Multi-functional forward osmosis draw solutes for seawater desalination

Forward osmosis (FO), as one of the emerging desalination technologies, has the potential to produce freshwater from a variety of water sources by utilizing the osmotic pressure gradient across a semi-permeable membrane. Drawsolution, as an essential component of any FO process, can extract watermolecules fromseawater orwastewater. 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.     

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.     

A novel ammonia—carbon dioxide forward (direct) osmosis desalination process

A novel forward (direct) osmosis (FO) desalination process is presented. The process uses an ammonium bicarbonate draw solution to extract water from a saline feed water across a semi-permeable polymeric membrane. Very large osmotic pressures generated by the highly soluble ammonium bicarbonate draw solution yield high water fluxes and can result in very high feed water recoveries. Upon moderate heating, ammonium bicarbonate decomposes into ammonia and carbon dioxide gases that can be separated and recycled as draw solutes, leaving the fresh product water. Experiments with a laboratory-scale FO unit utilizing a flat sheet cellulose tri-acetate membrane demonstrated high product water flux and relatively high salt rejection. The results further revealed that reverse osmosis (RO) membranes are not suitable for the FO process because of relatively low product water fluxes attributed to severe internal concentration polarization in the porous support and fabric layers of the RO membrane.     

正渗透过程中汲取质反向渗透研究进展

正渗透(FO)作为一种浓度驱动的膜技术,因其膜污染轻、能耗低和回收率高等优点而逐渐成为膜技术领域的研究热点之一。汲取质的反向渗透是正渗透过程中不可忽视的现象,但其研究相对比较滞后。本文主要介绍了汲取质反渗模型的研究进展,分析了渗透压差、膜表面流速、膜结构与膜材料、温度、汲取质种类、膜取向、离子水力半径等因素对汲取质反向渗透的影响情况,并发现汲取质的反向渗透通量可由其浓度或汲取液渗透压的一元多项式表达。总体而言,FO模式的汲取质反渗模型经过不断发展已相对比较完善,而压力阻尼渗透(PRO)模式的反渗模型则缺陷较大,有待进一步研究;此外,关于汲取质反渗过程影响因素及其影响机制的研究对于汲取质、膜材料的选择与开发,以及正渗透过程的优化均具有重要的指导作用,因此会引起越来越多的关注。     

Poly(vinyl) alcohol coating of the support layer of reverse osmosis membranes to enhance performance in forward osmosis

Membrane hydrophilicity influences the transport of water through the membrane in osmotically driven separations such as forward osmosis. In this paper, we coated the polysulfone support layer of two types of commercially available reverse osmosis membranes (brackish water and seawater) with hydrophilic polyvinyl alcohol (PVA). The aim of this was to increase the support layer hydrophilicity and, correspondingly, the rate of water transport through the membrane. Previous work with polydopamine coatings of the polysulfone support of reverse osmosis membranes has yielded promising results. In this work, we explore more readily available materials. Specifically, we studied the effects of two different PVA crosslinking agents – maleic acid and glutaraldehyde – on the resultant membrane properties and osmotic performance. For seawater membranes we found that PVA crosslinked to a limited degree with maleic acid creates a significant improvement in water flux in RO and FO systems, as compared to membranes with PVA crosslinked by glutaraldehyde. However, brackish water membranes did not have comparably significant changes in membrane performance. We conclude that the smaller pores of the brackish water membrane become clogged, and this effect is magnified by the lack of fractional free volume available within PVA that is highly crosslinked with glutaraldehyde.     

Synthesis and application of ethylenediamine tetrapropionic salt as a novel draw solute for forward osmosis application

The development of suitable draw solutes for forward osmosis (FO) process is a big obstacle on the way of its real industrialization. In this work, a novel draw solute, ethylenediamine tetrapropionic (EDTP) acid (salt) is developed for FO application. The successful synthesis is confirmed by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and high resolution mass spectrum. By optimizing the pH of EDTP solution, its composition is varied, and therefore, its water solubility and osmotic pressure are effectively improved. The effects of EDTP concentration on the osmotic pressure and FO performance are also investigated. Its outstanding osmotic pressure and big molecular size result in a high water flux of 22.69 LMH and a low salt flux of 0.32 gMH with 0.8 M EDTP draw solution (water as the feed solution, pressure retarded osmosis mode). The good stability and easy recovery by nanofiltration of EDTP solution also demonstrate its great potential as the draw solute for future FO applications. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1309–1321, 2015     

微乳液法制备Fe3O4/TiO2磁性纳米粒子

采用多元醇还原法制备出平均粒径为6.0 nm的Fe3O4磁性纳米粒子,以此磁性纳米粒子为核,在OP-10/正丁醇/环己烷/浓氨水反向微乳体系中制备出Fe3O4/TiO2磁性纳米复合粒子,通过XRD,TEM,VSM对复合粒子进行性能表征。结果表明,采用微乳液法能够制备出Fe3O4/TiO2磁性纳米复合粒子,并且包覆后比饱和磁化强度有所下降,但矫顽力仍趋近于0,显示超顺磁性。     

羧甲基淀粉包覆Fe_3O_4磁性纳米颗粒的制备与表征

利用共沉淀法制备了CMS@Fe3O4磁性纳米颗粒。利用扫描电子显微镜、红外光谱、Zeta电位分析仪以及振动样品磁强计表征了纳米颗粒的形态以及性质。磁性纳米颗粒类似于球状,平均直径为(35±10)nm。结果表明,在较高的pH范围内粒子有较高的负电顺磁性。30 d后考察了CMS@Fe3O4磁性纳米颗粒的稳定性,CMS@Fe3O4磁性纳米颗粒在pH值为11时保持较好的稳定性。     

Forward osmosis water desalination: Fabrication of graphene oxide-polyamide/polysulfone thin-film nanocomposite membrane with high water flux and low reverse salt diffusion

This paper investigates the synthesis of graphene oxide (GO)-incorporated polyamide thin-film nanocomposite (TFN) membranes on polysulfone substrate for forward osmosis applications. The GO nanosheets were embedded into polyamide layer using different concentrations (0.05?0.2 wt%). The results represented the alteration of polyamide surface by GO nanosheets and enhancing the surface hydrophilicity by increasing the GO loading. The results showed that the water flux for 0.1 wt% GO embedded nanocomposite (TFN) membrane was 34.7 L/m² h, representing 90% improvement compared to the thin-film composite, while the salt reverse diffusion was reduced up to 39%.     

Fe_3O_4纳米颗粒的制备及其净化含油污水的研究

采用沉淀法在碱性条件下不使用任何表面活性剂直接制备出Fe3O4纳米颗粒。用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、XRD粉末衍射仪、振动样品磁强计及激光粒度分析仪对制备的纳米颗粒性质进行了表征。结果显示所制得的Fe3O4颗粒单颗平均粒径约为9 nm,具有超顺磁性,晶型单一,比饱和磁化强度为53.279 emu/g,在水中分散后粒度集中分布在10—26 nm和114—150 nm这2个区域。将其应用于油田污水处理,并与粒度分布在0.5—1.0μm的市售Fe3O4粉末以及活性炭粉末的除油效果进行了对比,研究了3种粉末不同质量分数与净化效果的关系以及磁性纳米颗粒净化油田污水的机理。     

疏水修饰磁性壳聚糖载药纳米粒子的制备与表征

利用O-羧甲基壳聚糖(O-CMC)的表面多种官能团(如-NH_2,-OH,-COOH等)与胆酸(CA)进行化学修饰得到两亲性共聚物,再以反溶剂法将Fe_3O_4和阿霉素(DOX)包埋在两亲性共聚物疏水的核中,制备两亲性的磁性壳聚糖载药纳米粒子,并对磁性载药纳米粒子的形貌、粒径大小、磁性、药物控释等进行了研究。结果表明:磁性壳聚糖纳米粒子有较高的药物包埋效率(92.3%),与自由阿霉素相比,磁性复合物具有明显的缓释作用和pH响应性;同时,有较好的超顺磁性。这些说明制备的疏水修饰磁性壳聚糖载药纳米粒子具有双重响应性,有望作为药物输送载体对肿瘤进行实时跟踪、诊断和治疗。     

Synthesis and characterization of novel conducting composites of Fe3O4 nanoparticles and sulfonated polyanilines

Surface charged iron oxide (Fe₃O₄) nanoparticles were used for the synthesis of sulfonated polyaniline (SPAN)‐Fe₃O₄ nanocomposites (SPAN/Fe₃O₄‐NCs). 2,5‐diaminobenzenesulfonic acid (DABSA) and 2‐aminobenzenesulfonic acid (ABSA) were independently polymerized with aniline to form SPAN. The structure of the composites was characterized by means of transmission electron microscopy (TEM), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectra, conductivity and magnetic properties. TEM reveals that Fe₃O₄ nanoparticles are “glued” with SPAN in the composite. TGA indicates that SPAN/Fe₃O₄‐NCs are having better thermal stability. The room temperature conductivity of SPAN/Fe₃O₄‐NCs is higher than that of pristine PANI and SPAN. SPAN/Fe₃O₄‐NCs exhibits magnetic behavior. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 4127–4134, 2007     

Promotional effect for SCR of NO with CO over MnOx-doped Fe3O4 nanoparticles derived from metal-organic frameworks

MnO_x-Fe₃O₄ nanomaterials were fabricated by using the innovative scheme of pyrolyzing manganese-doped iron-based metal organic framework in inert atmosphere and exhibited extraordinary performance of NO reduction by CO (CO-SCR). Multi-technology characterizations were conducted to ascertain the properties of fabricated materials (e.g., TGA, XRD, SEM, FT-IR, XPS, BET, H₂-TPR and O₂-TPD). Moreover, the interaction between reactants and catalysts was ascertained by in situ FT-IR. Experimental results demonstrated that Mn was an ideal promoter for iron oxides, resulting in decrease of crystallite size, improve reducibility property, enhance the mobility and the amount of lattice O^2- species, as well as strength the adsorption ability of active NO and CO to form multiple species (e.g., nitrate and carbonate). The unprecedented enhancement of CO-SCR activity over Mn-Fe nanomaterials follows the Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) reaction pathway.     

撞击流反应器制备纳米四氧化三铁的研究

在浸没式循环撞击流反应器中,以氨水为沉淀剂,用七水合硫酸亚铁和六水合三氯化铁为原料,采用共沉淀法制备了纳米四氧化三铁粒子。考察了搅拌转速、亚铁与三价铁物质的量比、反应温度和溶液pH对所得纳米四氧化三铁的分散性和粒径的影响。采用傅里叶红外光谱仪、透射电镜、X射线衍射仪等对制得的纳米粒子的结构和性能进行了表征。结果表明：用撞击流反应器制备纳米四氧化三铁粒子的最佳工艺条件：亚铁与三价铁物质的量比为1 ∶1,反应温度为40 ℃,搅拌转速为1 600 r/min,以氨水作沉淀剂,最佳pH控制在11.0左右。在上述条件下,可以制备出分散性好、纯度高、平均粒径为10 nm的四氧化三铁粒子。     

Intensification of levofloxacin sono-degradation in a US/H2O2 system with Fe3O4 magnetic nanoparticles

Fe3O4 magnetic nanoparticles (MNPs) were synthesised, characterised, and used as a peroxidase mimetic to ac-celerate levofloxacin sono-degradation in an ultrasound (US)/H2O2 system. The Fe3O4 MNPs were in nanometre scale with an average diameter of approximately 12 to 18 nm. The introduction of Fe3O4 MNPs increased levofloxacin sono-degradation in the US/H2O2 system. Experimental parameters, such as Fe3O4 MNP dose, initial solution pH, and H2O2 concentration, were investigated by a one-factor-at-a-time approach. The results showed that Fe3O4 MNPs enhanced levofloxacin removal in the pH range from 4.0 to 9.0. Levofloxacin removal ratio in-creased with Fe3O4 MNP dose up to 1.0 g·L?1 and with H2O2 concentration until reaching the maximum. More-over, three main intermediate compounds were identified by HPLC with electrospray ionisation tandem mass spectrometry, and a possible degradation pathway was proposed. This study suggests that combination of H2O2, Fe3O4 MNPs and US is a good way to improve the degradation efficiency of antibiotics.     

磁性CuO—Bi2O3催化剂的制备及炔化性能

采用溶胶凝胶法结合等体积浸渍法制备了具有磁性的CuO—Bi2O3／Fe3O4@SiO2催化剂,利用XRD、BET等手段进行表征,并考察了催化剂在甲醛乙炔化反应中的催化性能。结果表明,载体Fe3O4@SiO2具有较高的比表面积,CuO在其表面以高分散的微晶态形式存在;制得的催化剂在甲醛乙炔化反应中有较高的活性与使用稳定性,可以在外加磁场的作用下与反应液快速分离。     

Influence of magnetic casting on the permeability and anti-fouling properties of a novel iron oxide/alumina/polysulfone mixed matrix membrane

Novel mixed matrix membranes (MMMs) were fabricated using Fe₃O₄, and Al₂O₃ nanoparticles (NPs) were added to the polysulfone (PSf) and N-methylpyrrolidone (NMP) solution. The nanocomposite membranes were fabricated using the NIPS (non-solvent induced phase separation) method. In order to create preferential permeation pathways for water across the MMMs, membrane formation is accomplished with an external magnetic field. Using magnetic casting cause the targeted placement of NPs in the best location and orientation. The performance of the prepared membranes was examined in terms of pure water flux and fouling parameters. Magnetic casting considerably increased pure water flux and decreased the total resistance of the optimum mixed matrix membrane, which contains 0.2% wt. of Fe₃O₄ NPs to 1175 L/m²h and 13.4 * 10¹¹ (m⁻¹), respectively. This is explained by the ordering of magnetic nanoparticles on the membrane sub-layer cast under the magnetic field of 500 mT, which changed the sub-layer structure. Less rough membrane surface of the mixed matrix membranes offered preferable anti-fouling properties against fouling by BSA proteins. The characterization of fabricated membranes was carried out using field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), energy dispersive X-ray (EDX), and water contact angle measurement methods.     

油相稳定分散Fe3O4纳米粒子的制备研究

分别采用热分解法及共沉淀油酸同步修饰法制备了2种可以在油相稳定分散的Fe3O4纳米粒子,并对热分解法制备Fe3O4纳米粒子的反应条件进行了优化,考察了热分解温度、熟化时间对颗粒粒径、形貌及磁性能的影响。通过TEM、VSM和FTIR等表征手段对2种方法制备的Fe3O4纳米粒子的油相分散稳定性、颗粒形貌及粒径、比饱和磁化强度及表面性质进行了比较。结果表明:热分解法制备的Fe3O4纳米粒子表现出更好的油相分散稳定性,共沉淀油酸同步修饰法制备的Fe3O4纳米粒子则表现出更好的磁响应性。