Solubility Of Volatile Organic Compounds Research Articles

KOH activated pine tree needle leaves biochar as effective sorbent for VOCs in water

The removal of volatile organic compounds (VOCs) from water using KOH-activated pine tree needle leaves biochar is considered a cost effective and efficient process. In this study, pine tree needle leaves were mixed with 0, 50, 100 and 200% (KOH weight/feedstock weight) of KOH, respectively. Then, the mixture was pyrolyzed at 500 degree celcius for 6 hrs. The adsorption characteristics of 10 VOCs to the biochar were tested. The results indicated that the removal efficiency of the KOH activated biochar was highest in 100% KOH-biochar. The VOC removal efficiencies of 50% and 200% KOH activated biochar were similar and the 0% KOH activated biochar showed the lowest VOC removal. The FTIR results showed that increasing the amount of KOH seemed to enhance the formation of various functional groups, such as -OH, -C=C, -O. The adsorption strength of 10 VOCs to the KOH activated biochar seemed to be increasing by the increase of the solubility of VOCs. This may suggest that the adsorption is taking place in hydrophilic sites of the biochar surface. The KOH activated pine tree needle leaves biochar can be an effective sorbent for VOCs removal in water and 100% KOH mixing seemed to provide better sorption capacity.

Study on the synergistic effect of UV/Fenton oxidation and mass transfer enhancement with addition of activated carbon in the bubble column reactor

For the UV/Fenton treatment of waste gas, low solubility of volatile organic compounds (VOCs) was a significant factor of limiting gas–liquid mass transfer and thus restricted the removal efficiency. In this study, synergistic effect of UV/Fenton oxidation and mass transfer enhancement with addition of activated carbon (AC) was observed through a drastic improvement of n-octane removal in a bubble column reactor. Firstly, the effect of AC on mass transfer was investigated. Result revealed that the addition of AC could change bubble behavior and largely enhance the mass transfer efficiency (volumetric mass transfer coefficient (kLa) increased from 0.0057 to 0.14 s−1 as 0–0.1% AC was added) due to the particle shuttle effect. Then AC was introduced into the UV/Fenton reaction system, and the removal efficiency of n-octane had been remarkably improved (maintained above 50% in 60 min with addition of 0.04% AC, compared with below 10% in 20 min for the UV/Fenton alone). Moreover, we comprehensively detected the concentration of residual reactants, intermediates, final products and hydroxyl radicals in the gas and liquid phase. Results indicated that addition of AC could mildly and stably generate hydroxyl radicals (10−8 M), and the mass balance showed that the mineralization efficiency had increased from 42.4% to 57.9%. For theoretical calculations, the value of the cooperation factor raising from 0.5 to 11.7 in 40 min could offer direct evidence for confirming the synergistic effect. Finally, the reaction pathways of n-octane in UV/Fenton or AC-UV/Fenton were proposed. It can be induced that the latter ones were more likely to first break the CC bond and then oxidize into small molecules acids or CO2.

Nanoporous Semicrystalline Syndiotactic Polystyrene with Sulfonated Amorphous Phase, for a Fast and Efficient Removal of VOC Pollutant Traces From Water

SummarySyndiotactic polystyrene films and aerogels with nanoporous crystalline phase and sulfonated amorphous phase have been prepared and characterized. The nanoporous nature of the crystalline phase confers to these materials a high solubility of volatile organic compounds (VOCs) from aqueous solutions even at low VOC concentrations while the sulfonation of the amorphous phase enhance the VOC sorption kinetics. These combined properties make these materials particularly interesting for a potential use as a sorption medium to remove traces of pollutants from water. Different aspects relative to the preparation, the structure and the transport properties of these innovative polymeric materials are described.

Solubility of Organics in Triethylene Glycol: Phase Equilibrium Modelling Using the Dortmund and LYNGBY Modified UNIFAC Models

 Abstract—This work is an attempt to predict the solubility of 60 volatile organic compounds (VOCs) in triethylene glycol aimed at thermodynamically testing the suitability of this solvent as an absorbent for the selected organics. The VOC main groups studied were alkanes, alkenes, alkynes, aldehydes, carboxylic acids and alcohols. The Modified UNIFAC Dortmund and Lyngby models were to study the required phase equilibrium as a function of temperature and composition. Triethylene glycol was found to be suitable for the absorption of low molecular weight aldehydes, alcohols and carboxylic acids. Generally, the infinite dilution activity coefficients computed in this study were low (below 100) indicating that the polymeric solvent studied in this work gave favourable phase equilibrium compared to water, the common industrial solvent. The solubility of VOCs was also found to decrease with increase in solute molecular weight. Compared with literature findings, the Dortmund performed better than the Lyngby procedure. However both models failed to accurately predict phase equilibrium behaviour. The authors therefore agree with literature findings that a specialised group interaction needs to be created for this solvent in the UNIFAC models in order to satisfactorily predict activity coefficients for the studied binary interactions.

Selection of Ionic Liquids for Enhancing the Gas Solubility of Volatile Organic Compounds

A systematic thermodynamic analysis has been carried out for selecting cations and anions to enhance the absorption of volatile organic compounds (VOCs) at low concentration in gaseous streams by ionic liquids (ILs), using COSMO-RS methodology. The predictability of computational procedure was validated by comparing experimental and COSMO-RS calculated Henry's law constant data over a sample of 125 gaseous solute-IL systems. For more than 2400 solute-IL mixtures evaluated, including 9 solutes and 270 ILs, it was found that the lower the activity coefficient at infinite dilution (γ(∞)) of solutes in the ILs, the more the exothermic excess enthalpy (H(E)) of the equimolar IL-solute mixtures. Then, the solubility of a representative sample of VOC solutes, with very different chemical nature, was screened in a wide number of ILs using COSMO-RS methodology by means of γ(∞) and H(E) parameters, establishing criteria to select the IL structures that promote favorable solute-solvent intermolecular interactions. As a result of this analysis, an attempt of classification of VOCs respect to their potential solubility in ILs was proposed, providing insights to rationally select the cationic and anionic species for a possible development of absorption treatments of VOC pollutants based on IL systems.

Supercritical extraction of volatile organic components from polyethylene pellets

This paper evaluates the feasibility of extracting volatile organic compounds (VOCs) from polyethylene pellets via contact with supercritical fluids. Stagnant carbon dioxide (CO2) or stagnant ethane above their critical points contacted stagnant pellets. Then, a quick depressurization step vented the gases, and the pellets were analyzed for volatiles content. Moderately high temperatures (60°C) appear to be necessary for an effective devolatilization. At 36°C, diffusion limitations dominate, and the extraction performance is insensitive to the pressure and to the chemical nature of the supercritical fluid. At 60°C, ethane could extract more volatiles than CO2, indicating that the mutual solubility of VOCs and extraction fluids is an important factor. Up to a 90% reduction of the initial volatile content resulted after a 3-h contact with CO2 in multiple extractions in which pure CO2 periodically replaced VOC-laden CO2. A similar VOC reduction level resulted using ethane in a single extraction (i.e., without replacing the used ethane).

Reversibly enhanced aqueous solubilization of volatile organic compounds using a redox-reversible surfactant

Surfactant-enhanced remediation (SER) is an effective method for the removal of volatile organic compounds (VOCs) from contaminated soils and groundwater. To reuse the surfactant the VOCs must be separated from the surfactant solutions. The water solubility of VOCs can be enhanced using reversible surfactants with a redox-acive group, (ferrocenylmethyl)dodecyldimethylammonium bromide (Fcl2) and (ferrocenylmethyl)tetradecanedimethylammonium bromide (Fcl4), above and below their critical micelle concentrations (CMC) under reducing (I +) and oxidative (I 2+) conditions. The CMC values of Fcl2 and Fcl4 in I + are 0.94 and 0.56 mmol/L and the solubilization of toluene by Fcl2 and Fcl4 in I + for toluene is higher than the solubilization achieved with sodium dodecyl sulfate, cetyltrimethylammonium bromide and Trition X-114. The solubilization capacity of the ferrocenyl surfactants for each tested VOCs ranked as follows: ethylbenzene > toluene > benzene. The solubilities of VOCs by reversible surfactant in I + were 30% higher than those in I 2+ at comparable surfactant concentrations. The effects of Fcl4 concentrations on VOCs removal efficiency were as follows: benzene > toluene > ethylbenzene. However, an improved removal efficiency was achieved at low ferrocenyl surfactant concentrations. Furthermore, the reversible surfactant could be recycled through chemical approaches to remove organic pollutants, which could significantly reduce the operating costs of SER technology.

Effect of surfactant and oil additions in the biodegradation of hexane and toluene vapours in batch tests

The biological treatment of gaseous emissions of hydrophobic volatile organic compounds (VOCs) results in low rates of elimination partially because of the low solubility of VOCs in water. Recently, the use of two‐phase partition bioreactors (TPPBs) was proposed to increase the bioavailability and consequently the elimination capacities of this kind of VOC. In the present study, TPPBs operating in a batch feed mode were tested for biodegradation of hexane and toluene vapours with a microbial consortium. The results obtained were compared with single‐phase systems (control experiments). The liquid phase used was silicone oil (organic phase) with the surfactant Pluronic F‐68. Experiments were named F1 and F2 for one and two phases, respectively, and F1S and F2S when the surfactant was included. The maximum specific rates (Srates) of hydrocarbon consumption for hexane and toluene were 539 and 773 mghydrocarbon/(gprotein·h), respectively. For both substrates, the systems that showed the highest Srates of hydrocarbon consumption were F2 and F2S. In experiment F1S the surfactant Pluronic F‐68 increased the solubility of hydrocarbons in the liquid phase, but did not increase the Srates. The maximum percentages of mineralization were 51% and 72% for hexane and toluene, respectively. The results showed that simultaneous addition of silicone oil and surfactant favours the mineralization, but not the rate of biodegradation, of toluene and hexane vapours.

Solubility of volatile organic compounds in polymers: Effect of polymer type and processing

In this paper, the vapour phase calibration method (VPC) is applied to determine the solubility of three volatile organic compounds at 30.0 °C in 13 polymers (headspace concentrations in contact with the polymer from 0.044 to 0.241 mol/m 3 for dimethyl sulfide, 0.0015 to 0.0133 mol/m 3 for trichloroethylene and 3.19 × 10 −4 to 2.47 × 10 −3 mol/m 3 for toluene). In this way, the influence of polymer type, penetrant type and polymer processing, i.e. adding additives and vulcanisation, on the solubility could be investigated. The polymer type and the penetrant's condensability proved to have the largest influence on the solubility. Polymer processing from base polymer to end product has in some cases no effect on the solubility and leads to a decreased solubility in other cases. No increase in solubility after polymer processing was observed. For the rubbery polymer/vapour penetrant combinations, a linear relationship at 30 °C and diluted concentrations (ln( Sp 0 T c 2 ) = −3.070( χ( T c/ T) −2) + 28.761) with an R 2 = 0.941 and n = 36 could be observed. S is the solubility coefficient, p 0 the penetrant saturated vapour pressure, χ the Flory–Huggins interaction parameter and T and T c are the temperature and the penetrant critical temperature, respectively.

QSPR analysis of air-to-blood distribution of volatile organic compounds

Quantitative structure property relationship (QSPR) models for the prediction of human blood:air partition coefficient (log K blood) of volatile organic compounds (VOCs) has been developed based on the linear heuristic method (HM) and non-linear radial basis function neural networks (RBFNNs). Molecular descriptors that are calculated from the structures alone were used to represent the characteristics of the compounds. HM was used both to pre-select the whole descriptor sets and to build the linear model. RBFNN was performed to obtain more accurate models. Both the linear and the non-linear models can give very satisfactory prediction results: the correlation coefficient R was 0.964 and 0.979, and the root-mean-square (RMS) error was 0.3303 and 0.2542 for the whole data set, respectively. The prediction result of the non-linear model is better than that obtained by the linear model. In addition, this paper provides an effective method for predicting log K blood from its structures and gives some insight into the structural features related to the solubility of VOCs in human blood.

Solubility of volatile organic compounds in aqueous ammonia solution

The Ostwald solubility coefficient, L of 17 volatile organic compounds (VOCs) from the gas phase into water and dilute aqueous ammonia solutions was determined by the equilibrium partitioning in closed system-solid phase micro extraction (EPICS-SPME) method at 303 K and at 0–2.5 mol dm −3 ammonia concentrations. Ammonia increased the solubility of all VOCs nearly linearly, but to a different extent. The difference in the solubility values in aqueous ammonia solutions ( L mix) compared to pure water ( L) is explained on the basis of a Linear Solvation Energy Relationship (LSER) equation made applicable for solvent mixtures, log L mix - log L = x ( ( s NH 3 - s H 2 O ) π 2 H + ( a NH 3 - a H 2 O ) Σ α 2 H + ( b NH 3 - b H 2 O ) Σ β 2 H + ( v NH 3 - v H 2 O ) V x ) . s NH 3 - s H 2 O , a NH 3 - a H 2 O , b NH 3 - b H 2 O , v NH 3 - v H 2 O are the differences of solvent parameters, x is the mole fraction, π 2 H is the solute dipolarity–polarizability, Σ α 2 H is the effective hydrogen bond acidity of the solute, Σ β 2 H is the effective hydrogen bond basicity of the solute and V x , the McGowan characteristic volume. The most significant term was v, the phase hydrophobicity. The solubility behavior was explained by the change in structure of the aqueous solution: the presence of ammonia reduces the cavity effect. These findings show that the presence of compounds such as ammonia, frequently observed in environmental waters, especially wastewaters, affect the fugacity of VOCs, having consequences for the environmental partitioning of VOCs and having technical consequences towards wastewater treatment technologies.

Temperature dependence of Henry's law constant in an extended temperature range.

The Henry's law constants H for chloroform, 1,1-dichloroethane, 1,2-dichloropropane, trichloroethene, chlorobenzene, benzene and toluene were determined by the EPICS-SPME technique (equilibrium partitioning in closed systems--solid phase microextraction) in the temperature range 275-343 K. The curvature observed in the ln H vs. 1/T plot was due to the temperature dependence of the change in enthalpy delta H0 during the transfer of 1 mol solute from the aqueous solution to the gas phase. The nonlinearity of the plot was explained by means of a thermodynamic model which involves the temperature dependence of delta H0 of the compounds and the thermal expansion of water in the three-parameter equation ln (H rho TT) = A2/T + BTB + C2, where rho T is the density of water at temperature T, TB = ln(T/298) + (298-T)/T, A2 = -delta H298(0)/R, delta H298(0) is the delta H0 value at 298 K, B = delta Cp0/R, and C2 is a constant. delta Cp0 is the molar heat capacity change in volatilization from the aqueous solution. A statistical comparison of the two models demonstrates the superiority of the three-parameter equation over the two-parameter one ln H vs. 1/T). The new, three-parameter equation allows a more accurate description of the temperature dependence of H, and of the solubility of volatile organic compounds in water at higher temperatures.

Plasma-grafting of fluoroalkyl methacrylate onto PDMS membranes and their VOC separation properties for pervaporation

A polydimethylsiloxane (PDMS) membrane was improved by graft polymerization of 1H,1H,9H-hexadecafluorononyl methacrylate (HDFNMA) by plasma, which had the effect of increasing the selectivity for volatile organic compounds (VOCs). The use of an easy quantitative analysis for the pervaporation through plasma-grafted PDMS membranes was investigated. The degrees of grafting on the inside and reverse side of the grafted PDMS membranes were lower than on the surface. Only part of the HDFNMA sorbed into the PDMS membrane was grafted onto the PDMS membrane. The relationship between the feed concentration and the permeate concentration was observed to be linear. The pervaporation through the grafted PDMS membrane could be used for easy quantitative analysis. The solubility of VOCs for the grafted PDMS membrane was high when compared with the solubility for the PDMS membrane. The grafted PDMS membrane that had high VOC concentrations of the sorbed solution showed an excellent separation performance. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1835–1844, 1999

Evaluation of a Continuous Composite Sampler for Volatile Organic Compounds in Water

The high volatility and low water solubility of volatile organic compounds (VOCs), make the collection of representative samples difficult. The standard grab sampling method only gives information of that moment in time when the sample is taken. When the composition of VOCs is varying, continuous composite sampling will give a more representative sample. However, no thorough evaluation of its use for VOCs has been reported. The use of an automatic continuous composite sampler for the analysis of VOCs in water was studied. The causes and magnitude of the VOCs losses during the sampling process were determined. Adsorbent cartridges were used to trap the VOCs escaping from solution during the sampling process. Sorption phenomena occurring on the containers and/or tubings were also evaluated. Sorption losses were much more significant than volatilization losses. The results indicate that a modified version of this sampler can be an alternative for the long term sampling of water for VOC analysis.