乙醇发酵与渗透汽化在硅橡胶膜生物反应器中的耦合强化

用硅橡胶膜生物反应器(SMBR)实验研究了发酵-渗透汽化的耦合性能。发酵微生物采用酿酒活性干酵母,所用的碳源为工业级葡萄糖。间歇发酵过程由于产物抑制作用在乙醇浓度达到90g稬-1时就趋于停滞,而经耦合渗透汽化膜分离后,发酵罐内的乙醇浓度迅速降低并维持在40g稬-1,且发酵在此浓度下可以连续稳定地进行。 在SMBR运行达到稳态后,乙醇的体积产率为1.5gL-1h-1。SMBR中所用的聚二甲基硅氧烷(PDMS)复合膜由实验室自行制备,它能稳定分离含有酵母细胞的发酵液。当发酵液中乙醇浓度为92.7~49.5g稬-1时,PDMS复合膜的总通量为1490~1164g穖-2h-1,分离因子为6.9~7.8,与分离相同进料浓度的清洁模型溶液相比分别平均高出31%和14%。乙醇发酵和渗透汽化在硅橡胶膜生物反应器中能够相互耦合并得到强化。     

Preparation of high‐performance zeolite NaA membranes in clear solution by adding SiO2 into Al2O3 hollow‐fiber precursor

Zeolite NaA membranes were prepared in a clear synthesis solution without the aid of nanoseeds. To improve the properties of the membranes formed in a clear solution, alumina hollow fibers were fabricated by adding silica powder to the conventional spinning slurry, resulting in hollow fibers with a mullite phase. Prior to the membrane synthesis, the hollow fibers were pretreated by dipping in an aged synthesis solution diluted with isopropanol. Dense zeolite NaA membranes on mullite‐containing alumina hollow fibers were successfully obtained at 100°C for 2 h without the aid of nanoseeds. The membranes have a good pervaporation performance with a high flux of 10.8 kg m^?2 h^?1 and a separation factor of over 10,000. The abundant mullite‐phase hydroxyl groups on the support surface promote the nucleation and growth of zeolite crystals on the support, resulting in dense membranes. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2679–2688, 2018     

乙醇/水及乙酸/水体系的渗透汽化分离

以乙醇/水及乙酸/水体系为研究对象,研究了渗透汽化过程中料液浓度、温度因素对分离效果的影响;结合乙醇、乙酸对聚二甲基硅氧烷(PDMS)膜的溶胀特性差别,分析并讨论了两者在渗透汽化过程中可能的分离机理. 研究表明,PDMS膜能够优先透醇,但乙酸分子的缔合物以及羧基与疏水PDMS膜高分子链的强相互作用降低了其在膜中的扩散速率,使低温时乙酸/水体系优先透水,只有当温度在60℃以上时才表现出优先透酸,且分离效果较差.     

Membrane processing of fruit juices and beverages: a review

Membrane technology for the processing of fruit juices and beverages has been applied mainly for clarification using ultrafiltration and microfiltration, and for concentration using reverse osmosis. The effects of product preparation, membrane selection, and operating parameters are important factors influencing filtration rate and product quality. Technological advances related to the development of new membranes, improvement in process engineering, and better understanding of fruit beverage constituents have expanded the range of membrane separation processes. Developments in novel membrane processes, including electrodialysis and pervaporation, increased the array of applications in combination with other technologies for alternate uses in fruit juices and beverages.     

果汁生产中膜技术的应用

膜技术是一种高效、低能耗和易操作的分离技术,在果汁的生产中得到越来越广泛的应用。概述了膜技术在苹果汁、柑桔汁、山楂汁、葡萄汁、草莓汁等果汁生产中的应用和特点,并展望了膜技术在果汁加工中的应用前景。     

Pervaporation of emulsion droplets for the templated assembly of spherical particles: A population balance model

The emulsion droplet solvent evaporation method is used in the preparation of spherical particles, which form due to processes such as the clustering of nanocrystals or precipitation of polymers as the volume of solvent in the droplets decreases. A population balance model is presented to describe this transport of solvent from nanocrystal‐ or polymer‐laden droplets in an emulsion that flows through a pervaporation unit. The solvent transport and lateral migration of droplets was simulated using a high‐resolution finite‐volume algorithm, which provided a smooth solution with second‐order accuracy. Concentration gradients in the continuous phase become prominent when the resistance to solvent transport in the continuous phase dominates that in the membrane. In contrast, with the membrane resistance controlling the overall transport rate, a lumped capacitance assumption can be made and a simpler plug flow model would be sufficient. The simulations also indicate that the particle‐size distributions are generally bimodal, and are broader for low dispersed‐phase volume fractions and very low‐solvent solubilities. Furthermore, the distributions show that radial diffusion of the particles occurs to a significant degree. Such simulations offer insight into how the solvent is removed from emulsion droplets as they flow down a pervaporation fiber and should be useful in the design of pervaporation systems for that purpose. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3975–3985, 2013     

两步晶化制备高性能a&b取向T型沸石膜

采用廉价的大孔α-Al₂O₃作为载体, 通过二次晶种诱导+两步变温水热合成工艺, 成功制备出薄而致密的高性能T型沸石膜。该方法能够充分发挥晶种的诱导成核作用, 通过改变两阶段水热晶化温度和时间来控制晶种外延生长和晶体生长方向, 最终获得了连续、无缺陷的a&b取向T型沸石膜。实验过程中详细考察了第一阶段的晶化温度、晶化时间以及第二阶段的晶化温度对沸石膜表面结构和性能的影响, 并将最优两步晶化条件下制备的膜用于90wt%的异丙醇/水渗透汽化分离, 在75 ℃下膜的通量为3.84 kg·m ^-2·h ^-1, 分离因子大于10000。     

An experimental investigation on phenol wastewater treatment from coal gasification by pervaporation with NaY molecular Sieve filling membrane

In the experiment,PDMS membrane with NaY molecular sieve filling were chosen as the experimental objects and the flux of phenol and removal efficiency of phenol as evaluation index,the effect of the system operating temperature,the flow rate,liquid membrane downstream pressure,operation time,and filling proportion of NaY molecular sieve on pervaporation treatment efficiency for wastewater from coal gasification were investigated. With the increase of temperature and feed flow rate,pervaporation flux and phenol removal efficiency increases. The decrease of the membrane downstream pressure and elevating NaY molecular sieve filling proportion may result in the increase of flux and then phenol removal efficiency improves. When NaY molecular sieve filling proportion is 45% ,treatment efficiency is the best for coal gasification wastewater containing 1850 mg/L phenol as the flux of phenol was 12948. 23 mg/(h·m2) .     

渗透蒸发过程脱除水溶液中挥发性有机物的研究

采用自制的PDMS膜研究了从VOCs (挥发性有机化合物 )稀水溶液中脱除VOCs的渗透蒸发过程。以分离因子和渗透通量为评价指标 ,考察了料液浓度、温度和流动状况以及膜下游压力对膜的渗透蒸发分离性能的影响 ;并研究了针对脱除水溶液中VOCs的渗透蒸发过程的传质模型。     

底膜对脱硫用羟乙基纤维素复合膜性能的影响

以聚偏氟乙烯为底膜材料,以羟乙基纤维素(HEC)为活性层材料,通过改变底膜铸膜溶液中添加荆的质量浓度.制备出不同的渗透汽化脱硫用HEC复合膜;用催化裂化汽油评价了复合膜的脱硫性能,并对汽油组分在底膜内的传质进行了简单分析.结果表明.添加剂的质量浓度增加,底膜平均孔径增加,孔隙率却稍有降低,但汽油组分在底膜内的传质系数增加.添加剂的浓度增加,HEC复合膜对硫化物的选择性先增加后降低.渗透性则先降低后增加,在添加荆舍量1%时出现极值.