酸性重金属废水/石灰反应结晶工艺基础研究
文献类型：学位论文
| 作者 | 邓立聪 |
| 学位类别 | 硕士 |
| 答辩日期 | 2012-05-28 |
| 授予单位 | 中国科学院研究生院 |
| 授予地点 | 北京 |
| 导师 | 张懿 ; 张亦飞 |
| 关键词 | 酸性重金属废水 石灰乳 反应结晶 硫酸钙 资源化 |
| 其他题名 | Fundamental Research on Reactive Crystallization Process between Acidic Wastewater Containing Heavy Metals and Lime |
| 学位专业 | 环境工程 |
| 中文摘要 | 酸性重金属废水产生量大、pH值低，水中重金属离子种类多、含量高，严重危害人体健康和生态环境，排放至水体中严重影响居民饮用水乃至生命安全，是工业生产过程中的重大污染源之一。治理酸性重金属废水的方法较多，目前生产领域主要采用较为经济的石灰乳中和沉淀法。石灰沉淀法工艺简单，但是中和渣渣量大、含水率高、过滤性能差，沉淀渣中的重金属离子存在二次污染的潜在危害等。深入掌握中和反应过程的化学机理，在低成本条件下提高工艺处理效率、使沉淀渣中重金属高效解吸富集利用成为解决问题的新途径。本论文以石灰乳与酸性重金属废水的反应结晶过程控制为研究对象，开展了硫酸钙晶体成核与生长过程研究，深入分析影响结晶产物晶习的主要因素，并探索中和沉淀渣资源化利用的可行性。论文研究了反应温度、反应物浓度、反应物加入速度、搅拌速度以及酸性重金属废水中主要金属离子对石灰乳-硫酸水溶液反应结晶生成硫酸钙晶体形貌与粒度等的影响。石灰乳与硫酸水溶液反应结晶条件实验表明，不同结晶条件下结晶产物均为二水硫酸钙晶体，且晶体粒径较小。反应温度对晶体形貌的影响最大，温度高于60℃，硫酸钙晶体形貌从片状向棒状转变。根据实际酸性废水的组成，考察废水结晶过程中的主要影响因素Fe3+、Al3+、Mg2+、Zn2+离子对反应结晶过程的影响。低浓度的Fe3+、Al3+、Mg2+离子单独或共同存在于溶液中，硫酸钙晶体形貌均为片状结构， Fe3+、Al3+、Mg2+、Zn2+离子共同存在，硫酸钙晶体由片状转变为针状；Mg2+离子浓度高于0.08 mol/L时，晶体从片状和针状结构转变为棒状结构；Zn2+和Al3+离子促进硫酸钙晶体得到团聚体，不同浓度Zn2+离子单独存在，晶体团聚成花朵状，Al3+离子浓度越大，硫酸钙团聚越明显。结果表明，控制反应温度并调节废水中离子浓度，制取粒径均一且适于沉淀渣过滤以及共沉淀金属离子解吸的硫酸钙晶体的途径有效可行。论文进一步考察了石灰乳二段工艺处理酸性重金属废水及二段沉淀渣清洁利用的可行性。在常温下，利用对一段中和反应结晶过程的控制，能够实现废水中Fe3+离子和其它金属离子的分离。控制结晶过程得到的一段及二段沉淀渣中二水硫酸钙晶体呈针状，针状晶体被金属沉淀物包裹产生团聚。沉淀渣经硫酸洗涤得到较为纯净的针状二水硫酸钙晶体，沉淀物中重金属离子含量低于0.005%，可以作为建筑材料等实现增值利用。洗涤液中主要金属离子Zn2+、Fe3+和Al3+的含量分别达到23390、17840和5126 mg/L，分别为废水中离子浓度的7.80、8.29和5.13倍，实现富集浓缩。研究结果表明，深入控制洗涤工艺，进一步高效解吸和浓缩金属离子，是酸性废水后续有效处理和资源化利用的有效途径。 |
| 英文摘要 | As one of the major sources of industrial pollution, the acidic wastewater containing heavy metals is characterized by large amount of production, low pH, high content of various metal ions and serious toxicity. If inappropriately discharged to the environment, the wastewater may seriously destroy the ecological balance, pollute the water or even threaten the human health and safety. Among the various methods for treating the acidic wastewater, the lime neutralization process is most widely adopted as the consideration of the economical factor. Despite of the advantage of low expense and its simplicity, the filtration operation of this process is rather difficult and the water content of the huge amount of flitration cake is accordingly high, which would lead to a secondary pollution. To solve this problem, a new method of enriching the heavy metals from the wastewater and liberating them from the precipitates based on lime neutralization process was introduced. To better understand the principal of the lime neutralization process and improve the processing efficiency at low expense, the reactive crystallization of the acidic wastewater containing heavy metals with lime was systematically investigated, and the factors that influence the crystal habit and the particle size distribution of the calcium sulfate dihydrate were detailly analyzed, the feasibility of utilizing the precipitates were also investigated. The effect of the parameters of the reactive crystallization, including the reaction temperature, the addition rate and the concentration of the lime, the stirring speed and the main metal components in the water on the morphology and the size distribution of the calcium sulfate dihydrate crystals was studied. And all the precipitated crystals are identified as the phase of calcium sulfate dihydrate with small particle size. The morphology of the calcium sulfate dihydrate is significantly influenced by the reaction temperature which evolves from the platelet or needle structure to the rod structure when the temperature is above 60 °C. Furthermore, the effect of the major metal ions in the industrial wastewater on the crystal habit of the calcium was studied. The morphology of gypsum transformes from the platelet-like shape to the rod-like shape as long as the Mg2+ concentration in the solution is larger than 0.08 mol/L. With the existence of Al3+ and Zn2+ ions in the water, the agglomeration of the precipitated crystals is found to be enhanced, even flower-like shape crystals were obtained with Zn2+ ions. The co-existence of Fe3+, Al3+ and Mg2+ metal ions has no effect on the morphology of calcium sulfate dihydrate, which takes the forms of platelet-like shape from the solutions of low metal ions concentration. However, the morphology of gypsum transfromes from platelet-like shape to the needle-like shape with extra Zn2+ metal ions added. Conclusion can be made that with reaction temperature and metal ions concentration controlled, regular rod structure calcium sulfate crystals which are suitable for metal ions elution could be obtained. The two stage neutralization process of lime with acidic wastewater containing heavy metals was experimently verificated using a semi-batch crystallizer. Through the first-stage treatment at controlled processing conditions, the Fe3+ ions in the wastewater were separated from other metal ions at room temperature. Needle-like calcium sulfate dihydrate aggregated with the metals’ hydroxide precipitates were found after both first-stage and second-stage treatment process. When the precipitates were washed with sulfuric acid, pure needle-like calcium sulfate dihydrate which could be utilized as building materials and solutions with concentrated metal ions which could be re-used in industry were obtained respectively. The contents of main metal ions like Zn2+、Fe3+ and Al3+ in the concentrated solution were 23390、17840 and 5126 mg/L, 7.80、8.29 and 5.13 times of the intial metal ions. The metal contents in the washed precipitates were extremely low, and each kind of heavy metal ion in the washed precipitates was below 0.005 percent. This provided a suitable diagram to obtain highly concentrated metal ions for further recycle from acidic wastewater and the precipitates after appropriate washing and elution process. |
| 公开日期 | 2013-09-25 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1816]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 邓立聪. 酸性重金属废水/石灰反应结晶工艺基础研究[D]. 北京. 中国科学院研究生院. 2012. |
入库方式： OAI收割
来源：过程工程研究所
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