Cosolvency and sorption of hydrophobic organic chemicals

Abstract

Sorption of hydrophobic organic chemicals (HOCs) by two soils was measured from mixed solvents containing water plus completely miscible organic solvents (CMOSs) and partially miscible organic solvents (PMOSs). The utility of the log-linear cosolvency model for predicting HOC sorption from solvent mixtures was evaluated. Cosolvent effects of PMOSs on HOC solubility and sorption were compared. Nonpolar PMOSs (e.g., toluene, p-xylene, and TCE) have low aqueous solubilities and when present either as a cosolvent/ cosolute in the aqueous phase or as a separate liquid phase do not significantly influence HOC sorption by soils. In contrast, polar PMOSs (e.g., nitrobenzene and o-cresol) have sufficiently high aqueous solubilities that significant decreases in HOC sorption can be measured. The presence of a CMOS increases the PMOS solubility which, in turn, is reflected in increased solubility and decreased sorption of HOCs. Results presented suggest that water-PMOS and sorbent-PMOS interactions need to be considered in predicting the cosolvency of a polar PMOS.

Enhanced anaerobic biodegradation of BTEX-ethanol mixtures in aquifer columns amended with sulfate, chelated ferric iron or nitrate

“…In addition, high ethanol concentrations (>10% v/v) expected initially near the source could exert a co-solvent effect that enhances BTEX solubility and migration (Da Silva & Alvarez 2002;Powers et al 2001b;Rao et al 1990). Therefore, ethanol may hinder BTEX natural attenuation, which could result in longer BTEX plumes and a greater risk of exposure (Ruiz-Aguilar et al 2002b).…”

Determinação do coeficiente de distribuição (Kd) de benzo(a)pireno em solo por isotermas de sorção

“…Denomina-se efeito de cosolvência o efeito causado por um determinado solvente orgânico sobre a solubilidade e sorção de compostos orgânicos hidrofóbicos. Rao et al 23 afirmaram que com o aumento do volume de solvente orgânico utilizado em uma mistura de solvente binária, há um aumento da solubilidade dos contaminantes orgânicos hidrofóbicos e diminui a sorção desses compostos ao solo. Além disso, cosolventes também podem alterar a natureza hidrofóbica da fração orgânica do solo, aumentando o teor de carbono orgânico dissolvido na fase solução, alterando desta forma todo o comportamento de contaminantes hidrofóbicos no solo.…”

Lab Testing and Field Implementation of Soil Flushing

“…Assuming the contaminant partitions between NAPL and aqueous phases: Similar to the log-linear cosolvency effect on solubility, the equilibrium sorption coefficient of hydrophobic organic compounds was also observed to decrease log-linearly in the same manner (Brusseau et al, 1991;Rao et al, 1985;Rao et al, 1990): Eq. 3.17 where K N,m and K N,w are the partition coefficients between NAPL and water (subscript N,w), and between NAPL and water/cosolvent mixture (subscript N,m) respectively.…”