Iron Salt Concentration Research Articles

Fenton type processes for minimization of organic content in coloured wastewaters: Part I: Processes optimization

This study was focussed on the application of Fenton (Fe 2+/H 2O 2) and Fenton “like” processes (Fe 3+/H 2O 2 and Fe 0/H 2O 2) for the minimization of organic content of coloured synthetic wastewaters. Two reactive dyes, C.I. Reactive Blue 49 with anthraquinone chromophore and C.I. Reactive Blue 137 with azo chromophore were used as model organic pollutants. Fenton type processes were investigated in order to establish optimal operating conditions (pH, concentration of iron salts or iron powder, and ratio of Fenton reagent) for the maximal degradation of investigated model coloured wastewaters. Degradation of studied dyes as organic pollutants was monitored on the basis of decolourization and mineralization extents of model solutions, determined by UV/vis spectrophotometric, and TOC and AOX analyses, respectively. Colour removal > 95% was achieved by all the applied processes, while mineralization extents ranged between 34 and 72% depending on the dye structure and applied AOP.

Bacterial Crowd Control with Iron

Bacterial biofilms account for more than 80% of human infections. Hergenrother and coworkers report in this issue that high concentrations of iron salts can block the formation of these bacterial communities; this represents an attractive new method for biofilm control.

Effect of aluminum and iron on lipid metabolism in aquatic invertebrates

Methods of thin-layer, gas-liquid, and liquid chromatography were applied to the study of the effect of various concentrations of aluminum and iron salts on the contents of phospholipids, cholesterol, and fatty acids in the aquatic invertebrate Hydropsyche contubernalis L. (Trichoptera). It was found that the effect of the metals under study on lipid contents in living organisms depended on the composition of the aqueous medium and concentrations of the metals. Aluminum and iron altered the value of the cholesterol-to-phospholipid molar ratio. In the absence of lethal effects, this was indicative of attempts to switch adaptational biochemical mechanisms to stabilize cellular structures.

Formation of magnetite nanoparticles in poly(acrylamide) gels

Magnetic gels with magnetite nanoparticles incorporated in a matrix of poly(acrylamide)gel were studied. Magnetite was synthesized through coprecipitation of Fe(II) and Fe(III) inthe gel phase, in the solution of linear polymer and in aqueous solution without polymer inalkaline media. The effects of network structure and of the concentration of iron salts in theswollen networks on the composition, structure and properties of magnetic gels havebeen studied by electron diffraction, XRD, transmission electron microscopy andvibration sample magnetometry. The average size of magnetite nanoparticles,D, is of the order of 10 nm. It decreases with the increase of polymer concentration in the gelphase. In the dried gels the particles form spherical aggregates (diameter about 150 nm),whereas in the solution of linear polymer, in the aqueous solution of iron saltsand in the gel with high content of polymer the aggregates have irregular shape.

Inhibition of copper-catalyzed cysteine oxidation by nanomolar concentrations of iron salts

Problems caused by the presence of adventitious metals in buffers and reagents are well recognized in studies of metal-catalyzed oxidation reactions. In most cases, metal contamination leads to an increase in rate, and chelating agents are inhibitory. In the present study, however, the rate of copper-catalyzed oxidation of cysteine was found to be increased by buffer purification with Chelex resin or by addition of micromolar concentrations of the specific iron chelator desferrioxamine (DFO). These effects are attributable to inhibition of copper-catalyzed oxidation by adventitious iron. In purified buffer at pH 7.25, containing 0.4 μM copper, cysteine was oxidized at a rate of 32 μM/min. Addition of iron salts to this buffer caused a dose-related decrease in this rate, up to a maximum of 85%. A 50% decrease in rate was recorded at an iron concentration of only 11 nM. Other transition metals were without effect. Similar effects of purification or addition of DFO on the rate of cysteine oxidation were seen in Tris, glycylglycine, Mops, and Pipes buffers. Catalase decreased the rate of cysteine oxidation, but the sensitivity to iron was similar in the presence and absence of catalase. Copper-catalyzed oxidation of cysteamine and reduced glutathione was much less sensitive to inhibition by iron. Our results offer an explanation for the conflicting literature reports of the effects of chelating agents and catalase on cysteine oxidation, and emphasize the need for buffer purification or addition of DFO in studies concerned with the oxidation or cytotoxicity of this thiol. The exceptional sensitivity of copper-catalyzed cysteine oxidation to iron makes this an attractive system for monitoring the iron content of buffers, and may also have application for determining the free iron content of physiological fluids.

Practical applications of the Fenton reaction to the removal of chlorinated aromatic pollutants. Oxidative degradation of 2,4-dichlorophenol.

Chlorophenols (CPs) constitute a group of organic pollutants that are introduced into the environment as a result of several man-made activities, such as uncontrolled use of pesticides and herbicides, and as byproducts in the paper pulp bleaching. Promising removal technologies of chlorinated aromatics consist in the application of advanced oxidation processes (AOPs) that can provide an almost total degradation of a variety of contaminants. Among these, wide application find Fenton systems based on generation of reactive species having a high oxidizing power, such as hydroxyl radical HO*. Our objective was that of determining the overall degradation efficiency of the model compound 2,4-dichlorophenol (DCP) by thermal Fenton-type oxidation systems with a view toward defining in more details relevant process parameters, the effect of reaction temperature and of co-catalyst Cu2+. Reaction conditions were similar to those generally adopted as optimal in many practical applications, i.e. pollutant/Fe2+ (as FeSO4) ratio ca. 20, Fe2+/Cu2+ (co-catalyst) 2:1, pH adjusted and controlled at pH 3, and H2O2 in excess (up to four-fold over the stoichiometric amount required for complete mineralization). The results demonstrate that it is advantageous to carry out the reaction at a temperature markedly higher (70 degrees C) than ambient. The stepwise addition of H2O2 in aliquots yields an efficient transformation, while allowing a convenient control of the reaction exothermicity. Under these conditions, the essentially complete removal of the initial DCP is accomplished using just one equiv of H2O2 during 15 min; excess H2O2 (5 equivalents) yields extensive substrate mineralization. Also relevant, at 70 degrees C dechlorination of the initial DCP (and of derived reaction intermediates) is remarkably extensive (3-5% residual TOX), already with the addition of 1 equiv of H2O2. At the end of the reaction, IC and IC-MS analyses of the solution reveal that only low-molecular weight carboxylic acid (acetic, formic, oxalic, malonic, tartaric, etc.) contribute to the residual TOC. The whole of the results herein point to the advantage of performing the process at temperatures substantially higher than ambient (70 degrees C). Under the conditions adopted, almost complete degradation of the initial toxic compound can be achieved using hydrogen peroxide in fair excess (e.g., 3.5 equiv H2O2). In applying practical Fenton-type degradation systems to heavily polluted wastes, either for the pre-treatment of waters with a high COD value prior to biodegradation or for complete mineralization of pollutants, the set up of appropriate reaction conditions appears to be a key factor. Also, it is desirable to keep the concentration of iron salts within the lower limits in order to minimize the production and disposal of iron oxide sludges.

Destratification of an impounding reservoir using compressed air––case of Mudi reservoir, Blantyre, Malawi

This paper reviews the operational and cost effectiveness of a compressed air destratification system that was installed in the Mudi reservoir for destratifying the reservoir. Mudi reservoir is a raw water source for the Blantyre Water Board. It has a capacity of 1,400,000 cubic metres. The reservoir is 15.3 m deep at top water level. In the absence of any artificial circulation of air, the reservoir stratifies into two layers. There is a warm epilimnion in the top 3 m of the reservoir, with temperatures ranging from 23 to 26 °C. There is prolific algal growth in this layer. The bottom layer has much lower temperatures, and is oxygen deficient. Under such anaerobic conditions, ammonia, sulphides, iron and manganese are released from the sediments of the reservoir. As a result of nutrient inflow from the catchments, coupled with tropical ambient temperatures, the reservoir is most times infested with blue-green algae. This results into water treatment problems in respect of taste and odour and iron and manganese soluble salts. To abate such problems, air is artificially circulated in the reservoir, near the intake tower, through a perforated pipe that is connected to an electrically driven compressor. This causes artificial circulation of water in the hypolimnion region of the reservoir. As a result of this circulation, a hostile environment that inhibits the propagation of algae is created. Dissolved oxygen and temperature profiles are practically uniform from top to bottom of reservoir. Concentrations of iron and manganese soluble salts are much reduced at any of the draw-off points available for the water treatment process. The paper concludes by highlighting the significant cost savings in water treatment that are accrued from the use of compressed air destratification in impounding water storage reservoirs for the control of algae and other chemical pollutants.

Effect of the medium composition and cultivation conditions on sporulation in chemolithotrophic bacteria

The possibility of controlling endospore formation by changing cultivation conditions was for the first time shown in acidophilic chemolithotrophic bacteria Sulfobacillus thermosulfidooxidans type strain 1269 and the thermotolerant strain K1 formerly described as "S. thermosulfidooxidans subsp. thermotolerans". Suppression of sporulation occurred when these strains were cultured in Manning's liquid medium with yeast extract. This medium was optimized by gradually reducing the concentrations of ferrous iron salts (the source of energy), phosphorous, nitrogen, and yeast extract and simultaneously increasing the concentrations of calcium, magnesium, and manganese (the elements important for sporogenesis) to attain higher yields of endospores by strains 1269 and K1. As a result, a new medium A was proposed, in which the life cycle of the strains studied culminated in sporulation at a level of 45 and 60%, respectively, of the total cell number. In a series of additional tests, the growth temperature and medium pH were adjusted to obtain the maximum yield of endospores. The optimal ranges found were 40-50 degrees C and pH 1.8-2.2 for strain 1269 and 35-40 degrees C and pH 2.5-2.7 for strain K1. An even higher yield of endospores, amounting to 55 and 75% for strains 1269 and K1, respectively, was obtained when the above growth conditions were combined (growth on medium A at optimal temperatures and pH). Our results suggest a new approach to optimizing sporulation by acidophilic chemolithotrophs, which consists in limiting the energy and nutrient sources and using temperature and pH values within the tolerance bounds of these cultures but outside their growth of optimum ranges.

Optimal experimental design and artificial neural networks applied to the photochemically enhanced Fenton reaction

Among advanced oxidation processes (AOPs), the photochemically enhanced Fenton reaction may be considered as one of the most efficient for the degradation of contaminants in industrial wastewater. This process involves a series of complex reactions. Therefore, an empirical model based on artificial neural networks has been developed for fitting the experimental data obtained in a laboratory batch reactor for the degradation of 2,4-dimethyl aniline (2,4-xylidine), chosen as a model pollutant. The model describes the evolution of the pollutant concentration during irradiation time as a function of the process conditions. It has been used for simulating the behavior of the reaction system in sensitivity studies aimed at optimizing the amounts of reactants employed in the process, an iron(III) salt and hydrogen peroxide, as well as the temperature. The results show that the process is most sensitive to the concentration of iron(III) salt and temperature, whereas the concentration of hydrogen peroxide has a minor effect.

Modeling the kinetics of a photochemical water treatment process by means of artificial neural networks

We have investigated the kinetics of the degradation of 2,4-dimethyl aniline (2,4-xylidine), chosen as a model pollutant, by the photochemically enhanced Fenton reaction. This process, which may be efficiently applied to the treatment of industrial waste waters, involves a series of complex reactions leading eventually to the mineralization of the organic pollutant. A model based on artificial neural networks has been developed for fitting the experimental data obtained in a laboratory batch reactor. The model can describe the evolution of the pollutant concentration during irradiation time under various conditions. It has been used for simulating the behavior of the reaction system in sensitivity studies aimed at optimizing the amounts of reactants employed in the process — an iron(II) salt and hydrogen peroxide. The results show that the process is much more sensitive to the iron(II) salt concentration than to the hydrogen peroxide concentration, a favorable condition in terms of economic feasibility.

Using iron-coated spent catalyst as an alternative adsorbent to remove Cr(VI) from water

The feasibility of utilizing iron-coated spent catalyst to adsorb Cr(VI) from aqueous solution was studied. Various factors, such as types and concentrations of iron salt, pH, and initial Cr(VI) concentration were investigated. A significant increase in Cr(VI) removal capacity can be achieved through iron-coating. The maximum adsorption was found at pH of 3.0-4.0. The presence of chloride and sulfate ions were found to suppress Cr(VI) adsorption. Langmuir adsorption isotherm was utilized to describe the adsorption reaction. Results from zeta potential measurement indicate that Cr(VI) is adsorbed largely through electrostatic interaction onto iron-coated spent catalyst. This study shows that spent catalyst can be converted to a useful adsorbent for Cr(VI) removal.

Using iron-coated spent catalyst as an alternative adsorbent to remove Cr(VI) from water

The feasibility of utilizing iron-coated spent catalyst to adsorb Cr(VI) from aqueous solution was studied. Various factors, such as types and concentrations of iron salt, pH, and initial Cr(VI) concentration were investigated. A significant increase in Cr(VI) removal capacity can be achieved through iron-coating. The maximum adsorption was found at pH of 3.0–4.0. The presence of chloride and sulfate ions were found to suppress Cr(VI) adsorption. Langmuir adsorption isotherm was utilized to describe the adsorption reaction. Results from zeta potential measurement indicate that Cr(VI) is adsorbed largely through electrostatic interaction onto iron-coated spent catalyst. This study shows that spent catalyst can be converted to a useful adsorbent for Cr(VI) removal.

Enhanced Removal of As(V) from Water with Iron-Coated Spent Catalyst

The effectiveness of pretreating a spent catalyst with an iron-salt solution to improve its As(V) removal capacity was studied. Various factors, such as types and concentrations of iron salt, pH. and initial As(V) concentration were investigated for their effects on the improvement of As(V) removal capacity. A significant increase in As(V) removal capacity can be achieved by iron-coated spent catalyst. Adsorption density of As(V) decreased with increasing pH. Langmuir adsorption isotherm was utilized to describe the adsorption reaction. Results from IR analysis and zeta potential measurement indicate that As(Y) is specifically adsorbed onto iron-coated spent catalyst. This study shows that spent catalyst can be converted to a useful adsorbent for As(V) removal.

Transferrin-independent iron uptake supports B lymphocyte growth

Raji, a malignant B-lymphocyte cell line containing Epstein-Barr virus genomic elements, has been conditioned to proliferate optimally in transferrin (Tf)-free medium containing a very low concentration of an iron salt. We provide evidence that an Tf-independent iron uptake system is physiologically important for maintaining the growth of these cells. The data show that Raji cells take up iron from iron salts using a relatively high-capacity, low-affinity, temperature- and calcium- dependent uptake system. The apparent capacity of this system increases when: (1) cells are cultured in Tf-free medium containing high concentrations of iron salt as opposed to medium containing Tf; and (2) when the iron salt concentration of Tf-free medium is lowered to about 1.6 mumol/L. Cellular iron uptake also increases when a maximum number of cells are in S and G2 and M cell phases of the cell cycle. The cells are sensitive to growth inhibition by the addition of deferoxamine. This evidence supports the hypothesis that certain malignant lymphocytes, under iron deplete conditions, fulfill an iron requirement for proliferation by an adaptation such as Tf-independent iron uptake.

Transferrin-Independent Iron Uptake Supports B Lymphocyte Growth

Raji, a malignant B-lymphocyte cell line containing Epstein-Barr virus genomic elements, has been conditioned to proliferate optimally in transferrin (Tf)-free medium containing a very low concentration of an iron salt. We provide evidence that an Tf-independent iron uptake system is physiologically important for maintaining the growth of these cells. The data show that Raji cells take up iron from iron salts using a relatively high-capacity, low-affinity, temperature- and calcium-dependent uptake system. The apparent capacity of this system increases when: (1) cells are cultured in Tf-free medium containing high concentrations of iron salt as opposed to medium containing Tf; and (2) when the iron salt concentration of Tf-free medium is lowered to about 1.6 mumol/L. Cellular iron uptake also increases when a maximum number of cells are in S and G2 and M cell phases of the cell cycle. The cells are sensitive to growth inhibition by the addition of deferoxamine. This evidence supports the hypothesis that certain malignant lymphocytes, under iron deplete conditions, fulfill an iron requirement for proliferation by an adaptation such as Tf-independent iron uptake.

Superoxide radical as electron donor for oxidative phosphorylation of ADP

When isolated rat heart mitochondria are subject to xanthine/xanthine oxidase generated free redicals, nmol quantities of ADP are phosphorylated to ATP. This effect is proportional to xanthine oxidase concentration, and is relatively independent of ADP concentration. Exogenous superoxide dismutase partially suppresses the phosphorylation. Micromolar concentrations of iron salts completely eliminate the phosphorylation. Catalase has no effect. The likely electron source, then, is superoxide radicals. The reduced minus oxidised spectra of superoxide-bombarded mitochondria show that superoxide enters the electron transport chain by reducing cytochrome c and complex IV. Mitochondria retain their ability to phosphorylate ADP in more traditional ways under the experimental conditions described. Superoxide under physiological conditions in vivo may be a source of electrons for the oxidative phosphorylation of ADP.

The role of free radical-mediated processes in oxygen-related damage in cultured murine myocardial cells.

A new approach to quantifying myocyte cell death utilizing fluorescence-activated sorting of antimyosin antibody-labeled cells was used to study the effects of oxygen-generated free radicals on cell survival. Uptake of antimyosin, reflecting sarcolemmal damage, increased under conditions which promoted elevated free radical formation and decreased in the presence of increased levels of free radical-scavenging agents. Superoxide dismutase decreased antimyosin uptake at pH 6.7 and 7.5. Mannitol decreased antimyosin uptake at pH 6.5 and 6.7 but not at pH 7.5, and dimethyl sulfoxide decreased antimyosin uptake at pH 6.4 but not at pH 7.5. These data suggest that a greater portion of hydroxyl radicals are produced at higher concentrations of hydrogen ion. Mannitol, a scavenger of hydroxyl radicals, was effective in reducing antimyosin uptake at pH 7.5 in the presence of ferrous sulfate, but had no effect on antimyosin uptake in the absence of ferrous sulfate, suggesting possible iron-mediated catalysis of hydroxyl radical formation. The data suggest that oxygen-derived free radicals can cause significant loss of membrane integrity in cultured myocytes, that the species of radical formed is dependent both on pH and the concentration of iron salts, and that this injury is, at least in part, preventable by the administration of exogenous radical scavenging agents.

Superoxide-dependent formation of hydroxyl radicals in the presence of iron salts: What is the physiological iron chelator?

In the presence of physiological concentrations of iron(III) salts, superoxide radical and hydrogen peroxide can interact to form the highly-damaging hydroxyl radical. No specific added ‘chelator’ of iron salts is necessary for this reaction to occur.

A mechanistic study of the decomposition of phenylhydroxylamine to azoxybenzene and aniline and its catalysis by iron(II) and iron(III) ions stabilised by ethylenediaminetetra-acetic acid

The catalysis by FeII and FeIII of the slow decomposition 3PhNHOH → PhN2OPh + PhNH2 has been investigated kinetically under nitrogen by quantitative u.v. and e.s.r. spectroscopy and by potentiometric measurements at pH 6–8 in aqueous 30% t-butyl alcohol containing EDTA. The reactions of nitrosobenzene with (a) phenylhydroxylamine and (b) FeII have been examined similarly and a mechanism for all these reactions is put forward. Small percentages of nitrosobenzene and of phenylnitroxide radicals are formed during all these reactions and the rapidly attained equilibria (i) and (ii) appear to control their concentrations, the much slower formation of azoxybenzene being due to the dimerisation (iii). Aniline formation is due to reaction (iv) PhNO + 2FeII+ 2H+⇌ PhNHOH + 2FeIII(i), PhNO + PhNHOH ⇌ 2 PhNHO·(ii), 2 PhNHO·→ PhN2OPh + H2O (iii) of which the first stage must be (V) and becomes dominant when high percentages of FeII are used. Reaction 2 FeII+ PhNHOH + 2H+→ PhNH2+ 2FeIII+ H2O (iv), FeII+ PhNHOH → PhNH·+ FeIII+(OH)–(v)(iv) does not appear to be pH dependent. Azoxybenzene formation, initiated by reaction (vi), occurs more rapidly the higher the pH, this being due to the effect of base on the [PhNO]:[PhNHOH] ratio controlled by equilibrium (i). With low percentages of FeII or FeIII catalysts, the reaction velocities approximately depend FeIII+ PhNHOH → PhNHO·+ FeII+ H+(vi) on the total iron salt concentration. Under these conditions the transient PhNO concentrations change so slowly with time that both the decomposition of PhNHOH and the formation of azoxybenzene become pseudounimolecular processes. The noteworthy feature of this transition metal catalysed decomposition is the kinetic control of a sequence of one-electron transfer reactions by the formation of a molecular intermediate (PhNO).

Effect of Iron and Magnesium on Manganese Metabolism

THERE are many areas in which water for livestock and poultry consumption contains high concentrations of iron and magnesium salts. In Iowa, a number of cases of leg problems with swine and turkeys have been reported from these areas. Furthermore, the Iowa State University Diagnostic Laboratory has diagnosed these leg problems to be due to nutritional rather than pathological causes.Leg disorders commonly observed in turkeys appear to be the gross symptoms of perosis. A dietary manganese deficiency has been found to cause perosis, (Ringrose et al., 1939). Excessive amounts of some minerals can be toxic to poults or can act as antagonists of other minerals. For example, magnesium has been known to be an antagonist of some minerals, especially calcium, and Wilgus and Patton (1939) found that ferric hydroxide and iron citrate decreased the diffusable manganese in the intestinal tract.The primary objective of the studies reported herein was…