Concentration Of Iron In Solution Research Articles

Humic acid coated magnetic particles as highly efficient heterogeneous photo-Fenton materials for wastewater treatments

Heterogeneous photo-Fenton reaction with iron-based magnetic materials has been proposed as an alternative to the homogeneous Fenton process to remove contaminants of emerging concern (CECs) because of the low cost, facile recovery and reuse. The iron-based material is not only a reservoir to maintain an effective concentration of iron in solution, but it also activates H2O2 at the surface.Magnetic particles (MPs) coated with different amount of humic acid (HA), prepared by co-precipitation method under anoxic and oxygenated conditions were synthesized. Their features were characterized by different techniques (XPS, XRD, TGA, SEM and FTIR). The ability of those materials to promote Fenton and photo-Fenton-like processes was investigated using 4-chlorophenol as standard substrate. The HA coating increased the catalyst efficiency, both in the dark and under irradiation, showing the best performance at pH below 4 under simulated sunlight. The iron speciation at the MPs surface had a paramount role in the H2O2 (photo)activation, although the processes promoted by the released iron in solution were not negligible on the overall degradation process. It was demonstrated a role of the surface defectivity to promote faster degradations as a consequence of not only a faster photodissolution, but also a higher heterogeneous reactivity promoted by defective sites.The best performing MPs/HA showed high efficiency for the abatement of CECs, namely Carbamazepine, Ibuprofen, Bisphenol A and 5-Tolylbenzotriazole also in real wastewater. The obtained results demonstrated the potential application of the heterogeneous (photo)-Fenton process activated by these inexpensive and environmental friendly materials in advanced wastewater treatments.

Effects of different scrap iron as anode in Fe-C micro-electrolysis system for textile wastewater degradation.

The degradation of organic contaminants in actual textile wastewater was carried out by iron carbon (Fe-C) micro-electrolysis. Different Fe-C micro-electrolysis systems (SIPA and SISA) were established by using scrap iron particle (SIP) and scrap iron shaving (SIS) as anode materials. The optimal condition of both systems was obtained at the initial pH of 3.0, dosage of 30g/L and Fe/C mass ratio of 1:1. Commercial spherical Fe-C micro-electrolysis material (SFC) was used for comparison under the same condition. The results indicated that total organic carbon (TOC) and chroma removal efficiencies of SIPA and SISA were superior to that of SFC. Total iron concentration in solution and XRD analysis of electrode materials revealed that the former showed relatively high iron corrosion intensity and the physicochemical properties of scrap iron indeed affected the treatment capability. The UV-vis and 3DEEM analysis suggested that the pollutants degradation was mainly attributed to the combination of reduction and oxidation. Furthermore, the potential degradation pathways of actual textile wastewater were illustrated through the GC-MS analysis. Massive dyes, aliphatic acids, and textile auxiliaries were effectively degraded, and the SIPA and SISA exhibited higher performance on the degradation of benzene ring and dechlorination than that by SFC. In addition, SIPA and SISA exhibited high stability and excellent reusability at low cost. Graphical abstract.

Methylcellulose films partially crosslinked by iron compounds for medical applications

Methylcellulose (MC) is now widely used in medicine to fill defects of damaged tissues. A new method is proposed to improve the stability of MC-based materials in aqueous media using non-toxic reagents. MC–alginate blend films are crosslinked by iron(II) and iron(III) ions using different iron salts. The resulting films are stable in physiological solution for about 14 days. Mechanical tests of the dried films show an increase in the Young's modulus with iron concentration in solutions. Mössbauer spectroscopy data show that the films contain Fe3+ ions alone irrespective of whether chlorides of Fe2+ or Fe3+ are applied as crosslinking agents. The use of ascorbic acid as a complexing agent prevents Fe2+ from oxidation. The obtained materials are stable for at least half a year. The resulting films facilitate the growth of human fibroblasts on their surface.

Synthesis Features of Iron Oxide Nanopowders with High Magnetic and Sorption Properties

The magnetic particles of iron oxides are promising materials for the purification of water from ions of heavy metals and radionuclides. Their advantage compared to other sorbents is the ability to extract by applied magnetic field, which greatly simplifies the task of extraction, separation and processing in cleaning technologies. The aim of this work is investigation of temperature and concentration of iron in the solution effect on the phase composition, nanoparticle size and their magnetization. Phase magnetite in the sample increases with increasing temperature and the magnetization decreases slightly with increasing the initial concentration of iron in solution. We found that regardless of the conditions of deposition formed spherical particles whose average size ranges from 7 to 15 nm. The sorptive capacity of the particles is virtually independent of the phase composition and for cobalt is about 18 mg/g. For sorption-based material magnetic particles Fe3O4 recommended to carry out the deposition process at a temperature not lower than 80°C. The concentration of iron in solution must be within 0,15–0,3M. The particles obtained contain in their composition at least 90 wt.% of magnetite phase and are characterized by a magnetization in the range of 65–70 A·m2/kg. Also in the paper is comparing efficiency of extraction and sorption capacity for cobalt particles by different phase of magnetite and hematite.

Natural soil mediated photo Fenton-like processes in treatment of pharmaceuticals: Batch and continuous approach

This paper manifests the potential viability of soil as a cost-free catalyst in photo-Fenton-like processes for treating pharmaceuticals at large scale. Naturally available soil without any cost intensive modification was utilized as a catalyst to degrade pharmaceuticals, specifically ornidazole (ORZ) and ofloxacin (OFX). Soil was characterized and found enriched with various iron oxides like hematite, magnetite, goethite, pyrite and wustite, which contributes toward enhanced dissolution of Fe3+ than Fe2+ in the aqueous solution resulting in augmented rate of photo-Fenton reaction. The leached iron concentration in solution was detected during the course of experiments. The degradation of ORZ and OFX was assessed in solar induced batch experiments using H2O2 as oxidant and 95% ORZ and 92% OFX removal was achieved. Elevated efficiencies were achieved due to Fe2+/Fe3+ cycling, producing more hydroxyl radical leading to the existence of homogeneous and heterogeneous reactions simultaneously. The removal efficiency of solar photo-Fenton like process was also compared to photo-Fenton process with different irradiation sources (UV-A and UV-B) and were statistically analysed. Continuous-scale studies were conducted employing soil either in the form of soil beads or as a thin layer spread on the surface of baffled reactor. Soil beads were found to have satisfactory reusability and stability. 84 and 79% degradation of ORZ and OFX was achieved using soil as thin layer while with soil beads 71 and 68% degradation, respectively. HPLC and TOC study confirmed the efficient removal of both the compounds. Toxicity assessment demonstrates the inexistence of toxic intermediates during the reaction.

Destruction of humic substances by pulsed electrical discharge

Currently, the water recourses in the territory of Tomsk region are groundwater which is limited to the high concentration of iron and manganese ions and organic substances. These impurities present in water in different forms such as soluble salts ant the colloid forms. Therefore, the present work is a part of a continuations researcher of the processes in natural waters containing humic substances at the influence of pulsed electrical discharges in a layer of iron pellets. It is shown that the main stage of water purification process of humic substances during treatment by pulsed electric discharge in the layer of iron granules is a difficult process including several stages such as formation of iron oxyhydroxide colloid particles, sorption and coagulation with humic macromolecules substances, growth of particle dispersed phase and precipitation. The reason for the formation and coagulation of the dispersed phase is a different state of charge of the colloid particles (zeta potentials of (Fe (OH)3) is +8 mV, zeta potentials of (Humic substances) is -70 mV. The most intense permanganate oxidation reduction to the maximum permissible concentration occurs at the processing time equal to 10 seconds. The contact time of active erosion products with sodium humate is established and it equals to 1 hour. The value of permanganate oxidation achieves maximum permissible concentration during this time and iron concentration in solution achieves maximum permissible concentration after filtration.

Electropulse treatment of water solution of humic substances in a layer iron granules in process of water treatment

The present work is a part of a continuations study of the physical and chemical processes complex in natural waters containing humic-type organic substances at the influence of pulsed electrical discharges in a layer of iron pellets. The study of humic substances processing in the iron granules layer by means of pulsed electric discharge for the purpose of water purification from organic compounds humic origin from natural water of the northern regions of Russia is relevant for the water treatment technologies. In case of molar humate sodium - iron ions (II) at the ratio 2:3, reduction of solution colour and chemical oxygen demand occur due to the humate sodium ions and iron (II) participation in oxidation-reduction reactions followed by coagulation insoluble compounds formation at a pH of 6.5. In order to achieve this molar ratio and the time of pulsed electric discharge, equal to 10 seconds is experimentally identified. The role of secondary processes that occur after disconnection of the discharge is shown. The time of contact in active erosion products with sodium humate, equal to 1 hour is established. During this time, the value of permanganate oxidation and iron concentration in solution achieves the value of maximum permissible concentrations and further contact time increase does not lead to the controlled parameters change.

Extraction of nickel from ferromolybdenum leach residues

The extraction of nickel from ferromolybdenum leach residues by sulphation roasting, water leaching and iron removal from subsequent nickel leach solutions was studied. Sulphation roasting and water leaching promote the reaction between sulphuric acid and the residue and decrease the silicon dissolution. Over 90% of Ni was leached. Ferric ions in the solution could be effectively removed as jarosite and ferric hydroxide. The recovery of nickel reached 88·3% under sulphation roasting with the sulphuric acid quality of 1472 kg t−1 leach residue at 280°C for 4 h followed by iron removal with addition of 0·5 g NaClO3, 6 g Na2SO4 and 10 g CaO/100 mL solution at 95°C for 2·5 h, while the concentration of iron in solution reduced to 0·38 from 56·6 g/L−1.On a étudié l’extraction du nickel à partir de résidu de lessivage de ferromolybdène par grillage sulfateur, lessivage à l’eau et enlèvement du fer des solutions obtenues de lessivage de nickel. Le grillage sulfateur et le lessivage à l’eau favorisent la réaction entre l’acide s ulfurique et le résidu et diminuent la dissolution de la silice. On a lessivé plus de 90% du Ni. On pouvait enlever efficacement de la solution les ions ferriques sous forme de jarosite et d’hydroxyde ferrique. La récupération du nickel atteignait 88·3% au moyen du grillage sulfateur, avec 1472 kg d’acide sulfurique par tonne de résidu de lessivage à 280°C pendant 4 h, suivi par l’enlèvement du fer avec l’addition de 0·5 g de NaClO3, 6 g de Na2SO4 et 10 g de CaO par 100 mL de solution à 95°C pendant 2·5 h, la concentration du fer dans la solution étant réduite de 56·6 à 0·38 g L−1.

Factors controlling the precipitation of copper and cobalt minerals in sediment-hosted ore deposits: Advances and restrictions

An assessment is presented of existing data on the most important copper and cobalt complexes and sulphides applied to reactive transport modelling. The most important complexes in ore-forming hydrothermal solutions at 150°C are CoCl(H2O)5+, CoCl4−2 and CoCl2(H2O)2(aq) for cobalt, and CuCl2− and CuCl3−2 for copper. Reactive transport modelling was carried out to simulate the transport and precipitation of copper and cobalt sulphides in sediment-hosted stratiform ore deposits, such as the Central African Copperbelt. A limitation is the lack of thermodynamic data for carrollite (CuCo2S4). Initially chalcopyrite (CuFeS2) and cattierite (CoS2) precipitate in a reducing host rock. Pyrite dissolves in the horizon where both minerals form and it precipitates in adjacent rocks. The continuous supply of copper and cobalt causes formation of the metal-rich sulphides bornite (Cu5FeS4) and linnaeite (Co3S4). Chalcopyrite and cattierite precipitate further in the flow direction. In this model, the dissociation reaction of chalcopyrite and bornite are:CuFeS2(s)+2H+=Cu2++Fe2++2HS−Cu5FeS4(s)+2H+=4Cu++Cu2++Fe2++4HS−However, if the dissociation reactions only include Cu+ and Fe3+, simulations show the precipitation of only chalcocite (Cu2S), which is explained by the low concentration of trivalent iron in solution. The dissociation reactions are:CuFeS2(s)+2H+=Cu++Fe3++2HS−Cu5FeS4(s)+2H+=5Cu++Fe3++4HS−

Mössbauer spectroscopy study of iron complexes in a poly(methacrylic acid) hydrogel matrix

Using Mossbauer spectroscopy, we have studied iron complexes resulting from the interaction of aqueous iron salt solutions with poly(methacrylic acid) (PMAA) gel. In these complexes, the di- and trivalent Fe ions are linked to the PMAA through the COO− functional group. From the observed dynamics of the variation in the intensities of the di- and trivalent iron in the Mossbauer spectra of the gels with incubation time and iron concentration in solution, we have inferred a model for the incorporation of Fe ions into a gel matrix.

Synthesis and fluorescence properties of polystyrene via atom transfer radical polymerization using a coumarin derivate as initiator

Well-defined polystyrene was successfully synthesized via atom transfer radical polymerization, using a novel coumarin derivate, 2-bromo-2-methyl-propionic acid 4-methyl-2-oxo-2H-chromen-7-yl ester (BMP), synthesized in our lab as an initiator, and CuBr/N,N,N′,N′,N″-pentamethyldiethylenetriamine (PMDETA) as the catalyst at 110 °C. The kinetics of the polymerization was studied in detail. The fluorescence properties of the resultant polystyrenes were studied in N,N-dimethylformamide (DMF). It is very interesting that the adding of Fe3+ has significant effect on the fluorescence intensities, which decreased with increasing the concentration of iron in solutions. The obtained polystyrenes can be used as fluorescent probe molecules for Fe3+.

Recovery of manganese from electric arc furnace dust of ferromanganese production units by reductive leaching

Recovery of manganese from electric arc furnace dust (EAFD) of a ferromanganese production unit was investigated using reductive leaching in sulfuric acid (H2SO4). Three different reducing reagents, oxalic acid, hydrogen peroxide and glucose, were tested. Effect of different leaching parameters on the leaching and separation selectivity of manganese from iron was investigated. Iron concentration in solution was also determined, since iron was the major contaminant in the leach liquor. From the results complete leaching of manganese was achieved at 0.31mol/L oxalic acid concentration, 2mol/L H2SO4, a liquid/solid ratio of 30/1 at 70°C and with 90min leaching time.

Investigating heap bioleaching: Effect of feed iron concentration on bioleaching performance

This paper describes an investigation into the effect of iron concentration in the leach solution on the bioleaching of a low grade copper ore, where chalcopyrite was the dominant copper sulphide. The concentration of dissolved iron is primarily controlled by pH and the relative proportion of ferric to ferrous iron, with significant jarosite precipitation occurring above pH ≈ 1.8 in a highly oxidised system. The solution pH may be increased by the dissolution of acid soluble gangue and when iron oxidation is significantly higher than sulphur oxidation. The study was approached using two experimental systems. In the former, the leach solution was recycled through an ore bed of low aspect (reactor height divided by diameter) ratio for a portion of the experiment. During the recycle phase, no acid was added to the system and acid consumption by gangue material led to a pH increase (1.6–2.2). The resulting jarosite precipitation reduced soluble iron from 2.5 g/l to less than 250 mg/l. Copper recovery decreased, but not in proportion to the decrease in iron. This was partly attributed to adsorption on, or entrainment within, the jarosites. To study the effect of reduced iron concentration on leach performance under more controlled conditions, bioleaching was performed in packed bed column reactors with feed iron concentrations ranging from 5 g/l to 200 mg/l. Observations indicated an initial decreased rate of copper liberation with reduced iron concentration in the feed. The relationship between available Fe 3+ concentration and copper liberation was not proportional. However, with time, the liberation of copper became independent of iron concentration in the percolation liquor. Further, the specific rate of copper liberation was consistently below the theoretical value on a basis of ferric iron concentration. The highest values of copper liberation were reported at the lowest iron concentrations. In summary, while increased iron concentration in solution may enhance the initial rate of leaching, mineral availability appears to dominate CuFeS 2 leach kinetics through the majority of the leach. Furthermore, high iron concentrations in solution aggravate jarosite formation with concomitant retention of copper in the ore bed.

Process for biological oxidation and control of dissolved iron in bioleach liquors

Iron has a central role in bioleaching and biooxidation processes. Fe 2+ produced in the dissolution of sulfidic minerals is re-oxidized to Fe 3+ mostly by biological action in acid bioleaching processes. To control the concentration of iron in solution, it is important to precipitate the excess as part of the process circuit. In this study, a bioprocess was developed based on a fluidized-bed reactor (FBR) for Fe 2+ oxidation coupled with a gravity settler for precipitative removal of ferric iron. Biological iron oxidation and partial removal of iron by precipitation from a barren heap leaching solution was optimized in relation to the performance and retention time ( τ FBR) of the FBR. The biofilm in the FBR was dominated by Leptospirillum ferriphilum and “ Ferromicrobium acidiphilum.” The FBR was operated at pH 2.0 ± 0.2 and at 37 °C. The feed was a barren leach solution following metal recovery, with all iron in the ferrous form. 98–99% of the Fe 2+ in the barren heap leaching solution was oxidized in the FBR at loading rates below 10 g Fe 2+/L h ( τ FBR of 1 h). The optimal performance with the oxidation rate of 8.2 g Fe 2+/L h was achieved at τ FBR of 1 h. Below the τ FBR of 1 h the oxygen mass transfer from air to liquid limited the iron oxidation rate. The precipitation of ferric iron ranged from 5% to 40%. The concurrent Fe 2+ oxidation and partial precipitative iron removal was maximized at τ FBR of 1.5 h, with Fe 2+ oxidation rate of 5.1 g Fe 2+/L h and Fe 3+ precipitation rate of 25 mg Fe 3+/L h, which corresponded to 37% iron removal. The precipitates had good settling properties as indicated by the sludge volume indices of 3–15 mL/g but this step needs additional characterization of the properties of the solids and optimization to maximize the precipitation and to manage sludge disposal.

Synthesis and characterization of Fe(III)-montmorillonites for phosphate adsorption

Two Fe(III)-modified montmorillonites were synthesized by mixing Fe(III) nitrate solutions with montmorillonite at pH 3.5 followed by an increase in pH up to 9. The synthesis procedure was analyzed by solubility calculations and Fe(III) speciation in aqueous solutions, and the resulting solids were characterized by X-ray diffraction, specific surface area, Mössbauer spectroscopy, electrophoretic mobilities (EM) and phosphate adsorption. At low pH, iron concentration in solution during the synthesis is controlled by adsorption/intercalation reactions, whereas at high pH the concentration is controlled by the solubility of ferrihydrite. When the initial Fe(III) content is relatively low the synthesized solid contains mainly interlayer/sorbed Fe(III). When the initial Fe(III) content is relatively high the synthesized solid contains also some iron (hydr)oxide phases, mainly ferrihydrite. These Fe(III) phases are in close contact with montmorillonite, either coating the montmorillonite surface or aggregated with montmorillonite particles. The presence of Fe(III) species increases significantly the specific surface area and phosphate adsorption capacity, but changes only slightly the EM of the solid.

Pressure oxidative leaching of lead-containing copper matte

The pressure oxidative leaching of lead-containing copper matte is studied systematically. The effects of leaching time, oxygen partial pressure, leaching temperature, agitation speed, acid addition and initial Cu 2+ concentration on the extraction of copper and iron are investigated. The effect of initial Cu 2+ concentration is insignificant compared to the other reaction parameters. The best found conditions are: leaching time 2 h, oxygen partial pressure 0.8 MPa, acid addition 80% of matte mass, temperature 150 ± 5 °C and agitation speed 600 rpm. Under these conditions, > 95% Cu is extracted with the concentration of iron in solution < 5 g/L and the yield of sulfur is 20–30% of total sulfur mass. The leach residue is about 30% of the initial mass and the recovery of lead and silver is close to 100% and 98% respectively.

A novel preparation of titanium dioxide from titanium slag

A novel method of caustic hydrothermal decomposition of titanium slag followed by acidification of the sodium titanate product was adopted to prepare titanium dioxide. The effects of temperature, sodium hydroxide concentration, alkali-to-titanium slag mass ratio and reaction time on the titanium extraction were studied. Almost complete extraction of titanium was achieved when finely ground titanium slag (− 61/+51 μm) was reacted with a NaOH solution with a concentration of 10 mol kg − 1 H 2O and the alkali-to-titanium slag (based on TiO 2) mass ratio of 4:1 at 220 °C for about 4 h. The XRD pattern shows that the hydrothermal product obtained under optimal conditions was Na 4Ti 3O 8. Titanium dioxide with a rutile structure was obtained by acidification and cation exchange of Na 4Ti 3O 8. The effects of pH value, temperature, mass ratio of liquid-to-solid, and different acid medium on the product of cation exchange were studied together with the variation of titanium and iron concentration in solution. Under optimal conditions, the purity of titanium dioxide was > 99.0%.

The use of oxygen in high pressure acid leaching of nickel laterites

Preliminary leaching tests on a sample of limonitic laterite at 220°C, gave satisfactory recoveries of nickel. It was noted that a significant proportion of the iron remained in solution (about 11g/l) due to its presence as divalent iron. This was equivalent to about 55kg per ton of ore or 14% of the iron. The use of oxygen in the leach was investigated as a means of precipitating this iron as hematite and a few tests with oxygen were performed. Reaction with manganese dioxide was used subsequently, as a means of quantifying oxygen consumption and the ferrous content of the ore. A series of tests at various acid additions was used to test the benefit of oxidizing conditions. The concentration of iron in solution was reduced to about 1g/l when oxidizing conditions were used, resulting in a calculated saving in acid consumption of about 88kg/t. The data confirmed that the saving in acid consumption was of this order. The oxygen consumption of the ore, based on conversion of manganese dioxide, was very variable, with an average value of about 15kg/t. This is about twice the calculated value (of 7kg/t) based on reduction of iron in solution. This could imply that a similar proportion of ferrous iron was present in the residue.The use of a high temperature (270–280°C), for precipitation of ferrous compounds, may not necessarily reduce acid consumption, if these compounds contain sulphate or if they re-dissolve on cooling, as filtration at high pressure and temperature is required. The use of oxygen in the leach offers the potential of reducing acid consumption and eliminating unstable precipitates associated with ferrous compounds.

A study of the crystallization kinetics of scorodite via the transformation of poorly crystalline ferric arsenate in weakly acidic solution

Abstract In this work, the transformation of poorly crystalline ferric arsenate nanoparticle aggregates to polycrystalline scorodite particles (FeAsO4·2H2O) in an acidic nitrate medium (pH 2–4) and elevated temperature (40–80 °C) is described. Monitoring of the transformation process via different parameters such as arsenic and iron concentration in solution, iron to arsenic molar ratio in solid phase, or crystalline fraction in product, exhibited “S”-shape or sigmoidal kinetic curves, characteristic of an autocatalytic-type reaction. The lengths of the induction period and self-acceleration stage were found to depend strongly on pH and reaction temperature with the fastest transformation achieved at pH 2 and 80 °C. The transformation kinetics have been described by the Avrami–Erofeev nucleation-growth model. The selected nucleation-growth model along with FEG-SEM and FEG-TEM observations supplemented with SAED and microanalysis suggested that the mechanism of transformation involved crystallization within the amorphous precursor phase aggregates. The poorly crystalline ferric arsenate was found to contain an excess of iron, which was attributed to ferrihydrite co-precipitation. The minor ferrihydrite phase was found to convert to crystalline scorodite via a postulated mechanism that involves AsO4 ion adsorption, surface build-up of ferric arsenate and crystallization. TGA and XRD analysis revealed the final crystallization stage to be rather slow not leading to full development of crystalline structure even after 24 h ageing at pH 2 and 80 °C.

Mineral Iron Oxides as Iron Source in Electro-Fenton and Photoelectro-Fenton Mineralization Processes

Several low-soluble mineral iron oxides have been studied as an iron source for the production of hydroxyl radicals via decomposition in the presence of ferrous ions (Fenton’s reaction). In particular, this study focuses on electro-Fenton and photoelectro-Fenton processes, using aniline as a model pollutant. The aim of this work is to spread the use of iron minerals as catalyst in the different electrochemical wastewater treatments. Among all the iron oxides tested, magnetite and wustite show the more promising results. The main advantages of these minerals are that they produce lower concentrations of iron in solution, ease of recycling the iron catalyst, and their ability to self-regulate the concentration of iron ions in solution. Wustite and magnetite behave purely as a source of iron ions in the electro-Fenton process. But, magnetite exhibits a heterogeneous photocatalytic effect when used as an iron source in the photoelectro-Fenton process. This new magnetite-photoelectro-Fenton process significantly improves the pollutant removal yield (16.7% more after of mineralization) compared to the conventional photoelectro-Fenton process. This effect is observed for two different wavelengths in the UV range, 254 and .