高铀/钒吸附容量比纤维吸附剂的研制及吸附机制研究

In the process of extracting uranium from seawater, fibrous adsorbents with amidoximate and carboxyl ligands possess some shortcomings, such as low adsorption capacity ratio of uranium to vanadium and vanadium ions difficult to desorb, which seriously influence its uranium adsorption performance and recycling efficiency. In this project, Ultra-high molecular weight polyethylene (UHMWPE) fiber will be selected as a substrate owing to its high tensile strength. Diaminomaleonitrile (DAMN) will be immobilized onto UHMWPE fiber through low energy electron beam irradiation induced graft polymerization technique. Subsequently, the UHMWPE-DAMO fibrous adsorbent will be fabricated by the amidoximation reaction. The adsorption capacity ratio of uranium to vanadium and uranium adsorption capacity of UHMWPE-DAMO fibrous sorbent will be evaluated via simulated seawater flowing adsorption platform and natural seawater adsorption platform. The coordination mode between UHMWPE-DAMO fibrous adsorbent and uranium/vanadium will be carefully studied based on analysis of X-ray absorption fine structure (XAFS) data, in order to illustrate its adsorption mechanism. The experimental conditions will be systematically optimized in an attempt to achieve the adsorption capacity ratio of uranium to vanadium of 5 to 1 and the uranium adsorption capacity of 3 mg-U/g-ads (30 days) in natural seawater.

含偕胺肟基和羧基的纤维吸附剂在海水提铀过程中，存在铀/钒吸附容量比低和钒洗脱条件苛刻导致纤维强度下降等不足之处，严重影响吸附剂的铀吸附性能和循环利用效率。本项目拟选用高强度的超高分子量聚乙烯(UHMWPE)纤维作为基材，利用低能电子束辐射接枝改性的方法，将二氨基马来腈(DAMN)嫁接于UHMWPE纤维上，结合偕胺肟化反应，制备出含DAMO功能分子的UHMWPE纤维吸附剂(UHMWPE-DAMO)。依托模拟海水流动吸附平台和天然海水吸附平台，评估UHMWPE-DAMO纤维吸附剂的铀/钒吸附容量比和铀吸附容量。基于X射线吸收精细结构(XAFS)分析测试手段，研究UHMWPE-DAMO纤维吸附剂与铀、钒的配位方式，阐明其吸附机制。通过优化实验条件，筛选出在天然海水中铀/钒吸附容量比大于5:1和铀吸附容量大于3 mg-U/g-ads(30天)的UHMWPE-DAMO纤维吸附剂。

本项目在执行期间，利用辐射接枝技术并结合化学改性制备了UHMWPE-DAMO纤维，研究了接枝反应参数对GMA接枝率的影响和EDA开环反应条件对开环率的影响，优化了UHMWPE-DAMO纤维制备工艺；基于辐射接枝法制备了含不同AO基和AA摩尔量的UHMWPE-g-P(AO-co-AA)纤维；采用辐射接枝法制备了含不同共聚单体（MAA、ITA、AA和AAm）的AO基PE无纺布；通过辐射接枝法制备了含不同AO基和MAA摩尔量的UHMWPE-g-P(AO-co-MAA)纤维。采用SEM、ATR-FTIR、13C-NMR、XPS、DSC、TGA、单丝拉力仪等对吸附材料进行表征测试，掌握吸附材料的理化性能与结构信息。开展了实验室模拟海水和真实海水吸附实验，利用ICP-AES测试手段评估材料的铀吸附性能。基于XPS和EXAFS表征手段对活性官能团与铀酰离子的配位结构进行表征，阐明材料吸附铀的机理机制。UHMWPE-DAMO纤维接枝GMA优选条件为：吸收剂量为150 kGy，反应温度为65℃和反应时间为2h；EDA开环优选条件为：EDA浓度为30vol%，反应温度为70℃和反应时间为0.5h。UHMWPE-DAMO纤维表现出优异的铀/钒吸附选择性。共聚单体协同吸附铀性能依次为MAA、ITA、AA和AAm。XPS表征结果证实UHMWPE-DAMO纤维通过偕胺肟基中“NH2”与“OH”与铀酰离子进行配位从而实现对铀酰离子的富集。EXAFS表征结果表明UHMWPE-g-P(AO-co-AA)纤维通过偕胺肟基取代碳酸铀酰中的碳酸根实现对铀酰离子的富集，U-O(AO)和U-N(AO)配位键主要是铀5f/6d轨道与N(AO)或O(AO)的2p轨道相互作用的结果。本项目研制了一系列海水提铀用AO基聚合物吸附材料，并系统研究了材料的制备工艺、表征测试了材料的理化性能、评估了材料在不同海域的吸附性能和探讨了材料的铀吸附机理机制，为制备高铀/钒吸附选择性的海水提铀材料提供了理论依据和技术参考。