The interfacial characteristics between various heavy metals and hydrous FeS were investigated. Heavy metals which have lower sulfide solubilities than FeS undergoes the lattice exchange reaction when these metal ions contact FeS in the aqueous phase. For heavy metals which have higher sulfide solubilities than FeS, these metal ions adsorb on the surface of FeS. Such characteristic reactions were interpreted by the solid solution formation theory. The presence of ligand such as EDTA reduced largely metal removal efficiency due to formation of metal-ligand complex in the solution. In an attempt to elucidate the interfacial characteristics, zeta potential of the hydrous FeS in the absence and in the presence of various metal ions were measured and analyzed.