Browsing by Subject "AQUEOUS-SOLUTION"

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  • Reischl, Bernhard; Raiteri, Paolo; Gale, Julian D.; Rohl, Andrew L. (2019)
    Advances in atomic force microscopy (AFM) in water have enabled the study of hydration layer structures on crystal surfaces, and in a recent study on dolomite (CaMg(CO3)(2)), chemical sensitivity was demonstrated by observing significant differences in force-distance curves over the calcium and magnesium ions in the surface. Here, we present atomistic molecular dynamics simulations of a hydration layer structure and dynamics on the (10 (1) over bar4) surfaces of dolomite, calcite (CaCO3), and magnesite (MgCO3), as well as simulations of AFM imaging on these three surfaces with a model silica tip. Our results confirm that it should be possible to distinguish between water molecules coordinating the calcium and magnesium ions in dolomite, and the details gleaned from the atomistic simulations enable us to clarify the underlying imaging mechanism in the AFM experiments.
  • Paavola, Anne; Bernards, Christopher M.; Rosenberg, Per H. (2016)
    In order to avoid the risks of sideeffects of epidural local anesthetics and opioids, the use of nonsteroidal anti-inflammatory drugs (NSAIDs) epidurally would be an interesting option of analgesic therapy. The fairly short duration of action of spinally administered NSAIDs, e.g., ibuprofen, may be prolonged by using controlled release poloxamer gel formulation. Using a microdialysis technique we studied the epidural and intrathecal pharmacokinetics of ibuprofen after its epidural administration as a poloxamer 407 formulation or a solution formulation. In addition, plasma ibuprofen concentrations were analyzed from central venous blood samples. Ibuprofen concentrations in the epidural space were significantly higher and longer lasting after the epidural gel injection compared with the epidural solution injection. The epidural AUC of ibuprofen was over threefold greater after epidural ibuprofen gel injection compared with the ibuprofen solution injection (p <0.001). The systemic absorption of ibuprofen from 25% poloxamer 407 gel was very low. The in situ forming poloxamer gel acted as a reservoir allowing targeted ibuprofen release at the epidural injection site and restricted ibuprofen molecules to a smaller spinal area. Ibuprofen diffusion from the epidural space to the intrathecal space was steady and prolonged. These results demonstrate that the use of epidurally injectable poloxamer gel can increase and prolong ibuprofen delivery from epidural space to the CSF enhancing thus ibuprofen entry into the central neuroaxis for spinal analgesia. Further toxicological and dose-finding studies are justified. (C) 2016 Elsevier B.V. All rights reserved.
  • Paukkonen, Heli; Kunnari, Mikko; Lauren, Patrick; Hakkarainen, Tiina; Auvinen, Vili-Veli; Oksanen, Timo; Koivuniemi, Raili; Yliperttula, Marjo; Laaksonen, Timo (2017)
    Concentrated 3% and 6.5% anionic nanofibrillar cellulose (ANFC) hydrogels were introduced as matrix reservoirs for controlled delivery applications of small molecules and proteins. A further aim was to study how the freeze-drying and subsequent rehydration of ANFC hydrogel affects the rheological properties and drug release of selected model compounds from the reconstructed hydrogels. It was demonstrated that the 3% and 6.5% ANFC hydrogels can be freeze-dried with suitable excipients into highly porous aerogel structures and redispersed back into the hydrogel form without significant change in the rheological properties. Freeze-drying did not affect the drug release properties from redispersed ANFC hydrogels, indicating that these systems could be stored in the dry form and only redispersed when needed. For large molecules, the diffusion coefficients were significantly smaller when higher ANFC fiber content was used, indicating that the amount of ANFC fibers in the hydrogel can be used to control the release rate. The release of small molecules was controlled with the ANFC fiber content only to a moderate extent. The results indicate that ANFC hydrogel can be used for controlled delivery of several types of molecules and that the hydrogel can be successfully freeze-dried and redispersed.
  • Knaapila, M.; Fonseca, S. M.; Stewart, B.; Torkkeli, M.; Perlich, J.; Pradhan, S.; Scherf, U.; Castro, R. A. E.; Burrows, H. D. (2014)
  • Knuutinen, Jenna; Bomberg, Malin; Kemell, Marianna; Lusa, Merja (2019)
    The uptake of nickel [Ni(II)] by Paenibacillus sp., Methylobacterium sp., Paraburkholderia sp., and Pseudomonas sp. strains isolated from a boreal bog was studied using batch experiments. All strains removed Ni(II) from the solution and the uptake efficiency was affected by the nutrient source, incubation temperature, time, and pH. As highest Ni uptake (with a maximum K-d of 1890 L/kg DW) was recorded for the Pseudomonas sp. strains, these bacteria were used in the following protein expression (SDS-PAGE and MALDI-TOFF), transmission electron microscopy (TEM) and EDS experiments. In addition, Freundlich and Langmuir sorption isotherms were determined. In the Ni(II) treated cells, dense crystalline intra-cellular accumulations were observed in TEM examinations, which were identified as Ni accumulations using EDS. SDS-PAGE and MALDI-TOFF spectra of Ni(II) treated cells showed several changes in the protein profiles, which can indicate active accumulation of Ni in these bacteria. Concurrently, we observed Ni(II) uptake to follow Freundlich and Langmuir isotherms, suggesting straight cellular biosorption in addition to the intra-cellular accumulation. The role of cellular (cell membrane and cell wall) functional groups involved in Ni(II) binding were therefore studied using Fourier transformation infrared spectroscopy. These analyses supported the potential role of the alcoholic hydroxyl, carboxyl and amine groups in Ni(II) binding in these bacteria, therefore suggesting two different Ni(II) uptake mechanisms; (i) intra-cellular accumulation [possibly connected to detoxification of Ni(II)], and (ii) straight biosorption on cell membrane/wall functional groups.
  • Paajanen, Johanna; Lönnrot, Satu; Heikkilä, Mikko; Meinander, Kristoffer; Kemell, Marianna; Hatanpää, Timo; Ainassaari, Kaisu; Ritala, Mikko; Koivula, Risto (2019)
    Both stable and radioactive antimony are common industrial pollutants. For antimonate (Sb(v)) removal from industrial waste water, we synthesized submicron zirconium dioxide (ZrO2) fibers by electroblowing and calcination of the as-electroblown fibers. The fibers are amorphous after calcination at 300 and 400 degrees C and their average diameter is 720 nm. The fibers calcined at 500 to 800 degrees C have an average diameter of 570 nm and their crystal structure transforms from tetragonal to monoclinic at the highest calcination temperatures. We investigated Sb(v) adsorption capacity of the synthesized ZrO2 fibers as a function of pH, adsorption isotherm at pH 6 and adsorption kinetics at pH 7. The tetragonal ZrO2 fibers calcined at 500 degrees C exhibited the best potential for Sb(v) remediation with Sb(v) uptake of 10 mg g(-1) at pH 2 and a maximum Sb(v) uptake of 8.6 mg g(-1) in the adsorption isotherm experiment. They also reached 30% of 7 days' Sb(v) uptake in only a minute. The adsorption kinetics followed the Elovich model.
  • Sánchez, Julio; Espinosa, Carolina; Pooch, Fabian; Tenhu, Heikki; Pizarro, Guadalupe del C.; Oyarzún, Diego P. (2018)
    This work is focused on the removal of Cr(VI) ions from aqueous solution using polymer-enhanced ultrafiltration (PEUF) techniques with water-soluble poly(N,N-dimethylaminoethyl methacrylate), PDMAEMA, used as sorbent. The polymer was prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization at different reaction times, characterized by size exclusion chromatography (SEC) and proton nuclear magnetic resonance (1H NMR). The sorption of Cr(VI) was studied by PEUF as a function of pH, the polymer:Cr(VI) molar ratio, and the presence of interfering ions. The PEUF-enrichment mode was used to saturate the polymer and further determine the release of Cr(VI) and regeneration of the polymer using sorption-desorption process. The RAFT polymerization showed a yield in the range 46% to 79% (determined by 1H NMR) for polymers with molecular weight (Mn) between 28 and 195 kg mol−1. The polydispersity estimated by SEC was between 1.1 and 1.8. The capacity of PDMAEMA as sorbent of Cr(VI), by the PEUF technique showed an efficient removal of Cr(VI) (100%, 25 mg L−1 in the feed) at pH 4 using polymer:Cr molar ratio of 40:1. The presence of interfering ions does not significantly decrease the retention capacity of PDMAEMA. Finally the results indicated that PDMAEMA can release Cr(VI) and be regenerated.
  • Venäläinen, Salla H.; Hartikainen, Helinä (2018)
    Treatment of acidic mining water (MW) with industrial minerals and alkaline chemicals requires utilisation of unrenewable raw materials and produces disposable inorganic sludges of no further use. We investigated the efficiency of bio-based anionic nanofibrillated cellulose (NFC) to purify authentic MW high in metals and sulphate. In a short-term (10 min) adsorption experiment, highly acidic (pH 3.2) multi-metal process water was treated with anionic NFC gels differing in their consistency (1.1%, 1.4% and 1.8% wow) at three sorbent-to-solution ratios. To unravel the purification efficiency of the NFC gels, MW was treated stepwise with a set of fresh NFC gels in three sequential batches. Each treated solution was filtrated before pH measurement and analysis for the NFC-induced changes in the metal and sulphate concentrations. All NFC gels efficiently co-adsorbed metals and sulphate and decreased the acidity of MW. Depending on the dosage, a triplicated treatment with the NFC gels removed as much as 32-75% of metal cations and 34-75% of sulphate anions. The retention of metals highly exceeded the amount of carboxyl groups in the sorbent Thus, we concluded that, instead of electrostatic adsorption, the retention took place through formation of covalent metal-NFC complexes. The subsequent surplus in positive total charge formed on the NFC-surface, in turn, enabled electrostatic co-adsorption of sulphate anions. The mutual interactions between cellulose nanofibrils in the NFC gel weakened with decreasing consistency, which promoted the accessibility of the sorption sites. This improved the purification efficiency while decreasing the demand for cellulosic raw material. We concluded that anionic NFC could potentially serve as a multifunctional and resource-efficient purification agent in the treatment of acidic process waters of high ionic strength. Ideally, the elements retained could be liberated and recycled elsewhere. (C) 2018 Elsevier Ltd. All rights reserved.
  • Venäläinen, Salla H.; Hartikainen, Helinä (2017)
    We carried out an adsorption experiment to investigate the ability of anionic nanofibrillated cellulose (NFC) to retain metal and SO42- ions from authentic highly acidic (pH 3.2) mining water. Anionic NFC gels of different consistencies (1.1%, 1.4-% and 1.8-% w/w) were allowed to react for 10 min with mining water, after which NFC-induced changes in the metal and SO42- concentrations of the mining water were determined. The sorption capacities of the NFC gels were calculated as the difference between the element concentrations in the untreated and NFC-treated mining water samples. All the NFCs efficiently co-adsorbed both metals and SO42-. The retention of metals was concluded to take place through formation of metal-ligand complexes. The reaction between the NFC ligand and the polyvalent cations renders the cellulose nanofibrils positively charged and, thus, able to retain SO42- electrostatically. Adsorption capacity of the NFC gels substantially increased upon decreasing DM content as a result of the dilution-induced weakening of the mutual interactions between individual cellulose nanofibrils. This outcome reveals that the dilution of the NFC gel not only increases its purification capacity but also reduces the demand for cellulosic raw material. These results suggest that anionic NFC made of renewable materials serves as an environmentally sound and multifunctional purification agent for acidic multimetal mining waters or AMDs of high ionic strength. Unlike industrial minerals traditionally used to precipitate valuable metals from acidic mining effluents before their permanent disposal from the material cycle, NFC neither requires mining of unrenewable raw materials nor produces inorganic sludges. (C) 2017 Elsevier B.V. All rights reserved.
  • Overton, Philip; Danilovtseva, Elena; Karjalainen, Erno; Karesoja, Mikko; Annenkov, Vadim; Tenhu, Heikki; Aseyev, Vladimir (2016)
    The present work describes the acid-triggered condensation of silicic acid, Si(OH)(4), as directed by selected polycations in aqueous solution in the pH range of 6.5-8.0 at room temperature, without the use of additional solvents or surfactants. This process results in the formation of silica-polyelectrolyte (S-PE) nanocomposites in the form of precipitate or water-dispersible particles. The mean hydrodynamic diameter (d(h)) of size distributions of the prepared water-dispersible S-PE composites is presented as a function of the solution pH at which the composite formation was achieved. Poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and block copolymers of DMAEMA and oligo(ethylene glycol) methyl ether methacrylate (OEGMA) were used as weak polyelectrolytes in S-PE composite formation. The activity of the strong polyelectrolytes poly(methacryloxyethyl trimethylammonium iodide) (PMOTAI) and PMOTAI-b-POEGMA in S-PE formation is also examined. The effect of polyelectrolyte strength and the OEGMA block on the formation of the S-PE composites is assessed with respect to the S-PE composites prepared using the PDMAEMA homopolymer. In the presence of the PDMAEMA(60) homopolymer (M-w = 9400 g/mol), the size of the dispersible S-PE composites increases with solution pH in the range pH 6.6-8.1, from d(h) = 30 nm to d(h) = 800 nm. S-PDMAEMA(60) prepared at pH 7.8 contained 66% silica by mass (TGA). The increase in dispersible S-PE particle size is diminished when directed by PDMAEMA(300) (M-w = 47,000 g/mol), reaching a maximum of d(h) = 75 nm. S-PE composites formed using PDMAEMA-b-POEGMA remain in the range d(h) = 20-30 nm across this same pH regime. Precipitated S-PE composites were obtained as spheres of up to 200 nm in diameter (SEM) and up to 65% mass content of silica (TGA). The conditions of pH for the preparation of dispersible and precipitate S-PE nanocomposites, as directed by the five selected polyelectrolytes PDMAEMA(60), PDMAEMA(300), PMOTAI(60), PDMAEMA(60)-b-POEGMA(38) and PMOTAI(60)-b-POEGMA(38) is summarized.