| 1. |
- Brinck, J, et al.
(författare)
-
Influence of pH on the adsorptive fouling of ultrafiltration membranes by fatty acid
- 2000
-
Ingår i: Journal of Membrane Science. - 0376-7388 .- 1873-3123. ; 164:1-2, s. 187-194
-
Tidskriftsartikel (refereegranskat)abstract
- Fatty acids are found in many solutions treated in ultrafiltration plants, for example, in dairy products, fermentation broth, oily waste water and bleach plant effluents from pulp mills. The influence of fatty acids on the fouling of membranes is often ignored because their concentration is rather low. However, during recent years the significant influence of fatty acids on the flux reduction of ultrafiltration membranes has attracted much attention. The pore radius of the membrane, the concentration of fatty acids and the pH of the solution all have a profound influence on the flux reduction when treating solutions containing fatty acids. In the work presented in this paper, the influence of pH on the flux reduction of an ultrafiltration membrane made of polyethersulphone was studied. It was found that there was no flux reduction under alkaline conditions, whereas the flux reduction under acidic conditions was severe. In order to elucidate the adsorption process, the adsorption of octanoic acid on a planar, hydrophobized silica surface was studied by means of in situ null ellipsometry. In the ellipsometry study a sharp increase in the amount adsorbed was observed when the concentration of undissociated acid approached the saturation concentration as the pH was decreased. This explains the observed flux reduction under acidic conditions. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 2. |
- Jönsson, Ann-Sofi, et al.
(författare)
-
A concentration polarization model for the ultrafiltration of nonionic surfactants
- 2006
-
Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 304:1, s. 191-199
-
Tidskriftsartikel (refereegranskat)abstract
- A theoretical model has been developed that describes ultrafiltration of nonionic surfactants. The model takes into account the fact that surfactants start to aggregate and form micelles at the critical micelle concentration, The model can be used to predict the performance of the membrane if the transport properties inside and at the membrane surface as well as the surfactant association behavior, are known. Three hydrophilic ultrafiltration membranes, made of regenerated cellulose, were used in the investigation. The cut-offs of the membranes were 10,000, 20,000, and 30,000 Da. The surfactant used in the investigation was the nonionic surfactant Triton X-100. The influence of the concentration of surfactant, transmembrane pressure and pure water flux were studied theoretically and experimentally. From the results presented in this work it can be concluded that the calculated values are in good agreement with experimental data. (c) 2006 Elsevier Inc. All rights reserved.
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| 3. |
- Jönsson, Ann-Sofi, et al.
(författare)
-
Colloidal fouling during ultrafiltration
- 1996
-
Ingår i: Separation Science and Technology. - : Informa UK Limited. - 0149-6395 .- 1520-5754. ; 31:19, s. 2611-2620
-
Tidskriftsartikel (refereegranskat)abstract
- Colloidal fouling causes serious problems in many membrane plants. Two different kinds of flux-reducing phenomena occur when treating colloidal dispersions, When treating stable dispersions the flux is reversible and can be restored after changing the operating parameters, such as the transmembrane pressure or the crossflow velocity. The flux reduction experienced when treating unstable colloidal dispersions is irreversible. In this study the DLVO theory, well-known from colloid chemistry, has been used to illustrate the mechanisms underlying the difference in filtration characteristics between stable and unstable colloidal dispersions.
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| 4. |
- Jönsson, Ann-Sofi, et al.
(författare)
-
Fluid flow in compressible porous media: I: Steady-state conditions
- 1992
-
Ingår i: AIChE Journal. - : Wiley. - 1547-5905 .- 0001-1541. ; 38:9, s. 1340-1348
-
Tidskriftsartikel (refereegranskat)abstract
- This is the first of two articles dealing with fluid flow in compressible porous media. In this article a model describing fluid flow and pressure-induced variations in porosity under stationary conditions is developed. In a forthcoming article the dynamic behavior during filtration and wet pressing of compressible porous media are presented. Fluid flow through rigid porous media is generally described by Darcy's law. The corresponding expression for compressible materials is derived in this article. This expression, the steady-state flow (SSF) equation, allows the steady-state flow to be easily calculated, either numerically, or by using the approximative analytical solutions that are also presented here. In the SSF equation optional empirical and/or theoretical permeability and compressibility relationships may be combined. Further, a new compressibility model which also applies for viscoelastic materials is presented. The influence of the compressibility of the material and the influence of precompression is illustrated.
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| 5. |
- Jönsson, Ann-Sofi, et al.
(författare)
-
Fluid flow in compressible porous media: II: Dynamic behavior
- 1992
-
Ingår i: AIChE Journal. - : Wiley. - 1547-5905 .- 0001-1541. ; 38:9, s. 1349-1356
-
Tidskriftsartikel (refereegranskat)abstract
- This article deals with the dynamic behavior during filtration and wet pressing of compressible porous media. An equation is developed which permits the derivation of the time dependency of porosity and flow at varying locations in a medium subjected to hydraulic pressure and/or mechanical load. Furthermore, a numerical solution that allows the equation to be solved rapidly and with high accuracy on a common PC is presented. The computer program developed in conjunction with this work has been used to illustrate the dynamics of fluid flow in some industrially important applications, such as wet pressing of paper pulp and flow in chromatography columns. The program has also been used to calculate the flow and concentration variations during mechanical impulse loading (that is, a press pulse).
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| 6. |
- Jönsson, Ann-Sofi, et al.
(författare)
-
Influence of the concentration of a low-molecular organic solute on the flux reduction of a polyethersulphone ultrafiltration membrane
- 1997
-
Ingår i: Journal of Membrane Science. - 0376-7388. ; 135:1, s. 117-128
-
Tidskriftsartikel (refereegranskat)abstract
- Drastic flux reductions are sometimes encountered during ultrafiltration of solutes much smaller than the membrane pores. This usually occurs during ultrafiltration of hydrophobic, low-molecular solutes, such as fatty acids, alcohols and alkanes. The influence of the concentration of a carboxylic acid, octanoic acid, on the flux of a polyethersulphone membrane was studied in this investigation. The concentration was found to have a marked influence on the flux. The flux reduction was moderate at low concentrations, but became severe above a certain, critical concentration. Two fur-reducing mechanisms were evaluated; reduction of the effective pore radius by adsorption of solute molecules on the pore walls, and blocking of pores by capillary condensation. The adsorption of octanoic acid on a hydrophobic solid surface was studied by null ellipsometry.
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| 7. |
- Jönsson, Ann-Sofi, et al.
(författare)
-
The influence of nonionic surfactants on hydrophobic and hydrophilic ultrafiltration membranes
- 1991
-
Ingår i: Journal of Membrane Science. - 0376-7388. ; 56:1, s. 49-76
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of different types of surfactants on ultrafiltration membranes has been investigated. A basic approach to membrane-surfactant interactions is also presented. A nonionic (Triton X-100), two anionic (potassium oleate and sodium dodecylbenzenesulphonate) and a cationic (hexadecyltrimethylammonium bromide) surfactant were investigated. The effects on commercial membranes of polysulphone, poly(vinylidene fluoride) and cellulose acetate were studied. The flux reductions of the hydrophobic membranes were found to be much more pronounced than the flux variations of the hydrophilic membranes. Both the material and the molecular weight cut-off were found to influence the performance of the hydrophobic membranes. A drastic influence of hydrophobic impurities was demonstrated. The retention of the nonionic surfactant was low at concentrations below the critical micelle concentration. The retention of the ionic surfactants was quite high, even at low concentrations.
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| 8. |
- Jönsson, Ann-Sofi, et al.
(författare)
-
Ultrafiltration of colloidal dispersions - A theoretical model of the concentration polarization phenomena
- 1996
-
Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 180:2, s. 504-518
-
Tidskriftsartikel (refereegranskat)abstract
- A general thermodynamic model of the concentration polarization phenomena of colloidal particles at a membrane surface is presented. The model is based on the balance between a thermodynamic force, due to the osmotic pressure gradient, and a frictional force, due to the fluid flow around each particle. A cell model description is used to model the concentration dependence of the thermodynamic force as well as the how properties in the concentrated colloidal solution. Equilibrium thermodynamics of the colloidal system can be used in the cell calculations since local equilibrium is assumed in the neighborhood of each colloidal particle (i.e., in each cell). This means that the concentration dependence of the osmotic pressure can be obtained, either from an experimental determination or from a theoretical model of the bulk properties of the colloidal system. To exemplify the usefulness of the model when establishing the influence of different operating parameters, such as the transmembrane pressure, the fluid shear, or different solution properties, such as concentration, particle size, pH, and ionic strength, a model system of charged spherical colloidal particles is used. The interaction between the particles is in the presented examples assumed to be a combination of electrostatic interactions, calculated from the Poisson-Boltzmann equation, dispersion forces, calculated as additive 1/r(6) interactions, and a hard sphere interaction calculated from the Carnahan-Starling equation. (C) 1996 Academic Press, Inc.
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| 9. |
-
34th EMS Summer School : Membranes in Biorefineries
- 2017
-
Proceedings (redaktörskap) (refereegranskat)abstract
- The EMS Summer School “Membranes in Biorefineries” is related to Annex XVII of the Industrial Energy Related Technologies and Systems (IETS)Implementing Agreement: “Membrane Filtration for Energy-efficient Separation of Lignocellulosic Biomass Components” co-ordinated by the Department of Chemical Engineering at Lund University, Sweden.The IETS Implementing Agreement is an initiative within IEA (International Energy Agency). The mission of IETS is to foster international co-operation among OECD and non-OECD countries for accelerated research and technology development of industrial energy-related technologies and systems. In doing so, IETS seeks to enhance knowledge of cost-effective new industrial technologies and system layouts that enable increase productivity and better product quality while improving energy efficiency and sustainability.
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| 10. |
- Andersson, Alexandra, et al.
(författare)
-
Comparison of diafiltration and size-exclusion chromatography to recover hemicelluloses from process water from thermomechanical pulping of spruce
- 2007
-
Ingår i: Applied Biochemistry and Biotechnology. - : Springer Science and Business Media LLC. - 1559-0291 .- 0273-2289. ; 137:1-12, s. 971-983
-
Tidskriftsartikel (refereegranskat)abstract
- Hemicelluloses constitute one of the most abundant renewable resources on earth. To increase their utilization, the isolation of hemicelluloses from industrial biomass side-streams would be beneficial. A method was investigated to isolate hemicelluloses from process water from a thermomechanical pulp mill. The method consists of three steps: removal of solids by microfiltration, preconcentration of the hemicelluloses by ultrafiltration, and purification by either size-exclusion chromatography (SEC) or diafiltration. The purpose of the final purification step is to separate hemicelluloses from small oligosaccharides, monosaccharides, and salts. The ratio between galactose, glucose, and mannose in oligo- and polysaccharides after preconcentration was 0.8: 1: 2.8, which is similar to that found in galactoglucomannan. Continuous diafiltration was performed using a composite fluoro polymer membrane with cutoff of 1000 Da. After diafiltration with four diavolumes the purity of the hemicelluloses was 77% (gram oligo- and polysaccharides/gram total dissolved solids) and the recovery was 87%. Purification by SEC was performed with 5, 20, and 40% sample loadings, respectively and a flow rate of 12 or 25 mL/min (9 or 19 cm/h). The purity of hemicelluloses after SEC was approx 82%, and the recovery was above 99%. The optimal sample load and flow rate were 20% and 25 mL/min, respectively. The process water from thermomechanical pulping of spruce is inexpensive. Thus, the recovery of hemicelluloses is not of main importance. If the purity of 77%, obtained with diafiltration, is sufficient for the utilization of the hemicelluloses, diafiltration probably offers a less expensive alternative in this application.
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| 11. |
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| 12. |
- Arkell, Anders, et al.
(författare)
-
Back-pulsing as an energy-saving method in the microfiltration of milk
- 2014
-
Ingår i: International Dairy Journal. - : Elsevier BV. - 0958-6946. ; 35:1, s. 1-5
-
Tidskriftsartikel (refereegranskat)abstract
- Extended shelf-life milk can be produced by a combination of microfiltration and pasteurisation. However, due to the need for high cross-flow velocity during microfiltration, the energy consumption is high. One way of decreasing the energy demand during microfiltration is to use back-pulsing for fouling control. Microfiltration was performed in constant flux mode on skim milk to measure the fouling rate. Different frequencies and durations of back-pulsing were investigated to determine the optimal conditions. The most promising conditions were used to evaluate the degree to which the cross-flow velocity could be decreased without significantly affecting the performance of the membrane. It was found that short pulses (0.2 s) at a frequency of 1 min-1 were most efficient, and the membrane performance was only slightly affected by reducing the cross-flow velocity from 5.8 m s-1 to 4.5 m s-1 with back-pulsing. This corresponds to a reduction in the energy requirement of 50%.
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| 13. |
|
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| 14. |
- Arkell, Anders, et al.
(författare)
-
Evaluation of membrane performance and cost estimates during recovery of sodium hydroxide in a hemicellulose extraction process by nanofiltration
- 2013
-
Ingår i: Separation and Purification Technology. - : Elsevier BV. - 1873-3794 .- 1383-5866. ; 118, s. 387-393
-
Tidskriftsartikel (refereegranskat)abstract
- The recovery the alkaline solvent from of a residual stream after the extraction of hemicelluloses in wheat bran was investigated. The solution was withdrawn from an ultrafiltration (UF) process in which hemicelluloses were recovered. The UF permeate, containing mainly NaOH, lignin and mono- and oligosaccharides, was treated by nanofiltration (NF). Seven NF membranes were tested in a parametric study, and the two membranes showing the best performance were further evaluated in a concentration study. The mean flux of a Koch SelRO MPF 36 and a Microdyn-Nadir NP010 membrane was about 200 l/m2 h during concentration to a volume reduction of 0.75. The retention of NaOH was <20%, while the retention of lignin and sugars was about 70% and >95%, respectively. Cost estimates for a NaOH recovery process indicated that an NF plant would have a pay-back time of less than 2 months if the plant was run continuously, and 7 months if it was used 25% of the time.
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| 15. |
- Arkell, Anders, et al.
(författare)
-
Increasing flux by back-pulsing in the microfiltration of milk
- 2015
-
Ingår i: International Dairy Journal. - : Elsevier BV. - 0958-6946. ; 41, s. 23-25
-
Tidskriftsartikel (refereegranskat)abstract
- Milk with extended shelf-life can be produced by microfiltration (MF) and pasteurisation in a cascade arrangement. In a previous study, we have shown that back-pulsing can be used to reduce the energy requirement in the MF of defatted milk. In this study, the influence of back-pulsing on MF was investigated at higher milk fluxes than in a prior study. The MF experiments were performed in constant-flux mode. The operational time until a certain pressure build-up was used as a measure of the performance. Fluxes between 350 and 500 L m−2 h−1 were investigated, with and without back-pulsing (frequencies ranging from 6 to 0.2 min−1). It was shown that the fouling rate was strongly dependent on the permeate flux; higher flux leading to a higher fouling rate. Improved MF performance was found using back-pulsing at a flux of 350 L m−2 h−1, while at higher fluxes, back-pulsing impaired the performance.
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| 16. |
|
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| 17. |
- Arkell, Anders, et al.
(författare)
-
Influence of heat pretreatment on ultrafiltration of a solution containing hemicelluloses extracted from wheat bran
- 2013
-
Ingår i: Separation and Purification Technology. - : Elsevier BV. - 1873-3794 .- 1383-5866. ; 119, s. 46-50
-
Tidskriftsartikel (refereegranskat)abstract
- Hemicelluloses extracted from wheat bran can be concentrated and purified by ultrafiltration. However, the viscosity of the process solution is rather high (about 5 mPa s at 80 C and a shear rate of 100 s1), which results in a relatively low flux. The solution was subjected to heat pretreatment in an attempt to decrease the viscosity and increase the flux. Pretreatment of the solution at 80 C for 72 h was found to reduce the viscosity by 25%. The flux during ultrafiltration with a 10 kDa ceramic membrane increased from 48 l/m2 h, for the untreated solution, to 62 l/m2 h. The increase in flux was lower than expected, and this was attributed to the formation of a fouling layer of acid-insoluble compounds on the membrane. Both hemicelluloses and lignin were partly degraded. The retention of lignin was reduced from about 30% to 18%, whereas the retention of hemicelluloses was above 95%, and was not affected by heat pretreatment. The decrease in lignin retention after heat pretreatment results in improved separation of hemicelluloses and lignin, facilitating the purification of hemicelluloses.
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| 18. |
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| 19. |
-
Bioblitz i Arkelstorp 16-17 augusti 2019
- 2020
-
Samlingsverk (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
- Arkelstorpsviken är den nordvästra delen av Oppmannasjön, som ären av Skånes största sjöar. Idén att genomföra en så kallad Bioblitzvid Arkelstorpsviken föddes under ett styrelsemöte i projektet "En viki Sjöriket Skåne" som är ett samarbete mellan Oppmanna Vånga Bygderåd och Högskolan Kristianstad. Projektets främsta syfte är att hitta en lösning på den kraftiga övergödningen i Arkelstorpsviken. Detta är ett ”Leader”-finansierat projekt, vilket innebär att stommen i projektetär lokal förankring. Det fanns röster i byn som kände att man gav området onödigt dåligt rykte genom att ständigt lyfta fram problemen med vattenstatusen i sjön. Under ett styrelsemöte 30 sep 2018 föddes iden att genom en Bioblitz lyfta fram de positiva värdena i och kring sjön. Den naturliga samarbetspartnern för detta projekt var forskningsmiljön MABH (Man & Biosphere Health) vid Högskolan Kristianstad,vars medlemmar tillsammans besitter en mycket bred biologisk kunskap.Med MABH i ryggen var alltså kompetensen säkrad för att genomföra en Bioblitz. Inbjudningar skickades ut till lokala naturorganisationerför att hitta ännu fler experter som kunde hjälpa till med särskilda artgrupper. Samtidigt jobbade man aktivt lokalt med att försöka engagera intresserad allmänhet. Inbjudningar och direktreklam skickades ut till samtliga hushåll med postadress Arkelstorp. I ett försök att synas genom mediebruset anordnades en tävling, som gick ut på att gissa antalet arter (taxa) som hittades under Bioblitzen. Två lokala företag ställde upp och första priset för den vuxna individ som gissade närmstvar en 3-rätters måltid på Bäckaskogs Slott. De yngre tävlande kunde vinna en kanotutflykt med familjen på Ivögården.
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| 20. |
- Blomgren, Y, et al.
(författare)
-
Concentration of acid hydrolysate by reverse osmosis and mechanical vapor recompression evaporation
- 1991
-
Ingår i: Journal of Wood Chemistry and Technology. - : Informa UK Limited. - 0277-3813 .- 1532-2319. ; 11:1, s. 117-135
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of this project was to investigate possible methods for the concentration of acid hydrolyzate obtained from hydrolyzing wood. A detailed study of concentration of sugar solution by reverse osmosis, RO, has been performed as well as a comparison with mechanical vapor recompression evaporation. The comparison has, in this specific case, shown that RO is currently more expensive. The result is, however, highly dependent on investment costs, and future expansion of membrane technology could mean lower area costs which would favor the technology.
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| 21. |
- Byhlin, Henric, et al.
(författare)
-
Influence of adsorption and concentration polarisation on membrane performance during ultrafiltration of a non-ionic surfactant
- 2003
-
Ingår i: Desalination. - 1873-4464. ; 151:1, s. 21-31
-
Tidskriftsartikel (refereegranskat)abstract
- Surfactants are present in almost all aqueous solutions-either as additives for different purposes, or because they occur naturally. Because of the common occurrence of surfactants in process water it is important to know how they behave in membrane processes. Ultrafiltration membranes allow almost complete passage of surfactant monomers, but reject micelles almost completely. Concentration polarisation during ultrafiltration of surfactant solutions is therefore mainly influenced by the presence of micelles. Operating parameters, e.g. the transmembrane pressure and the concentration of surfactant, as well as the pure water flux of the membrane, have a marked influence on the performance of hydrophilic membranes, as shown in this investigation. A distinct difference between the interaction of a non-ionic surfactant with hydrophilic and hydrophobic membranes was observed. The hydrophobic membrane showed a flux reduction already at concentrations below the critical micelle concentration (CMC), whereas no flux reduction was observed for a hydrophilic membrane with the same nominal molecular weight cut-off, below the CMC.
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| 22. |
- Falth, F, et al.
(författare)
-
Ultrafiltration of effluents front chlorine-free, kraft pulp bleach plants
- 2001
-
Ingår i: Desalination. - 1873-4464. ; 133:2, s. 155-165
-
Tidskriftsartikel (refereegranskat)abstract
- Ultrafiltration has proven to be a useful technology for treating alkaline bleach plant filtrates in sulphite pulp mills. In this investigation the treatment of seven alkaline filtrates from kraft pulp mills were studied. The results include high fluxes and fair, or even good, removal of organic, as well as inorganic, substances. The flux seems to depend on the concentration of the bleach plant filtrate rather than its origin. The factor with the largest impact on flux is conductivity, i.e., the concentration of the low-molecular-weight inorganic substances. The retention of organic substances varies depending on the type of filtrate and the water management system of the mill. The retention is highest when treating filtrates from the first alkaline stage from traditional ECF mills. Filtrates from modem ECF and TCF mills contain a larger fraction of low-molecular-weight substances, which are not retained as efficiently. The treatment not only reduces the organic content of the filtrates but also increases the fraction that is biodegradable. The membranes retain a rather large fraction of the multi-valent ions, while the monovalent ions are let through.
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| 23. |
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| 24. |
- Frenander, U, et al.
(författare)
-
Cell harvesting by cross-flow microfiltration using a shear-enhanced module
- 1996
-
Ingår i: Biotechnology and Bioengineering. - 1097-0290. ; 52:3, s. 397-403
-
Tidskriftsartikel (refereegranskat)abstract
- Protein, produced by a bacterial culture of recombinant Vibrio cholerae, was separated from cells in a fermentation broth by cross-flow microfiltration. A new, mechanically agitated (rotational) shear filter, the DMF(TM) filter from Pall, was used to perform the separation. Higher protein recovery and permeate flux than commonly obtained during cell harvesting were demonstrated using sixfold concentration followed by twofold diafiltration. The transmembrane pressure only increased by 10 kPa when the flux was kept constant at 150 L/m(2) h during both concentration and diafiltration. The protein transmission was about 100% initially, and over 90% at the end of the concentration process. The protein transmission during the diafiltration was over 80%. The total recovery of protein was 97%. When using an enzymatic cleaning agent, no significant pure water flux decrease was detected during the course of the experiments. (C) 1996 John Wiley & Sons, Inc.
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| 25. |
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| 26. |
- Holmqvist, Anders, et al.
(författare)
-
Ultrafiltration of kraft black liquor from two Swedish pulp mills
- 2005
-
Ingår i: Chemical Engineering Research & Design. - : Elsevier BV. - 0263-8762. ; 83:A8, s. 994-999
-
Tidskriftsartikel (refereegranskat)abstract
- Extraction of lignin by ultrafiltration of black liquor from two Swedish pulp mills has been studied. One of the mills employs batch digestion and the other continuous digestion. At both mills softwood was used as raw material. The black liquor was withdrawn before the evaporator unit. A ceramic membrane with a cut-off of 15 000 g mol(-1) was used in the experiments. The average flux during concentration to 90% volume reduction was 160 and 110L m(-2) h(-1) for the liquors from the batch and the continuous digestion processes, respectively, when the temperature was 90 degrees C and the transmembrane pressure 200 kPa. The retention of lignin was about the same for both liquors, 35%. A cost estimate of extraction of lignin fuel from black liquor was made, based on experimental data from ultrafiltration at various operating conditions. The cost was found to be about 20 E per MWh of calorific value of the lignin fuel.
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| 27. |
- Into, M, et al.
(författare)
-
Reuse of industrial wastewater following treatment with reverse osmosis
- 2004
-
Ingår i: Journal of Membrane Science. - : Elsevier BV. - 0376-7388. ; 242:1-2, s. 21-25
-
Tidskriftsartikel (refereegranskat)abstract
- The Perstorp, industrial park in southern Sweden is faced with water shortage problems. One way to reduce these problems is through the reuse of recycled water. In this paper the results of treating 240 m(3) per day wastewater in a reverse osmosis (RO) plant are presented. High-quality water, which is used as make-up water in cooling towers, is produced from a difficult and varying feed. Severe fouling problems during the first year of operation have been solved and the reliability of the RO plant is now good. The only pretreatment employed before the RO plant is a bag filter. Despite no cleaning of the membranes, the membrane lifetime is 16 months, which means that RO treatment is economically feasible. The savings made by using the RO plant emanate from reduced use of fresh water and lower discharge charges. (C) 2004 Elsevier B.V. All rights reserved.
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| 28. |
- Jonsson, C, et al.
(författare)
-
Influence of the membrane material on the adsorptive fouling of ultra-filtration membranes
- 1995
-
Ingår i: Journal of Membrane Science. - 0376-7388. ; 108:1-2, s. 79-87
-
Tidskriftsartikel (refereegranskat)abstract
- The hydrophilic/hydrophobic properties of the membrane material have an important influence on the membrane flux reduction when treating solutions containing hydrophobic solutes. Different methods of measuring the hydrophobic properties of membranes have been evaluated; measurement of the contact angle being the most commonly used method. In this investigation the flux reduction of eight membranes of approximately the same cut-off, but of different materials, was determined and related to the contact angle. A low-molecular weight hydrophobic solute (octanoic acid) was used as foulant. The flux of the hydrophilic membrane was only marginally reduced, whereas the flux reduction of hydrophobic membranes was significant. Membranes of polyvinylidene fluoride had the lowest flux reduction of the hydrophobic membranes. Differences between membranes of the same material (polyethersulfone), but from different manufacturers, were observed. No relation was found between the flux reduction and the contact angle of the membrane, the initial pure water flux or the retention of a hydrophilic macromolecule (PEG20). The pure water flux of two of the hydrophobic membranes increased significantly during the experiments, whereas the pure water flux of the other hydrophobic membranes decreased. A membrane of polyaramide, with a contact angle of the same order of magnitude as the other hydrophobic membranes, behaved as a hydrophilic membrane, with no influence on the flux at concentrations below the solubility limit of the hydrophobic solute, but experienced the most severe flux decline of all the membranes included in the investigation at the solubility limit. Two modified membranes were included in the investigation. The flux reduction of these membranes was not significantly lower than for the corresponding unmodified membranes of the same materials.
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| 29. |
- Jonsson, C, et al.
(författare)
-
The influence of degreasing agents used at car washes on the performance of ultrafiltration membranes
- 1995
-
Ingår i: Desalination. - : Elsevier BV. - 1873-4464 .- 0011-9164. ; 100:1-3, s. 115-123
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of washing chemicals used at car washes on the flux and retention of three ultrafiltration (UF) membranes has been studied. Eleven commercial degreasing agents, two shampoo agents and a wax were included in the investigation. The membrane performance when treating waste water collected at a car wash at different times of the year was also studied. The retention of the different chemicals varied greatly, but there was no significant difference in COD retention among the three UF membranes. The highest flux was observed when treating the alkaline degreasing agents and the shampoo solutions. The flux and COD retention when treating the waste water from the car wash were 30-50 l/m(2) h and 60%, respectively. One of the low-retention degreasing agents was treated by nanofiltration (NF). The retention was significantly higher when using NF, but the COD concentration in the permeate was still too high to allow the permeate to be discharged without further treatment.
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| 30. |
- Jönsson, Ann-Sofi, et al.
(författare)
-
Concentration and purification of lignin in hardwood kraft pulping liquor by ultrafiltration and nanofiltration
- 2008
-
Ingår i: Chemical Engineering Research & Design. - : Elsevier BV. - 0263-8762. ; 86:11A, s. 1271-1280
-
Tidskriftsartikel (refereegranskat)abstract
- Today, there is considerable interest in integrated forest biorefineries which, besides pulp, produce high-value-added products, such as, polymers and carbon fibres. Lignin is the major non-cellulosic constituent of wood. It is a complex, amorphous highly crosslinked polyphenolic. Lignosulphonate in spent liquor in sulphite mills has long been isolated using ultra filtration. Generally, precipitation is used to extract the lignin from kraft black liquor. The liquor is commonly withdrawn from the evaporation unit in the recovery system, where the dry substance is optimal for precipitation. Lately, interest in the isolation of lignin by ultrafiltration of kraft black liquor has arisen. The concentration of the liquor is not that critical, and there is therefore considerable freedom in the choice of liquor for treatment with ultra filtration. In this work, the influence of membrane cut-off, transmembrane pressure and cross-flow velocity during ultrafiltration of cooking liquor and black liquor was studied. The extraction of lignin from hardwood black liquor withdrawn before the evaporation unit was investigated. A hybrid ultrafiltration/nanofiltration process was used. The lignin concentration was 60 g/l in the black liquor and 165 g/l in the product stream (the narrofiltration retentate). A cost estimate indicates a production cost of (sic)33 per tonne of lignin. (C) 2008 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
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| 31. |
- Jönsson, Ann-Sofi
(författare)
-
Concentration polarization and fouling during ultrafiltration of colloidal suspensions and hydrophobic solutes
- 1995
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Ingår i: Separation Science and Technology. - : Informa UK Limited. - 0149-6395 .- 1520-5754. ; 30:2, s. 301-312
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Tidskriftsartikel (refereegranskat)abstract
- Flux reductions experienced during ultrafiltration are due either to concentration polarization or fouling. It is usually difficult to distinguish between these two phenomena, but by using a turbulence-promoting module it is possible to determine the reversibility of a flux reduction, and thus distinguish between concentration polarization and fouling. By using a turbulence-promoting module, it is also possible to distinguish between different cases of fouling. In this paper, fouling caused by the deposition of material at the surface of the membrane is illustrated by results from tests with a silica sol, and fouling due to interactions in the membrane matrix is illustrated by results from ultrafiltration of a low-molecular organic solute.
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| 32. |
- Jönsson, Ann-Sofi, et al.
(författare)
-
Cost estimates of kraft lignin recovery by ultrafiltration
- 2009
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Ingår i: Desalination. - : Elsevier BV. - 1873-4464 .- 0011-9164. ; 237:1-3, s. 254-267
-
Tidskriftsartikel (refereegranskat)abstract
- Climate change and endeavours towards a sustainable society have brought the interest of wood-based biorefineries to the fore. Lignin is the main energy carrier in chemical pulp mills. Today, the heat value of lignin is commonly recovered in the recovery boiler of the mill. However, interest in the extraction of lignin for use as an external biofuel and in speciality chemicals is growing. Lignosulphonates have been isolated by ultrafiltration from spent liquor in sulphite pulp mills for decades, whereas kraft lignin is mainly extracted by precipitation. The isolation of kraft lignin by ultrafiltration is currently attracting increasingly greater interest because lignin can be extracted from pulping liquors at almost all positions in a pulp mill using ceramic membranes, without altering the pH or temperature of the liquor. In this work hardwood lignin was recovered from two process streams in a kraft pulp mill by Ultrafiltration with a ceramic membrane with a cut-off of 15,000 Da. It was shown that lignin can be recovered from a cooking liquor at a cost of about 60 (sic) per tonne of lignin and from black liquor withdrawn from the evaporation unit at 33 (sic) per tonne.
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| 33. |
- Jönsson, Ann-Sofi, et al.
(författare)
-
Costs for membrane cleaning – an economic assessment
- 2016
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Konferensbidrag (refereegranskat)abstract
- Cleaning is an inevitable, and often costly, part of most membrane filtration plants. The economic assessment of cleaning costs is often rather arbitrary when researchers design and estimate costs of a membrane plant in a new application. Severity of fouling, operation conditions, cleaning agents and cleaning frequency all influence the costs for membrane cleaning. In addition to the costs of the cleaning process itself, cleaning also affects membrane lifetime, membrane performance during filtration and process down time. The cleaning procedure and cleaning frequency varies from one application to another and most cleaning studies are therefore trial-and-error investigations. Temperature, time, concentration and type of cleaning agent must be adapted to the conditions in each individual application. Furthermore, in some cases it is necessary to use a sequence of different cleaning agents. The influence of cleaning conditions on costs for membrane cleaning is illustrated in this work.
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| 34. |
- Jönsson, Ann-Sofi
(författare)
-
Fouling during ultrafiltration of a low molecular weight hydrophobic solute
- 1998
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Ingår i: Separation Science and Technology. - : Informa UK Limited. - 0149-6395 .- 1520-5754. ; 33:4, s. 503-516
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Tidskriftsartikel (refereegranskat)abstract
- The influence of a small hydrophobic solute (octanoic acid) on the flux reduction and the flux recovery of two ultrafiltration membranes was studied in this investigation. The two membranes were made of polyether sulfone and regenerated cellulose, both with a nominal molecular weight cutoff of 20,000 Da. The concentration of the octanoic acid solution was found to have a significant influence on not only the extent of flux reduction during treatment of the octanoic acid solution, but also on the flux recovery when the membrane was rinsed with deionized water. After treatment of the octanoic acid solution, a pure water flux increase of 1.5 times the pure water flux of the new, unused polyether sulfone membrane was observed. Different causes of the increased pure water flux after treatment of the octanoic acid solution are presented, and the serious consequences this apparent positive effect can cause in industrial applications are discussed.
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| 35. |
- Jönsson, Ann-Sofi, et al.
(författare)
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Fundamental principles of ultrafiltration
- 1990
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Ingår i: Chemical Engineering and Processing. - 0255-2701. ; 27:2, s. 67-81
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Tidskriftsartikel (refereegranskat)abstract
- Different theoretical models describing the influence of the operating parameters are treated in this paper. The osmotic pressure, gel layer and resistance in series models are presented. The influence of different operating parameters, such as the operating pressure, temperature, cross-flow velocity and concentration is demonstrated. The complex fouling phenomenon is reviewed. Finally, various pretreatment and cleaning operations are presented.
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| 36. |
- Jönsson, Ann-Sofi, et al.
(författare)
-
Influence of pH and surfactants on ultrafiltration membranes during treatment of bleach plant effluent
- 1988
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631. ; 3:4, s. 159-165
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Tidskriftsartikel (refereegranskat)abstract
- The influence of pH and surfactants during treatment of E-stage effluent was studied. Three tubular ultrafiltration membranes were used in the experiment. The flux of the three membranes was at its highest level at the normal, high pH, of the effluent. In this experiment the densest membrane showed the greatest flux decrease, while the most ouen membrane was either unaffected bv variations in ph or experienced a more moderate decrease. The flux after treatment with a nonionic surfactant could be restored by cleaning with a commercial cleaning agent, but it was not possible to restore the initial flux when a cationic surfactant had been added to the effluent. The role of cleaning during membrane treatment is also discussed.
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| 37. |
- Jönsson, Ann-Sofi
(författare)
-
Influence of shear rate on the flux during ultrafiltration of colloidal substances
- 1993
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Ingår i: Journal of Membrane Science. - 0376-7388. ; 79:1, s. 93-99
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Tidskriftsartikel (refereegranskat)abstract
- The shear rate at the surface of a membrane has a distinct influence on the membrane flux in systems containing colloidal substances. If the shear rate is decreased, flux decreases since the thickness of the boundary layer of retained solutes at the membrane surface then increases. When low molecular solutes are used, flux increases again when the shear rate is increased. However, if large solutes are used, polymeric and colloidal substances, for example, it sometimes happens that the flux cannot be increased to its original value again by increasing the shear rate: the flux decline is regarded as irreversible. Experiments, performed in a new type of turbulence-promoting module, which illustrate the influence of shear rate on flux when treating solutions containing colloidal substances, are presented in this paper. It is also shown that a flux decrease which can not be restored by increasing the shear rate, may be completely restored by a temporary interruption of the permeate flow.
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| 38. |
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| 39. |
- Jönsson, Ann-Sofi, et al.
(författare)
-
Membrane distillation - A theoretical study of evaporation through microporous membranes
- 1985
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Ingår i: Desalination. - : Elsevier BV. - 1873-4464 .- 0011-9164. ; 56, s. 237-249
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Tidskriftsartikel (refereegranskat)abstract
- Membrane distillation is a process in which, for example, water in a heated salt solution, evaporates through a porous membrane. The vapour condenses on a coolant surface on the other side of the membrane. The two liquid streams, the salt solution and the condensate, are separated by a highly porous hydrophobic membrane. Surface tension forces withhold liquids from the pores and prevent contact between the two liquids. The temperature difference, causing a corresponding vapour pressure difference across the membrane, provides the driving force of the membrane distillation process. Evaporation will occur at the solution surface if the vapour pressure on the solution side is greater than the vapour pressure at the condensate surface. Vapours then diffuse through the pores to the cooler surface, where they condense. The dependence of mass and heat transport upon different process and membrane parameters involved in membrane distillation has been investigated theoretically.
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| 40. |
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| 41. |
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| 42. |
- Jönsson, Ann-Sofi, et al.
(författare)
-
Separationsteknik som vinner terräng
- 1984
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Ingår i: KEMISK TIDSKRIFT. - 0039-6605. ; 96:13, s. 40-45
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Tidskriftsartikel (populärvet., debatt m.m.)
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| 43. |
- Jönsson, Ann-Sofi, et al.
(författare)
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The application of membrane technology in the pulp and paper industry
- 1985
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Ingår i: Desalination. - : Elsevier BV. - 1873-4464 .- 0011-9164. ; 53:1-3, s. 181-196
-
Tidskriftsartikel (refereegranskat)abstract
- A state of the art review on industrial applications of membrane technology in the pulp and paper industry is presented. Applications have been arranged under three headlines, effluent treatment, concentration and fractionation. Among new and promising applications are treatment of waste paper white water, effluent after deresination and concentration of spent liquor from chemi-mechanical pulping.
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| 44. |
- Jönsson, Ann-Sofi, et al.
(författare)
-
Treatment of C-stage and E-stage bleaching plant effluent by ultrafiltration
- 1989
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631. ; 4:3, s. 184-187
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of pH on membranes of different materials and different cut off has been studied. One ceramic microfiltration membrane and three synthetic ultrafiltration membranes were included in the study. The pH of an acidic (C-stage) and and alkaline (E-stage) bleaching effluent was varied. For the E-stage effluent the membrane performance seemed to be correlated to the cut off of the membrane. During treatment of the C-stage effluent the performance of the membranes was more disparate
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| 45. |
- Jönsson, Ann-Sofi, et al.
(författare)
-
Treatment of C-stage and E- stage effluents from a bleach plant using a ceramic membrane
- 1988
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631. ; 3:1, s. 4-7
-
Tidskriftsartikel (refereegranskat)abstract
- C-stage effluent, E-stage effluent and a total effluent (C-stage and E-stage effluent mixed in proportion to the volumes of the effluents at the mill) have been treated with a ceramic microfilter membrane. The flux of the total effluent was considerably lower than of the separate effluents. The fluxes of the E-stage and C-stage effluents were 550 and 1,300 l/m2h, respectively, while the flux of the total effluent was only 150 l/m2h. The low filtration capacity is thought to be caused by adsorption of substances onto the membrane. The influence of pH on the filtration capacity of C- and E-stage effluent was clearly demonstrated.
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| 46. |
- Jönsson, Ann-Sofi
(författare)
-
Treatment of effluent from alkali extraction with ultrafiltration and reverse osmosis
- 1989
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631. ; 4:1, s. 33-37
-
Tidskriftsartikel (refereegranskat)abstract
- Effluent from alkali extraction of chlorinated pulp was treated with ultrafiltration (UF). Three different ultrafiltration (UF) membranes were tested. The permeate from one of the UF membranes was further treated with reverse osmosis (RO). Titration curves for the permeates from the different UF and R0 membranes were determined. The concentration of charged compounds was calculated from the titration data and compared with the COD and AOX of the permeates. The retention of COD and AOX was between 50 and 90% for the UF membranes, whereas the retention of carboxylic acid groups was considerably lower, 15-45%. During the R0 treatment the retention of all compounds was found to be very high. For the densest R0 membrane the retention of AOX and compounds with carboxylic acid groups was higher than 99%. The retention of COD was 96%.
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| 47. |
- Jönsson, Ann-Sofi, et al.
(författare)
-
Treatment of high-temperature rinsing water from a degreasing plant by reverse osmosis
- 1997
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Ingår i: Desalination. - 1873-4464. ; 114:2, s. 175-181
-
Tidskriftsartikel (refereegranskat)abstract
- In the manufacture of heat-exchangers, it is of great importance that the heat-exchanger plates be thoroughly cleaned before being sealed. At a Swedish heat-exchanger manufacturer, oil, grease and other impurities are removed in a washing plant consisting of three stages: a degreasing tank and two rinsing tanks. The possibility of improving the cleanliness of the heat-exchanger plates, without increasing the need for fresh water, by treating the rinsing water in a reverse osmosis (RO) plant, was studied in this investigation. A new, high-temperature-resistant, thin-film RO membrane from Osmonics-Desal was used in the experiments. The influence of a lubricant, based on a block copolymer, and an alkaline degreasing agent on the membrane performance was studied. The flux reduction of a model rinsing solution with time was moderate. The flux after 500 h of continuous treatment at 65 degrees C and 4.0 MPa was 351/m(2) h, and the permeate quality fulfilled the demands of the heat-exchanger manufacturer.
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| 48. |
- Jönsson, Ann-Sofi, et al.
(författare)
-
Treatment of paper coating colour effluents by membrane filtration
- 1996
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Ingår i: Desalination. - : Elsevier BV. - 1873-4464 .- 0011-9164. ; 105:3, s. 263-276
-
Tidskriftsartikel (refereegranskat)abstract
- Dilute coating colour effluents are created during the coating of paper and board. After treating the colour effluents with ultrafiltration, the retentate can be reused as coating colour and the permeate can replace fresh water. At the same time, the load on the external treatment plant is reduced. In this investigation, pilot-plant experiments were performed at a paper mill. A high and steady flux, 120 l/m(2) h, was achieved at a colour concentration of 10-15%. The flux at 40% was lower but steady, 50 l/m(2) h. The membrane performance when treating five coating colours with varying composition was studied in laboratory experiments. The composition of the colour had a significant influence on the membrane performance. A colour containing starch exhibited the lowest flux and the lowest COD retention of the colours included in the study, while a colour in which the clay had been replaced by CaCO3 exhibited the highest final concentration of 60%.
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| 49. |
- Jönsson, Ann-Sofi, et al.
(författare)
-
Ultrafiltration applications
- 1990
-
Ingår i: Desalination. - : Elsevier BV. - 1873-4464 .- 0011-9164. ; 77:1-3, s. 135-179
-
Forskningsöversikt (refereegranskat)
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| 50. |
- Jönsson, Ann-Sofi
(författare)
-
Ultrafiltration of bleach plant effluent
- 1987
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631. ; 2:1, s. 23-29
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Tidskriftsartikel (refereegranskat)abstract
- An up-to-date evaluation of capacity and retention of new membranes with regard to bleach plant effluents has been made. The results from a trial of seven reverse osmosis, ultrafiltration and microfiltration membranes are reported. The trial has even included membranes not yet commercially available. The trial has demonstrated that some of the tested membranes could probably combine a satisfactory flux and an acceptable retention. A rough estimate of the costs shows that treatment of the E-stage effluent with ultrafiltration could be performed within a total cost of approximately 25 SEK per tonne of pulp.
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