Toxic metals exist in the effluents of many industrial operations. The impact of chemical speciation was stressed during various flotation applications for metal separation from the effluent. Examples of recent investigations include the removal of arsenic ions by iron oxides, speciation studies of chromium ions, the selective separation of molybdate anions (and verification of extant phosphate, arsenate, and silicate impurities), the recovery of tungstates, the biosorption of metals (i.e., the selective removal of copper), the use of pyrite and other solid wastes as adsorbents, and the classical case of mixed sulfide mineral flotation (pyrite oxidation, use of surface complexation modeling, etc.). Thermodynamic equilibrium diagrams and software packages were employed to interpret the removal mechanism involved.