| 题名 | 电荷-高分子改性土壤去除有害藻及其环境意义的研究 |
| 作者 | 李梁 |
| 学位类别 | 博士 |
| 答辩日期 | 2014-05 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 潘纲 |
| 关键词 | 有害藻 改性土壤 辣木籽 壳聚糖 絮凝 Harmful algal blooms modified soil moringa oleifera chitosan flocculation |
| 其他题名 | Harmful algal blooms removal using charge-polymer modified soil and its environmental implications |
| 学位专业 | 环境工程 |
| 中文摘要 | 本文根据传统单组份改性粘土矿物除藻方法的缺点与不足，结合电荷改性与高分子改性的功能与作用，提出了电荷-高分子双组份改性土壤方法，以实现在多种水体环境下对不同有害藻的有效去除。并在室内研究的基础上，将这一方法应用于现场，考察了其实际除藻与水质改善效果，及由此而引发并促进的生态修复效应，从而为长效控制有害藻暴发提供理论与技术支持。 根据本文研究内容，主要取得了以下五方面的研究结果： （1）首先以辣木籽提取液（MO）-壳聚糖改性土壤为例，研究了电荷-高分子双组份改性土壤方法对赤潮有害藻——强壮前沟藻、海洋小球藻与水华优势藻种——铜绿微囊藻的去除效果。结果表明：MO作为一种高等电点物质，通过改性能将土壤颗粒等电点由pH4.5提升至pH10.5，这使其在天然水体的pH条件下，仍能具有正电荷，从而能中和藻细胞表面负电荷并将其脱稳。但与其它电荷改性剂相似，通过电中和自凝聚的藻细胞絮体较小（20-100 μm），往往需要较长的沉降时间或仍然悬浮在水体中。然而，当这些脱稳絮体被高分子絮凝剂——壳聚糖通过吸附架桥作用连接之后，能迅速增长粒径，在30 min内，这三种有害藻去除率均能达到90%以上。 （2）MO-壳聚糖双组份改性土壤结合了两种改性剂及土壤颗粒物三种物质的三种功能：MO改性使土壤颗粒物带有正电荷，中和藻细胞表面负电荷并使其脱稳，形成小絮体，这不仅为壳聚糖的吸附架桥功能创造了良好的条件，使絮体粒径迅速增长，而且也提高了整体的去除率，而土壤颗粒增加了颗粒物间的碰撞频率与絮体重量，进一步促进了絮体在天然水体中的沉降。在电荷、架桥网捕、有效碰撞这三种作用的协同下，有望实现对不同水体、种类、藻细胞大小、形状、游动性及表面性质的有害藻高效去除。 （3）颗粒物表面电荷对壳聚糖絮凝效果影响的定量研究表明，藻细胞Zeta电位对壳聚糖的絮凝行为有重要影响。当颗粒物电负性较强时，壳聚糖由于电荷密度相对较低，对此颗粒物基本没有絮凝作用。但过于降低颗粒物电负性，壳聚糖正电荷基团与藻细胞间相互吸引作用将会降低，也不利于壳聚糖吸附架桥功能的发挥，形成大的絮体。因此，对于双组份改性土壤除藻而言，经过电荷改性后，藻细胞Zeta电位最优区间为-20.7 mV ~ -6.7 mV，在此范围内最有利于壳聚糖吸附架桥作用的发挥，30 min内去除率能达到80%以上，并且絮体粒径也大于350 μm。这一结果为双组份改性土壤组分配比、效果预测及现场实施提供了理论依据与指导。 （4）溶菌酶或菠萝酶与壳聚糖改性土壤去除有害藻的实验表明，高等电点的蛋白质能发挥与MO相似的作用：中和藻细胞表面负电荷，使其脱稳、凝聚并形成小絮体，提高去除率的同时，也为壳聚糖吸附架桥创造较好的条件，使絮体迅速增长，加速沉降。这一结果可将电荷改性剂如MO扩展至具有相同功能的、自然界广泛存在的蛋白质，从而极大的拓宽了双组份改性方法在不同区域的适用性。为保证有效地电荷改性作用，蛋白质等电点应当不低于9.5。 （5）电荷-高分子双组份改性土壤除藻现场实验表明，400 m2、1.5 m深的藻型水体经过处理后，在第二天能实现清澈见底。由于藻细胞对营养盐的吸收与吸附，其沉降的同时也去除了其它污染物，处理区域TN、TP、Chl-a、CODMn的去除率均在90%以上，溶解性污染物含量也有一定的降低，并将水体营养状态由重度富营养化降低至中营养水平。水体生境的改善，促进了生态系统的修复，在工程实施1年后，与对照相比，处理区沉水植物已顺利恢复，生态结构多样性显著提升。 |
| 英文摘要 | Responding to the limitations and drawbacks of traditional single component modified soil/clay for harmful algal blooms (HABs) removal, this paper proposed a bi-component modification method using proteins with high iso-electric point and chitosan. The main objective of this study was to develop a method or theory for universal removal of different HAB species in different water conditions. According to the laboratory results, this method was also applied for the practical HABs control, the removal efficiency of HAB cells and other pollutants and the induced ecological restoration effect was evaluated. Five main results were obtained in this paper: (1) Moringa oleifera seed extract (MO) with cationic proteins was firstly combined with chitosan to modify soil collected from beach of Lake Taihu, the removal efficiency for the Amphidinium carterae (A.C.) and Chlorella sp. (C.S.) in sea water and Microcystis aeruginosa (M.A.) in fresh water was calculated, and the flocculation mechanism was also studied. Results suggested that the isoelectric point of soil was largely increased from pH 4.5 to 10.5 after been modified by MO. However, when soil was modified by MO alone, maximum removal efficiencies of 80% and 20% for A.C. cells and C.S. cells in sea water and 60% for M.A. cells in fresh water were achieved in 30 min. The limited removal improvement was due to the form of only small flocs (20−100 μm) by surface charge modification only. Large flocs (270−800 μm) and high removal rate of 96% A.C. and C.S. cells and 90% of M.A. cells were achieved within 30 min when the small MO-algae-soil flocs were linked and bridged by chitosan. The optimized dosage of modified soil depends on the property of algal cells and water conditions. (2) The bi-component modification method combined three functions of the two modifiers and soil particles: MO modification made soil particles possess net positive charge in natural waters to enhance their ability to distabalize the cell suspension, which not only created the optimized opportunity for chitosan to link them into large flocs , but also increased the removal efficiency since chitosan works better for less negatively charged small flocs. The soil particles increased the collision frequency and improved the floc weight, which also speed up the sedimentation process after flocculation. To this end, when the soil is modified by the bi-component mechanism of surface charge and netting-bridging modification using biodegradable modifiers such as MO and chitosan, high removal efficiency was achievable to different HAB species with different shape, size, motility and surface properties in different water conditions. (3) Surface charge of algal cells affected the flocculation behavior of chitosan. Results suggested that the optimal removal efficiency was obtained when the zeta potential of M.A. cells was between -20.7 mV and -6.7 mV with a removal efficiency of more than 80% in 30 min and large floc size of > 350 μm. When the algal cells were more negatively charged than -20.7 mV, the effect of chitosan modified soil was depressed (< 60%) due to the insufficient charge density of chitosan to neutralize and destabilize the algae suspension. When the algal cells were less negative than -6.7 mV or even positively charged, the attractive force between positively charged groups of chitosan (-NH3+) and particles was decreased and hence small floc size (< 120 μm) were formed, which may be difficult to sink under natural water conditions. These results provided the theoretical basis and guideline for modifiers preparation, efficiency prediction and practical cyanobacteria removal when using the bi-component modification method. (4) The other proteins with high iso-electric point, lysozyme (pI ≈ 11) and bromelain (pI ≈ 9.5) were used to modify soil jointly with chitosan. Results suggested that 5 mg/L lysozyme and 100 mg/L bromelain modified 10 mg/L soil can both reduce the zeta potential of M.A. cells from -26 mv to -10 mv and remove 73% and 60% of algal cells in 30 min, respectively. The limited improvement of removal efficiency was due to the small flocs (< 60 μm) formed by charge neutralization, which need more than 90 min to settle in static condition. However, when the small flocs were linked and bridged by chitosan, large flocs of about 800 μm and 300 μm were fomed and more than 80% of algal cells were removed in 5 min and 30 min by lysozyme-chitosan modified soil and bromelain-chitosan modified soil, respectively.The lower removal ability of bromelain-modified soil was due to the lower charge density leading to less powerful in destabilization of algal cells. These results greatly expanded the MO to widely existed proteins, it is possible to develop new and biodegradable modifiers from natural and renewable sources local availably. (5) The field experiment using bi-component modification method suggested that after the cyanobacteria removal for one day (Area: 400 m2, depth: 1.5 m), the water transparency was increased to more than 1.5 m. Due to the sedimentation of HAB cells which enriched or absorbed the pollutants, the removal efficiency of total nitrogen (TN), total phosphorus (TP), Chlorophyll a and CODMn was more than 90%, other dissolved pollutants were also decreased. The water quality improvement induced the ecological restoration, after one year of the engineering, compared to the control area, the submerged macrophytes have been successfully restored and the ecological diverse index was also significantly increased. |
| 公开日期 | 2015-07-08 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.rcees.ac.cn/handle/311016/15620]  |
| 专题 | 生态环境研究中心_环境水质学国家重点实验室 |
| 推荐引用方式 GB/T 7714 | 李梁. 电荷-高分子改性土壤去除有害藻及其环境意义的研究[D]. 北京. 中国科学院研究生院. 2014. |
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