Precious metals enrichment from wastewater solution using emulsion liquid membrane process

Abstract

Recovery of precious metals including palladium and silver from liquid waste solutions is vital, in order to sustain the resources and to conserve the environment from hazardous materials, particularly heavy metals. Many methods were studied for precious metal recovery, but constrained by several limitations. One of the promising methods for industrial wastes treatment and precious metals recovery is emulsion liquid membrane (ELM). This method able to selectively separate and concentrate the target metals through a very thin layer of liquid membrane with large surface area. In this study, an attempt was made to recover palladium and silver from liquid waste solution using bis (2,4,4-trimethylpentyl) monothiophosphinic acid (Cyanex 302) as a mobile carrier. Several important parameters affecting the ELM recovery process such as extractant/carrier and stripping agent concentration, phase treatment ratio between emulsion and feed phase were studied. The results showed that at optimum process conditions of 0.03 M Cyanex 302 carrier concentration, 1.0 M of thiourea in 1.0 M of H2SO4(1.0 M acidic thiourea) stripping agent concentration and 1:4 treat ratio, almost 100% of silver was extracted and recovered with 11 times of enrichment. Whilst for the palladium treatment, almost 100% of palladium was extracted and recovered with 3 times enrichment in the receiving phase at 0.2 M of Cyanex 302, 1.0 M acidic thioureaof striping agent and 1:3 treat ratio. Therefore, it can be concluded that the ELM system is very promising and has high potential in removal and recovery of precious metals.