Ultrafiltration characteristics of colloid solutions containing oxyethylated methyl dodecanoate, hexadecyltrimethylammonium bromide and selected phenols as pollutants Beata Korzystka, Hanna Adamczak, Anna Sobczyn´ ska, Jan Szymanowski  Institute of Chemical Technology and Engineering, Poznan´ University of Technology, Pl. Skl  odowskiej-Curie 2, 60-965 Poznan´, Poland Received 13 February 2002; accepted 10 June 2002 Abstract The effect of hexadecyltrimethylammonium bromide upon ultrafiltration of oxyethylated methyl dodecanoate solutions and separation of phenol, 4-nitrophenol and 4-methylphenol was investigated. The permeate fluxes and the resistance of the secondary layer (SL) were determined and the effect of the surfactant discussed. The rejection of the phenols, distribution and binding constants were determined and interpreted. It was found that colloidal systems containing mixtures of oxyethylated methyl dodecanoates and hexadecyltrimethylammonium bromide are advanta- geous systems for recovery of phenols by micellar enhanced ultrafiltration (MEUF). An addition of CTAB causes only a slight increase in the resistance of the SL and a slight decrease in the ultrafiltration flux. This negative effect is fully compensated for by improved rejections of phenols, observed in mixed surfactant systems. # 2002 Published by Elsevier Science B.V. Keywords: Micellar enhanced ultrafiltration; Oxyethylated methyl dodecanoates; Hexadecyltrimethylammonium bromide; Phenols 1. Introduction Solvent extraction is widely used to recover and separate various organic and inorganic substances. Recovery of copper from oxide ores and flotation tailings [1] and separation of aromatics from petroleum products [2] can be given as examples of high tonnage processes in which solvent extrac- tion is successfully used. Solvent extraction is also widely used to recover low tonnage products. Solvent extraction can be considered as an economical separation process that permits recov- ery, separation and concentration of the solute at ambient temperatures. However, the classical ex- traction also shows an important drawback, resulting from the use of organic solvents, usually high-boiling hydrocarbons which in some cases, due to solubility problems, are bound to contain some amounts of toxic aromatics.  Corresponding author. Fax: /48-61-313-349 E-mail address: jan.szymanowski@put.poznan.pl (J. Szymanowski). Colloids and Surfaces A: Physicochem. Eng. Aspects 212 (2003) 175 /183 www.elsevier.com/locate/colsurfa 0927-7757/02/$ - see front matter # 2002 Published by Elsevier Science B.V. PII:S0927-7757(02)00298-4