含氟水协同制备高结晶度三维异质结构铁基类水滑石材料及其多级循环利用研究

Fluoride and Nitrophenol compounds are important water pollutants that are generally present in Northern Shaanxi, and have led to exasperate ecological environment. Fe3+-based Layered Doubled Hydroxide Materials(LDHs) with Three-Dimensional Heterogeneous structure consisted of transition metals have been widely studied in recent years because of their potential applications in adsorbents, anion exchangers, the visible light photocatalytic, electro- and magnetic materials, and so on, which have important complementary multipole value in using of treatment Flouride-containing wastewater and Nitrophenol-containing wastewate. However, it is difficult for the transition metals such as Fe3+-based LDHs materials with high crystallinity and high performance have been obtained through the conventional precipitation method, which is prevented in application development and function expansion.. In view of the fact that fluorine ions complex with Fe3+ ions in the solution and could control Fe3+ ion slow-release, causing pH deposition range of Fe3+ raise, so the transition metals such as Fe3+-based LDHs materials with Three-Dimensional Heterogeneous structure and high performance have been obtained in a favorable condition by a fluorine ions assisted homogeneous precipitation method. On this basis, photocatalytic pegradation of nitrophenol-containing wastewate and adsorbent fluorine ion with Fe3+-based LDHs are designed respectively for achieving multistage utilization. Fluorine ion is recycled through adsorption of regeneration process of Fe3+-based LDHs, and is used for preparation of new Fe3+-based LDHs again. Then the matching and selectivity of fluoride complexing agent and different Fe3+-based LDHs materials will be systematically investigated by controlling the amount of fluorine ions and type of divalent metal ion. By adjusting the microstructure to enhance the function of Fe3+-based LDHs, and the inherent relationship between microstructure and fluorine ions was revealed. The process of topological transformation is controlled to enhance the adsorption and photocatalytic properties of Fe3+-based LDHs, providing new ideas for the development, design and application of Fe3+-based LDHs materials. At the same time it is provided a theoretical basis for the wastewater treatment in Northern Shaanxiin in the future.

陕北地区排放大量的含氟废水和含酚废水导致了生态环境日趋恶化。三维异质结构铁基类水滑石独特的结构使其具有吸附、离子交换、可见光催化、电、磁等特性，在废水处理中具有重要的多级互补利用价值。制备高结晶度三维异质结构铁基类水滑石极其困难，限制了其开发应用。本项目以含氟水为反应体系，借助氟与Fe3+的络合能力，控制Fe3+缓释并协助Fe3+与二价金属离子原位生长构建高结晶度三维异质结构的系列铁基类水滑石。在此基础上，分别处理含酚及含氟废水，实现材料的多级利用；铁基类水滑石再生过程中吸附回收废水中的氟离子使其循环使用；通过控制氟离子以及金属离子的种类和用量，研究氟对构建不同系列异质结构的匹配性和选择性；调控材料的微观结构，增强材料的功能控制，建立氟与材料微观结构的内在联系；通过控制材料的拓扑转变过程，强化其吸附和光催化性能，为铁基类水滑石的开发、设计及应用提供新思路，为陕北地区废水治理提供理论依据。

本项目采用含氟水中的氟离子作为络合剂成功制备了三维异构铁基类水滑石材料（重点研究了g-Fe2O3-Cd2+-Ni2+-Fe3+-LDHs、Ni2+-Al3+-LDHs/γ-Fe2O3-Cd-Ni-Fe-LDHs、 LaCO3OH /Ni2+-Fe3+-LDHs等），开辟了制备铁基类水滑石的新方法。对铁基类水滑石材料的形成过程进行了系统研究，充分证明了氟离子作为络合剂，能有效控制Fe3+的缓释速度，提高Fe3+的沉淀pH值，能与二价金属离子在较高pH条件下共沉淀，从而形成铁基类水滑石材料。通过调节氟离子、总金属盐的浓度和比例实现了类水滑石材料的功能化（磁性）和异构化，同时也实现了不同形貌铁基类水滑石材料的可控制备，拓展了类水滑石的种类和范围。本项目筛选了合适的类水滑石材料（Ni2+-Al3+-LDHs/γ-Fe2O3-Cd-Ni-Fe-LDHs）进行了多级循环利用研究。研究表明铁基类水滑石材料能有效降解含酚废水和有机染料废水。煅烧拓扑转化后的铁基类水滑石材料能有效吸附氟离子，并能进行再生，实现了材料的循环利用，达到了材料多级利用的目标。多次循环后铁基类水滑石材料对苯酚的降解率为98.9%，对有机染料废水（甲基橙）降解率为99%。经多次循环后对氟的吸附量可达为21.7 mg/g。这些研究成果发展了铁基类水滑石的制备方法，同时也为类水滑石的功能拓展、废水处理奠定了重要基础。项目执行期间，项目组成员的研究成果先后在Applied Clay Science, Science of Advanced Materials, Journal of Magnetism and Magnetic Materials, Nano等期刊发表学术论文12篇，申请发明专利3件，授权实用新型专利3件，参加学术会议3次，培养和指导学生12人。