Linear Solvation Energy Relationship of the Limiting Partition Coefficient of Organic Solutes between Water and Activated Carbon

Abstract

A linear solvation energy relationship has been found for 353 values of the limiting adsorption coefficients of diverse chemicals: log K = −0.37 + 0.0341Vi − 1.07β + D + 0.65P with R = 0.951, s = 0.51, n = 353, and F = 818.0, where Vi is the intrinsic molar volume; β is a measure of the hydrogen bond acceptor strength of the solute; D is an index parameter for the research group which includes the effects of the different types of carbon used, the temperature, and the length of time allowed for the adsorption equilibrium to be established; and P is an index parameter for the flatness of the molecule. P is defined to be unity if there is an aromatic system in the molecule or if there is a double bond or series of conjugated double bonds with no more that one non-hydrogen atom beyond the double bond and zero otherwise. A slightly better fit is obtained if the two-thirds power of Vi is used as a measure of the surface area in place of the volume term: log K = −1.75 + 0.227V 2/3 − 1.10β + D + 0.60P with R = 0.954, s = 0.49, n = 353, and F = 895.39. This is the first quantitative measure of the effect of the shape of the molecule on its tendency to be adsorbed on activated carbon.

QSAR Models To Predict Effect of Ionic Strength on Sorption of Chlorinated Benzenes and Phenols at Sediment–Water Interface

“…Many semi-theoretical models describing the QSARs have been proposed to predict the sorption parameters including the octanol-water partitioning coefficient, the LSE model, (Nirmalakhandan and Speece, 1993;Luehrs et al, 1996), the MCI model (Blum et al, 1994;Nirmalakhandan and Speece, 1988), and the solvophobic theory (Belfort et al, 1984). While utilising the above QSARs, it is hypothesised that the sorption coefficients normalised to the organic carbon fraction of the sediment (K exp oc ) values for pollutants in fact depend upon the background ionic strength of the system and the validity of this approach has been demonstrated by incorporating the ionic strength term into the three QSARs namely octanol-water partitioning coefficient model (Kow model), the LSE model, and the MCI model.…”

“…A multiple regression incorporating the ionic strength term into the Kow model yields the following equation and a correlation coefficient (r 2 ) of 0.57 (N ¼ 18): log K exp oc ¼ 0:006 þ 0:541 log K ow þ 1:09 IS LSE model. In the LSE model, the whole array of solvatochromic parameters (V i =100, p; a, and b) were obtained from Luehrs et al (1996) for all the pollutants used in this study excepting 1,4-chlorophenol which was calculated by the procedure given by Hickey and Passino-Reader (1991). The solvatochromic parameters for the various pollutants studied are as given in Table 2.…”

“…Carrying out a multiple Schwarzenbach et al (1993). b Values obtained from Luehrs (1996). c Values calculated as per the method given by Kier and Hall (1976).…”

“…Many semi-theoretical quantitative structure activity relationships (QSARs) have been proposed to parameterise sorption onto soils/sediments (Baker et al, 1997;Meylan et al, 1992), sorption onto activated carbon (Blum et al, 1994;Luehrs et al, 1996;Belfort et al, 1984), sorption onto wastewater solids (Dobbs et al, 1989), adsorption of organic vapours onto activated carbon (Urano et al, 1982;Nirmalakhandan and Speece, 1993;Prakash et al, 1994), dissolution of compounds (Kamlet et al, 1986;Lane and Loehrs, 1995;Speece, 1988, 1989;Dunnivent et al, 1992), Henry's law constants (Nirmalakhandan and Speece, 1988;Dunnivent et al, 1992;Nirmalakhandan et al, 1997;Brennan et al, 1998), chemical biotransfer (Dowdy et al, 1996), chemical toxicity (Blum and Speece, 1990;Xu and Nirmalakhandan, 1998); and octanolwater partition coefficients (Sablijic et al, 1993). It is well known that the physico-chemical interactions depend on chemical properties of the pollutant such as aqueous solubilities, octanol/water partition coefficients, or structural characteristics including substituted groups on the pollutant molecule, molar volume of the molecule, topology as well as the intrinsic properties like polarity and polarisability of the pollutant molecules (Westall et al, 1985;Kamlet et al, 1986).…”

“…Lately, more attention has been given to applications of QSARs to predict sorption parameters at the soil or sediment interface (Meylan et al, 1992) because such parameterisation can help in a variety of situations including prediction of local and regional impact of aquatic environment, understanding relative importance of fate (Baker et al, 1997) and transport processes in aquatic systems such as oceans, rivers, aquifers, and lakes, remediation of soils, sediments, and aquifers, bioaccumulation, biomagnification, toxicity to life forms, and bioavailability. Some of the most commonly used QSARs for prediction of sorption capacities at the soil-water interface include the octanol-water partitioning coefficient model (Means et al, 1980;Karickhoff, 1981;Piwomi and Banerjee, 1989;Chiou, 1983;Schwarzenbach et al, 1993), the Linear Solvation Energy model (Nirmalakhandan and Speece, 1993;Luehrs et al, 1996), Molecular Connectivity Indices model (Blum et al, 1994;Nirmalakhandan and Speece, 1988;Xu and Nirmalakhandan, 1998); the Solvophobic Theory (Belfort et al, 1984); and the combination of polarisability parameter, molecular connectivity index, and hydrogen bonding index model (Nirmalakhandan et al, 1997). All these QSARs have essentially tried to focus on several complex physico-chemical surface interactions including adsorption, absorption, ion exchange, pore diffusion, redox reaction, precipitation, dissolution, acid/base hydrolysis, formation of co-ordinated complexes giving rise to the polynuclear species (Weber et al, 1991;Banerji et al, 1993;Gao et al, 1998).…”