Efficiency and mechanism of adsorption of low-concentration uranium in water by a new chitosan/aluminum sludge composite aerogel
A new chitosan/aluminum sludge composite aerogel (CS/ASca) exhibiting good selectivity, easy separation potential, and high adsorption capacity was synthesized by combining chitosan (CS) and aluminum mud from waterworks (AS). The adsorption of U(VI) by the CS/ASca was assessed as a function of solution pH, adsorption time, temperature, initial concentrations of uranium, and coexisting ions. The systematic batch experiments reveal that the adsorption kinetics is described by a pseudo-second-order model, and the sorption thermodynamics involves spontaneous endothermic processes. At pH of 4, 308 K, and initial concentrations of 10–700 mg·L-1, the maximum adsorption capacity of the CS/ASca for U(VI) (simulated by Langmuir model) was 434.64 mg·g−1. Data from scanning electron microscopy/energy dispersive spectrometry, Fourier-transformed infrared, and X-ray photoelectron spectra spectroscopy indicate that uranyl ions adsorption was predominantly associated with the complexation of amino and hydroxyl groups on the surface of the CS/ASca. In addition, our results demonstrated that the Mg (Ⅱ), Pb (Ⅱ), Na (I), and K (I) ions had little or no effect on the sorption of U(VI) on the CS/ASca. This study provides new clues for the treatment of radioactive wastewater.