Scaling Up Cloud Point Extraction of Aromatic Contaminants from Wastewater in a Continuous Rotating Disk Contactor. I. Effect of Disk Rotation Speed and Wastewater to Surfactant Ratio

Abstract

When an aqueous solution containing nonionic surfactant is heated above the cloud point, the solution separates into two phases. A micellar‐rich phase, or coacervate, and a micellar‐dilute phase are formed. Aromatic contaminants present in the original solution tend to solubilize into the micelles in the coacervate phase and concentrate there—this is the basis of the separation process known as cloud point extraction (CPE). In this study, CPE was scaled up from single‐stage, batch experiments to multistage continuous operation in a rotating disk contactor (RDC) to remove the aromatic contaminants, toluene and ethylbenzene, from wastewater. A nonionic surfactant, t‐octylphenolpolyethoxylate, was utilized as the separating agent. The concentration of solutes in the coacervate phase increased as agitator speed, wastewater to surfactant solution flow rate ratio, and degree of alkylation of the aromatic solutes increased. The overall volumetric mass‐transfer coefficient (K a) and the number of transfer unit (NTU) in the RDC increased with increasing rotation speed of the rotor disk. In this pilot scale, multistage continuous operation, the toluene partition ratio and concentration of toluene in the coacervate phase are two times greater than that observed in a single‐stage, equilibrium batch experiment with the same initial conditions.