Investigation on removing recalcitrant toxic organic polluters in coking wastewater by forward osmosis

Investigation was made on the efficiency of two commercial membranes in removing via forward osmosis(FO)the low molecular weight organic compounds typical of coking wastewater. The membranes were supplied by Poten and HTI companies. The organics in the simulated coking water were indole and pyrridine. Under FO mode, the rejection to the organics by Poten membrane was around 50%, whereas that for HTI membrane was obviously higher, ranging from 65% to 74%. The response of the two membranes in terms of Water flux and reverse salt flux(RSF) towards changing feed/draw solution(DS) flow rates in FO mode showed similar tendency,but different degree. Generally, the flux in FO using HTI membranes was lower. For HTI membrane, FO operated with pressure retarded osmosis(PRO) mode was also performed and the overall rejection of the organics was slightly lower than that in FO mode. In the long term FO test within 15 days, both Poten and HTI membranes displayed flux reduction and rejection enhancement. But the variation with Poten membrane was much more obvious. Discussion was carried out about the reasons and the mechanisms behind the FO performance difference between two membranes and the variation in flux and rejection with operation conditions. Characterizations by SEM, FTIR, AFM, XRD and XPS were tried to support the proposed explanations.

不同粒径UiO-66混掺改性TFN-FO膜的构建及性能评价

以锆基金属-有机骨架材料(MOFs)UiO-66作为研究对象,制备了三种不同粒径的UiO-66纳米颗粒,并将其混掺到薄层复合膜(TFC)的聚酰胺(PA)层内,研究了UiO-66纳米颗粒的粒径对薄层复合纳米正渗透(TFN-FO)膜性能的影响。通过扫描电子显微镜(SEM)、原子力显微镜(AFM)、水接触角(WCA)测量仪、X射线光电子能谱仪(XPS)等表征手段,探究了TFN-FO膜的性质变化。结果表明,减小UiO-66的粒径不会影响TFN-FO膜的高亲水性,并且随着UiO-66粒径的减小,TFN-FO膜的粗糙度降低、交联度升高。通过以去离子水和2 mol/L氯化钠溶液作为进料液和汲取液的实验室自制的正渗透系统对膜性能进行评价,发现混掺小粒径(50 nm)UiO-66的TFNFO膜可以在保持较低反向盐通量的同时实现35%的水通量提升。有机污染实验表明,TFN-FO膜具有良好的抗污染性能。

A Combined Forward Osmosis and Membrane Distillation System for Sidestream Treatment

Separate treatment of high-nutrient sidestream is an efficient and cost effective way to decrease the loading on the main plant, resulting in lower effluent nutrient concentration. This study investigated the use of a combined forward osmosis-membrane distillation (FO-MD) system for the removal of nitrogen present in high concentration in sidestream from anaerobic digestion process. The combined system was able to achieve almost 100% rejection of solids and acetic acid, and more than 98% rejection of NH3-N from the sidestream. The high rejection of NH3-N was mainly achieved by the FO process. The solids in the feed solution contributed to fouling problem in both FO and MD, resulting in significant decline in flux. However, 76% or higher flux recovery was achieved for FO membrane by cleaning with tap water. We observed that flux recovery was due to removal of solids from the membrane surface by the cleaning process. FO membrane also demonstrated excellent performance for continuous operation when cleaned for 15 min in every 24 h interval. Overall, the combined FO-MD system was found to be an effective solution for treatment of nutrient rich sidestream.

An agent-based simulation with NetLogo platform to evaluate forward osmosis process(PRO Mode)

Forward osmosis(FO), as an emerging technology, is influenced by different factors such as operating conditions,module characteristics, and membrane properties. The general aim of this study was to develop a suitable(flexible,comprehensive, and convenient to use) computational tool which is able to simulate osmosis through an asymmetric membrane oriented in pressure retarded osmosis(PRO) mode in a wide variety of scenarios. For this purpose, an agent-based model was created in NetLogo platform, which is an easy-to-use application environment with graphical visualization abilities and well suited for modeling a complex system evolving over time. The simulation results were validated with empirical data obtained from literature and a great agreement was observed. The effect of various parameters on process performance was investigated in terms of temperature,cross-flow velocity, length of the module, pure water permeability coefficient, and structural parameter of the membrane. Results demonstrated that the increase in all parameters, except structural parameter of the membrane and the length of module led to the increase of average water flux. Moreover, nine different draw solutes were selected in order to assess the influence of net bulk osmotic pressure difference between the draw solution(DS) and feed solution(FS)(known as the driving force of FO process) on water flux. Based on the findings of this paper, the performance of FO process(PRO mode) can be efficiently evaluated using the NetL ogo platform.

Multi-functional forward osmosis draw solutes for seawater desalination

Forward osmosis(FO), as one of the emerging desalination technologies, has the potential to produce fresh water from a variety of water sources by utilizing the osmotic pressure gradient across a semi-permeable membrane.Draw solution, as an essential component of any FO process, can extract water molecules from seawater or wastewater. An ideal draw solution should meet three essential requirements, namely high osmotic pressure, low reverse flux, and facile regeneration mechanism. The selection of proper draw solutes is especially critical for an energy-efficient FO process since the energy consumption mostly arises from the separation or regeneration of the draw solution. Recently, we developed a few multi-functional FO draw solutes, mainly aiming to enhance the FO water flux and to explore facile re-concentration methods. This review summarizes these draw solutes,including Na^+_- functionalized carbon quantum dots, thermoresponsive copolymers, hydrophilic magnetic nanoparticles, and thermoresponsive magnetic nanoparticles.

Potential use of nanofiltration like-forward osmosis membranes for copper ion removal

The discharge of industrial effluent containing heavy metal ions would cause water pollution if such effluent is not properly treated.In this work,the performance of emerging nanofiltration(NF)like-forward osmosis(FO)membrane was evaluated for its efficiency to remove copper ion from water.Conventionally,copper ion is removed from aqueous solution via adsorption and/or ion-exchange method.The engineered osmosis method as proposed in this work considered four commercial NF membranes(i.e.,NF90,DK,NDX and PFO)where their separation performances were accessed using synthetic water sample containing 100 mg·L-1 copper ion under FO and pressure retarded osmosis(PRO)orientation.The findings indicated that all membranes could achieve almost complete removal of copper regardless of membrane orientation without applying external driving force.The high removal rates were in good agreement with the outcomes of the membranes tested under pressuredriven mode at 1 MPa.The use of appropriate salts as draw solutes enabled the NF membranes to be employed in engineered osmosis process,achieving a relatively low reverse solute flux.The findings showed that the best performing membrane is PFO membrane in which it achieved N 99.4%copper rejection with very minimum reverse solute flux of<1 g·m-2·h-1.

An easily recoverable thermo-sensitive polyelectrolyte as draw agent for forward osmosis process

As a potential solution to the crises of energy and resources, forward osmosis(FO) has been limited by the development of draw agents. An ideal draw agent should be able to generate high osmotic pressure and can be easily recovered. In this study, a thermo-sensitive polyelectrolyte of poly(N-isopropylacrylamide-co-acrylic acid)(PNA)is developed as an efficient draw agent, and two easy and simple methods are proposed to effectively recover the polyelectrolytes. After adjusting the pH value of polyelectrolyte solutions to around 6.0, the polyelectrolyte can generate relatively high osmotic pressure, and induce average water fluxes of 2.09 and 2.95 L·m^(-2)·h^(-1) during12 h FO processes when the polyelectrolyte concentrations are 0.20 and 0.38 g·ml^(-1) respectively. After acidifying and heating to 70 °C, the PNA-10 polyelectrolyte can aggregate together because of hydrophobic association and separate from water, so it can be easily recovered by either simple centrifugation or gravitational sedimentation. The recovery ratios of PNA-10 polyelectrolyte in both methods are as high as 89%, and the recovered polyelectrolytes can be reused with almost the same FO performance as fresh ones. The results in this study provide valuable guidance for designing efficient and easily recoverable draw agents for FO processes.

Osmotic concentration of succinic acid by forward osmosis:Influence of feed solution pH and evaluation of seawater as draw solution

In this study, we investigated the essential role of feed solution pH so as to gain insights into the transport mechanisms of succinic acid concentration by osmotically-driven forward osmosis(FO) process. FO performances including water flux and bidirectional transport of succinate and chloride anions were systematically examined using cellulose triacetate-based FO membrane. Additionally, real seawater was explored as draw solution. Experimental results revealed that the p H-dependent speciation of succinic acid can affect the FO performances. Ionization of succinic acid at higher solution p H enhanced the osmotic pressure of feed solution, thus leading to lower water flux performance. A strong effect was pointed out on the succinate rejection for which nearly 100% rejections were achieved at p H above its pK_(a2) value. The rejection of succinate increased in the following order of chemical form: C_2H_4 C_2O_4H_2 < C_2H_4C_2O_4H~ˉ < C_2H_4C_2O_4^(2-).With real seawater as the draw solution, low to moderate water fluxes(<4 L·m^(-2)·h^(-1)) were observed.The divalent succinate anion was highly retained in the feed side despite differences in the succinic acid feed concentration at p H of approximately 6.90.

Layer by Layer Assembly of Poly(Allylamine Hydrochloride)/Phosphate Ions and Poly(Sodium 4-Styrene Sulfonate) Membrane for Forward Osmosis Application

Based on the layer by layer(Lb L)assembly technology,the nano-scale composite membrane with excellent structure can be prepared by changing the polyelectrolyte and controlling the deposition conditions.Polyamines and phosphate ions(Pi)can be self-organized to form supramolecular systems which could be exploited to stabilize the interfacial architecture.The LbL membrane was made of the positively charged poly(allylamine hydrochloride)(PAH)self-organized with Pi and the negatively charged poly(sodium 4-styrene sulfonate)(PSS)alternatively on top of a poly(acrylonitrile)(PAN)substrate.Compared to the membrane without Pi,the membrane assembled by PAH/Pi improved forward of flux and reduced flux of salt.The concentration of PAH and PSS,deposition time,pH and number of layers showed significant influences on the performance of the membrane.In this experiment,we systematically investigated the preparation conditions and under the optimized conditions the prepared membrane exhibited high water fluxes of 13.5 L m^-2 h^-1 with corresponding salt to water flux,Js/Jv,ratio of 0.07 g L^-1 tested by forward osmosis when DI water as feed solution and 2 mol L^-1 MgCl2 as draw solution.

Potential of Magnesium Chloride for Nutrient Rejection in Forward Osmosis

Wastewater may contain high levels of the nutrients: nitrogen and phosphorus. Excessive release of nutrients to the environment can cause severe environmental problem such as eutrophication leading to algal blooms, oxygen deficiency, and fish kills. The forward osmosis (FO) could be a choice of treatment. FO process presents the results of using four kinds of variation in concentration of magnesium chloride (MgCl2) as draw solution and the two kinds of commercial membranes for nutrient rejection in the same cross flow velocity at 0.25 m/s and temperature at 25°C. Nutrients consisting of nitrogen (nitrite, nitrate, and ammonium) and phosphorus (phosphate) in feed solution were successfully rejected with an efficiency of mostly more 95%. The water flux in membrane HTI-NW achieved lower 7.55 - 9.61 L/m2·hr than in membrane HTI-ES that exceeds until 13.58 - 15.10 L/m2·hr. The reverse solute in membrane HTI-NW is seemly constant along all concentration of DS MgCl2 that the chloride diffusion is slightly higher than magnesium. In membrane HTI-ES, the reverse solute of chloride was almost three times than that of magnesium. The concentration of MgCl2 plays a significant role in rejecting nutrients by the Donnan’s potential and the diffusion constant in low and high concentration of DS, respectively.

Harvesting Microalgae Biomass Using Sulfonated Polyethersulfone(SPES)/PES Porous Membranes in Forward Osmosis Processes

This study was performed to investigate the availability of forward osmosis(FO)for microalgae harvesting using sulfonated polyethersulfone(SPES)/PES porous membranes.In FO process,porous membranes(<25.0 L m^−2 h^−1)exhibited more superior water flux than TFC FO membranes(<2.6 L m^−2 h^−1).Furthermore,the incorporation of SPES has been demonstrated to enhance membrane performance.The effects of SPES content on pore structure and separation performance were investigated.Compared with pure PES porous membranes,porous membranes with 40%SPES yielded an improved hydrophilicity and greater porosity.It exhibited two times higher water fluxes than the pure PES porous membrane.For microalgae harvesting,AL-FS mode(active layer facing the feed solution)was more favourable than AL-DS mode(active layer facing the draw solution)because less deposited microalgae on the active layer mitigate the membrane biofouling.FO operation combined with SPES/PES porous membranes is conducive to preserving microalgae cell integrity under the mild condition.In addition,FO membrane can be cleaned by a simple water rinse.Potential implications were highlighted as a sustainable method for microalgae harvesting because of no pressure input and less chemical cleaning demand.

Preparation of novel magnetic nanoparticles as draw solutes in forward osmosis desalination

Novel magnetic nanoparticles(MNPs),Fe_(3)O_(4)@SiO_(2) and Fe_(3)O_(4)@SiO_(2)@PEG-(COOH)_(2),were prepared by loading different amounts of SiO_(2) or/and PEG-(COOH)_(2) onto Fe_(3)O_(4) nanoparticles,and their feasibility to be used as forward osmosis(FO)draw solutes was investigated.The characterization of the materials showed that,compared to normal Fe_(3)O_(4) nanoparticles,the modified MNPs exhibited enhanced dispersity and high osmotic pressure in aqueous solution.The FO experiment indicated that the synthesized draw solutes could obtain a water flux as high as 10 L·m^(-2)·h^(-1) with an aquaporin FO membrane.The optimal concentration of the added tetraethyl orthosilicate was 30%during the synthesis.The novel MNPs could be easily recovered from draw solutions by magnetic field,and the recovery rate of Fe_(3)O_(4)@SiO_(2) and Fe_(3)O_(4)@SiO_(2)@PEG-(COOH)_(2) was 83.95%and 63.37%,respectively.Moreover,after 5 recycles of reuse,the water flux of Fe_(3)O_(4)@SiO_(2) and Fe_(3)O_(4)@SiO_(2)@PEG-(COOH)_(2) as draw solutes still remained 64.36%and 85.26%,respectively.The experimental results demonstrated that the synthesized core–shell magnetic nanoparticles are promising draw solutes,and the Fe_(3)O_(4)@SiO_(2)@PEG-(COOH)_(2) was more suitable to be used as draw solute in FO process.

Influence of Temperature on the Performance of Forward Osmosis Using Ammonium Bicarbonate as Draw Solute

This study investigated the influence of temperature on the performance of forward osmosis(FO) under the condition that the feed solution(FS) temperature was diff erent from draw solution(DS) temperature. An FO model considering the mass and heat transfer between FS and DS was developed, and the FO experiment with ammonium bicarbonate solution as DS and sodium chloride solution as FS was carried out. The predicted water flux and reverse draw solute flux using the developed model coincided with the experimental fluxes. Increases in the temperature of FS or DS yield corresponding increases in the water flux, reverse draw solute flux, and forward rejection of feed solute. Compared with increasing the FS temperature, increasing the DS temperature has a more significant impact on enhancing FO performance. When the temperature of DS increased from 20 to 40 ℃, the specific reverse solute flux decreased from 0.231 to 0.190 mol/L.

PAM汲取液制备及FO浓缩模拟城市污水可行性

通过共沉淀法制备了超顺磁性纳米颗粒,并利用聚丙烯酰胺对其改性,制备了新型正渗透汲取液Fe_(3)O_(4)@PAM,探究其正渗透浓缩模拟城市污水的可行性。通过SEM、FTIR、XRD和VSM等技术对改性前后的磁性纳米颗粒形貌结构进行表征,表明PAM可很好地负载在Fe_(3)O_(4)表面。PAM、MNPs和Fe_(3)O_(4)@PAM汲取液在相同FO运行条件下,Fe_(3)O_(4)@PAM汲取液的水通量最大,为5.1 L/(m^(2)·h);AM(PAM的前聚体)/MNPs在质量比分别为3、2.5、2、1.5时制备改性磁纳米颗粒,质量比为3制备的20 g/L的Fe_(3)O_(4)@PAM水通量最大,为7.7 L/(m^(2)·h);当Fe_(3)O_(4)@PAM(3∶1)的浓度从10 g/L增加至70 g/L时,水通量从4.3 L/(m^(2)·h)增至12.7 L/(m^(2)·h),呈稳定上升趋势;50 g/L的Fe_(3)O_(4)@PAM汲取液正渗透浓缩模拟城市污水,水通量最大可达10.5 L/(m^(2)·h),汲取液的3次重复利用后的平均回收率达到了84.3%,表明其有一定的城市污水浓缩可行性。

H2O2氧化/CaO沉淀预处理化学镀镍废槽液及其FO浓缩减量效果研究

为了降低高浓度化学镀镍废槽液处理成本,采用氧化-沉淀预处理-正渗透(FO)组合工艺对废槽液进行常温浓缩减量.FO膜为水通道蛋白膜(AQP),汲取液为4 mol·L^(-1)NaCl溶液,FO过程采用活性层朝向原料液(AL-FS)的模式.当采用H2O2加CaO进行预处理时,废液电导率、TP、TOC和Ni的去除率远高于其他预处理方案.当CaO添加量为5%时,系统水通量可达到5.89 L·(m^(2)·h)^(-1);浓缩后污染物TP、Ni和TOC的截留率分别达到73.97%、92.90%和84.65%.三维荧光图谱(EEM)结果显示,有机物类腐殖酸组分比酪氨酸或色氨酸蛋白类物质更容易透过半透膜从原料液进入到汲取液中.适量的CaO预处理不仅可以有效的降低污染物的浓度和渗透压,有利于后续FO工艺浓缩减量,而且节约了经济成本.

正渗透膜回收废水中氨氮的研究进展

综述了正渗透(FO)膜技术对废水中的氨氮回收的研究进展。重点介绍了其发展历史、工艺原理、应用现状,将应用现状分为膜制造和改性、膜与其它工艺的耦合工艺、提取液、膜污染、数学建模这五方面进行了综述。在此基础上,对正渗透膜技术的研究前景进行了展望。

温敏水凝胶的改性及其在正渗透工艺中的应用

温敏水凝胶是一种能够响应外界温度变化的聚合物材料。由于温敏水凝胶具一定的渗透压与易于脱水特性,因此可作为汲取剂应用于正渗透(FO)工艺中。但传统温敏水凝胶的溶胀能力较弱,导致FO工艺的水通量较低。因此需要对温敏水凝胶进行改性,从而获得更高的溶胀性能和渗透压,使温敏水凝胶在FO工艺中具有更广阔的应用前景。介绍了几种通过无机、有机改性的温敏水凝胶,以及其在FO中的应用情况。研究表明:通过添加具有亲水性物质(如无机物污泥灰、氧化石墨烯等,有机物如丙烯酸钠、聚乙二醇等)可有效提高水凝胶的溶胀性能,从而在FO工艺中获得更多的水通量;此外,添加碳颗粒、γ-Fe_(2) O_(3) 等材料可以提高水资源回收率,降低回收能耗。因此,改性后的温敏水凝胶在FO工艺中具有更广阔的应用前景。

基于“超滤——正渗透——膜蒸馏”工艺的中药废水利用研究

本文提出了基于“超滤—正渗透—膜蒸馏”(UF-FO-MD)耦合工艺的中药废水利用研究。通过设计模拟FO有效物质回收实验与UF-FO-MD耦合工艺处理实验,对比2组实验数据,验证该耦合工艺在实际中药废水处理中的应用效果。实验结果表明,经UF-FO-MD耦合工艺处理,实际中药生产废水中的回收效率明显提升。由此说明,该耦合工艺可有效回收中药废水中的有效物质和水资源,可在处理废水的同时,缓解中药生产的用水压力,可提高废水资源化利用的经济可行性,为中药生产废水资源化利用提供了创新方法。

基于不同厂家聚醚砜基膜的薄膜复合正渗透膜性能的比较

薄膜复合(TFC)膜由多孔基底层和通过界面聚合反应生成的聚酰胺层组成,在纳滤、反渗透和正渗透等领域已经得到广泛的应用.近年来,基底膜对TFC膜性能的影响受到越来越多的关注.早期实验数据显示,即使在制备方法和基底膜名义孔径完全相同的条件下,由不同厂家生产的基膜所制备的TFC膜也存在显著差异.本文选择两家公司名义孔径均为0.22μm的商品聚醚砜(PES)膜为基底,通过调节界面聚合过程水相的沥干时间,对比研究了2种基膜的不同性质及其对TFC膜性能的影响.结果表明,亲水性更强、膜孔位置分布更密集且均匀、孔径更均一的基膜具有更高的水通量和更低的反向盐质通量.此外,基于2种基膜的TFC正渗透膜的水通量均随沥干时间的拉长而呈现不断降低的趋势,而反向盐通量始终保持较低水平.综上,本研究可为未来TFC膜的规范化制备提供技术支持.

聚酰胺/醋酸纤维素复合正渗透膜的制备及相转化工艺参数的优化

正渗透(forward osmosis,FO)分离技术具有低操作压力、低能耗、膜污染程度轻等优点,可能成为解决世界上水资源匮乏和能源短缺等极具挑战性问题的潜在方案。然而,正渗透技术缺乏性能优异且稳定的FO膜被认为是限制其发展及应用的主要障碍之一。本文从调控相转化工艺参数出发,通过改变铸膜液中的致孔剂种类以及操作参数(涂布厚度、溶剂蒸发时间和凝固浴温度)来实现对醋酸纤维素(cellulose acetate,CA)基底结构和性能的有效调控,并采用界面聚合(interfacial polymerization,IP)的方法在这种亲水的多孔基底上制备聚酰胺(polyamide,PA)分离层,得到薄膜复合正渗透(TFC-FO)膜。实验结果表明,用10%(质量分数)CA、致孔剂A等组成的铸膜液在150μm浇铸刀下涂布,立即浸入25℃凝固浴相转化制得CA基底,再经界面聚合所得的TFC-FO膜的渗透选择性最佳,以1mol/L NaCl溶液作为汲取液,去离子水作为原料液,膜的FO水通量达10.94L/(m^(2)·h),反向盐通量为0.0500mol/(m^(2)·h),对NaCl的截留率为95.0%,结构参数为1404μm。