Removal of chelated heavy metals from aqueous solution: A review of current methods and mechanisms

Water contamination with heavymetal ions and organic compounds such as citrate, ethylenediaminetetraacetic acid, tartrate, pharmaceuticals, surfactants and natural organic matter, is a serious problem in the natural environment. Although many methods have been effectively applied to the removal of heavy metal complexes from aqueous solution, there is a lack of information available on the mechanisms, advantages and disadvantages of these various methods. This review summarizes the various treatment methods applied to the removal of heavymetal complexes, with a summary of the mechanisms of action and recent research progress. The methods reviewed in detail include electrolysis, membrane separation, adsorption, precipitation, replacement-coprecipitation, TiO2 photocatalysis and Fenton oxidation-precipitation, with the advantages and disadvantages of each method discussed. Furthermore, the heavy metal complex removal mechanisms are analyzed comprehensively. Results show that the adsorption method exhibited unique merits, showing much promise for future development. Finally, this review comprehensively analyzes future prospects and developments in methods for removal of chelated heavy metals. (C) 2019 Elsevier B.V. All rights reserved.