Ultrasound-assisted dynamic extraction of valuable compounds from aromatic plants and flowers as compared with steam distillation and superheated liquid extraction

A method for the extraction of valuable compounds from plants and flowers (viz. laurel, rosemary, thyme, oregano and tuberose) is proposed. The dynamic approach allows go-and-backward circulation of the extractant (ethanol) through the solid sample subjected to the action of an ultrasound probe (thus reducing sample amount and avoiding overpressure). A multivariate optimisation study and application of the optimum values of the variables to kinetics studies show that 10 min is sufficient to obtain extraction efficiencies that greatly surpass those provided by steam distillation for essential oils or superheated liquid extraction for these oils and other valuable compounds, with lower costs and higher quality of the extract. The extraction time of the proposed method is 176–165 min shorter than steam distillation and 31–20 min shorter than superheated liquid extraction, depending on the target compound.     

Modeling and analysis of vacuum membrane distillation for the recovery of volatile aroma compounds from black currant juice

A vacuum membrane distillation (VMD) model has been developed and validated with experimental data. The model consists of an extended transport model for the VMD process and is able to predict the effects of concentration and temperature polarization on the overall process performance. To validate the model, first it was tested with few experimental case studies from literature [S. Bandini, G.G. Sarti, Heat and mass transport resistances in vacuum membrane distillation per drop, AIChE J. 45 (7) (1999) 1422–1433; K.W. Lawson, D.R. Lloyd, Membrane distillation. I. Module design and performance evaluation using vacuum membrane distillation, J. Membr. Sci. 120 (1996) 111–121; A.M. Urtiaga, G. Ruiz, I. Ortiz, Kinetic analysis of the vacuum membrane distillation of chloroform from aqueous solutions, J. Membr. Sci. 165 (2000) 99–110]. Then the VMD model has been validated with experimental data collected from the recovery of aroma compounds from black currant [R.B. Jørgensen, A.S. Meyer, C. Varming, G. Jonsson, Recovery of volatile aroma compounds from black currant juice by vacuum membrane distillation, J. Food Eng. 64 (2004) 23–31]. In this work, recovery of 12 characteristic volatile aroma compounds from black currant juice has been studied. The simulated results from the VMD model, in terms of aroma concentration in the permeate have been compared with those obtained from laboratory experiments. The validated model has been used to study the effects of various process and membrane parameters on the concentration factor. The physical properties of various aroma compounds have been predicted using group contribution method as a function of temperature.     

Chemical pretreatment of feed water for membrane distillation

Membrane distillation was used to produce demineralized water from ground water. The influence of feed water pretreatment carried out in a contact clarifier (softening with Ca(OH)₂ and coagulation with FeSO₄ · 7H₂O) followed by filtration, on the process effectiveness was evaluated. It was found that the chemical pretreatment decreased the membrane fouling; however, the degree of water purification was insufficient because precipitation of small amounts of deposit on the membrane surface during the process operation was still observed. The permeate flux was gradually decreasing as a result of scaling. The morphology and composition of the fouling layer were studied using scanning electron microscopy coupled with energy dispersion spectrometry. The presence of significant amounts of silica, apart from calcium and magnesium, was determined in the formed deposit. The removal of foulants by heterogeneous crystallization performed inside the filter (70 mesh), assembled directly at the module inlet, was found to be a solution preventing the membrane scaling. Presented at the 34th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 21–25 May 2007.     

Antioxidant activity of hydro distillation water residues from Rosmarinus officinalis L. leaves determined by DPPH assays

Rosemary (Rosmarinus officinalis L.) is a perennial herb with an intensive aromatic flavor. Its most important chemical constituents are essential oils (e.g., 1,8-cineole and camphor) and antioxidants (e.g., carnosic acid and rosmarinic acid). The common methods to extract the essential oil of rosemary are steam or hydro distillation. The aim of this work is to investigate the residual antioxidants after hydro distillation, especially rosmarinic acid and carnosic acid. For this purpose, the hydro distillation water residues were analyzed by HPLC-UV. Moreover, the influence of the extraction duration on the concentration of the antioxidants was investigated. Also, the residual amount of these compounds in the leaves was examined. The total antioxidant activity of the extracts and of the pure compounds was determined by DPPH assays. It is shown that after 2.5 h of hydro distillation the amount of rosmarinic acid and the antioxidant activity in the water residue reaches a maximum value. In addition, the yield and the quality of the essential oil were investigated to draw a comparison between steam and hydro distillations of Moroccan rosemary leaves.     

水蒸汽对PtSn／Al2O3催化剂结构及反应性能的影响

比较研究了Ａｌ２Ｏ３负载的铂及ＰｔＳｎ催化剂在氮气及水蒸汽稀释条件下的丙烷脱氢性能,并利用ＸＰＳ及氢脉冲吸附对催化剂进行了表征。结果表明,水蒸汽可促使Ｐｔ／Ａｌ２Ｏ３催化剂的铂晶粒烧结。与在氮气氛中相比,在水蒸汽存在下反应显著提高了Ｐｔ／Ａｌ２Ｏ３的丙烷转化率,却降低了丙烯的选择性。另一方面,水蒸汽可调变ＰｔＳｎ／Ａｌ２Ｏ３催化剂的结构,破坏了ＰｔＳｎ／Ａｌ２Ｏ３中与锡相互作用的铂簇团结构。从而导     

一种纳米TiO2粉体防团聚的新方法

开发了一种新的低成本防团聚方法——泡沫悬浮法。对泡沫悬浮法和共沸蒸馏法的防团聚效果进行了系统比较。结果表明，泡沫悬浮法可以有效抑制煅烧过程中纳米TiO₂晶粒的粗化和一次粒径的长大。泡沫悬浮法所得纳米TiO₂的粉体还具有团聚粒径小、粒度分布窄以及比表面积大的优点。通过FTIR、TG、DTA和松装密度实验对泡沫悬浮法的防团聚机理进行了研究，提出了纳米TiO₂防团聚模型。     

辛酸亚锡对氧化锌催化制备丙交酯的影响

用减压蒸馏法合成了丙交酯,在反应的不同时间段加入辛酸亚锡,可使丙交酯最高馏出温度降低至197 ℃。 采用红外光谱表征了丙交酯,测定了反应体系的表面张力和黏度,结果表明,脱自由水后的乳酸、脱自由水后加氧化锌和脱自由水后加氧化锌和辛酸亚锡体系的表面张力分别为38.8、47.0和40.3 N/m;黏度分别为43.1049、59.6774和48.9376 mPa·s。 辛酸亚锡的加入降低了反应体系表观张力和黏度,有利于低聚物结构中酰氧键断裂生成丙交酯。     

Improving Quantum Metrology via Purifying and Distilling Noisy Probe States

In quantum metrology, the precision of unknown parameter estimation is studied in the quantum regime, and the choice of the probe state plays an important role in determining the precision of the parameter to be estimated. The quality of quantum metrology will be reduced in the presence of quantum noise during the memory time of probe states after preparation. Meanwhile the noisy probe state can be manipulated by different protocols such as single‐qubit purification, entanglement purification, and entanglement distillation etc. In this paper, the effects of these manipulations on the usefulness, that is, quantum Fisher information (QFI), of the noisy probe state in quantum metrology are studied. The results show that joint operations in single‐qubit purification and entanglement purification processes play positive roles in enhancing the QFI of the probe states, and local measurements in entanglement purification and entanglement distillation processes play both positive and negative roles in enhancing the QFI of the probe states. In this sense, single‐qubit purification will always be helpful in parameter estimation by using single qubits as probe, and entanglement purification process maybe more suitable for improving the estimation precision when entangled‐state probe is adopted.     

First-principles investigations of the Ni3Sn alloy at steam reforming conditions

The structure and surface composition of a Ni₃Sn alloy at conditions relevant for the steam reforming reaction was investigated using density functional theory calculations. Both the flat Ni₃Sn(0 0 0 1) surface and a surface with steps in the closed packed direction [1 0  0]were considered. The adsorption geometries and energies of the species CO, C, OH and H were calculated. Chemical potentials were used to map out which adsorbates are on the surface under varying conditions. It was found that adsorbates preferably bind to Ni as nearest neighbor with Sn as second-nearest neighbor. The binding energy is slightly stronger than on pure Ni. Adsorbate binding to Sn was found to be very unfavorable. Binding free energies indicate that at high temperature the alloy surface will be predominantly covered by CO and C, and at low temperatures one may find H and almost no OH. Even though the nominal composition of the investigated alloy is Ni₃Sn, the surface composition may differ significantly depending on temperature and pressure of the gas phase. This effect was investigated by calculating segregation energies both in the absence and in the presence of adsorbates. For the flat surface, it was found that only the bulk termination is present under relevant conditions. In contrast, it was found that for steps preferential adsorption of CO and C on Ni sites may lead to adsorption-induced segregation at temperatures below 400 °C. When taking segregation into account, the most stable Ni₃Sn surfaces will not bind CO or C at the same condition that Ni does. This is in excellent agreement with the previously proven ability of Ni-Sn alloys to inhibit graphite formation.     

Calcium sulphate scaling in membrane distillation process

Formation of precipitates containing CaSO₄ during membrane distillation, applied to the concentration of aqueous salt solutions, is discussed in this paper. It was found that the concentration of SO₄²⁻ ions in such solutions should not exceed 600 mg L⁻¹ when they are subjected to concentration. However, concentration of sulphates at the level of 800 mg L⁻¹ in the feed is permissible provided that the excess of CaSO₄ is removed in a crystallizer. Crystallisation of salts, mainly CaSO₄ · 2H₂O, on the surface and inside the membrane was observed at higher feed concentrations, causing damage of the module. Precipitation of calcium sulphate was also observed during the production of demineralised water when high values of the water recovery coefficient (above 90 %) were used. In this case, the formed precipitate also contained CaCO₃, the co-precipitation of which significantly changed the properties of the scaling layer. The precipitate containing both CaSO₄ and CaCO₃ was formed mainly on the membrane surface and it could easily be removed by rinsing the module with a HCl solution. Presented at the 35th International Conference of the Slovak Society of Chemical Engineering, Tatransé Matliare, 26–30 May 2008.