- Email: [email protected]
Electrodialysis and nanofiltration of surface water
CALENDAR
Events Calendar 11–14 December 2003 3rd Conference of the International Water History Association Cairo, Egypt Contact: Alv Terje Fotland, Coordinator CDS, Strømgt. 54, N-5007 Bergen Norway Tel: +47 55 589315 Fax: +47 55 589892 Email: [email protected] Web: www.iwha.net
14–19 December 2003 Solid–Liquid Separation Systems IV Pucon, Chile Contact: Engineering Conferences International, 6 MetroTech Center, Brooklyn, New York, NY 11201, USA Tel: +1 718 260 3743 Fax: +1 718 260 3574 Email: [email protected] Web: www.engconfintl.org
26–30 January 2004 Membrane Technology Course Cranfield, UK Contact: Short Course Office, Cranfield University, Cranfield, Bedfordshire, MK43 0AL, UK Tel: +44 1234 754176 Fax: +44 1234 751206 Email: [email protected]
17–20 February 2003 SMAGUA Water Zaragoza, Spain Contact: Zaragoza Trade Fair Centre
Tel: +34 976 76 4700 Fax: +34 976 33 0649 Web: www.feriazaragoza.com
Web: www.desline.com or www.edsoc.com
4–5 March 2004
Advanced Membrane Technology II
Industrial Water Recovery and Reuse (IWRR) Short Course Cranfield, UK Contact: Short Course Office, Cranfield University, Cranfield, Bedfordshire, MK43 0AL, UK Tel: +44 1234 754176 Fax: +44 1234 751206 Email: [email protected]
19–23 April 2004
23–28 May 2004 Irsee, Germany Contact: Engineering Conferences International, 6 MetroTech Center, Brooklyn, NY 11201, USA Tel: +1 718 260 3743 Fax: +1 718 260 3754 Email: [email protected] Web: www.engconfintl.org/4aj.html
8–11 June 2004 Pharmintech 2004
New Orleans, Louisiana, USA Contact: Charlotte Stripling Administrative Manager, AFS Society PO Box 1530, Northport, AL 35476, USA Tel: +1 205 333 6111 Fax: +1 205 333 6446 Email: [email protected]
Bologna, Italy Contact: Maria Grazia Facchinetti Marketing & Communications Manager Ipack-Ima srl, Corso Sempione 4, 20154 Milan, Italy Tel: +39 02 319 1091 Fax: +39 02 336 19826 Email: [email protected] Web: www.pharmintech.com
3–6 May 2004
26–30 June 2004
9th World Filtration Congress
EuroMed 2004: Desalination Strategies in South Mediterranean Countries Agadir, Morocco Contact: Miriam Balaban, European Desalination Society, Science and Technology Park of Abruzzo, Via Antica Arischia 1, 67100 L'Aquila, Italy Tel: +39 862 3475 308 Fax: +39 862 3475 213 Email: [email protected] or [email protected]
Simultaneously, the use of rotating electrodes substantially lowers the response time at submicromolar activities. An eccentrically placed Pb 2+-selective membrane on a rotating disk electrode, with optimized internal solution, showed a lower detection limit of aPb = 6.3 × 10–11 M. T. Vigassy, R.E. Gyurcsányi, E. Pretsch: Electroanalysis 15(15–16) 1270–1275 (September 2003).
Treatment for indirect potable reuse of water Microfiltration (MF) followed by reverse osmosis (RO), and soil-aquifer treatment (SAT), are the two principal technologies considered for indirect potable reuse of wastewater. This study, conducted at the Northwest Water Reclamation Plant, based in Mesa Arizona, USA, evaluated MF/RO and SAT (residence time in excess of 6 months) treated tertiary effluent with respect to organics removal. Effluent organic matter was characterized as total organic carbon (TOC), by UV absorbance (UVA), solid-state carbon-13 nuclear magnetic resonance spectroscopy, and size exclusion
Membrane Technology December 2003
Conference on Inorganic Membranes (ICIM8)
NAMS 2004 Honolulu, Hawaii Contact: Meeting Secretary, Ms Victoria Corrin, CERR, 5403 Boelter Hall, University of California, Los Angeles, CA 90095, USA Tel: +1 310 825 8798 Fax: +1 310 206 4107 Email: [email protected]
18–21 July 2004 The 8th International
chromatography. Several trace organic micropollutants, including ethylenediaminetetraacetate (EDTA), nitrilotriacetate (NTA), and alkylphenolethoxylate residues, were analyzed by gas chromatography/mass spectrometry (GC/MS). The study revealed that final TOC concentrations of MF/RO and SAT are 0.3 mg L–1 and 1.0 mg L–1, respectively. Based on the characterization techniques used, the character of bulk organics present in final SAT water resembles the character of natural organic matter present in drinking water. Depending on the molecular weight cut-off, RO membranes can efficiently reject high molecular weight organic matter (characterized as humic and fulvic acids). However, approximately 40–50% of the remaining TOC in permeates consists of low molecular weight acids and neutrals representing a molecular weight range of about 500 Da and less. In the SAT-treated effluent, EDTA and APECs were removed to approximately 4.3 µg L–1 and 0.54 µg L–1, respectively, but were below the detection limit in the MF/RO treated effluent. J.E. Drewes, M. Reinhard and P. Fox: Water Research 37(15) 3612–3621 (September 2003).
Cincinnati, Ohio, USA Contact: Gerri Burke, Department of Chemical and Materials Engineering University of Cincinnati, ML 171, Cincinnati, Ohio 45343, USA Tel: +1 513 556 6135 Fax: +1 513 556 1522 Email: [email protected]
28 September–1 October 2004 Euromembrane 2004 Hamburg, Germany Contact: c/o TUHH-Technologie GmbH (TuTech), Postfach 21079, Hamburg, Germany Tel: +49 40 766 1800 Fax: +49 40 7661 8018 Web: www.tutech.de/euromembrane
21–26 August 2005 International Congress on Membrane Processes – ICOM 2005 Seoul, Korea Contact: Prof. Young Moo Lee, National Research Laboratory for Membranes, School of Chemical Engineering, Hanyang University, Seungdong-ku, Seoul 133-791, Korea Tel: +82 2 2290 0525 Fax +82 2 2291 5982 Email: [email protected] Web: www.membrane.or.kr
Electrodialysis and nanofiltration of surface water In order to achieve stable groundwater levels, an equilibrium is needed between the use of groundwater for producing drinking water, and natural or artificial groundwater recharge by infiltration. Local governments usually require that the composition of the water used for artificial recharge is similar to the surface water that is naturally present in the specific recharge area. In this research, electrodialysis (ED) and nanofiltration were evaluated as possible treatment technologies for surface water from a canal in Flanders (in the North of Belgium), in view of infiltration at critical places on heathlands. Both methods were evaluated on the basis of a comparison between the water composition after treatment and the composition of local surface waters. The treatment generally involves ‘tuning’ the pH and the removal of contaminants originating from industrial and agricultural activity, for example, nitrates and pesticides. Further evaluation of the influence of the composition of the water on the characteristics of the artificial recharge, however, was not envisaged. In a case study of water from the canal Schoten-Dessel, satisfactory concentration reductions of Cl–, SO42–, NO3–, HCO3–,
15
RESEARCH TRENDS Na+, Mg2+, K+ and Ca2+ were obtained by ultrafiltration pretreatment followed by ED. Nanofiltration with UTC-20, N30F, Desal 51 HL, UTC-60 and Desal 5 DL membranes resulted in an insufficient removal level, especially for the monovalent ions. B. van der Bruggen, R. Milis, C. Vandecasteele, P. Bielen, E. Van San and K. Huysman: Water Research 37(16) 3867–3874 (September 2003).
Alumina and aluminate ultrafiltration membranes The fabrication of alumina ultrafiltration membranes using acetic acid surface stabilized alumina nanoparticles (A-alumoxanes) has been investigated. The pore size, pore-size distribution, and molecular weight cut-off (MWCO) parameters of the resulting membranes are highly dependent on the uniformity of the nanoparticle precursor, which is a function of the reaction time and reaction pH during their synthesis. By controlling the alumina nanoparticles, a significant improvement of the membrane performance is observed, compared with the authors’ previous results. The new alumoxane-derived membranes have a molecular weight cut-off in the range of less than 1000 g mol–1, and show good selectivity to a range of synthetic dyes. Further control over selectivity and flux of these ceramic membranes may be obtained by using doped alumina nanoparticles (Fe, Mn and La) that result in the formation of the appropriate aluminate membranes. Of these, LaAlO3 shows the most promising results. Retention coefficients and flux values also may be altered by the chemical functionalization of the interior surface of the membranes by reacting the alumina surface with carboxylic acids. K.A. DeFriend, M.R. Wiesner and A.R. Barron: J. of Membrane Science 224(1–2) 11–28 (15 October 2003).
Gas separation performance of Matrimid membranes At room temperature a chemical cross-linking modification was performed on Matrimid 5218, a material that has received pervasive attention in membrane separation. The cross-linking reaction was conducted by simply immersing the membrane in a p-xylenediamine solution at 16
ambient temperature for a stipulated period of time. The influence of cross-linking modification on thermal and gas transport properties of Matrimid membrane were studied. The gas permeability and selectivity of pure gases He, O2, N2, CH4 and CO2, as well as mixed gas of CO2/CH4 were measured. The gas permeabilities show their maximum values for one-day cross-linked membranes, but then decrease gradually with immersion time. It is found that the Matrimid membrane undergoes the plasticization phenomenon at 15 atm, however it is effectively suppressed by the proposed cross-linking modification. The ideal selectivities for O2/N2, CO2/CH4 and CO2/N2 remain almost constant and decreased slightly with the cross-linking reaction, whereas the He/N2 selectivity increased with immersion time. Thus, it appears that the crosslinking modification on Matrimid is mainly useful for separation of gas He/N2. The mixed gas permeabilities for both CO2 and CH4 are lower than their pure gas permeabilities at respective partial pressure. While the mixed gas selectivity is found to be lower for untreated membranes it is higher for cross-linked membranes, if a comparison is made with the ideal selectivity of CO2/CH4. P.S. Tin, T.S. Chung, Y. Liu, R. Wang, S.L. Liu and K.P. Pramoda: J. of Membrane Science 225(1–2) 77–90 (1 November 2003).
Mesoporous silica membranes on porous ceramic supports The authors of this study present a new approach for rapid formation of mesoporous, surfactant-templated silica membranes on coarse-pore a αAl2O3 ceramic supports. A surfactant-silica sol is dispersed in the gas phase in the form of small droplets and delivered to the surface of the planar support by a N2 carrier stream. Coalescence of deposited sol droplets combined with solvent evaporation-induced self-assembly of liquid crystalline meso-phases results in the formation of continuous, meso-structured silica-surfactant layers covering the surface of the support. These meso-structured silica membranes are impermeable right after synthesis and exhibit N2 permeance in the range 10–7–10–6 mol m–2 s–1 Pa–1 after surfactant removal. SEM studies revealed the presence of relatively smooth layers of thickness
about 1 µm on the surface of the ceramic supports, while SAXS and TEM investigations revealed that these membranes possess cubicordered mesopores of size 20 Å, without preferential orientation with respect to the substrate. Such membranes may find application in ultrafiltration separation processes, since surfactant-templating can be used for accurate control of the pore size/distribution in the proper range for a desired separation. G. Xomeritakis, C.M. Braunbarth, B. Smarsly, N. Liu, R. Köhn, Z. Klipowicz and C.J. Brinker: Microporous and Mesoporous Materials 66(1) 91–101 (18 November 2003).
Analysis of polarized layer resistance during UF A mathematical model based on filtration theory, coupled with the resistance in series model and gel polarization/film model was developed in this study. Unlike the cake filtration equipment where cake deposition continues until the wash cycle occurs, in case of continuous stirred ultrafiltration (UF) the deposited solutes are allowed to build up over the membrane indefinitely, along with continuous back transport of deposited solutes into bulk by the turbulence created by stirring action. To account for this back transport, a coefficient called ‘back transport coefficient’ has been defined which is found to be independent of any operating variables. Variation of polarized layer resistance was also studied with different operating variables like bulk concentration, stirrer speed and pressure differential. A correlation was also developed relating polarized layer resistance with those operating variables. A comparative study has been made between the experimentally found polarized layer resistance value, using ultrafiltration data of Bhattacharjee and Bhattacharya, with those found from correlation and this developed model based on filtration theory. The model has been found to predict the polarized layer resistance reasonably well once the three parameters describing the model – permeability coefficient, back transport coefficient and membrane hydraulic resistance – are known, along with the operating condition. Using the above-mentioned parameters, it is also possible to predict flux and/or total permeate
volume at any time under a given operating condition. C. Bhattacharjee and S. Datta: Separation and Purification Technology 33(2) 115–126 (1 October 2003).
Removal of chromates from drinking water by anion exchangers Strong-base anion-exchange resins were used for selective removal of Cr(VI) from tap water. The influence on the process efficiency of parameters, such as the type of anionexchange resin, the concentrations of Cl– and SO42– in the feed water, and the flow rate and pH of the feed water, was investigated. Regeneration was carried out by the reduction of the chromate with bisulphite under acidic conditions and the subsequent removal of the Cr from the column as the Cr3+ cation. The pH of the regenerant solution was then increased, causing Cr(OH)3 to precipitate, and the precipitate was removed by filtration. E. Korngold, N. Belayev and L. Aronov: Separation and Purification Technology 33(2) 179–187 (1 October 2003).
Next month News Business activities Industry trends Commercial news New products
Features Developments and applications around the world
Research Trends The latest membrane research published in the key journals
Patents Recently published US and WO patents
Events Calendar Conferences and shows relevant to the membranes industry
Membrane Technology December 2003
Events Calendar 11–14 December 2003 3rd Conference of the International Water History Association Cairo, Egypt Contact: Alv Terje Fotland, Coordinator CDS, Strømgt. 54, N-5007 Bergen Norway Tel: +47 55 589315 Fax: +47 55 589892 Email: [email protected] Web: www.iwha.net
14–19 December 2003 Solid–Liquid Separation Systems IV Pucon, Chile Contact: Engineering Conferences International, 6 MetroTech Center, Brooklyn, New York, NY 11201, USA Tel: +1 718 260 3743 Fax: +1 718 260 3574 Email: [email protected] Web: www.engconfintl.org
26–30 January 2004 Membrane Technology Course Cranfield, UK Contact: Short Course Office, Cranfield University, Cranfield, Bedfordshire, MK43 0AL, UK Tel: +44 1234 754176 Fax: +44 1234 751206 Email: [email protected]
17–20 February 2003 SMAGUA Water Zaragoza, Spain Contact: Zaragoza Trade Fair Centre
Tel: +34 976 76 4700 Fax: +34 976 33 0649 Web: www.feriazaragoza.com
Web: www.desline.com or www.edsoc.com
4–5 March 2004
Advanced Membrane Technology II
Industrial Water Recovery and Reuse (IWRR) Short Course Cranfield, UK Contact: Short Course Office, Cranfield University, Cranfield, Bedfordshire, MK43 0AL, UK Tel: +44 1234 754176 Fax: +44 1234 751206 Email: [email protected]
19–23 April 2004
23–28 May 2004 Irsee, Germany Contact: Engineering Conferences International, 6 MetroTech Center, Brooklyn, NY 11201, USA Tel: +1 718 260 3743 Fax: +1 718 260 3754 Email: [email protected] Web: www.engconfintl.org/4aj.html
8–11 June 2004 Pharmintech 2004
New Orleans, Louisiana, USA Contact: Charlotte Stripling Administrative Manager, AFS Society PO Box 1530, Northport, AL 35476, USA Tel: +1 205 333 6111 Fax: +1 205 333 6446 Email: [email protected]
Bologna, Italy Contact: Maria Grazia Facchinetti Marketing & Communications Manager Ipack-Ima srl, Corso Sempione 4, 20154 Milan, Italy Tel: +39 02 319 1091 Fax: +39 02 336 19826 Email: [email protected] Web: www.pharmintech.com
3–6 May 2004
26–30 June 2004
9th World Filtration Congress
EuroMed 2004: Desalination Strategies in South Mediterranean Countries Agadir, Morocco Contact: Miriam Balaban, European Desalination Society, Science and Technology Park of Abruzzo, Via Antica Arischia 1, 67100 L'Aquila, Italy Tel: +39 862 3475 308 Fax: +39 862 3475 213 Email: [email protected] or [email protected]
Simultaneously, the use of rotating electrodes substantially lowers the response time at submicromolar activities. An eccentrically placed Pb 2+-selective membrane on a rotating disk electrode, with optimized internal solution, showed a lower detection limit of aPb = 6.3 × 10–11 M. T. Vigassy, R.E. Gyurcsányi, E. Pretsch: Electroanalysis 15(15–16) 1270–1275 (September 2003).
Treatment for indirect potable reuse of water Microfiltration (MF) followed by reverse osmosis (RO), and soil-aquifer treatment (SAT), are the two principal technologies considered for indirect potable reuse of wastewater. This study, conducted at the Northwest Water Reclamation Plant, based in Mesa Arizona, USA, evaluated MF/RO and SAT (residence time in excess of 6 months) treated tertiary effluent with respect to organics removal. Effluent organic matter was characterized as total organic carbon (TOC), by UV absorbance (UVA), solid-state carbon-13 nuclear magnetic resonance spectroscopy, and size exclusion
Membrane Technology December 2003
Conference on Inorganic Membranes (ICIM8)
NAMS 2004 Honolulu, Hawaii Contact: Meeting Secretary, Ms Victoria Corrin, CERR, 5403 Boelter Hall, University of California, Los Angeles, CA 90095, USA Tel: +1 310 825 8798 Fax: +1 310 206 4107 Email: [email protected]
18–21 July 2004 The 8th International
chromatography. Several trace organic micropollutants, including ethylenediaminetetraacetate (EDTA), nitrilotriacetate (NTA), and alkylphenolethoxylate residues, were analyzed by gas chromatography/mass spectrometry (GC/MS). The study revealed that final TOC concentrations of MF/RO and SAT are 0.3 mg L–1 and 1.0 mg L–1, respectively. Based on the characterization techniques used, the character of bulk organics present in final SAT water resembles the character of natural organic matter present in drinking water. Depending on the molecular weight cut-off, RO membranes can efficiently reject high molecular weight organic matter (characterized as humic and fulvic acids). However, approximately 40–50% of the remaining TOC in permeates consists of low molecular weight acids and neutrals representing a molecular weight range of about 500 Da and less. In the SAT-treated effluent, EDTA and APECs were removed to approximately 4.3 µg L–1 and 0.54 µg L–1, respectively, but were below the detection limit in the MF/RO treated effluent. J.E. Drewes, M. Reinhard and P. Fox: Water Research 37(15) 3612–3621 (September 2003).
Cincinnati, Ohio, USA Contact: Gerri Burke, Department of Chemical and Materials Engineering University of Cincinnati, ML 171, Cincinnati, Ohio 45343, USA Tel: +1 513 556 6135 Fax: +1 513 556 1522 Email: [email protected]
28 September–1 October 2004 Euromembrane 2004 Hamburg, Germany Contact: c/o TUHH-Technologie GmbH (TuTech), Postfach 21079, Hamburg, Germany Tel: +49 40 766 1800 Fax: +49 40 7661 8018 Web: www.tutech.de/euromembrane
21–26 August 2005 International Congress on Membrane Processes – ICOM 2005 Seoul, Korea Contact: Prof. Young Moo Lee, National Research Laboratory for Membranes, School of Chemical Engineering, Hanyang University, Seungdong-ku, Seoul 133-791, Korea Tel: +82 2 2290 0525 Fax +82 2 2291 5982 Email: [email protected] Web: www.membrane.or.kr
Electrodialysis and nanofiltration of surface water In order to achieve stable groundwater levels, an equilibrium is needed between the use of groundwater for producing drinking water, and natural or artificial groundwater recharge by infiltration. Local governments usually require that the composition of the water used for artificial recharge is similar to the surface water that is naturally present in the specific recharge area. In this research, electrodialysis (ED) and nanofiltration were evaluated as possible treatment technologies for surface water from a canal in Flanders (in the North of Belgium), in view of infiltration at critical places on heathlands. Both methods were evaluated on the basis of a comparison between the water composition after treatment and the composition of local surface waters. The treatment generally involves ‘tuning’ the pH and the removal of contaminants originating from industrial and agricultural activity, for example, nitrates and pesticides. Further evaluation of the influence of the composition of the water on the characteristics of the artificial recharge, however, was not envisaged. In a case study of water from the canal Schoten-Dessel, satisfactory concentration reductions of Cl–, SO42–, NO3–, HCO3–,
15
RESEARCH TRENDS Na+, Mg2+, K+ and Ca2+ were obtained by ultrafiltration pretreatment followed by ED. Nanofiltration with UTC-20, N30F, Desal 51 HL, UTC-60 and Desal 5 DL membranes resulted in an insufficient removal level, especially for the monovalent ions. B. van der Bruggen, R. Milis, C. Vandecasteele, P. Bielen, E. Van San and K. Huysman: Water Research 37(16) 3867–3874 (September 2003).
Alumina and aluminate ultrafiltration membranes The fabrication of alumina ultrafiltration membranes using acetic acid surface stabilized alumina nanoparticles (A-alumoxanes) has been investigated. The pore size, pore-size distribution, and molecular weight cut-off (MWCO) parameters of the resulting membranes are highly dependent on the uniformity of the nanoparticle precursor, which is a function of the reaction time and reaction pH during their synthesis. By controlling the alumina nanoparticles, a significant improvement of the membrane performance is observed, compared with the authors’ previous results. The new alumoxane-derived membranes have a molecular weight cut-off in the range of less than 1000 g mol–1, and show good selectivity to a range of synthetic dyes. Further control over selectivity and flux of these ceramic membranes may be obtained by using doped alumina nanoparticles (Fe, Mn and La) that result in the formation of the appropriate aluminate membranes. Of these, LaAlO3 shows the most promising results. Retention coefficients and flux values also may be altered by the chemical functionalization of the interior surface of the membranes by reacting the alumina surface with carboxylic acids. K.A. DeFriend, M.R. Wiesner and A.R. Barron: J. of Membrane Science 224(1–2) 11–28 (15 October 2003).
Gas separation performance of Matrimid membranes At room temperature a chemical cross-linking modification was performed on Matrimid 5218, a material that has received pervasive attention in membrane separation. The cross-linking reaction was conducted by simply immersing the membrane in a p-xylenediamine solution at 16
ambient temperature for a stipulated period of time. The influence of cross-linking modification on thermal and gas transport properties of Matrimid membrane were studied. The gas permeability and selectivity of pure gases He, O2, N2, CH4 and CO2, as well as mixed gas of CO2/CH4 were measured. The gas permeabilities show their maximum values for one-day cross-linked membranes, but then decrease gradually with immersion time. It is found that the Matrimid membrane undergoes the plasticization phenomenon at 15 atm, however it is effectively suppressed by the proposed cross-linking modification. The ideal selectivities for O2/N2, CO2/CH4 and CO2/N2 remain almost constant and decreased slightly with the cross-linking reaction, whereas the He/N2 selectivity increased with immersion time. Thus, it appears that the crosslinking modification on Matrimid is mainly useful for separation of gas He/N2. The mixed gas permeabilities for both CO2 and CH4 are lower than their pure gas permeabilities at respective partial pressure. While the mixed gas selectivity is found to be lower for untreated membranes it is higher for cross-linked membranes, if a comparison is made with the ideal selectivity of CO2/CH4. P.S. Tin, T.S. Chung, Y. Liu, R. Wang, S.L. Liu and K.P. Pramoda: J. of Membrane Science 225(1–2) 77–90 (1 November 2003).
Mesoporous silica membranes on porous ceramic supports The authors of this study present a new approach for rapid formation of mesoporous, surfactant-templated silica membranes on coarse-pore a αAl2O3 ceramic supports. A surfactant-silica sol is dispersed in the gas phase in the form of small droplets and delivered to the surface of the planar support by a N2 carrier stream. Coalescence of deposited sol droplets combined with solvent evaporation-induced self-assembly of liquid crystalline meso-phases results in the formation of continuous, meso-structured silica-surfactant layers covering the surface of the support. These meso-structured silica membranes are impermeable right after synthesis and exhibit N2 permeance in the range 10–7–10–6 mol m–2 s–1 Pa–1 after surfactant removal. SEM studies revealed the presence of relatively smooth layers of thickness
about 1 µm on the surface of the ceramic supports, while SAXS and TEM investigations revealed that these membranes possess cubicordered mesopores of size 20 Å, without preferential orientation with respect to the substrate. Such membranes may find application in ultrafiltration separation processes, since surfactant-templating can be used for accurate control of the pore size/distribution in the proper range for a desired separation. G. Xomeritakis, C.M. Braunbarth, B. Smarsly, N. Liu, R. Köhn, Z. Klipowicz and C.J. Brinker: Microporous and Mesoporous Materials 66(1) 91–101 (18 November 2003).
Analysis of polarized layer resistance during UF A mathematical model based on filtration theory, coupled with the resistance in series model and gel polarization/film model was developed in this study. Unlike the cake filtration equipment where cake deposition continues until the wash cycle occurs, in case of continuous stirred ultrafiltration (UF) the deposited solutes are allowed to build up over the membrane indefinitely, along with continuous back transport of deposited solutes into bulk by the turbulence created by stirring action. To account for this back transport, a coefficient called ‘back transport coefficient’ has been defined which is found to be independent of any operating variables. Variation of polarized layer resistance was also studied with different operating variables like bulk concentration, stirrer speed and pressure differential. A correlation was also developed relating polarized layer resistance with those operating variables. A comparative study has been made between the experimentally found polarized layer resistance value, using ultrafiltration data of Bhattacharjee and Bhattacharya, with those found from correlation and this developed model based on filtration theory. The model has been found to predict the polarized layer resistance reasonably well once the three parameters describing the model – permeability coefficient, back transport coefficient and membrane hydraulic resistance – are known, along with the operating condition. Using the above-mentioned parameters, it is also possible to predict flux and/or total permeate
volume at any time under a given operating condition. C. Bhattacharjee and S. Datta: Separation and Purification Technology 33(2) 115–126 (1 October 2003).
Removal of chromates from drinking water by anion exchangers Strong-base anion-exchange resins were used for selective removal of Cr(VI) from tap water. The influence on the process efficiency of parameters, such as the type of anionexchange resin, the concentrations of Cl– and SO42– in the feed water, and the flow rate and pH of the feed water, was investigated. Regeneration was carried out by the reduction of the chromate with bisulphite under acidic conditions and the subsequent removal of the Cr from the column as the Cr3+ cation. The pH of the regenerant solution was then increased, causing Cr(OH)3 to precipitate, and the precipitate was removed by filtration. E. Korngold, N. Belayev and L. Aronov: Separation and Purification Technology 33(2) 179–187 (1 October 2003).
Next month News Business activities Industry trends Commercial news New products
Features Developments and applications around the world
Research Trends The latest membrane research published in the key journals
Patents Recently published US and WO patents
Events Calendar Conferences and shows relevant to the membranes industry
Membrane Technology December 2003