Implementing nanoparticles for competitive drinking water purification

The implementation of nanotechnology in drinking water treatment is a very promising field for applied research. A major part of this effort focuses on the reduction of the dimensionality of the conventional cost-effective adsorbents that have been successfully used for decades. 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 are overcome. In this study, we review: (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 regulation limit and (3) the indirect health and environmental risk related to the application of nanosized materials in a water treatment line. A part of the review is devoted to the identification of an optimum nanoparticle profile that complies with the unique characteristics for each and every heavy metal 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.