Functional organoclays for removal of heavy metal ions from water: A review

The presence of heavy metals in the environment is an issue of great concern because of their growing discharge, toxicity, and other adverse effects on the receiving water. Adsorption has been proven to be one of the best options for pollution control in water in which functional organoclays are prominent candidates for treating wastewater containing heavy metal ions. This review deals with comprehensive information on the application of functional organoclays (polymer-, silane coupling agent-, surfactant-, ionic liquid- and other organics based organoclays) for heavy metal ions uptake from aqueous solutions. The adsorption performances of various functional organoclays for anionic and cationic heavy metal ions, the influence of environmental conditions as well as the regeneration performances are discussed. A special focus is made on a detailed overview and comparison of the mechanisms (ion exchange, electrostatic attraction, complexation, redox, surface complexation and precipitation) associated with the characteristics of different functional organoclays for retention of heavy metal ions. Furthermore, this paper also states the limitations, challenges and development directions of functional organoclays, providing valuable insights for actual sewage purification. (C) 2021 Elsevier B.V. All rights reserved.