Role of emulsifier in the extraction of gold(III) ions from aqueous solutions using the emulsion liquid membrane technique

Extraction of gold (III) ions from aqueous solutions by two types of emulsifier using the emulsion liquid membrane technique was investigated. Experimental results for the batch extraction of gold (III) ions using a surfactant liquid membrane technique are presented. A comparison was made between a synthetic commercial and a novel, naturally based, biodegradable emulsifier. The effects of various parameters such as emulsifier type, concentration of gold ions in the external phase, concentration of carrier, concentration of the internal phase reagents, pH of the external phase and the speed of agitation on the extraction rate were studied. Results showed that both types of emulsifiers have very good stability against both reducing-alkaline and acidic solutions and are suitable for this technique. The concentration of emulsifier in the membrane phase is critical and determines the stability, viscosity and the mass transfer resistance of the resultant emulsion. The results also showed that by proper selection of the extraction conditions, nearly all of the Au(III) ions present in a highly concentrated feed solution were extracted within a few minutes. It was found that the most effective parameters in the extraction of gold ion are pH, speed of agitation and concentration of the internal phase with a percentage of contribution of 65, 11 and 6.5, respectively, and the concentration of the carrier has the least effect with a contribution of 2.2% in final result.