Clay-hydrogel nanocomposites for adsorptive amputation of environmental contaminants from aqueous phase: A review

Water, being the crucial feature of our planet, the contamination of which is a grave matter of concern globally. Elimination of tenacious pollutants from the aquatic phase is indispensable for the sustainability of this planet. Adsorptive sequestration of pollutants is a highly cherished way owing to its design simplicity, economic feasibility and, higher efficacy than various reported treatment methods. Amidst the ample range of adsorbents employed for an environmental cause, clay-hydrogel nanocomposites (CHN) are emerging as an enticing materials platform for wastewater treatment owing to their high sorption capacity, affinity, environmental viability, tailorable physiochemical characteristics, and better reusability. The presence of various functional groups in the polymer chain -OH, -COOH, -NH2 along with the adsorptive potential of clays validate them as a hot spot sorbent. This review initially summarizes the synthetic methodologies of various clay-hydrogel nanocomposites and then their utilization in the seizure of pollutants from the aquatic realm. The removal mechanism which governs the uptake of pollutant on the clay-hydrogel nanocomposites has been thoroughly reviewed which illustrated that electrostatic interaction, hydrogen bonding, and complexation are the prime ways to sequester dyes and metals on CHN. Discussion on isotherm and kinetic models along with thermodynamic study is also provided. Regeneration efficiency of CHN was also discussed demonstrating HCl to be potent desorbing agent than various acids and organic solvents. Finally, the future perspective for the advancement of CHN in the direction of modern technological facets is also detailed out.