Phenolic Based Porous Carbon Fibers with Superior Surface Area and Adsorption Efficiency for Radioactive Protection

Abstract

Radioactive iodine element mainly in CH₃I is a key fission product of concern in the nuclear fuel cycle, which directly threatens human health if released into the environment. Effective capture of the I element is essential for human health protection. The iodine filter, consisting of an activated carbon inner core and cotton filter, is the most common radioactive iodine protection product. Currently, the activated carbon inside the iodine filter suffers from the weak adsorption efficiency and high cost. Herein, a process based on a strong alkali activation method was developed to significantly improve iodine absorption and reduce the cost. A series of flexible porous carbon fibers with a high specific surface area (up to about 1,500 ~ 2,200 m²/g) were prepared by carbonation of the phenolic resin fibers (PF, prepared through melt spinning and crosslink) followed by activation via KOH treatment. Meanwhile, the nitrogen-doped sp²-heterogeneous carbon atoms were prepared by adding nitrogen sources such as urea which led to a high surface area nano-porous fibers with an average pore size of ~ 2.4 nm. The nitrogen-doped porous carbon fibers exhibit very high adsorption for liquid iodine and iodine vapor. The liquid iodine adsorption capacity of nitrogen-doped porous carbon NDAC-4 prepared under 800 °C reaches 2,120 mg/g, which is 2.1 times higher than that of the commercial iodine filter, and for iodine vapor the capacity can reach 5,330 mg/g. Meanwhile, the CH₃I adsorption capacity is 510 mg/g, which is 3.4 times higher than that of commercial unmodified viscose fibers and has greater stability and circularity. Importantly, the research has met the requirements of industrial production, and the fabrication of phenolic-fibers-based protection equipment can be widely used in the nuclear radiation industry.

Funding

Science and Technology Planning Project of Guangdong Province(2019B010941001); Science and Technology Planning Project of Shenzhen Municipality(JCYJ20200109140812302); Dongguan Science and Technology Bureau(2019707126017)