Study of adsorption behavior of malachite green on polyethylene glycol micelles in cloud point extraction procedure

Cloud point extraction (CPE) was carried out to extract malachite green (MG) from aqueous solution and shrimp samples using a series of polyethylene glycol (PEG) surfactants: PEG10000, PEG6000, PEG2000 and PEG600. The adsorption mechanism between PEG micelles and MG molecules was studied. The data of equilibrium concentrations and adsorption amounts in the four PEG–MG systems followed the Langmuir type isotherm. On some assumptions, a developed Langmuir isotherm was used to calculate the feed surfactant concentration required for the removal of MG up to an extraction efficiency of 90%. The calculated PEG concentrations were used in CPE process, and other influence factors on phase behavior were investigated. Under the optimal conditions, recoveries of MG were 82.16–92.41% in aqueous solution and 78.16–86.54% in shrimp samples.