Application of inorganic chemically active membranes (ICAMs) for copper ion separation from acidic sulfate solutions

Inorganic ceramic membranes impregnated with organic chelation acid exhibit novel behavior as a separator. This study explores the feasibility of this separation technology for on-site hazardous waste reduction by selective extraction of toxic and/or valuable metal ions from aqueous waste streams by inorganic chemically active membranes (ICAMs). The model system studied was copper ion extraction from sulfate solution employing 2-hydroxy-5-nonyl- acetophenone oxime impregnated in α-alumina/silica membranes. An experimental evaluation of the ICAMs' performance is presented here. Data to calculate metal ion flux through the ICAMs were obtained with a rotating diffusion cell equipped with on-line UV-visible spectrophotometry. Flux was shown to increase with pH of feed solution and rotational speed, and suggests that both the chemical reaction rate and film diffusion influence the flux. Upon repeated impregnation and reuse of the same membranes, some form of deactivation occurred and the flux decreased to lower but stable values. Continuous membrane operation also was achieved for about 6 days with stable fluxes of 1.5 - 1.8 x 10^-6 gmol/cm² hr with the reimpregnated membranes. Even at the lower fluxes, the ICAMs were comparable to impregnated polymeric membranes and show promise for separation applications. These results indicate that inorganic ceramic membranes have the potential for on-site reduction and recovery of many toxic and valuable metal ions from waste streams.