重金属离子在胶州湾入海河流中的运移行为及其催化/吸附耦合去除机制研究-以大沽河为例

Due to high chemical toxicity, bio-cumulative effect, without self-purificaiton ability, easy migration and transformation, the heavy metal pollution has become a major environmental and geochemical concerned issue. The heavy metal ions contamination of Jiaozhou Bay, which is a semi-closed bay, has bring serious threats to the human health and marine life. The heavy metal in the streams flowing into the Jiaozhou Bay is the most important contamination source. Dagu river, the largest river flowing into Jiaozhou Bay, is taken as an example in this study. The vertical distributions of heavy metal in Dagu river will be measured. The secondary pollution of heavy metal ions, which released from the surface sediments in the river, and its impact on the migration behavior will be investigated under dynamic conditions of natural water. The experiments will be carried out to understand the transport law of heavy metal in the river..The heterostructure composite materials based on ferromagnetic graphene will be designed and synthesized, which are used for the removal of heavy metal ions in wastewater. The first-principle theoretical calculations based on density functional theory (DFT) will be used to explore the structure and properties of the composite and its mechanism of heavy metal ions removal. The theoretical heterostructure model will be constructed, tested and verified in our study. The electronic and interface structure, charge distribution, surface and interface properties, electronic migration path, oxidation and reduction potential, surface defects are all involved to explore properties of the composite materials in our work. The metal ions containing wastewater will be treated by the products as absorbent/photocatalyst. The effects of affecting parameters such as metal ion concentration, background electrolytes, contact time on the heavy metal ion uptake capacity of the prepared nanoparticles are explored in the experimental process. The reaction model of metal ion on the surface of adsorbent composite will be induced from the experimental observation of adsorption kinetics, thermodynamics and isotherm. The constant capacitance model and surface complex model are involved to explore its reaction mechanism. The mechanism of “physi-chemcial adsorption and oxidation-reduction reaction” is proposed in this work to illustrate the reaction of metal ions on the surface of absorbent/photocatalyst nanocomposites. The annular photocatalytic reactor filled with adsorbent composite will be used to removal the heavy metal ions in wastewater, which resolved the problems such as the separation and reusability of adsorbents, the secondary pollution caused by the release of heavy metal ions. The investigation will provide the scientific basis for the heavy metal pollution treatment and bring suitable adsorbents for removal of heavy metal ions from environmental and industrial wastewater.

因其毒性强、有生物累积性，易迁移转化，无环境自净能力，重金属污染成为备受关注的环境和地球化学问题。入湾河流携带是胶州湾重金属的重要污染源。以大沽河为例，探讨金属离子在河流中的垂向分布，讨论自然水动力条件下表层沉积物中重金属污染物的二次释放及其对离子运移行为的影响，研究其迁移规律。设计合成铁磁石墨烯基异质结构复合材料，将其用于水体中重金属离子的去除。构建异质结构理论模型，探讨其结构、电荷分布、氧化还原电位、界面电荷迁移以及表面缺陷等对材料性能的影响。理论与实验相结合，由金属离子的吸附反应动力学、热力学及等温线推测其在材料表面的作用方式，采用表面络合模型和恒容定量模式探讨金属离子的表面吸附反应，揭示其在材料表面的“物理化学双吸附+氧化还原”的反应机理。采用填料塔式环隙型光催化反应器处理废水，解决吸附剂与水体分离、循环使用，以及重金属离子的释放带来的二次污染问题，可用于重金属离子的水体净化。

重金属污染对人类生存和环境安全带来了严重威胁，已成为全球迫切需要解决的问题。课题组设计合成了铁磁性金属氧化物、石墨烯层状结构、生物炭复合吸附剂，并将其用于去除环境水中重金属离子，研究其去除性能和机理。铁磁性金属氧化物吸附剂包括Fe3O4、Fe3O4/Pinecone， Fe3O4/Graphene、Fe3O4/TiO2、Fe3O4/TiO2/Graphene三相复合物、α-Fe2O3/碳球、MoS2/GO、Fe3O4/MoS2、TiO2/Fe3O4/MoS2、MnO2/TA等吸附剂，金属离子在复合吸附剂表面的吸附过程包括表面扩散、颗粒内部扩散和吸附平衡扩散三个阶段，可以通过调控吸附剂的机构改变其表面物理化学性能提高其对重金属的去除效率。生物炭基吸附剂包括生物炭/ZnO、生物炭/MnO2、生物炭/Fe3O4/壳聚糖、生物炭/MnFe2O4等系列重金属污染修复剂，分别用于去除Cu(II)和Cr(VI)。其吸附反应动力学可采用准二级反应动力学方程拟合，吸附等温线符合Langmuir模型。对其反应热力学研究表明Cu(II)在复合生物炭表面的吸附主要为物理吸附。运用表面络合模型（SCFM）结合吸附热力学、吸附动力学以及吸附热力学模型来探究了MoS2/MnO2/TA复合材料、MnO2/PEI/TA双功能复合材料等吸附剂去除Cu(Ⅱ)和Cr(Ⅵ)的性能和机制。研究发现金属离子的吸附过程中存在静电作用、溶剂化作用、吸附质之间的相互作用以及络合作用，其中静电作用和络合作用均有利于Cu(II)的吸附，而溶剂化和吸附质间相互作用均不利于Cu(II)的吸附。物理静电相互作用主要在吸附反应的初始阶段起作用，化学相互作用是推动吸附进行，达到平衡的重要动力。将RGO/TiO2用于光催化还原Cr(VI),吸附和光催化对Cr(VI)的污染去除具有协同作用，可将Cr(VI)进行完全无害化。. 采用基于密度泛函理论的第一性原理计算方法，探究了TiO2/GO、TiO2/g-C3N4、h-BN / RGO(F)等材料的电子结构，研究了异质结的态密度、电荷密度差、电子迁移方向以及电子与空穴的分离情况，阐释了复合材料的光催化机制。此外，还研究了过渡金属硼化物MBenes等部分材料的电池性能及析氢性能。