Highly cost-effective and high-strength hydrogels as dye adsorbents from natural polymers: chitosan and cellulose

Search for cost-effective and high-strength dye adsorbents has become an urgent problem in wastewater treatment. Natural polymers such as chitosan and cellulose are low-cost and can be fabricated as hydrogels for dye adsorption, but these hydrogels usually have weak strength. Here, novel high-strength and highly cost-effective hydrogels with a high capacity of dye adsorption were prepared with chitosan and cellulose. The chitosan/cellulose hydrogels could be knotted and twisted without fracture and could be restore rapidly after compression. These features showed that the hydrogels had good elasticity, high strength and excellent resilience. Also, the incorporation of rectorite into hydrogels could increase the thermal stability and strength of composite hydrogels. Subsequently, the adsorption capacity of hydrogels to Congo Red was investigated: chitosan was the main functional material for adsorption and rectorite participated in dye adsorption as well, but cellulose supported the structure. Furthermore, the adsorption process fitted closely with the Freundlich model, and was best described by a pseudo-second-order kinetic model. The hydrogels were biodegradable and could be easily collected after adsorption. These environmental friendly hydrogels could be promising candidates for dye removal in the future.