Effects of activation parameters on Zeolitic imidazolate framework JUC-160-derived, nitrogen-doped hierarchical nanoporous carbon and its volatile iodine capture properties

Abstract

Despite its importance in the nuclear industry, the uncontrollable use and/or accidental release of iodine in the environment pose serious threats to human health and endanger wildlife. Therefore, effective removal of radioiodine from various environmental media is necessary to circumvent its adverse effect. Herein, we report on an excellent and highly efficient capture of iodine by ZIF (JUC-160)-derived ultra-porous carbon. The ultra-porous carbon, obtained through KOH activation at high temperature, displayed unprecedented iodine capture properties with uptake capacities of 1567 mg g−1 and 821 wt.% in the aqueous and vapor phases, respectively. Various conditions including activation temperature and residency time effects on material properties and uptake performances were evaluated. The results showed that iodine uptake increased with increasing activation temperature; while activation time beyond 60 min was not favorable because the carbon materials were completely gasified. Kinetics and Isotherm fitting with the experimental data was done to assess sorption behavior of the derived carbon materials and their interactions with iodine. The results showed that chemisorption was the dominant medium through which iodine was captured as confirmed by both pseudo-second order and Langmuir models. Furthermore, the main mechanism involved in the process was mainly attributed to electron donor-acceptor interactions wherein the oxygen-containing functional groups and nitrogen active sorption sites of the carbon materials acted as electron donors. This work provides insight into optimizing KOH activation temperature and residency time for best performance of iodine adsorbents.