海藻对水体中重金属的吸附研究

IOCAS-IR > 海洋环流与波动重点实验室

	海藻对水体中重金属的吸附研究
	潘进芬
学位类型	博士
	2000
学位授予单位	中国科学院海洋研究所
学位授予地点	中国科学院海洋研究所
学位专业	海洋环境化学
关键词	海藻吸附机理重金属离子
摘要	本文研究了三种大型藻及五种微藻的死藻体对水体中重金属离子的吸附。从藻细胞的形态学和光谱学以及咐附动力学和热力学等角度，探讨了海藻对金属离子的吸附机理。获得了吸附的适宜条件，为生物吸附剂在实际生产中的开发利用提供了生理基础。实验主要结果为：通过藻体死细胞与活细胞吸附研究比较，得出：藻体细胞的死亡不但不影响其吸附能力，而且可以解决用活体细胞作生物吸附剂进行工业废水处理的许多困难（如藻的营养问题、藻细胞对金属的耐受力等问题）。以死亡藻细胞作为生物吸附剂的细胞固定化技术有很大的工业应用前景。从藻细胞形态学和荧光发射光谱的研究得出，海藻对重金属的吸附不仅靠细胞壁成分对金属离子进行作用，细胞的内部物质也积极地参与吸附。吸附前后的细胞不仅表面强烈变形（变得凹凸不平），而且细胞的深层结构也发生了变化，使细胞的荧光发射光谱发生改变；未经吸附的藻细胞在紫光外激发下发出清晰的荧光，吸附之后荧光削弱甚至消失。吸附的热力学研究得出，吸附过程符合Freundlich吸附等温方程q = kc~b，可以认为该方程是少洋藻类－尤其是单胞藻吸咐金属的普遍模式。海藻对金属离子的吸附过程是多个一级反应并行的反应。藻体细胞存在着多个吸附官能团，这些官能团大致可以总括为快速吸附位点、中速吸附位点和慢速吸附位点三大类，实验模拟得出藻细胞吸附金属离子的动力学公式：C_e = Σ_(c_i) = C_(01)e~(-k1t) + C_(02)e~(-k2t) + C_(03)e~(-k3t)，式中 k_1，k_2及k_3 代表三类吸附位点的反应速率常数。吸附的条件研究表明，吸附反应有一个最佳吸附温度和酸度，温度和酸度值过高或过低都不利于反应的进行；对于所实验的藻种，最佳吸附温度约为40 ℃，最佳吸附pH值在6.4左右。离子强度低利于吸附的进行。离子强度越高，藻对金属子的吸附量越低。当其它条件相同、离子强度由0.0016增至0.047，吸附容量减小了9倍。原因是各离子之间对吸附位点的竞争吸附，这种竞争关系决定了离子强度高时吸附空量较低。藻类对金属的吸附能力和金属离子的化学本质有密切的关系。各官能团对离子进行选择吸附，多种离子共存时，相互之间是竞争关系，这种竞争关系从侧面解释了低离子强度利于吸附进行的现象。各共存离子的吸附量及优先选择性主要决定于离子的软硬酸度。
其他摘要	The accumulation of heavy metals by algae has been studied extensively for biomonitoring or bioremediation purposes. It is found that the accumulation of heavy metals by algae is one of the most effective methods and the research on this has been performed more than fifty years. With the advantages of low cost raw material, big adsorbing capacity and no secondary pollution etc., the algae are promising to be used in treating industrial water containing heavy metals. A series of marine algae were tested for their adsorption properties. The mechanism studies illustrated that the non-living algae might have the same or even greater adsorption capacity. From the study of marine algae's adsorption kinetics and thermodynamics, it is found out that: The adsorption process lasted about 24 hours, in which the completion between the metal ions and the functional groups on the surface of and inside the biological material played a major role. During the adsorption processes there are mainly three kinds of parallel reactions that are respectively very fast, fast, or very slow. The process, that contains several first order reactions, may be expressed by the following function: C_e = Σ_(c_i) = C_(01)e~(-k1t) + C_(02)e~(-k2t) + C_(03)e~(-k3t), where k_1, k_2 and k_3 are the reaction constants of these three kinds of reactions. Freundlich equation fitted very well the adsorption isotherms. It is demonstrated that the principal mechanism of metallic cation sequestration involves the formation of complexes between a metal ion and functional groups. These functional groups are present on the surface or inside the porous structure of the biological material, in which carboxyl groups of alginate play a major role in the completion of heavy metals. The optimal pH, which was the major factor influencing the adsorption of the metals, was around 6.4; and the higher the ionic strength, the lower the sobbing capacity. Different species of algae and the algae in the same species have different adsorption capacity. The selection affinity for heavy metals and the retention of physical integrity are two major criteria for the screening of a biologic absorbent to be used in water treatment. The removal rate and sobbing capacity were relative to the chemical properties of the ions. In a co-existing ions system, the ions compete one another during the sorption, and the competition can be explained by "the principle of hard and soft acids and bases". Our study performed on the adsorption mechanism has significantly increased our understanding of the adsorption between algae and heavy metals. To get a thorough understanding of this, we still need further intensive studies. It is also need to carry out more on the immobilization of algae. The modification of algae can improve their mechanical properties. Immobilization of whole cells of microorganisms is one of the most commonly used methods both in fundamental research and industrial processes.
页数	52
语种	中文
文献类型	学位论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/1139
专题	海洋环流与波动重点实验室
推荐引用方式 GB/T 7714	潘进芬. 海藻对水体中重金属的吸附研究[D]. 中国科学院海洋研究所. 中国科学院海洋研究所,2000.

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