The adsorbent for efficient iodine capture based on citrazinic acid and cytosine: experimental synthesis with a simple way and property analysis with electronic structure calculations

Abstract

Radioactive iodine, one type of nuclear waste, is harmful to the environment and human health due to its long half-life and volatility. Therefore, designing and synthesizing low-cost and easily-made materials for the effective adsorption of radioiodine is widely concerned. Herein, a biscuit-shaped new material was synthesized by a grinding-mixing coupled with sonication protocol through self-assembly interactions between citrazinic acid (CA) and cytosine (CY) aiming to achieve the iodine capture from both vapor and solution. Electronic structure calculations were used to reveal the adsorption mechanism. The results showed that the high uptake of iodine by CACY originates from the charge transfer via CACY to the antibonding molecular orbital (σ∗) of I2. Meanwhile, trouble-free entry pore sizes of CACY also contribute to the physisorption of molecular iodine. Besides, the iodine molecule is preferentially perpendicularly adsorbed on the carbon atom of the CA ring. Moreover, CACY exhibits a high capture for iodine in hexane following pseudo-second-order kinetics and fitting the Langmuir isotherm model. This work presents a facile and inexpensive synthesis approach for radioiodine adsorption materials and provides new insights into the interaction mechanism between the self-assembled materials and the adsorbates.

Keywords

• Citrazinic acid
• Cytosine
• Self-assembly
• Iodine adsorption
• DFT calculations