Pollutants aqueous solubility

Another feature of the process is that the sorption capacity of type II organoclays is inversely related to the aqueous solubility of the NOCs (Chiou 1989). For example, the affinity of HDTMA-smectite for various phenols increases in the order phenol < chlorophenol < dichlorophenol < trichlorophenol since phenol is the most water-soluble while trichlorophe-nol is the most hydrophobic (Mortland et al. 1986, Lo et al. 1998). The relationship between the distribution (partition) coefficient in a type II organoclay and water-solubility is illustrated in Fig. 5 for a range of nonionic organic pollutants. 

Tester, D.J., Harker, R.J. (1981) Ground water pollution investigations in the Great Ouse Basin. Water Pollut. Control 80, 614—631. Tewari, Y.B., Martire, D.E., Wasik, S.P, Miller, M.M. (1982a) Aqueous solubilities and octanol-water partition coefficients of binary liquid mixtures of organic compounds at 25°C. J. Solution Chem. 11, 435 -45. 

The assessment of rate and distribution of environmental pollutants in various phases including air, water, and soil is important for the risk assessment of chemicals [48]. The partitioning of chemicals among different phases is usually assessed using a critical list of physical properties including vapor pressure (VP), aqueous solubility, ainwater partition coefficient, and octanol-water partition coefficient. 

Pollutants with high VP tend to concentrate more in the vapor phase as compared to soil or water. Therefore, VP is a key physicochemical property essential for the assessment of chemical distribution in the environment. This property is also used in the design of various chemical engineering processes [49]. Additionally, VP can be used for the estimation of other important physicochemical properties. For example, one can calculate Henry s law constant, soil sorption coefficient, and partition coefficient from VP and aqueous solubility. We were therefore interested to model this important physicochemical property using quantitative structure-property relationships (QSPRs) based on calculated molecular descriptors [27]. 

It must be noted that the partition coefficient is not the ratio of the pollutant solubilities in the two pure liquids. This change can result in significant differences, particularly with compounds of low aqueous solubility. The measurement of partition coefficients may be complicated by the involvement of other equilibrium processes such as pKa and pH values. For example, the following reaction shows the dissociation of a monoprotic organic acid ... 

Dichloromethane or methylene chloride is an Environmental Protection Agency priority pollutant. Its mode of human toxicity and carcinogenicity is described above. Dichloromethane has a high vapor pressure and a relatively high aqueous solubility of 150 mM (Dean, 1985), properties that contribute to its distribution in... 

Aliphatic hydrocarbons include straight chain and branched structures. Industrial solvents, petroleum hydrocarbons, and the linear alkyl benzene sulfonates (LAS) are the primary sources of aliphatic hydrocarbon pollutants. Many microorganisms utilize aliphatic hydrocarbons as carbon sources. Long-chain -alkanes are utilized more slowly due to the low bioavailability that results from their extremely low solubility in water. In contrast, short-chain rc-alkanes show a higher aqueous solubility. 

The most typical route for metal ion removal/ recovery from polluted aqueous media is precipitation (see Section 10.2). However, in some cases the target metal ion cannot be precipitated in a pure form because other metal ions may co-precipitate. Selective complexation can then be used to promote the solubilization of either the target ions or the accompanying ions. Here, the constant for metal complexation must be greater than the solubility product. (Note that in order for this comparison to be valid, one has to be aware of the differences in the units of the constants). For example, one can recover Ag... 

Suspended and bottom sediments are widely regarded as a sink for PCB s and other hydrophobic organic pollutants released Into aquatic systems. The mechanism commonly proposed to explain the affinity of PCB s for sediments Is equilibrium sorption or partitioning, which Is a function of the aqueous solubility of PCB Isomers and the attractiveness of the sedimentary matrix to PCB s (1-4). Field and laboratory studies Indicate that sedimentary organic matter plays a fundamental role In PCB-sedlment associations (5-12) and that humic substances are Important components of the sedimentary organic matrix for such associations (6,13-16). For example, Choi and Chen (O found that sedimentary PCB and DDT concentrations were linearly related to the humic acid content of sediments from Los Angeles Harbor. Fierce et al. (15) determined that humic acid could account... 

Ruehle T, Schneider H, Find J, Herein D, Pfaender N, Wild U, Schloegl R, Nachtigall D, Artelt S, Heinrich U (1997) Preparation and characterisation of Pt/A1203 aerosol precursors as model Pt-emissions from catalytic converters. Appl Catal B Environ 14 69-84 Schafer J, Hannker D, EckWdt JD, Stiiben D (1998) Uptake of traffic-related heavy metals and platinum group elements PGE by plants. Sci Total Environ 215 59-67 Speranza A, Leopold K, Maier M, Taddei AR, Scoccianti V (2009) Pd-nanoparticles cause Increased toxicity to kiwifruit pollen compared to soluble Pd. Environ Pollut (submitted) Sures B, Zimmermann S (2007) Impact of humic substances on the aqueous solubility, uptake and bioaccumulation of platinum, palladium and rhodium in exposure studies with Dreissena polymorpha. Environ Pollut 146(2) 444 51... 

Experimental measurements of solubility are influenced by many different factors, including the purity of the solute and solvent, presence of cosolvents, presence of salts, temperature, physical form of the undissolved solute, ionization state, and solution pH [18]. Consequently many different definitions of solubility are in common use in the published literature. Here we discuss the intrinsic aqueous solubility, Sg, which is defined as the concentration of the neutral form of the molecule in saturated aqueous solution at thermodynamic equilibrium at a given tanperature [18-20]. Intrinsic aqueous solubility is used to calculate dissolution rate and pH-dependent solubility in models such as the Noyes-Whimey equation [21] and the Henderson-Hasselbalch equation [22, 23], respectively. Prediction of the intrinsic aqueous solubility of bioactive molecules is of great importance in the biochemical sciences because it is a key determinant in the bioavailability of novel pharmaceuticals [1, 3, 24-26] and the environmental fate of potential pollutants [27, 28],... 

Empirical linear correlation analysis has also produced results that may be used in predicting the rates of FeS-mediated pollutant transformation based on pollutant thermodynamic or molecular properties. One study (77) performed linear correlation analysis of log kohs values for 8 halogenated aliphatic molecules with five molecular properties one-electron reduction potentials, lowest unoccupied molecular orbital (LUMO) energies, fi ee energies of formation of aqueous phase radicals formed upon one-electron reduction, gas-phase homo-[ytic bond dissociation enthalpies, and aqueous solubilities. Of these parameters, homolytic bond dissociation enthalpies (7)r.x values) were best correlated with log obs values for FeS reductive dechlorination (R =0.82). The correlation between log obs and 7)r x is illustrated in Figure 4. Another parameter shown... 

The translocation of BaP from roots to shoots should be low, due to BaP hydrophobicity (Figure 4), unless special molecules are produced by plants, able to increase the apparent aqueous solubility of hydrophobic pollutants, such as 2,3,7,8-TCDD-binding proteins, shown by Campanella and Paul (2000) for dioxin absorption by zucchini (Cucurbita pepo L.) may be B. curtipendula root exudates can enhance the acquisition of BaP, then accumulate it into their roots however, it could not translocate great amounts of BaP into their stems (Figure 4A). 

Campanella, B. Paul, R. (2000). Presence, in the rhizosphere and leaf extracts of zucchini Cucurbita pepo L.) and melon (Cucumis melo L.), of molecules capable of increasing the apparent aqueous solubility of hydrophobic pollutants. Int J Phytoremed, 2, 145-158. 

MetaUic ions are precipitated as their hydroxides from aqueous caustic solutions. The reactions of importance in chlor—alkali operations are removal of magnesium as Mg(OH)2 during primary purification and of other impurities for pollution control. Organic acids react with NaOH to form soluble salts. Saponification of esters to form the organic acid salt and an alcohol and internal coupling reactions involve NaOH, as exemplified by reaction with triglycerides to form soap and glycerol,... 

The rat LD qS are 13, 3.6 (oral) and 21, 6.8 (dermal) mg/kg. Parathion is resistant to aqueous hydrolysis, but is hydroly2ed by alkah to form the noninsecticidal diethjlphosphorothioic acid and -nitrophenol. The time required for 50% hydrolysis is 120 d ia a saturated aqueous solution, or 8 h ia a solution of lime water. At temperatures above 130°C, parathion slowly isomerizes to 0,%diethyl 0-(4-nitrophenyl) phosphorothioate [597-88-6] which is much less stable and less effective as an insecticide. Parathion is readily reduced, eg, by bacillus subtilis ia polluted water and ia the mammalian mmen to nontoxic 0,0-diethyl 0-(4-aminophenyl) phosphorothioate, and is oxidized with difficulty to the highly toxic paraoxon [511-45-5] diethyl 4-nitrophenyl phosphate d 1.268, soluble ia water to 2.4 mg/L), rat oral LD q 1.2 mg/kg. 

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