubation studies using 0.01 %, 10 %, and 100 % MeOH treatments demonstrated chemical losses from headspace vials through time. Declines were greatest for 0.01 % MeOH treatments and nonsignificant for vials containing 100 % MeOH. The silanization of vials using 5 % DCMCS was unsuccessful in reducing ...

Cosolvent flushing for the remediation of PAHs from former manufactured gas plants

Cosolvent flushing is a technique that has been proposed for the removal of hydrophobic organic contaminants in the subsurface. Cosolvents have been shown to dramatically increase the solubility of such compounds compared to the aqueous solubility; however, limited data are available on the effectiveness of cosolvents for field-contaminated media. In this work, we examine cosolvent flushing for the removal of polycyclic aromatic hydrocarbons (PAHs) in soil from a former manufactured gas plant (FMGP). Batch studies confirmed that the relationship between the soil–cosolvent partitioning coefficient ( K i ) and the volume fraction of cosolvent ( f c ) followed a standard log-linear equation. Using methanol at an fc of 0.95, column studies were conducted at varying length scales, ranging from 11.9 to 110 cm. Removal of PAH compounds was determined as a function of pore volumes (PVs) of cosolvent flushed. Despite using a high f c , rate and chromatographic effects were observed in all the columns. PAH effluent concentrations were modeled using a common two-site sorption model. Model fits were improved by using MeOH breakthrough curves to determine fitted dispersion coefficients. Fitted mass-transfer rates were two to three orders of magnitude lower than predicted values based on published data using artificially contaminated sands.

Tuneable mechanical properties in low molecular weight gels

The mechanical properties of gels are critical to the final targeted applications. Depending on the application, different properties may be required. Here, we show that the mechanical strength and ability to recover of gels formed using a low molecular weight gelator can be controlled by two independent factors (i) the volume fraction of co-solvent (in this case DMSO) in the system and (ii) the temperature cycle used. These differences correlate with the large scale structure of the network that is formed from the self-assembled fibres. This opens up the potential to prepare gels with very different properties at the same final conditions, allowing the effect of microstructure to be probed.

Effect of propylene glycol on ibuprofen absorption into human skin in vivo

The objective was to assess the impact of propylene glycol (PG), a common cosolvent in topical formulations, on the penetration of ibuprofen into human skin in vivo. Drug uptake into the stratum corneum (SC), following application of saturated formulations containing from 0 to 100% v/v PG, was assessed by tape-stripping. Dermatopharmacokinetic parameters, characterizing drug amount in and diffusivity through the SC, were derived. The solubility behavior of ibuprofen in PG-water mixtures was carefully evaluated, as were a number of other physical properties. Ibuprofen delivery depended on the level of PG in the vehicle, despite all formulations containing the drug at equal thermodynamic activity. PG appeared to alter the solubility of ibuprofen in the SC (presumably via its own uptake into the membrane), the effect becoming more important as the volume fraction of cosolvent in the formulation increased. In summary, tape-stripping experiments, with careful interpretation, can reveal details of a drug's bioavailability in the skin following topical application and may be used to probe the mechanism(s) by which certain excipients influence local drug delivery.

Solubility and sorption of petroleum hydrocarbons in water and cosolvent systems

The solubility and sorption of oil by uncontaminated clay loam and silt loam soils were studied from water and cosolvent/water solutions using batch techniques. The data obtained from the dissolution and sorption experiments were used to evaluate the applicability of the cosolvent theory to oil as a complex mixture. Aqueous solubility and soil-water distribution coefficients (K(d,w), L/kg) were estimated by extrapolating from cosolvent data, with a log-linear cosolvency model, to the volume fraction of cosolvent (f(c)) 0, and were compared with direct aqueous measurements. The extrapolated water solubility was 3.16 mg/L, in good agreement with the directly measured value of 3.83 mg/L. Extrapolated values of K(d,w) for the two soils were close to each other but consistently higher than the values from direct aqueous measurements, because of the presence of dissolved organic carbon (DOC). The partition coefficient (K(DOC)) between the DOC and the freely dissolved phase and the OC-normalized sorption coefficient (K(OC)) were determined. The average values of logKD(OC) and logK(OC) were estimated as 4.34 and 3.32, respectively, giving insight into the possibility of oil becoming mobilized and/or of the soil being remedied. This study revealed that the cosolvency model can be applied to a broader range of hydrophobic organic chemicals (HOCs) than has been previously thought. The results aided in a reliable determination of water solubility and sorption coefficients and provide information about the fate of oil in solvent-contaminated environment.

Development of a Two-Phase Cosolvent Washing-Fungal Biosorption Process for the Remediation of DDT-Contaminated Soil

A bench scale, two-phase soil washing-biosorption process was developed for the remediation of p,p′-DDT-contaminated soil (containing 990 and 7750 mg kg-1 of p,p′-DDT). Removal of p,p′-DDT from contaminated soil was achieved by washing the soil with low molecular weight primary alcohols (ethanol or 1-propanol). An improved efficiency of p,p′-DDT removal was observed with increasing C-chain length of the cosolvent and by increasing the cosolvent volume fraction. When 40 or 80% 1-propanol were used, greater than 93% of p,p′-DDT was desorbed from the respective soils. p,p′-DDT was partitioned from the cosolvent solutions using biomass of Cladosporium sp. strain AJR318,501 as the sorptivematrix. When studies were conducted using a cosolvent-recycling regime (with 80% 1-propanol) greater than 95% of p,p′-DDT was removed from Soil A (990 mg kg-1p,p′-DDT) and Soil B (7750 mg kg-1p,p′-DDT) with the majority of the desorbed organochlorine repartitioning onto the fungal biomass. Less than 2.4 μg mL-1p,p′-DDT was detected in the cosolvent wash solution of Soil A after 80 hr: potentially the cosolvent could be further reused to treat other soil. A higher concentration of p,p′-DDT was detected in the cosolvent wash solution of soil B after 120 hr (13.3 μg mL-1) indicating that the p,p′-DDT sorption sites on the fungal biomass were fully saturated.

In situ Remediation of DDT-contaminated Soil Using a Two-Phase Cosolvent Flushing-Fungal Biosorption Process

The effectiveness of cosolvent soil flushing and fungal biosorption for the remediation of p,p′-DDT-contaminated soil was evaluated usingpacked soil columns in order to simulate an in situ soil flushing technique. Greater than 95% of p,p′-DDT (940 mg kg-1) was desorbed from the soil by flushing with 40 or 80% 1-propanol. Increasing the cosolvent volume fraction increased the rate of p,p′-DDT removal from the soil, however, the extent of p,p′-DDT removal was not enhanced. A further enhancement in therate of p,p′-DDT removal was achieved by increasing the cosolventflow rate from 6 ml hr-1 to 12 ml hr-1 (pore water velocity from 18.9 to 37.8 cm hr-1). The desorbed p,p′-DDT was removed from cosolvent wash solutions by partitioning onto fungal biomass. Biosorption of p,p′-DDT resulted in low concentrations of the organochlorine (3.3 μg ml-1) remaining in thecosolvent effluent indicating that the cosolvent could be reused for further p,p′-DDT desorption. Using this technique, between 53 and 95 pore volumes were required to reduce p,p′-DDT concentrationsfrom 990 mg kg-1 to below Australian and New Zealand Environmentaland Conservation Council (ANZECC) guidelines (50 mg kg-1).

Solubilization by cosolvents: Establishing useful constants for the log–linear model

The purpose of this study was to develop constants for the log–linear cosolvent model, thereby allowing accurate prediction of solubilization in the most common pharmaceutical cosolvents: propylene glycol, ethanol, polyethylene glycol 400, and glycerin. The solubilization power ( σ) of each cosolvent was determined for a large number of organic compounds from the slope of their log–solubility vs. cosolvent volume fraction plots. The solubilization data at room temperature were either experimentally determined or obtained from the literature. The slopes of the nearly linear relationship between solubilization power and solute hydrophobicity (log K ow) were obtained by linear regression analysis for each considered cosolvent. Thus, knowing or calculating a compound's partition coefficient is all that is needed to predict solubilization.

Desorption of Pentachlorophenol from Soils Using Mixed Solvents

Desorption of pentachlorophenol (PCP) from contaminated soils in mixed solvents of water and ethanol was investigated using desorption isotherm experiments. The following cosolvent volume fractions of ethanol in the mixed solvent were considered: 0.03, 0.56, 0.79. 0.95, and 1.0. Three fractions of a synthetic soil (Edison soil) with approximately 1% organic matter were the main soils used in this study in addition to K-10 montmorillonite clay and Ottawa sand. The effect of soil organic matter and soil surface area on desorption in mixed solvents was evaluated. Analysis of desorption data revealed that PCP desorption increased with PCP solubility in mixed solvent up to 0.79, 0.95, and 0.56 fraction ethanol for Edison soil, K-10 montmorillonite, and Ottawa sand, respectively. Lower desorption of PCP from Edison soil in solvents with more than 0.79 fraction ethanol resulted from interactions between solvent and soil organic matter. For Edison soil, highest PCP desorption in all mixed solvents was obtained for the soil fraction with the smallest surface area. Desorption of PCP in mixed solvents containing more than 0.79 fraction ethanol was lower for soils with organic matter than for other soils.

Margules Equations Applied to PAH Solubilities in Alcohol−Water Mixtures

Solubilities of phenanthrene, pyrene, and perylene were determined in aqueous solutions containing either methanol, ethanol, or propanol at alcohol volume fractions ranging from zero to nearly 1, at 25 °C and atmospheric pressure. These data, and data from the literature on naphthalene were compared to various forms of two- and three-suffix Margules equations and UNIFAC predictions. For each solute−solvent−cosolvent (i.e., PAH−water−alcohol) system examined, the solubility (S) of each PAH increased with increasing alcohol volume fraction (v3). The UNIFAC model poorly estimated solubilities at cosolvent volume fractions near 0.5. Analysis of the data with various forms of the Margules equations shows that, in addition to solute−solvent and solute−cosolvent interaction terms, inclusion of solvent−cosolvent (i.e., water−alcohol) and solute−solvent−cosolvent interaction terms in the model improves predic tions, particularly at cosolvent volume fractions near 0.5. A simplified three-suffix Margules model is proposed, which includes terms for all these interactions and accurately estimates the experimental data with a consistent set of interaction parameters. All sets of interaction parameters involving solute molecules were regressed against each solute's respective log octanol−water partition coefficient, Kow. Solubilities of other PAH compounds in similar alcohol−water mixtures, obtained from the liturature, were estimated accurately with these relationships and knowledge of each solute's Kow value and enthalpy of fusion.

Organic Cosolvent Effects on Sorption Kinetics of Hydrophobic Organic Chemicals by Organoclays

Data obtained from batch kinetics sorption experiments for naphthalene and diuron using two organoclays [trimethylphenylammonium (TMPA)-clay and benzyldimethyltetradecylammonium (BDTDA)-clay] in aqueous and methanol−water systems were analyzed with a first-order one-site mass transfer model (OSMTM) to obtain kinetic parameters. The mass transfer coefficient (e) exponentially decreased as the sorption coefficient (Kp) increased, and a log-linear increase in e was observed with an increase in the volume fraction of cosolvent (f c) in the system. Regression equations relating e to f c, measured in mixed solvents, could be extrapolated to f c = 0 to obtain the coefficients in aqueous systems. The organic cosolvent effects on the sorption kinetics behavior of naphthalene and diuron depended on the sorbate structure, the cosolvent fraction, and the arrange ment of the exchanged quaternary alkylammonium ions in montmorillonite-clay interlayers.