During the past 20 years, membrane technology industry has achieved great development both in China and abroad, meanwhile, membrane technology plays an important role in solving water security problem. In this article, the development of membrane separation technology and its applications in deep treatment of drinking water, wastewater treatment, emergency water supplies and special wastewater treatment were summarized.
This review first presents the main two structures in cell membrane—the lipid bilayer and membrane proteins and the mechanism of the ultrafast water transportation .It then describles the three types of biomimetic membranes that apply membrane protein，carbon nanotubes (CNTs) and artificial channels as water channel respectively. At the part of the membrane protein，the advantages of amphiphilic block copolymer using as supporting matrix and the problem faced in large-scale production of defectless membrane have been introduce；the second part is mainly about the mechanism of ultrafast water transportation in CNTs and the fabrication method of the hybrid membrane；at the part of artificial channels what really important is the design method. The review concludes with a discussion on the fundamental and practical challenges and a future outlook on the application of biomimetic membrane for desalination.
Herein, we report a new concept, constricted interfacial polymerization to study the formation of polyamide thin film composite membranes. Delayed diffusion of protected polyfunctional amine reacts with acyl chloride to produce a transition surface structure. Hydrophilic macromolecules and amphiphilic template induced interfacial polymerization reacted in a limited zone, the aggregation state of polymer chains transform from a random state to a regular stateand membrane permeability increases without a loss of salt rejection. Zeolite nanoparticles dispersed in RO composite membrane changed film morphology and water permeability is increased nearly 50% with equivalent salt rejection.
Graphene oxide provides an ideal substrate for lysozyme immobilization due to a large specific surface area and abundant functional groups. The lysozyme immobilization on the GO sheets could take place readily by electrostatic interaction of GO-lysozyme (denoted as GO-Ly). The immobilized lysozyme of GO used as the addictive was blended with PES to prepare hybrid ultrafiltration membrane via phase inversion.The effect of GO-Ly content on the morphology, hydrophilic, separation, mechanical and antibacterial properties of hybrid membranes was investigated. The results showed that the surface hydrophilicity and water flux was significantly improved with the increase of GO-Ly content. Meanwhile, the mechanical strength of hybrid membrane was also increased. Especially for 1.5 wt.% of GO-Ly, the water flux reached up to 318 L/(m2?h). The rejection of PVA30000-70000 was 99% and the antibacterial rate of the hybrid membrane against E. coli could achieve 68%.
Anti-fouling membrane is an important research subject of reverse osmosis (RO) and the key to RO membrane application. In this paper, classification and influence factors of RO membrane-fouling are reviewed. Attention is focused on methods to improve anti-fouling property of RO membrane, including design of key monomer, physical surface modification, chemical modification, and blending modification. Prospect of anti-fouling RO membrane is made as well.
The removal of trace phthalic acid esters (PAEs) in water used DK nanofiltration membrane has been investigated. The adsorption behavior and rejection characteristics of dimethyl phthalate (DMP)、 diethyl phthalate (DEP)、di-n-butyl phthalate (DnBP) and di-iso-butyl phthalate (DiBP) were also explored. It was found that adsorption isotherms of PAEs in DK nanofiltration membrane fit the Freundlich adsorption equation well. The rejection characteristics of PAEs involved in the retention of adsorption and the retention of membrane pore before adsorption reaches saturation. After adsorption reaches saturation, the rejection mechanisms of PAEs could be described pore model,and rejection rate (R) of DMP、DEP、DnBP and DiBP were 55.1%、78%、96%、96.8% (0.5MPa,30℃,PAEs concentration 300μg/L), respectively. The results indicated that the trace DnBP 、DiBP in water could been rejected very effectively by DK nanofiltration membrane.
The salt in the wastewater of the cephalexin enzymatic process was removed by electrodialysis. The influence of operating voltage, velocity ratio and temperature on the desalination process were investigated. The change of the permeate flux in the reverse osmosis separation process was also studied. The results showed that the electrodialysis process performed better in desalination with the organic matter retention rate reaching 99.50%, the energy consumption of 3.65KWh/kg at the conditions of the velocity ratio of 1:1, the operating voltage of 25V and temperature <30℃. During the reverse osmosis separation process, the decay of permeate flux was slow and acceptable, and the the water recovery rate was 75.67%. All results showed that it was feasible to treatment the waste water of the cephalexin enzymatic process by a combined process of electrodialysis and reverse osmosis.
In this paper, the basic principle of computational fluid dynamics (CFD) in membrane separation process were introduced, and the application of CFD mechanism of membrane pollution, membrane module design in pressure-driven membrane processes, as well as other membrane process, such as pervaporation, membrane distillation were presented. The prospect of application of CFD in membrane process was discussed.
This study focused on preparing drinking water from the tidal salty water of Qiantang River by nanofiltration technology. Some commercial nanofiltration membranes were compared and the performance of optimized membrane was measured. A nanofiltration pilot-scale system with 500 m3/d was operated and optimized. The results showed that it was effective in removing the salt and reducing the organic pollutants from tidal water for nanofiltration technology, and nanofiltration could play an important role of security for drinking water.
The nonporous homogeneous cellulose membrane for forward osmosis was prepared via phase inversion method using ionic liquid 1-ethyl-3-methyl-imidazolium acetate (EMIMAc) as solvent, water as nonsolvent on a non-woven fabric substrate. The characterizations of Fourier transform infrared (FTIR) and X-ray diffraction (XRD) spectroscopies showed that no obvious change occurred in the chemical structure of cellulose after membrane formation, but the crystallinity had a certain degree of decline. The cross-section and the surface morphologies of the cellulose forward osmosis membrane were analyzed by scanning electron microscopy (SEM). The membrane performance were investigated by measuring water flux and rejection of simulated seawater. The water flux of the cellulose forward osmosis membrane, which the cellulose concentration is 8 %(wt) in casting solution, was 3.534 L/m2.h and the rejection for NaCl was more than 99 %, using 0.6 mol/L NaCl solution as the feed solution and lab-made nutrient solution as the draw solution.
Study on the feasibility of EDI device, whose dilute departments were filled with cation exchange resins and feed water was low concentration Ni2 solution, for the treatment of low-concentration heavy-metal wastewater. The effects of operating voltage and dilute flow flux on the separation performances EDI processes were investigated. With the feed solution whose Ni2+ concentration was 50 mg·L-1 and pH was 4.5, the results show that the out dilute Ni2+concentration was lower than 2 mg·L-1 and the Ni2+ concentration of out concentrate could higher than 900 mg·L-1 when operating voltage was 25 v and dilute flow flux was 20 L·h-1.
In this paper, the composite membrane of polydimethylsiloxane(PDMS)/polyvinylidene fluoride (PVDF) is prepared by cross-linking reaction of PDMS and triethoxyvinylsilane on PVDF hollow fiber membrane surface.Themembranesare characterized with scanning electronmicroscopyandattenuated total reflection Fourier transform infrared spectrum.Thepervaporation performance is investigated by separation of three simulate saline organic wastewaters, n-butanol-water, isopropanol-water and acetone-water, the effect of temperature on membrane separation performance is also determined. The results show that the membranes have good performance for separation of three saline organic wastewaters, when the operating temperature is 40 oC, the membranes exhibit the permeate flux of 275.95 g/m2·h,322.16 g/m2·h,489.76 g/m2·h, and separation factor is 37.82,12.60,33.12, respectively.
In this paper some characteristics of uranium in aqueous solution and its harmness were briefly introduced. The research progress in recent years on adsorption technologies in treatment wastewater with low concentration of uranium was summarized, and the features of every adsorption technologies were analyzed. The performance and industrial application prospect of these adsorption technologies were remarked, and some opinions about the further study aspects were given.
PVP/EVAL blend membranes was prepared by blending of PVP with poly(ethylene-co-vinyl alcohol) (EVAL) via immersion precipitation and were used to separate the oil/water emulsion. The chemical structure, morphology, mechanical performance and hydrophilicity of PVP/EVAL blend membranes were characterized by FTIR-ATR, scanning electron microscopy, tension test and water contact angle measurement. The effect of PVP content on the separation performance of oil/water emulsion was investigated. The results indicate that PVP content had distinct effect on the morphology of PVP/EVAL membranes. The tensile strength and elongation at break of PVP/EVAL blend membrane with 10 wt% (the mass percent of PVP in the casting solution) PVP were 1.88 and 1.34 times, respectively, that of pure EVAL membrane. When the content of PVP increased to 4 wt%, oil/water emulsion flux of PVP/EVAL blend membrane were 1.81 times that of the pure EVAL membrane. The rejection ratio was 92.2 %, slightly higher than the pure EVAL membranes. When the content of PVP increased to 10 wt%, the flux recovery ratio after washing increased from 51 % to 77.98 %.
Grephene oxide (GO) mixed matrix reverse osmosis (RO) membranes were prepared with metaphenylenediamine(MPD) and trimesoyl chloride (TMC) by interfacial polymerization. Themorphology of the membraneswere characterized by scanning electron microscopy(SEM). The separation performance and chlorine resistance were also investigated.The results shown that owing to the hydrophilicity of GO, the membranes appeared to be more hydrophilic and had higher pure water fluxes than the bared polyamide RO membrane,only with a slight change of rejection. When the content of GO added in the aqueous phase was 0.005wt%, the flux of the membrane increased by 20%. The mixed matrix RO membrane of polyamide and GO shownbetterchlorine resistance than PA RO membrane.
Reverse osmosis technology plays an important role in desalination industry. However, regular reverse osmosis (polyamide) membrane will be damaged by active chlorine in feed then fail in separation performance. Here the chlorination mechanism of reverse osmosis polyamide membrane is briefly illustrated and the progress in new chlorine-resistant membrane materials is reviewed.
As a novel method of separation,micellar enhanced ultrafiltration is applicable to purifying wastewater,especially in dealing with the effluents containing low levels of metal ions. The main factors of MEUF are introduced in detail by summarizing prior research,and the limitation and the direction of optimizing the process are also discussed. The recent development of MEUF as well as the research on surfactants recovery is also introduced.
Heavy metal wastewater is becoming one of the most serious environmental problems today, a variety of technologies have been used to treat heavy metal wastewater. In this paper, the frequently-used treatment methods, which include chemical precipitation, coagulation-flocculation, electrochemical methods, membrane separation, ion-exchange and adsorption, were introduced, and their advantages and disadvantages were summarized.
As to the increasing severe water pollution, developing an effective strategy for advanced potable water treatment is one of the urgent livelihood issues. Membrane technology of water treatment is highly focused and studied to guarantee the security of drinking water due to its high efficiency and low consumption. In this paper, a detailed review was drawn on the application of different membrane processes in the advanced water treatment, based on the features of these pressure-driven membrane processes and the quality of different water resource, Finally, several suggestions were listed for the development of membrane-based potable water treatment.