Iron Sulfate Solution Research Articles

Determination of saturated dissolved oxygen concentration in iron sulfate solutions containing iron oxidizing microorganisms

Iron sulfate solutions and the extremophile lifeforms that can live within them are industrially and environmentally important in many applications and require proper assessments of solution properties. Determination of saturated dissolved oxygen concentration is an important parameter for monitoring iron biooxidation processes. However, its determination is not so straight forward using commercially available dissolved oxygen meters. Such meters utilize internal calculation models based on the saline properties of seawater which can be easily overlooked. A method for determination of the saturated dissolved oxygen concentration in acidic iron sulfate solutions with the inclusion of other inorganic salts is proposed in this work using the biooxidation of ferrous iron as an indicator measured with redox potential and converted to oxygen concentration through bioreaction stoichiometry. The technique was tested on a BioGenerator system over the course of four days and proved satisfactory in establishing a value for the saturated dissolved oxygen concentration of the bioreactor broth. Study of the lifespan properties of the microorganisms in absence of ferrous iron substrate was briefly examined to determine the effective handling period of solutions for assessment.

Hydrogen production from iron sulphate photolysis using mark-5 cycle

ABSTRACT Hydrogen production was carried out in a photochemical device in a Mark-5 cycle. The photolysis of iron sulphate solution was carried out in a close periodic system. The reaction mixture was 8.5 g iron sulphate compound (FeSO4•7 H2O), 2.5 g I2 and 1.0 g HI in 100 mL water. Fifty millilitres of this solution was filled into a quartz reactor and connected to cycle system. The optimisation of hydrogen production was achieved by temperature, flow rate and radiation irradiation. The maximum hydrogen generated was 50.0 × 1016 molecules per minute at 120 °C temperature, 0.08 mL/sec. Pump speed, pressure 0.30 MPas, and Hg-vapour λmax = 365 nm. Eact. = 14.92 kC/mol caused bimolecular reactions to occur at low temperatures by photochemical action. Quantum yield of hydrogen depended on the absorbed of 0.5 × 1015 kvant/s. The energy of the quantum above T ≥ 100°C temperatures was φ ≥ 1. The dependence of the hydrogen generation rate (W) increased from 0.001 to 0.0038 × 1016 molecules/sec at 10-90 minutes, respectively.

Determination of the efficiency of oxygen removal from water from the ratio of the concentrations of sodium sulfite and the iron catalyst

The main issue of corrosion activity is the removal of oxygen from water. Under certain conditions, inhibitors-passivators are effective. Other methods based on thermal and vacuum deaeration of water. These methods are energy-consuming and do not provide the necessary quality of water, so chemical reagents are used for deep deoxidation of water regardless of secondary pollution.
 In this work, distilled water with a certain concentration of oxygen was placed in a hermetic container. The calculated amount of sodium sulfite solution (sodium metabisulfite) was added to the water and after certain intervals the oxygen concentration in the water was recorded using an oxygen meter, the sensor of which was placed in the container before. In another series of experiments, calculated amounts of sodium sulfite and iron sulfate solutions were added to the water, the container was quickly closed and the oxygen concentration in the water was recorded at certain intervals.
 It has been shown that in distilled water at room temperature, sodium sulfite interacts very slowly with oxygen. In 1 hour, the rate of oxygen recovery increases from 27.7 % to 56.9 % when the sulfite concentration increases from 50 to 300 mg/dm3. It was established that iron (II) ions significantly accelerate the rate of oxygen reduction by sulfite already at an iron concentration of 0.1 mg/dm3 at a sulfite concentration of 50-300 mg/dm3. According to the integral kinetic curves of the 0th, 1st, 2nd, and 3rd orders, kinetic models of sulfite oxidation in distilled water with oxygen in the presence of iron ions were determined.
 It is shown that when the concentration of sulfite increases to 200, 300 mg/dm3, with an iron concentration of 0.5‑1.0 mg/dm3, the oxidation processes follow first-order reactions and their speed is determined by the oxygen concentration. When the concentration of iron and sulfite is reduced, the realization of oxidation processes according to the reactions of the 2nd and 3rd orders was noted, when the speed of the process depends not only on the concentration of oxygen, but also on the concentration of sulfite (2nd order) and iron ions (3rd order) .
 This work is aimed at solving the relevance of the problem of water deoxidation for water preparation in cooling systems. The direction of the research is very promising considering the satisfactory and effective results obtained and the inexpensive chemical reagents used. Further research will be aimed at finding ideal conditions for the reaction and finding optimal concentrations of reagents while ensuring maximum efficiency of the process, which in turn will bring mankind a solution to the problem of spending large amounts of money, chemical reagents and environmental pollution.

Devising a comprehensive technology for treating industrial iron sulfate-containing effluents of galvanic production

The object of the research is complex electrochemical and ferritic decontamination of iron sulfate-containing waters. Processing of liquid waste is carried out by electrochemical treatment using two- and three-chamber electrolyzers. This paper investigates the processes of electrodialysis purification of simulated solutions with an FeSO4 compound concentration of 5 g/dm3 and an H2SO4 compound concentration of 300–2100 mg-equiv/dm3. A plate made of stainless steel was used as the cathode, and a plate made of titanium covered with ruthenium oxide and lead was used as the anode. It is shown that the highest current yield of electrodialysis products of 84.5 % was obtained when using a three-chamber electrolyzer with MA-41 anion exchange membranes. It was found that when using the specified electrolyzer, the concentration gradient, the value of which is directly proportional to the difference in the concentrations of the initial solutions filled with the electrode chambers, has a significant effect on the process of separation of impurities. It is shown that for a two-chamber electrolyzer, the current output reaches 72 %, which is explained by the harmful effect of a significant concentration gradient and is manifested in the rapid mechanical blocking of the membrane and the slowing down of the ion migration process, as well as the increase in energy consumption. In a two-chamber electrolyzer, H2SO4 with a concentration of 18.3 % was obtained, which is suitable for repeated use in etching baths. It was found that as a result of electrodialysis separation and additional oxidation, it is advisable to use concentrated iron sulfate solutions for obtaining ferrite material of a crystalline structure with particle sizes of 2–20 μm. Within the framework of the circular economy, an ecologically safe technology for decontamination of industrial iron-containing sulfate solutions of galvanic production using a complex of electrodialysis and ferrite methods is proposed

Optimization of FeSO4 Molarity for Synthesis of Prussian Blue Pigment from Iron Sand from Sunur Beach Estuary, Pariaman

The objective of this research was to see how the molarity of Iron(II) sulfate (FeSO4) solution affected the coloring of the Prussian blue pigment produced, to find the best synthesis conditions. The coprecipitation methods were used to synthesize Prussian blue from FeSO4 and K3[Fe(CN)6] solutions. The molarity of iron(II) sulfate (FeSO4) was varied to 0.005 M, 0.0025 M, and 0.00125 M in this research, with the resulting products referred to as K1, K2, and K3. The UV-Visible spectrophotometer was used to analyze the produced pigment. The molarity of Iron(II) sulfate (FeSO4) impacts the final Prussian blue pigment, as observed in the experiment with variations in the molarity of FeSO4. The optimum color of Prussian blue, with a peak near-standard UV-Visible spectra at 686 nm, was produced at 11.85 mM FeSO4 molarity, which was very much by the standard absorbance wavelength Prussian blue pigment.

Production of iron-enriched kale leaves (Brassica oleracea L. var. acephala) utilizing combinations of novel food processing technologies

Despite its rich content, iron bioavailability from leafy greens is low relative to protoporphyrin-bound (e.g. heme) iron, richest in red meat. We hypothesized that combinations of novel food processing techniques, i.e., vacuum impregnation (VI), water-bath (WB), overnight immersion (IM) in an iron sulfate solution, and moderate electric field (MEF) could improve kale leaf iron content and produce protoporphyrin-bound iron derivatives in situ. Combination MEF treatments increased leaf iron concentrations ∼160x greater than control. A ferroprotoporphyrin IX isomer was detected in MEF and IM-treated kale, providing up to 0.75 mg protoporphyrin-bound iron/100 g kale leaf fresh weight (FW). IM and MEF treatments also significantly increased leaf total chlorophyll concentrations ∼3x greater than the control. The novel food processing techniques employed herein produced kale with significantly higher concentrations of free + heme-bound iron, as well as total chlorophyll, relative to other plant-based sources. Future testing will determine if this “iron-enhanced” kale delivers more iron, as compared to other iron-rich food sources.

Degradation Characteristics and Mechanism of Black Sandy Dolomite with Fluid Added in a Mechanical Test

Sandy dolomite, being a soluble rock, is prone to dissolution and erosion caused by groundwater, leading to the formation of underground caves and fractures. This may result in geological disasters such as ground subsidence and collapse. In this paper, the changes and mechanical properties of black sandy dolomite after hydrochemistry are studied. A semi-immersion test with different concentrations of iron sulfate solution was carried out to simulate the water-rock interaction in different water environments. After that, scanning electron microscope (SEM) results could reflect the dissolution and pore development of rock by the effect of water-rock interaction from the microscopic. Water-rock interaction enlarges cracks in rocks and dissolves pyrite, carbonate minerals, and other components, reducing the cementation between particles. The change in the mechanical properties of black sandy dolomite under water-rock chemical interaction was revealed by uniaxial compression test. The mechanical properties of the samples exhibit varying degrees of deterioration, with strain increased ranging from 4.96 to 29.58%. The brittleness index modified (BIM) values for each sample ranged from 5.20 to 6.20%, all of which are larger than 4.70% in the natural state.

Imaging Techniques of Tomatoes (Solanum Lycopersicum L.) Grown with Different Organic and Conventional Fertilizer Applications

In this study, which was carried out in field conditions in Van in 2019 and 2020, different image generation methods (biocrystallization method, and circular and rising picture chromatography methods) were used to determine the difference between various organic and conventional fertilizer applications. 3% frozen tomatoes and 16% CuCl2.2H2O were applied in the biocrystallization method, 80% frozen tomatoes and 1% silver nitrate solution were used in the circular chromatography method, and 100% frozen tomatoes and 0.5% silver nitrate and 0.5% iron sulfate solution were employed in the rising picture method. In light of the visual findings obtained at the end of the study, it has been determined that there are some differences between organic and conventional fertilizer applications. As the alteration between organic and conventional products; the center number difference in the copper crystallization method; the smoothness of the rings formed in the circular chromatogram and the vividness of the colors; in the rising painting method, it clearly reveals the transitions between colors and the difference in light and dark tones that occur in colors.

Simultaneous removal process of hydrogen sulfide and siloxanes and field application of iron hydroxide desulfurization agent for green hydrogen production from biogas

Biogas, one of renewable energies, is a key element necessary for a carbon-neutral policy and to build a hydrogen economy. In order to utilize biogas, impurities of biogas such as moisture, hydrogen sulfide(H2S), siloxanes, and VOCs should be removed. In particular, since H2S causes corrosiveness of equipment by sulfur oxides, and is harmful to the human body if leaked, it is a major target material to be removed. The minimum concentration of H2S obtainable from the wet method is several ppm. It is known, however that the iron hydroxide-based adsorbent in the dry method can obtain ultimately low concentration of H2S down to 0.1 ppm or less. The DeHyS was manufactured through a series of processes such as mixing iron cloride solution or iron sulfate solution, NaOH solution, and inorganic binder. During the adsorption process, H2S was removed in the form of iron sulfide through a chemical reaction, and siloxanes are known to be removed through physical adsorption. It was also applied to various biogas plant sites such as landfill gas, sewage sludge, livestock manure, and food waste. At this time, the H2S removal efficiency was known to be 99.9% or more, while simultaneous removal of 90% or more of the total siloxanes was possible. Moreover, the biogas produced at the Chungju Food Bioenergy Center was pretreated using the DeHyS and supplied to the nearby Chungju Bio Green Hydrogen Charging Station to produce hydrogen through steam methane reforming(SMR), producing 500 kg of hydrogen from 8,000 m3 of biogas per day.

Влияние сульфата железа, сернистого натрия и их смеси на флотацию сфалерита в щелочной среде

Introduction. The quality of the enrichment process is affected by many factors, ranging from the characteristics of the raw materials supplied to the enrichment plant to the enrichment technology and the agents used. Strict process control is required at all stages from mining to concentrate extraction. Copper-zinc ores of Russian deposits are difficult for enrichment due to high mass fraction of pyrite in ore and fine irregular intergrowth of sulfide minerals between themselves and with rock minerals. The practice of enrichment of copper-zinc ores has established that it is impossible to obtain high-quality zinc and pyrite concentrates without adding sphalerite flotation modifier agents to various flotation operations. To improve the flotation activity of sphalerite, copper sulphate is used as an activation additive in the enrichment process chain. Purpose of work. To study the effect of sulfhydryl collectors on flotation of sulfide minerals, and development of innovative technologies of flotation of copper-zinc and polymetallic ores considering the acidity of the environment. Materials and methods. In the experimental part of the work, several methods of materials and agents preparing were used, a variety of equipment was used, as well as methods of analysis and processing of results. The material composition and grain size distribution of sphalerite was studied using the MLA System Quanta. X-ray phase analysis of sphalerite was carried out at the University of science and technology "MISIS" in Research Laboratory of ultra-hard materials on Rigaku Geigerflex device using monochromatized CuKα-radiation. Thermographic studies were carried out using a Q -1500D derivatograph. The following flotation agents were used in the work: collector - butyl potassium xanthate, foam agent MIBC, medium regulator - lime, modifiers - iron sulfate, sodium sulphide and mixture of iron sulfate and sodium sulphide. Flotation experiments were carried out on the laboratory flotation machine FL-189 G. Results. The kinetics of sphalerite flotation is characterized not by a single value of the flotation kinetics constant for all flotation mineral grains, but by a set of such values corresponding to quite certain fractions of sphalerite extracted in the foams product. It has been found that in the initial period of flotation the mineral grains with a high value of the flotation velocity constant are flotated, and in the final period of flotation the grains of the same mineral with a low value of the same flotation velocity constant are flotated. Discussion. The introduction of iron (II) sulphate into the mineral slurry leads to a redistribution of the flocculated mineral between medium and lightly flocculated fractions. This indicates that iron (II) sulphate acts as an activator for sphalerite flotation. At a low flow rate of this agent, the proportion of medium flotable fractions increases and the proportion of easily and hardly flotable fractions decreases. With increase in the agent consumption up to 400 g/t and more, the opposite picture is observed - the proportion of medium flotable fraction decreases and the proportion of easily flotable fraction increases in flocculated sphalerite. The replacement of iron (II) sulphate by sodium sulphate has the opposite effect on the flotation spectrum of sphalerite. The introduction of a mineral suspension of a solution of sodium sulfide and iron (II) sulfate into the liquid phase at a consumption of 200 g/t of each agent leads to a decrease in the proportion of easily and especially medium floatable fractions of the mineral and an increase in the proportion of difficultly floatable fractions. Conclusions: 1. An increase in the pH of pulp liquid phase leads to a decrease in the extraction of zinc concentrate in the foam product during flotation with butyl xanthate. 2. The introduction of a solution of sodium sulfide with ferrous sulfate reduces the floatability of the mineral, which is reflected in a decrease in the extraction of zinc concentrate. 3. Sodium sulfide and iron sulphate, while simultaneously dosing them into the flotation pulp, act as depressants in the sphalerite flotation process. 4. Sodium sulfide depresses sphalerite at all studied pH concentrations. Resume. The results of the research can be useful in improving the methods for processing sulfide ores (lead-zinc and copper-zinc) which are included in the group of polymetallic ores. The developed methods of flotation processing make it possible to improve the quality of enrichment and increase the extraction of a valuable component.

Use of Citric Acid and Iron Sulfate in Promoting Post-Harvest Longevity of Cut Tulips (Tulipa Gesneriana L. Cv. Marylin) in Vase Solutions

Summary Tulip is one of the most beautiful perennial flowering plants which, based on its brilliance and attraction, is ranked at the top among cut flowers. However, bending of the neck, short display life and senescence of the flowers are the major causes that reduce its market value. These problems can be addressed by using different chemicals to prolong the flower display life. The present research was initiated to prolong the display life of tulips by using citric acid and iron sulfate (50, 100, 150 mgL−1) in distilled water containing 2.5% sucrose. Cut stems of tulips were immersed in the diluted solution of citric acid and iron sulfate. The results showed that all the observed parameters varied among the treatments. The solution containing 100 mgL−1 citric acid performed better and resulted in the most extended post-harvest display life (13.34 days), more solution uptake (63.36 mL), maximum flower diameter (57.66 mm), maximum tepal length, width, minimum stem bending and maximum quality of the flower. These characteristics were better also in 150 mgL−1 iron sulfate vase solution, but less effective in comparison. From these results, it can be concluded that the use of citric acid and iron sulfate vase solutions helps in prolonging the vase life of cut tulips and enhances the flower quality attributes.

Reserve‐adaptive potential of sperm plasma in stallions of different ages

During the aerobic metabolism of sperm, various reactive oxygen species are produced. Sperm cells are extremely vulnerable to oxidative stress (OS), which causes loss of membrane integrity, resulting in increased cell permeability, enzyme inactivation, structural DNA damage and cellular apoptosis. The aim of this study was to assess the reserve‐adaptive potential (RAP) of sperm plasma in stallions of various ages. RAP is the difference between the level of spontaneous and induced oxidative protein modification (OMP), reflecting the degree of OS. Spontaneous OMP reflects the accumulation of OS products in vivo. To determine the level of spontaneous OMP, a sperctrophotometric analysis of 2,4‐dinitrophenylhydrazones (DNPH) formed during the interaction of carbonyl derivatives of sperm plasma proteins with 2,4‐dinitrophenylhydrazine was carried out (spectrophotometer “SF‐2000”, Russia). R.L. Levine, modified by E.E. Dubinina. Measurements of DNPH derivatives were carried out at 14 wavelengths: in the range 260‐280nm for the registration of aldehyde dinitrophenylhydrazones of a neutral nature (ADNPHn), of a basic nature (ADNPHb) – 258‐264 and 428‐520nm, for the determination of ketone‐dinitrophenylhydrazones of a neutral nature (CDNPHn) 363‐370nm, basic character (CDNFGb) – 430‐434 and 524‐535nm. After that, the total amount of carbonyl derivatives was found. Induced OMP was determined in a similar way, but after adding iron (II) sulfate and hydrogen peroxide solutions to the reaction mixture. This provoked the formation of new carbonyl groups. The more RAP, the higher the ability of the biological material to resist the OS.Two groups of stallions were formed: the first group consisted of 15 stallions aged 13 to 20 years (average age 15.2±1.8 years), the second group consisted of 15 stallions aged 3 to 6 years (average age 4.0±0.5 years). The spontaneous OMP of sperm plasma in aged stallions was 495.6 Eod/ g protein, the induced one – 573.4 Eod / g protein. In the group of young stallions, spontaneous OMP – 347.2 Eod / g protein, induced – 485.3 Eod / g protein. The OMP level of sperm plasma in older stallions is initially higher than in young stallions (p = 0.04), which indicates the accumulation of carbonyl derivatives in vivo as a result of the prevalence of OS over the antioxidant capabilities of the organism. But when additional oxidizing components are added to the reaction mixture, the OMP of aged stallions does not increase as significantly as in young ones. RAP of sperm plasma of old stallions is 13.56%, of young stallions – 28.75%. The ability to withstand OS, the reserve of antioxidant capabilities of sperm plasma in young stallions is 2.1 times higher than in older stallions.

Effectiveness of European oak wood staining with iron (II) sulphate during natural weathering

Artificial graying of wood can be solution for contemporary trends of using uncoated wood for the arrangement of external architecture. The presented work was aimed at investigation of colour changes of European oak (Quercus sp.) wood surface treated with iron (II) sulphate. Three different procedures differing in time (2 h and 24 h) and temperature (20 °C and 70 °C) were used, as well as three different concentrations of aqueous iron (II) sulphate solutions (10 %, 20 %, 30 %). Beside the colour itself, it was evaluated the stained oak wood discolouration due to natural weathering. Thanks to iron (II) sulphate, wood colour changed to dark grey. In general, the colour changes on tangential section of wood were higher than those on radial section what was result of wood structure, in particular parenchyma cells arrangement in wooden rays. Contrary to expectations, the concentration of the iron (II) sulphate solution was not of significant importance for wood staining. Usage of concentrations higher than 10 % for the modification of the colour of wood gives the same effects. However, with increasing solution used to wood staining, the colour stability of the wood decreases during external exposure. The parameters of the procedure were not significantly affected. This allows the application of the simplest and least time-consuming modification method to be considered.

High retention supercapacitors using carbon nanomaterials/iron oxide/nickel-iron layered double hydroxides as electrodes

People's awareness regarding the environmental protection and energy crisis has greatly boost rapid development of advanced energy storage devices. In this regard, supercapacitors with long operation life and superior properties have considered as one of the powerful candidates for energy storage. Herein, electrodes with a 3D structure are fabricated by first mixing oyster shell powder with graphene oxide (GO) and iron sulfate solution and subsequently subjected to the hydrothermal reaction, in which GO is reduced to form reduced GO (rGO) and afterwards to fabricate rGO-FeOOH. Using dried rGO-FeOOH as the framework in the following chemical vapor deposition process, carbon nanotubes (CNTs) are successfully grew on the rGO surface. Then, NiFe layered double hydroxide (NiFeLDH) is deposited by electrochemical deposition to prepare the rGO-FeO-CNT-NiFeLDH electrodes. The rGO-FeO-CNT-700-NiFeLDH electrode performs an excellent capacitance of 411.9 F g−1 at a scan rate of 5 mV s−1. The rGO-FeO-CNT-700-NiFeLDH-60//AC-NiO asymmetric supercapacitor performs an energy density of 41.4 W h kg−1 with a power density of 5600 W kg−1. The capacitance increases up to 144.89% of its initial capacitance after operation for 3200 cycles and remains 102.2% capacitance retention after 5000 cycles demonstrating that the electrode with excellent property is applicable for energy storage devices.

Chemical Electricity

AbstractIn 1800 Alessandro Volta published the results of several years’ work on the phenomenon of electric shocks which he experienced from physical contact with the terminals of his newly developed battery. His work was prompted by Luigi Galvani's explanation of involuntary muscle spasms in frog's legs, which he induced and attributed to animal electricity. Volta's paper opened the floodgates for research in the new field of electrochemistry which has resulted in today's worldwide electric battery industry. This essay explains the sequence of natural events and their explanations which led to the publication of Volta's paper, and gives an overview of the scientific research resulting from Volta's work. This research includes attempts to improve batteries, and the development of ideas which led to a better understanding of matter and the way it interacts with energy. Practical details for the teaching of several important chemical concepts are listed in the appendix. The experiments are related to a reaction which has been known for many centuries - that between iron and copper sulphate solution.

Iron removal by fixed-bed adsorption with thermochemically treated Lithothamnium calcareum algae

Difficulty in removing metallic ions from water has led to the development of new technologies. This work aims to investigate the removal of Fe 2 + from water by a fixed-bed column filled with bioclastic granules of the algae Lithothamnium calcareum . The bioclastic granules were thermo-chemically treated in order to unblock the existent pores and improve the sorption capacity. The column was constructed in an acrylic tube with height of 14.9 cm and diameter of 4.58 cm filled with the earlier prepared Lithothamnium calcareum . Then a solution of Iron Sulfate in the concentration of 500 mg L −1 of Fe 2 + was applied in hydraulic loads of 2, 4, 6, 8 and 10 cm and the hydraulic conductivity was determined. The miscible displacement was evaluated by the construction of breakthrough curves for each load, considering the mass flux and diffusive–dispersive flux and only the diffusive–dispersive flux. Peclet number, diffusion coefficient and dispersivity of the porous medium were also determined. Evaluation of the mass balance of the bioclastic granules column experiment was performed through sigmoidal models. The column showed removal efficiency of Fe 2 + around 50% and high values of retardation factor (2.410 < R < 4.092) indicating the high interaction between Lithothamnium calcareum and the solute. The dispersive flux was predominant according to the miscible displacement and sigmoidal models evaluated. Thus, the use of Lithothamnium calcareum is an interesting alternative to remove excess of iron from consumption water, protecting from changes in color, turbidity and flavor of the water, and from pipe obstructions. • Lithothamnium calcareum used as biosorbent. • High interaction between Lithothamnium calcareum and Fe +2 . • Satisfactory removal of high concentrations of iron from water. • Predominance of dispersive flux in Lithothamnium calcareum fixed-bed column.

Thermodynamic Modeling of the Fe(II)–Fe(III)–Cu(II)–H2SO4–H2O Solution and Its Application to Determination of Redox Potential during Copper Electrorefining up to 70 °C

A thermodynamic model of the Fe(II)–Fe(III)–Cu(II)–H2SO4–H2O system is developed and shown to reliably simulate the species distribution in the industrial copper electrorefining electrolyte from 25 to 70 °C. The previously developed model of the Fe(II)–Fe(III)–H2SO4–H2O system under leaching conditions was first evaluated, and it proved that its applicability can be extended to a much higher acid concentration (185 g/L). Cu(II) species were then identified, and their thermodynamic data were collected and assessed for modeling calculations. Results reveal that after addition of a high amount of copper (40–50 g/L), Fe(II) is still distributed as free Fe2+, FeHSO4+, and FeSO4°; Fe(III) is distributed as free Fe3+, FeSO4+, FeHSO42+, and Fe(SO4)2–. Cu(II) is dissolved as Cu2+, CuSO4°, and CuHSO4+. The proposed model was validated by reliable and accurate prediction of the measured redox potential throughout all solution conditions. An expression developed previously to predict the redox potential can still be applied in this work. Analysis of speciation results strongly supports that the redox potential of acidic iron sulfate solutions with such a high acid and copper concentration can still be solely determined by the Fe3+/Fe2+ couple. The pH and effective ionic strength were also obtained and discussed. These findings contribute to further investigation on speciation of other solutions during copper production.

Hastelloy G 35 сorrosion tests for intergranular corrosion resistance

The article is devoted to the analysis of corrosion behavior and assessment of the resistance of Hastelloy G 35. Nickel-based alloys (steels) containing chromium, molybdenum, tungsten, possibly iron are widely used as materials for the manufacture of equipment in high-temperature technological processes using solutions of highly hygroscopic halides (chlorides) in molten halides (chlorides) of alkali metals. During the operation of the equipment, the instability of the surface of apparatus and pipelines to corrosion is determined. In this test, 4 samples of 80×20×3 mm were used, of which 2 samples were subjected to provoking heating, and 2 samples were examined in their normal state. Our tests were carried out in a boiling aqueous solution of iron sulfate and sulfuric acid for 48 ± 0.25 h. Further, the bent samples were examined using an MBS-9 microscope with a magnification of х8. The results of corrosion tests are also presented. As a result of the study, the rate of penetration of corrosion of the alloy was calculated. Hastelloy microstructure is presented. The average depth of destruction was determined from the six maximum values detected in six fields of view. According to the research results, the corresponding conclusions were made.

Arsenic removal from industrial effluent: In-situ ferric sulfate production and arsenic partitioning in the residues

Ferric sulfate solution was producedin situby sulfating arsenic-bearing, hematite-rich calcines (56–62% Fe2O3) with sulfuric acid, both produced by roasting refractory gold ore. The solution was then used for arsenic precipitation in the treatment of effluents from the cyanidation plant. The conversion of hematite to ferric sulfate increased as the acid/calcine ratio increased and reached 60.7%, with 0.87 of the stoichiometric acid amounts. An iron sulfate solution (13.4 g.L−1 Fe and 2.32 g.L−1 As) was produced at the end of the calcine sulfation/dissolution. Arsenic removal varied between 99.4 and 99.8%. Arsenic concentration dropped from 1583.4 mg.L−1 to 5.31 mg.L−1 As, which is far less than the industrial circuit's typical concentration (15 mg.L−1). Hydrated calcium sulfates were the principal constituents in the arsenical residues (i.e., 42–50%). Its removal allowed the identification of ferric arsenate/arsenite coprecipitates, arsenical ferrihydrite, and hydrated calcium-iron hydroxy-arsenate and hydrated calcium using X-ray diffraction analyses and Raman spectroscopy. The sequential extraction protocol and microscope automatic system confirmed the arsenic carriers. These are ferric (aluminum) or calcium arsenate/arsenites, accounting for 71.2 and 72.8% total As, and minor arsenic adsorbed on iron oxyhydroxides. Arsenic was primarily found (63.3%) in the Fe,Al-AsOx coprecipitates in the industrial residue. A 17% As-richer sludge, as achieved here (4.18% As), would result in a lower sludge volume for disposal. Transportation and disposal costs would then drop. These benefits were confirmed along one year of industrial operation. The projected reduction in effluent treatment costs reaches 60%.

Microfluidic pore model study of precipitates induced by the pore-scale mixing of an iron sulfate solution with simulated groundwater

Precipitates induced by the pore-scale mixing of iron sulfate solutions with simulated groundwater were investigated using a microfluidic pore model to assess the environmental impacts of the infiltration of acid mine drainage into a shallow aquifer. This model was employed to visualize the formation of precipitates in a porous network and to evaluate their physicochemical influences on pore flow. Four types of groundwater (Na–HCO3, Na–SO4, Na–Cl, and Ca–Cl) were evaluated, and precipitation rates were calculated by processing images of precipitates in the pores captured via microscopy. The results showed that all groundwater types formed a yellow-brownish precipitate at the interface of the iron solution and simulated groundwater flow. Microscopic X-ray analyses demonstrated that precipitate morphology varied with groundwater type. Faster precipitation was observed in the following order by groundwater type: Na–HCO3 > Na–Cl > Na–SO4 > Ca–Cl, which was attributed to the different stability constants of the major anions in each simulated groundwater with Fe ions. Chemical equilibrium models suggested that precipitates were Fe minerals, with FeOOH as the predominant form consistent with the results of X-ray photoelectron spectrometry. The presence of FeOOH implies that precipitates may serve as an effective sorption barrier against some nutrients and heavy metals for the underlying groundwater. However, dye-flow experiments suggested that the precipitates may clog aquifer pores, thereby altering hydrogeological properties in the aquifer.