海洋生态与环境科学重点实验室知识库

改性粘土法（Modified clay, MC）是一种科学有效防控赤潮灾害的应急处置方法，其具有成本低、除藻高效、安全环保等优势，是目前唯一能够大规模现场应用的方法。然而，随着赤潮灾害综合治理要求的提升，不仅需要进一步提升改性粘土的除藻效率，还需要对伴随出现的氮磷富营养化污染因子等予以有效消除。现有的改性粘土虽具有一定的营养盐消除能力，但在实际应用中仍面临效率偏低、用量偏高等问题。因此，亟待开发既能高效除藻，又能净化水体的功能性改性粘土新材料。尿素合铁（Ferric carbamide complex, FC）是以铁离子为中心、含氨基的尿素（CH₄N₂O）为有机配体的一种Fe-MOFs化合物，具有高效的吸附、螯合等能力，为其在除藻领域的应用奠定基础。本研究提出了一种以FC为改性剂制备改性粘土材料，综合提升其除藻、净水等能力的功能性赤潮治理材料制备方法。实验考察了影响新方法制备尿素合铁改性粘土（Ferric carbamide complex-modified clay, FCK）的因素，分析了不同因素影响FCK除藻性能的作用途径，通过对比实验筛选了最佳制备方法，并基于单因素分析法和正交试验法确定了方法中不同影响因素间的最佳组合条件，对新方法制备改性粘土的除藻净水性能进行了实验评估，发现尿素合铁改性粘土在高效除藻的同时对水体中活性磷酸盐有良好消除效果，并降低水体浊度。主要研究结果如下：

（1）尿素合铁改性是一种有效提升粘土除藻效率的制备方法。实验对比了原位表面合成法与预制掺混合成法获得FCK的除藻率，发现原位表面合成法为优选方案。综合利用单因素分析法和正交试验法分析了制备过程中的材料配比、反应条件对获得FCK除藻效率的影响，发现多因素均会影响获得改性粘土的除藻效率。基于赤潮治理材料最少用量、最大除藻效率、最小环境影响的筛选原则，获得最佳材料配比为尿素与铁离子比例R_U-Fe=1:1.1、尿素合铁与粘土比例R_F-K=1:1，最佳反应条件为反应温度30℃、硝酸铁溶液滴加速度1mL/min、熟化时间1h。最佳方案合成FCK在用量为0.2g/L时，对赤潮异弯藻的去除效率超过90%。进而实验考察了改性粘土的投加量和处理时间、赤潮生物的种类以及赤潮生物密度等对FCK除藻效率的影响，发现在投加量为0.2g/L处理时间≥3h时，对不同赤潮密度的赤潮异弯藻均有90%以上的去除率。且对赤潮异弯藻、东海原甲藻、微绿球藻均具有良好的应用效果。

（2）FCK通过多种机制复合实现增效除藻效果。借助扫描电镜、Zeta电位仪以及激光粒度仪观察了改性粘土的表面特征，利用XRD、XRF、FT-IR和TG-DSC分析了FCK的材料组成，利用Zeta电位仪、FT-IR及PIV分析了FCK的絮凝行为，综合材料的化学基础和絮凝行为，探究了FCK增效除藻的作用机制。第一，从材料形态与组成上可以证实FC对粘土有效改性：尿素通过羰基氧与Fe³⁺结合形成FC后，通过C-N和N-H键与高岭土结合，形成FCK复合物；电镜显微下FCK的表面形貌明显变得粗糙且有颗粒物附着；Zeta电位数据显示与高岭土相比FCK表面电位明显提升，XRD、XRF表明FCK层间距增大、表面官能团改变。基于改性粘土理论可以推断， FC改性会增强粘土与藻细胞之间的絮凝结合能力。第二，FCK的絮凝行为有明显改善：FCK除藻过程的Zeta电位随投加量和时间的增加而增加； FCK除藻过程中产生C-O或C-N新峰，为增效除藻提供化学基础；FCK除藻时会迅速形成大粒径絮体，因此，FCK表现出增效除藻能力。第三，综合材料化学基础与絮凝行为，分析FCK除藻增效的机制为：1）提升电中和作用能力增效除藻，这主要归功于FC和FCK外部结构的大量活性氨基赋予的明显电中和能力，可在短时间内絮凝藻细胞提升除藻效率；2）提升化学作用能力增效除藻，由于粘土颗粒表面的官能团发生变化，使得FCK可通过产生化学键提升絮凝除藻能力；3）提升卷扫网捕作用能力增效除藻，这主要得益于颗粒粒度的改变和表面粗糙程度的增加，使得除藻絮体粒径增大，能包裹并沉降更多藻细胞，从而提升除藻效果。

（3）尿素合铁改性粘土具有较好的活性磷酸盐去除性能，且对水质影响较小。首先借助紫外分光光度计测定了改性粘土的活性磷酸盐去除性能；然后利用浊度仪、pH计和ICP-MS表征了FCK 对水质的影响。第一，基于类同除藻材料制备方法的筛选原则，对服务于最佳活性磷酸盐去除能力的合成方案进行了实验筛选，发现服务于除藻和磷消除的FCK最佳制备方法和材料配比相同，但二者在最佳反应条件上有一定差异。服务于溶解态活性磷酸盐去除目标FCK的最佳反应条件为反应温度50℃、硝酸铁滴加速度1mL/min、熟化时间2h。此条件下FCK在用量≥0.2g/L时，水体中的磷浓度可以降至0.01 mg/L以下。第二，实验考察了最佳除藻配方下，FCK在除藻过程中对水体浊度的影响，发现在用量为0.2g/L时，其浊度约为未改性粘土的1/5；另外考察了FCK除藻过程对水体铁离子浓度和水体pH的影响，在用量0.2g/L进行除藻作用后，水体中的残余铁浓度均低于0.3mg/L；以用量0.2g/L除藻后pH变化率＜0.37%，对水环境影响较小。

The Modified Clay (MC) Method is a scientific and effective emergency response method for the prevention and control of red tide blooms. It has advantages such as low cost, efficient algae removal, safety and environmental protection, and is currently the only method that can be applied on a large scale in the field. However, with the increasing requirements for comprehensive management of red tide disasters, it is necessary not only to further improve the algae removal efficiency of modified clay, but also to effectively eliminate the accompanying nitrogen and phosphorus eutrophication pollutants. Although the existing modified clay has a certain ability to remove nutrients, it still faces problems such as low efficiency and high dosage in practical applications. Therefore, it is urgent to develop new functional modified clay materials that can efficiently remove algae and purify water bodies. Ferric carbamide complex (FC) is an Fe based Metal-organic frameworks (Fe-MOFs) compound with iron ions as the centre and amino-containing urea (CH₄N₂O) as the organic ligand. It has efficient adsorption and chelation abilities, which is the basis for its application in the field of algae removal. This study proposes a functional red tide control material preparation scheme that uses FC as a modifier to prepare modified clay materials and comprehensively enhance their capabilities in algae removal and water purification. The factors affecting the preparation of ferric carbamide complex modified clay (FCK) using a new method were experimentally investigated, and the pathways through which different factors affect the algae removal performance of FCK were analyzed. A comparative experimental approach was employed to identify the optimal preparation plan. This was followed by a single factor analysis and orthogonal experiment to determine the optimal combination conditions among different influencing factors in the method. The efficacy of the modified clay prepared by the new method in removing algae and purifying water was experimentally evaluated. It was demonstrated that urea carbamide-modified clay has a beneficial impact on the removal of active phosphates from water, while simultaneously exhibiting effective algae removal and a reduction in water turbidity. The principal findings of the research are as follows: 
(1) Modified with FC is an efficient and effective preparation scheme for improving the efficiency of clay algae removal. The experiment compared the efficiency of algae removal of FCK obtained by the in situ surface synthesis method and Precast mixing-synthesis method. It was found that the in situ surface synthesis method was the optimal solution. A comprehensive analysis of the influence of material ratio and reaction conditions during the preparation process on the algae removal efficiency of FCK was conducted using both the single factor analysis method and the orthogonal experimental method. It was demonstrated that a multitude of factors can influence the efficiency of algae removal in modified clay. The optimal material ratio was determined based on the principles of minimum red tide control material, maximum algae removal efficiency, and minimum environmental impact. The results indicated that the optimal ratio was Ratio of urea to iron ions R_U-Fe=1:1.1 and Ratio of ferric carbamide complex to clay R_F-K=1:1. The optimal reaction conditions were identified as reaction temperature 30 ℃, droplet acceleration of iron nitrate solution 1 mL/min, and maturation time 1 h. The optimal solution for synthesising FCK at a dosage of 0.2 g/L resulted in a removal efficiency of over 90% for red tide algae. Furthermore, the effects of the dosage and treatment time of modified clay, the types of red tide organisms, and the density of red tide organisms on the efficiency of FCK algae removal were experimentally investigated. It was demonstrated that when the dosage was 0.2 g/L and the treatment time was ≥ 3 hours, the removal rate of red tide heterotrophic algae with different densities exceeded 90%. Furthermore, the product has been found to be effective in the removal of heterotrophic algae, including those found in the East China Sea, as well as those belonging to the genus Prodiginopelta and microalgae. 
(2) FCK achieves enhanced algae removal through a combination of multiple mechanisms. The surface characteristics of the modified clay were observed using scanning electron microscopy, a zeta potential analyzer, and a laser particle size analyzer. The composition of the FCK material was analysed using X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis coupled with differential scanning calorimetry (TG-DSC). The flocculation behaviour of FCK was analysed using a combination of techniques, including zeta potential analysis, Fourier transform infrared spectroscopy (FTIR), and particle image velocimetry (PIV). The chemical basis and flocculation behaviour of the materials were considered in order to explore the mechanism by which FCK enhances algae removal. Firstly, it can be confirmed from the material morphology and composition that FC is effective in modifying clay. The formation of FC is initiated by the combination of carbonyl oxygen with Fe³⁺; subsequently, the C-N and N-H bonds facilitate the combination of FC with kaolin, resulting in the formation of FCK composites. Upon examination under electron microscopy, the surface morphology of FCK becomes significantly rougher, accompanied by the presence of particles. The zeta potential data indicates a notable increase in the surface potential of FCK in comparison to kaolin, while the XRD and XRF results demonstrate an expansion in the interlayer spacing and alterations in the surface functional groups of FCK. It can be postulated that the modification of FC will enhance the flocculation and binding ability between clay and algae cells, in accordance with the theory of modified clay. Secondly, there is a significant improvement in the flocculation behaviour of FCK. The zeta potential of the FCK algae removal process increases with the increase of dosage and time. During the FCK algae removal process, new peaks of C-O or C-N are generated, providing a chemical basis for enhanced algae removal. FCK rapidly forms large particle size flocs during algae removal, therefore, FCK exhibits an enhanced ability to remove algae. Thirdly, a comprehensive analysis of material chemistry and flocculation behaviour has led to the conclusion that the mechanism of FCK algae removal efficiency enhancement is as follows: 1) The enhancement of the ability of electroneutralisation to enhance algae removal efficiency is attributed to the significant electroneutralisation ability endowed by the large number of active amino groups in the external structure of FC and FCK, which can flocculate algae cells and improve algae removal efficiency in a short period of time. 2) The enhancement of chemical reactivity and the enhancement of algal removal efficiency are also observed. The functional groups on the surface of clay particles undergo changes, which enables FCK to enhance its flocculation and algal removal ability by generating chemical bonds. 3) The ability of the sweeping net to capture and remove algae is improved by a change in particle size and an increase in surface roughness, which increases the particle size of the algal flocs and can encapsulate and settle more algal cells, thereby improving the algal removal effect.
(3) FCK exhibits excellent phosphorus removal and turbidity reduction performance, with minimal impact on water quality. Firstly, the removal of active phosphate from modified clay was measured using a UV spectrophotometer; then the influence of FCK on water quality was characterised using turbidimeters, pH meters and ICP-MS. Firstly, the preparation schemes and material ratios were subjected to experimental screening based on the principles of similar algal removal material preparation schemes. This involved the use of single factor analysis and orthogonal experimental methods to identify the schemes and ratios that exhibited the greatest active phosphate removal capacity. It was determined that the optimal preparation scheme for FCK, which serves both algal removal and phosphorus elimination, is identical. However, there are certain differences in the optimal reaction conditions between the two. The optimal reaction conditions for FCK serving the phosphorus removal target are reaction temperature 50 ℃, droplet acceleration of iron nitrate solution 1 mL/min, and maturation time 2 h. In this context, it can be observed that when the dosage of FCK is ≥ 0.2 g/L, the phosphorus concentration in the water can be reduced to below 0.01 mg/L. Secondly, the experiment investigated the effect of FCK on water turbidity during the algae removal process under the optimum algae removal formula. It was found that at a dosage of 0.2g/L, its turbidity was about 1/5 of that of unmodified clay; in addition, the effects of the FCK algae removal process on the iron ion concentration and pH of the water were investigated. Following the application of 0.2 g/L for the removal of algae, the residual iron concentration in the water was found to be below 0.3 mg/L. Furthermore, the pH change rate following the removal of algae with a dosage of 0.2 g/L was observed to be less than 0.37%, indicating a relatively minor impact on the water environment.

第1章 绪论 1

1.1 赤潮危害及防治方法 1

1.1.1 赤潮的成因 1

1.1.2 赤潮的危害 2

1.1.3 赤潮的治理方法 3

1.2 改性粘土治理赤潮方法概述 5

1.2.1 改性粘土治理赤潮理论模型的构建和演变 5

1.2.2 改性粘土研发进展 6

1.2.3 改性粘土治理赤潮的机制 8

1.3 金属有机骨架材料（metal-organic frameworks, MOFs）概述 10

1.3.1 MOFs材料简介 10

1.3.2 MOFs材料的合成方法 11

1.3.3 铁基MOFs材料的优势 12

1.4 研究目标及研究内容 12

1.4.1 研究目标 13

1.4.2 研究内容 13

1.4.3 技术路线图 14

第2章 尿素合铁改性粘土的合成方案构建 15

2.1 前言 15

2.2 实验材料和方法 16

2.2.1 实验药品与试剂 16

2.2.2 实验材料准备 16

2.2.3 实验方法 18

2.3 实验结果与分析 19

2.3.1 制备方法的确定 19

2.3.2 材料配比的确定 20

2.3.3 反应条件的确定 21

2.3.4 应用效果分析 23

2.4 小结 26

第3章 尿素合铁改性粘土的除藻作用机制分析 27

3.1 前言 27

3.2 实验材料与方法 27

3.2.1 实验药品与试剂 27

3.2.2 实验材料准备 29

3.2.1 实验方法 30

3.3 实验结果与分析 31

3.3.1 尿素合铁改性粘土的表面特征 31

3.3.2 尿素合铁改性粘土的材料组成 34

3.3.3 尿素合铁改性粘土的絮凝行为 38

3.4 小结 43

第4章 尿素合铁改性粘土的可应用性分析 45

4.1 前言 45

4.2 实验材料与方法 45

4.2.1 实验药品与试剂 45

4.2.2 实验材料准备 46

4.2.3 实验方法 47

4.3 实验结果与分析 48

4.3.1 除磷效果 48

4.3.2 对水质的影响 53

4.4 小结 55

第5章 总结与展望 57

5.1 获得的主要结果 57

5.2 创新点 57

5.3 不足与展望 57

参考文献 59

致 谢 71

作者简历及攻读学位期间发表的学术论文与其他相关学术成果 73