Fixed-bed adsorption of Cr(VI) onto chitosan supported on highly porous composites

Abstract

Abstract A highly porous composite was developed as a support for chitosan to provide dimensional stability for the continuous-flow adsorption of Cr(VI) in a fixed-bed column. The high-porosity adsorbent was prepared by incorporating polystyrene into a low-density polyethylene/agave blend to enhance the pore formation using azodicarbonamide as a blowing agent. The high porosity led to low mass transfer resistance for both: chitosan diffusion into the pores of the support, and also high diffusivity of the polluted solution during the adsorption. These findings were reflected in high adsorption capacity and fast kinetics observed in batch experiments which are critical parameters for continuous-flow operation. The effect of bed length, flow rate, and inlet concentration were evaluated in a fixed-bed system. The continuous-flow adsorption capacity of up to 9.7 mg/g represents a capacity of 82.6 mg/g of chitosan. A new parameter was introduced to determine if the column regeneration is convenient from an environmental point of view. From this analysis, it was observed that two cycles of the column regeneration were suitable.