Biopolymer-Based Nanocomposites for Removal of Cr(VI) from Aqueous Systems: A Review

Hexavalent chromium Cr(VI) has emerged as a contaminant of prime concern for the environmentalists because of its improper disposal by tannery, dye, and electroplating industries. Adsorption is the most exploited method for its removal from industrial wastewater because of its high removal efficiency even at low Cr(VI) concentration, minimal sludge, and ease of regeneration. In recent years, several adsorbents of biological origin such as plants, algae, fungi, and bacteria have been explored for Cr(VI) remediation. This review comprehends the recent studies involving usage of biopolymer-based nano-composites with respect to its adsorption mechanisms, adsorption capacities, isotherms, and kinetics. The conventional abiotic and biotic techniques for removal of Cr(VI) are also discussed with a comparative insight of their adsorption capacity and removal efficiency. Nano-biocomposites integrate the functional properties of both nanoparticles and biopolymers, which make them efficient biosorbents. Nano-biocomposites offer a large surface area, reduced particle loss, minimal particle agglomeration on the surface, and high stability. Common kinetic models among the nano-biocomposites, and various equilibrium models are also analyzed to understand the mode of adsorption and associated factors. These materials are mostly found to follow monolayer adsorption with ion exchange, electrostatic interaction, and surface complexation as major players in the process.

Automated summary

Hexavalent chromium Cr(VI) has become a major concern for environmentalists due to improper disposal by certain industries. Adsorption is a widely used method for removing Cr(VI) from industrial wastewater, and biopolymer-based nano-composites have shown promising results as efficient biosorbents. This review summarizes recent studies on the adsorption mechanisms, capacities, isotherms, and kinetics of these nano-composites. The conventional abiotic and biotic techniques for Cr(VI) removal are also discussed, along with a comparison of their adsorption capacity and efficiency. The analysis suggests that monolayer adsorption with ion exchange, electrostatic interaction, and surface complexation are the main mechanisms involved in the adsorption process.