胡萝卜中β-胡萝卜素提取工艺的优化研究

采用有机溶剂浸泡法从新鲜胡萝卜中提取β-胡萝卜素,比较不同提取剂的提取效率,确定提取效率较好的提取剂,并优化了提取工艺条件(如提取剂、料液比、提取温度、提取时间等).结果表明,采用丙酮:甲醇(体积比)=7 ∶2的混合溶剂作为提取剂,在料液比(g:mL)为1∶4、提取温度为40℃的条件下提取1h,再用石油醚萃取2次,提取...     

络合萃取法处理6-硝基间甲酚废水

采用络合萃取法处理6-硝基间甲酚废水,一次萃取率达到99.9%,最佳的萃取条件为V(络合剂)∶V(稀释剂)=1∶2,萃取油水体积比为1∶2,溶液pH值低于3。萃取剂可经过反萃再生其效率不变。     

Removal of As(V) by PVDF hollow fibers membrane contactors using Aliquat-336 as extractant

In this work, the removal of As(V) from an aqueous stream by non-dispersive solvent extraction in a hollow fibre membrane contactor was investigated. To this purpose, microporous hydrophobic poly(vinylidene fluoride) hollow fibres were prepared by the dry/wet spinning technique. Fibres were spun, changing the pore forming additives, to obtain micro-porous sponge-like structure membranes, with pore diameters of about 0.2 μm and porosity of 80%. The produced fibres were used to perform As(V) extraction experiments in a membrane contactor device, using Aliquat-336 as extractant. Different tests were carried out in order to study the effect of temperature, initial concentration, pH of the feed solution and membrane properties. The results showed that the extraction of As(V) by non-dispersive solvent extraction was influenced by the pH of the feed, with an optimum reached for neutral values, increased with the arsenic content in the feed and was not affected by temperature. The extraction was favoured by working with thinner membranes. The highest removal of arsenic achieved was around 70% after 6 h of operation. The produced fibres kept their performance for all the experimental activity, giving reproducible results with time.     

氮化硅在水和乙醇中的摩擦化学机理研究

在往复试验机上考察了Si_3N_4在干摩,水和乙醇润滑条件下的摩擦磨损性能,用SEM,XRD和XPS研究了Si_3N_4在水和醇中的摩擦化学反应机理。结果表明,Si_3N_4的摩擦系数和磨损体积随润滑环境的不同有如下顺序:干摩擦>水润滑>乙醇润滑。Si_3N_4在水中的摩擦化学机理涉及两个方面,一是Si_3N_4与水直接反应生成SiO_2;二是Si_3N_4与溶于水中的氧反应生成无定形Si-O化合物。Si_3N_4在醇中的摩擦化学机理为:Si_3N_4先与乙醇反应生成SiO_2,部分SiO_2与乙醇进一步反应生成硅酯。     

Experimental and Theoretical Studies of Actinide and Lanthanide Ion Transport Across Supported Liquid Membranes

In this work, we propose a new transport mechanism for metal ions relevant for used nuclear fuel separation processes by a supported liquid membrane (SLM). Two SLM extraction systems were investigated where the membrane was impregnated with either di-(2-ethylhexyl)phosphoric acid (HDEHP) or tributyl phosphate (TBP). A HDEHP impregnated membrane was used to extract neodymium (III), representative of a typical trivalent lanthanide. Cerium, which was oxidized by sodium bismuthate from trivalent to tetravalent state, was extracted by TBP. Oxidized cerium was used as a surrogate for oxidized americium to investigate the kinetics and possibility of americium and curium separation by membrane extraction. Both extraction systems were operated at varying nitric acid concentrations, and changes in the kinetics and extraction efficiency of metal ions were investigated. The proposed transport mechanism that was chosen for our studies was modified from the previous works by Danesi et al.^[1,2] and Cussler et al.^[3] The mechanism was selected due to the ability to accommodate and describe transport phenomena across a SLM when formation of extractant nano-channels in the membrane may exist. We were able to obtain acceptable fit of the models to our overall data trends although chemical and physical conditions must be well established and purity and homogeneity of the membrane are critical. A reverse transport of metal ions was observed when leaving the system for longer times which agrees with our model. The membrane was investigated for degradation and shown to be stable after contact with up to 7 M nitric acid for over 2000 minutes. Finally, we examined the possibility of partitioning americium from curium using a SLM impregnated by TBP. Separation of americium from curium was observed although not to a degree that was expected based on the Ce(IV) transport. Incomplete oxidation of Am(III) to Am(V) and reduction of Am(VI) on the membrane surface are possible causes for this observed discrepancy. Our model was, however, able to accurately predict Cm(III) transport through the membrane.     

膜萃取防止溶剂污染的优势

本文以３％ＴＢＰ／苯酚／水为实验体系在不同的膜器中对膜萃取过程中料液对萃取剂的夹带,即溶剂的二次污染进行了研究。在保持膜两侧压降不变的情况下对进口和出口处料液的ＣＯＤ值进行了测定,并与传统的溶剂萃取方法相比较。结果表明,膜萃取中料液中溶剂只有少量的夹带,并且夹带量与操作条件和膜构件基本无关。     

高粘度润滑油馏分油溶剂精制小试对比

针对某炼厂高粘度润滑油馏分油进行了糠醛溶剂的单级抽提试验,并借助数学手段,确定了糠醛精制的最优操作条件.在此基础之上,进行了糠醛精制假三段抽提试验,确定了其适宜的操作条件,并与NMP精制进行了对比.试验结果表明,糠醛单级抽提适宜操作条件为:抽提温度115℃,剂油比1.8(V/V);在该操作条件下,精制油60℃折光率为1.462 8,油收率为83％;糠醛假三段试验适宜操作条件为:上段温度115℃、中段温度100℃、下段温度85℃,剂油比1.8(V/V).在该操作条件下,精制油60℃的折光率为1.460 9,油收率为84％;馏分油糠醛抽提与NMP抽提相比,在精制效果相当的情况下,无论单级还是假三段抽提,NMP精制的温度下降25℃,剂油比下降30％,油收率提高至少3个百分点,说明NMP作为抽提溶剂要优于糠醛.     

鼓气膜吸收法海水提溴研究

以开发高效节能的提溴工艺为目的,设计了鼓气膜吸收法海水提溴过程,压缩空气透过第1级聚偏氟乙烯中空纤维疏水膜,鼓泡进入含溴水溶液,将溴吹脱出来,含溴气体透过第2级膜进入吸收液被吸收;试验考察了各因素对膜吸收提溴性能和传质系数的影响.结果表明,传质系数随吸收液体积、装填密度和鼓气强度的增加而增大,但随温度变化不明显;装填密度15.71%,吸收剂碳酸钠与尿素的量比为3:1时提溴效果最好.鼓气膜吸收法对浓海水提溴有90%以上的脱除率,操作参数优化后,溴的吸收率可达99.6%,回收率可迭89%.     

Extraction of alcohol using emulsion liquid membrane consisting of paraffin oil as an organic phase and lecithin as a surfactant

BACKGROUND: This paper reports on the use of a liquid emulsion membrane involving paraffin light oil as membrane phase and lecithin as surfactant for the extraction of alcohol from anthocyanin extract and simulated pineapple wine. RESULTS: The extraction of alcohol was found to depend on the many factors such as surfactant concentration, contact time, stirring speed, stirring time, and ratio of membrane emulsion to feed volume. Results showed that optimum conditions for maximum alcohol extraction (25%) were lecithin concentration 3%, contact time 20 min, stirring speed 250 rpm and ratio of membrane emulsion to feed volume 1:2. Multistage extraction using this liquid emulsion membrane was found to completely remove alcohol from anthocyanin extract and from simulated pineapple wine in seven stages and five stages, respectively. CONCLUSION: This liquid emulsion membrane was found to be a useful method for the extraction of alcohol from aqueous feed. Copyright © 2009 Society of Chemical Industry     

Separation of As(III) and As(V) by hollow fiber supported liquid membrane based on the mass transfer theory

Separation of As(III) and As(V) ions from sulphate media by hollow fiber supported liquid membrane has been examined. Cyanex 923 was diluted in toluene and used as an extractant. Water was used as a stripping solution. The extractability of As(V) was higher than As(III). When the concentration of sulphuric acid in feed solution and Cyanex 923 in liquid membrane increased, more arsenic ions were extracted into liquid membrane and recovered into the stripping solution. The mathematical model was focused on the extraction side of the liquid membrane system. The mass transfer coefficients of the aqueous phase (k _i ) and organic phase (k _m ) are 7.15×10⁻³ and 3.45×10⁻² cm/s for As(III), and 1.07×10⁻² and 1.79×10⁻² cm/s for As(V). Therefore, the rate-controlling step for As(III) and As(V) in liquid membrane process is the mass transfer in the aqueous film between the feed solution and liquid membrane. The calculated mass transfer coefficients agree with the experimental results.