【作者】 刘伟；

【导师】 陈丽杰；

【作者基本信息】 大连理工大学 ， 生物化工， 2009， 硕士

【摘要】 生物吸附是指利用自然界中广泛存在的生物质材料的吸附作用,去除废水中存在的污染物特别是工业废水中的重金属离子的过程。与离子交换、沉淀等传统方法相比,在处理工业废水的过程中,尤其是当处理低浓度工业废水时,生物吸附法具有运行成本低、生物吸附剂回收处理简单、吸附效率高等优势。生物吸附法所具有的这些优势已经成为促进其发展并应用于重金属污染处理的主要因素,近年来,利用酵母细胞作为生物吸附剂来处理重金属废水污染的研究得到广泛开展。具有絮凝能力的细胞很容易与液相分离,这就为大规模处理操作提供了便利,但是目前关于絮凝细胞做生物吸附剂的研究还较少。本文中,选取了一株具有絮凝能力的酵母菌株SPSC01作为生物吸附剂,并对其去除Cr(Ⅵ)的能力进行了研究。实验过程中,对溶液pH值、吸附平衡时间、初始Cr(Ⅵ)浓度,初始菌体浓度和温度等因素进行了考察。实验结果表明pH对于吸附过程影响显著,它不仅影响自絮凝酵母去除Cr(Ⅵ)的能力,同时还影响吸附平衡时间;在最适pH条件下(pH为2.0),30至40℃温度区间内,温度对于吸附过程几乎没有影响。实验过程中分别采取Freundlich和Langmuir两种吸附等温模型对实验数据进行了拟合,拟合结果得到对于以上两种不同的模型,其线性相关系数R~2分别为0.9808和0.9836,这表明吸附过程中即存在单层吸附同时也存在复杂的多层吸附。用硝酸消化法测定菌体表面铬离子的存在形式,发现菌体表面的铬离子全部以三价铬的形式存在,因此可以证实,自絮凝酵母吸附六价铬的过程中存在着氧化还原反应将六价铬还原为三价铬。通过对吸附过程进行动力学研究,得到了一个能够准确描述自絮凝酵母吸附Cr(Ⅵ)过程的准二级反应动力学模型。更多还原

【Abstract】 Biosorption is a process that utilizes inexpensive biomaterials to sequester heavy metals and is particularly useful for the removal of contaminants from industrial effluents.Compared with conventional methods such as ion exchange and precipitation,Biosorption process offers the advantages of low operating cost,minimization of volume of chemical and biological sludge to be disposed of,high efficiency in detoxifying very dilute effluents.These advantages have served as the primary incentives for developing biosorption processes to clean up heavy-metal pollution.Biosorption of heavy metals by yeast cells has been studied extensively in the last decade for wastewater treatment.Although flocculating yeast cells can be separated from liquid phase easily,which is desirable for large scale processes,they have been rarely used in biosorption.In this study,a self-flocculating yeast strain,SPSC01,was utilized for the Cr（Ⅵ） removal. The ability of the self-flocculating yeast SPSC01 to remove Cr（Ⅵ） from aqueous solutions was investigated.Effect of initial pH,contact time,initial concentration of Cr（Ⅵ）,initial concentration of biosorbent and temperature on the biosorption was determined and it was found that pH was a significant factor affecting not only the removal ability of Cr（Ⅵ） by the self-flocculating yeast but also the contact time required for the biosorption equilibrium,with an optimum of 2.0,while no significant impact of temperature from 30 to 40℃on the biosorption was observed.The fitness of the experimental data for the Freundlich and Langmuir adsorption models was further examined and good correlations with R²=0.9808 and 0.9836 were observed,indicating both monolayer biosorption and the presence of heterogeneous surface conditions.Since only Cr（Ⅲ） was detected in the solution after the self-flocculating yeast adsorbed with Cr（Ⅵ） was treated by HNO₃ under high temperature,the mechanism of the biosorption was deduced to be the reduction of Cr（Ⅵ） into Cr（Ⅲ） on the surfaces of the self-flocculating yeast,and a pseudo second-order kinetic model was developed to describe the biosorption process.更多还原