SOLID-PHASE HEAVY-METAL SEPARATION USING COMPOSITE ION-EXCHANGE MEMBRANES

Selective removal of heavy metals from sludges or soil is a challengin g problem because the heavy metals constitute a small fraction (usuall y <5%) of the solid phase, the rest being a background of innocuous no n-toxic materials which are not important from a regulatory viewpoint. However, the non-toxic background materials may interact with the hea vy metals through generation of high buffer capacity, ion-exchange, co mplexation, etc., thus compounding the problem. This study explores th e feasibility of using composite ion-exchange membranes under such unf avorable conditions. This paper also reports on aspects of tailoring t he chemistry within the sludge reactor to get optimum results.