High performance polyethersulfone UF membrane for manufacturing spiral wound module: preparation,morphology, performance,and chemical cleaning

Large sheet asymmetric polyethersulfone (PES) ultrafiltration membranes were prepared via phase inversion process in a continuous conveyor system with addition of PVP to the casting solution. Dimethylacetamide (DMAc) and mixture of water and isopropyl alcohol (70/30 v%) were used as solvent and non‐solvent respectively. The prepared membrane was 0.96 m wide and 3 m long. The pieces of the membrane were selected randomly for characterization in terms of performance using cross flow filtration for milk concentration, image analysis, scanning electron microscopy (SEM), and cleaning procedures. It was found that the prepared membrane has high porosity and high water flux during milk filtration. In addition, cleaning experiments indicated that NaOH/HCl/NaOH sequence is an effective procedure for cleaning the fouled membrane during milk concentration. Copyright © 2007 John Wiley & Sons, Ltd.     

Spectrophotometric study of the alkali metal-murexide complexes in some non-aqueous solutions

The complexes of murexide with alkali-metal cations have been studied spectrophotometrically in methanol, dimethylformamide and dimethylsulphoxide media at 25 degrees . The stoichiometry of the complexes was found to be 1:1. The formation constants of the complexes were determined, and found to decrease in the order Na(+) > K(+) > Rb(+) approximately Li(+) for all solvents studied. The complex formation constants varied inversely with the Gutmann donicity of the solvents.     

Kinetic Study of Mercury(II) Transport through a Bulk Liquid Membrane Using Cyanex 301 as Carrier

A kinetic study of Hg(II) ions transport through a bulk liquid membrane (BLM) was investigated. The commercially available liquid bis(2,4,4‐trimethyl(pentyl) dithiophosphinic acid) (Cyanex 301) was employed as mobile carrier. The influences of the carrier concentration in the liquid membrane, HNO₃ concentration in the feed phase, type of organic solvent, composition of the receiving phase, and stirring speed on mass transfer were studied. Various solvents including CH₂Cl₂, CHCl₃, C₂H₄Cl₂ and CCl₄ were used as organic membrane. Among the solvents, CHCl₃ provided the superior results. The kinetic parameters (k₁, k₂, R_m^max, t^max, J_d^max, and J_a^max) were calculated for the interface reaction assuming two consecutive, irreversible first‐order reactions. The analysis of Hg(II) accumulation in liquid membrane and the rate‐controlling step under different experimental conditions were elucidated. The experiments demonstrated that Cyanex 301 is an appropriate carrier for Hg(II) transport through liquid membrane.     

PREPARATION OF POLYETHERSULFONE ULTRAFILTRATION MEMBRANES FOR MILK CONCENTRATION AND EFFECTS OF ADDITIVES ON THEIR MORPHOLOGY AND PERFORMANCE

Polyethersulfone membranes were prepared from quaternary systems containing N,N-dimethylacetamide （DMAc） as solvent, polyvinylpyrrolidone （PVP） as constant additive and acetic acid, acetone and water as variable additives. Phase inversion via immersion precipitation was employed for manufacturing of membranes. The prepared films were immersed in the mixture of pure water and 2-propanol （30/70 vol%） as the non-solvent. Acetic acid caused an increment in the flux at high polymer concentration （16 wt%） and a decline in the flux at low polymer concentrations （10 wt% and 13 wt%）. Acetone and water as the solvent in the casting solution declined the flux at any polymer concentration tested. The morphology and performance of the prepared membranes were investigated by scanning electron microscopy and separation experiments using milk as the feed.     

Ultrafiltration of Humic Substances in the Presence of Protein and Metal Ions

In this paper factors affecting the ultrafiltration of mixtures of HA and BSA including concentration, pH, ionic strength, ionic charge and size of hydrated ion were elucidated. In the presence of BSA, higher HA rejection and lower flux were obtained during ultrafiltration. This is due to interactions between HA and BSA. A bond may be established between humic acid and protein molecules. Flux was decreased and HA rejection was increased with increasing the humic acid concentration in constant concentration of BSA. At low concentration, the humic macromolecules pass more easily through the membrane pores due to their structure. The HA rejection depends on the molecular weight cut off (MWCO) of the membrane. Higher rejection is anticipated for membranes with lower MWCO. However cake deposition is the dominant mechanism during ultrafiltration of solutions containing mixtures of HA and BSA using XM50, YM100 and XM300 ultrafiltration membranes. By increasing the pH of solutions containing mixture of HA and BSA, higher flux and lower HA rejection were achieved. At the protein isoelectric point, flux showed a minimum and increased for higher pH values. A higher flux was obtained for solutions with lower ionic strength. At the beginning of the filtration, HA rejection was low for solution with higher ionic strength. However during filtration the trend was conversely changed. In the presence of Ba²⁺ cation the HA rejection for solutions containing HA and BSA was higher compare to the solutions containing Na⁺ cation.     

Preparation and characterization of metallic membrane using wire arc spraying

Metallic membranes can be prepared by various techniques. This work introduces a novel method for the preparation of metallic membranes using wire arc spraying. The formed metallic membranes were characterized by metallographic techniques such as microscopy image analysis. The distance between gun and the substrate surface, which is called spray distance or gun distance, was selected as the variable of metal spraying. The effects of gun distance on coating properties and membrane performance were investigated. The metallographic and performance data showed that the range of 35–40 cm is the optimum gun distance for spraying. Ion rejection capability of the prepared membrane was tested using saline water as the feed. Moreover the filtration capability of the prepared membranes for blue indigo dye particles was investigated. Energy dispersive X-ray (EDX) analysis and SEM technique were used for the investigation of filtration mechanism. The results indicate that the prepared stainless steel membrane is able to efficiently remove particles from water.     

Ionic behavior modification of cation exchange ED membranes by using CMC-co-Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles for heavy metals removal from water

A new mixed matrix polyvinyl chloride-based heterogeneous cation exchange membrane was prepared by incorporation of carboxy methyl cellulose-co-Fe₃O₄ nanoparticles through solution casting technique. The effect of simultaneous using of carboxy methyl cellulose and iron oxide nanoparticles in the casting solution on the physicochemical properties of membranes was studied. SOM images showed uniform particles distribution and uniform surfaces for the membranes relatively. The SEM images exhibited regular direction/spatial orientation for the CMC-co-Fe₃O₄ nanoparticles in the membrane matrix. XRD patterns showed that membrane heterogeneity was enhanced by using of Fe₃O₄ nanoparticles. Membrane ion exchange capacity, membrane surface hydrophilicity, membrane potential, surface charge density, transport number, selectivity, and ionic flux were increased by using CMC/Fe₃O₄ nanoparticles in membrane matrix. Results showed that membrane areal electrical resistance was declined up to 3.8 Ω cm² by utilizing CMC/Fe₃O₄ nanoparticles in the casting solution. Also PVC/CMC-co-Fe₃O₄ membrane showed higher transport number, selectivity, flux, and electrical conductivity compared to PVC/CMC membrane and unmodified ones. Electrodialysis experiment in laboratory scale showed higher dialytic rate in lead ions removal for PVC/CMC-co-Fe₃O₄ nanoparticle-mixed matrix ion exchange membrane compared to PVC/CMC membrane and pristine one.     

Characterization of Zinc Ion Transport Via Dialysis Process

Treatment of metal ions' wastes is getting more interest due to the tight regulations for environmental protection. Dialysis, a membrane based process with the concentration difference as the driving force, may be used for separation of metal ions from wastewater. In this study membranes with different pore sizes including Accurel, Celgard, GVHP, PM30 and PTHK membranes were employed to characterise the transport of zinc ion in various (0.01, 0.1, 0.5, 1, 5 and 10 w/v percent) initial feed concentrations. The results show that low initial feed concentration causes less passage of ions through the membrane due to low driving force, i.e. concentration gradient across the membrane. This result is expected. However the effect of membrane pore size is somehow unexpected. It was found that the large pore size membranes provide less penetration of the metal ions through the membrane. This reproducible result has been explained based on the transport mechanism. Two types of mechanisms, i.e. extensive and intensive mechanisms, have been suggested for metal ion transport through different pore size membranes.     

Effect of type of solvent and non‐solvents on morphology and performance of polysulfone and polyethersulfone ultrafiltration membranes for milk concentration

Polysulfone (PS) and polyethersulfone (PES) ultrafiltration membranes were manufactured from a casting solution of the polymer, polyvinylpyrrolidone (PVP) in various solvents [N,N‐dimethylacetamide (DMAc), N,N‐dimethylformamide (DMF) and 1‐methyl‐2‐pyrrolidone (NMP)] by immersing the prepared films in different non‐solvents [water, 2‐butanol, mixture of water and 2‐butanol, mixture of water and 2‐propanol (IPA) and mixture of water and 1‐butanol]. The influences of various solvents and non‐solvents on morphology and performance of the prepared membranes were analyzed by scanning electron microscopy (SEM) and separation experiments using milk as the feed. Copyright © 2005 John Wiley & Sons, Ltd.     

The effect of heat treatment of PES and PVDF ultrafiltration membranes on morphology and performance for milk filtration

The flat sheet polyethersulfone (PES) and poly(vinylidene fluoride) (PVDF) membranes were prepared by immersion precipitation technique. The influence of hot air and water treatment on morphology and performance of membranes were investigated. The membranes were characterized by AFM, SEM, cross-flow filtration of milk and fouling analysis. The PES membrane turns to a denser structure with thick skin layer by air treatment at various temperatures during different times. This diminishes the pure water flux (PWF). However the milk permeation flux (MPF) was considerably improved at 100 °C air treatment for 20 min with no change in protein rejection. The smooth surface and slight decrease in surface pore size for air treated PES membrane at 100 °C compared to untreated membrane may cause this behavior for the membrane. The water treatment of PES membranes at 55 and 75 °C declines the PWF and MPF and increases the protein rejection. This is due to slight decrease in membrane surface pore size. The treatment of PES membrane with water at higher temperature results in a porous structure with superior performance. The fouling analysis of 20 min treated membrane indicates that the surface properties of 100 °C air treated and 95 °C water treated PES membranes are improved compared to untreated membrane. The SEM observation depicts that the morphology of air and water treated PVDF membranes was denser and smoother with increasing the heat treatment temperature. The 20 min air treated PVDF membranes at 100 °C and water treated at 95 °C exhibited the highest performance and antifouling properties.