| 1. |
- Baresel, Christian, et al.
(författare)
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Functionalized magnetic particles for water treatment
- 2019
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Ingår i: Heliyon. - : Elsevier BV. - 2405-8440. ; 5:8
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we have taken the concept of water treatment by functionalized magnetic particles one step forward by integrating the technology into a complete proof of concept, which included the preparation of surface modified beads, their use as highly selective absorbents for heavy metals ions (Zinc, Nickel), and their performance in terms of magnetic separation. The separation characteristics were studied both through experiments and by simulations. The data gathered from these experimental works enabled the elaboration of various scenarios for Life Cycle Analysis (LCA). The LCA showed that the environmental impact of the system is highly dependent on the recovery rate of the magnetic particles. The absolute impact on climate change varied significantly among the scenarios studied and the recovery rates. The results support the hypothesis that chelation specificity, magnetic separation and bead recovery should be optimized to specific targets and applications.
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| 2. |
- Chauhan, Vinay, 1985, et al.
(författare)
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A reverse degradation vs. temperature relationship for a carbonate-containing gemini surfactant
- 2018
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 531, s. 189-193
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Tidskriftsartikel (refereegranskat)abstract
- The rate of hydrolysis of cleavable surfactant is known to have a strong temperature dependence. A nonionic gemini surfactant with a readily hydrolysable carbonate bond as spacer unit has been synthesized and evaluated. A carbonate linkage is special as spacer unit in a gemini surfactant because the hydrolysis results in two identical molecules, in this case a hydroxy-substituted nonionic surfactant, along with carbon dioxide. The critical micelle concentration for the gemini surfactant was an order of magnitude lower than that of the degradation product. The degradation of the new surfactant and specifically the effect of temperature on the rate of hydrolysis was investigated in detail. It was found that alkaline hydrolysis was rapid at 15 °C but very slow at 30 °C, i.e. there was a reverse relationship between rate of hydrolysis and temperature. The same behavior was found for monomeric nonionic carbonate-containing surfactants that were synthesized and used as references. This unusual behavior, which can be of practical use, is explained by the reverse solubility vs. temperature profile for amphiphiles carrying a polyoxyethylene chain.
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| 3. |
- Singh, G., et al.
(författare)
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Nicotine-based surface active ionic liquids: Synthesis, self-assembly and cytotoxicity studies
- 2017
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 1095-7103 .- 0021-9797. ; 496, s. 278-289
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Tidskriftsartikel (refereegranskat)abstract
- New ester-functionalized surface active ionic liquids (SAILS) based on nicotine, [C(n)ENic][Br] (n = 8, 10 and 12), with bromide counterions have been synthesized, characterized and investigated for their self assembly behavior in aqueous medium. Conductivity measurements in aqueous solutions of the investigated SAILs have provided information about their critical micelle concentration (cmc), and degree of counterion binding (16), where cmc was found to be 2-3-fold lower than homologous SAILs or conventional cationic surfactants. The inherent fluorescence of SAILs in the absence of any external fluorescent probe have shed light on cmc as well as interactions prevailing between the monomers in micelle at molecular level. The thermodynamic parameters related to micellization have been deduced from isothermal titration calorimetry (ITC) and conductivity measurements. H-1 NMR, spin-lattice (T-1) relaxation time and 2D H-1-H-1 ROESY measurements have been exploited to get detailed account of internal structure of micelle. The size and shape of the micelles have been explored using dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements. The synthesized SAILs have been found to be non-cytotoxic towards C6-Glioma cell line, which adds to the possible utility of these SAILs for diverse biological applications.
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| 4. |
- Stjerndahl, Maria, 1975, et al.
(författare)
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Cleavable Surfactants: A Comparison between Ester, Amide, and Carbonate as the Weak Bond
- 2019
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Ingår i: Journal of Surfactants and Detergents. - : Wiley. - 1558-9293 .- 1097-3958. ; 22:5, s. 1139-1145
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Tidskriftsartikel (refereegranskat)abstract
- Cleavable surfactants, i.e., surfactants in which a weak bond has deliberately been inserted into the molecule, are of interest when remaining surface-active material at a surface can cause problems. Ester and amide bonds are established as week linkages in surfactants but these generate an acid when they hydrolyze. For some applications, acidic degradation products are unwanted. Surfactants with a carbonate bond between the polar headgroup and the hydrophobic tail are of interest for such purposes. In this article, we compare the physical–chemical properties of nonionic carbonate surfactants with those of the corresponding ester and amide surfactants. The half-lives of the different cleavable surfactants are also compared and it was found that a carbonate bond is slightly more stable to alkaline hydrolysis than an ester bond when present in otherwise identical structures. A nonionic Gemini surfactant with a carbonate bond in the spacer, which on hydrolysis decomposes into two identical single-tailed nonionic amphiphiles, is also presented. The hydrolysis kinetics for this surfactant was studied in some detail and it was found that it degrades much faster at low temperature than at higher temperature. This anti-Arrhenius type of hydrolysis kinetics is proposed to be due to the reverse solubility versus temperature behavior of ethoxylated surfactants.
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| 5. |
- Stubenrauch, Cosima, et al.
(författare)
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On how hydrogen bonds affect foam stability
- 2017
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Ingår i: Advances in Colloid and Interface Science. - : Elsevier BV. - 0001-8686. ; 247, s. 435-443
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Forskningsöversikt (refereegranskat)abstract
- Do intermolecular H-bonds between surfactant head groups play a role for foam stability? From the literature on the foam stability of various surfactants with C12 alkyl chains but different head groups a clear picture emerges: stable foams are only generated when hydrogen bonds can form between the head groups, i.e. when the polar head group has a hydrogen bond donor and a proton acceptor. Stable foams can therefore be generated with surfactants having a sugar unit, a glycine, an amine oxide (at pH ~ 5), or a carboxylic acid (at pH ~ pKa) as polar head group. On the other hand, aqueous foams stabilized with surfactants having oligo(ethylene oxide), phosphine oxide, quaternary ammonium, sulfate, sarcosine, amine oxide (at pH ? 5), or carboxylic acid (at pH ? pKa) are not very stable. These observations suggest that hydrogen bonds between neighbouring molecules at the surface enhance foam stability. Formation of hydrogen bonds between surfactant head groups gives rise to a short-range attractive interaction that may restrict the surfactant's mobility while providing a more elastic surfactant layer which can counteract deformations. To support our hypothesis we carried out a systematic foaming study of two types of surfactants, one of them being capable of forming H-bonds and the other one not. Generating foams of all surfactants mentioned above with the same foaming conditions we found that stable foams are obtained when the head group is capable of forming intersurfactant H-bonds. The outcome of this study constitutes a new step towards the implementation of H-bonds in the future design of surfactants.
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