Recovery of nickel ions by supported liquid membrane (SLM) extraction

Heavy metal ions very often appear in high concentrations in all kind of effluents giving rise to hazards of pollution because of their high toxicities and wide environmental spreading. This paper deals with the recovery of nickel ions from effluents resulting from the metal finishing industry. In the first stage, commercial extractants were screened by means of conventional extractions. Combining organophosphoric or organophosphinic acids with oximes lead to enhanced Ni(II) extraction. The influence of the type of extractant was investigated as well as other critical parameters such as concentration and pH of the feed. In the second stage, the most promising combinations were tested with the supported liquid membrane (SLM) technology in a lab-scale environment. Those experiments can be divided into two classes when the membrane type is considered: experimental work with flat sheet membranes (Celgard 2400: 0.0062 m2) and with hollow fiber modules (Celgard: 0.4–1.7 m2). A mixture of LIX 860-I and Cyanex 302 was most successful for the selected operation characteristics, especially for the plating industry. Permeations were calculated for various concentrations of extractant and experimental runs were undertaken with real effluents. At the end, an ageing test was started to check the stability of the membrane and the evolution of the flux in function of time.