Solid phase heavy metal separation using composite ion-exchange membranes

ABSTRACT Selective removal of heavy metals from sludges or soil is a challenging problem because the heavy metals constitute a small fraction (usually <5%) of the solid phase, the rest being a background of innocuous non-toxic materials which are not important from a regulatory viewpoint. However, the non-toxic background materials may interact with the heavy metals through generation of high buffer capacity, ion-exchange, complexation, etc., thus compounding the problem. This study explores the feasibility of using composite ion-exchange membranes under such unfavorable conditions. This paper also reports on aspects of tailoring the chemistry within the sludge reactor to get optimum results.