Separation of VOCs from coacervate phase of alcohol ethoxylates surfactant by vacuum stripping

Abstract

Coacervate phase extraction or cloud point extraction (CPE) is a surfactantbased separation technique that uses concentrated nonionic surfactant to extract organic compounds from contaminated water. To make this process economically feasible, the spent nonionic surfactant should be recycled and reused. Co-current vacuum stripping is suggested for this purpose since foaming and flooding are minimized and eliminated. In this study, Tergitol 15-S-7 (C₁₁.₁₅H₂₃. ₃₁ O(CH₂CH₂O)₇. ₃H), the secondary alcohol ethoxylate (AE), is selected since AE are environmental friendly and biodegradable to harmless compounds, while the conventional nonionic surfactant, alkyl phenol ethoxylate (APE) is suspected to cause endocrine disruption. Two major types of volatile organic compounds (VOCs); aromatic and chlorinated hydrocarbon are selected as contaminants. The volatilization and solubilization of VOCs in coacervate solution are reported in terms of apparent Henry’s law constant (Happ), and solubilization constant (Ks). The hydrophobic properties of the VOCs are described by using an octanol-water partition coefficient (KoW). The results show that, as Kow increases, Ks also increases whereas Happ of the VOCs are significantly decreased. Furthermore, the efficiency of vacuum stripping column to remove VOCs out from their coacervate phase system are investigated in term of VOCs removal (%) and the overall liquid phase volumetric mass transfer coefficient, Kxa (mol/cm³min). For both aromatic and chlorinated hydrocarbon series; as Kow increases, the percentage of VOCs removal and Kₓa decrease due to the effect of hydrophobicity of solute.