Ferrous Sulfate Heptahydrate Research Articles

Study on structural characterization and algae-removing efficiency of polymeric aluminum ferric sulfate (PAFS)

Polymeric aluminum ferric sulfate (PAFS), as a novel inorganic coagulant, was prepared through direct oxidation process using industrial by-product ferrous sulfate heptahydrate (FeSO4·7H2O) and industrial aluminum oxide (Al2O3 content of 16%) as the main materials. PAFS was characterized by Fourier transformed infrared spectrophotometer, scanning electron microscopy, and X-ray diffraction. The coagulation mechanism and molecular conformation of PAFS were analyzed and the different conditions of flocculation effect were investigated in the paper. In order to test the coagulating performances of PAFS, traditional coagulants such as polymeric ferric sulfate, polymeric aluminum chloride, and polymeric aluminum ferric chloride were used to carry out the comparison tests on algae removal efficiency. The results show the removal efficiency for turbidity and chlorophyll a using PAFS were 92.8 and 95.3%, respectively, which were higher than those of the traditional coagulants.

Production of Iron Premix for the Fortification of Table Salt

Abstract The feasibility of using fluidized bed technology for the production of an iron premix of ferrous fumarate encapsulated with soy stearine for iron fortification of table salt has been successfully demonstrated. Ferrous fumarate was selected as source of iron, in preference to ferrous sulphate heptahydrate, ferric sodium EDTA and reduced elemental iron, for its bioavailability, bland taste, stability and high iron content. Potassium iodate was used as iodine source. Fluid-bed processors of 7, 200 and 500 kg capacity were used to granulate ferrous fumarate with a solution containing, hydroxypropylmethylcellulose, sodium hexametaphosphate and titanium dioxide for binding, stabilization and colour masking, respectively. Encapsulation of granulated ferrous fumarate was achieved by top-spraying hot soy stearine containing more titanium dioxide at 98ºC on the fluidized bed. The premix contained 46.4 wt. % of ferrous fumarate. Double Fortified Salt (DFS), made by dry blending 1 part of iron premix and 150 parts of already iodized salt, contained 1000 ppm of iron and 50 ppm of iodine. Less than 10% of the iron in the premix, with a bulk density of 0.78 g/cc, dissolved in HCl at pH of 4.0 indicating good coating integrity. Particle size distribution of iron premix was consistently centred on 300 µm with more than 90% of the particles in the size range of 150 to 710 µm, similar to that of free flowing refined salt.

Application of Flocculation Process in Dressing Wastewater from Antimony Mine

Antimony (Sb) has received increasing environmental concerns due to its potential toxicity and carcinogenic property. In the present work, the flocculation process had used to treat dressing wastewater (DW) from some antimony mine, and the mechanism of removing Sb was investigated. The study focused on the effect of experimental parameters on the Sb removal efficiency, such as dosage of flocculant, pH value and the settling time. Several flocculants were evaluated and the results suggested that ferrous sulfate heptahydrate (FeSO4•7H2O) was the optimal choice. When the dosage of ferrous sulfate heptahydrate (FeSO4•7H2O) was 0.075:100, pH value was 7 and the settling time was 180 min, removal efficiency of Sb in the DW reached 99.86% and concentration of Sb in the treated wastewater was below 0.04mg/L, which meets the emission standards established by State Department of Environmental Protection and State Administration for Quality Supervision and Inspection and Quarantine.

Crystallisation of ferrous sulphate heptahydrate: Experiments and modelling

AbstractCrystallisation is an industrially important unit operation for purifying and separating chemical mixtures. A generic crystallisation modelling framework has been implemented in the general process modelling system (gPROMS) software (of PSE, UK). This framework can be used to model the batch cooling crystallisation of ferrous sulphate heptahydrate (FSH). The parameter estimation and sensitivity of the predicted results with various numerical parameters was studied for batch crystalliser. An Excel “front‐end” to the gPROMS model was developed to facilitate the interactive use of the model. © 2011 Canadian Society for Chemical Engineering

Biotinylated magnetic nanoparticles for pretargeting: synthesis and characterization study.

In this paper, we have proposed a simple method to covalently conjugate biotin to magnetic nanoparticles, which can be targeted to the tumour sites by using pretargeting approach with avidin or streptavidin. Magnetic nanoparticles of manganese ferrite were synthesized by alkaline coprecipitation of ferric chloride hexahydrate, ferrous sulphate heptahydrate and manganese sulphate monohydrate using ammonium hydroxide. The synthesized magnetic nanoparticles were then successfully surface modified by using 3-aminopropyl trimethoxysilane, and the amount of aminopropylsilane bound to the surface of magnetic nanoparticles was quantified by measuring the absorbance of a purple-coloured complex (Ruhemann’s purple) formed between amine group and ninhydrin at 576 nm. The aminated magnetic nanoparticles were then conjugated to biotin by reacting them with N-hydroxysuccinimide–biotin in dimethylsulphoxide. The successful conjugation of biotin to magnetic nanoparticles was confirmed by Fourier transform infrared spectroscopy. The size, phase and magnetic nature of the synthesized nanoparticles were analysed by using various techniques like transmission electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy and vibrating sample magnetometry.

Determination of the molar extinction coefficient for the ferric reducing/antioxidant power assay

The FRAP reagent contains 2,4,6-tris(2-pyridyl)- s-triazine, which forms a blue–violet complex ion in the presence of ferrous ions. Although the FRAP (ferric reducing/antioxidant power) assay is popular and has been in use for many years, the correct molar extinction coefficient of this complex ion under FRAP assay conditions has never been published, casting doubt on the validity of previous calibrations. A previously reported value of 19,800 is an underestimate. We determined that the molar extinction coefficient was 21,140. The value of the molar extinction coefficient was also shown to depend on the type of assay and was found to be 22,230 under iron assay conditions, in good agreement with published data. Redox titration indicated that the ferrous sulfate heptahydrate calibrator recommended by Benzie and Strain, the FRAP assay inventors, is prone to efflorescence and, therefore, is unreliable. Ferrous ammonium sulfate hexahydrate in dilute sulfuric acid was a more stable alternative. Few authors publish their calibration data, and this makes comparative analyses impossible. A critical examination of the limited number of examples of calibration data in the published literature reveals only that Benzie and Strain obtained a satisfactory calibration using their method.

Biohydrometallurgical/UV production of ferrous sulphate heptahydrate crystals from pyrite present in coal tailings

The objective of this work was to develop a biohydrometallurgical/UV radiation route to produce ferrous sulphate heptahydrate (melanterite) from the pyrite present in coal tailings. The experimental work was carried out with a pyrite concentrate obtained from gravimetric processing of coal tailing. At laboratory scale it was performed the oxidation of pyrite in an aqueous medium in packed bed leaching columns in an oxidising environment with the presence of acidophilic bacteria ( Acidithiobacillus ferrooxidans). The recirculation of the liquor allowed obtaining an iron-rich extract. The conversion of Fe 3+ to Fe 2+ was performed using ultraviolet irradiation (UV). Finally, the solution was evaporated allowing the formation of iron sulphate crystals. The results demonstrated that it is possible to produce high purity ferrous sulphate heptahydrate crystals using coal tailings as raw material.

Gallium and Arsenic Recovery from Waste Gallium Arsenide by Wet Refined Methods

This study was focused on the recovery of gallium arsenide (GaAs) from semiconductor fabrication sludge. Wet refined methods were applied to recover gallium (Ga) including acid leaching, purified isolation, electrolysis, and coagulation. The result showed that leaching Ga with nitric acid (HNO3) was more efficient than with sulfuric acid (H2SO4). GaAs could be leached with 4 N HNO3 to obtain 100% Ga+ and arsenic (As—). The pH was adjusted with sodium hydroxide (NaOH). Then, the solution was extracted by di(2-ethylhexyl) phosphoric acid (D2EHPA) and was back extracted by H2SO4. In this way, Ga extraction efficiency was 80%. At the end of the process, electrolysis was applied to recover Ga. The resulting electrolysis efficiency with nickel-copper was only 56% and its purity was 92%. To further increase the recovery of Ga, the leaching solution was adjusted to alkaline solution and was then electrolyzed with platinum-stainless steel. In this way, recovery and purity could be as high as 90% and 94%, respectively. The removal of arsenic was 86% when the leaching solution was added with ferrous sulfate heptahydrate (Fe2(SO4)3‧xH2O) to form iron arsenate (AsFeO4).

Weekly Iron Supplementation for the Prevention of Anemia in Pre-school Children: A Randomized, Double-blind, Placebo-controlled Trial

This study analyses the impact of weekly iron supplementation with ferrous sulphate heptahydrate (FeSO4) in 5-year-olds compared with placebo, on hemoglobin (Hb) and hematocrit (Ht) values and anemia. The study concerns a cluster-randomized, placebo-controlled double-blind trial. Intervention participants received 50 mg elemental iron for 14 weeks. The study population comprised pre-school children (n = 135) from one randomly chosen public school in the northeast of Brazil. Participants were 5-year-old students from a public school. Mean Hb and Ht values increased after iron supplementation, with p < 0.0001. There was no statistically significant increase in the placebo group. After intervention, anemia prevalence reduced only in the intervention group, from 48.0% to 26.0%. Weekly iron supplementation was effective in reducing anemia in 5-year-olds.

Iron removal and recovery in the titanium dioxide feedstock and pigment industries

Titanium and iron are closely related in nature. Therefore, for both environmental and economic reasons, the fate of iron may be very crucial for the titanium extraction industry. Smelting of ilmenite to produce titania slag allows for the recovery of iron as high purity pig iron. However, in the production of synthetic rutile from ilmenite sands, iron is returned to the mine site as a fine oxide/hydroxide residue. Some projects to recover iron from these residues never reached the industrial scale. In the titanium dioxide (TiO2) pigment industry, iron is deported as sulfate or chloride salt, which is usually neutralized and rejected at a considerable cost. In the past few years, ferrous sulfate heptahydrate (or copperas) and iron chloride have found a few applications, but still the demand for these iron salts is not enough to cover the production volumes. The review of some new processes currently under development clearly shows that iron recovery is essential for the long-term viability of any new ilmenite upgrading or TiO2 pigment production process.

Reduction of Cr(VI) to Cr(III) in Artificial, Contaminated Soil Using Ferrous Sulfate Heptahydrate and Sodium Thiosulfate

Due to widespread use in industrial applications, chromium compounds are often considered one of the most serious heavy metal pollutants found at environmental sites. Stabilization/solidification has been studied as a means of immobilizing chromium within a solid matrix. Reduction to a lower valence state is an effective treatment option when coupled with a stabilization/solidification treatment, so that any chromium subsequently leached from the treated soil into groundwater is the less toxic and less mobile trivalent form of chromium. Some studies also indicate that reduction from Cr(VI) to Cr(III) is a necessary preliminary step to effective immobilization. Recent studies have reported the use of ferrous sulfate heptahydrate as an effective reducing agent. However, the possibility of chromium release after such treatment has also been called into question. This technical note presents an alternative to ferrous sulfate heptahydrate, the less-expensive sodium thiosulfate, to reduce hexavalent-chromium co...

Synthesis of Water-Soluble Iron−Gold Alloy Nanoparticles

In this study, a synthetic method to produce water-soluble iron−gold (Fe−Au) alloy nanoparticles is described. The diameter of the alloy nanoparticles is 4.9 ± 1.0 and 3.8 ± 1.0 nm for two different precursors of iron, ferrous sulfate heptahydrate (Fe2+) and iron pentacarbonyl (Fe0). The X-ray powder diffraction of the alloyed nanoparticles shows an appreciable shift in 2θ peak positions relative to pure gold or iron. Using Vegard’s law, we estimated the particle’s iron content to be 14.8 ± 4.7 mol %. The lattice constant of the alloy nanoparticles is found to be 4.0449 ± 0.0375 A. The high-resolution transmission electron microscopy images show the presence of icosahedral structures in agreement with the previous high temperature synthesis of the Fe−Au alloy nanoparticles. The optical absorption of the alloy nanoparticles is distinctive from pure gold nanoparticles and shows a relatively narrow absorption band in the range of 642−662 nm depending upon the amount of gold precursor used.

Removal of nuisance aqueous anions with Ferrilig

The present study describes an improved synthesis of Ferrilig, an iron(III) salt of a commercially available immobilized ligand, IMLIG, called Octolig®. The resulting composite, called “Ferrilig” was used to remove arsenate, chromate, molybdate, and selenite ions from aqueous solutions by means of column chromatography. The synthesis of Ferrilig was accomplished by treating an aqueous suspension of Octolig®-21 with an equal weight of ferrous sulfate heptahydrate under nitrogen. The ferrous salt was then collected by sieving and allowed to oxidize to the iron (III) salt by exposure to air; treatment with dilute sodium hydroxide converted the composite to the hydroxide. Using 300 ppb As (as Na2HAsO4·7H2O) and column chromatography, the arsenic concentration in the effluent was less than the detection limit (< 2 ppb). Chromium as sodium chromate, molybdenum as (NH4)6 Mo7O24·4H2O, and selenium as Na2Se03, were removed with fair success. The elements, their initial concentrations and their percentage removal (parenthetically) were: As (280 ppb, 99%), Cr (50.6 ppm, 95.5%), Mo (50.7 ppm, 94.6%), Se (258 ppm, 99.9%).

Studies on the behavior of Co 2+ and Zn 2+ in the conversion from FeOOH to magnetite in NH 3 (NaOH)–Fe 2+, Co 2+–H 2O medium under hydrothermal conditions

Crystalline FeOOH and Zn(II) doped FeOOH samples were prepared by a co-precipitation method using ferrous sulphate heptahydrate, zinc sulphate heptahydrate, ammonia, 3% hydrogen peroxide at 80 °C and pH value 3.0. These samples were characterized by XRD and were also chemically analyzed. The XRD patterns of pure FeOOH matched with that of Zn(II) doped FeOOH sample and showed no shift in their d-values, which indicated that Zn 2+ ions were adsorbed on the surface of FeOOH or on the surface of the crystalline lattice, and were not captured into the ferrite lattice. Chemical analysis showed that the molar ratio of Zn(II)/Fe in Zn(II) doped FeOOH sample was only 0.038 when this ratio was 0.5 in an initial reaction solution. These samples were treated in ammoniacal or sodium hydroxide medium in the presence of ferrous sulphate or cobalt sulphate under hydrothermal conditions. The converted products were analyzed both for ferrous, total iron, cobalt and zinc. Characterization was carried out using instrumental techniques such as SEM, FT-IR, XRD and magnetization characterization. Though the XRD patterns of the converted products showed presence of only magnetite in the NH 3–Fe 2+, Co 2+–H 2O converted medium, the FT-IR spectra and chemical analysis showed an un-reacted FeOOH in the converted product. Even though, the saturation magnetization of this magnetite was higher to 97.489 emu g − 1 . Furthermore, higher temperature increased the concentration of Co 2+ captured into spinel structure. The conversion were restrained in NH 3 concentration of less than 12 g/L and more than 25 g/L. However, increasing of Fe 2+/Co 2+ ratio in the NH 3–Fe 2+, Co 2+–H 2O medium made no distinct difference in the introduction of Co 2+ into spinel structure when concentration of Fe 2+ was enough. Compared with Zn-free FeOOH, it was difficult for Zn-doped FeOOH to convert to magnetite in the NH 3 (NaOH)–Fe 2+–H 2O medium. Furthermore, alkali species were critical in the above conversion. The content of Zn 2+ which was out of Zn-doped FeOOH solid state and entered into the outer solution was more in the NH 3 medium than that of the NaOH medium, but conversion from Zn–FeOOH into magnetite was easy in the NaOH medium. The explanations of above facts were given in the text.

Removal of aqueous arsenic using iron attached to immobilized ligands (IMLIGs)

The present study describes the synthesis of the iron(III) salt of a commercially available immobilized ligand, IMLIG, Octolig-21 and its use to remove arsenic from aqueous solutions. The synthesis was accomplished by treating an aqueous suspension of Octolig-21 with an equal weight of ferrous sulfate heptahydrate under nitrogen. The ferrous salt was then collected by sieving and allowed to oxidize to the iron (III) salt by exposure to air, and treatment with dilute sodium hydroxide converted the composite to the hydroxide. Using standard test water containing 300 ppb As and column chromatography, reduction of the arsenic concentration to 3 ppb or less in the effluent was achieved, using a pair of columns (4.5 cm id; 1780 mL and 2019 mL, respectively) in tandem. Subsequently, the Fe(III)-Octolig composite was tested for capacity, and it was calculated that with an input of 50 ppb As, it could take up to a year for the effectiveness to be exhausted.

Modified atmosphere and humidity packages for conservation of paper antiques

Modified atmosphere and humidity (MAH) agents were developed to manipulate the gas composition and humidity for controlling the foxing of paper materials during storage. Sodium ascorbate, sodium carbonate decahydrate, ferrous sulfate heptahydrate, and silica gel were selected as the basic ingredients to formulate the MAH agents that could effectively remove oxygen, release carbon dioxide, and control the relative humidity (RH). With all the MAH agents developed in our study, RH was reduced and maintained without decreasing the MAH efficiency. To evaluate the inhibition of microorganisms on antique paper by MAH agents, the properties of Wikstroemia papers were measured after accelerated aging and inoculation with Aspergillus flavus and Penicillium citrinum. Under high (90%) or low (50%) RH conditions, as long as MAH agents were used, even after 80 days, the color difference value of Wikstroemia paper was kept below 1.5 and foxing was not found. Paper packaged without MAH agents and under RH as high as 90% showed a substantial color difference in 60 days. Snowflake-like foxing was also found by ultraviolet light inspection. Wikstroemia paper inoculated with P. citrinum without an MAH agent showed a significant color difference in 80 days.

Long-term treatment issues with chromite ore processing residue (COPR): Cr 6+ reduction and heave

A pugmill treatability study was conducted to remediate chromite ore processing residue (COPR) using ferrous sulfate heptahydrate (FeSO 4·7H 2O) as a reductant. Two different types of COPR, with respect to particle size and mineralogy, were tested in this study. Two different stoichiometric ratios of FeSO 4·7H 2O to Cr 6+ (5× and 8×) were applied to reduce Cr 6+ to Cr 3+. The effectiveness of FeSO 4·7H 2O treatment was assessed using the toxicity characteristic leaching procedure (TCLP) tests and X-ray absorption near edge structure (XANES) analyses. TCLP results obtained from the pugmill treatability study showed that TCLP Cr concentrations were less than the TCLP regulatory limit of 5 mg/L upon 8× FeSO 4·7H 2O treatment for up to 420 days but may fail to meet this regulatory limit in the long-term. XANES results obtained from samples cured for 300 days showed that all of the treated samples failed the New Jersey Department of Environmental Protection (NJDEP) clean up level for Cr 6+ of 240 mg/kg. However, the Cr 6+ concentration from the sample with the smaller particle size approached 240 mg/kg (338 mg/kg), suggesting that particle size reduction prior to the addition of reductant may improve the effectiveness of the treatment. COPR heaving was investigated with unconfined swell tests upon 5× and 8× FeSO 4·7H 2O treatment. The formation of ettringite, an expansive material, was investigated following the swell tests using X-ray powder diffraction (XRPD). Significant heaving (>50 vol%) was observed at curing times of 138 days for the 5× treatment and the ettringite formation was identified by XRPD analyses.

Ettringite-Induced Heave in Chromite Ore Processing Residue (COPR) upon Ferrous Sulfate Treatment

A pilot-scale treatment study was implemented at a deposition site of chromite ore processing residue (COPR) in New Jersey. Ferrous sulfate heptahydrate (FeSO4 x 7H2O) was employed to reduce hexavalent chromium in two dosages with three types of soil mixing equipment. XANES analyses of treated samples cured for 240 days indicated that all treatment combinations failed to meet the Cr(VI) regulatory limit of 240 mg/kg. More importantly, the discrepancy between XANES and alkaline digestion results renders the latter unreliable for regulatory purposes when applied to ferrous-treated COPR. Regardless of Cr-(VI), the introduction of reductant containing sulfate, mechanical mixing, water, acidity, and the resulting temperature increase in treated COPR promoted dissolution of brownmillerite (Ca2FeAlO5), releasing alumina and alkalinity. The pH increase caused initially precipitated gypsum (CaSO4 x 2H2O) to progressively convert to ettringite (Ca6Al2(SO4)3 x 32H2O) and its associated volume expansion under both in situ and ex situ conditions, with a maximum of 0.8 m vertical swell within 40 days of curing. While Cr-(VI) treatment remains a challenge, the intentional exhaustion of the heave potential of COPR by transforming all Al sources to ettringite emerges as a possible solution to delayed ettringite formation, which would hamper site redevelopment.

Pilot‐Plant Study of Wastewater Sludge Decontamination Using a Ferrous Sulfate Bioleaching Process

The objective of this research was to investigate the performance of the ferrous sulfate bioleaching (FSBL) process in a pilot plant for decontamination and stabilization of wastewater sludge. Batch and continuous experiments, conducted with two 4-m3 bioreactors using indigenous iron-oxidizing bacteria (20% v/v of inoculum) with addition of 4.0 g ferrous sulfate heptahydrate per liter of sludge initially acidified to pH 4.0, were sufficient for effective heavy metal (cadmium, copper, manganese, zinc, and lead) removal yields. The average metal removal yields during the FSBL process were as follows: cadmium (69 to 75%), copper (68 to 70%), manganese (72 to 73%), zinc (65 to 66%), and lead (16%). The FSBL process was also found to be effective in removing both fecal and total coliforms (abatement > 5 to 6 log units). The nutrients content (nitrogen, phosphorus, and magnesium) were also preserved in decontaminated sludge.

Iron Form and Concentration Affect Nutrition of Container-grown Pelargonium and Calibrachoa

Two experiments were completed to determine whether the form and concentration of iron (Fe) affected Fe toxicity in the Fe-efficient species Pelargonium ×hortorum `Ringo Deep Scarlet' L.H. Bail. grown at a horticulturally low substrate pH of 4.1 to 4.9 or Fe deficiency in the Fe-inefficient species Calibrachoa ×hybrida `Trailing White' Cerv. grown at a horticulturally high substrate pH of 6.3 to 6.9. Ferric ethylenediaminedi(o-hydroxyphenylacetic) acid (Fe-EDDHA), ferric ethylenediamine tetraacetic acid (Fe-EDTA), and ferrous sulfate heptahydrate (FeSO4·7H2O) were applied at 0.0, 0.5, 1.0, 2.0, or 4.0 mg ·L–1 Fe in the nutrient solution. Pelargonium showed micronutrient toxicity symptoms with all treatments, including the zero Fe control. Contaminant sources of Fe and Mn were found in the peat/perlite medium, fungicide, and lime, which probably contributed to widespread toxicity in Pelargonium. Calibrachoa receiving 0 mg Fe/L exhibited severe Fe deficiency symptoms. Calibrachoa grown with Fe-EDDHA resulted in vigorous growth and dark green foliage, with no difference from 1 to 4 mg·L–1 Fe. Using Fe-EDTA, 4 mg Fe/L was required for acceptable growth of Calibrachoa, and all plants grown with FeSO4 were stunted and chlorotic. Use of Fe-EDDHA in water-soluble fertilizer may increase the upper acceptable limit for media pH in Fe-inefficient species. However, iron and Mn present as contaminants in peat, irrigation water, or other sources can be highly soluble at low pH. Therefore, it is important to maintain a pH above 6 for Fe-efficient species regardless of applied Fe form or concentration, in order to avoid the potential for micronutrient toxicity.