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PubMed2004

Performance of a household-level arsenic removal system during 4-month deployments in Bangladesh.

A simple arsenic removal system was used in Bangladesh by six households for 4 months to treat well water containing 190-750 microg/L As as well as 0.4-20 mg/L Fe and 0.2-1.9 mg/L P. The system removes As from a 16-L batch of water in a bucket by filtration through a sand bed following the addition of about 1.5 g of ferric sulfate and 0.5 g of calcium hypochlorite. Arsenic concentrations in all but 1 of 72 samples of treated water were below the Bangladesh drinking water standard of 50 microg/L for As. Approximately half of the samples also met the World Health Organization (WHO) guideline of 10 microg/L. At the two wells that did not meet the WHO guideline, observations were confirmed by additional experiments in one case ([P] = 1.9 mg/L) but not in the other, suggesting that the latter household was probably not following the instructions. Observed residual As levels are consistent with predictions from a surface complexation model only if the site density is increased to 2 mol/mol of Fe. With the exception of Mn, the average concentrations of other inorganic constituents of health concern (Cr, Ni, Cu, Se, Mo, Cd, Sb, Ba, Hg, Pb, and U) in treated water were below their respective WHO guideline for drinking water.

Arsenic↗
PubMed1987

Ferric chloride-catalyzed activation of hydrogen peroxide for the demethylation of N,N-dimethylaniline, the epoxidation of olefins, and the oxidative cleavage of vicinal diols in acetonitrile: a reaction mimic for cytochrome P-450.

In dry acetonitrile, anhydrous Fe(III)Cl3 catalyzes the demethylation of N,N-dimethylaniline, the epoxidation of olefins, and the oxidative cleavage of 1-phenyl-1,2-ethanediol (and other 1,2-diols) by hydrogen peroxide. For each class of substrate the products closely parallel those that result from their enzymatic oxidation by cytochrome P-450. Because of the close congruence of products, the catalytic nature of the Fe(III)Cl3/H2O2 reaction mimic, and the similarity of the dipolar aprotic solvent (acetonitrile) to the proteinaceous lipid matrix of the biomembrane, the form of the reactive intermediate may be the same in each case. A mechanism is proposed in which an initial Lewis acid-base interaction of Fe(III)Cl3 with H2O2 generates a highly electrophilic Fe(III)-oxene species as the reactive intermediate. This is in contrast to the prevailing view that cytochrome P-450 acts as a redox catalyst to generate an Fe(V)-oxo species or an Fe(IV)-oxo cation radical as the reactive intermediate.

Acetonitriles↗
PubMed2006

Kinetics of mercury ions removal from synthetic aqueous solutions using by novel magnetic p(GMA-MMA-EGDMA) beads.

Poly(glycidylmethacrylate-methylmethacrylate), p(GMA-MMA-EGDMA), magnetic beads were prepared via suspension polymerization in the presence of ferric ions. The epoxy groups of the beads were converted into amino groups via ring opening reaction of the ammonia and, the aminated magnetic beads were used for the removal of Hg(II) ions from aqueous solution in a batch experiment and in a magnetically stabilized fluidized bed reactor (MFB). The magnetic p(GMA-MMA-EGDMA) beads were characterized with scanning electron microscope (SEM), FT-IR and ESR spectrophotometers. The optimum removal of Hg(II) ions was observed at pH 5.5. The maximum adsorption capacity of Hg(II) ions by using the magnetic beads was 124.8+/-2.1 mgg(-1) beads. In the continuous MFB reactor, Hg(II) ions adsorption capacity of the magnetic beads decreased with an increase in the flow-rate. The maximum adsorption capacity of the magnetic beads in the MFB reactor was 139.4+/-1.4 mgg(-1). The results indicate that the magnetic beads are promising for use in MFB for removal of Hg(II) ions from aqueous solution and/or waste water treatment.

Adsorption↗
PubMed2005

Antioxidant activities of extracts from Barkleyanthus salicifolius (Asteraceae) and Penstemon gentianoides (Scrophulariaceae).

Various extracts of the aerial parts of Barkleyanthus salicifolius (Asteraceae) and Penstemon gentianoides (Scrophulariaceae) have been used in folk medicine to treat many ailments, particularly inflammation and migraine. Neither the bioactive components responsible nor the mechanisms involved have been evaluated. Here are reported antioxidant activities of their methanol, dichloromethane, and ethyl acetate extracts. Samples were evaluated for oxygen radical absorption capacity (ORAC), ferric reducing antioxidant power (FRAP), 2,2-diphenyl-1-picryl-hydrazyl (DPPH) radical scavenging, and inhibition of the formation of thiobarbituric acid reactive species (TBARS), a measure of lipid peroxidation. Antioxidant activities were strongly correlated with total polyphenol content. The most active extracts from P. gentianoides in scavenging DPPH radicals and inhibiting TBARS formation were the methanol extract (A) and a further ethyl acetate extract of this (E). Partition E was further divided into eight fractions, and both E and the fractions were compared for activity against butylated hydroxytoluene, quercetin, and tocopherol. Partition E and the most active fractions, 5 and 6, were found to have I(50) values of 14.1, 38.6, and 41.8 ppm, respectively, against DPPH and 18.5, 26.0, and 12.7 ppm, respectively, against TBARS formation. Consistent with this finding, partition E and fractions 4-6 had the greatest ORAC and FRAP values. These results show that these plants could be useful antioxidant sources.

Antioxidants↗
PubMed2006

Evolution of iron speciation during hydration of C4AF.

It is now well accepted and demonstrated that calcium silicate, calcium aluminate and calcium sulfo aluminate (ettringite, AFm) phases exhibit a good capability to fix metals and metalloids. Unfortunately the role of minor phases and especially calcium-ferric aluminate phase, shorthand C4AF is not well defined. In other systems like in soils or sediments iron phases play a key role in the fixation of pollutant. In cement sorption isotherms, indicated that various metals can be retained by the C4AF hydrated products. Therefore the capabilities of those phase to retain heavy metal should not be neglected. Previous investigations have shown that the minerals formed during the hydration of C4AF are similar to those formed from C3A (pure tri-calcium aluminate) under comparable conditions. Nevertheless no investigation was conducted at the molecular level and there is still a controversy whether Fe substitutes for Al in the hydrated minerals in whole or in part, or if it forms FeOOH clusters scattered throughout the matrix. In this context we have conducted XAS experiments using synchrotron radiation. It was found that the hydration of C4AF forms C3AH6 (hydrogarnet) in which Fe randomly substitutes for Al as well as an amorphous FeOOH phase. Intermediate products like AFm (i.e., an ill organized lamellar phase) are also formed but rapidly evolve to C3AH6; iron does not seem to be incorporated in the AFm structure.

Aluminum Compounds↗
PubMed2002

Carbon tetrachloride transformation in a model iron-reducing culture: relative kinetics of biotic and abiotic reactions.

Contributions of biotic (cell-mediated) and abiotic (mineral-mediated) reactions to carbon tetrachloride (CT) transformation were studied in a model iron-reducing system that used hydrous ferric oxide (HFO) as the electron acceptor, acetate as the substrate, and Geobacter metallireducens as a representative dissimilative iron-reducing bacteria (DIRB). Over a period of 2-3 weeks, nanoscale magnetite particles, Fe3O4, were consistently formed as a product of iron respiration in this system. CT transformation rates were measured independently in resting cell suspensions of G. metallireducens or in suspensions of washed magnetite particles recovered from spent cultures. Protein and surface area-normalized expressions were derived for the biotic and abiotic reaction rates, respectively. Using the yield of total protein and magnetite surface area formed during growth in the model system as a basis for comparison, the mineral-mediated (abiotic) reaction was estimated to be 60-260-fold faster than the biotic reaction throughout the incubation period. We conclude that G. metallireducens induces CT transformation in this system primarily through the formation of reactive mineral surfaces rather than via co-metabolic mechanisms. The findings indicate that reactive biogenic minerals could play a significant role in the natural attenuation of chlorinated solvents in iron-reducing environments. A novel approach for stimulating reductive transformation of contaminants may be to enhance the formation of reactive biogenic minerals in situ.

Biotransformation↗
PubMed2002

Parenteral iron formulations: a comparative toxicologic analysis and mechanisms of cell injury.

BACKGROUND: Multiple parenteral iron (Fe) formulations exist for administration to patients with end-stage renal disease. Although there are concerns regarding their potential toxicities, no direct in vitro comparisons of these agents exist. Thus, the present study contrasted pro-oxidant and cytotoxic potentials of four available Fe preparations: Fe dextran (Fe dext), Fe sucrose (Fe sucr), Fe gluconate (Fe gluc), and Fe oligosaccharide (Fe OS). METHODS: Differing dosages (0.06 to 1 mg/mL) of each compound were added to either (1) isolated mouse proximal tubule segments, (2) renal cortical homogenates, or (3) cultured human proximal tubule (HK-2) cells (0.5- to 72-hour incubations). Oxidant injury (malondialdehyde generation) and lethal cell injury (percentage of lactate dehydrogenase release; tetrazolium dye uptake) were assessed. Effects of selected antioxidants (glutathione [GSH], catalase, dimethylthiourea (DMTU), and sodium benzoate also were assessed. RESULTS: Each test agent induced massive and similar degrees of lipid peroxidation. Nevertheless, marked differences in cell death resulted (Fe sucr >> Fe gluc > Fe dext approximately Fe OS). This relative toxicity profile also was observed in cultured aortic endothelial cells. Catalase, DMTU, and sodium benzoate conferred no protection. However, GSH and its constituent amino acid glycine blocked Fe sucr-mediated cell death. The latter was mediated by mitochondrial blockade, causing free radical generation and a severe adenosine triphosphate depletion state. CONCLUSIONS: (1) parenteral Fes are highly potent pro-oxidants and capable of inducing tubular and endothelial cell death, (2) markedly different toxicity profiles exist among these agents, and (3) GSH can exert protective effects. However, the latter stems from GSH's glycine content, rather than from a direct antioxidant effect.

Animals↗
PubMed2006

Iron sucrose induced morphological and functional changes in the rat kidney.

Treatment of anemia in uremic patients requires simultaneous supplementation of erythropoietin and iron. Because of the impaired iron absorption from the gastrointestinal tract in conditions of renal insufficiency, intravenous supplementation is a treatment of choice in such conditions. Iron compounds used for intravenous supplementation induce several systemic side effects, and therefore, we studied the effect of chronic exposure to iron sucrose in rats on renal function. Experiments were performed on male Wistar rats, which were infused intraperitoneally every 4 days, for 28 days with iron sucrose in a dose 1 mg/kg bw or 10 mg/kg bw diluted in 20 mL of the dialysis fluid. Control animals were infused with plain dialysis fluid. Renal function was evaluated at the beginning and at the end of the study. Additionally morphology of the kidneys was evaluated in all animals after 28 days of the study. Chronic exposure of rats to iron sucrose resulted in increased accumulation of PAS-positive material in their glomeruli: + 38% at Fe 1 mg/kg bw P < 0.05 and + 42% at Fe 10 mg/kg/bw P < 0.01 and collagen in the peritubular area: + 40% at Fe 1 mg/kg bw P < 0.005 and + 77% at Fe 10 mg/kg/bw P < 0.001. Only renal clearance of urea was decreased by 53%, P < 0.01 in rats exposed to iron sucrose at a dose of 10 mg/kg bw. Chronic exposure of rats to iron sucrose results in morphologic changes of the kidney; however, mild impairment in renal function was observed only at the highest (10 mg Fe/kg bw) concentration of iron sucrose.

Albuminuria↗
PubMed2001

Intravenous iron sucrose: establishing a safe dose.

It is now recognized that the majority of patients on epoetin therapy require intravenous (IV) iron supplementation to maximize the response to treatment. Of the IV iron preparations available, iron sucrose has proved its efficacy and safety; however, there are no guidelines or systematic studies examining the optimum safe dosage regimen for this compound. The aim of the present study was to investigate prospectively a variety of dosing regimens for IV iron sucrose in patients with renal failure to develop treatment strategies for this preparation. A total of 335 iron infusions was administered to 249 patients in this study, which was conducted in four phases. In phase I, 89 patients were administered a dose of 200 mg as an IV infusion over 2 hours. No adverse events were seen. A 500-mg dose by 2-hour infusion was then assessed, but was abandoned after 8 of 22 patients developed reactions characterized by dizziness, hypotension, and nausea. The dose was then reduced to 300 mg by 2-hour infusion for the next 189 patients, and again, no adverse reactions were witnessed. Finally, a 400-mg dose by 2-hour infusion was examined in 35 patients, but 2 patients experienced such symptoms as hypotension, nausea, and lower back pain. Both the 200- and 300-mg doses of IV iron sucrose administered over 2 hours appear to be safe. The incidence of adverse events with the 400- and 500-mg doses administered as a 2-hour infusion seems too high to recommend their routine use, although it may be possible to administer these doses over a longer period.

Abdominal Pain↗
PubMed1994

Effect of 21-aminosteroid U74500A (pregna-1,4,9(11)-triene-3,20-dione, 21-(4-(5,6-bis(diethylamino)-2-pyridinyl)-1-piperazinyl)-16-methyl-, HCl (16 alpha)) on rat brain cortex lipid peroxidation induced "in vivo" by iron-carbohydrate.

Compounds derived from glucocorticoids, 21-aminosteroids, were reported to inhibit in vitro lipid peroxidation in CNS tissue. In order to evaluate the possible scavenging and/or iron chelating activities in vivo of the 21-aminosteroid U74500A (pregna-1,4,9(11)-triene-3,20-dione, 21-(4-(5,6-bisdiethylamino)-2-pyridinyl)-1-piperazinyl)-16-methyl- , HCl (16 alpha)), the drug was administered for seven days to rats. These rats had been induced by iron-saccharate complex injection a slow process of lipid peroxidation into their right brain hemicortex. The drug was injected also to intact rats (normal rats). Seven days after the operation the extent of iron-induced lipid peroxidation in both the hemicortices and the effect of the drug, were assessed by the evaluation of lipid-soluble fluorescence and of conjugated diene formation. The assessment was performed both in vehicle (control) and in U74500A-treated rats. In the iron-injected rat groups the drug induced a significant dose-related reduction of fluorescence values. Formation of conjugated dienes showed a significant decrease when U74500A (48 mg/kg every 48 hr) was administered to cortico-cerebrally iron-injected animals. The lipid peroxidation of cortices in normal rats was evaluated as thiobarbituric acid reactant substances in both the drug-treated and the control animals. In normal rats, U74500A (48 mg/kg every 48 hr) caused a significant decrease of TBARS values, as compared to those observed in the control group. The iron content in the iron-injected hemicortices, which was evaluated by the ferrozine method, was not modified by drug treatment. U74500A appears to have in vivo antioxidant properties and not to affect the iron content in the neural tissue. An interaction of this drug with the metal, however, cannot be excluded.

Animals↗
PubMed2000

Antioxidant activity of Nigella sativa essential oil.

The essential oil of black cumin seeds, Nigella sativa L., was tested for a possible antioxidant activity. A rapid evaluation for antioxidants, using two TLC screening methods, showed that thymoquinone and the components carvacrol, t-anethole and 4-terpineol demonstrated respectable radical scavenging property. These four constituents and the essential oil possessed variable antioxidant activity when tested in the diphenylpicrylhydracyl assay for non-specific hydrogen atom or electron donating activity. They were also effective.OH radical scavenging agents in the assay for non-enzymatic lipid peroxidation in liposomes and the deoxyribose degradation assay. GC-MS analysis of the essential oil obtained from six different samples of Nigella sativa seeds and from a commercial fixed oil showed that the qualitative composition of the volatile compounds was almost identical. Differences were mainly restricted to the quantitative composition.

Animals↗
PubMed2002

Determination of the constants of affinity of FeCl3, CuCl2, and ZnCl2 for a nitrogen-containing organosilane bonded on Al2O3-cellulose acetate hybrid material surface from ethanol solution.

This work describes the preparation and characterization of a cellulose acetate fiber coated with Al(2)O(3), resulting in the organic-inorganic hybrid Cel/Al(2)O(3). Furthermore, the hybrid was modified by attaching organofunctional groups by reaction with the precursor reagents (RO)(3)Si(CH(2))(3)L (L=NH(2), NH(CH(2))(2)NH(2), NH(CH(2))(2)NH(CH(2))(2)NH(2), and N(2)C(3)H(3) (imidazole)), resulting in Cel/Al(2)O(3)/Si(CH(2))(3)NH(2) (1), Cel/Al(2)O(3)/Si(CH(2))(3)NH(CH(2))(2)NH(2) (2), Cel/Al(2)O(3)/Si(CH(2))(3)NH(CH(2))(2)NH(CH(2))(2)NH(2) (3), and Cel/Al(2)O(3)/Si(CH(2))(3)N(2)C(3)H(3) (4). The amounts of attached organofunctional groups were (in mmol per gram of the material) 1=1.90, 2=1.89, 3=1.66, and 4=1.35. The isotherms of adsorption of FeCl(3), CuCl(2), and ZnCl(2) by Cel/Al(2)O(3)/Si(CH(2))(3)L from ethanol solutions were obtained at 298 K. Accurate estimates of the specific sorption capacities and the heteregeneous stability constants of the immobilized metal complexes were determined with the aid of several computational procedures. It is shown that the sorptional capacities are much less than the concentrations of the attached organofunctional groups. As all sorption isotherms are fitted properly with the Langmuir isotherm equation, the effects of the energetic heterogeneity and the lateral interactions do not affect the chemisorption equilibria. The heterogeneous stability constants of the immobilized complexes are fairly high, which provides efficient removal of the metal ions from solutions by the hybrid materials.

Adsorption↗
PubMed1987

Effects of aluminum(III), chromium(III), and iron(III) on the rate of dissolution of calcium hydroxyapatite crystals in the absence and presence of the chelating agent desferrioxamine.

Aluminum ions (Al) and chromium (III) ions (Cr), as they exist in aqueous solution at neutral pH, adsorb onto calcium hydroxyapatite crystals (HAP) and severely inhibit their dissolution process, when present in concentrations less than 1 microM. Iron (III) ions (Fe), at concentrations up to 10 microM, have no effect on the dissolution process of HAP. The Fe-chelating agent desferrioxamine also forms strong complexes with Al but not with Cr. Desferrioxamine prevents the adsorption of Al to HAP and removes pre-adsorbed Al from the HAP surface, although not instantaneously, but has no significant effect on the adsorption of Cr to HAP. Desferrioxamine is also found to be capable of removing Al preadsorbed to bone powder.

Adsorption↗
PubMed1996

The promotion of iron-induced generation of reactive oxygen species in nerve tissue by aluminum.

Aluminum is suspected to play a role in several neurological disorders. Reactive oxygen species (ROS) lead to oxidative stress, which is thought to be a possible mechanism for neurological damage. Interactions between aluminum and iron, a known promoter of prooxidant events, were studied in cerebral tissues using a fluorescent probe to measure rates of generation of ROS. Al2(SO4)3 alone failed to stimulate ROS production over a wide range of concentrations (50-1000 microM). The aluminum-deferrioxamine chelate in the absence of iron could also not potentiate ROS formation. However, Al2(SO4)3 potentiated FeSO4-induced ROS, with a maximal effect at 10 microM Fe and 500 microM Al. Kaolin, a hydrated aluminum silicate, did not potentiate iron-induced ROS formation. Ferritin had a minor stimulatory effect on ROS generation, but this was not potentiated by the concurrent presence of Al2(SO4)3. Transferrin had no effect on basal rates of ROS generation, but when Al2(SO4)3 was also present, ROS production was enhanced. It is concluded that: 1. There is a potentiation of iron-induced ROS by aluminum salts; 2. Free or complexed aluminum alone is not a key producer of ROS; and 3. High rates of ROS production are unlikely to be owing to the displacement by aluminum iron from its biologically sequestered locations.

Alum Compounds↗
PubMed2004

Mechanochemical removal of organo-chlorinated compounds by inorganic components of soil.

The purpose of this work is to evaluate the catalytic efficiency of two metal oxides, ferrihydrite and birnessite and of a ferruginous smectite, towards organic molecules such as 4-chloroaniline (4-CA), pentachlorophenol (PCP), and five polychlorinated biphenyls (PCBs) characterised by different number and position of chlorine atoms. Mechanochemical dry contacts with light grinding between catalytic surfaces and pollutants have been carried out. The efficiency of the mechanochemical removal was compared with batch experiments for the soluble compounds (PCP and 4-CA). The removal of 4-CA and PCP by the mechanochemical procedure resulted more effective than by batch contact in the presence of birnessite and ferrihydrite, particularly at higher pH (100% removal of 4-CA by birnessite in 30 min at pH 8.6 after the mechanochemical contact compared to 20% removal using the batch interaction at the same pH). The mechanochemical contact of PCBs and birnessite produced a removal of pollutant that was a function of the number of chlorine atoms (complete removal of 2,2'-dichlorobiphenyl in 10 days and a removal of 30% and 20% of 2',3,4-trichlorobiphenyl and 3,3',4,4'-tetrachlorobiphenyl, respectively in 90 days) and of the position of chlorine atoms about the biphenyl rings (100% of 2,2'-dichlorobiphenyl in 10 days, 84% of 3,3'-dichlorobiphenyl in 15 days and 40% of 4,4'-dichlorobiphenyl in 27 days).

Aniline Compounds↗
PubMed2005

The impact of seasonal variations in DOC arising from a moorland peat catchment on coagulation with iron and aluminium salts.

Natural organic matter (NOM) is one of the main sources of environmental pollution to drinking water supplies in much of the UK and the US. Whilst traditional treatment with trivalent coagulants has proven a successful strategy in the past, operational problems are now being reported during periods of elevated organic levels in the water. Characterisation of the pollutants in terms of polarity, molecular weight and charge, provides a method to understand the impact of the observed temporal and spatial variations in terms of a mechanistic parameter relevant to the treatment processes. Results from this study demonstrate that it is not simply the increased organic concentration, but also the change in NOM composition and character, which influences the impact on the treatment processes. Consequently, monitoring of these parameters provides an insight into how to manage the impact caused by environmental changes to the catchments.

Aluminum↗
PubMed2005

The effect of citrate, oxalate, acetate, silicate and phosphate on stability of synthetic arsenic-loaded ferrihydrite and Al-ferrihydrite.

The effect of the organic species oxalate, citrate and acetate and the inorganic species silicate and phosphate on release of As(V) from synthetic arsenic-loaded ferrihydrite and Al-ferrihydrite in the pH range 4-8 was investigated. For ferrihydrite, the organic species increased %As(V) extraction in the order: acetate PO4(3-). Competitive adsorption of the investigated organic and inorganic species on ferrihydrite and Al-ferrihydrite could explain the enhanced release of As(V) into solution. However, disproportionate adsorption of other species relative to amount of As(V) release occurs, suggesting that mechanisms other than competitive adsorption are also operative. The results could best be explained in terms of combination of competitive adsorption and processes involving pH-dependent dissolution of ferrihydrite/Al-ferrihydrite, formation of various complex ionic species involving Al(III), Fe(III), As(V), SiO3(2-), PO4(3-), OH-, H+ and organic species: acetate, oxalate and citrate.

Acetates↗