Cloud point extraction of gold (III) ion with polyoxyethylene nonyl phenyl ether

Abstract

The cloud point extraction (CPE) of gold (III) ion with polyoxyethylene nonyl phenyl ether (oxyethylene=9) was investigated. A solution of polyoxyethylenated nonionic surfactant exhibits cloud point phenomena as a result of less hydration at elevated temperature with subsequent decrease in aqueous solubility. Above the cloud point temperature, the solution seperates into two phases : the surfactant-rich phase and the water-rich phase. Any analytes that can interact with and bind the micellar entity will become concentrated in the surfactant-rich phase upon heating the solution over CP. The CPE methodology can be utilized for separating gold (III) ion from other metals because of the selectivity of gold ion into the micellar of PONPE-9. In this study, the effect of equilibration time, ratio of PONPE-9 to gold, settling temperature, and pH of the solution on extraction efficiency were investigated. The results obtained had been applied to design the process schemes for recovering gold (III) ion from other metal ions. The process consists of two batches of CPE. The first batch was performed at pH 3 for extracting gold (III) ion from other metal ions. The second was conducted at pH 7 for separating gold ion from surfactant. Metallic gold can be precipitated out. Greater than 63% of gold with 98% purity can be recovered. Moreover, the thermodynamic equations for describing the interaction between gold (III) ion and PONPE-9 were proposed. The comparative of that interaction in the solutions is in the order of pH 3> pH 10> pH 7 which is in accordance with the percent extraction of gold obtained by CPE.