1. Technetium-99 decontamination from radioactive wastewater by modified bentonite: batch, column experiment and mechanism investigation.
- Author
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Yang, Junqiang, Shi, Keliang, Wu, Fei, Tong, Juan, Su, Yin, Liu, Tonghuan, He, Jiangang, Mocilac, Pavle, Hou, Xiaolin, Wu, Wangsuo, and Shi, Weiqun
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BENTONITE , *SEWAGE , *ADSORPTION capacity , *CETYLPYRIDINIUM chloride , *DENSITY functional theory - Abstract
[Display omitted] • HDPy-bent with high adsorption capacity and fast kinetic for 99TcO 4 − was synthesized. • HDPy-bent displayed superior selectivity towards 99TcO 4 −. • Adsorption mechanism of anion exchange and surface precipitation was confirmed by experiments and DFT simulations. • HDPy-bent was proved to be an excellent material for 99Tc decontamination from wastewater by successful column experiments. Technetium-99 (99Tc), as one of the important high-yield fission products, poses a significant threat to the environment and human health due to its radiotoxicity, long half-life, high solubility and mobility in the environment. Thus, removal of 99TcO 4 − from radioactive wastewater is considerably imminent for waste disposal and environment conservation. In this work, Hexadecylpyridinium Chloride Monohydrate modified bentonite (HDPy-bent) was synthesised and used as an adsorbent to remove 99TcO 4 −. The adsorption behaviours of ReO 4 − as an analogue for TcO 4 − were investigated as functions of contact time, solution pH, initial concentration, and competing anions using batch techniques. It is demonstrated that the HDPy-bent showed an excellent adsorption ability for ReO 4 − at the pH range of 2–11, fast adsorption kinetic (reaching equilibrium within 3 min at room temperature), and maintains desirable ReO 4 − adsorption in the presence of concomitant anions at an excessive concentration of 500 times (Cl−, HCO 3 −, NO 3 −, CO 3 2−, SO 4 2− and PO 4 3−). As for adsorption mechanism, we propose the anion exchange process at low concentration of Re(VII) and precipitation reaction at high concentration, while the driving force of the high ReO 4 − adsorption ability is the interaction between ReO 4 − anion and pyridinium ring of HDPy+, which is confirmed by density functional theory (DFT) simulations. Additionally, DFT studies also shed light on the adsorption structure of HDPy+/ReO 4 − and the origin of adsorption selectivity. Moreover, four adsorption-desorption cycles suggest that the HDPy-bent has good durability and reusability. Furthermore, ReO 4 − can be removed completely and recovered fractionally by using the chromatography column packed with HDPy-bent from simulated groundwater samples. The work presented herein demonstrates a low-cost adsorbent which can efficiently remove 99Tc from contaminated water. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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