Effect of agitation mode (mechanical, ultrasound and microwave) on uranium sorption using amine- and dithizone-functionalized magnetic chitosan hybrid materials

Abstract

Magnetic chitosan nanoparticles, activated by glycidyl methacrylate, can be functionalized by grafting dieth-ylenetriamine (DETA) and dithizone for improving U(VI) sorption at pH around 5. The physicochemical prop-erties of the materials have been characterized by a wide variety of analytical techniques. Uranyl sorption increases with the pH (progressive deprotonation of amine and sulfur groups). Uptake kinetics are controlled by the agitation mode: the equilibrium time is reduced while using ultrasonic treatment (especially at highest frequency: 80 kHz): the cavitation effect improves the accessibility to internal reactive groups (sorption capacity is increased). The diffusivity coefficient is increased by 4-5 times. In the case of microwave, the sorption capacity is significantly reduced (especially for R-Dithizone, down to 0.8 mmol U g − 1 ) because of temperature increase, which limits the sorption (exothermic mechanism). Mass transfer is tremendously enhanced: equilibrium time is less than 60 s (30 min for ultrasonic treatment and 120 min with mechanical agitation). Sorption capacity at monolayer saturation (Langmuir) decreases with increasing the temperature from 2.20 to 1.74 mmol U g − 1 for R-Amine (from 1.77 to 1.22 mmol U g − 1 for R-Dithizone). The sorption enthalpy is close to − 19.7 kJ mol − 1 for R-Amine (with positive entropy change, ΔS • ) and − 34.2 kJ mol − 1 for R-Dithizone (negative ΔS • ). Metal desorption is highly efficient using 0.3 M Na 2 CO 3 /0.1 M H 2 O 2 solution. Metal desorption is instantaneous (less than 1 min) and complete when using microwave treatment. The ultrasonic treatment allows improving desorption efficiency and decreasing the concentration of the eluent compared with mechanical agitation. The process is successfully applied for uranyl separation from the leachates of marine sediments, especially in the presence of Complexon III (masking agent).

Phosphorylation of Guar Gum/Magnetite/Chitosan Nanocomposites for Uranium (VI) Sorption and Antibacterial Applications

“…However, recent studies have clearly showed the beneficial effect using alternative modes of agitation. The sorption performance can be strongly improved by application of ultrasonic treatment (UT) [92] or microwave activation [93]); in the latter case the kinetic rate is drastically accelerated while the equilibrium sorption is dramatically decreased.…”

Adsorption of Uranium, Mercury, and Rare Earth Elements from Aqueous Solutions onto Magnetic Chitosan Adsorbents: A Review

“…The thermal degradation of R-Amine and R-Dithizone are relatively close, exhibiting that the residual weights after complete degradation are close to 15 and 11%, respectively. However, DTG curves showed substantial differences between the two sorbents, proving that the water uptake of R-Dithizone was higher in comparison to R-Amine (diphenylthiocarbazone for producing GMA-magnetic/CS-dithizone NPs, R-Dithizone, for comparison with R-Amine sorbent) [ 13 ].…”

“…Here, this band is “hidden” in the range of 970–900 cm −1 (poorly resolved region). A series of smalls bands at 1343 cm −1 , 826 cm −1 , and 745 cm −1 could be attributed to the ligand of nitrate attached to bound uranyl (−N=O symmetric bending, −N−O out of plane rocking, −N−O symmetric bending, respectively) [ 13 ].…”

“…In the case of R-Dithizone, in addition to the aforementioned functional groups, the change in the S=C-N chemical environment confirms that these groups (reactive) may also take part in the binding of uranyl (possibly bound as a form of nitrate). Figure 23 summarizes and depicts the tentative mechanisms for the bending of uranium onto R-Amine and R-Dithizone composite nanoadsorbents, respectively [ 13 ].…”

“… Synthesis routes for the preparation of R-Amine and R-Dithizone sorbents. Reprinted from Ref [ 13 ]. Copyright 2021 with permission from Elsevier B.V. …”