Various flotation techniques for metal ions removal

The importance of the flotation process to the economies of the entire industrial world is considered to be enormous; it is a gravity separation method, which is based on the idea of applying rising gas bubbles as the transport medium. Usually following the selective attachment of bubbles to particles, those solids are transferred from the body of water to the surface, where foam is formed. Hence, as opposed to settling, flotation is a solid-liquid separation technique that is applied to particles of which the density is lower, or has been made lower, than the liquid they are in, by collectors and modifiers. Thus, flotation initially originated from the field of mineral processing but for many years, various particulate solids, in addition to minerals, have been extracted from water by using this effective process. These flotation applications mainly include the treatment of water and wastewater, mainly containing heavy metals, being the scope of the present. The techniques followed were that of ion, precipitate and/or sorptive flotation, including the biosorptive one, summarizing to a dispersed-air flotation - microfiltration hybrid unit. Mention with certain examples will be given to the flotation separation (dispersed or dissolved-air) and recovery of the following pollutants, as selectivity was often the focus: Zn, Cd, Cu, Ni, Fe, Mn, Mo, P, As, Si. (C) 2016 Elsevier B.V. All rights reserved.