Removal of phenols from aqueous streams by the cloud point extraction technique with oxyethylated methyl dodecanoates as surfactants.
New oxyethylated methyl dodecanoates with average degrees of oxyethylation (n) ranging between 5 and 14 (denoted OMD-n) were considered as nonionic surfactants for the removal of phenol, 4-methylphenol, and 4-nitrophenol from aqueous streams by the cloud point extraction technique. The cloud point (denoted CP) strongly increases with the average degree of oxyethylation n but is independent of OMD-n concentration, except at low concentration (i.e., < 10 g.L-1). CP can be related to the surfactant hydrophilicity by the following equation: CP(degree C) = 20.27 x HLBG - 245.8 (above 10 g.L-1 and in the absence of electrolyte), where HLBG refers to the OMD-n hydrophile-lipophile balance in Griffin's scale. The presence of electrolyte such as NaCl strongly decreases the cloud point [delta CP/delta [NaCl] approximately -(9 +/- 1) degrees C-M-1]. Many parameters influence the extraction of phenols in OMD-n-rich phases, including the characteristics of phenols (hydrophobicity, hydrogen-bond acidity, hydrogen-bond basicity, etc.), the average degree of oxyethylation of OMD-n (i.e., n), the concentration of electrolyte, the settling temperature (Tset), and overheating (delta T = Tset - CP). The distribution coefficients typically range between 20 and 100. Finally, the kinetics of the separation process is limited by the slow coalescence of the fine droplets of surfactant-rich phase formed above CP.
Materna
K
K
Poznan University of Technology, Institute of Chemical Technology and Engineering, Pl. Sklodowskiej-Curie 2, 60-965 Poznan, Poland.
Milosz
I
I
Miesiac
I
I
Cote
G
G
Szymanowski
J
J
D055598:Chemical Phenomena; D002627:Chemistry, Physical; D007700:Kinetics; D007848:Laurates / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry*; D013501:Surface-Active Agents / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014876:Water Pollution / Q000517:prevention & control
D007848:Laurates; D010636:Phenols; D013501:Surface-Active Agents; D014874:Water Pollutants, Chemical