Adsorption mechanisms of hydrogels for heavy metal and organic dyes removal: A short review

Heavy metal and organic dyes produced in modern industrialization development have polluted the natural resources human live by due to their adverse effects on all biological organisms. Developing effective, economical and friendly strategies to tackle environmental pollution has been a hotspot in recent years, among which adsorption of chemical pollutants from water has been considered of utmost importance. Hydrogel-based adsorbents with three-dimensional porous structures and versatile functional groups have become the first choice, whose adsorption involves several mechanisms. In this perspective article, electrostatic interactions, hydrogen bonding, π-π interactions, ion exchange, surface complexation and coordination/chelation were introduced in detail to provide an overview for a better understanding of the action mechanisms of various hydrogels. Combining two or more mechanisms is advantageous to gain great adsorption capacity, which could be achieved via physical or chemical modification of hydrogels. This short review aims to provide theoretical guidance to design and prepare hydrogels for applications in water treatment.