Cloud point extraction of toluene from wastewater using nonionic surfactants : effect of temperature and surfactant structure

Abstract

The clouding phenomenon of a nonionic surfactant solution occurs when the solution is heated above the cloud point temperature. Above the cloud point, the turbid solution separates into two phases, viz. micellar-rich or coaccervate phase, and micellar-poor or dilute phase. When an organic solute is present in the system, the organic compound tends to be solubilized and concentrated in the coavcervate phase. This phenomenon can be applied to extract organic solute from an aqueous solution, which is called coacervate phase extraction or cloud point extraction. The aim of this work is to study the effects of operating temperature and surfactant structure on the cloud point extraction of toluene from wastewater. Two types of nonionic surfactants, which are selected to use in this work, are alkylphenol ethoxylates (APE) and alcohol ethoxylates (AE). In order to study the temperature effect, the operating temperatures are varied from 30, 40, 50 and 60C for APE surfactants and 60, 70 and 80C for AE surfactants. To study the effect of surfactant structure, the alkyl chain length and numbers of ethylene oxide group of these nonionic surfactants are varied. The results show that more than 80% and 70% of toluene can be extracted by using APE and AE surfactants respectively. As predicted, extraction efficiency increases with increasing temperature, but decreases with increasing amount of ethylene oxide. In contrast to the assumption, extraction performance decreases with increasing alkyl chain length.