Extraction of Gold(III) with a Nonionic Surfactant Poly(oxyethylene) 4-Nonylphenyl Ethe r from Hydrochloric Acid Solution

Abstract

Two procedures have been described for extraction of gold(III) with a nonionic surfactant from hydrochloric acid solution. The surfactant used was poly(oxyethylene) 4-nonylphenyl ether with an average number of oxyethylene units 7.5 (PONPE-7.5). One procedure utilizes the cloud point of the surfactant; at a temperature above the cloud point, a surfactant-rich phase is separated from aqueous solution, and gold is extracted into this phase. In this procedure, 30 g of 0.1 mol·kg^-1 of hydrochloric acid solution containing 30-3000 μg of gold and 0.3 g of PONPE-7.5 was heated at 40°C in a water bath for 10 min and then centrifuged. The centrifuge tube was cooled at about 10°C for 1 min, and the aqueous phase (upper layer) was removed, leaving the extract (about 2 g) in the tube. One and half gram of 20% w/w PONPE-20 solution was added to make the extract clear, and water was added to make the solution 5.00 g. Absorbance of this solution was measured at 335 nm to determine gold. Ninety-five% of gold was extracted. Effect of foreign metals is shown in Table 1. Another procedure involves extraction of gold with a 1, 2-dichloroethane solution of PONPE-7.5. In this procedure, 25 cm'of 2 mol·kg^-3 hydrochloric acid solution containing 50-5000 μg of gold was shaken with 5 cm' of 5% w/v PONPE-7.5 in 1, 2-dichloroethane for 5 min. The extract was diluted to 10 cm³ and the absorbance was measured at 325 nm. Ninety-seven to 98% of gold was extracted. Effect of foreign metals is shown in Table 2.