High Concentrations Of Ferric Ions Research Articles

The Development of Innovated Complex Process for Treatment of Old Flotation Tailings of Copper-Zinc Sulfide Ore.

The possibility of selective Cu and Zn leaching from the sample of old pyrite tailings, which is one of the most widespread types of solid waste forming during non-ferrous metal production, using sulfuric acid solutions and water was studied. It was shown that water leaching provided selective extraction of Cu and Zn and comparatively low iron ion extraction. At the same time, acid leaching provided the obtainment of pregnant solutions with high ferric ion concentration, which can be used for oxidative leaching of substandard copper concentrates. Water and acid leaching also provided increased Au recovery by cyanidation. The results suggest that acid leaching can be an effective approach for processing old flotation tailings, which allows the extraction of base metals from these wastes and treating flotation tailings for subsequent cyanidation. Effective flotation treatment methods should also provide environmental load reduction, which is caused by the long-term storage of metal-bearing wastes.

Killing Effect of Bacillus Velezensis FZB42 on a Xanthomonas Campestris pv. Campestris (Xcc) Strain Newly Isolated from Cabbage Brassica Oleracea Convar. Capitata (L.): A Metabolomic Study.

The potential use of Bacillus velezensis FZB42 for biological control of various phytopathogens has been documented over the past few years, but its antagonistic interactions with xanthomonads has not been studied in detail. Novel aspects in this study consist of close observation of the death of Xanthomonas campestris pv. campestris cells in a co-culture with B. velezensis FZB42, and quantification of lipopeptides and a siderophore, bacillibactin, involved in the killing process. A new robust Xcc-SU isolate tolerating high concentrations of ferric ions was used. In a co-culture with the antagonist, the population of Xcc-SU was entirely destroyed within 24–48 h, depending on the number of antagonist cells used for inoculation. No inhibitory effect of Xcc-SU on B. velezensis was observed. Bacillibactin and lipopeptides (surfactin, fengycin, and bacillomycin) were present in the co-culture and the monoculture of B. velezensis. Except for bacillibactin, the maximum contents of lipopeptides were higher in the antagonist monoculture compared with the co-culture. Scanning electron microscopy showed that the death of Xcc-SU bacteria in co-culture was caused by cell lysis, leading to an enhanced occurrence of distorted cells and cell ghosts. Analysis by mass spectrometry showed four significant compounds, bacillibactin, surfactin, fengycin, and bacillomycin D amongst a total of 24 different forms detected in the co-culture supernatant: Different forms of surfactin and fengycin with variations in their side-chain length were also detected. These results demonstrate the ability of B. velezensis FZB42 to act as a potent antagonistic strain against Xcc.

Effect of Iron Redox Equilibrium on the Foaming Behavior of MgO-Saturated Slags

In this study, the foaming index of CaO-SiO2-FetO and CaO-SiO2-FetO-Al2O3 slags saturated with MgO was measured to understand the relationship between their foaming behavior and physical properties. The foaming index of MgO-saturated slags increases with the FetO content due to the redox equilibrium of FetO. Experimental results indicated that MgO-saturated slag has relatively high ferric ion concentration, and the foaming index increases due to the effect of ferric ion. Therefore, the foaming behavior of MgO-saturated slag is more reasonably explained by considering the effect of ferric ion on the estimation of slag properties such as viscosity, surface tension, and density. Specifically, the estimation of slag viscosity was additionally verified by NBO/T, and this is experimentally obtained through Raman spectroscopy.

Improved production of poly-γ-glutamic acid with low molecular weight under high ferric ion concentration stress in Bacillus licheniformis ATCC 9945a

This study found that high ferric ion (Fe3+) concentrations lead to high poly-γ-glutamic acid (γ-PGA) production and low-molecular-weight γ-PGA. In cultures containing 7.4 mmol/L FeCl3, the average molecular weight of γ-PGA reached 3.18 ± 0.3 × 105 Da, which is a 76% decrease from that in the culture without FeCl3 (1.31 ± 0.14 × 106 Da). Cultures containing increasing concentrations of FeCl3 (0–7.4 mmol/L) showed a corresponding increase in γ-PGA yield from 26.57 ± 1.64 to 34.93 ± 1.05 g/L. Transcription level analysis indicated that high FeCl3 concentrations could enhance the expression of γ-PGA synthetase genes (pgsA, pgsB, and pgsC), which may contribute to the improved production of γ-PGA. In addition, γ-PGA degradation genes ggt (encoding γ-glutamyltransferase) and cwlO were found to contribute to a lower γ-PGA molecular weight in cultures containing 7.4 mmol/L FeCl3. The result of γ-glutamyltransferase activity was in agreement with the results of the transcription level analysis. Overall, this study would provide a novel method for the regulation of synthesis of γ-PGA with low molecular weight.

Estimation of Cells Growth and Substrate Oxidation in Initial Stages of Adaptation of Acidithiobacillus ferrooxidans to High Concentrations of Ferric Ions

Acidithiobacillus ferrooxidans is among the few microorganisms which take energy from the oxidation of the ferrous ions in acidic medium. That hemolitoautotrophic bacterium is well known and successfully used in the wastewater treatment of and in all aspects of microbial mediated extraction of metals from minerals or solid wastes and acid mine drainages. The use of bacteria in environmentally friendly technologies may fall in areas with high concentrations of iron and lead, and this is toxic for the strain. In order to avoid inhibition of the bacterial action, it is necessary to adapt Acidithiobacillus ferrooxidans to high initial concentrations of iron ions. The aim of present work is to estimate the processes of substrate oxidation and cells growth in exponential phase of batch cultivation of the strain, loaded higher initial concentration of ferric ions. It was established that there is no in uence of initial substrate concentrations on the strain in the beginning stages of its adaptation to high concentrations of ferrous ions.

Metschnikowia strains isolated from botrytized grapes antagonize fungal and bacterial growth by iron depletion.

Noble-rotted grapes are colonized by complex microbial populations. I isolated pigment-producing Metschnikowia strains from noble-rotted grapes that had antagonistic activity against filamentous fungi, yeasts, and bacteria. A red-maroon pigment was formed from a diffusible colorless precursor released by the cells into the medium. The conversion of the precursor required iron and could occur both in the cells (red colonies) and in the medium (red halos around colonies). The intensity of pigmentation was correlated with the intensity of the antimicrobial activity. Mutants that did not form pigment also lacked antifungal activity. Within the pigmented halos, conidia of the sensitive fungi did not germinate, and their hyphae did not grow and frequently lysed at the tips. Supplementation of the medium with iron reduced the size of the halos and the inhibition zones, while it increased the pigment accumulation by the colonies. The iron-binding agent tropolone had a similar effect, so I hypothesize that pigmented Metschnikowia isolates inhibit the growth of the sensitive microorganisms by pigment formation, which depletes the free iron in the medium. As the pigment is a large nondiffusible complex produced in the presence of both low and high concentrations of ferric ions, the proposed mechanism is different from the mechanisms operating in microbes that release siderophores into the environment for iron acquisition.

Quantitation of Hydroxyl Radicals from Photolysis of Fe(III)-Citrate Complexes in Aerobic Water (5 pp)

For their high photoreactivity, Fe(III)-carboxylate complexes are important sources of H2O2 for some atmospheric and surface waters. Citrate is one kind of carboxylate, which can form complexes with Fe(III). In our previous study, we have applied Fe(III)-citrate complexes to degrade and decolorize dyes in aqueous solutions both under UV light and sunlight. Results have shown that carboxylic acids can promote the photodegradation efficiency. It is indicated that the photolysis of Fe(III)-citrate complexes may cause the formation of some reactive species (e. g. H2O2 and *OH). This work is attempted to quantify hydroxyl radicals generated in the aqueous solution containing Fe(III)-citrate complexes and to interpret the photoreactivity of Fe(III)-citrate complexes for degrading organic compounds. By using benzene as the scavenger to produce phenol, the photogeneration of *OH in the aqueous solution containing Fe (III)-citrate complexes was determined by HPLC. In the aqueous solution containing 60.0/ 30.0 microM Fe(III)/citrate and 7.0 mM benzene at pH 3.0, 96.66 microM *OH was produced after irradiation by a 250 W metal halid light (lambda > or = 313 nm) for 160 minutes. Effects of initial pH value and concentrations of Fe(III) and citrate on *OH radical generation were all examined. The results show that the greatest from 3.0 to 7.0) was at pH 3.0. The photoproduction of *OH increased with increasing Fe(III) or citrate concentrations. In the aqueous solutions containing Fe(III)-citrate complexes, *OH radicals were produced after irradiation by a 250 W metal halide light. It can be concluded that Fe(III)-citrate complexes are important sources of *OH radicals for some atmospheric and surface waters. It is believed that the photolysis of Fe(III)-citrate complexes in the presence of oxygen play an important role in producing *OH both in atmospheric waters and surface water where high concentrations of ferric ions and citrate ions exist. The photoproduction of *OH has a high oxidizing potential for the degradation of a wide variety of natural and anthropogenic organic and inorganic substances. We can use this method for toxic organic pollutants such as organic dyes and pesticides.

Treatment of humic acids with ferric, aluminum, and chromium ions in water

The interaction of ferric, aluminum, and chromium ions with humic acids at different pH of mixture has been investigated. The concentration of metal ions, bound with humic acid is proportional to the concentration of metal ion in water solution at pH 3 at low metal ion concentrations. The ratio of the number of ferric ions, bound with humic acid, to the number of acidic groups in humic acid is more than 1.5 at high ferric ion concentration in solution. That is bound with the formation of dimers of ferric ions and their treatment with acidic groups of humic acid. The radius of particles formed in the reaction of humic acid with ferric ion does not depend on the pH and decreases in the reaction with chromium and aluminum ions at pH higher than 4. An increase of metal ion concentration leads to the increase of the particle radius at low metal ion concentration reaching the constant value at high metal ion concentration and pH 6.1.

Inhibitory effect of high concentrations of ferric ions on the activity of Acidithiobacillus ferrooxidans

The influence of high concentrations of ferric ions on the biochemical activity of Acidithiobacillus ferrooxidans was studied using intact cells. The specific oxidation rate of ferrous ions decreased with increasing ferric ion concentration. Lineweaver-Burk plots revealed typical competitive inhibition kinetics, because the slopes varied with the ferric ion concentration. A linear relationship between the slope and the square of the ferric ion concentration revealed that the iron-oxidizing enzyme system of A. ferrooxidans was competitively inhibited by about two molecules of ferric ion. The kinetic equation based on this inhibition model agreed with the experimental observation at a high ferric ion concentration where the bacterium is usually exposed in bioleaching and biooxidation plants.

Inhibitory Effect of High Concentrations of Ferric Ions on the Activity of Acidithiobacillus ferrooxidans

The influence of high concentrations of ferric ions on the biochemical activity ofAcidithiobacillus ferrooxidans was studied using intact cells. The specific oxidation rate of ferrous ions decreased with increasing ferric ion concentration. Lineweaver-Burk plots revealed typical competitive inhibition kinetics, because the slopes varied with the ferric ion concentration. A linear relationship between the slope and the square of the ferric ion concentration revealed that the iron-oxidizing enzyme system ofA. ferrooxidans was competitively inhibited by about two molecules of ferric ion. The kinetic equation based on this inhibition model agreed with the experimental observation at a high ferric ion concentration where the bacterium is usually exposed in bioleaching and biooxidation plants.