Influence of chemical speciation on the separation of metal ions from chelating agents by nanofiltration membranes

The simultaneous separation of various metal ions (nickel, copper, calcium, and iron) from chelating agents (EDTA and citric acid in water streams using Nanofiltration membranes is analyzed. Assuming that multiply-charged species are highly rejected, chemical speciation com-10 putations reproduce the observed patterns of metal and ligand rejection at different pH values and concentrations.Postprint (updated version

Dairy waste water treatment by combining ozonation and nanofiltration

The aim of this investigation was to examine the applicability of the membrane technique and the effect of preozonation in dairy waste water treatment technology. The best degree of surfactant removal from model anionic surfactant solution by nanofiltration was achieved at 20 degrees C and 40 bar. Investigations on the effects of ozone treatment of the waste water indicated that preozonation decreased the flux and increased the chemical oxygen demand and surfactant removal efficiency. Ozone treatment enhanced the biodegradability of the retentate from 68.8% to 96.4%

Trace ions rejection tunning in NF by selecting solution composition: Ion permeances estimation

Nanofiltration (NF) is suggested to selectively remove ionic species in aqueous process streams taking benefit of both membrane and aqueous solution composition. The importance of predicting and optimizing selective ion rejections by NF not only of major compounds (e.g. NaCl, Na2SO4, MgCl2, MgSO4) but also of minor ones such as ammonium (NH4+), nitrate (NO3-), bromide (Br-), iodide (I-) typically present in natural and industrial process streams is crucial. The current work explores ion rejection patterns and membrane ion permeances using the phenomenological Solution-Electro-Diffusion-Film (SEDF) model. It makes possible rapid calculations that account for the effects of spontaneously arising electric fields on rejections. Experimental ion rejection data of several inorganic ions species at various transmembrane pressures and at fixed cross-flow velocity have been obtained with NF270 membrane. A number of trace ions (Na+, K+, Cl-, Ca2+, Mg2+, SO42-, NO3-, NH4+, Br-and I-) have been used in combination with various dominant salts (NaCl, MgCl2, MgSO4) as model feed solutions. Results showed that dominant salts were moderately (NaCl) and highly (MgCl2, MgSO4) rejected when some ions are divalent, while trace ions exhibited quite variable rejection, including negative ones mainly at low transmembrane volume flows. The electric field of membrane potential can accelerate or retard the ion flows to the permeate, so negative or unexpectedly high rejections could be observed. Ions transport was shown to be affected by the membrane chemistry (e.g. acid-base properties of the un-crosslinked carboxylic and amine groups) and the dielectric exclusion phenomena. From the modelling procedure, ionic membrane permeances were determined for various multi-ion systems studied. Results showed that nature of dominant salt composition can be used to control the rejection of minor components.Peer ReviewedPostprint (author's final draft

Cyclophosphamide removal from water by nanofiltration and reverse osmosis membrane

The rejection of cyclophosphamide (CP) by nanofiltration (NF) and reverse osmosis (RO) membranes from ultrapure (Milli-Q) water and membrane bioreactor (MBR) effluent was investigated. Lyophilization–extraction and detection methods were first developed for CP analysis in different water matrices. Experimental results showed that the RO membrane provided excellent rejection (>90%) under all operating conditions. Conversely, efficiency of CP rejection by NF membrane was poor: in the range of 20–40% from Milli-Q water and around 60% from MBR effluent. Trans-membrane pressure, initial CP concentration and ionic strength of the feed solution had almost no effect on CP retention by NF. On the other hand, the water matrix proved to have a great influence: CP rejection rate by NF was clearly enhanced when MBR effluent was used as the background solution. Membrane fouling and interactions between the CP and water matrix appeared to contribute to the higher rejection of CP

Direct nanofiltration of wastewater treatment plant effluent

Membrane technology, especially nanofiltration, is seen as a suitable technology to polish WWTP effluent to EU WFD standards and consequently produce an effluent quality suitable for agricultural or (in)direct potable usage. The objective of this study was to assess the potential of direct nanofiltration as technique for effluent reclamation

Polyaniline membranes for use in organic solvent nanofiltration

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Dichloroaniline retention by nanofiltration membranes

This study evaluates the performance of two nanofiltration membranes in removing a herbicide: dichloroaniline. The membranes, one polyamide and one cellulose acetate, have a cut-off in the range 150–300 g/mol (manufacturers’ data). The experiments were carried out with solutions of dichloroaniline in demineralized water, with concentrations from 1 to 10 ppb. For each membrane, the amount of herbicide retained and adsorbed by the membrane was determined as a function of feed concentration and transmembrane pressure. The two membranes, made of different materials but having the same nominal cut-off, retained dichloroaniline to very different extents and by different mechanisms

Fenton coupled with nanofiltration for elimination of Bisphenol A

Bisphenol A (BPA) is a typical Endocrine Disrupting Chemical (EDC), which is potentially harmful during wastewater reclamation. In this study, its degradation during Fenton's process under different operational conditions was investigated in combination with subsequent nanofiltration of low concentration remnant BPA and compounds derived from oxidation. The results indicate that BPA could be degraded efficiently in aqueous phase by Fenton, even at very low hydrogen peroxide doses. The treatment of up to 300 mg/L solutions of BPA with Fenton liquor at optimal conditions resulted in its complete removal in less than 2 min. The optimal conditions were found to be pH, = 3, H2O2/BPA = 020 and Fe2+/BPA = 0.012. Five NF polymeric membranes having different properties were used for the nanofiltration of treated and non-treated solutions. The nanofiltration of BPA solutions showed that rejection is related to adsorption ability of BPA on the membrane and size exclusion mechanism. In the nanofiltration of the effluent after Fenton oxidation, high TOC, COD, colour and Fe2+ (>77%) removal were achieved, although significant membrane fouling was also observed. The normalised water flux after membrane flushing with water was lower than 60% in almost all used membranes, which indicates significant non-easily removable fouling. (C) 2014 Elsevier B.V. All rights reserved.Peer ReviewedPostprint (author’s final draft

UV-enhanced sacrificial layer stabilised graphene oxide hollow fibre membranes for nanofiltration

Graphene oxide (GO) membranes have demonstrated great potential in gas separation and liquid filtration. For upscale applications, GO membranes in a hollow fibre geometry are of particular interest due to the high-efficiency and easy-assembly features at module level. However, GO membranes were found unstable in dry state on ceramic hollow fibre substrates, mainly due to the drying-related shrinkage, which has limited the applications and post-treatments of GO membranes. We demonstrate here that GO hollow fibre membranes can be stabilised by using a porous poly(methyl methacrylate) (PMMA) sacrificial layer, which creates a space between the hollow fibre substrate and the GO membrane thus allowing stress-free shrinkage. Defect-free GO hollow fibre membrane was successfully determined and the membrane was stable in a long term (1200 hours) gas-tight stability test. Post-treatment of the GO membranes with UV light was also successfully accomplished in air, which induced the creation of controlled microstructural defects in the membrane and increased the roughness factor of the membrane surface. The permeability of the UV-treated GO membranes was greatly enhanced from 0.07 to 2.8 L m(−2) h(−1) bar(−1) for water, and 0.14 to 7.5 L m(−2) h(−1) bar(−1) for acetone, with an unchanged low molecular weight cut off (~250 Da)