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

Radioactive iodine element mainly in CH3I is a key fission product of concern in the nuclear fuel cycle,which directly threat-ens 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 pro-tection 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 m^(2)/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 sp^(2)-heterogeneous carbon atoms were prepared by add-ing 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 CH_(3)I 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.