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煤化工废水中的酚类、多环芳香族和杂环化合物的毒性强且不容易被生物降解，为了降低有毒物质对生化处理单元的影响，须在生化处理单元之前进行预处理。目前萃取预处理过程存在萃取剂选择性单一和溶剂损失大的问题，生化处理过程很难长期稳定运行。设计筛选对酚类污染物具有优良萃取效果，且对杂多环类污染物具有协同萃取能力的萃取剂，提高萃取预处理效果是重要的途径。本文提出了从现有商业化学物质中筛选单组分萃取剂，以及设计混合萃取剂的策略。具体研究内容如下：（1） 建立了现有商品化合物数据库 (Existing Commercial Compounds Database, ECCD)。为避免引入具有未知风险的化合物，基于中国、美国、欧盟的化学物质名录建立了含34,177个化合物的ECCD数据库。采用基团匹配工具开发了基于基团贡献法的化合物物性估算程序，估算了分子的主要物性。物性数据扩充了数据库信息，可以满足分子筛选的需要。（2） 提出了基于数据库检索的候选单组分萃取剂生成策略。将苯酚作为煤化工废水中的酚类代表组分，从ECCD中筛选对其具有良好萃取效果的单组分萃取剂。根据常用脱酚萃取剂物性范围，设置了萃取剂筛选的多个标准，生成潜在的候选分子集合，并进行萃取性能的排序和比较。筛选出的491种候选萃取剂的类别有酮、酯、醚、醇和苯的同系物，不仅与实验中常用的脱酚萃取剂类别一致，而且常用的15种萃取剂也包括其中。以甲基异丁基酮 (Methyl isobutyl ketone, MIBK)为参照萃取剂，候选集中有11个化合物的分配系数m和选择性β和萃取率ρ均高于MIBK，可作为萃取剂实验筛选的参考。（3） 建立了混合萃取剂的设计和筛选策略。从ECCD数据库中分别筛选出382种和219种对酚类和杂多环类污染物具有高效萃取性能的两个单组分萃取剂候选集。通过遍历组合这两个候选集合中的化合物，获得了60857组用于混合萃取剂筛选和优化的二元萃取剂。构建“虚拟组分”简化了废水中的各种污染物，避免了复杂的多组分LLE(Liquid-liquid equilibrium)计算。将混合萃取剂的筛选问题转化为NLP数学优化模型，根据GAMS(General algebraic modeling system)软件优化求解的特点，通过并行计算方法减少了GAMS模型的求解时间。 （4） 以煤气化废水和焦化废水为例进行了萃取剂的配方设计。虚拟污染物和总污染物在两相中的含量偏差以及萃取率偏差在可接受的误差范围内，说明用虚拟组分表示煤化工废水中的污染物具有化学合理性。以MIBK和二异丙醚 (Diisopropyl ether, DIPE)为参考，设定了污染物的萃取率和萃取相含水量约束范围，分别得到390种和333种对煤气化废水和焦化废水有良好萃取效果的二元萃取剂。二元萃取剂主要有“脂肪族（二）酮+”和“芳香族醚酮+”两个系列。主萃取剂和助萃取剂分别是脱酚和脱杂多环萃取剂候选集中综合排序指数比较靠前的化合物。二元萃取剂具有更高的萃取效果和更低的水中溶解度，综合萃取效果优于单组份萃取剂。而且，筛选出的二元萃取剂在比较宽的污染物浓度和温度范围下，对煤化工废水的综合萃取效果优于MIBK和DIPE。（5） 二元萃取剂S1 ~ S5对模拟煤化工废水的萃取实验结果显示，筛选得到的二元萃取剂表现出优于单组分萃取剂的良好协同萃取能力，具有与MIBK相同的一元酚、二元酚萃取率及明显高于MIBK的杂环类污染物萃取率。筛选优化模型计算得到的一元酚、二元酚、杂环类的萃取率与采用ASPEN Plus计算得到的萃取率显示出良好的一致性。说明本文建立的混合萃取剂筛选策略和筛选优化模型具有良好的可行性和可靠性。;The phenols, polycyclic aromatic compounds and heterocyclic compounds, have strong toxicity as well as poor biodegradability, which should be removed in pretreatment process to meet the quality requirements of biochemical treatment. The main problems of pretreatment are poor extraction performance on other pollutants and large solvent loss, resulting that biochemical treatment process is difficult to run stably for a long time. It is important to improve the pretreatment effect by designing and selecting extractants with high-efficiency co-extraction effects on phenolics as well as heteropolycyclics. The strategies of screening pure extractants and blended extractants from existing commercial chemicals were proposed in this paper.The detailed studies are following:（1）The Existing Commercial Compounds database (Existing Commercial Compounds Database, ECCD) was established. In order to avoid candidate extractants with unknown risk, an existing commercial compound database was developed based on the chemical substances lists of China, the United States and the European Union, which totally containing 34177 compounds. The compound property estimation program was developed to estimate the main properties, based on the molecular structure of the compounds, using group contribution method and group matching tool. The properties expands the physical information of the database and meets the needs of molecular screening.（2）A database-based candidate pure extractant generation strategy was proposed. Phenol was set as a representative component of phenols in coal chemical wastewater, and the single-component extractant with good extraction effect for it was screened from ECCD. Multiple standards for extractant screening were set to generate a list of potential candidate molecules, according to the characteristics of the de-phenol extractant commonly used in the industry. The candidate solvents list contains 491 chemical compounds, including ketones, ethers, esters, alcohols, and benzene compounds, not only consistent with the de-phenol extractants commonly used, but also include 15 commonly used extractants. There are 11 compounds having higher partition coefficient m, selectivity β and extraction rate ρ than Methyl isobutyl ketone (MIBK), which was selected as the reference extractant.（3）A design and screening method of blended extractants was proposed. Two pure compound candidates containing 382 and 219 compounds, were screened from the ECCD, with high extraction performance for phenolic and heterocyclic contaminants. 60857 binary extractants were obtained by one-to-each traversing the compounds in two candidate lists. Pseudo-components were constructed to simplify various contaminants in wastewater and avoid complex multiphase LLE calculations. The screening problem of blended extractant was transformed into NLP mathematical optimization model. The model was solved by parallel computing method to reduce the solution time of GAMS model, according to the characteristics of GAMS software optimization solution.（4）Binary extractants for coking and coal gasification wastewate were design. The deviations of content in two phases as well as extraction rate between the pseudopollutant and total pollutants are within the acceptable error range, indicating that pseudo-components can represent pollutants in coal chemical wastewater with chemical rationality. The constraints of extraction rate and solvent loss were set based on methyl isobutyl ketone (MIBK) and diisopropyl ether (DIPE). 390 and 333 binary extractants with good extraction effect on coal gasification wastewater and coking wastewater were obtained respectively. Binary extractants mainly include "Aliphatic (di) ketone +" and "Aromatic ether ketone +" two series. The main solvents and assistant solvents of binary extractants are those top-ranked compounds in de-phenolics and de-heteropolycyclics lists, respectively. The binary extractants have better comprehensive extraction effect on coal chemical wastewater than single extractant, with better extraction effect and lower solubility in water. Furthermore, the binary extractants have better extraction effects on pollutants than MIBK and DIPE in a wide range of pollutant concentration and temperature.（5）The experiment results of the binary extractants S1~S5 on simulated coal chemical wastewater show that the binary extractants screened have good co-extraction ability to replace the single extractants. The extraction rates of monophenols and dihydric phenols are same as MIBK, while the extraction rate of heterocyclic pollutants is significantly higher than MIBK. The extraction rates of monophenols, dihydric phenols and heterocyclic pollutants calculated by the screening optimization model show good consistency with ASPEN Plus. It shows that the screening strategy and screening optimization model of mixed extractant established in this paper have good feasibility and reliability.
|续冉. 煤化工废水萃取剂计算机辅助设计与优化方法研究[D]. 中国科学院大学,2020.|
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