Separation of aqueous salt solution by pervaporation through hybrid organic–inorganic membrane: Effect of operating conditions

Hybrid polymer-inorganic membranes were prepared by crosslinking poly(vinyl alcohol) (PVA), maleic acid (MA) and silica via an aqueous sol–gel route. Membrane characterisation results revealed silica nanoparticles (< 10 nm) were well dispersed in the polymer matrix and significantly reduced swelling of the membrane. The membranes were tested for pervaporation separation of aqueous salt solution with NaCl concentrations of 0.2–5.0 wt% at temperatures 20–65 °C, feed flowrates 30–150 mL/min and permeate pressures 2–40 Torr. The salt rejection remained high (up to 99.9%) under all operating conditions. A high water flux of 11.7 kg/m² h could be achieved at a feed temperature of 65 °C and a vacuum of 6 Torr. The effect of operating conditions on water flux is discussed in relation to diffusion coefficients of water and fundamental transport mechanism through the membrane. The activation energy for water permeation was found to vary from 23.8 to 20.1 kJ/kmol when the salt concentration in the feed was increased from 0.2 to 5.0 wt%.     

Osmotic concentration of salt solutions in a countercurrent multiplier system

Analysing the principles of performance of the human kidney, in about 1940, Kuhn and co-workers established the theoretical and physical model of concentrating solutions without the use of substantial differences of pressure (the so-called loop of Henle). p]Continuing this idea, a system of double channel asymmetrical capillaries made of cellulose 2$\text{1}\text{2}$ acetate was constructed and sodium and potassium chloride solutions were concentrated. The degree of concentration increased for higher feed concentrations. In experiments with one metre loop longitudinal apparatus 20 gl^-1 NaCl feed solution, the final concentration was 25 gl^-1 NaCl. To obtain 1 m³day concentrated solution with 10% recovery, about 1m² of membrane area was required.     

Isoelectric precipitation of sunflower protein in a tubular precipitator

Isoelectric precipitation of sunflower protein was carried out in a 10-m long, 6-mm internal diameter glass tubular precipitator. The effects of feed flow rate, protein concentration in the feed stream, and volumetric feed ratio of precipitant (HCl aqueous solution) to protein solution on solid protein recovery and particle size distribution were studied. The dispersion range of the tubular precipitator was modelled to predict the experimental results. Calculated initial growth rates of protein particles were found to: increase with increases in feed flow rate and protein concentration in the feed stream, and decrease with increases in volumetric feed ratio.     

Absorption of carbon dioxide into aqueous solution of 2-amino-2-methy-1-propanol and 1, 8-diamino-p-menthane

Carbon dioxide was absorbed into an aqueous solution containing two reactants of 2-amino-2-methyl-1-propanol (AMP) and 1,8-diamino-p-menthane (DAM) in a stirred semi-batch tank with a planar gas-liquid interface within a range of 0?C3.0 kmol/m³ of AMP, 0?C0.2 kmol/m³ of DAM, and 298.15?C323.15 K at 15% of CO₂ and 101.3 kPa. Diffusivity, Henry constant and mass transfer coefficient of CO₂ in the mixed solution of AMP and DAM were used to calculate the theoretical enhancement factor of CO₂, which was obtained by an approximated solution of mass balances with the instantaneous and fast regime in CO₂-AMP-DAM system. The method of the classification of the chemical regime in the heterogeneous system was used to determine the enhancement factor by adding DAM under the limited concentration of AMP.     

Comparison of Different HFSLM Configurations for Separation of Neodymium and Uranium

Different feed and strip operating modes have been compared for the transport of neodymium (Nd³⁺) and uranyl (UO₂²⁺) ions in nitric acid media. The flux values of UO₂²⁺ for feed in recycling and once through mode with fresh strip were 2.26 × 10^?9 kmol/m²-s and 2.33 × 10^?9 kmol/m²-s, respectively. So, this resulted in low separation factors. The flux values of Nd³⁺ for feed and strip—both in recycling and in once through mode—were 2.21 × 10^?9 kmol/m²-s and 2.14 × 10^?9 kmol/m²-s, respectively. The operating modes—feed and strip both recycling and feed and strip both in once through—were found to be the best configurations.     

三乙酸纤维素正渗透膜的制备与性能

以三乙酸纤维素（CTA）为膜材料,1,4-二氧六环、丙酮为溶剂,甲醇、乳酸为添加剂,采用相转换法制备了三乙酸纤维素正渗透膜。研究了不同1,4-二氧六环/丙酮配比、添加剂乳酸含量、挥发时间、膜厚度、热处理温度条件下正渗透膜性能的变化规律。研究表明,当采用纯水为原料液,0.56mol/L CaCl2为汲取液时,优化制备的CTA正渗透膜的水通量达到14.10L/(m2?h),溶质反扩散量为0.031mol/(m2?h);采用0.1mol/L NaCl为原料液,4mol/L葡萄糖为汲取液时,优化制备的CTA正渗透膜的水通量保持在5L/(m2?h)以上,对NaCl的截留率大于99%。CTA正渗透膜相比于HTI膜,具有较高的亲水性、水通量、截留率,稳定性更好。     

Investigation of the effect of tetrahydrofuran and acetone as cosolvents in acrylonitrile–butadiene–styrene–based nanofiltration membranes

In this study, novel nanofiltration membranes were prepared with acrylonitrile–butadiene–styrene (ABS)–poly(ethylene glycol)–N,N ‐dimethylacetamide–[tetrahydrofuran (THF)–acetone] as a cosolvent. All of the membranes were prepared by the phase‐inversion method and a casting solution technique. The effects of the cosolvent concentration in the casting solution and the evaporation time before the immersion/precipitation step on the membrane performance and properties were investigated. The prepared membranes were characterized through their permeation flux, salt rejection, and phase‐inversion time values. The salt rejection was increased from 53% for the bare ABS membrane to 73% for the membrane prepared with 40 wt % THF as a cosolvent. The water flux was decreased from 4345 to 1121 cc m^?2 h^?1 with the addition of THF to the casting solution. The addition of acetone to the casting solution improved the water flux from 4345 to 5607 cc m^?2 h^?1 and reduced the salt rejection from 53 to 36%. The evaporation time of THF and acetone led to similar effects on flux and rejection. However, with evaporation time, membranes prepared with acetone were denser than those prepared with THF; this was due to the lower boiling point and higher boiling rate of acetone at the same temperatures. This resulted in greater effects on the ABS performance and structure. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44993.     

The kinetics of dissolved oxygen reaction in aqueous sodium dithionite solutions

The kinetics of the reaction between dissolved oxygen and sodium dithionite in alkaline aqueous solution was investigated in a stirred cell. For dithionite concentrations below 0.08 kmol/m³ and sodium hydroxide concentrations from 0.044 to 0.27 kmol/m³, the results show the reaction to be first order in dithionite and zero order in oxygen. The Arrhenius activation energy was determined to be 76.2 MJ/kmol in the temperature range 15 to 34°C. Addition of other electrolytes (sodium sulphate or potassium chloride) had no effect on the kinetics.     

Preparation of mesh-reinforced cellulose acetate forward osmosis membrane with very low surface roughness

Mesh-reinforced cellulose acetate (CA)-based membranes were prepared for forward osmosis (FO) by immersion precipitation. Casting compositions such as CA percent and 1, 4-dioxane/acetone ratio and also preparation conditions such as evaporation time, coagulation bath and annealing temperatures were tested for membranes’ performance. The results were compared with commercially CTA membranes. The best membrane (17.9% polymer and 1, 4-dioxane/acetone ratio of 1.89) showed water flux of 9.3 L/m²h (LMH) and RSF of 0.536 mol NaCl/m²h. Moreover, the membrane structure was reinforced by a polyester mesh, which created micro pores in the back of the membrane. This caused higher water flux and RSF compared to membranes without mesh. FO membrane prepared under best conditions, had a smoother surface than commercial ones. This feature enhances the fouling properties of the membrane, which can be appropriate for wastewater treatment applications.     

Selective transport of cobalt (II) from ammoniacal solutions containing cobalt (II) and nickel (II) by emulsion liquid membranes using 8-hydroxyquinoline

The selective transport of cobalt (II) from ammoniacal solutions containing nickel (II) and cobalt (II) by emulsion liquid membranes (ELMs) using 8-hydroxyquinoline (8-HQ) as extractant has been presented. Membrane solution consists of a diluent (kerosene), a surfactant (ECA 4360J), and an extractant (8-HQ). Very dilute sulphuric solution buffered at pH 5.0 has been used as a stripping solution. The ammoniacal feed solution pH was adjusted to 9.0 with hydrochloric acid. The important variables governing the permeation of cobalt (II) have been studied. These variables are membrane composition, pH of the feed solution, cobalt (II) and nickel (II) concentrations of the feed solution, stirring speed, surfactant concentration, extractant concentration, complexing agent concentration and pH of the stripping solution, and phase ratio. After the optimum conditions had been determined, it was possible to selectively transport 95.0% of cobalt (II) from ammoniacal feed solution containing Co²⁺ and Ni²⁺ ions. The separation factors of cobalt (II) with respect to nickel (II), based on initial feed concentration, have experimentally found to be of as high as 31 for equimolar Co(II)–Ni(II) feed solution.     

泡沫分离法回收酶法生产生物柴油中的液体脂肪酶

采用泡沫分离法对酶法生产生物柴油过程中的水相脂肪酶进行回收并富集. 通过正交实验考察了液体脂肪酶溶液中pH值、通气速度、初始酶浓度对富集比、酶蛋白回收率和酶活回收率的影响. 结果表明,气速10 L/(L×h)、进料酶浓度0.2 g/L及pH 7.0时蛋白回收率和酶活回收率接近100%,相应的富集比为3.67;初始酶浓度对富集比和蛋白回收率有显著影响,回收过程中脂肪酶活性无损失. 甲醇的存在能显著提高回收速率,甘油的存在降低了富集比,而生物柴油的存在影响了泡沫的稳定性,要形成稳定的泡沫,生物柴油含量需小于0.01%.     

Novel alkyl methylnaphthalene sulfonate surfactants: A good candidate for enhanced oil recovery

The surface tensions of various surfactant aqueous solution and the dynamic interfacial tensions between the Shengli oil field of China crude oil and the solution of novel surfactants, a series of single-component alkylmethylnaphthalene sulfonates (AMNS) including various the length of alkyl chains (hexyl, octyl, decyl, dodecyl and tetradecyl, developed in our laboratory), were measured. It is found that synthesized surfactants exhibited great capability and efficiency of lowering the solution surface tension. The critical micelle concentrations, CMC were: 6.1–0.018×10⁻³ mol L⁻¹, and the surface tensions at CMC, γ_CMC were: 28.27–35.06 mN m⁻¹. It is also found that the added surfactants are greatly effective in reducing the interfacial tensions and can reduce the tensions of oil–water interface to ultra-low, even 10⁻⁶ mN m⁻¹ at very low surfactant concentration without alkali. The addition of salt, sodium chloride, results in more effectiveness of surfactant in reducing interfacial tension and shows that there exist obviously both synergism and antagonism between the surfactant and inorganic salt. All of the synthesized surfactants, except for hexyl methylnaphthalene sulfonate, can reduce the interfacial tension to ultra-low at an optimum surfactant concentration and salinity. Especially Tetradec-MNS surfactant is most efficient on lowering interfacial tension between oil and water without alkaline and the other additives at a 0.002 mass% of very low surfactant concentration. Both chromatogram separation of flooding and breakage of stratum are avoided effectively, in addition to the less expensive cost for enhanced oil recovery, and therefore it is a good candidate for enhanced oil recovery.     

Relationship between foaming properties and solution properties of protein/nonionic surfactant mixtures

The foaming properties of bovine serum albumin (BSA), in the absence and presence of Triton X-100 (TX-100), have been investigated using shaking tests. The results showed that increases in the TX-100 bulk concentration rapidly reduced both foam height and foam stability at TX-100 concentrations below about 0.25 mM, but increased foam height and foam stability at TX-100 concentration above 0.3 mM. The interaction between BSA and TX-100 has been studied using fluorescence spectroscopy. The surfactant appeared to bind to BSA with a low molar ratio (about one surfactant molecule per protein molecule) at concentrations below the critical micelle concentration (CMC); the binding became weaker at concentrations above the CMC. It was confirmed that protein-protein or protein-surfactant interactions had significant influence upon foaming properties of mixed protein/surfactant system.     

A Study on CO2 Absorption Kinetics by Aqueous Solutions of N,N‐Diethylethanolamine and N‐Ethylethanolamine

N‐Ethylethanolamine (EEA) and N,N‐diethylethanolamine (DEEA) represent promising candidate alkanolamines for CO₂ removal from gaseous streams, as they can be prepared from renewable resources. In this work, the reaction rate constant for the reaction between CO₂ and EEA was determined from the absorption rate measurements of CO₂ in a blend comprising DEEA, EEA and H₂O. A stirred‐cell reactor with a plane, horizontal gas‐liquid interface was used for the absorption studies. While the DEEA concentration in the formulated solution was varied in the range of 1.5–2.5 kmol/m³, the initial EEA concentration was 0.1 kmol/m³. A zwitterion mechanism for EEA and a base‐catalyzed hydration mechanism for DEEA were used to describe the reaction kinetics. At 303 K, the second‐order reaction rate constant for the CO₂ reaction with EEA was found to be 8041 m³/(kmol s). The liquid‐side mass transfer coefficient was also estimated, and its value (0.004 cm/s) is in line with those typical of stirred‐cell reactors.     

一种含氟烷基磷酸酯类氟碳表面活性剂的复配研究

研究了含氟烷基磷酸单酯类表面活性剂[分子式为H(CF2)6CH2OPO(ONa)2,记为DFH-PS]与无机盐和普通碳氢表面活性剂的复配性能,研究结果表明,DFH-PS水溶液最低表面张力为23.73 mN/m;当NaCl浓度为0.2 mol/L时,可使DFH-PS水溶液最低表面张力下降到21.62 mN/m;阴离子碳氢表面活性剂十二烷基硫酸钠(SDS)对该含氟表面活性剂影响显著,当n(DFH-PS)∶n(SDS)=5∶1时,可使水溶液表面张力在很低浓度时降至22.22 mN/m;与非离子表面活性剂辛基酚聚氧乙烯(10)醚(OP-10)混合,当n(DFH-PS)∶n(OP-10)=8∶1时,可使水溶液表面张力降至27.0 mN/m。     

Concentration of gelatin solution with polyethersulfone ultrafiltration membranes

In this work, polyethersulfone (PES) flat sheet ultrafiltration (UF) membranes were prepared by immersion precipitation phase inversion process with polyvinylpyrrolidone (PVP 30K) and acetone as additives. The best preparation condition for PES membranes with high water flux and rejection (to BSA) was decided. It was found that the optimal composition of the polymer casting solution was: 16 wt% (PES), 2 wt% (PVP 30K), and 1 wt% (acetone). Pure water flux of the membrane prepared at this condition reached to 373 L/m² h at 0.1 MPa, and the rejection to BSA was 91%. Compared with other reports, the rejection was slightly low but the flux of the PES membrane was high. When the membrane was used to concentrate gelatin solutions, the rejection value was over 75%. It was found that increasing the feed temperature and transmembrane pressure enhanced the permeation flux, but the rejection decreased slightly. However, increasing the cross-flow velocity of the feed solution simultaneously increased both the permeation flux and the rejection.     

Salt-Induced Constructions of Gemini-like Surfactants at the Interface and Their Effects on the Interfacial Tension of a Water/Model Oil System

It is an urgent issue to enhance oil recovery for unconventional reservoirs with high salinity. Focused on this topic, salt addition is a powerful tool to motivate the surfactant assembly at the water/oil interface and improve the interfacial activity. We used a cationic surfactant cetyltrimethylammonium bromide (CTAB) and an anionic salt dicarboxylic acid sodium (CnDNa) to construct gemini-like surfactants at the interface and evaluated their ability to reduce the interfacial tension (IFT) between model oil (toluene and n-decane, v:v = 1:1) and water. Interestingly, the fabrication of a (CTAB)₂/C4DNa gemini-like surfactant was hardly achieved at the fresh water/model oil interface, but accomplished at the brine/model oil interface. At a high NaCl concentration (100,000 mg L⁻¹), the IFT value is reduced to 10⁻³ mN m⁻¹ order of magnitude, which is generally desired in practical applications. The control experiments displacing the surfactant type and the spacer length further confirmed the NaCl effects on the interfacial assembly.     

Characteristics and potential applications of a novel forward osmosis hollow fiber membrane

There has been a resurgence of interest in forward osmosis (FO) as a potential means of desalination, dewatering and in pressure retarded osmosis, which Sidney Loeb was advocating over 3 decades ago. This paper describes the characteristics and potential applications of a newly developed FO hollow fiber membrane, which was fabricated by interfacial polymerization on the inner surface of a polyethersulfone (PES) hollow fiber. This FO membrane presents excellent intrinsic separation properties, with a water flux of 42.6 L/m² h using 0.5 M NaCl as the draw solution and DI water as the feed with the active layer facing the draw solution orientation at 23 °C. The corresponding ratio of salt flux to water flux was only 0.094 g/L, which is superior to all other FO membranes reported in the open literature. To evaluate different application scenarios, various NaCl solutions (500 ppm (8.6 mM), 1 wt.% (0.17 M) and 3.5 wt.% (0.59 M)) were used as the feed water to test the performance of the FO membrane. The membrane can achieve a water flux of 12.4 L/m² h with 3.5 wt.% NaCl solution as the feed and 2 M NaCl as the draw solution, suggesting it has good potential for seawater desalination.     

CO2‐Switchable Oil/Water Emulsion for Pipeline Transport of Heavy Oil

By mixing an aqueous solution of tertiary amine, N,N‐dimethylethanolamine (DMEA), with naphthenic acid (RCOOH) derived from heavy oil, a CO₂ switchable zwitterionic surfactant (RCOO^?DMEAH⁺) aqueous system was constructed. The CO₂ switchability of this zwitterionic surfactant was confirmed by visual inspection, pH measurements, and conductivity tests, i.e., the RCOO^?DMEAH⁺ decomposed into RCOOH, DMEAH⁺ and HCO₃^? after bubbling CO₂ through but switched back to its original state by subsequent bubbling N₂ through at 80 °C to remove the CO₂. The interfacial tension tests of heavy oil in DMEA aqueous solutions indicated that the solution containing 0.5 wt% of DMEA and 0.2 wt% of NaCl resulted in the lowest interfacial tension. The O/W emulsion formed when aqueous solutions of DMEA were used to emulsify heavy oil exhibited the best performance when the oil/water volume ratio, DMEA concentration, and NaCl concentration were 65:35, 0.5 and 0.2 wt%, respectively. The feasibility of pipeline transport of the O/W heavy oil emulsion was evaluated. The results illustrated that the demulsification of the O/W emulsion after transport could be easily realized by bubbling CO₂ through. Although demulsification efficiency still needs to be improved, the recycling of the aqueous phase after demulsification by removal of CO₂ looks promising.     

Membrane separation process modeling for CO2 partial removal in prepurification of air separation units

A novel membrane/adsorption hybrid system was proposed for air prepurification in large scale air separation units. Mathematical models were established for cocurrent and countercurrent flow patterns with crude nitrogen as purge stream to describe the membrane separation performance. The experimental and predicted results are in good agreement confirming the validity of the mathematical models. Effects of membrane properties and operation parameters on O₂ recovery, N₂ recovery, and membrane area requirement were investigated. For countercurrent flow pattern, O₂ recovery and N₂ recovery were larger than 98 and 99%, respectively, and membrane area requirement was less than 0.25?m²/m³?h^?1 with feed side pressure of 0.6?MPa and the purge gas/feed gas ratio of 0.2.