Preparation and adsorption properties of magnetic chitosan composite adsorbent for Cu 2+ removal

Water pollution caused by Cu2+ ions poses a significant threat to the ecosystem and human health, hence the development of highly cost-effective, highly operation-convenient and highly efficient natural polymer-based adsorbents is urgently needed. To overcome this serious problem, a novel cost-effective magnetic chitosan composite adsorbent (CsFeAC) was prepared with magnetic macroparticles and highly porous activated carbon carrier using the sol-gel method. Several methods, namely SEM, BET, FTIR, XRD, TGA and VSM, were applied to characterize the adsorbent. Batch tests were conducted to investigate Cu2+ adsorption properties of CsFeAC at different pH values, contact time, initial Cu2+ concentrations and temperatures. The adsorption fits better to the Langmuir isotherm and follows the pseudo-second-order model, suggesting that it is a monolayer adsorption and the rate-limiting step is the chemical chelating reaction. The saturated adsorption capacity is found to be 216.6 mg/g. Thermodynamics analysis suggests that the adsorption process is endothermic, with increasing entropy and spontaneous in nature. BET and XRD tests confirm that the higher specific surface area and lower crystallinity of CsFeAC significantly improve the absorption capacity and rate. FTIR spectra reveal that the amino and hydroxyl groups play an important role in the chelating adsorption. The supermagnetic property of CsFeAC facilitates its easy separation characteristic. Further recycling experiments show that CsFeAC still retains 95% of the original adsorption following the 5th adsorption-desorption cycle. All these results demonstrate that CsFeAC is a promising recyclable adsorbent for removing Cu2+.