FLOTATION TECHNIQUES IN WATER TECHNOLOGY FOR METALS RECOVERY: THE IMPACT OF SPECIATION

Abstract

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.

ACKNOWLEDGMENTS

Thanks are due to Mr. Martin Lehmann, Environmental Engineer, for his help with Figure 7, to Dr. Zhao You-Cai (Tongji University, Shanghai, China) for his help in adsorbing colloid flotation, and to Dr. Ian Ch. Hancock (University Newcastle-upon-Tyne, UK), coordinator, and the other colleagues of the European Union Environment research programme, BioElecDetox, for the constructive collaboration.