污水中镉离子联合吸附技术研究

发布时间：2019-05-17 19:24

【摘要】：随着我国社会经济的迅速发展,水体污染越来越严重,重金属污染问题尤为突出。镉离子已被世界卫生组织确定为优先研究对象,在我国的国家环保法中规定不得用稀释法来处理镉,由此可见镉污染问题在全球范围内影响之大及被重视程度。处理金属镉离子的方法有化学沉淀法、物理吸附法和生物吸附法等。其中物理吸附法是最常用的处理法,其优点是材料易得,操作简单,工艺流程简洁,并且成本低。常用的吸附材料有沸石、活性炭、润土、陶粒等,生物质炭是目前研究比较热门的新型吸附材料。但一种填料的吸附效果有限,往往需要通过对吸附材料改性来提高吸附材料的性能,这就大大增加了吸附法的运行成本,并且运行操作也更加复杂。如果多种吸附材料联用使用能提高吸附效果,那么在处理污水时可以大大节约运行成本和简化运行操作。本论文选用活性炭、沸石和生物质碳作为吸附材料,通过静态吸附实验,研究了在不同时间、p H值、固液比、温度和初始镉离子浓度等条件下,不同吸附材料吸附镉离子效果的影响,并且通过单元柱模拟污水处理实验,讨论不同吸附材料及其组合对镉离子去除的影响,筛选出处理镉离子的最佳组合。研究表明:活性炭在吸附20min时镉吸附率即可达到99%,在吸附时间为1h时达到吸附平衡,镉离子去除率达到99.5%;沸石和生物质炭都是在吸附1h时达到吸附平衡,镉离子的去除率分别为99.75%和95.25%。在不同的p H条件下,低p H值对沸石吸附镉的影响较大,p H值为3时,沸石对镉离子的去除率为83.57%,p H值在5~10范围内时,沸石对镉的吸附呈现先增大后减小的趋势,在p H为7时达到最大值99.22%;p H值3~6范围时,生物质炭对镉吸附能力受到的影响产生小幅度波动;在p H为8~10范围内生物质炭受p H值的影响较小,对镉的吸附率稳定在95.23%左右;活性炭受p H的影响较小。沸石和活性炭对于镉的吸附在固液比为3左右时达到了吸附平衡,而不同固液比对生物质炭的影响不是很明显。在温度的影响下,生物质炭和沸石对镉的吸附能力随温度的升高而变化不大;而活性炭对镉的去除率随着温度的升高而呈现先升高后降低的趋势。沸石对镉饱和吸附量达到3.205mg/g。三种吸附材料对镉离子的吸附都可以用准二级动力学模型描述,并且均符合Langmuir吸附等温式,沸石、生物质炭和活性炭的R2分别为0.9872、0.9422和0.9911。多种吸附材料联合吸附显著提高了污水中镉的去除率,对比三种吸附材料不同组合形式对镉去除效果发现,吸附材料最佳组合形式是沸石—活性炭—生物质炭,其对镉离子的去除率达到85%。
[Abstract]:With the rapid development of social economy in China, water pollution is becoming more and more serious, especially heavy metal pollution. Cadmium ion has been identified as a priority research object by the World Health Organization. It is stipulated in the national environmental protection law of our country that the dilution method should not be used to deal with cadmium. It can be seen that the problem of cadmium pollution has a great impact on the global scope and has been attached importance to. The methods of treating metal cadmium ions include chemical precipitation method, physical adsorption method and biological adsorption method. Physical adsorption method is the most commonly used treatment method, which has the advantages of easy availability of materials, simple operation, simple process flow and low cost. The commonly used adsorption materials are zeolites, activated carbon, moisturizing soil, ceramsite and so on. Biomass carbon is a hot adsorption material at present. However, the adsorption effect of a kind of packing is limited, so it is often necessary to improve the properties of the adsorption material by modifying the adsorption material, which greatly increases the operating cost of the adsorption method, and the operation is more complex. If the combination of various adsorption materials can improve the adsorption effect, then the operation cost can be greatly saved and the operation can be simplified in the treatment of sewage. In this paper, activated carbon, zeolites and biomass carbon were used as adsorption materials. The, p H value, solid-liquid ratio, temperature and initial cadmium ion concentration at different time were studied by static adsorption experiments. The effects of different adsorption materials on the adsorption of cadmium ions were discussed by simulated sewage treatment experiment by unit column, and the best combination of cadmium ions treatment was selected by discussing the effects of different adsorption materials and their combinations on the removal of cadmium ions. The results show that the adsorption rate of cadmium can reach 99% when 20min is adsorbed by activated carbon, the adsorption equilibrium can be reached when the adsorption time is 1 h, and the removal rate of cadmium ion can reach 99.5%. Both zeolites and biomass carbon reached adsorption equilibrium at 1 h, and the removal rates of cadmium ion were 99.75% and 95.25%, respectively. Under different pH conditions, the low pH value has a great effect on the adsorption of cadmium by zeolites. When the pH value is 3, the removal rate of cadmium ions by zeolites is 83. 57%, and the pH value is in the range of 5: 10. The adsorption of cadmium by zeolites increased at first and then decreased, and reached the maximum value of 99.22% when pH was 7. When the pH value is 3 鈮，

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