Film-like chitin/polyethylenimine biosorbent for highly efficient removal of uranyl-carbonate compounds from water

Abstract

Uranium contamination in groundwater has been increasingly reported, while biosorbents for the decontamination attracts growing attention because of their distinct advantages of abundant raw materials and eco-friendliness. Herein, a film-like chitin/polyethylenimine biosorbent (CH-PEI) was prepared and employed in the removal of uranyl-carbonate compounds from water. Fourier transform infrared spectra, element analysis, scanning electron microscopy/energy dispersive X-ray spectroscopy, N2 adsorption-desorption isotherms and X-ray photoelectron spectroscopy were used to characterize the biosorbent. Besides, thermodynamic calculation and various batch experiments were conducted to investigate the adsorption performances of CH-PEI for uranyl removal from carbonate solution. The results showed that the biosorbent possessed a unique hierarchically porous structure and a high nitrogen content. The batch experiments exhibited that it obtained the maximum adsorption capacity at pH = 6. Notably, CH-PEI could reach sorption equilibrium within 4 h at the initial concentration of 50 mg/L. The maximum adsorption capacity were 247.04 mg/g and 1023.74 mg/g at the initial concentrations of 50 mg/L and 300 mg/L. The kinetics and isotherm data were well fitted by pseudo-second-order and Langmuir models. It could remove 98.9% of uranium in the simulated groundwater. The biosorbent showed fast regeneration, good structural stability and reusability in 5 cycles. Furthermore, the adsorption mechanism was confirmed to be anion exchange and electrostatic attraction between nitrogen species and uranyl-carbonate complexes through FT-IR and XPS analysis. Considering its low costs, high efficiency and easy collection, CH-PEI would be a promising biosorbent for uranium removal from groundwater. This study provides a potential technique for uranium removal using chitin-based adsorbents.