| 1. |
- Jareman, Fredrik, et al.
(author)
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Effects of aluminum content on the separation properties of MFI membranes
- 2003
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In: Separation and Purification Technology. - 1383-5866 .- 1873-3794. ; 32:1-3, s. 159-163
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Journal article (peer-reviewed)abstract
- MFI membranes with almost identical film thickness and defect distribution but different Si/Al ratio were evaluated by separation of butane and hexane isomers. Film thickness was evaluated by SEM and defect distribution by porosimetry. When the temperature was varied, the membranes showed similar separation trends for butanes, but clear differences were observed for hexane separation. The hexane separation factor varied with temperature for the silicalite-1 membrane but was constant for the ZSM-5 membrane. It is believed that this difference may be a result of differences in adsorption properties.
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| 2. |
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| 3. |
- Ahmad, Arslan, et al.
(author)
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Impact of phosphate, silicate and natural organic matter on the size of Fe(III) precipitates and arsenate co-precipitation efficiency in calcium containing water
- 2020
-
In: Separation and Purification Technology. - : ELSEVIER. - 1383-5866 .- 1873-3794. ; 235
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Journal article (peer-reviewed)abstract
- Removal of arsenic (As) from water by co-precipitation with Fe(III) (oxyhydr)oxides is a widely used technique in water treatment. Nevertheless, As removal efficiency appears to be sensitive to the composition of the water matrix. The aim of this study was to gain a deeper understanding of the independent and combined effects of silicate (Si), phosphate (P), natural organic matter (NOM) and calcium (Ca) on arsenate [As(V)] co-precipitation efficiency and the size of Fe(III) precipitates. We found that, in complex solutions, containing multiple solutes and high levels of Ca, (variations in) Si and P concentrations reduce As(V) removal to some extent, mainly due to a decreased adsorption of As(V) onto Fe(III) precipitates. On the other hand, NOM concentrations reduced As(V) removal to a much greater extent, due to possible formation of mobile Fe(III)-NOM complexes that were difficult to remove by filtration. These findings have a great significance for predicting As(V) removal as a function of seasonal and process-related water quality changes at water treatment plants.
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| 4. |
- Ahmad, Arslan, et al.
(author)
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Mechanisms of arsenate removal and membrane fouling in ferric based coprecipitation-low pressure membrane filtration systems
- 2020
-
In: Separation and Purification Technology. - : ELSEVIER. - 1383-5866 .- 1873-3794. ; 241
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Journal article (peer-reviewed)abstract
- Ferric based coprecipitation-low pressure membrane filtration is a promising arsenic (As) removal method, however, membrane fouling mechanisms are not fully understood. In this study we investigated the effect of feed water composition and membrane pore size on arsenate [As(V)] removal and membrane fouling. We observed that As removal efficiency was independent of the membrane pore size because the size of the Fe(III) particles was larger than the pore size of the membranes, attributed to a high calcium concentration in the feed water. Arsenic coprecipitation with Fe(III) (oxyhydr)oxides rapidly reached equilibrium before membrane filtration, within 1 min. Therefore, As removal efficiency was not improved by increasing residence time before membrane filtration. The removal of As(V) was strongly dependent on feed water composition. A higher Fe(III) dose was required to reduce As(V) to sub-mu g/L levels for feed water containing higher concentration of oxyanions such as phosphate and silicate, and lower concentration of cations such as calcium. Cake-layer formation was observed to be the predominant membrane fouling mechanism.
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| 5. |
- Ahmad, Sheikh Asrar, et al.
(author)
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Use of digital thruster to separate the cadmium and lead metals from mixture sample
- 2008
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In: Separation and Purification Technology. - : Elsevier BV. - 1873-3794 .- 1383-5866. ; 63:1, s. 101-106
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Journal article (peer-reviewed)abstract
- The present work deals with the use of a digital thruster (DT) for the separation of cadmium and lead metals from mixture samples. Mixtures of lead and cadmium salts with varying concentrations were injected into a free electrolytic diffusion apparatus (FEDA). The microcathodes surrounding the central anode were programmed witha DT. The DT distributed the charge over the microcathodes at time intervals of 100-900 mu s or at the frequency of 625-70 Hz. The microcathodes become electrodeposited with lead and cadmium metals, showing both separation and co-deposition. The purity of deposited metals was analyzed by Atomic Absorption Spectroscopy (AAS) using PerkinElmer and Aldrich AAS standards. (C) 2008 Elsevier B.V. All rights reserved.
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| 6. |
- Al-Rudainy, Basel, et al.
(author)
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From lab-scale to on-site pilot trials for the recovery of hemicellulose by ultrafiltration: Experimental and theoretical evaluations
- 2020
-
In: Separation and Purification Technology. - : Elsevier BV. - 1873-3794 .- 1383-5866. ; 250
-
Journal article (peer-reviewed)abstract
- Spent sulfite liquor (SSL) is a byproduct of the sulfite pulping process of wood. SSL usually contains monosugars and lignosulfonates, which are fermented to produce ethanol and dried to generate lignosulfonate salts. However, the SSL that was used in this work was derived from the first step of a 2-step sulfite pulping process of softwood under mild pulping conditions in the first stage of cooking. The resulting SSL contained polymeric hemicelluloses, which are not used today but have many potential applications. The up-concentration of this SSL had been performed on a lab scale by ultrafiltration. However, the pilot-scale ultrafiltration of hemicellulose-rich sodium-based SSL has not been reported. In this study, the operating conditions for the lab-scale concentration of hemicellulose-rich, sodium-based SSL were examined in a pilot-scale membrane filtration unit. The permeate flux and retention of products were lower in the pilot equipment compared with the lab-scale setup, perhaps related to the lower Reynolds number and shear rate in the former, as indicated by simulations of computational fluid dynamics. The pilot equipment also ran at a higher volume reduction compared with the lab-scale system, which could explain the difference in flux and retention. The effects of fouling and cleaning were also determined, wherein an alkaline cleaning step (pH 11) for 1 h was sufficient to remove foulants and maintain a stable average flux of 88 L/m2h and the nonchanging retention of products.
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| 7. |
- Al-Rudainy, Basel, et al.
(author)
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Influence of prefiltration on membrane performance during isolation of lignin-carbohydrate complexes from spent sulfite liquor
- 2017
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In: Separation and Purification Technology. - : Elsevier BV. - 1383-5866. ; 187, s. 380-388
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Journal article (peer-reviewed)abstract
- In this study, we examined the isolation of lignin-carbohydrate complexes (LCCs) from sodium-based spent sulfite liquor, in conjunction with minimization of membrane fouling. We screened 3 polysulfone (PS) membranes with cutoffs of 100, 50, and 25 kDa, respectively. Flux and retention for the 100- and 50-kDa membranes had the same order of magnitude, indicating that these properties were determined by fouling that formed on the membrane—not pore size. The PS membrane with the 50-kDa cutoff performed best in terms of flux and retention of lignin-carbohydrate complexes and experienced the least membrane fouling. Two prefiltration methods were used to decrease the fouling of the 50-kDa membrane: a 0.2-μm PS microfiltration membrane and dead-end filtration with 10-um filter cloth and a 4 wt% mixture of kieselguhr (diatomite) and spent sulfite liquor prior to filtration. Prefiltration of the SSL with microfiltration increased the flux 3-fold and decreased the fouling grade from 49% to 7.2%. Dead-end filtration effected a 16% increase in flux and a fouling grade of 17%. The retention of LCC during microfiltration was high, which resulted in a loss of high-molecular-weight products, whereas the loss of LCC during dead-end filtration was negligible. A 50-kDa PS membrane performed best with regard to the recovery of lignin-carbohydrate complexes from spent sulfite liquor. Also, dead-end filtration is a promising method for eliminating membrane fouling.
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| 8. |
- Arkell, Anders, et al.
(author)
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Evaluation of membrane performance and cost estimates during recovery of sodium hydroxide in a hemicellulose extraction process by nanofiltration
- 2013
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In: Separation and Purification Technology. - : Elsevier BV. - 1873-3794 .- 1383-5866. ; 118, s. 387-393
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Journal article (peer-reviewed)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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| 9. |
- Arkell, Anders, et al.
(author)
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Influence of heat pretreatment on ultrafiltration of a solution containing hemicelluloses extracted from wheat bran
- 2013
-
In: Separation and Purification Technology. - : Elsevier BV. - 1873-3794 .- 1383-5866. ; 119, s. 46-50
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Journal article (peer-reviewed)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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| 10. |
- Bergström, Jonas, et al.
(author)
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Literature review of experimental hydrocyclone flow field studies
- 2007
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In: Separation and Purification Technology. - : Elsevier BV. - 1383-5866 .- 1873-3794. ; 53:1, s. 8-20
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Journal article (peer-reviewed)abstract
- The complex flow field of hydrocyclones has been experimentally investigated on several occasions. Most studies present similar results for the tangential velocity component. In the inner part of the cyclone, it resembles a solid-body rotation, while it typically has a free-vortex-like behavior in the outer part. When looking at the axial velocity component, the results are more diversified. Most studies show a downward velocity close to the wall and an upward velocity in the center. However, some studies report a heavily varying axial velocity over short radii close to the centerline. The radial velocity component appears to be the most problematic one to measure. Dissimilarities in measurement results between the studies are often greater than similarities. However, later studies agree on an increasing inward radial velocity towards the hydrocyclone center. Despite the obvious relationship, extremely little experimental research work can be found in the literature where changes to the flow field are connected to changes in separation efficiency.
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