Preparation of carbon based porous adsorbent with ultra high specific surface area and its Kr gas storage performance

doi:10.11949/0438-1157.20241533

Abstract

Abstract:

The effective recovery and safe storage of Kr-85 can reduce the emission dose of radioactive gaseous effluents from nuclear facilities and reprocessing plants, which is of great significance to the safety of nuclear fuel cycle. Compared with the current stainless steel vessel storage technology, the solid porous adsorbent-based adsorption storage technology has the advantages of lower storage pressure and smaller storage volume. Developing large Kr gas adsorption capacity porous adsorbents is important for reducing Kr-85 pressure in storage vessels. Since high-energy electrons that released from Kr-85 can interact with metal elements, metal-organic framework adsorbents are not suitable for long-term Kr-85 storage. In this study, three carbon-based porous adsorbents (PAF-1, with a specific surface area of 5310 m²/g; HCP-2, with a specific surface area of 2887 m²/g; and XJTU-C, with a specific surface area of 2505 m²/g) were synthesized for Kr gas storage, and their Kr gas storage performance was studied in detail under different temperatures and pressures. The relationship between pore properties (such as specific surface area, pore size, and micropore proportion) and Kr gas storage capacity was analyzed using a high-pressure adsorption apparatus. PAF-1 with the highest specific surface area has a maximum absolute Kr adsorption capacity of 1270 mg/g at 2 MPa and 0℃. XJTU-C adsorbent has the highest Kr adsorption enthalpy and adsorption rate at 2 MPa and 0℃, with a Kr adsorption capacity of 1179 mg/g. HCP-2 has lower affinity for Kr molecules than XJTU-C, resulting in low high-pressure Kr adsorption capacity. This research analyzed the key factors affecting the storage performance of Kr gas and provided experimental support for the design of adsorbents with excellent Kr storage performance.

Key words: krypton gas storage, spent fuel reprocessing, adsorption, porous media, activated carbon

摘要：

熔盐堆核燃料燃烧和乏燃料后处理过程会释放大量Kr-85放射性气体。Kr-85的有效回收和安全存储可降低核设施和后处理厂放射性气态流出物的排放剂量，对核燃料循环的安全保障具有重要意义。基于固体多孔吸附剂的吸附存储技术相较于当前采用的不锈钢压力罐储存技术具有存储压力低和存放体积小等优势。开发具有高Kr气吸附容量的多孔吸附剂对降低Kr-85储罐压力、缩小放射性储罐体积十分重要。由于Kr-85的β衰变会释放高能量电子，能与金属元素作用发生轫致辐射产生二次射线，因此金属有机框架吸附剂不适合Kr-85的长期存储。本文合成了三种不含金属元素且具有超高比表面积的碳基多孔吸附剂（多孔芳香框架PAF-1，比表面积为5310 m²/g；超交联聚合物HCP-2，比表面积为2887 m²/g；超级活性炭XJTU-C，比表面积为2505 m²/g）作为Kr气存储材料，并对其不同温度和压力下的Kr气储存性能进行了详细研究。采用高压吸附仪分析了三种吸附剂孔性质（如比表面积、孔径大小、微孔比例）与Kr气存储容量和吸附速度的关系。在2 MPa和0℃条件下，PAF-1具有最高的比表面积和集中于1.4 nm的微孔，对Kr气的最大绝对吸附量达到1270 mg/g；XJTU-C吸附剂对Kr气的最大绝对吸附量为1179 mg/g，且具有最高的氪气吸附焓及吸附速度，但其吸附量对温度变化较为敏感；HCP-2材料对Kr气的绝对吸附量为733 mg/g，但是其微孔占比较小的孔结构对Kr分子的亲和力比XJTU-C低，导致高压Kr吸附容量不高。本研究分析了影响Kr气存储性能的关键因素，为后续设计、合成具有良好Kr气存储性能的吸附剂提供了实验依据。

关键词: 氪气存储, 乏燃料后处理, 吸附, 多孔介质, 活性炭

CLC Number:

TQ 424

Yufeng TANG, Chunhui TAO, Yongzheng WANG, Yinhui LI, Ran DUAN, Zeyi ZHAO, Heping MA. Preparation of carbon based porous adsorbent with ultra high specific surface area and its Kr gas storage performance[J]. CIESC Journal, 2025, 76(7): 3339-3349.

唐羽丰, 陶春珲, 王永正, 李印辉, 段然, 赵泽一, 马和平. 超高比表面积碳基多孔吸附剂制备及其Kr气存储性能研究[J]. 化工学报, 2025, 76(7): 3339-3349.

Figures/Tables 16

Fig.1 Infrared spectroscopy

Fig.2 SEM images of PAF-1，HCP-2 and XJTU-C

Table 1 Elemental analysis data of sample

样品	元素含量/%
样品	N	C	H	O
PAF-1	0.39	92.01	5.54	2.284
HCP-2	0.17	87.04	6.55	2.860
XJTU-C	0.43	97.21	0.66	1.050

Fig.3 The 77 K nitrogen adsorption-desorption isotherm and pore size distribution of PAF-1

Fig.4 The 77 K nitrogen adsorption-desorption isotherm and pore size distribution of HCP-2

Fig.5 The 77 K nitrogen adsorption-desorption isotherm and pore size distribution of XJTU-C

Fig.6 The adsorption-desorption isotherms of Kr gas on PAF-1 at high pressure

Fig.7 The adsorption-desorption isotherms of Kr gas on HCP-2 at high pressure

Fig.8 The adsorption-desorption isotherms of Kr gas on XJJTU-C at high pressure

Fig.9 Absolute volume adsorption curves of PAF-1, HCP-2 and XJTU-C for Kr gas

Table 2 Mass adsorption capacity of PAF-1， HCP-2 and XJTU-C

材料	吸附类型	0℃吸附量/ (mg/g)	25℃吸附量/(mg/g)	40℃吸附量/(mg/g)
PAF-1	过剩吸附	970	914	857
PAF-1	绝对吸附	1270	1140	1056
HCP-2	过剩吸附	550	477	380
HCP-2	绝对吸附	733	621	483
XJTU-C	过剩吸附	885	738	634
XJTU-C	绝对吸附	1179	1032	805

Table 3 Volumetric adsorption capacity of PAF-1， HCP-2 and XJTU-C

材料	密度/ (g/cm³)	吸附类型	0℃吸附量/(mg/cm³)	25℃吸附量/ (mg/cm³)	40℃吸附量/ (mg/cm³)
PAF-1	0.10	过剩吸附	97	91	85
PAF-1	0.10	绝对吸附	127	114	105
HCP-2	0.38	过剩吸附	209	181	144
HCP-2	0.38	绝对吸附	278	236	183
XJTU-C	0.32	过剩吸附	283	236	202
XJTU-C	0.32	绝对吸附	377	330	257

Fig.10 Virial equation fitting of Kr adsorption isotherms of PAF-1, HCP-2 and XJTU-C

Table 4 Fitting parameters of Virial equation for Kr adsorption isotherms of three materials

吸附剂	a₀	a₁	a₂	a₃	a₄	a₅	b₀	b₁	b₂	R²
PAF-1	-2623.18291	530.31027	-37.83687	1.23826	-0.07942	0.00231	14.60973	-1.50085	0.09018	0.99943
HCP-2	-1812.82029	85.3354	-7.18885	2.23261	-0.32743	0.02301	12.91298	-0.05764	-0.00503	0.99998
XJTU-C	-2191.83641	193.13465	-28.26386	2.86836	-0.22259	0.0073	13.37044	-0.34249	0.03439	0.99999

Fig.11 Adsorption enthalpies of PAF-1, HCP-2 and XJTU-C for Kr

Fig.12 Instantaneous adsorption rates of Kr by PAF-1, HCP-2 and XJTU-C

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