Polyethersulfone/poly (butylene succinate) membrane: Effect of preparation conditions on properties and performance

In this study, biodegradable polymer of poly (butylene succinate) (PBS) was blended with polyethersulfone (PES) to prepare a novel semi-biodegradable membrane. The effect of blend ratio and coagulation bath temperature (CBT) was investigated on membrane characteristics including membrane morphology, mechanical strength and also treatment ability. Moreover, Fourier transform infrared (FTIR) spectrum, thermal stability, biodegradation and contact angle of the membranes were studied. Results demonstrated that the wastewater permeation through the prepared membranes was increased by blending the polymers and reached to maximum at blend ratio of 50/50. The wastewater treatment of PES/PBS blend membranes was improved by increasing PBS content.     

Hydrogen separation from the H2/N2 mixture by using a single and multi-stage inorganic membrane

The separation characteristics of hydrogen from a gas mixture were investigated by using a single and two-stage inorganic membrane. Three palladium impregnated membranes were prepared by using the sol-gel, hydrolysis, and soaking-and-vapor deposition (SVD) techniques. A two-stage gas separation system without a recycling stream was constructed to see how much the hydrogen separation factor would be increased. Numerical simulation for the separation system was conducted to predict the separation behavior for the multi-stage separation system and to determine the optimal operating conditions at which the highest separation factor is obtained. Gas separation through each prepared membrane was achieved mainly by Knudsen diffusion. The real separation factor for the H₂/ N₂ mixture was increased with the pressure difference and temperature for a single stage, respectively. For the twostage separation system, there was a maximum point at which the highest separation factor was obtained and the real hydrogen separation factor for H₂/N₂ mixture was increased about 40 % compared with a single stage separation. The numerical simulation for the single and two-stage separation system was in a good agreement with the experimental results. By numerical simulation for the three-stage separation system, which has a recycle stream and three membranes that have the same permeability and hydrogen selectivity near to the Knudsen value, it is clear that the hydrogen separation factors for H₂/N₂ mixture are increased from 1.8 to 3.65 and hydrogen can be concentrated up to about 80 %. The separation factors increased with increasing recycle ratio. Optimal operating conditions exist at which the maximum real separation factor for the gas mixture can be obtained for three-stage gas separation and they can be predicted successfully by numerical simulation.     

Water recovery from humidified waste gas streams: Quality control using membrane condenser technology

In this work “membrane condenser” is utilized for the selective recovery of evaporated waste water from industrial gases and for the control of the composition of the recovered liquid water. A simulation study of the process has been developed for predicting the membrane-based process performance. The achieved results indicate that feed flow rate (Q^Feed), interfacial membrane area (A^Membrane), the ratio Q^Feed/A^Membrane, the temperature difference (ΔT) between the fed flue gas T_feed and the membrane module are the parameters controlling the process. In particular, the amount of recovered water rises at increasing ΔT and Q^Feed/A^Membrane, whereas its quality is made worse at increasing ΔT and Q^Feed. The data obtained have been also supported by an experimental study of the process, confirming the validity of the simulation study and its suitability for a screening of the operative conditions to be chosen in a membrane condenser.     

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.     

旋叶动态膜滤技术在酶制剂生产中菌-酶分离过程的应用研究

通过旋叶式动态膜滤机装置的实验,利用核孔膜α 淀粉酶发酵液和２７０９碱性蛋白酶发酵液进行了菌 酶分离。实验结果表明,动态膜滤技术在酶制剂生产中直接用于酶发酵液除菌是可行的     

Glycerol removal from biodiesel using membrane separation technology

Membrane separation technology was used to remove free glycerol from biodiesel in order to meet the ASTM D6751 and EN 14214 standards. Fatty acid methyl esters (FAME) produced from canola oil and methanol were purified using ultra-filtration. The effect of different materials present in the transesterification reaction, such as water, soap, and methanol, on the final free glycerol separation was studied. A modified polyacrylonitrile (PAN) membrane, with 100 kD molecular weight cut-off was used in all runs. Tests were performed at 25 °C and 552 kPa operating pressure. The free glycerol content in the feed, retentate and permeate of the membrane system was analyzed using gas chromatography according to ASTM D6584. Results showed low concentrations of water had a considerable effect in removing glycerol from the FAME even at approx. 0.08 mass%. This is four orders of magnitude less than the amount of water required in a conventional biodiesel purification process using water washing. It is suggested that the mechanism of separation of free glycerol from FAME was due to the removal of an ultrafine dispersed glycerol-rich phase present in the untreated FAME. This was confirmed by the presence of particulates in the untreated FAME. The size of the particles and the free glycerol separation both increased with increasing water content of the FAME. The trends of separation and particle size vs. water content in the FAME phase were very similar and exhibited a sudden increase at 0.08 mass% water in the untreated FAME. This supports the conclusion that water increased the size of the distributed glycerol phase in the untreated FAME leading to its separation by the ultra-filtration membrane. The technology for the removal of free glycerol from biodiesel was found to use 2.0 g of water per L of treated FAME (0.225 mass% water) vs. the current 10 L of water per L of treated FAME.     

膜蒸馏和膜吸收技术现状及发展

膜蒸馏和膜吸收是一种以蒸汽压差为推动力的新型高效的膜分离技术,作者介绍了膜蒸馏和膜吸收技术发展现状,机理及优缺点,并对其在有机废水处理中的应用及今后发展方向进行了论述。     

Cadmium removal using hollow fiber membrane with organic extradant

Removal of cadmium ion by using a hollow fiber module is investigated experimentally, and organic extradant is applied to enhance the removal rate. The roles of pH, flow rates of the aqueous phase and the organic phase, initial concentration of cadmium ion and coexisting metals are investigated to find an optimum operating condition of the module. The experimental outcome indicates that the best performance is yielded with pH of 4 and the flow rate of aqueous phase in tube side flow controls mass transfer rate. In addition, the initial concentration of 100 ppm gives the best removal. Effect of coexisting component is negligible except Zn and Cu when both of them are present at the same time.     

Electrochemical studies of osmium-(pyrrole-methyl) pyridine-co-polymers deposited using the membrane template method

The electrochemical characterisation of films formed by co-polymerisation of [Os(2,2′-bipyridine)₂XCl] (Os-PMP) where X is 3-(pyrrole-1yl-methyl)pyridine with 3-methyl thiophene or 1,2-diaminobenzene was carried out. The use of the membrane template method, which allowed growth of tubules of redox co-polymer was employed in the case of 1,2-diaminobenzene. Cyclic voltammetry allowed formation of the most stable 3-methylthiophene/Os-PMP films while chronocoulometry was used to co-polymerise Os-PMP with 1,2-diaminobenzene, resulting in stable films of co-polymer micro-tubules with thin-film behaviour up to 0.5 V s⁻¹ (r² = 0.9997). Surface analysis was carried out using SEM.     

Decompostion of pharmaceuticals (sulfamethazine and sulfathiazole) using oxygen-based membrane biofilm reactor

The subject of this research was the decomposition of pharmaceuticals (sulfamethazine and sulfathiazole) using an oxygen-based membrane biofilm reactor. The influent concentrations in pharmaceuticals feed-medium were (in ppb): sulfamethazine (40) and sulfathiazole (85). The oxygen-based membrane biofilm reactor system consisted of two membrane modules connected to a recirculation loop. The main membrane module contained a bundle of 32 hydrophobic hollow-fiber membranes inside a polyvinyl-chloride pipe shell, and the other module contained a single fiber used to take biofilm samples. Pure O₂ was supplied to the inside of the hollow fibers through the manifold at the base, and the O₂ pressure for both reactors was 13 kPa. (1 kPa = 0.0099 atm = 0.145 psi). HRT was 3 h. The decomposition ratio of pharmaceuticals (sulfamethazine and sulfathiazole) using oxygen-based membrane biofilm reactor was (%): sulfamethazine (77 ± 2), and sulfathiazole (87 ± 2).     

Chromium(VI) removal in a semi-continuous process of hollow fiber membrane with organic extractants

Chromium(VI) extraction from aqueous metal solution was experimentally studied by using a hollow fiber supported liquid membrane module. Organic extractants of D2EHPA, TBP, Lix79 and TOA were used to investigate the extraction performance. The extraction efficiencies of single and multiple component systems were examined with single or multiple extractants, and the role of multiple extraction operations and the difference between batch and continuous processes were inspected to find the optimum extraction condition. The experimental outcome indicates that the extraction process is controlled by aqueous phase mass transfer and multiple extraction operations do not reduce the extraction efficiency. The coexisting elements give no significant effect on chromium removal, while the mixed extractants of D2EHPA and TBP enhance the extraction efficiency by 84%. The efficiencies of batch and continuous extraction processes are nearly identical. This paper was presented at the 2004 Korea/Japan/Taiwan Chemical Engineering Conference held at Busan, Korea between November 3 and 4, 2004.     

膜分离技术用于气体脱湿的研究现状

随着膜科学的发展,气体膜分离技术由于具有选择性高、能耗低、费用低、耐用性等优点,优于吸附等传统分离方法,广泛应用于石油、化工、电力、能源和环保等行业,该方法在气体除湿领域表现尤为突出,受到广泛关注。作者详细论述了气体膜分离技术的研究和发展现状,并介绍了分子模拟方法应用于该领域的研究。最后指出,随着膜材料及其制备工艺的发展和新型研究技术的应用与开发等,膜法脱湿将得到更大的发展。     

Membrane‐Based Conditioning of an Innovative Oil‐Based Preservative for Food Technology

Demulsification of emulsions is of great interest for industrial applications. For developing a new, alternative preservation process, investigations are conducted for separating a mixture of water and an oil‐based preservative by membrane technology. Using a water‐in‐oil emulsion, the conventional membrane separation with hydrophobic membranes does not show a reasonable result. It was found that the oil‐based preservative leads to a hydrophilization of the membrane by its amphipathic character. Subsequently, a possible separation with a hydrophilic membrane system as a coalescing system was investigated. Different parametric studies were performed. The efficiency of the coalescence depends on the membrane material, the pore size, the transmembrane pressure, and the temperature during membrane passage as well. Best results so far have been achieved by using a polyethersulfone membrane with a pore size of 0.6 μm.     

Effect of ethylene vinyl acetate content on the performance of VMD using HDPE co-blending membrane

Membranes were fabricated with high-density polyethylene(HDPE) and ethylene vinyl acetate(EVA) blend through thermally induced phase separation and were then used for vacuum membrane distillation(VMD).The membranes were supported by nonwoven polyester fabric with a special cellular structure. Different membrane samples were obtained by adjusting the polymer concentration, HDPE/EVA weight ratio, and coagulation bath temperature. The membranes were characterized by scanning electron microscopy(SEM) analysis, contact angle test, and evaluation of porosity and pore size distribution. A series of VMD tests were conducted using aqueous NaCl solution(0.5 mol·L~(-1)) at a feed temperature of 65 ℃ and permeate side absolute pressure of 3 kPa. The membranes showed excellent performance in water permeation flux, salt rejection, and long-term stability. The HDPE/EVA co-blending membranes exhibited the largest permeation flux of 23.87 kg·m~(-2)·h~(-1) and benign salt rejection of ≥99.9%.     

膜生物反应器(MBR)技术及其工程应用探讨

膜生物反应器(MBR)废水处理技术开发始于20世纪90年代,近年来MBR技术的应用在世界上维持着每年高于10%的增长率。随着对水资源利用水平要求的不断提高,我国已经成为世界上MBR工程应用增长最快的国家。特别是2005年以来,处理能力5 000m3/d以上的新建大中型MBR项目均保持大于100%的年增长率。作者介绍了膜生物反应器(MBR)污水处理技术工程应用的主要类型及特点,总结了膜污染的机理、主要影响因素及当前工程上对膜污染的主要控制手段,给出了当前几种典型的生活污水及工业废水MBR工艺的工程应用的技术经济情况,显示出MBR工艺的应用前景。     

膜生物处理技术的机理及应用研究

膜生物处理技术是一种控制水环境恶化和缓解水资源短缺的新型水处理工艺.详细介绍了膜生物技术的工艺特性(对污染物的去除效果、运行参数、微生物特性)及机理(污染物去除机理、膜污染机理).为进一步改进工艺、促进其推广应用提供了理论依据.     

Separation of phenylalanine by ultrafiltration using D-Phe imprinted polyacrylonitrile-poly(acrylic acid)-poly(acryl amide) terpolymer membrane

A D-phenylalanine (D-Phe) imprinted terpolymer P(AN-AA-AAm) membrane was prepared by the wet phase inversion method. Acrylamide (AAm) and acrylic acid (AA) were used as the functional monomer and acrylonitrile (AN) was used as a physical cross linker. The template molecules were removed from the terpolymer matrix by washing with a 5 percent acetic acid solution. The removal of template molecules from the membrane matrix increased the population of free COOH groups and reduced that of dimerized COOH groups in the membrane matrix, which is an indirect evidence of the formation of recognition sites. The adsorption selectivity of the D-Phe imprinted terpolymer membrane prepared by in-situ implanting method was 0.37 at pH 2 after 3 h batch adsorption using 100 mg Phe/l racemate solution and reached nearly 1 after 24 h. In the ultrafiltration process, the permselectivity was 0.38 at pH 2 after 2.5 min. Separation of D-Phe from the racemate solution was demonstrated by a repeated ultrafiltration batch work.     

Mass transfer modeling of membrane carrier system for extraction of Ce(IV) from sulfate media using hollow fiber supported liquid membrane

A theoretical and experimental study on the extraction and stripping of Ce(IV) ions from sulfate media using microporous hydrophobic hollow fiber supported liquid membrane has been performed. The experiments were made in the recycling mode. Tri-n-octylamine (TOA) was used as extractant diluted in kerosene and sodium hydroxide was use as strip solution. The mathematical model focused on the extraction side of a liquid membrane system. The aqueous feed mass transfer coefficient (k_i) and the organic mass transfer coefficient (k_m) which were calculated from the model were 9.47 X 10^-2 and 6.303 cm/s, respectively. Therefore, the rate controlling step is the diffusion of the cerium complex across a liquid membrane. In addition, the mass transfer modeling was performed and the validity of the developed model was evaluated with experimental data and found to tie in well with the theoretical value when the concentration of TOA was higher than 5% (v/v).     

Color fading of reactive-dyed cotton using UV-assisted ozonation

Fashion trends have promoted the use of oxidants in the textile sector recently. Conventionally, oxidants require an aqueous bath, with ozone; the worn style or faded effect on textile products could be achieved more ecologically. UV-assisted ozonation has been studied or applied to certain areas but not fading reactive-dyed textiles. In this study, the UV-assisted ozonation on color-fading reactive-dyed cotton was investigated. The effect of UV on ozone fading effect and the comparison of UV-assisted ozonation with conventional color-fading processes (hydrogen peroxide and chlorine) were carried out in terms of fading efficiency, negative impacts on fabrics’ mechanical properties, namely, tensile strength and elongation, tearing strength and abrasion resistance, and surface microstructure. It is found that UV strengthens the fading effect (up to 2.7 times) of ozonation with slight loss of cottons’ mechanical properties. UV-assisted ozonation is not only more effective than conventional fading processes in the respect of fading efficiency but also less negatively influenced fabrics mechanical properties. Additionally, it comparatively requires far less the use of water and power, so we may conclude that it proposed an excellent potential to alternate the conventional processes.     

New configuration of a membrane bioreactor for effective control of membrane fouling and nutrients removal in wastewater treatment

Excess aeration to membrane surface is common for controlling membrane fouling in a submerged membrane bioreactor (MBR) system, but significant energy is consumed for excess air production. Therefore, an alternative strategy for membrane fouling control is currently needed. A new configuration of MBR was proposed in this study to control membrane fouling effectively. To reduce biosolids concentration near the membrane surface, the position of the membrane module in MBR was elevated from the bottom to the top in the reactor. This could divide the reactor to two different zones: upper and lower zone. Air was not supplied at the lower zone whereas aeration was given to the upper zone where the membrane filtration was carried out. Biosolids concentration was reduced in the upper zone because the mixed liquor was settled down to the lower zone. Membrane fouling could be lessened in the upper zone due to the reduced biosolids concentration. Therefore, to verify if this new configuration of MBR could mitigate membrane fouling, the effect of changing vertical position of the membrane module in MBR on membrane fouling was investigated. Prior to verification the effect of elevation of membrane module on membrane fouling, influence of MLSS concentration on membrane fouling was investigated first. Transmembrane pressure (TMP) increase became steep as MLSS concentration increased. And the immersed membrane module was elevated from the bottom to the top of the MBR. When the upper membrane was located in the bioreactor, less membrane fouling was observed. This could demonstrate a possibility of new MBR design to control membrane fouling. In addition, reduced dissolved oxygen level in the returned sludge to anoxic tank could increase denitrification efficiency if this configuration is directly applied to biological nutrient removal processes.