Effects of embedding functionalized multi-walled carbon nanotubes and alumina on the direct contact poly(vinylidene fluoride-co-hexafluoropropylene) membrane distillation performance

Flat-sheet membranes were fabricated by incorporating alumina (Al₂O₃) and functionalized multiwalled carbon nanotubes (MWCNTs; MWCNTs-COOH) in PVDF-co-HFP membrane via the phase-inversion method for application in membrane distillation (MD) application. Scanning electron microscopy and atomic force microscopy were performed on the resulting membranes to investigate the effects of functionalized MWCNTs. The results revealed that the embedding of functionalized MWCNTs led to a significant modification of the membrane characteristics, including the structural morphology, thickness, roughness, porosity, pore size, and pore size distribution. The effects of operational parameters such as the hot feed solution temperature (47–67?°C), feed flow rate (0.35–0.55?L/min), and feed concentration (0–100?g/L) on the performance of the fabricated membrane were tested using the DCMD system. The experimental results demonstrated that the permeate flux was enhanced by approximately 32.43% by using functionalized MWCNTs, reaching a value of 16.35?kg/m² h at 35?g/L feed concentration, 67?°C hot feed temperature, and 0.55?L/min feed flow rate, at the constant temperature of 20?°C and 0.35?L/min flow rate. The functionalized MWCNTs embedded within the membrane successfully modified the interactions between water and the membrane to improve the water vapor transport while inhibiting salt penetration into the pores.     

吸附法去除水中药品及个人护理品(PPCPs)研究进展

近几年,环境新兴污染物——药品及个人护理品(PPCPs)在全球范围内不断检出,由于其具有"伪持续性"、难生物降解性、生态毒性等特点,对环境中的生物以及人类健康存在很大威胁。介绍了PPCPs的主要危害和分布情况,重点阐述了有关碳材料、黏土矿物、生物材料、纳米材料等去除水中PPCPs的研究进展,分析了吸附机理,并对吸附法去除水中PPCPs的发展方向进行了展望。     

Water Quality Improvement by Combined UF,RO, and Ozone/Hydrogen Peroxide System (HiPOx) in the Water Reclamation Process

Conventional water reclamation processes, such as membrane bioreactors, are not always effective in removal of pharmaceuticals and personal care products (PPCPs), endocrine disrupting chemicals (EDCs) and/or N-nitrosodimethylamine (NDMA), even with the reverse osmosis (RO) membrane process. A study was conducted, at a NEWater factory in Singapore, to compare a conventional ultrafiltration (UF) membrane /RO treatment process with a treatment train having the HiPOx unit, an advanced oxidation process (AOP), which was installed between the UF and the RO unit operations. By incorporating the HiPOx into the UF/RO treatment process, following results were observed; 1) increased removal of PPCPs, EDCs and NDMA, 2) improvement in ultraviolet transmission (UVT) of the RO permeate, 3) enhanced removal of TOC and color, and increased UVT of the RO brine, 4) suppression of the increase in the RO transmembrane pressure by organic fouling.     

液隙式热泵膜蒸馏海水淡化系统的热力性能分析

热泵膜蒸馏是一种新型的膜分离技术，在处理高浓度盐水方面具有很大的优势，而目前的热泵膜蒸馏系统存在渗透量较低、冷却水消耗量大等问题。为提高渗透量、减少冷却水的消耗，设计了一种新型液隙式热泵膜蒸馏的海水淡化系统，通过在Aspen Plus中自定义膜模块建立经过实验验证的系统仿真模型，研究了进料液温度、渗透侧温度及进料流量对系统膜通量及能效比等热力参数的影响。结果表明，渗透侧温度降低可引起渗透量增加和能效比减小，且在低渗透侧温度情况下渗透侧温度的改变对能效比影响更大。随着渗透侧温度变化，存在一个渗透侧温度使造水比最大且吨水能耗最小，研究工况下最大造水比可达3.42，最小吨水能耗为463 MJ/t，且该最佳渗透侧温度随进料液温度增加而增加。进料液流量增加可引起渗透量和能效比增加，引起吨水能耗升高和造水比降低，当进料液流量小于3 L/min时，进料液流量增加对吨水能耗和造水比的负面影响较显著，进料液温度为50℃时，料液流量从1.5 L/min增至3 L/min，造水比的降低幅度可达33.5%；料液流量从4.5 L/min增至6 L/min时，造水比的降低幅度降至10.6%。     

疏水性单管陶瓷膜接触器在SO2吸收中的应用

对平均孔径200 nm的氧化锆陶瓷膜进行疏水改性与表征,并将其组装制成疏水性单管陶瓷膜接触器,采用清水作为低成本吸收液,开展了陶瓷膜接触器在废气脱硫方面应用的研究。比较了亲、疏水陶瓷膜接触器的传质性能,考察了进气流量、吸收液流量、进气浓度和吸收液温度等因素对SO₂脱除率和传质速率的影响,并对陶瓷膜接触器进行了长期稳定性测试。研究表明,疏水改性只改变陶瓷膜的表面性质（接触角达到132°）,对形貌结构影响较小;与未改性的陶瓷膜相比具有更高的脱硫效率和总传质系数。SO₂的脱除率和传质速率随吸收液流量的增加均增加;SO₂的脱除率随进气流量和进气浓度的增加而降低,但传质速率增加;吸收液温度的升高不利于SO₂的吸收;原料气中的CO₂对SO₂的脱除率影响较小。与传统的填料塔相比,陶瓷膜接触器具有更小的传质单元高度（HTU）值。陶瓷膜接触器脱硫效率高,可稳定操作,在废气脱硫方面具有良好的应用前景。     

Continuous and efficient removal of THMs from river water using MF membrane combined with high dose of PAC

A combination of microfiltration (MF) membrane with a high concentration (40 g/L of the reactor) of powdered activated carbon (PAC) efficiently and continuously removed trihalomethanes (THMs) and total organic carbon (TOC) from river water for a period of two months. Without PAC, the membrane reactor was able to remove less than 18% of THMs and less than 5% of TOC; with PAC, 65 to 95% of THMs and TOC were removed. Even though the THMs concentration in the influent was steadily increasing (reaching 50 μg/L), THMs concentration in the effluents from the reactors with PAC were consistently below 15 μg/L. While the MF membranes alone could not remove organics, PAC and microbial activity in the biofilm deposited on the PAC particles assured long term and continuous removal of THMs. No additional PAC was added into or removed from the reactors during the filtration period. Operational parameters such as the backwashing of the membrane, interval of the filtration cycle and biological pretreatment of the river water had a small effect on the extent of THMs removal, but they increased the filtration time prior to membrane cleaning and improved the overall performance of the reactors.     

Application of ultrafiltration membranes for removal of humic acid from drinking water

Humic acids are primarily a result of the microbiological degradation of surrounding vegetation and animal decay and enter surface waters through rain water run-off from the surrounding land. This often gives rise to large seasonal variations, high concentrations in the wet season and lower concentrations in the dry season. Alone humic acid is just a colour problem but when present in conventional treatment processes like chlorination, carcinogenic by-products like trihalomethane and haloacetic acid are formed. This, in addition to the demand for clean potable drinking water, has sparked extensive research into alternative processes for the production of drinking water from various natural/industrial sources. One of the major areas of focus in these studies is the use of membranes in microfiltration, ultrafiltration and nanofiltration. In this report the humic acid removal efficiency of ultrafiltration membranes with 3 kDa, 5 kDa and 10 kDa MWCO is examined. The membranes were made of regenerated cellulose and were in the form of cassette providing a 0.1 m² surface area. At first distilled and deionised water, known as milliQ water, was used as the background feed solution to which humic acid powder was added. It was found that all three membranes removed humic acid with an efficiency of approx. 90% and were capable of reducing initial concentrations of 15mg/L to below the New Zealand regulatory limit of 1.17 mg/L. The permeate flux at a transmembrane pressure of 2.1 bar was approx. 20 l/m²/h (LMH) and 40 LMH, respectively through the membranes with MWCO 3 kDa and 5 kDa. These membranes experienced significant surface fouling resulting in retentate flow rates as low as 11 litres per hour after just four runs compared to the recommended 60–90 l/h. Cleaning with 0.1 M NaOH slightly improved the retentate flow rate, but well below those obtained with fresh membranes. The 10 kDa membrane provided high retentate flow rates which evidently minimised fouling by providing a good sweeping action across the membrane surface while maintaining humic acid removal below the regulatory 1.17 mg/L level. The permeate flux through this membrane was initially high (140–180 LMH) and reduced to approx. 100 LMH after 10–12 min of operation. Increasing the initial humic acid feed concentration from 10 mg/L to 50 mg/L did not significantly decrease humic acid removal efficiency although the retentate flow rate was lower at higher concentrations. Finally the tap water was tested as the background solution and treated for the removal of humic acid. The presence of ions and other impurities in the tap water had little effect on humic acid removal. However, the permeate flux through 10 kDa membrane decreased from 100 LMH for milliQ water to 60 LMH for tap water after 20 min of operation.     

水环境中药物类PPCPs的赋存及处理技术进展

药品和个人护理品(PPCPs)类新兴污染物在水环境中被广泛检测出,因其生物累积性和潜在的生态危害性,近年来受到高度关注。文中总结了水环境中PPCPs的赋存状况,解析了水环境中PPCPs的来源和迁移、转化路径,发现传统污水处理厂尚不能彻底、有效地去除PPCPs,污水厂的尾水排放是水环境中PPCPs的重要来源。同时,比较了污水厂常规处理和三级处理工艺对PPCPs的去除效果,指出污水处理厂基于宏量常规污染物和微量新兴污染物的同步去除技术或复合去除技术是削减水环境新兴污染物浓度的核心途径,开发能够经济、高效地去除各类PPCPs的深度处理技术仍然十分必要。     

MASS TRANSFER IN MEMBRANE ABSORPTIONDESORPTION OF AMMONIA FROM AMMONIA WATER

Hydrophobic membrane can provide fast mass transfer for absorption-desorption of gasesform liquid to absorbent.The removal of ammonia from ammonia water and absorption with dilutesulphuric acid was studied in a pilot plant with polypropylene hollow fiber column,The removalrate and influences of operation temperature,flow rate and concentration on mass transferperformances were discussed mathematically.Experimental results and computer calculation show thatthe ammonia removal rate is not affected by the feed concentration for a given system.Both partialand overall mass transfer coefficients vary along the axis of the fiber,and the mass transfer for themembrane process is controlled by membrane resistance.     

Control of oxygen concentration in water using a hollow fiber membrane contactor

A novel theoretical analysis was performed to regulate the oxygen concentration in water using a membrane contactor composed of nonporous hollow fibers. The governing ordinary differential equations were derived for the countercurrent flow of the feed water and the feed gas in a membrane contactor. The governing equations were regarded as a two point boundary value problem. The nonlinear ordinary differential equations were simultaneously solved using a finite difference method. The computer program was coded in Fortran language using the Compaq Visual Fortran Software. It was found that the concentration of oxygen dissolved in water increases from 28.9 to 64.3 ppm as the area of the membrane increases from 1.24 to 3.73 m² at the given typical operating condition: the flow rate of the feed gas is kept to be 1.0 L/min; its pressure is maintained to be 4 atm; the flow rate of the water is 15 L/min. It is observed that the concentration of oxygen increases from 48.2 to 56.2 ppm as the concentration of the feed gas increases from 0.75 to 0.95 mole fraction. As the flow rate of the water increases from 15 to 25 L/min, the concentration of oxygen decreases from 56.2 to 38.6 ppm with a constant membrane area of 3.11 m².     

富营养化水体中致臭物质来源及其处理

以某水库水为原水,研究了5种给水处理工艺对水体藻类导致的嗅味的去除效果。试验结果表明:除常规处理工艺(嗅阈值去除率50%左右)外,其余4种工艺都可达到90%以上的除臭率。臭氧-粉末活性炭-常规处理工艺对嗅阈值的去除率最高,达到98%。实际应用中,建议臭氧的投加量为2mg/L、粉末活性炭的投加量为5mg/L。     

硅烷分子接枝ASZ陶瓷膜处理水中苯酚的研究

为了提高陶瓷膜的疏水性,本研究选择硅烷分子对氧化铝支撑氧化锆(ASZ)陶瓷膜进行接枝改性。考察接枝硅烷分子结构(反应基团类型)、碳链长度、硅烷分子中含氟和十七氟癸基三乙氧基硅烷(F17C8OEt3)浓度对疏水性的影响。利用SEM-EDS、FTIR、TGA和接触角测量仪对接枝改性ASZ膜或金属氧化物进行表征。研究结果表明,硅烷分子接枝ASZ膜的疏水性能显著提高,接触角从29°增加到136°。FT-IR、TGA结果证明了硅烷分子成功接枝在ASZ膜或金属氧化物上。利用F17C8OEt3硅烷分子接枝改性ASZ管式膜构建渗透蒸发系统处理水溶液中苯酚,实验结果表明,当进料液中苯酚浓度从672.3 mg/L增加至3 844.6 mg/L时,去除的苯酚浓度从29.1 mg/L增加到407.4mg/L;进料液的温度升高到80℃,去除的苯酚是进料液温度为40℃时的5倍。     

Effect of Process Parameters on Separation Performance of Nitrate by Electrodialysis

Abstract

The electrodialytic separation of nitrate from water was investigated as a function of feed characteristics such as applied voltage, feed flow rate, and nitrate concentration in the solution. The separation performance was evaluated in terms of percent removal of nitrate, process time, and energy consumptions. TS‐1‐10 electrodialysis equipment (Tokuyama) was used in experimental studies. During the unsteady state run of the ED system, both inlet and outlet concentrations of nitrate and conductivities of streams were measured at certain time intervals until the current drops to 0.01 A. It was obtained that the percent removal of nitrate from the solution increased when the concentration of nitrate in the feed solution increased. The operation time became shorter when a high potential was applied.     

聚乙烯醇/碳纳米管复合超滤膜的制备及应用研究

以聚乙烯醇(PVA)为基膜材料,以羧基化碳纳米管(c-CNT)为添加剂,采用浸没沉淀相转化法制备了一种新颖的PVA/c-CNT复合超滤膜.考察了c-CNT的用量对膜力学性能、水通量、截留率及耐污染性能的影响.结果表明,当c-CNT用量为2份时,复合超滤膜的拉伸性能、水通量、截留率均达到最佳,膜的抗污染能力得到提高.分别...     

碳纳米管及其复合材料在水中有机污染物去除中的应用

在人类社会高速发展的同时,一些有机污染物被排入水体中造成严重的环境污染,其中部分有机物被证明对人体和水中生物存在直接或潜在的毒性。碳纳米管作为一种结构特殊且具有良好电学、力学、化学性质的新型一维纳米材料,在水处理中得到了广泛的应用。文中总结了碳纳米管及其复合材料的制备方法,及其在吸附、高级氧化、膜分离3种工艺中的应用情况,简述了污染物的反应去除机理及协同效应等。同时,对碳纳米管在水处理领域中的发展前景进行了展望。     

N, O-羧甲基壳聚糖复合纳滤膜的制备及其对酒厂发酵废水的截留效果

N, O-carboxymethyl chitosan （NOCC） composite nanofiltration （NF） membranes were prepared by coating and cross-linking. The fermentation effluent from a wine factory was treated with the resulting NOCC/polysulfone （PSF） composite NF membranes. The permeate flux and the removal efficiencies of the resulting NF membranes for the color, chemical oxygen demand （CODcr）, total organic carbon （TOC）, and conductivity of the fermentation effluent were investigated in relation to the driving pressure, the feed flow, and the operation time. The permeate flux and the removal efficiencies were found to increase with the increase of the driving pressure or the feed flow. At 0.40 MPa and ambient temperature the removal efficiencies were 95.5%, 70.7%, 72.6%, and 31.6% for color, CODcr, TOC, and conductivity, respectively. The membrane was found to be stable over a 10-h ooeration for the fermentation effluent treatment.     

超滤技术回收乳制品废水中蛋白质

以回收乳制品废水中的蛋白质为目的,研究了超滤技术回收乳制品废水中蛋白质的工艺,系统地讨论了操作压力、进料流量、浓缩比等因素对回收效果的影响,并考查了超滤膜对COD的去除率。在本实验条件下,超滤膜法回收乳制品废水中蛋白质的最佳操作压力为1.0 MPa,进料流量为32 L/min。在此最佳操作压力和进料流量下,蛋白质回收率为97.18%,COD的去除率为86%,而超滤膜透过液可为随后的纳滤膜法回收乳糖提供优质的进料。     

The effect of air distribution on the induced air flotation of fine oil in water emulsions

The induced air flotation (IAF) of a highly stabilized oil in water (o/w) emulsion has been studied experimentally in a batch column 10 cm in diameter and 150 cm in height. Column performance was strongly affected by the method of air distribution. The main variables investigated were the type of air distributor (either porous plate, single hole plate, or multi-hole plate), initial oil concentraton (30-600 mg/L), oil drop size distribution of feed (1.0-30 μm), surfactant type, and gas superficial velocity. Results were successfully analyzed in terms of a first order kinetic rate model which yielded a removal rate constant (K₁) that varied from 2.0 to 60.0 h^?1. Corresponding total organic carbon (TOC) removal efficiencies went from 20 to 99.9 percent, illustrating the wide performance range for the flotation cell.     

Oxidized carbon nanotubes for simultaneous removal of endrin and Cd(Π) from water and their separation from water

BACKGROUND: Previous investigation has shown that carbon nanotubes (CNTs) are effective for the removal of organic pollutants and oxidized carbon nanotubes (OCNTs) are effective for the removal of heavy metals. In this investigation, OCNTs were used for simultaneous removal of endrin and Cd(Π) from water. Separation of OCNTs from water was also investigated. RESULTS: The removal efficiencies of endrin and Cd(Π) by OCNTs were 89–97% and 96–100%, respectively. Endrin removal capacity of OCNTs is approximately the same as that of powdered activated carbon (PAC) and as‐prepared CNTs. Cd(Π) removal capacity of OCNTs is much higher than that of PAC and as‐prepared CNTs. OCNTs can be separated efficiently from water using AlCl₃. CONCLUSION: OCNTs are effective for the simultaneous removal of endrin and Cd(Π) and after adsorption, OCNTs can be separated from water by dosing AlCl₃. Copyright © 2008 Society of Chemical Industry     

Diameter control of multiwalled carbon nanotubes using experimental strategies

Multiwalled carbon nanotubes (MWNTs) were synthesized using a chemical vapor deposition floating feed method in a vertical reactor. Effects of the preparation variables on the average diameter of carbon nanotubes were systematically examined using the fractional factorial design (FFD), path of the steepest ascent, and central composite design (CCD) coupled with the response surface methodology. From the FFD study, the main and interactive effects of reaction temperature, methane flow rate, and chamber pressure were concluded to be the key factors influencing the diameter of MWNTs. Two empirical models, representing the dependence of the diameter of carbon nanotubes at the vicinities around maximum (420 nm) and minimum (15 nm) on the reaction temperature and methane flow rate, were constructed in two independent CCD studies. These models, shown as contour diagrams, indicated that the diameter of carbon nanotubes generally increased with increasing reaction temperature and methane flow rate. Based on both models, the diameter of MWNTs from 15 to 420 nm can be controlled precisely by using a continuous CVD fabrication method.