| 1. |
- Karlberg, Maria, et al.
(författare)
-
Mixed solutions of an associating polymer with a cleavable surfactant
- 2005
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 21:21, s. 9756-9763
-
Tidskriftsartikel (refereegranskat)abstract
- Mixtures of hydrophobically modified hydroxyethyl cellulose (HMHEC) and alkali-sensitive cleavable betaine ester surfactants have been studied by viscometry, H-1 NMR, absorbance measurements, and birefringence determinations. Before the hydrolysis, the surfactants behaved as conventional nondegradable surfactants in terms of the effect on the viscosity of increasing surfactant concentration. As the surfactants were hydrolyzed, systems with time-dependent viscosity were obtained. The viscosity either decreased monotonically or went through a maximum as a function of time, depending on the initial surfactant concentration. Different surfactant chain lengths gave rise to different viscosity profiles. The rate of hydrolysis, and thus the time-dependency of the surfactant concentration, could be controlled by changing the pH of the solution.
|
|
| 2. |
- Egermayer, Monica, et al.
(författare)
-
Gels of hydrophobically modified ethyl (hydroxyethyl) cellulose cross-linked by amylose: Effects of hydrophobe architecture
- 2004
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 20:6, s. 2208-2214
-
Tidskriftsartikel (refereegranskat)abstract
- Previous work has shown that amylose (AM) can cross-link hydrophobically modified polymers by inclusion complexation, whereby thermoreversible cold-setting gels are formed. Here we investigate the complexation of AM with different samples of hydrophobically modified ethyl(hydroxyethyl) cellulose (HMEHEC), distinguished by differences in the architecture of the hydrophobes (the hydrophobic side chains). All hydrophobes, except one, were based on linear alkyl chains, but with varying chain lengths (C-12-C-14). In addition, some samples contained short hydrophilic "spacers", consisting of 2-5 ethylene oxide units, between the alkyl chains and the EHEC backbone. Gels of varying strength were obtained for the different AM/HMEHEC samples. The alkyl chain length seemed to be the major factor affecting the gel strength, with longer alkyl chains giving stronger gels. For similar alkyl chain lengths, stronger gels were obtained when a spacer was present. Addition of AM caused a small increase of the cloud points of HMEHECs with C-14 hydrophobes in water. Time-dependent effects and effects of the sample preparation procedure were also investigated. The reversibility of the gelation with respect to shear was confirmed. A gel destroyed by added surfactant was shown to reform on removal of the surfactant by dialysis.
|
|
| 3. |
- Karlberg, Maria, et al.
(författare)
-
Gels of hydrophobically modified hydroxyethyl cellulose cross-linked by amylose. Competition with cyclodextrin
- 2006
-
Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 22:5, s. 2241-2248
-
Tidskriftsartikel (refereegranskat)abstract
- Previous work has shown that amylose (AM) can cross-link hydrophobically modified polymers by inclusion complexation, whereby thermoreversible cold-setting gels are formed. In this work, the competition between AM and cyclodextrin (CD) for the formation of inclusion complexes with hydrophobically modified hydroxyethyl cellulose (HMHEC) is investigated. A detailed study of viscosity, NMR self-diffusion, and chemical shifts of the two-component mixture, CD and HMHEC, was performed. The results imply that 2:1 (CD:polymer hydrophobe) complexes may be formed. The three-component mixtures, HMHEC/AM/CD, were investigated by rheology, NMR self-diffusion, and intensities of the NMR resonance peaks. The CD molecules competed efficiently with the AM molecules, as seen by a decreased storage modulus, an increased self-diffusion of AM and HMHEC, and increased NMR intensities of the HMHEC hydrophobes, as the concentration of CD increased in the solution. A high concentration of CD is needed in the mixtures to inhibit all interactions between HMHEC and AM, and it was shown that there still is an effect of AM at excess CD concentration in the mixtures.
|
|
| 4. |
- Karlberg, Maria, et al.
(författare)
-
Mixed solutions of hydrophobically modified graft and block copolymers
- 2004
-
Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - : Elsevier BV. - 0927-7757. ; 236:1-3, s. 159-164
-
Tidskriftsartikel (refereegranskat)abstract
- Phase separation temperatures and viscosities of dilute and semidilute aqueous mixtures of hydrophobically modified graft and block copolymers have been studied. The graft copolymer was hydrophobically modified ethyl(hydroxyethyl)cellulose (HM-EHEC), and the block copolymers were hydrophobically modified poly(ethylene glycol) (HM-PEG) with diblock (DB) or triblock (TB) structures, i.e., modified at one or both ends, respectively. For comparison, viscosity measurements were made also on mixtures of TB with HM-HEC, and on systems where one of the polymers was unmodified (i.e. HM-EHEC/PEG or TB/EHEC). All results indicate mixed hydrophobic associations between graft and block copolymers. Moderate viscosity enhancements were found on addition of HM-PEG to HM-EHEC, and the effects were larger for TB than for DB. The viscosity changes were quite sensitive to the concentration of HM-EHEC. (C) 2004 Elsevier B.V. All rights reserved.
|
|
| 5. |
- Karlberg, Maria, et al.
(författare)
-
Solubility of amylose/ionic surfactant complexes in dilute aqueous solutions: Dependence on surfactant concentration
- 2007
-
Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617. ; 70:3, s. 350-354
-
Tidskriftsartikel (refereegranskat)abstract
- The solubility in dilute aqueous solutions of amylose complexed with ionic surfactants has been investigated by turbidity measurements. The turbidity depended on both the amylose and the surfactant concentrations. Low and high surfactant concentrations resulted in macroscopic phase separation, while mixtures at intermediate surfactant concentrations remained monophasic for at least one month. The solubility of the complexes was sensitive to the addition of salt as well as to the surfactant charge and hydrophobic chain length. These results are interpreted in terms of an electrostatic stabilisation of soluble complexes. Complexes with a non-ionic surfactant were not soluble at any mixing ratio. (c) 2007 Elsevier Ltd. All rights reserved.
|
|
| 6. |
- Percebom, Ana Maria, et al.
(författare)
-
Micellization of Water-Soluble Complex Salts of an Ionic Surfactant with Hairy Polymeric Counterions
- 2013
-
Ingår i: Soft Matter. - 1744-6848. ; 9, s. 515-526
-
Tidskriftsartikel (refereegranskat)abstract
- For ionic surfactants in general, a change from simple to polymeric counterions leads to increasing attraction between micelles, condensing them in a concentrated phase. In the present study, two novel “complex salts” were prepared in which the cationic surfactant hexadecyltrimethylammonium was neutralized by two different copolyions, both having poly(methacrylate) main chains randomly decorated with oligo(ethylene oxide) side chains. The presence of hydrophilic side chains in the polyion backbone is proposed as a strategy to stabilize the complex salt aggregates in aqueous solutions and prevent them from separating out in a concentrated phase. Surface tension experiments reveal that the complex salts form soluble nano-aggregates by surfactant ion self-assembly at a distinct critical micellization concentration (cmc), similar to the micellization of a conventional ionic surfactant. This is the first time that cmc values have been determined for complex salts in the absence of all other ions. The physicochemical nature of the aggregates formed was investigated by dynamic light scattering, nuclear magnetic resonance self-diffusion measurements and steady-state fluorescence spectroscopy. Much larger aggregates are formed when the temperature is increased, but the small aggregates reform at room temperature, suggesting that the soluble aggregates are equilibrium structures, much like the micelles of conventional surfactants.
|
|
| 7. |
- Percebom, Ana Maria, et al.
(författare)
-
Polyion-Surfactant Ion Complex Salts Formed by a Random Anionic Copolyacid at Different Molar Ratios of Cationic Surfactant: Phase Behavior with Water and n-Alcohols
- 2012
-
Ingår i: The Journal of Physical Chemistry Part B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 116:8, s. 2376-2384
-
Tidskriftsartikel (refereegranskat)abstract
- The presence of acid groups with different pK(a) values in the anionic copolymer poly(4-styrene sulfonic acid-co-maleic acid), P(SS-Ma), allowed the preparation of complex salts with a variable fraction of anionic groups neutralized by cationic surfactant in the copolymer via controlled titration with hexadecyltrimethylammonium hydroxide, C(16)TAOH. Two new complex salts were selected for detailed phase studies, C(16)TA(2)P-(SS-Ma) and C(16)TA(3)P(SS-Ma), where both had 100% charged styrene sulfonate groups, but the fraction of charged carboxylate groups on the polyion was 50% or 100%, respectively. These complex salts thus contained both hydrophobic (styrene sulfonate) and hydrophilic (carboxylate) charged groups, and the ratio between the two could be altered by titration. These features were found to have consequences for the phase behavior in water and in ternary mixtures with water and n-alcohols for the two complex salts, which differed compared to complex salts containing homo- or copolyions with only carboxylate or styrene sulfonate charged groups. For both complex salts, binary mixtures with water produced, in the dilute region, two isotropic phases in equilibrium, the bottom (concentrated) one displaying increasing viscosity with increasing concentration. For the complex salt C(16)TA(2)P(SS-Ma), there was evidence of micellar growth to form anisometric aggregates at high concentrations. For the C(16)TA(3)P(SS-Ma) complex salt, this was not observed, and the isotropic phase was followed by a narrow region of cubic phase. In both cases, concentrations above ca. 60 wt % produced a hexagonal phase. For ternary mixtures with n-alcohols, the general trend was that a short-chain alcohol such as n-butanol acted as a cosolvent dissolving the aggregates, whereas with n-decanol, a cosurfactant effect was observed, inducing the formation of lamellar phases. Visual inspection (also between crossed polarizers), small angle X-ray scattering (SAXS) and diffusion nudear magnetic resonance (NMR) were used in these studies.
|
|
| 8. |
- Piculell, Maria, et al.
(författare)
-
Evaluating the Effect of Biofilm Thickness on Nitrification in Moving Bed Biofilm Reactors.
- 2015
-
Ingår i: Environmental Technology. - : Informa UK Limited. - 1479-487X .- 0959-3330. ; :Online 21 August 2015, s. 1-28
-
Tidskriftsartikel (refereegranskat)abstract
- This study evaluates the effect of biofilm thickness on the nitrifying activity in moving bed biofilm reactors (MBBRs) in a controlled environment. In-depth understanding of biofilm properties in MBBRs and their effect on the overall treatment efficiency compose the key to optimizing process stability and efficiency. However, evaluating biofilm properties in continuously operated MBBRs can be extremely challenging. This study uses a carrier design which enables comparison of four different biofilm thicknesses, in otherwise equally operated lab-scale MBBRs. The results show that, within the studied range (200-500 µm) and specific operation conditions, biofilm thickness alone had no significant effect on the overall ammonium removal. The nitrate production, however, decreased with a decreasing biofilm thickness, and the ratio between nitrite and ammonia oxidizing activity decreased both with increasing load and decreasing oxygen concentration for all thicknesses. The suggestion that nitratation is disfavored in thin biofilms is an interesting contribution to current research being performed on NOB inhibition for deammonification applications. By indicating that different groups of bacteria respond differently to biofilm thickness, this study accentuates the importance of further evaluation of these complex systems.
|
|
| 9. |
- PICULELL, MARIA
(författare)
-
New Dimensions of Moving Bed Biofilm Carriers : Influence of biofilm thickness and control possibilities
- 2016
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The moving bed biofilm reactor (MBBR) is a biological wastewater treatment process in which microorganisms grow as biofilms on suspended carriers. Conventionally, MBBRs are mainly designed and optimized based on the carrier surface area, neglecting the dynamic relationship between carrier design, reactor operation and biofilm characteristics, such as biofilm thickness and the composition of the microbial community. The purpose of this research project was to learn more about the roles of the biofilm carriers in the MBBR process, with the intention to improve process performance and develop new MBBR applications. In doing so, the MBBR performance was evaluated in several lab studies, considering different aspects such as carrier design and operational strategies. A new carrier type, the Z-carrier, was developed, with which it was possible to control the biofilm thickness in the MBBR. Hence, the Z-carrier enabled the evaluation of having different, pre-defined biofilm thicknesses in the MBBR process, something that has not previously been achievable. This thesis shows that biofilm thickness control can be used to ensure a more stable process performance as well as to avoid carrier clogging and minimize issues with biofilm scaling that may have detrimental effects on the MBBR performance. It was also shown that the microbiology in biofilms can be altered by biofilm thickness control. Based on these findings, a novel process configuration was developed, showing that successful nitritation of mainstream municipal wastewater could be achieved when combining thin, controlled biofilms with a periodic exposure of the biofilm to reject water from sludge dewatering. Finally, the role of suspended biomass in the MBBR was evaluated in relation to carrier surface area, HRT and loading rate, showing that the suspended biomass can have a considerable effect on the overall process performance, and that the design of MBBRs should not always be solely based on biofilm surface area. For future studies, the potential of using biofilm thickness as a control parameter for the MBBR should be investigated further, especially for specific microbial applications such as nitritation and anammox, and the importance of suspended biomass in the MBBR should be studied in relation to the settling characteristics of the excess sludge.
|
|
| 10. |
- Piculell, Maria, et al.
(författare)
-
Organic removal activity in biofilm and suspended biomass fractions of MBBR systems.
- 2014
-
Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 69:1, s. 55-61
-
Tidskriftsartikel (refereegranskat)abstract
- The moving bed biofilm reactor (MBBR) wastewater treatment process is usually designed based on the assumption that all activity in the process occurs in the biofilm on the MBBR carriers, although there is always some active biomass in the bulk liquid due to biofilm sloughing and, sometimes, free-growing bacteria. In this study the removal of organic matter is evaluated in laboratory-scale MBBR reactors under varying load, hydraulic retention time (HRT), oxygen concentration and volumetric filling degree of carriers in order to determine the heterotrophic activity in the different fractions of the MBBR biomass. The results showed that the heterotrophic conversions in an MBBR can show the same type of diffusion limited dependency on oxygen as nitrification, even for easily degradable substrates such as acetate. The contribution to the removal from the suspended biomass is shown to vary depending on HRT, as the amount of suspended solids changes. The developed method in this report is a useful tool for determining heterotrophic activity in the separate fractions of biomass in MBBRs.
|
|
