Dried ground formaldehyde-treated peanut skins, white ash bark, and So. Wisconsin red maple bark are efficient substrates for removal of many heavy metal ions from waste streams, but possible interference by common light metal cations has never been determined. The influence of Ca2+, Mg2+, or Na+ on the removal of the heavy metal ions Pb2+, Cu2+, Cd2+, and Zn2+ by the above substrates was studied in both batch and packed-column experiments. It was found that Pb2+ and Cu2+ were minimally affected by the presence of these light metal ions in solution, while the uptake of Cd2+ and Zn2+ was significantly reduced. Calcium ion produced the greatest effect of the light metals tested.