ABSTRACT
VERY often, removal of heavy metal cations from water and wastewater streams involves a scenario where only a trace concentration of the heavy metal ion (typically in the range of ppm) needs to be selectively removed in the presence of other competing nontoxic, nonregulated ions (e.g., Ca2+, Mg2+, Na+, etc.)- The case for selectivity is strong; removing only the trace contaminant constitutes an efficient and economic solution, but it is also a chal lenging proposition. Use of treatment processes that remove all ions-heavy metals and non toxic (e.g., solidification/stabilization, membrane filtration, precipitation, etc.)— invariably involve difficulties in justifying the associated costs. An additional problem relates to han dling the copious quantities of sludge produced, disposal of which is again an environmental issue and an economic issue. Organic ion exchange polymers allow the benefit of selective removal of heavy metal ions and can overcome the limitations described above. This method also opens the possibility of reusing the heavy metal ions.
