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氨基介孔二氧化硅吸附功能的研究及吸附过程模拟
Study on Adsorption Function of Amino-functionalized Mesoporous Silica and Simulation of Adsorption Process
【作者】 胡智辉;
【导师】 王纪孝;
【作者基本信息】 天津大学 , 化学工程, 2012, 博士
【摘要】 随着现代工业的迅速发展,人类生产活动产生的大量CO2气体和含重金属离子的废水对环境和人类的健康造成了严重的危害。CO2作为一种温室效应的气体,其导致全球气候变暖已经成为了一个全球性的环境问题。同样,重金属离子由于不能被微生物降解、毒性长期持续和不可逆转等,因而如何消除重金属离子危害也成为当今世界环境保护工作的重要问题。吸附法在CO2吸附回收和重金属离子吸附脱除方面有较大的优势,因此具有广阔的应用前景。本论文选用阴离子表面活性剂法合成一系列的带氨基介孔二氧化硅吸附剂用于CO2吸附回收和重金属离子的吸附脱除。其中采用异丁酸、月桂酸、十六酸、碳十二谷氨酸、碳十八谷氨酸为模板剂,带氨基的有机硅烷γ-氨丙基三乙氧基硅烷为助结构导向剂,硅酸乙酯为硅源合成介孔二氧化硅。采用红外上负载的官能团进行表征、利用X射线衍射和高效透射电镜对样品孔道结构和晶型进行分析、低温氮气吸附脱附测量其比表面积、孔容和孔径分布、热重分析样品上负载氨基的量。采用静态法和动态法分别测量其对N2和CO2的吸附量,考察表面活性剂的种类、有机硅烷γ-氨丙基三乙氧基硅烷含量对介孔二氧化硅吸附剂结构、CO2吸附量和CO2/N2吸附分离系数的影响,分别采用升温和抽真空的方法对吸附CO2饱和的样品进行解吸,评价吸附剂的再生性能。同时采用样品C12GluA-APS-0.3吸附脱除水中微量铜离子,测量吸附剂在不同浓度的溶液中对铜离子的吸附速率和吸附量。利用Freundlich和Langmuir吸附等温方程分析铜离子在样品C12GluA-APS-0.3上的吸附形式,采用吸附准一级方程和二级方程分析此吸附过程动力学。在大量探索性实验和条件优化的基础上,选择测量CO2吸附效果最好的样品C12AA-APS-0.2在323.15K下对CO2和N2的吸附等温线,对吸附等温线方程进行拟合,得到吸附等温线参数。在323.15K,0MPa下对CO2/N2混合气进行变压吸附分离。由于数据库不完全、变压吸附过程本身复杂等原因使得变压吸附模拟计算很少报道,本文中我们利用Aspen adsim软件对上述吸附过程进行模拟,选择合适的模拟模型,发现模拟结果能够很好的描述整个吸附过程。为了进一步的应用模拟模型,并进一步建立液相吸附模型,我们用超临界吸附分离的方法分离中药川芎中的有效成分,并对此吸附过程进行模拟。在8.8MPa、323.15K,川芎中的成分被超临界CO2溶解然后再在硅胶吸附剂上进行分离。为了更好的分析和模拟整个吸附分离过程,将川芎组分假设成二元组分,其中轻组分在吸附的过程中获得。利用添加夹带剂的方法对吸附在硅胶吸附剂上的重组分进行解吸,高浓度的重组分被脱附下来,而且其回收率高达85%。同时考察吸附时间、解吸液流速对产品浓度和回收率的影响。最后对模拟数据进行了实验验证,实验数据证明模拟选择模型非常合适,模拟数据和实验数据相符,模拟能够很好的指导实验进行。
【Abstract】 With the development of modern industry, the emission of carbon dioxide andwaste water containing heavy metal ions cause serious harm to the environment andhuman health. Carbon dioxide as a greenhouse gas has become a global environmentproblem and it emission lead to the global temperature increased and the sea-level rise.Removal o f h eavy m etal i ons f rom w aste w ater i s es sential due t o t heirbio-accumulation tendency, toxicity, persistency and non-biodegradability in nature.Adsorption w as c onsidered f or t he b est w ay t o de aling w ith recovery of c arbondioxide and low concentration of copper waste water, and it was used more widely.In this paper, a series of amine-functionalized mesoporous silica were preparedvia an anionic surfactant-mediated synthesis method and applied to CO2adsorptionand deep removal of copper ions from aqueous solution. With isobutyric acid, lauricacid, p almitic a cid, N-Lauroyl-L-glutamic a cid and N-stearoyl-l-glutamic acid asstructure directing agent, γ-aminopropyltriethoxysilane as co-structure directing agentand tetraethyl orthosilicate as silica source. The force of forming the silicamicelle isthe direct electrostatic interaction between the positively charged amino groups inγ-aminopropyltriethoxysilane and the negatively charged head groups in the anionicsurfactant via t he S-N+I-mechanism, and t he a lkoxysilane s ite ofγ-aminopropyltriethoxysilane is co-condensed w ith i norganic pr ecursors (tetrathtylorthosilicate) to form silica wall. The am ine-functionalized mesoporous silica wascharacterized by Fourier transform infrared spectrometer, X-ray diffraction, nitrogenphysisorption and thermogravimetric analysis. The adsorption capacity of samples forCO2and N2was measured using static method and dynamic method. The effects ofthe type of surfactant and the content of γ-aminopropyltriethoxysilane on the structureof mesoporous silica, adsorption capacity for CO2and N2, and adsorption separationfactor of CO2/N2were studied. The saturated adsorbents were regenerated by hightemperature or vacuum, and the regenerative capacity of the adsorbents was evaluated.The C12GluA-APS-0.3sample was also used to remove of Cu2+ions from aqueoussolution, and adsorption capacity for Cu2+and adsorption rate was measured in thesolution with different concentrations. Copper adsorption process had been studiedfrom both kinetic (Pseudo-first-order kinetic and Pseudo-second-order kinetic) and equilibrium (Freundlich and Langmuir) points of view for C12GluA-APS-0.3material.The adsorption isotherms of C12GluA-APS-0.3material for CO2and N2weremeasured at323.15K, and the mixture of CO2and N2was separated by pressureswing adsorption (323.15K,0M Pa) us ing C12GluA-APS-0.3as a dsorbent. Thesimulation of pressure swing adsorption was rarely reported because of a variety ofreasons, aspen adsim software was used to simulate the adsorption process in thispaper, a nd t he a ppropriate s imulation m odel was w ell de scribed t he a dsorptionprocess. In order to further the application of simulation model, the components inLigusticum chuanxiong was separated by adsorption in supercritical carbon dioxide(SC-CO2,8.8M Pa and323.15K), and then the process was simulated using aspenadsim. In order to further used simulation model and built simulation model for liquidphase a dsorption, Ligusticum chuanxiong i s a ssumed t o be a qua si-binary s ystemmade up of s lightly a dsorbed ps eudcomponents a nd s trongly a dsorbedpseudcomponents. The adsorbent was regenerated by adding a strippant in SC-CO2,and t he s lightly adsorbed ps eudcomponents a nd s trongly ps eudcomponents (therecovery of85%) were successfully obtained in the adsorption and desorption step.The effects of the adsorption time and the flow rate of strippant on the concentrationsof t he c omponents i n t he e ffluent a nd t he r ecovery of t he p roducts were al soinvestigated. The w hole a dsorption s eparation process was s imulated with a spenadsim successfully and the amount of adsorbed components on t he adsorbents waspredicted graphically.
【Key words】 adsorption; carbon di oxide; mesorporous s ilica; simulation; supercritical carbon dioxide; Ligusticum Chuanxiong; Aspen adsim;