Abstract:

The development of radioactive iodine capture materials with high efficiency and low cost is of great significance for the safe utilization of nuclear energy and the disposal of nuclear waste. In view of the application status which the radioactive iodine capture materials have low adsorption capacity and adsorption rate, and high cost. Green and low-cost lignin has rich active sites such as hydroxyl group and carboxyl group, etc., which will have potential application prospects in iodine capture. Here, the lignin with rich active sites such as hydroxyl group and carboxyl group, etc. was selected as the basic raw materials, N,N-methylene bisacrylamide (MBA) as nitrogen source and crosslinking agent, and 4-vinylbenzyl chloride (VBC) as functional monomer, a series of nitrogen modified lignin based hyper-cross-linked polymers (NLHCPs) were synthesized insitu by the two-step reaction including free radical grafting copolymerization and Friedel-Crafts alkylation, the specific surface areas of these materials was up to 715.8m²/g, and had high nitrogen content (3.95%—4.48%). The adsorption performance of iodine vapor and iodine/n-hexane solution on these NLHCPs were studied, respectively. The results showed that NLHCP-2 had the largest adsorption capacity of iodine vapor (2.5g/g), and the adsorption was mainly chemical adsorption, and the iodine molecule was converted to the polyiodide anion form at the polymer surface. At the same time, the adsorption isotherms of iodine in n-hexane solution on NLHCP-2 was more consistent with Freundlich model, and the maximum equilibrium capacity reached 230.8mg/g. The kinetic curves fitting showed that the adsorption rate was mainly controlled by the diffusion process. In addition, the iodine-loaded NLHCPs can be quickly desorbed in ethanol, and had good cycling performance. This work will provide new ideas for the development of lignin-based porous materials and offer important guidance for green and low-cost radioactive iodine capture.

Key words: lignin, polymers, adsorbents, iodine capture, desorption

摘要：

开发高效、低成本的放射性碘捕获材料对核能的安全利用和核废料处理具有重要意义。本文针对目前碘捕获材料吸附容量低、成本高等问题，以含有羟基、羧基等活性位点的木质素为基础原料，N,N-亚甲基双丙烯酰胺（MBA）为氮源，对氯甲基苯乙烯（VBC）为功能单体，通过自由基聚合接枝与Friedel-Crafts烷基化两步反应，原位构筑一系列氮修饰木质素基超交联聚合物（NLHCPs），其比表面积最高可达715.8m²/g，且有较高的氮含量（3.95%~4.48%，原子分数）。分别研究了NLHCPs对碘蒸气和碘正己烷溶液的吸附性能，结果表明NLHCP-2的碘蒸气吸附容量最高，可达2.5g/g，吸附作用主要为化学吸附，碘分子在聚合物表面转变成聚碘阴离子的形式。而其对正己烷中碘的吸附等温线更符合Freundlich模型，吸附最大平衡容量可达230.8mg/g，动力学拟合表明其吸附速率主要受扩散过程控制。吸附碘蒸气后的材料，在乙醇中可快速脱附，具有良好循环使用性能。

关键词: 木质素, 聚合物, 吸附剂, 碘捕获, 脱附