双极膜电渗析法资源化草甘膦生产废水的研究

发布时间：2018-06-23 19:50

本文选题：草甘膦 + 双极膜电渗析　；参考：《中国海洋大学》2013年硕士论文

【摘要】：草甘膦是一种高效广谱低毒性农药，由于近年来转基因作物的扩大种植，草甘膦销量和市场需求迅速增长，目前已成为世界需求量最大的农药之一。统计表明，我国已成为草甘膦的第一生产国。由于原料和工艺知识产权等因素的限制，我国大约70%的草甘膦是通过甘氨酸法生产获得的。然而，通过甘氨酸法生产草甘膦将副产含草甘膦（约1%）和大量盐分（NaCl，约15%）的生产废水。显然，上述生产废水的直接排放将不仅会严重污染环境（如土地盐碱化等），而且也会造成一定程度上的资源浪费。本文设计了一种草甘膦生产废水的资源化工艺，旨在实现草甘膦生产过程的零排放。即，采用双极膜电渗析法处理草甘膦废水，将废水中所含大量的NaCl进行脱盐处理并转变为HCl和NaOH，在回收草甘膦的同时也获得了草甘膦生产过程所必需的酸和碱，进而实现了物料的循环利用和生产过程的零排放。本文首先进行了双极膜电渗析法资源化草甘膦生产废水的实验室小规模实验，初步探索了该工艺的可行性。实验采用国产双极膜、国产异相阳离子交换膜和国产异相阴离子交换膜组成双极膜膜堆，对模拟草甘膦生产废液（即含NaCl15%，含草甘膦1.2%，pH约为11）进行试验。实验过程中的酸碱浓度通过分别以酚酞和甲基橙为指示剂的氢氧化钠和盐酸相互的标准滴定获得，通过电导率仪和pH计监测料液体系的电导率和pH变化情况，通过国标GB12686-2004中的分光光度法在242nm的波长下检测实验中草甘膦的渗漏情况。实验初步证实了该工艺的技术可行性，即实现脱盐并转化为盐酸和氢氧化钠的同时，料液中草甘膦并未向酸室和碱室渗漏。继而，实验中着重考察了所施加的电流密度对资源化工艺的电流效率和能耗的影响，结果证实有一定的工业化可行性，如在70mA/cm~2的电流密度下，以所得的盐酸来计算，电流效率和能耗可以达到63%和10.5kWh/kg。基于此结果，我们进一步核算整个工艺过程的生产成本，结果显示该工艺具有一定的经济可行性。另外，我们也进行了德国双极膜和国产膜的对比试验，结果显示二者的电流效率和能耗等并没有显著差别。进而，本文采用中试规模，考察电流密度、初始酸碱浓度、初始料液盐浓度、电渗析器料液流量等四个独立因素对双极膜电渗析处理草甘膦废水的过程影响，每个因素选取5个水平，采用响应面法优化设计实验。实验结果表明电流密度、初始酸碱浓度、初始料液盐浓度、电流密度和初始料液的盐浓度的交互作用对过程成本有较明显影响，流量和其它因素交互作用等影响不明显。通过优化设计得出实验最佳条件：当电流密度为87.46mA/cm~2，料液室起始盐浓度为14g/100mL，起始酸碱浓度为0.08mol/L，流量为40L/h时，预测实验合理可能最低成本为0.72$/kg，参照电流密度90mA/cm~2最低成本0.7$/kg，模型较准确。从过程成本考虑，国产膜的价格较低，因此我们又换用国产双极膜和国产均相和异相阳膜组成膜堆在电流密度50mA/cm~2，起始酸碱浓度0.04M，盐度14g/100mL，流量40L/h的条件下进行双极膜电渗析处理草甘膦废水实验。在能耗方面的效果并没有很大的差异。但由于膜价格与国外进口膜相差很大，，从过程成本讲国产膜更胜一筹，由于国产双极膜并未大规模商品化，我们只是进行了初步的探索。
[Abstract]:Glyphosate is a highly effective and low toxic pesticide. Due to the expansion of transgenic crops in recent years, the sales of glyphosate and the market demand have increased rapidly. At present, it has become one of the most demanding pesticides in the world. Statistics show that China has become the first producer of glyphosate. About 70% of the country's glyphosate is produced by glycine process. However, glyphosate is produced by glyphosate by glyphosate, which will produce a by-product of glyphosate (about 1%) and a large amount of salt (NaCl, about 15%). It is clear that the direct discharge of the wastewater will not only seriously pollute the environment (such as salinization, etc.), but also cause a certain degree. A waste of resources.
In this paper, a resource process for glyphosate production wastewater is designed to achieve zero emission of glyphosate production process. That is, the treatment of glyphosate wastewater by bipolar membrane electrodialysis is used to remove a large amount of NaCl in the wastewater and convert it into HCl and NaOH, and the process of glyphosate production is also obtained. The acid and alkali are needed to achieve the recycling of materials and zero discharge in the production process.
The feasibility of this process was preliminarily explored in the laboratory of bipolar membrane electrodialysis. The feasibility of this process was preliminarily explored. A bipolar membrane reactor made of domestic bipolar membrane, home-made heterogenous cation exchange membrane and domestic heterogeneous anion exchange membrane was used to simulate the waste liquid containing NaCl15%. Glyphosate 1.2%, pH about 11) was tested. The concentration of acid and base in the experiment was obtained by the standard titration of sodium hydroxide and hydrochloric acid with phenolphthalein and methyl orange respectively. The conductivity and pH changes of the liquid system were monitored by the conductivity meter and the pH meter, and the wavelength of 242nm in the national standard GB12686-2004 was obtained. The experiment preliminarily confirmed the technical feasibility of this process, that is, to realize desalination and transform into hydrochloric acid and sodium hydroxide, while the glyphosate did not leak into the acid chamber and the alkali chamber. In the experiment, the current efficiency and energy consumption of the applied current density on the resource process were investigated in the experiment. The results confirm the feasibility of a certain industrialization. For example, at the current density of 70mA/cm~2, the current efficiency and energy consumption can reach 63% and 10.5kWh/kg. based on the calculation of the hydrochloric acid. We further calculate the production cost of the whole process. The result shows that the process has a certain economic feasibility. In addition, I The German bipolar membrane and domestic membrane were also tested. The results showed that the current efficiency and energy consumption of the two had no significant difference.
Then, this paper uses the pilot scale to investigate the effects of four independent factors, such as current density, initial acid and base concentration, initial liquid salt concentration, and the discharge of electrodialysis, on the process of glyphosate wastewater treatment by bipolar membrane electrodialysis. Each factor is selected at 5 levels, and the response surface method is used to optimize the design experiment. The experimental results show the current density, and the initial results show the initial current density. The interaction between the concentration of acid and base, the initial liquid salt concentration, the current density and the salt concentration of the initial liquid has a obvious influence on the process cost, and the interaction between the flow and other factors is not obvious. The optimum design conditions are obtained by optimizing the design: when the current density is 87.46mA/cm~ 2, the initial salt concentration of the liquid chamber is 14g/100mL, the starting acid is the initial acid. When the concentration of alkali is 0.08mol/L and the flow rate is 40L/h, the lowest cost of the prediction experiment is 0.72$/kg, and the minimum cost of the current density 90mA/cm~2 is 0.7$/kg, and the model is more accurate.
Considering the cost of the process, the price of the domestic film is low, so we have replaced the domestic bipolar membrane and homemade homogeneous and heterogeneous positive film in the current density 50mA/cm~2, the initial acid base concentration of 0.04M, the salinity 14g/100mL, the flow 40L/h, and the treatment of glyphosate wastewater by bipolar membrane electrodialysis. However, because the price of the membrane is very different from that of the foreign imported film, it is better to tell the domestic film from the process cost. Because the domestic bipolar membrane is not commercialized on a large scale, we have just carried out a preliminary exploration.
【学位授予单位】：中国海洋大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：X703

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