Release Of Sulfate Research Articles

Long-term Release of Sulfate From Building Rubble–Composed Soil

High sulfate concentrations in the groundwater occur in several cities and particularly in Berlin, Germany. Building rubble–composed soils and landfills are a major source of dissolved sulfates. This study assesses the sulfate release dynamics of such rubble-composed substrates. The substrate was taken from a building rubble landfill in Berlin, which was created after World War II. It was poured into two lysimeters, which were irrigated repeatedly for 2 years to simulate several years of groundwater recharge. Sulfate concentration in the leachate was measured monthly. Sulfate release dynamics were effectively described with PHREEQC, assuming either one or two sulfate pools with kinetically limited dissolution. The volume that percolated the lysimeter column was 2,440 L, corresponding to 17 years of local groundwater recharge. At the beginning, sulfate concentrations increased from approximately 10·10−3 mol ·L−1 to 13·10−3 mol · L−1, which is close to gypsum solubility concentration. After 1.8 pore volumes, a decrease was observed, and after 8 pore volumes, concentrations were relatively constant at levels less than 3·10−3 mol · L−1. The data were best described by a model that included a kinetically limited dissolution of gypsum from two sulfate pools different in their effective surface areas. One pool can be ascribed to fine-grained gypsum particles, whereas the other can be ascribed to coarse-grained ones. Overall, rubble-composed substrates can be a severe long-term source of sulfates.

In situ Cross-linked Matrix Tablets for Sustained Salbutamol Sulfate Release: Formulation Development by Statistical Optimization

In situ Cross-linked Matrix Tablets for Sustained Salbutamol Sulfate Release: Formulation Development by Statistical Optimization

Dynamic Release of Antibiotic Drug Gentamicin Sulfate from Novel Zirconium Phosphate Nano-Platelets

Dynamic Release of Antibiotic Drug Gentamicin Sulfate from Novel Zirconium Phosphate Nano-Platelets

Polyelectrolyte complexes of poly[(2-dimethylamino) ethyl methacrylate]/chondroitin sulfate obtained at different pHs: I. Preparation, characterization, cytotoxicity and controlled release of chondroitin sulfate

For the first time, polyelectrolyte complex based on poly[(2-dimethylamino) ethyl methacrylate] (PDMAEMA) and chondroitin sulfate (CS) was prepared. The properties of novel material and precursors were investigated by WAXS, FTIR, TGA, SEM and DLS analysis. The PDMAEMA/CS PECs presented hydrophilic–hydrophobic transition at pHs 6.0, 7.0 and 8.0 whereas the non-complexed PDMAEMA showed such a transition at pH 8.0 and not at pHs 6.0 and 7.0. Studies of CS release from PECs at pHs 6 and 8 confirmed that the samples possess the potential to release the CS in alkaline and not in acidic conditions. Since PECs are thermo-responsive due to the reduction of LCST caused by the increase in pH, the release of CS was dependent on temperature and pH factors. Cytotoxicity assays using healthy VERO cells showed that the complexation between CS and PDMAEMA increased the PECs' biocompatibility related to PDMAEMA. However, the biocompatibility depends on the amount of CS present in the PECs.

Lepidocrocite Formation Kinetics from Schwertmannite in Fe(II)-Rich Anoxic Alkaline Medium

Effect of dissolved ferrous iron [Fe(II)aq = 0–1.0 mM] on stability of schwertmannite containing ≈40 wt% Fe(III) and 15 wt% SO4 2− [with and without 0.92 wt% sorbed As(III)] was investigated in anoxic alkaline conditions at pH 8 for 154 h. New product formation, sulfate, iron, and arsenic release kinetics were examined using diffractogram, microscopic, spectroscopic and geochemical techniques. Both schwertmannite types were incompletely transformed to lepidocrocite with a platy tabular morphometry. Product formation was accelerated with increased Fe(II)aq, while sorbed As(III) markedly hindered lepidocrocite formation. Almost 50–57 % of the SO4 2− was released from schwertmannite within 154 h in the absence of Fe(II)aq, while its presence inhibited its release. Some of the sorbed As(III) was released during lepidocrocite formation with a maximum in the presence of 1.0 mM Fe(II)aq (0.02 %, 21 µg L−1), presumably due to catalytic action of Fe(II)aq on schwertmannite dissolution, which likely re-precipitated as lepidocrocite with considerable surface-adsorbed SO4 2−.

Cationic spin probe reporting on thermal denaturation and complexation-decomplexation of BSA with SDS. Potential applications in protein purification processes.

In this work, we present evidence on the suitability of spin probes to report on the thermal treatment of bovine serum albumin (BSA), in the temperature range 293-343 K, and indirectly monitor the release of sodium dodecyl sulfate (SDS) from its complex with BSA using a covalent gel with β-cyclodextrin (β-CD) in the network. The spin probes used, 5- and 7-doxyl-stearic acids (5-DSA, 7-DSA) or 4-(N,N'-dimethyl-N-hexadecyl)ammonium-2,2',6,6'-tetramethylpiperidine-1-oxyl iodide (CAT16), present similar, fatty acid-like structural features. Their continuous wave electron paramagnetic resonance (CW-EPR) spectra, however, reflect different dynamics when complexed with BSA: a restricted motion for 5-DSA, almost nonsensitive to the heating/cooling cycle, and a faster temperature-dependent dynamic motion for CAT16. Molecular docking allows us to rationalize these results by revealing the different binding modes of 5-DSA and CAT16. The EPR data on the temperature effect on BSA are supported by circular dichroism results projecting recovery, upon cooling, of the initial binding ability of BSA for samples heated to 323 K. The interactions occurring in BSA/SDS/β-CD systems are investigated by CW-EPR and FT-ESEEM spectroscopies. It is found that the covalent gel containing β-CD can efficiently remove SDS from the BSA/SDS complex. The gel is not permeable to BSA but it can encapsulate SDS, thus yielding the free protein in solution and allowing recovery of the native protein conformation. Collectively, the accrued knowledge supports potential applications in protein purification biotechnological processes.

Quinapyramine Sulfate-Loaded Sodium Alginate Nanoparticles Show Enhanced Trypanocidal Activity

To reduce the dose, toxic effects and to ensure sustained release of quinapyramine sulfate (QS), a highly effective drug against Trypanosoma evansi. QS-loaded sodium alginate nanoparticles (QS-NPs) were formed by emulsion-crosslinking technology using dioctyl-sodium-sulfosuccinate and sodium alginate. The formulation was characterized for size, stability, morphology and functional groups by a zetasizer, scanning electron microscopy, atomic force microscopy, transmission electron microscopy and Fourier transform infrared spectroscopy. In vitro safety and toxicity studies were performed by metabolic assay in Vero cell lines, and in vivo efficacy was evaluated in mice. QS-NPs were <60 nm with 96.48% entrapment efficiency and 3.70% drug loading. The formulation showed an initial burst effect followed by slow drug release in accordance with quasi-Fickian Higuchi diffusion mechanism. QS-NPs were much less toxic and able to clear the parasite at a much lower concentration than QS. The QS-NPs synthesized are safe, less toxic and highly effective compared with QS.

The impact of biostimulation on the fate of sulfate and associated sulfur dynamics in groundwater

The impact of electron-donor addition on sulfur dynamics for a groundwater system with low levels of metal contaminants was evaluated with a pilot-scale biostimulation test conducted at a former uranium mining site. Geochemical and stable-isotope data collected before, during, and after the test were analyzed to evaluate the sustainability of sulfate reducing conditions induced by the test, the fate of hydrogen sulfide, and the impact on aqueous geochemical conditions. The results of site characterization activities conducted prior to the test indicated the absence of measurable bacterial sulfate reduction. The injection of an electron donor (ethanol) induced bacterial sulfate reduction, as confirmed by an exponential decrease of sulfate concentration in concert with changes in oxidation–reduction potential, redox species, alkalinity, production of hydrogen sulfide, and fractionation of δ34S-sulfate. High, stoichiometrically-equivalent hydrogen sulfide concentrations were not observed until several months after the start of the test. It is hypothesized that hydrogen sulfide produced from sulfate reduction was initially sequestered in the form of iron sulfides until the exhaustion of readily reducible iron oxides within the sediment. The fractionation of δ34S for sulfate was atypical, wherein the enrichment declined in the latter half of the experiment. It was conjectured that mixing effects associated with the release of sulfate from sulfate minerals associated with the sediments, along with possible sulfide re-oxidation contributed to this behavior. The results of this study illustrate the biogeochemical complexity that is associated with in-situ biostimulation processes involving bacterial sulfate reduction.

Surface modified nano-zeolite used as carrier for slow release of sulphur

Surface modified nano-zeolite (SMNZ) was used as carrier to develop nano-zeolite based nano-sulphur fertilizer. A laboratory study on sulphur nano-fertilizer and conventional sulphur fertilizer were studied with percolation reactor system to evaluate the slow release of sulphur from both fertilizers in ambient temperature. SMNZ and sulphur nano-fertilizer were characterized using Fourier Transform Infrared Spectroscopy (FT-IR), Zeta Analyzer, Raman Spectroscopy, XRD and Scanning Electron Microscope (SEM). Raman spectroscopy confirmed the sulphur attachment at 480 cm-1 in the SMNZ. The FTIR spectra at 1030 cm-1 confirmed the sulphate attachments in the SMNZ spectrum. Zeta analyzer showed the surface charge of sulphur nano-fertilizer had (-) 52.6 mV. SEM imaged the sulphur loaded SMNZ in irregular flake like structure. A comparative study of the release of sulphate (SO4 2-) from fertilizer-loaded SMNZ and (NH4)2 SO4 fertilizers were performed using the percolation reactor. The results showed that the SO42- supply from fertilizer-loaded SMNZ was available even after 912 h of continuous percolation, whereas SO42- from (NH4)2 SO4 was exhausted within 384 h. These properties suggest that SMNZ has a great potential as the fertilizer carrier for slow release of SO42-.

In vitro, in vivo and pharmacokinetic assessment of amikacin sulphate laden polymeric nanoparticles meant for controlled ocular drug delivery

The rationale of current exploration was to formulate positively charged amikacin-loaded polymeric nanoparticles providing a controlled release attribute. Amikacin sulphate-loaded nanoparticles were prepared by w/o/w emulsification solvent evaporation approach succeeded by high-pressure homogenization. Two bioadhesive positively charged polymers, Eudragit® RS 100 and Eudragit® RL 100, were used in the blend, with variable ratios of drug and polymer. The formulations were assessed in terms of particle size and zeta potential. Thermal gravimetric analysis was brought out on the samples of drug, polymer and drug polymer complex. Drug loading and release attributes of the nanoparticles were scrutinized and antimicrobial activity in contrast to Staphylococcus aureus was appraised. Ocular irritation test, in vivo ocular retention study, in vivo release profile (permeation study) and in vivo antibacterial activity of polymeric nanosuspensions were executed. No rupture consequence but a lengthened drug release was contemplated from all formulations. Amikacin sulphate release from the polymeric nanoparticles reflected a better fit with Korsmeyer–Peppas model. In the course of the antibacterial activity of nanoparticles against S. aureus, formulation AE1 displays the most prominent inhibitory effect as compared with marketed formulation of amikacin sulphate.

Short period of oxygenation releases latch on peat decomposition

Extreme summer droughts are expected to occur more often in the future in NW Europe due to climate change. These droughts might accelerate the rate of peat oxidation in drained peat areas, with impacts on soil subsidence, GHG emission and water quality. This study aimed at providing more insight in the oxidation of deep peat layers that had not previously been exposed to air, the so-called secondary decomposition.We incubated two types of peat (eutrophic and oligotrophic), sampled from permanently anoxic peat layers from nature reserves and agricultural peat meadows. Peat samples were incubated for thirteen weeks under anoxic conditions, but were exposed to air for one to eight weeks. The production of CO2 and CH4 was quantified as a proxy for decomposition; concentrations of soluble nutrients and phenolic compounds were also measured.The results showed that oxygenation led to a steep increase in the rate of decomposition, indicated by higher carbon loss rates during and after oxygenation compared to non-oxygenated samples. Carbon loss rates increased more for eutrophic peat (agricultural area: 352%, nature reserve: 182%) than for oligotrophic peat (83% and 159% respectively). Most peat samples investigated showed higher post-oxygenation CO2 and/or CH4 production compared to the anoxic pre-oxygenation period. This indicates that oxygenation stimulates decomposition, even after anoxic conditions have returned. Contrary to the enzymic latch theory, no effects of oxygenation on the concentrations of soluble or condensed phenolic compounds were detected. Soluble nutrient concentrations did not change due to oxygenation either. Noteworthy is the occurrence of pyrite mineralization and associated acidification in eutrophic peat. Thus, low summer water levels, for example due to climate change, should be avoided in order to limit exceptionally high decomposition rates and associated problems such as increasing subsidence rates, greenhouse gas emission, sulfate release and acidification.

Cyclical salt efflorescence weathering: an invisible threat to the recovery of underground mine environment for tourist exploitation

Enhancing the value of an underground mine environment for tourist exploitation involves altering the physico-chemical balance of stone materials whose original mechanical properties guaranteed the structural stability of the site’s galleries and chambers. Humidity and temperature changes caused by the public exhibition of this kind of assets are the main causes of such disorders. After the intervention in the Agrupa-Vicenta mine in La Union (Spain) there were still runoff-water leaks into the mine. These water runoffs through the fault and schistosity planes of the enclosing rock mass give rise to salt precipitation over time. Adapting this mine and turning it into a museum have meant a decrease in relative indoors humidity and an increase in temperature. These variations have caused rocks, which were stable in the original conditions, to increase their rate of physico-chemical weathering due to the polycyclic supergene alteration of the metal sulfides they contain. The resulting release of sulfates into the solution and their subsequent precipitation as single and double salt efflorescence causes haloclasty, deteriorating the rock’s mechanical properties and diminishing the structural stability of the operation. This paper presents the results of characterizing the supergene mineral phases of salt efflorescence in the rock bed enclosing an underground sulfide mine value enhanced for tourist exploitation. Dangers for the structural stability of this type of architectural intervention, associated to the formation of efflorescences, are also identified; these efflorescences are caused by the weathering of rocks that make up its supporting structure.

Comparison of Particle Mass and Solid Particle Number (SPN) Emissions from a Heavy-Duty Diesel Vehicle under On-Road Driving Conditions and a Standard Testing Cycle

It is important to understand the differences between emissions from standard laboratory testing cycles and those from actual on-road driving conditions, especially for solid particle number (SPN) emissions now being regulated in Europe. This study compared particle mass and SPN emissions from a heavy-duty diesel vehicle operating over the urban dynamometer driving schedule (UDDS) and actual on-road driving conditions. Particle mass emissions were calculated using the integrated particle size distribution (IPSD) method and called MIPSD. The MIPSD emissions for the UDDS and on-road tests were more than 6 times lower than the U.S. 2007 heavy-duty particulate matter (PM) mass standard. The MIPSD emissions for the UDDS fell between those for the on-road uphill and downhill driving. SPN and MIPSD measurements were dominated by nucleation particles for the UDDS and uphill driving and by accumulation mode particles for cruise and downhill driving. The SPN emissions were ∼ 3 times lower than the Euro 6 heavy-duty SPN limit for the UDDS and downhill driving and ∼ 4-5 times higher than the Euro 6 SPN limit for the more aggressive uphill driving; however, it is likely that most of the "solid" particles measured under these conditions were associated with a combination release of stored sulfates and enhanced sulfate formation associated with high exhaust temperatures, leading to growth of volatile particles into the solid particle counting range above 23 nm. Except for these conditions, a linear relationship was found between SPN and accumulation mode MIPSD. The coefficient of variation (COV) of SPN emissions of particles >23 nm ranged from 8 to 26% for the UDDS and on-road tests.

Chitosan hydrogels for chondroitin sulphate controlled release: an analytical characterization.

This paper provides an analytical characterization of chitosan scaffolds obtained by freeze-gelation toward the uptake and the controlled release of chondroitin sulphate (CS), as cartilage repair agent, under different pH conditions. Scanning electron microscopy (SEM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and liquid chromatography-UV spectrophotometry (LC-UV) techniques were exploited to obtain qualitative and quantitative descriptions of polymer and drug behaviour in the biomaterial. As for morphology, SEM analysis allowed the evaluation of scaffold porosity in terms of pore size and distribution both at the surface (Feret diameter 58 ± 19 μm) and on the cross section (Feret diameter 106 ± 51 μm). LC and ATR-FTIR evidenced a pH-dependent CS loading and release behaviour, strongly highlighting the role of electrostatic forces on chitosan/chondroitin sulphate interactions.

In vitro dissolution and in vivo gamma scintigraphic evaluation of press-coated salbutamol sulfate tablets

The aim of this study was to investigate the in vitro and in vivo performance of salbutamol sulfate press-coated tablets for delayed release. The in vitro release behavior of press-coated tablets with the outer layer of PEG 6000/ Eudragit S100 blends (2:1) in pH 1.2 (0.1 mol L-1 HCl) and then pH 6.8 buffer solution was examined. Morphological change of the press-coated tablet during in vitro release was recorded with a digital camera. Release of salbutamol sulfate from press-coated tablets was less than 5 % before 3 h and was completed after 8 h in pH 6.8 phosphate buffer solution. In vivo gamma scintigraphy study carried out on healthy men indicated that the designed system released the drug in lower parts of the GI tract after a lag time of 5 hours. The results showed the capability of the system of achieving delayed release of the drug in both in vitro and in vivo gamma scintigraphy studies.

Treatment of synthetic acid mine drainage using rice wine waste as a carbon source

Spent mushroom compost (SMC) is commonly used as a carbon source for passive treatment systems in South Korea; however, it has some drawbacks, such as sulfate release from itself. Consequently, investigations to identify effective substitutes for SMC are necessary. In this study, batch experiments were conducted for 27 days to evaluate the efficiency of rice wine waste (RWW) for reducing sulfate and removing dissolved metals within synthetic acid mine drainage (AMD). The results showed that RWW could be more suitable than SMC, which even released sulfate in the early stage of the experiment, for sulfate reduction by sulfate-reducing bacteria. Both materials produced similar results with respect to the removal of dissolved metals, such as Fe and Al. Furthermore, a mixture of SMC and RWW showed the greatest efficiency in sulfate removal. Overall, both RWW and the mixed carbon source showed comparable performance to SMC, which indicated that RWW had a great potential for use as a carbon source for AMD treatment.

Radiation Effects on the Performance of Proton Exchange Membranes in Electrochemical Cells

Proton exchange membranes (PEMs) are being studied for tritium separation applications involving electrochemical processes. The effects of γ- and β-radiation on Nafion 112 membrane are discussed in this paper. The fluoride and sulfate release from Nafion 112 membrane increases with increase in γ-dose. Oxygen promotes the total organic carbon (TOC) release while hydrogen suppresses sulfur release. A β-radiation dose of 200 kGy from tritium causes minor damage to the membrane, comparable to the effect of γ-radiation at similar dose. The FTIR spectrum of tritium-exposed membranes is similar to that of the reference samples except for a weak peak of C=O stretch observed at 1740 cm-1. The conductivity and electrochemical performance of the tritium-exposed and reference membrane samples are not significantly different during the fuel cell and water electrolysis tests. It is believed that β-radiation is likely to attack the carbon chain in Nafion 112 membrane.

Model-Based Integration and Analysis of Biogeochemical and Isotopic Dynamics in a Nitrate-Polluted Pyritic Aquifer

Leaching of nitrate from agricultural land to groundwater and the resulting nitrate pollution are a major environmental problem worldwide. Its impact is often mitigated in aquifers hosting sufficiently reactive reductants that can promote autotrophic denitrification. In the case of pyrite acting as reductant, however, denitrification is associated with the release of sulfate and often also with the mobilization of trace metals (e.g., arsenic). In this study, reactive transport modeling was used to reconstruct, quantify and analyze the dynamics of the dominant biogeochemical processes in a nitrate-polluted pyrite-containing aquifer and its evolution over the last 50 years in response to changing agricultural practices. Model simulations were constrained by measured concentration depth profiles. Measured (3)H/(3)He profiles were used to support the calibration of flow and conservative transport processes, while the comparison of simulated and measured sulfur isotope signatures acted as additional calibration constraint for the reactive processes affecting sulfur cycling. The model illustrates that denitrification largely prevented an elevated discharge of nitrate to surface waters, while sulfate discharges were significantly increased, peaking around 15 years after the maximum nitrogen inputs.

Controlled release of Capreomycin sulfate from pHresponsive nanocapsules

Abstract The synthesis of polymeric nanocapsules loaded with the antituberculosis drug Capreomycin sulphate is presented in this work. The pHresponsive polymeric nanocapsules were successfully synthesized using the RAFT-based vesicle templating approach in the presence of Capreomycin sulphate. Anionic small polyelectrolytes comprising randomly distributed butyl acrylate and acrylic acid units were adsorbed on cationic vesicles of dimethyldioctadecyl ammonium bromide (DODAB). N,N-(dimethylamino)ethyl methacrylate (DMAEMA) and methyl methacrylate (MMA) or tertiary butyl methacrylate (tBMA) and MMA were used for the formation of the polymeric shells. Subsequently the tBMA was hydrolyzed to obtain negatively charged nanocapsules. The nanocapsule morphology for both approaches was characterized by DLS and TEM. The most stable hollow latex particles were obtained with the monomer composition of DMAEMA:MMA = 1:1. These nanocapsules were found to be colloidally stable and pH-responsive. The entrapment efficiency of drug determined by UV-Vis-spectroscopy was 70 %. The drug release rate from nanocapsules at pH 6.5 was found to be relatively fast (substantial release within one hour already), however we believe slower release can be achieved by using a thicker polymer shell.

In vitro bioactivity, cytocompatibility, and antibiotic release profile of gentamicin sulfate-loaded borate bioactive glass/chitosan composites

Borate bioactive glass-based composites have been attracting interest recently as an osteoconductive carrier material for local antibiotic delivery. In the present study, composites composed of borate bioactive glass particles bonded with a chitosan matrix were prepared and evaluated in vitro as a carrier for gentamicin sulfate. The bioactivity, degradation, drug release profile, and compressive strength of the composite carrier system were studied as a function of immersion time in phosphate-buffered saline at 37 °C. The cytocompatibility of the gentamicin sulfate-loaded composite carrier was evaluated using assays of cell proliferation and alkaline phosphatase activity of osteogenic MC3T3-E1 cells. Sustained release of gentamicin sulfate occurred over ~28 days in PBS, while the bioactive glass converted continuously to hydroxyapatite. The compressive strength of the composite loaded with gentamicin sulfate decreased from the as-fabricated value of 24 ± 3 MPa to ~8 MPa after immersion for 14 days in PBS. Extracts of the soluble ionic products of the borate glass/chitosan composites enhanced the proliferation and alkaline phosphatase activity of MC3T3-E1 cells. These results indicate that the gentamicin sulfate-loaded composite composed of chitosan-bonded borate bioactive glass particles could be useful clinically as an osteoconductive carrier material for treating bone infection.