【作者】 李璐；

【导师】 杨朝晖； 曾光明；

【作者基本信息】 湖南大学 ， 环境工程， 2010， 硕士

【摘要】 水体中重金属污染监测与防治一直是环境科学研究的热点。人们不断地开发、改进治理重金属废水的方法和技术,产生了如物理法、化学法、生物化学法等处理方法。生物吸附法处理重金属废水是一种很有潜力的新型重金属废水处理技术。它具有在低浓度下金属离子可以被选择性去除、处理效率高、pH值和温度条件范围宽、投资小、运行费用低以及可有效地回收一些贵重金属等优点。本文用沙田柚废弃果皮制备出一种对重金属离子有很好吸附性能的生物质吸附剂。研究了该吸附剂对Pb2+的吸附性能。采用Plackett-Burman(P-B)法和中心复合设计(Central Composite Design,简称CCD)对影响柚皮吸附Pb2+的6个条件进行筛选优化.P-B实验设计与统计学分析表明：pH值、Pb2+初始浓度、吸附剂用量是影响吸附率的3个关键因素.以吸附率为响应目标,对3因素进行中心复合设计,并经响应面法优化分析得到影响吸附率的二阶模型,确定了Pb2+吸附实验的最优操作条件：pH值5.4,Pb2+初始浓度为265.86 mg/L,吸附剂用量为2.56 g/L,实测吸附率达到92.47%,吸附量为96.01 mg/g；选用聚乙烯醇(PVA)+海藻酸钠(SA)复合体系对游离态生物质吸附剂进行固定化,在保持较高吸附率的前提下,以载体的机械强度和通透性为指标考察各固定条件对载体性能的影响。首先通过单因素实验观察了PVA浓度、海藻酸钠浓度、CaCl2浓度和柚皮粉含量对制备固定化生物质吸附剂的影响,以单因素实验结果为参考,用响应面法对固定化条件进行了优化。由Analysis模块拟合出了方程。模型显著性较好,拟合值和真实值之间的符合程度较好。通过Optimization Numerical Solution求最优解,结果为PVA浓度9.45%,SA浓度2.8%,CaCl2浓度1.7%,柚皮粉含量25wt%,对应的机械强度为45.73g/mm2,通透性达42.38%,而验证试验测得的机械强度为为43.94 g/mm2、通透性为42.12%,与预测值符合程度较好。更多还原

【Abstract】 Detecting prevention and curing heavy metals in water are always the hotspots in the study of environment science. Techniques in treating the heavy wastewater were exploitured and meliorated, such as physical, chemic, biologic and so on. Biosorption of heavy metal is a new potential technology to treat wastewater containing heavy metal. It has many outstanding advantages:selectivity of heavy metal ions from the low concentration wastewater, high efficiency, wide range of pH and temperature, low investment and recovery of some precious metals.In the present work, citron peel was prepared into a metal ion adsorbent with good performance.The Pb2+ adsorption capability of the adsorbents was investigated. Plackett-Burman (P-B) design and Central Composite Design (CCD) were applied for optimizing 6 factors for the biosorption of Pb2+.The P-B design and its following statistic analysis indicate that the pH,initial Pb2+ concentration,and adsorbent dosage were the 3 key factors significantly influencing the Pb2+ removal. Considering biosorption as the response objective,the quadratic model was obtained by CCD for the 3 factors with the analysis of response surface optimization. At the optimal biosorption conditions,i.e. pH5.4,initial Pb2+concentration265.86mg/L,adsorbent dosage2.56g/L, the Pb2+ removal achieved 92.47%,96.01 mg/g.PVA and sodium alginate were used for citron peel immobilization.Maintaining a high absorption rate in the premise,effect of preparation conditions on mechanical strength and permeability of immobilized biosorbent were studied. Firstly, the PVA concentration, sodium alginate concentration,CaCl2 concentration and entrapped amount were studied by single factor test. Then, according to the result of single factor test, condition of immobilization was optionlized by response surface method.Equation is fitted by analysis model, and the model is significant with acceptable errors.Fitting values of the model accord with actual values. The optimal solution is obtained by Optimization Numerical Solution:PVA9.45%,sodium alginate2.8%, CaCl21.7%, the amount of citron peel powder 25wt%, Corresponds to the mechanical strength of 45.73g/mm2, the permeability of up to 42.38%,which accords with the actual value.(the mechanical strength was 43.94g/mm2, the permeability of 42.12%)更多还原