Addition Of Ferrous Iron Research Articles

Biological Solubilisation of Metals from Solid Waste Materials from Copper, Steel and Recycling Industries

The aim of the present work was to study the feasibility of using bioleaching for the solubilisation of metals from solid waste streams and by-products of copper, steel and recycling industries. Optimal process conditions were tested using iron and sulphur oxidising acidophiles in shake flasks at 25°C. The effects of inoculum, ferrous iron, sulphur, chloride ion, pH, and the type of waste material on metal solubilisation were evaluated. Solubilisation of metals was mainly achieved through acid attack due to the formation of sulphuric acid by sulphur oxidising bacteria. Addition of ferrous iron and chloride ion did not enhance solubilisation.

鉄酸化細菌を用いた廃棄プリント配線板のバイオリーチング

In order to recover copper from waste printed wiring boards which were free of mounted parts, bioleaching experiments of the boards were carried out using Acidithiobacillus ferrooxidans in shaking flasks. The size fraction and the copper content of the sample mainly used were -3.5+8mesh and 34.1% respectively. In the preliminary study using metal copper powder, the dissolution of copper was accelerated with the addition of ferric iron in the bioleaching while not in the absence of ferric iron. Ferric iron oxidized metal copper to give copper ions, and Acidithiobacillus ferrooxidans oxidized ferrous iron, promoting dissolution of metal copper. The dissolution rate of copper increased with increase in the initial concentration of ferric iron in the bioleaching of the waste printed wiring board. After the bioleaching of 125 hours, 72% of copper was dissolved with initial ferric ion concentration of 600mg/L, which was approximately three times as much as that without ferric iron.

Advanced treatment of landfill leachate from a sequencing batch reactor (SBR) by electrochemical oxidation process

Biologically stabilized landfill leachate usually requires further removal of organic substances and ammonia nitrogen (NH3-N) before final discharge. In this paper, the advanced treatment of landfill leachate pretreated by sequencing batch reactor (SBR) via electrochemical oxidation was carried out in an electrochemical compartment reactor with oxide-coated titanium anode (Ti/TiO2-IrO2). The effect of voltage, chlorine content, initial pH value, and ferrous sulfate (FeSO4) on the removal efficiency of contaminants was investigated systematically. The removal efficiency of organic pollutants and ammonia nitrogen (NH3-N) increased with the increase of voltage, chlorine content and the addition of ferrous iron. The initial pH value has a different effect on the removal of COD and NH3-N. Compared with the traditional electrochemical oxidation, the process with Fe(II/III) is more efficient with low power consumption, and the removal efficiency of organic pollutant is slightly lower when Fe(II) is used. A lower power consumption of 16.6 kWh·(kg COD)–1 indicated the electrochemical oxidation with Fe(II) was a promising alternative for the advanced treatment of leachate.

Ferrous iron in post-perovskite from first-principles calculations

We investigate by first-principles calculations the effect of ferrous iron, Fe 2+, on the structure and the equation of state of MgSiO 3 post-perovskite. We find that ferrous iron is high-spin over the pressure range of the mantle assuming a ferromagnetic structure. The bulk modulus and the specific volume increase with the addition of ferrous iron to MgSiO 3. We find that Fe partitions preferentially to post-perovskite and broadens the two-phase pressure range.

Influence of ferrous iron on the granularity of a UASB reactor

The effect of ferrous ion addition on the granularity of an upflow anaerobic sludge blanket (UASB) reactor was investigated. Two UASB reactors (R1 and R2) (35 °C; pH 7) were operated for 3 months at a 20-h hydraulic retention time (HRT) at organic loads from 1.4 to 10.0 g COD L−1 d−1. Ferrous iron was fed only to reactor R1 in a range of load from 0.014 to 0.100 g Fe2+ L−1 d−1. The addition of ferrous iron induced a stable and excellent COD conversion rate. The enhancement of the performance of reactor R1 may be accredited to the mean granule diameter increase as well as to the sludge bed porosity decrease. The addition of iron to reactor R1 had a pronounced effect on the quality of the granular sludge, increasing the characteristic settling velocities. The formation of ferrous sulphide was mainly responsible for the promotion of sludge granulation.

Effect of modified Fenton treatment on the thermal behavior of contaminated harbor sediments

This study presents the results of experimental Fenton-like treatments conducted on marine sediment slurries (2 g sediment vs. 20 ml liquid). The sediment was collected in a harbor situated in a high density industrial area, characterized by a great hydrocarbon C > 12 and PAHs contamination. The investigated parameters were: the H 2O 2 dose, the reagent’s pH and the effect of a phosphate salt and ferrous iron addition. To evaluate sediment’s characteristics COD, particle size, thermogravimetric and differential thermal analyses were performed under N 2 and O 2 atmosphere while dissolved organic carbon and COD analyses were performed on the filtrate. Results indicate that the treatment was able to change the organic matter to a less hydrophobic state, to destroy part of the organic carbon (up to 78% decrease of the 200–400 °C labile organic matter), to lower the COD of the sediment (60% COD removal maximum) and to increase the cumulated distribution undersize. In addition as the treated sediment showed easier-to-handle characteristics, reduced caking and lower aggregation capacity, the modified Fenton treatment could also be considered a pre-treatment of a successive thermal treatment.

Myoglobin Oxidation in a Model System as Affected by Nonheme Iron and Iron Chelating Agents

A model system was used to study the effect of nonheme iron on myoglobin oxidation at pH 5.6 and pH 7.2 at 23 degrees C. The addition of ferrous iron significantly (p < 0.05) increased the rate of myoglobin oxidation in the absence of lipid, demonstrating that iron promoted myoglobin oxidation independent of the effect of lipid oxidation. The addition of the type II, iron chelating antioxidants sodium tripolyphosphate (at pH 7.2) or milk mineral (at pH 5.6) negated the effect of added iron, slowing oxidation of myoglobin. A clear concentration dependence was seen for iron-stimulated myoglobin oxidation, based on both spectral and visual evidence. Further investigation is needed to determine the possible role for nonheme ferrous iron on myoglobin oxidation in vivo or in meat.

Iron speciation and dynamics during SERIES, a mesoscale iron enrichment experiment in the NE Pacific

Abstract During the Sub-arctic Ecosystem Response to Iron Enrichment Study (SERIES), the addition of ferrous iron to high-nitrate low-chlorophyll (HNLC) waters near Ocean Station PAPA (OSP: 50°N, 145°W) produced a phytoplankton bloom and CO 2 drawdown, as evidenced by decreasing CO 2 fugacity ( f CO 2 ). We analyzed five fractions or phases of iron: soluble ( 0.22 μm). Here, we describe iron distributions and the evolution of iron phases in the upper ocean during the experiment. We also present an iron budget accounting for horizontal and vertical dilution. At the time of our first sampling eight hours after fertilization was completed, total iron reached 8.6 nmol L −1 and dissolved iron was approximately 3 nmol L −1 . Early in the experiment the dissolved iron phase decreased the most rapidly and by late day 6 the integrated dissolved iron (8.6 μmol m −2 ) represented less than 10% of the initial addition (90–95 μmol m −2 ). However at this same time the total integrated iron at the centre of the patch was still 52 μmol m −2 or almost 60% of the calculated initial addition. By day 12,45% of the added iron (from both injections) could be accounted for in the patch. The half-life of total iron in the patch for the first injection was estimated to be less than 5 days if dilution is not considered, but more than 13 days if dilution is taken into account. The most notable change in iron percentages from one form to another occurred early in the first week of the experiment where the predominant phase shift was from the colloidal portion of dissolved iron to labile particulate iron that could have been biologically induced or simply aggregation of oxyhydroxides. This was immediately followed by a physical event resulting in a reduction in the non-labile particulate iron due to sinking out of the patch. The second infusion did not change the relative concentration of the various pools of iron as might be expected, but this was likely due to the fact that it was a much smaller injection than the first. The most pronounced change after the second infusion was the reduction in the labile particulate pool which coincided with one of the largest decreases in silicate observed during the entire experiment. In general the gradual decrease in the fraction of the 10 m colloidal iron as well as episodic losses of, or shifts in, integrated colloidal iron are thought to be the result of adsorption of colloidal iron to the plankton cell surfaces as well as aggregation of oxyhydroxides but could also be the result of utilization of colloidal iron by mixotrophic phytoplankton.

Effect of ferrous ion on the biological activity in a UASB reactor: Mathematical modeling and verification

The effect of ferrous ion on the biological activity in a upflow anaerobic sludge blanket (UASB) reactor was studied. A mathematical model was developed and validated in order to simulate the dynamic behavior of a UASB reactor. This model took into consideration of all the biological and physicochemical reactions. The model was able to simulate the accumulation of iron in the sludge bed and its effect on the biological activity of the anaerobic sludge. A significant increase in the maximum uptake rate of methanogens and acidogens was revealed when iron was supplemented to the UASB reactor. The addition of ferrous iron induced a stable and excellent COD conversion rate. The model can be a useful tool for the prediction of process performance in the future and can be used to assist in the operation of biogas plants. The ferrous ion addition proved to enhance the biological activity of UASB sludge. Thus, the model can be used for the design of treatment plants that will take advantage of the benefits of iron addition.

Chalcopyrite concentrate leaching with biologically produced ferric sulphate

Biological ferric iron production was combined with ferric sulphate leaching of chalcopyrite concentrate and the effects of pH, Fe 3+, temperature and solids concentration on the leaching were studied. The copper leaching rates were similar at pH of 1.0–1.8 and in the presence of 7–90 g L −1 Fe 3+ despite massive iron precipitation with 90 g L −1 Fe 3+. Increase of the leaching temperature from 50 °C to 86 °C and solids concentration from 1% to 10% increased the copper leaching rate. Increase in solids concentration from 1% to 10% decreased the copper yields from 80% to 40%. Stepwise addition of ferric iron did not improve the copper yields. CuFeS 2, Ag and Cu 1.96S potentials indicated the formation of a passivating layer, which consisted of jarosite and sulphur precipitates and which was responsible for the decreased leaching rates.

Thioredoxin Reductase System Mediates Iron Binding in IscA and Iron Delivery for the Iron-Sulfur Cluster Assembly in IscU*

IscA is a key member of the iron-sulfur cluster assembly machinery found in bacteria and eukaryotes. Previously, IscA was characterized as an alternative iron-sulfur cluster assembly scaffold, as purified IscA can host transient iron-sulfur clusters. However, recent studies indicated that IscA is an iron-binding protein that can provide iron for the iron-sulfur cluster assembly in a proposed scaffold IscU (Ding H., Clark, R. J., and Ding, B. (2004) J. Biol. Chem. 279, 37499-37504). To further elucidate the roles of IscA in the biogenesis of iron-sulfur clusters, we reevaluate the iron binding activity of IscA under physiologically relevant conditions. The results indicate that in the presence of the thioredoxin reductase system, Escherichia coli IscA binds iron with an iron association constant of 2.0 x 10(19) M(-1) in vitro. Whereas all three components (thioredoxin 1, thioredoxin reductase and NADPH) in the thioredoxin reductase system are essential for mediating the iron binding in IscA, only catalytic amounts of thioredoxin 1 and thioredoxin reductase are required. In contrast, IscU fails to bind iron in the presence of the thioredoxin reductase system, suggesting that the iron binding in IscA is specific. Nevertheless, the thioredoxin reductase system can promote the iron-sulfur cluster assembly in IscU in the presence of the iron-loaded IscA, cysteine desulfurase (IscS), and L-cysteine, demonstrating a physiologically relevant system for the biogenesis of iron-sulfur clusters. The results provide additional evidence for the hypothesis that IscA is capable of recruiting intracellular "free" iron and delivering the iron for the iron-sulfur cluster assembly in IscU.

Decrease in Net Mercury Methylation Rates Following Iron Amendment to Anoxic Wetland Sediment Slurries

The rate of mercury methylation in anoxic wetland sediments is affected by the concentration of bioavailable complexes between Hg and sulfide. Previous research with pure bacterial cultures has shown that addition of ferrous iron reduces the net rate of mercury methylation by decreasing the concentration of dissolved sulfide. To assess the possibility of using this approach to decrease net mercury methylation in restored and constructed wetlands, laboratory experiments were conducted by adding Hg(II) and Fe(II) to sediments collected from six sites in five estuarine wetlands. Addition of 30 mM (0.07 mmol g(-1) or 3.9 mg g(-1)) Fe(II) decreased net mercury methylation relative to that of unamended controls by a factor of 2.1-6.6. In all cases, the observed decrease in net mercury methylation was accompanied by a decrease in the concentrations of sulfide and filterable mercury in the water overlying the sediments. When iron was added to one of the sediment samples at doses that were small relative to the concentration of sulfide present, net mercury methylation either increased slightly or was unaffected. Comparison of the results to speciation model predictions suggests that dissolved reduced sulfur-containing species play a role in the formation of uncharged, bioavailable Hg complexes. Although further research is needed to determine the long-term effect of iron amendment, these results suggest that iron addition decreases mercury methylation in authentic wetland sediments.

P‐quinone mediates 6‐hydroxydopamine‐induced dopaminergic neuronal death and ferrous iron accelerates the conversion of p‐quinone into melanin extracellularly

Parkinson's disease (PD) is characterized by the selective loss of dopaminergic neurons in the substantia nigra (SN). 6-Hydroxydopamine (6-OHDA), a dopaminergic neurotoxin, is detected in human brains and the urine of PD patients. Using SH-SY5Y, a human neuroblastoma cell line, we demonstrated that 6-OHDA toxicity was determined by the amount of p-quinone produced in 6-OHDA auto-oxidation rather than by reactive oxygen species (ROS). Glutathione (GSH), which conjugated with p-quinone, provided significant protection whereas catalase, which detoxified hydrogen peroxide and superoxide anions, failed to block cell death caused by 6-OHDA. Although iron accumulated in the SN of patients with PD can cause dopaminergic neuronal degeneration by enhancing oxidative stress, we found that extracellular ferrous iron promoted the formation of melanin and reduced the amount of p-quinone. The addition of ferrous iron to the culture medium inhibited caspase-3 activation and apoptotic nuclear morphologic changes and blocked 6-OHDA-induced cytotoxicity in SH-SY5Y cells and primary cultured mesencephalic dopaminergic neurons. These data suggested that generation of p-quinone played a pivotal role in 6-OHDA-induced toxicity and extracellular iron in contrast to intracellular iron was protective rather than harmful because it accelerated the conversion of p-quinone into melanin.

Removal and recovery of copper from wastewater by a complexation-ultrafiltration process

Carboxyl methyl cellulose (CMC) as a water-soluble metal-binding polymer in combination with ultrafiltration (UF) was used in a hybrid approach for selective removal and recovery of copper from water. In the complexation-UF process the cationic forms of heavy metals were first complexed by a macro ligand in order to increase their molecular weight to having a size larger than the pores of the selected membrane that can be retained and flow out in the retentate whereas permeate water was purified to a certain extent from heavy metals. The complexation of Cu2+, Pb2+, Fe2+ and Mn2+ by CMC from synthetic solutions and real wastewater followed by UF filtration used as a complex separation step was studied. The aim was to recover water-soluble polymers and to obtain a heavy metal concentrate; attempts were also made to destroy the Me:CMC complexes by a pH decrease. The decomplexation procedure was followed by a second step of UF. The results obtained show that a low mole Cu:CMC ratio favors both ultrafiltrate permeability during the first stage of the process and the separation following the next step of complex destruction at a lower pH. The comparative experiments with (1)synthetic water containing copper as a single heavy metal; (2)copper containing a solution with addition of ferrous iron, manganese and lead; and (3) drainage mine water contaminated with copper, ferrous iron, manganese and lead show a selectivity for Cu during the first stage of UF approaching 99% in these three cases. However, the destruction of complexes of heavy metals from the real wastewater was limited — up to 80%.

Iron-dependent activation of NF-κB in Kupffer cells: a priming mechanism for alcoholic liver disease

Alcoholic liver disease is associated with hepatic iron accumulation, and iron supplementation exacerbates alcoholic liver disease, suggesting the pathogenic role of iron in alcoholic liver disease. We have tested a hypothesis that iron plays a signaling role in activation of redox-sensitive nuclear factor-kappa B (NF-κB) and that increased iron content results in heightened expression of proinflammatory cytokines in Kupffer cells because of this signaling. In cultured Kupffer cells isolated from normal rats, treatment with a lipophilic iron chelator, 1,2-dimethyl-3-hydroxypyrid-4-one (L1), markedly reduced lipopolysaccharide (LPS)-induced NF-κB activation and expression of tumor necrosis factor-alpha (TNF-α) and interleukin-6. Kupffer cells, isolated from rats with experimentally induced alcoholic liver disease, had significant increases in nonheme iron content, NF-κB binding, and mRNA expression for TNF-α and macrophage inflammatory protein-1. Ex vivo L1 treatment normalized all these parameters. Addition of ferrous iron to cultured normal rat Kupffer cells increased I-kappa B kinase (IKK) activity at 15 min and NF-κB binding at 30 min. L1 pretreatment completely abrogated both effects. Moreover, the iron treatment increased TNF-α release and TNF-α promoter activity in a NF-κB-dependent manner. Ferrous iron also transiently decreased cytoplasmic I-kappa B-alpha (IκB-α), with concomitant increases in nuclear p65 protein and DNA binding of p65/p50. Taken together, these results support the existence of iron-dependent signaling for activation of IKK/NF-κB in Kupffer cells, and this iron signaling serves as a target for a potential priming effect for the pathogenesis of experimental alcoholic liver disease.

Signaling Role of Intracellular Iron in NF-κB Activation

Iron chelators inhibit endotoxin-induced NF-kappaB activation in hepatic macrophages (HMs), suggesting a role for the intracellular chelatable pool of iron in NF-kappaB activation. The present study tested this hypothesis. Analysis of Fe(59)-loaded HMs stimulated with lipopolysaccharide (LPS), revealed a previously unreported, transient rise in intracellular low molecular weight (LMW).Fe(59) complex ([LMW.Fe](i)) at </=2 min returning to the basal level within 15 min. The [LMW.Fe](i) response preceded IkappaB kinase (IKK) (>/=15 min) and NF-kappaB (>/=30 min) activation. Iron chelators (1,2-dimethyl-3-hydroxypyridin-4-one and N,N'-bis-2-hydroxybenzylethylenediamine-N,N'-diacetic acid) abrogated the [LMW.Fe](i) response and IKK and NF-kappaB activation. The [LMW.Fe](i) response was also observed in tumor necrosis factor alpha (TNFalpha)-stimulated HMs and RAW264.7 cells treated with LPS and interferon-gamma but not in primary rat hepatocytes or myofibroblastic cells exposed to LPS or TNFalpha. Both [LMW.Fe](i) response and IKK activation in LPS-stimulated HMs were inhibited by diphenylene iodonium (nonspecific inhibitor for flavin-containing oxidases), l-N(6)-(1-iminoethyl)lysine (selective iNOS inhibitor), and adenoviral-mediated expression of a dominant negative mutant of Rac1 or Cu,Zn-superoxide dismutase, suggesting the role of (.)NO and O(2)() in mediating the iron signaling. In fact, this inhibition was recapitulated by a cell-permeable scavenger of ONOO(-), 5,10,15,20-tetrakis (4-sulfonatophenyl)porphyrinato iron (III) chloride. Conversely, ONOO(-) alone induced both [LMW.Fe](i) response and IKK activation. Finally, direct addition of ferrous iron to cultured HMs activated IKK and NF-kappaB. These results support a novel signaling role for [LMW.Fe](i) in IKK activation, which appears to be induced by ONOO(-) and selectively operative in macrophages.

Enhanced sonochemical decomposition of 1,4-dioxane by ferrous iron

The enhanced ultrasonic decomposition of 1,4-dioxane by the addition of ferrous iron (Fe(II)) was investigated at 205, 358, 618, and 1071 kHz. The total organic carbon (TOC) remaining was also determined at each frequency. Addition of Fe(II) improved the 1,4-dioxane decomposition rate and mineralization efficiency at all frequencies studied. A nearly four-fold increase of the rate constant was observed at the optimal Fe(II) concentration and a frequency of 205 kHz. In the presence and absence of the iron, the fastest overall degradation and mineralization of 1,4-dioxane took place at 358 kHz where 95% of the initial 1,4-dioxane was removed after 50 min. Finally, although reduced, the ultrasonic decomposition of 1,4-dioxane was still significant at all frequencies in the presence of the hydroxyl radical scavenger bicarbonate.

Microbial sulfate reduction at low pH in sediments of an acidic lake in Argentina.

We measured sulfate reduction in the acidic (pH < or = 3) sediment of an Argentinean lake influenced by volcanism. Sulfate reduction rates of 2.04 mmol m(-2) d(-1) were determined with a 35SO4(2-) core injection method and confirmed by batch incubations and from H2S measurements in the sediment. H2S production stopped when iron reduction was stimulated by addition of ferric iron. The results suggest that sulfate reduction at pH values around 3 is possible and can probably be used in biotechnological strategies if competing microbial processes are inhibited and electron donors are highly available.

Mechanisms for naphthalene removal during electrolytic aeration

Batch tests were performed to investigate chemical and physical processes that may result during electrolytic aeration of a contaminated aquifer using naphthalene as a model contaminant. Naphthalene degradation of 58–66% took place electrolytically and occurred at the same rates at a pH of 4 and 7. 1,4-naphthoquinone was identified as a product of the electrolysis. Stripping due to gases produced at the electrodes did not result in any naphthalene loss. Hydrogen peroxide (which may be produced at the cathode) did not have any effect on naphthalene, but the addition of ferrous iron (which may be present in aquifers) resulted in 67–99% disappearance of naphthalene. Chlorine (which may be produced from the anodic oxidation of chloride) can effectively degrade naphthalene at pH of 4, but not at a pH of 7. Mono-, di- and poly chloronaphthalenes were identified as oxidation products. Ferric iron coagulation (due to the oxidation of ferrous iron) did not significantly contribute to naphthalene loss. Overall, electrolytic oxidation and chemical oxidation due to the electrolytic by-products formed are significant abiotic processes that could occur and should be accounted for if bioremediation of PAH-contaminated sites via electrolytic aeration is considered. Possible undesirable products such as chlorinated compounds may be formed when significant amounts of chlorides are present.

Generation of carbon monoxide and iron from hemeproteins in the presence of 7,8-dihydroneopterin

7,8-Dihydroneopterin and neopterin are secreted by human and primate macrophages after activation by interferon-γ in a ratio of 2:1. 7,8-Dihydroneopterin is known to suppress radical-mediated processes, but it is also able in the presence of iron ions to generate superoxide radical anion and hydroxyl radicals from molecular oxygen. Effects of 7,8-dihydroneopterin were investigated on (met)myoglobin and (met)hemoglobin. Addition of 7,8-dihydroneopterin to heme proteins in air-saturated solution resulted in dose-dependent cleavage of the porphyrin moiety. The liberation of non-heme iron and carbon monoxide originating from the cleaved porphyrin was quantified. Both were generated at equimolar concentrations with a linear correlation coefficient of 0.9. Addition of ferrous iron significantly accelerated the pteridine-mediated cleaving of the porphyrin. However, the total yield of porphyrin cleaved was controlled by the pterin rather than by the ferrous ion concentration. 7,8-Dihydroneopterin is assumed to reduce the heme iron in intact protein molecules, thereby preparing the conditions for binding of oxygen and carbon monoxide as ligands. Beyond that, it is concluded that hydroxyl radicals might be generated via reduction of molecular oxygen to superoxide anion in the autoxidation process and dismutation to hydrogen peroxide and subsequent Fenton reaction.