Solubility Of Hydrophobic Organic Compounds Research Articles

Development of novel experimental and modelled low density polyethylene (LDPE)-water partition coefficients for a range of hydrophobic organic compounds

Knowledge about partitioning constants of hydrophobic organic compounds (HOCs) between the polymer and aqueous phases is critical for assessing chemical environmental fate and transport. The conventional experimental method is characterized by large discrepancies in the measured values due to the limited water solubility of HOCs and other associated issues. In the current work, a novel three-phase partitioning system was evaluated to determine accurate low-density polyethylene (LDPE)-water partition coefficients (KPE-w). By adding sufficient surfactant (Brij 30) to form the micellar pseudo-phase within the polymer/water system, the KPE-w values were obtained from a combination of two experimentally measured values, that is, the micelle-water partition coefficient (Kmic-w) and the LDPE-micelle partition coefficient (KPE-mic). The method presented here is capable of shortening the equilibration time to half a month, and avoiding defects of the traditional method with respect to directly measured aqueous phase concentrations. Herein, the KPE-w values were determined for HOCs with little errors. Meanwhile, based on the 120 experimental KPE-w data, several in silico models were also developed as valid extrapolation tools to estimate missing or uncertain values. Analysis of the underlying solubility interactions in the nonionic surfactant micelles were investigated, providing additional support for the reliability of the proposed method.

Analysis of Non-Ionic Surfactant Triton X-100 Using Hydrophilic Interaction Liquid Chromatography and Mass Spectrometry.

It is well known that surfactants increase the solubility of hydrophobic organic compounds and cause adverse environmental effects. The removal of these compounds from the contaminated soil or ground-water is particularly difficult due to their water soluble feature. In this work, an ultra-high performance hydrophilic interaction liquid chromatographic method was developed for the separation of oligomers of Triton X-100 octylphenol-polyethoxylate non-ionic surfactant. Liquid chromatography-mass spectrometry (LC-MS) was used to identify the Triton X-100 compounds. There was a 44 mass unit difference between two adjacent peaks that is the molar mass of one ethylene oxide group (–CHCHO–). A quadratic retention model was applied for the estimation of retention of the examined non-ionic surfactant and the optimization of gradient elution conditions. The optimized method was suitable for the baseline separation of 28 Triton X-100 oligomers in five minutes.

In situ Raman spectroscopy investigation of the solubility and dissolution mechanism of 1,2‐dichlorobenzene in hot compressed water in a fused silica capillary reactor

Hot compressed water (HCW), with its unique properties, is regarded as a promising solvent for industrial applications. A number of methods to measure the solubility of hydrophobic organic compounds (HOCs) in HCW have been reported. However, these methods were conducted in large‐scale stainless‐steel reactors, and few included an in situ study regarding the dissolution mechanism of HOCs in HCW during the solubility determination process. In this study, a fused silica capillary reactor in combination with Raman spectroscopy was applied to investigate phase changes, determine the solubility, and study the dissolution mechanism of 1,2‐dichlorobenzene in HCW. The total dissolution process of 1,2‐dichlorobenzene in HCW was observed under a microscope, and the images were recorded continuously using a digital camera. Raman spectroscopy was used to confirm the homogeneity of the 1,2‐dichlorobenzene solution during dissolution. The solubility of 1,2‐dichlorobenzene increased from 35.9 to 85.7 mg g−1 in water with increasing temperature from 256.7 to 294.1 °C. Furthermore, the dissolution mechanism of 1,2‐dichlorobenzene in HCW is proposed based on the Raman spectra of 1,2‐dichlorobenzene and water during the dissolution process in the fused silica capillary reactor. The breakage of the fully hydrogen‐bonded (tetrahedral) configuration and the consequent change in the static dielectric constant of water are deemed to be compelling reasons for the high solubility of 1,2‐dichlorobenzene in HCW. Our experimental method exhibits great potential for determining the solubility of HOCs in HCW and for investigating their dissolution behavior and dissolution mechanism at elevated pressure and temperature conditions. Copyright © 2017 John Wiley & Sons, Ltd.

Applying UNIFAC-based models to predict the solubility of solids in subcritical water

This work explores the capabilities of UNIFAC-based models to predict the solubility of different solid solutes in subcritical water as a function of temperature. The original UNIFAC, its modified (Dortmund) version and the A-UNIFAC model, which explicitly includes association effects between groups, are applied to calculate the solubility of solid compounds in subcritical water in the temperature range 298–500 K. The comparison between the three models is carried out using polycyclic aromatic hydrocarbons (PAHs) as test substances and for which reliable physical properties and experimental solubility data are available in the literature. The results obtained indicate that modified UNIFAC (Dortmund) provides the best representation of the aromatic compounds’ solubility as a function of temperature. In addition, the application of the A-UNIFAC model confirms the hypothesis that a decrease in the level of association between the subcritical water molecules (in accordance with the dielectric constant decrease with temperature), greatly improves the solubility of hydrophobic organic compounds.

The electrodeless discharge lamp: a prospective tool for photochemistry: Part 6. Photochemistry of valerophenone and 4-nitroanisole in high-temperature water

Two temperature-sensitive model photochemical reactions, the Norrish Type II reaction and photochemical nucleophilic aromatic substitution on 4-nitroanisole by the hydroxide ion, carried out in high-temperature water (100–200 °C) in a pressurized vessel under microwave heating, are reported. The observed chemoselectivity and the ability to increase the solubility of hydrophobic organic compounds in this environmentally friendly solvent are promising results for prospective green (photo)chemical applications.

Effect of molecular structures on the solubility enhancement of hydrophobic organic compounds by environmental amphiphiles

Amphiphilic molecules, such as humic substances and surfactants, are known to increase the apparent aqueous solubility of hydrophobic organic compounds (HOCs) in the aqueous phase because of their molecular structures, which consist of hydrophilic and hydrophobic moieties. In this study, we examined the effect of the structures of humic acid and HOCs on the sorption of four polycyclic aromatic hydrocarbons (PAHs) and an organochlorine pesticide, p,p'-DDT, to humic acid. As the number of aromatic rings was increased, the extent of solubility enhancement of PAHs by humic acid was increased. Although p,p'-DDT was more hydrophobic than pyrene in this study, the extent of solubility enhancement of p,p'-DDT by humic acid was lower than that of pyrene because of the molecular structures of the solutes. Anionic surfactants with and without aromatic rings also were studied for comparison, and the dianionic surfactant with two benzene rings exhibited similar results with humic acid, unlike the surfactants without and with one benzene ring. The results from this study indicate that bulky molecules, such as p,p'-DDT sorbed with more difficulty to the aggregates of amphiphiles with larger molecules, such as humic substances and the dianionic surfactants.

Influence of Rhamnolipids and Triton X-100 on the Biodegradation of Three Pesticides in Aqueous Phase and Soil Slurries

The effect of surfactants on the biodegradation of trifluralin and atrazine (by Streptomyces PS1/5) and coumaphos (by degrading consortia from a contaminated cattle dip) in liquid cultures and soil slurries was tested at different concentrations of a rhamnolipid mixture (Rh-mix) and Triton X-100 (TX-100). The extent of trifluralin biodegradation in liquid culture was improved at high concentrations of both surfactants. The extent of atrazine degradation dropped in the presence of either surfactant. Coumaphos biodegradation improved slightly at Rh-mix dosages >3000 microM; however, it was readily inhibited by TX-100 at amounts above the critical micelle concentration. In soil slurries, the extent of both trifluralin and atrazine biodegradation was higher in Hagerstown A (HTA) soil than in Hagerstown B (HTB) soil and was not significantly affected by the presence of either surfactant. The onset of trifluralin biodegradation was retarded at higher concentrations of surfactants. In the absence of surfactant, up to 98% of coumaphos in both soil slurries was transformed. At increasing dosages of Rh-mix, the onset of coumaphos biodegradation was retarded, but the removal efficiency of the pesticide increased. Rh-mix and TX-100 depletion was observed during Streptomyces PS1/5 growth in liquid cultures. Rh-mix concentration also decreased during coumaphos biodegradation, whereas TX-100 concentration was not affected. These results suggest that surfactants, added for the purpose of increasing the apparent water solubility of hydrophobic organic compounds, may have unintended effects on both the rate and extent of biodegradation of the target compounds if the surfactants can also be degraded by the microorganisms in the system.

Polycations. 4. Synthesis and antihydrophobic effect of polycationic strings

Two categories of polycationic “strings” have been synthesized and investigated for their effect on the aqueous solubility of hydrophobic organic compounds (benzene and 4-bromotoluene, the latter discussed here). Polycationic “strings” are compounds in which cationic sites (quaternary ammonium sites) are incorporated into the covalent structure along a linear chain with free-floating associated anions. The categories are: 1) defined length chains consisting of quaternized dabco units connected by intervening lengths of methylene groups, terminating with ω-alkanol units, and 2) α,ω-dimethylaminoalkane units quaternized with chain extending ω-alkanol units. The observed antihydrophobic effect depends on the total charge, the length of the charge-intervening linkages, and the terminating groups.

Bioenhancement of soil microorganisms in natural surfactant solutions. iii. effect of hexachlorobenzene

A plant‐based natural surfactant extracted from fruit pericarps of Sapindus mukorossi was tested to remediate contaminated soils. Natural surfactants are shown to increase the solubility of hydrophobic organic compounds (HOCs) significantly and recover them from soil. Bioenhancement of typical soil microorganisms in natural surfactant solutions under aerobic and anaerobic conditions was investigated in our earlier studies. These surfactant solutions can readily serve as both carbon and energy sources and degrade considerably. In this study, a chlorinated organic, hexachlorobenzene (HCB) is used as a model contaminant to study the effect of contaminants on the bioenhancement. HCB at a concentration of 1 mg/l which is about 20 times that of HCB aqueous solubility was used for both aerobic and anaerobic cultures. Aerobic and anaerobic biodegradation experiments were conducted in 250 ml Erlenmeyer flasks and 125 ml serum bottles respectively. HCB at the concentration tested did not affect the growth of microorganisms significantly under both oxygen rich and anoxic conditions. HCB neither underwent any biotransformation nor adsorb to the biomass. The presence of basal salt media enhanced the biological growth under both the conditions.

Effect of surfactant film on solubility of hydrophobic organic compounds in fog droplets

A HOCs-enrichment reactor was developed to investigate the elevated solubility of n-octane, a surrogate of the hydrophobic organic compounds (HOCs), in the artificial fog droplets containing sodium dodecyl sulfate (SDS), a surrogate of the natural surfactants. The enrichment of n-octane is strongly related to the SDS concentration. In comparison with the solubility of n-octane based on the Henry's law for the ideal aqueous solution, the enrichment factors of n-octane in the fog droplets are between 27.2 and 1.87, depending on the SDS concentration (2.85 × 10 −3 to 5.15 × 10 −5 M). In addition, when SDS concentration is below the specific concentration, 1.03 × 10 −4 M, the larger fog droplets show higher enrichment effect than the smaller fog droplets do. Moreover, we present an enrichment model to describe the micro-states of the n-octane molecules partitioning in the SDS organic film at the air/fog interface and the SDS monomers inside the fogwater. The experimental results can easily be expounded and discussed by use of this model.