Nanoparticles for Heavy Metal Removal from Drinking Water

The implementation of nanotechnology in drinking water treatment is a very promising field for applied research. A major part of this effort focuses on reducing the building units dimensions in the existing inorganic adsorbents used for the purification of water versus heavy metal species. The development of engineered nanoparticles has the potential to provide improved uptake efficiencies and sustainability if issues related to cost, technical incorporation and environmental safety will be overcome. We reviewed (1) the technical and economic conditions for potential implementation of inorganic nanoparticles as alternative adsorbents of heavy metals from drinking water, (2) the reported studies referring to the capture of heavy metals ionic forms by inorganic nanoparticles giving emphasis to those succeeding residual concentrations below the maximum contaminant level and (3) the indirect health and environmental risk related to the application of nanosized materials in a water treatment line. In particular, a separate section is devoted to the identification of an optimum nanoparticle profile that fits the unique characteristics of each class of emerging heavy metals with respect to the chemical affinity, charge interactions, aqueous speciation, redox reactions and ion-exchange processes. Importantly, in order to bridge fundamental research with the requirements of the technical and commercial sector dealing with water treatment plants, we introduce an evaluation path for the preliminary qualification of candidate nanoparticulate materials, based on a universal index which is derived by adsorption isotherms recorded under realistic conditions of application.