2D/2D nanohybrid of Ti3C2 MXene/WO3 photocatalytic membranes for efficient water purification

Photocatalytic membrane is attracting a great deal of current attention for water decontamination by taking the full advantage of photocatalysis and membrane separation. Herein, the well-defined WO₃ nanoplates are homogeneously dispersed onto the surface of multilayer Ti₃C₂ MXene to create a novel 2D/2D nanohybrid with various Ti₃C₂ contents (3–7 wt%) through a facile and cost-effective approach, and then photocatalytic membrane system is developed by anchoring these heterostructured-photocatalysts on polyvinylidene fluoride (PVDF) membrane by means of vacuum filtration. Ti₃C₂/WO₃/PVDF photocatalytic membranes exhibit enhanced RhB degradation and cyclability, alongside with refreshing behavior under visible-light illumination. We demonstrate that the excellent electrical conductivity of Ti₃C₂, the formation of built-in electric field and the large interface contact area between Ti₃C₂ and WO₃ synergetically promote the spatial charge separation and increase the surface reactive sites, which is responsible for boosting the photoreactivity and photostability. Besides, a significant high flux recovery of ～ 94% is obtained by 5 wt% Ti₃C₂/WO₃/PVDF membrane under visible light irradiation. This study opens possibilities to construct multi-functional and robust MXenes-based photocatalytic membrane for long-term water purification.     

Poly(ether-block-amide) membrane with deformability and adjustable surface hydrophilicity for water purification

Freshwater resources are currently insufficient, and another form of freshwater resources, namely, ice, is very interesting except for the issue of how to use new materials for effective purification during the processing procedure. In this article, a new membrane material with multisize pore structure in the cross-section and intact thin skin layer on the upper and lower surfaces was successfully prepared by adding porogen, filler and setting heating environment during the phase separation process. The membrane exhibits excellent axial deformability, and its elongation at break can reach to 160% strain. Meanwhile, they all show elastic deformation behavior in the range from −60 to 100°C. Even if high content of hydrophobic filler is compounded into these membranes, that is, 5.7 wt% carbon tube content, water contact angle of membrane's surface is only 72.5°, demonstrating obvious hydrophilicity. In addition, in the water purification process, the adsorption rate constant reached ideal value of 0.26 s⁻¹, and the equilibrium adsorption capacity was about 2.8 g/g, showing fast and efficient water purification ability. In the mode of external heating source or the membrane's heat dissipation, these prepared membranes can melt the ice to obtain purified water and exhibit a controllable purification ability in this process.     

Simultaneously tuning dense skin and porous substrate of asymmetric hollow fiber membranes for efficient purification of aggressive natural gas

Highly permeable, selective, and stable asymmetric membranes are required to replace the traditional separation approaches for natural gas purification with higher energy efficiency and smaller footprints. Herein, we report on the design and engineering of defect-free asymmetric hollow fiber membranes with a thin dense skin and highly porous substrate to effectively deal with aggressive natural gas. A crosslinkable polymer with rigid molecular structure and high molecular weight was synthesized for developing spinning dope with desirable solution properties. Phase separation behavior of the polymer was carefully controlled by systematic formulation of the dope composition and optimizing spinning conditions, thereby realizing simultaneously tuning dense skins and porous substrates of the spun asymmetric hollow fiber membranes. The crosslinked hollow fiber membrane, with well-preserved delicate asymmetric nanostructures, exhibited unprecedentedly high and stable separation performance for long-term processing extremely aggressive CO₂/CH₄ mixtures (with pressure up to 820 psi containing C6⁺ hydrocarbons), thereby showing great potential for practical application of natural gas purification. This work offers a new platform to create hollow fiber membranes with both high permeance and plasticization resistance in natural gas service. © 2019 American Institute of Chemical Engineers AIChE J, 65: 1269–1280, 2019     

纳滤膜在功能性低聚糖分离纯化中的应用研究进展

功能性低聚糖具有抗肿瘤、抗放射、抗凝血、消炎和调节免疫力等医疗保健作用,广泛应用于食品科学和生物医药等领域。纳滤作为一种高效的膜分离技术,在功能性低聚糖的分离与纯化中的应用得到越来越多的关注。本文分析了纳滤膜对功能性低聚糖的分离机理,综述了纳滤膜在功能性多糖分离纯化中的应用进展,讨论了纳滤分离过程的影响因素,主要包括功能性多糖料液的性质、膜过程的操作参数以及膜材料本身的性质等。其中,料液的性质主要体现在组成、浓度、黏度等方面;操作参数主要体现在压力、温度、膜面流速和pH等方面;而膜材料的性质主要体现在微结构和表面性质两个方面。最后,进一步指出纳滤膜技术用于功能性多糖分离纯化时在设备成本、膜材料及膜污染等方面存在的问题,并对未来纳滤膜技术在低成本专用膜材料及系统开发和膜污染控制方面的研究进行了展望。     

Molecular-scale hybrid membranes: Metal-oxo cluster crosslinked benzimidazole-linked polymer membranes for superior H2 purification

Hydrogen (H₂) purification requires separation membranes with excellent performance and high stability. Here, a few nanometer-sized Zr-oxygen clusters (CP-2) abundant in amino groups were incorporated in benzimidazole-linked polymers (BILPs) by interfacial polymerization (IP) to fabricate molecular-scale hybrid membranes for efficient H₂/CO₂ separation. The amino groups in CP-2 engage in IP. The structure of the BILPs polymer chains is regulated and more H₂ selective channels are created. The hybrid membranes provide an H₂/CO₂ selectivity of up to 75.2 (with a corresponding H₂ permeance of 318 GPU) and a high H₂ permeance of up to 1470 GPU (with a corresponding H₂/CO₂ selectivity of 23.6). In addition, the membranes exhibit satisfactory separation performance and durability under industry-relevant conditions (573 K, 11 bar, or steam treatment).     

基于二维纳米材料的水处理功能膜研究进展

二维纳米材料是制备膜材料中一类重要的掺杂材料或膜构筑单元,也是新型水处理功能膜的研究热点。已有许多研究报道了二维纳米材料通过有序的堆叠和自组装在膜内构建出规整的水通道,可以赋予膜可调控的分离性能,进而实现trade-off效应的突破,被认为是“下一代膜材料”（next-generation membranes）。同时,二维纳米材料的独特片层结构、催化性能及可修饰性可使膜材料获得新的功能,如导电性能、光/电催化性能等。本文综述了近年来基于二维纳米材料的水处理功能膜研究进展,重点介绍了共混法、自组装等制备方法,并总结了此类功能膜在抗污染、膜通量恢复、强化污染物去除、调控盐截留及污染物监测领域的应用。最后对基于二维纳米材料的水处理功能膜发展方向,如限域催化、调控盐分离、监测传感等新兴领域进行了分析和展望。     

Enhanced antipressure ability through graphene oxide membrane by intercalating g-C3N4 nanosheets for water purification

Graphene oxide (GO) membranes have shown great potential for water purification, but their permeability and antipressure ability are poor, which limits their practical applications. In this study, two-dimensional graphitic carbon nitride (g-C₃N₄) nanosheet-intercalated GO (GOCN) membranes were developed to improve the separation performance of GO membranes, especially under high operating pressure. After incorporation of the g-C₃N₄ nanosheets, the amount of permeable nanochannels (wrinkles or corrugation) in the membrane increased; hence, the water permeance was effectively improved (twice as high as that of GO membranes). Moreover, the antipressure performance of the GOCN membranes was significantly enhanced (even below 0.5 MPa pressure) as the nanochannels in the composite membranes become stable and rigid due to the support of the pressure-resistant g-C₃N₄ nanosheets. The good separation performance demonstrates that the intercalation of g-C₃N₄ is an effective strategy to improve the GO-based membrane properties, which can promote their application in water purification.     

芬兰水管理和废水净化

介绍了芬兰水专项计划产生的背景,芬兰水资源管理和废水净化受到芬兰政府支持和机构间多方合作。详细阐述了芬兰水资源保护和废水处理的各种实施方案,希望对我国水管理及废水处理能有所借鉴。     

某南水北调水源水厂净水工艺设计

某城区供水采用南水北调中线水源。根据该城区现状,以及进水水质条件和出水水质要求,经技术经济比较确定了预氧化-常规处理-预留深度处理的工艺方案。工程运行结果表明,出水水质完全符合GB 5749—2006《生活饮用水卫生标准》的要求。     

多孔陶瓷膜用于碳量子点的分离与纯化

尺寸分布均一的碳量子点由于其良好的光学特性,在光电设备、离子检测、纳米传感器、生物成像和催化剂等领域具有广阔的应用前景。采用陶瓷膜“超滤-纳滤”双膜法,对微波合成的碳量子点进行分离和纯化。研究了pH对碳量子点料液荧光强度和粒径分布的影响。在pH=3时,碳量子点分散较好,荧光强度较高。陶瓷超滤膜可以有效截留碳量子点料液中的大颗粒杂质,渗透侧的碳量子点平均粒径约为2 nm,分散良好,无团聚现象。陶瓷纳滤膜对碳量子点具有良好的截留性能,在浓缩和水洗过程中可以进一步去除料液中的小分子杂质。经双膜法处理后,发射光谱由多峰分布变为单峰分布,且峰宽变窄,碳量子点的发光纯度得到了明显提高。     

自来水深度处理超滤膜的选择

试验设计、运行了聚砜中空纤维超滤(UF)膜,直接将未经预处理的某自来水管网输出水,处理成优质供水。结果表明,随着UF膜的切割分子量从0.6万增大到5万,产水量提高,对主要水质指标的去除率下降,净化水的水质优良,即使原水的水质突然恶化,UF膜能有效地将被严重污染的高浊度和色度的异常自来水转化成为符合饮用水水质指标的卫生洁净水。     

Halloysite nanotube-based superhydrophobic foam for highly efficient oil/water separation

Oil/water separation is a worldwide concern because of the emissions of oil contaminated wastewater and increasing number of oil spill accidents in recent years. Materials with superhydrophobicity and superoleophilicity provide a new strategy to solve such problems, which allow organic solvents to pass through freely while repelling water. Herein, the porous foams with superhydrophobicity and superoleophilicity were prepared successfully through a facile low-temperature sintering method, in which the halloysite nanotubes (HNTs), polyvinylidene fluoride (PVDF) and sodium chloride were used as the raw materials. Among them, HNTs constructed the rough surface in micro-/nano-scale and sodium chloride served as the sacrifice template. The superhydrophobic surface was achieved via the synergistic effect between the rough surface and PVDF with the low surface energy. The foam showed good water repellency (water contact angle, CA: 156.0 ± 0.1°) and superoleophilic properties, which could selectively absorb organic solvents from the mixture solution with water. Moreover, the foam exhibited high separation efficiencies for a variety of oil/water mixed solutions with excellent cycling stability, which make it a promising material for practical oil/water separation.     

Interlayer-confined two-dimensional manganese oxide-carbon nanotube catalytic ozonation membrane for efficient water purification

Catalytic ozonation technology has attracted copious attention in water purification owing to its favorable oxidative degradation of pollutants and mitigation of membrane fouling capacity. However, its extensive industrial application has been restricted by the low ozone utilization and limited mass transfer of the short-lived radical species. Interlayer space-confined catalysis has been theoretically proven to be a viable strategy for achieving high catalytic efficiency. Here, a two-dimensional MnO₂-incorporated ceramic membrane with tunable interspacing, which was obtained via the intercalation of a carbon nanotube, was designed as a catalytic ozonation membrane reactor for degrading methylene blue. Benefiting from the abundant catalytic active sites on the surface of two-dimensional MnO₂ as well as the ultralow mass transfer resistance of fluids due to the nanolayer confinement, an excellent mineralization effect, i.e., 1.2 mg O_3(aq) mg^–1 TOC removal (a total organic carbon removal rate of 71.5%), was achieved within a hydraulic retention time of 0.045 s of pollutant degradation. Further, the effects of hydraulic retention time and interlayer spacing on methylene blue removal were investigated. Moreover, the mechanism of the catalytic ozonation employing catalytic ozonation membrane was proposed based on the contribution of the Mn(III/IV) redox pair to electron transfer to generate the reactive oxygen species. This innovative two-dimensional confinement catalytic ozonation membrane could act as a nanoreactor and separator to efficiently oxidize organic pollutants and enhance the control of membrane fouling during water purification.     

电去离子净水技术的新进展

综合介绍了美国Ｉｏｎｐｕｒｅ＾ＴＭ加拿大Ｅ－Ｃｅｌｌ＾ＴＭ这两种电去离子净水装置的性能及应用,并讨论了我国在研究离子交换树脂电再生技术及开发电去离子净水产品方面的进展。从技术水平、市场开发前景和我国其他诸多因素的实际情况出发,建议优先开发作者依据ＥＤＩ中自再生原理发明的离子交换树脂的电再生技术。     

基于多巴胺亲水改性下Janus膜的制备及其油水乳液分离

目前用于处理含油废水的特殊润湿材料通常分为去油型和去水型,其仅局限分离单一乳液。本文基于多巴胺改性的聚偏氟乙烯(PVDF)膜,通过交替浸渍工艺和无纺布剥离,制备了具有不对称润湿性的Janus膜。通过调整交替次数以及剥离无纺布,可分别获得超亲水/水下超疏油的表面以及超疏水/超亲油的底面,水/水下油接触角(CA)差异高达150°。基于Janus膜的非对称润湿性,仅通过切换跨膜方向,对表面活性剂稳定的水包油(O/W)和油包水(W/O)乳液渗透通量高达367L/(m²·h)和1729L/(m²·h),其中水包油渗透液化学需氧量(COD)符合石油化工排放标准,油包水渗透液中水含量小于80mg/L,实现了对O/W和W/O乳液的高效分离。此外,Janus膜在牛血清蛋白(BSA)溶液分离过程中表现出理想的防污性能和可重复使用性。     

Investigations on the use of different ceramic membranes for efficient oil-field produced water treatment

Efficient performance of the combination of treatment processes for oilfield produced water generated from oil tank dewatering was investigated in the study presented below. By-produced wastewater is generated in significant quantity during exploitation of crude oil and gas from onshore and offshore production operations. This wastewater, commonly referred to as “produced water”, has distinctive characteristics, due to their organic and inorganic compounds. However, these characteristics change from well to well. The treatment process investigated here consists of a pre-treatment step utilizing microfiltration (0.1 and 0.2 µm pore size filters) and/or a simulated batch dissolved air flotation (DAF), and a multistage post-treatment step utilizing cross-flow ultra- (0.05 µm pore size and 20 kDa molecular weight cut-off filters), and nanofiltration (1 and 0.75 kDa MWCO filters). Filters used were ceramic membranes. To determine the separation capability of the processes described, various parameters, such as trans-membrane pressure varying from 0.5 to 2 bar, cross-flow velocity in the range of 0.6 to 1.3 m/s, influent oil concentration ranging from 32 to 5420 parts per million (ppm) and different membrane cleaning methods used were investigated. The average permeate flux varied from 3.4 to 3300 l/h m² bar, total oil removal was up to 99.5% and total organic carbon removal reached 49%.     

Addressing water scarcity: cationic polyelectrolytes in water treatment and purification

Synthetic cationic polyelectrolytes (CPEs) serve as coagulation and flocculation agents in wastewater treatment due to a synergy of inherent electrostatic interactions and hydrophilic properties. In wastewater treatment, CPEs act as coagulation and flocculation agents to aggregate impurities and enable water purification. New health and environmental‐related regulations provide motivation for government agencies and industrial companies to reuse wastewater. Chemical structure, molecular weight, charge density and functionality of CPEs provide tailorability for specific purification needs. Cationic polyacrylamides, ammonium‐based polymers, poly(allyldimethyl‐ammonium chloride) and epichlorohydrin/dimethylamine‐based polymers are the most common CPEs used as coagulation and flocculation agents because they are economical and water soluble with tunable charge densities at high molecular weights. Free radical polymerization, step‐growth polymerization and post‐polymerization modification methods afford each polymer system. This review highlights recent advancements in synthetic methods to yield CPEs, structure?property relationships as related to flocculation efficiency and a summary of their toxicity and environmental impact. © 2018 Society of Chemical Industry     

Thermodynamic and kinetic study of fluorinated gas hydrates for water purification

This study investigated and compared the thermodynamic stability, kinetic behaviour, and effectiveness of a water purification process using pentafluoroethane (HFC125a) and 1,1,1,2-tetrafluoroethane (HFC134a) as guest molecules. The hydrate phase equilibria of each fluorinated gas (F-gas) in pure water and NaCl solution were predicted using the Hu-Lee-Sum correlation, which agreed well with the experimental results from our previous studies. Under the same subcooling temperature of 3 K (at 0.3 MPa), the rate of hydrate growth with HFC134a was faster than that of HFC125a in the absence or presence of NaCl. In situ Raman spectroscopy confirmed that the HFC134a and HFC125a molecules occupy only a large cage of structure II hydrate. The Raman shifts of C H and C C bands in all phases (gas, liquid, and hydrate phases) of HFC125a shifted to higher wavelengths than those of HFC134a due to the increase in the number of fluorine atoms. The change in the salinity was studied to evaluate the effectiveness of an F-gas hydrate-based water purification process. In addition, the desalination efficiency of the HFC134a and HFC125a hydrates was compared by separating hydrate crystals from the slurries. The results showed that the desalination efficiency (or total dissolved solids removal efficiency) of HFC134a hydrate was higher than that of HFC125a hydrate. This study proves the importance of the water purification process using hydrates.     

硫铁矿制酸水洗净化工艺实现污水零排放的技改

介绍硫铁矿制酸污水循环利用的改造情况以及对改造中出现问题的整改措施。改造利用了公司邻近合成氨厂的废氨水对污水进行中和处理,既解决了公司污水处理问题,又解决了邻近合成氨厂外排废氨水的问题。技改后,水循环利用率达95%。