ferric oxyhydroxides
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Iron-based nanomaterials have high technological impacts on various pro-environmental applications, including wastewater treatment using the co-precipitation method. The purpose of this research was to identify the changes of iron nanomaterial's structure caused by the presence of selenium, a typical water contaminant, which might affect the removal when the iron co-precipitation method is used. Therefore, we have investigated the maturation of co-precipitated nanosized ferric oxyhydroxides under alkaline conditions and their thermal transformation into hematite in the presence of selenite and selenate with high concentrations. Since the association of selenium with precipitates surfaces has been proven to be weak, the mineralogy of the system was affected insignificantly, and the goethite was identified as an only ferric phase in all treatments. However, the morphology and the crystallinity of ferric oxyhydroxides was slightly altered. Selenium affected the structural order of precipitates, especially at the initial phase of co-precipitation. Still, the crystal integrity and homogeneity increased with time almost constantly, regardless of the treatment. The thermal transformation into well crystalized hematite was more pronounced in the presence of selenite, while selenate-treated and selenium-free samples indicated the presence of highly disordered fraction. This highlights that the aftermath of selenium release does not result in destabilization of ferric phases; however, since weak interactions of selenium are dominant at alkaline conditions with goethite's surfaces, it still poses a high risk for the environment. The findings of this study should be applicable in waters affected by mining and metallurgical operations.
- MeSH
- alkálie chemie MeSH
- chemická precipitace MeSH
- krystalizace MeSH
- kyselina seleničitá chemie MeSH
- kyselina selenová chemie MeSH
- minerály chemie MeSH
- sloučeniny železa chemie MeSH
- spektroskopie infračervená s Fourierovou transformací MeSH
- spektroskopie Mossbauerova MeSH
- teplota MeSH
- železité sloučeniny chemie MeSH
- železo chemie MeSH
- Publikační typ
- časopisecké články MeSH
Rare diseases affect a small part of the population, and the most affected are children. Because of the low availability of patients for testing, the pharmaceutical industry cannot develop drugs for the diagnosis of many of these orphan diseases. In this sense, the use of benzothiazole compounds that are highly selective and can act as spectroscopy probes, especially the compound 2-(4'-aminophenyl)benzothiazole (ABT), has been highlighted. This article reports the design of potential contrast agents based on ABT and iron to develop a new material with an efficient mechanism to raise the relaxation rate, facilitating diagnosis. The ABT/δ-FeOOH hybrid material was prepared by grafting (N-(4'-aminophenyl) benzothiazole-2-bromoacetamide) on the surface of the iron oxyhydroxide particles. FTIR spectra confirmed the material formations of the hybrid material ABT/δ-FeOOH. SEM analysis checked the covering of nanoflakes' surfaces in relation to the morphology of the samples. The theoretical calculations test a better binding mode of compound with iron oxyhydroxide. Theoretical findings show the radical capture mechanism in the stabilization of this new material. In this context, Fe3+ ions are an electron acceptor from the organic phase.
- MeSH
- benzothiazoly chemie MeSH
- ionty chemie MeSH
- kontrastní látky chemie terapeutické užití MeSH
- lidé MeSH
- magnetické jevy MeSH
- spektrální analýza MeSH
- vzácné nemoci diagnóza diagnostické zobrazování patologie MeSH
- železité sloučeniny chemie MeSH
- železo chemie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
The impact of a natural wetland ("dambo" in Zambia) on neutral mine drainage at Luanshya in the Zambian Copperbelt has been investigated during an intermediate discharge period (July) using a multi-method characterization of solid phase samples, sequential extraction analysis, X-ray diffraction, Mössbauer spectroscopy, and scanning electron microscopy combined with water analyses, isotopic analyses, and geochemical modeling. In the wetland, the principal identified solid phases in sediments were carbonates, gypsum, and ferric oxyhydroxides. A significant portion of the ochres was present as insoluble hematite. Mine drainage pH values decrease, and log [Formula: see text] values increase after inflow of water into the wetland; dissolved and suspended concentrations of Fe, Mn, Cu, and Co also decrease. Based on speciation calculations, there is no precipitation of secondary Cu and Co minerals in the period of sampling, but it can occur later in dry period when the flow rate is reduced. Concentrations of sulfate decrease, and values of δ34S(SO4) in the wetland increase in parallel, suggesting sulfate reduction is occurring. In more advanced dry period, the discharge in mine drainage stream is probably much lower and water can reach supersaturation with respect to minerals such as gypsum, which has been found in sediments. Wetlands have a positive impact on mine drainage water quality due to the removal of metals by adsorption, co-precipitation, and filtration of colloids. However, there can also be a rebound of contamination by seepage inflow downstream from the wetland. Ongoing climate change with extreme hydrologic events may enhance differences between dry and rainy seasons with resulting faster mobilization of contaminants.
- MeSH
- adsorpce MeSH
- chemická precipitace MeSH
- chemické látky znečišťující vodu analýza MeSH
- difrakce rentgenového záření MeSH
- filtrace MeSH
- hornictví * MeSH
- klimatické změny * MeSH
- koloidy MeSH
- minerály chemie MeSH
- mokřady * MeSH
- monitorování životního prostředí * metody MeSH
- odpadní voda chemie MeSH
- počasí MeSH
- roční období MeSH
- síran vápenatý chemie MeSH
- sírany analýza MeSH
- těžké kovy analýza MeSH
- uhličitany chemie MeSH
- železité sloučeniny MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Zambie MeSH
Analysis of over 500 groundwater samples from throughout the Red River Delta indicates de-coupling of dissolved arsenic (As) and dissolved iron (Fe). Sorting of all data along the redox potentials suggests re-adsorption of As released initially from Mn(IV)-oxyhydroxides and later from Fe(III)-oxyhydroxides on remaining ferric phases at moderate redox levels. A gradually decreasing specific surface area available for re-adsorption of As probably plays a role as a consequence of limited reactivity of more crystalline phases such as goethite and hematite. At low redox levels, concentrations of Fe and phosphate decrease, but As concentrations keep increasing and most As is present as As(III) with limited adsorption affinity. Based on the results of speciation modeling, the water is supersaturated with respect to siderite and vivianite. A general conceptual model of As and Fe behavior is presented, suggesting that coupled behavior is possible in two geochemical "windows", i.e., 1: between saturation of remaining adsorption sites and the onset of siderite and vivianite precipitation, and 2: after the beginning of secondary sulfide phases precipitation and during methanogenesis. The de-coupling of As from Fe is common and has been observed at many sites around the world where As is released as a consequence of redox processes, e.g., in Bangladesh, West Bengal and Assam in India, the Mekong Delta in Cambodia and Vietnam, and Taiwan. The presented general conceptual model of de-coupling processes can be applied to the interpretation of As and Fe data, and, thus, it can help in the preparation of a site conceptual model which is a necessary prerequisite for reactive transport modeling.
- MeSH
- arsen analýza MeSH
- chemické látky znečišťující vodu MeSH
- epidemiologické monitorování MeSH
- geologické sedimenty analýza chemie MeSH
- monitorování životního prostředí metody MeSH
- oxidace-redukce MeSH
- řeky MeSH
- teoretické modely MeSH
- uhličitany MeSH
- železité sloučeniny analýza MeSH
- železo analýza MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Bangladéš MeSH
- Indie MeSH
- Kambodža MeSH
- Taiwan MeSH
- Vietnam MeSH
Despite the importance of phosphorus as a nutrient for humans and its role in ecological sustainability, its high abundance, resulting in large part from human activities, causes eutrophication that negatively affects the environment and public health. Here, we present the use of ferrate(VI) as an alternative agent for removing phosphorus from aqueous media. We address the mechanism of phosphate removal as a function of the Fe/P mass ratio and the pH value of the solution. The isoelectric point of γ-Fe2O3 nanoparticles, formed as dominant Fe(VI) decomposition products, was identified to play a crucial role in predicting their efficiency in removing of phosphates. Importantly, it was found that the removal efficiency dramatically changes if Fe(VI) is added before (ex-situ conditions) or after (in-situ conditions) the introduction of phosphates into water. Removal under in-situ conditions showed remarkable sorption capacity of 143.4 mg P per gram of ferric precipitates due to better accessibility of active surface sites on in-situ formed ferric oxides/oxyhydroxides. At pH = 6.0-7.0, complete removal of phosphates was observed at a relatively low Fe/P mass ratio (5:1). The results show that phosphates are removed from water solely by sorption on the surface of γ-Fe2O3/γ-FeOOH core/shell nanoparticles. The advantages of Fe(VI) utilization include its environmentally friendly nature, the possibility of easy separation of the final product from water by a magnetic field or by natural settling, and the capacity for successful phosphate elimination at pH values near the neutral range and at low Fe/P mass ratios.
Various low-molecular-weight organic acids (LMWOAs) play an important role in the mobilisation of contaminants and their subsequent uptake by plants. Nano-maghemite (NM) and an amorphous Mn oxide (AMO) were investigated for their stabilisation potential under simulated rhizosphere conditions in terms of their use during chemical stabilisation and aided phytostabilisation of metal(loid)s in contaminated soils. In order to understand the reactivity of these potential sorbents of contaminants in soils and subsequent mobility of metal(loid)s, a set of time-dependent batch leaching experiments was performed using a mix of acetic, lactic, citric, malic and formic acids simulating root exudates. Despite being relatively unstable under given conditions, the AMO proved to be an efficient amendment for rapid stabilisation of both metals and As compared to NM. Generally, low pH (∼ 4) and the presence of citrate complexes resulted in higher mobility of metals in the non- and NM-amended soil. In contrast, the presence of AMO in the soil accelerated the neutralisation reactions related to pH increase and (co-) precipitation of secondary Fe/Mn/Al oxyhydroxides. Mineralogical transformations of the AMO showed to be crucial for contaminant immobilisation.
- MeSH
- arsen chemie MeSH
- kovové nanočástice chemie MeSH
- kovy chemie MeSH
- kyseliny karboxylové chemie MeSH
- látky znečišťující půdu chemie MeSH
- molekulová hmotnost MeSH
- oxidy chemie MeSH
- sloučeniny manganu chemie MeSH
- železité sloučeniny chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Owing to Mössbauer spectroscopy, an advanced characterization technique for iron-containing materials, the present study reveals previously unknown possibilities using l-amino acids for the generation of magnetic particles. Based on our results, a simple choice of the order of l-amino acids addition into a reaction mixture containing ferrous ions leads to either superparamagnetic ferric oxide/oxyhydroxide particles, or magnetically strong Fe0-Fe2O3/FeOOH core-shell particles after chemical reduction. Conversely, when ferric salts are employed with the addition of selected l-amino acids, only Fe0-Fe2O3/FeOOH core-shell particles are observed, regardless of the addition order. We explain this phenomenon by a specific transient/intermediate complex formation between Fe2+ and l-glutamic acid. This type of complexation prevents ferrous ions from spontaneous oxidation in solutions with full air access. Moreover, due to surface-enhanced Raman scattering spectroscopy we show that the functional groups of l-amino acids are not destroyed during the borohydride-induced reduction. These functionalities can be further exploited for (i) attachment of l-amino acids to the as-prepared magnetic particles, and (ii) for targeted bio- and/or environmental applications where the surface chemistry needs to be tailored and directed toward biocompatible species.
