Among various reactions which metal sulfides can undergo in the reducing environment, the lattice exchange reaction was examined in a attempt to selectively remove heavy metal ions contained in the Fe-Coagulants acid solution. We have examined Zeta potential along with pHs to investigate surface characteristics of FeS(s). As a result of this experiment, zero point charge(ZPC) of FeS is pH 7 and zeta potential which resulted from solid solution reaction between Pb(Ⅱ) and FeS(s) is similar to that of PbS(s). Solubility characteristics of FeS(s) is appeared to that dissolved Fe(Ⅱ) concentration increased in less than pH 4, and also increased with increasing heavy metal concentration. Various heavy metal ions(Pb(Ⅱ), Cu(Ⅱ), Zn(Ⅱ)) contained in Fe-coagulants acid solution were removed selectively more than ninety-five percent in the rang of pH 2.5∼10 by FeS(s). From the above experiments, therefore, We could know that the products of reaction between heavy metal ions and FeS(s) are mental sulfide such as PbS(s), CuS(s) and ZnS(s).