Abstract
Poly(ethylene glycol) bis(methylimidazolium) di[bis(trifluoromethylsulfonyl)imide] was synthesized as an ionic liquid and impregnated onto chitosan. The removal of uranium(VI) ions from aqueous solution was investigated with batch sorption tests using ionic liquid impregnated chitosan. Response surface methodology based on 3 level Box–Behnken design was applied to analyze the effect of initial pH (4–6), initial concentration (20–60 mg L-1), contact time (15–105 min), and temperature (30–50 °C) on the uptake capacity of uranium(VI). Main effect of initial concentration, quadratic effect of contact time, and dual effect of initial pH and contact time were found statistically significant based on analysis of variance (ANOVA). Probability F-value (F = 1.49 ×10-6) and correlation coefficient (R2 = 0.96) point out that the proposed model is compatible with experimental data. The maximum uptake capacity of uranium(VI) was found as 28.48 mg g-1 at initial pH 4, initial concentration 60 mg L-1, contact time of 70 min, and a temperature of 50 °C. Sorption kinetics followed a pseudo-second-order model and Freundlich model was obtained to fit the sorption data. The presence of competing ions slightly reduced uranium(VI) sorption and the selectivity order can be given as UO22+>Zn2+>Ni2+.
Highlights
Uranium is a naturally occurring radioactive element and chemically toxic heavy metal
The presence of vibration bands of = C-H, C = N, C = C, C-F, C-O, S = O, and C-S groups in the Fourier transform infrared (FTIR) spectrum of ionic liquids (ILs)-based chitosan sorbent showed that the IL was impregnated onto chitosan
8, selectivity order can be given as. These results suggest that IL impregnated chitosan can be used successfully in the treatment of radioactive wastewater polluted with uranium(VI) in the presence of competing ions
Summary
Uranium is a naturally occurring radioactive element and chemically toxic heavy metal. During the stages of nuclear fuel production such as mining, purification, and enrichment, large amount of uranium polluted wastewater is produced. Uranium exists mostly in the valence states of uranium(IV) and uranium(VI) depending on the environment. The oxidized state uranium(VI) can highly migrate and it is more soluble. The direct discharge of uranium polluted waste streams is hazardous for environment and human health. Uranium can enter the human body via food chain. It can cause harmful effects on skin, kidneys, liver, and may even lead to death [2]. It is highly important to remove uranium from wastewater prior to discharge and to prevent its mobilization into the environment
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