纤维素基荧光响应型汞Hg (II)吸附剂的制备及吸附机理研究

Activated carbon based adsorbents have low adsorption capacity and poor selectivity on mercury removal from aqueous solution, and could not be monitored online. In order to optimize the grafting efficiency of heterogeneous reaction system, “pre-grafting” technique is employed to significantly increase the grafting sites in cellulose based adsorbents. Based on the mechanism of PET (photo induced electron transfer), [Receptor-Spacer-Sensor] system is established by introducing rhodamine fluorescent groups into the adsorbent structure, which could tell the immediate concentration according to the fluorescent signals when meets mercury ions in water. As a result, the correlation between fluorescence intensity and the concentration of the target metal ions in water is thus established, and the integrated preparation of fluorescent probe and adsorbent material is realized. In addition, the adsorption mechanism is investigated by comparing the DFT data and the single crystal structure of the coordination complex between Hg (II) and the sensor molecules. The research proposed in this application focuses on preparing an integrated system for Hg (II) removal with simultaneous adsorption and detection, which has high adsorption capacity and specific fluorescent response to Hg (II). Moreover, this project will be of great scientific value and practical significance to the research of multi-functional cellulose based adsorbent and supramolecular ion recognition.

针对现有活性炭基汞Hg (II)吸附剂材料对水相汞吸附容量低、选择性差、无法在线监测的问题，本项目提出采用纤维素基体材料，通过“先行共聚”的方式显著增加其接枝位点以优化该类型非均相反应体系的接枝效率；在此基础上，基于光致电子转移机理，将对汞具有特异性响应的罗丹明类荧光信号基团（受体分子）引入吸附剂分子结构中，建立[Receptor-Spacer-Sensor]荧光增强型分子体系，可实现在吸附汞的同时释放荧光信号，以此反馈溶液中金属汞的即时浓度，从而建立荧光强度与离子浓度对应关系，实现荧光探针与吸附剂材料的集成化制备，将吸附与在线检测同时进行。采用缓慢挥发法制备受体分子与Hg (II)的配合物单晶，利用单晶数据与量子化学模拟数据分析吸附机理。本项目将构建高吸附容量、对汞具有特异性荧光响应的吸附检测一体化吸附剂体系，对多功能纤维素基吸附剂和超分子化学离子识别的研究具有重要的科学价值和实际意义。

本项目围绕水中重金属Hg (II)离子的检测与脱除问题展开研究。针对纤维素基吸附剂材料改性过程中由非均相反应导致的接枝效率低且功能单一的问题，提出了预接枝的反应策略，构建侧链多反应位点方式对后续改性功能基团进行有效放大，通过细胞增殖实验证实该方法的生物相容性与环境友好性。在此基础上，建立了基于壳聚糖和纤维素多底物形式的荧光增强响应型吸附剂体系，其对水相Hg (II)高选择性的荧光发射与灵敏的比色响应实现了材料的吸附检测一体化。同时，提出了基于分子内电荷转移的荧光发射机制，并通过密度泛函理论计算探讨了吸附与检测机理。此外，根据单酰氯小分子的聚集诱导发光现象，创新地将其固定于固体纤维素基质中形成初始态发光吸附剂材料，其对水相Hg (II)具备极高的选择性，检测限低至8.33×10-9 M。在以上项目进展的基础上，进行了材料大吸附容量与灵敏高选择性的耦合，制备了双反应位点的荧光响应型纤维素基吸附剂，其对水中Hg (II)离子的吸附容量高达624.8 mg/g，检测限低至5.9×10-9 M，并可同时实现“裸眼识别”。项目执行期内研究成果发表在Chemical Engineering Journal，Reactive and Functional Polymers，Separation and Purification Technology，European Polymer Journal等高水平期刊上，并申请国家发明专利一项。本项目的实施为荧光探针的设计及应用提供了积极的借鉴及促进作用，是功能性吸附剂的开发利用的一项重要研究进展。