Ferric Salt Solutions Research Articles

Unveiling the formation mechanism of polydisperse iron oxide nanoparticles in coprecipitation route

Coprecipitation is the simplest, fastest, and most inexpensive method for preparing metal oxide nanoparticles (NPs). It is considered one of the most convenient methods for simultaneously precipitating two or more aqueous metal salt precursors (such as chlorides, nitrates, oxychloride, etc.) into NPs in a basic solvent, yielding uniform composition. However, the main drawback of this route is the production of NPs with a broad size distribution (polydispersed particle formation), which limits their use in various applications. The present work addresses the experiments and formation mechanism of polydispersed iron oxide magnetite (Fe3O4) NPs using this route. Experiments involving the drop-wise addition of mixed ferric (Fe3+) and ferrous (Fe2+) chloride salt solutions to NaOH base solution at room temperature resulted in a polydispersed Fe3O4 NP system containing both large and small particles at the end of 30 min of the reaction. A mechanism is proposed to explain the formation of these polydispersed Fe3O4 NPs based on the time scales of different individual particle formation events and the experimental aging time. The mechanism elucidates that the time scales of events such as Fe3O4 nucleation, diffusional-limited and Ostwald ripening growth of small and large particles, and the coagulation of two small particles or a small particle with a large particle are smaller, and completed within the experimentally allowed aging time. Conversely, the coagulation time for two large particles exceeds the experimental time, preventing complete coagulation. As a result, incomplete coagulation of large particles and the completion of all other events lead to the formation of a polydispersed Fe3O4 NP system at the end of the synthesis. The combined experiments and time scale-based mechanism explain the polydispersed NP formation in the coprecipitation route, and the insights gained from this understanding can be beneficial for optimizing synthesis conditions to achieve a controlled size distribution of Fe3O4 and other NP systems.

Photocatalytic removal of 2-chlorophenol from water by using waste eggshell-derived calcium ferrite.

A new approach to recycling low-value eggshell food waste was to produce a CaFe2O4 semiconductor with a narrow band gap (Eg = 2.81 eV) via hydrothermal treatments of powdered eggshell suspended in aqueous ferric salt (Fe3+) solutions at varying Fe loadings. It was possible to obtain a single phase of CaFe2O4 without any Ca(OH)2 and CaO impurities using an optimal Fe loading (30 wt% of Fe3+ by eggshell weight). The CaFe2O4 material was used as a photocatalyst for the breakdown of 2-chlorophenol (2-CP, a herbicide model chemical) as a pollutant in water. The CaFe2O4 with a Fe loading of 7.1 wt% exhibited a high 2-CP removal efficiency of 86.1% after 180 min of UV-visible light irradiation. Additionally, the eggshell-derived CaFe2O4 photocatalyst can be effectively reused, giving a high removal efficiency of 70.5% after the third cycle, without the requirement of regeneration processes (washing or re-calcination). Although radical trapping experiments confirmed that hydroxyl radicals were generated in the photocatalytic reactions, photogenerated holes play a significant role in the high 2-CP degradation efficiencies. The performance of the bioderived CaFe2O4 photocatalysts in the removal of pesticides from water demonstrated the benefits of resource recycling in the area of materials science and in environmental remediation and protection.

Use of ferric salt solutions as leaching agents of Co, Ni, Cu, Fe, and Mn from metallic alloys of spent lithium-ion batteries and separation of iron from the leaching solution

Smelting reduction of spent lithium-ion batteries (LIBs) results in metallic alloys containing Co, Ni, Cu, Fe, and Mn. In order to recover the valuable metals contained in the metallic alloys, they need to be dissolved. In this work, the mixture of Fe2(SO4)3 and FeSO4, single Fe2(SO4) and FeCl3 solutions were used as leaching agents and the effects of parameters such as ferric salt concentration, reaction temperature and time, and pulp density on the leaching of the metals were studied. The difference in the leaching percentage of the metals due to the type of the ferric solutions was insignificant. In these leaching systems, ferric and hydrogen ions act as oxidants and sulfate/bisulfate and chloride anions act as ligands. Optimal conditions for the complete leaching of metals by single ferric solutions were 0.35 mol/L Fe2(SO4)3 or 0.7 mol/L FeCl3 at 12.5 g/L pulp density for 60 min at 22oC. The addition of H2O2 to the leaching solution for the oxidation of Fe(II) to Fe(III) enhanced the selective extraction of iron over Co(II), Ni(II), Cu(II), Mn(II), and Si(IV) by D2EHPA. Stripping of iron from the loaded D2EHPA with aqua regia resulted in a pure iron solution. Compared to HCl and H2SO4 solutions, the use of single ferric solution showed some advantages such as fast reaction kinetics at 22?C and the reduction in the dosage of acids and oxidants.

Lithium extraction from clay-type lithium resource using ferric sulfate solutions via an ion-exchange leaching process

Clay-type lithium resources have been developed as an important natural lithium source secondary to hard rock sources and brine sources. In this study, a green and effective lithium extraction process employing ferric salt solutions to leach lithium-rich clay was proposed. Upon calcination treatment, 73.6% of lithium could be leached over a period of 180 min using a 15% ferric sulfate solution at 90 °C. The most suitable calcination temperature, leaching temperature, ferric sulfate concentration, and reaction time were determined to be 600 °C, 90 °C, 15% ferric sulfate, and 180 min, respectively. Ferric chloride and ferric nitrate had similar lithium leaching efficiencies under the same conditions. In addition, ferrous, sodium and calcium salts were introduced and compared in terms of their lithium extraction abilities. The results indicated that ferric ions had good selectivity for lithium leaching. The leaching process was considered to involve ion exchange between ferric ions and lithium ions.

High Yield Synthesis and Application of Magnetite Nanoparticles (Fe3O4)

Magnetite nanoparticles (Fe3O4), average particle size of 12.9 nm, were synthesized de novo from ferrous and ferric iron salt solutions (total iron salt concentration of 3.8 mM) using steady-state headspace NH3(g), 3.3% v/v, at room temperature and pressure, without mechanical agitation, resulting in >99.9% yield. Nanoparticles size distributions were based on enumeration of TEM images and chemical compositions analyzed by: XRD, EDXRF, and FT-IR; super-paramagnetic properties were analyzed by magnetization saturation (74 emu/g). Studies included varying headspace [NH3(g)] (1.6, 3.3, 8.4% v/v), and total iron concentrations (1.0 mM, 3.8 mM, 10.0 mM, and >>10 mM). An application of the unmodified synthesized magnetite nanoparticles included analyses of tetracycline’s (50, 100, 200, 300, and 400 ppb) in aqueous, which was compared to the same tetracycline concentrations prepared in aqueous synthesis suspension with >97% extraction, analyzed with LC-MS/MS.

Magnetic hyperthermia in phosphate coated iron oxide nanofluids

We study the magnetic field induced hyperthermia in water based phosphate coated Fe3O4 nanofluids, synthesized by a co-precipitation method using ferrous and ferric salt solutions, ammonia and orthophosphoric acid. The specific absorption rate (SAR) values were measured at a fixed frequency of 126kHz and at extremely low field amplitudes. The SAR values were determined from the initial rate of temperature rise curves under non-adiabatic conditions. It was observed that the SAR initially increases with sample concentration, attains a maximum at an optimum concentration and beyond which SAR decreases. The decrease in SAR values beyond the optimum concentration was attributed to the enhancement of dipolar interaction and agglomeration of the particles. The system independent intrinsic loss power (ILP) values, obtained by normalizing the SAR values with respect to field amplitude and frequency, were found to vary between 158–125nHm2kg−1, which were the highest benchmark values reported in the biologically safe experimental limit of 1.03–0.92×108Am−1s−1. The very high value of ILP observed in the bio-compatible phosphate coated iron oxide nanofluids may find practical applications for these nanoparticles in tumor targeted hyperthermia treatment.

Adsorptive Removal of As(III) from Aqueous Solution

The iron-modified Dalbergia sissoo sawdust was synthesized by loading iron (III) onto phosphorylated Dalbergia sissoo sawdust via soaking in a ferric salt solution. Batch studies were performed at an initial concentration of 1 mg/l to evaluate the effect of parameters such as pH, equilibrium time, adsorbent dose and concentration of adsorbate. Kinetics and isotherm modeling studies demonstrated that the experimental data best fit a pseudo-first order and Langmuir isotherm model, respectively. The maximum adsorption capacity was found to be 1.33 mg/g for As(III) onto FePDSD suggesting the suitability of chemically modified Dalbergia sissoo sawdust for the adsorptive removal of As(III) from aqueous solution.Journal of Institute of Science and Technology, 2014, 19(1): 150-154

A Single Pot Approach for Synthesis of Phosphate Coated Iron Oxide Nanoparticles.

Water dispersible Fe3O4 nanoparticles with a phosphate monolayer capping was synthesized by a single-step coprecipitation method using ferrous and ferric salt solutions, ammonia and orthophosphoric acid. The synthesized nanoparticles were characterized using thermogravimetric analyser with simultaneous differential scanning calorimetry (TGA-DSC), Fourier transform infra red spectroscopy (FTIR), X-ray diffraction (XRD), small angle X-ray scattering (SAXS), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and dynamic light scattering (DLS). The FTIR result confirms the formation of protonated and nonprotonated monodentate complexes on nanoparticle surface. The surface coverage and the bridging of these complexes are found to be pH dependant. The DSC results confirm that the maghemite to hematite phase transition in these nanoparticles is enhanced by ~100 °C, which is attributed to the presence of flame retardant phosphocarbonaceous shell at the nanoparticle interface. These results show that the dynamic capping of phosphate on Fe3O4 particles during co-precipitation can control the nucleated particle size, without compromising magnetic properties and improve their thermal stability. The phosphate capped Fe3O4 nanoparticles showed excellent long term stability (> 2 years of shelf life) at biological pH that makes them ideal for biomedical applications.

Development of the Hydroxysulfate Green Rust on the Steel Surface Contacting with Water Ferric and Ferrous Salt Solutions

Development of the Hydroxysulfate Green Rust on the Steel Surface Contacting with Water Ferric and Ferrous Salt Solutions

Preparation of Activated Carbon Loaded with Ferric Oxide Hydrate and its Absorption for Arsenic

In this study granular activated carbon loaded with ferric oxide hydrate (Fe-AC) as arsenic adsorbent was prepared by impregnation method. The influence of the kinds of ferric salt solution, the concentration of ferric salt solution, impregnation time and curing temperature on its arsenic removal effect was investigated. The optimal preparation conditions of the adsorbent were determined. And its adsorption properties of arsenic in aqueous solution were studied by static adsorption experiments. Results showed that when the dipping solution is 1.0 mol/L of Fe (NO3)3, impregnation time is 16h and the curing temperature is 60°C, the arsenic adsorption effect of the prepared adsorbent is best. The pattern of adsorption of As (V) with Fe-AC prepared under optimal condition well fit the Langmuir adsorption model, the correlation coefficient R2is greater than 0.98, and the maximum adsorption capacity is up to 71.43 mg/g.

Stable aqueous dispersion of superparamagnetic iron oxide nanoparticles protected by charged chitosan derivatives

This article presents the synthesis and characterization of biocompatible superparamagnetic iron oxide nanoparticles (SPIONs) coated with ultrathin layer of anionic derivative of chitosan. The water-based fabrication involved a two-step procedure. In the first step, the nanoparticles were obtained by co-precipitation of ferrous and ferric aqueous salt solutions with ammonia in the presence of cationic derivative of chitosan. In the second step, such prepared materials were subjected to adsorption of oppositely charged chitosan derivative which resulted in the preparation of negatively charged SPIONs. They were found to develop highly stable dispersion in water. The core size of the nanocoated SPIONs, determined using transmission electron microscopy, was measured to be slightly above 10 nm. The coated nanoparticles form aggregates with majority of them having hydrodynamic diameter below 100 nm, as measured by dynamic light scattering. Their composition and properties were studied using FTIR and thermogravimetric analyses. They exhibit magnetic properties typical for superparamagnetic material with a high saturation magnetization value of 123 ± 12 emu g−1 Fe. Very high value of the measured r 2 relaxivity, 369 ± 3 mM−1 s−1, is conducive for the potential application of the obtained SPIONs as promising contrast agents in magnetic resonance imaging.Electronic supplementary materialThe online version of this article (doi:10.1007/s11051-012-1372-9) contains supplementary material, which is available to authorized users.

Design, characterization and magnetic properties of Fe3O4-nanoparticle arrays coated with PEGylated-dendrimers

Stable magnetic magnetite nanoparticles (Fe3O4 NPs) were synthesized using the chemical co-precipitation method of ferrous (Fe2+)/ferric (Fe3+) mixed aqueous salt solutions in presence of well-defined biocompatible low generation (poly)amidoamine (PAMAM)-based dendrimers with end-grafted n ethylene glycol ether (n=1, 2, 9) moieties, accessible by means of straightforward consecutive divergent synthesis methodologies including addition and amidation cycles. Addition of NH4OH to the respective dendritic nanoreagent containing iron salt solution produced dendritic stabilized uniform shaped magnetite nanoparticles. The structural and magnetic properties of Fe3O4 NPs were analyzed by FT-IR spectroscopy, thermogravimetry (TG), X-ray powder diffraction (XRPD), transmission electron microscopy (TEM), and superconducting quantum interference device (SQUID) vibrating sample magnetometry (VSM). The coherence of affecting the average magnetite particle diameter in range of 5.6 (±1.4)–10.1 (±1.9)nm by the dendritic scaffold, the number and length of the attached ethylene glycol ether termini, as well as the adjusted stabilizer-to-Fe3O4 ratio is discussed along with their magnetic peculiarities.

Arsenic Removal from Water by Iron-Modified Bamboo Charcoal

The effectiveness of a novel and low-cost adsorbent, iron-modified bamboo charcoal (BC-Fe), for arsenic removal from aqueous systems was evaluated in this study. The BC-Fe was synthesized by loading iron onto bamboo charcoal via soaking in a ferric salt solution. The BC-Fe possessed a porous structure with a surface area of 277.895 m2/g. The adsorption characteristics of arsenic onto BC-Fe were further investigated at various pHs, contact times, arsenic concentrations, and adsorbent doses in batch tests. The corresponding optimum equilibrium pH ranges for As(III) and As(V) removal were 4–5 and 3–4, respectively. The equilibrium times for As(III) and As(V) adsorption were 30 and 35.5 h, respectively. The arsenic removal was strongly dependent on the initial adsorbate concentration and adsorbent dosage. The maximum arsenic removal capacities of BC-Fe under the experimental conditions were 7.237 and 19.771 mg/g for As(III) and As(V), respectively. The pseudo-second-order kinetic model and Freundlich isotherm explained the kinetic and equilibrium of both the As(III) and As(V) adsorbent processes, respectively. Based on these results, the BC-Fe developed in this study is a promising material for the treatment of arsenic-contaminated water.

Mechanistic Study on Magnetite Nanoparticle Formation by Thermal Decomposition and Coprecipitation Routes

The synthesis of poly (acrylic acid) [PAA]-coated superparamagnetic Fe3O4 nanoparticles was carried out in two ways, either by thermal decomposition of an organometallic iron precursor or by coprecipitation of aqueous solutions of ferrous and ferric chloride salts. PAA-coated particles obtained in the former route were spherical, isolated, and nearly monodisperse, whereas aggregates of coated particles formed in the latter route. A nanoparticle formation mechanism is proposed to explain such contrasting morphology. It is based on estimated time scales of different individual steps in the synthesis routes, diffusion of Fe3O4 nanoparticle over a PAA polymer chain, Brownian collision, and coagulation of particles and experimental aging time. We find that the coagulation time scale is smaller in the thermal decomposition route and is hence essentially complete within the experimental aging time. This results in formation of PAA-coated, isolated Fe3O4 nanoparticles. In contrast, the coagulation time scale in c...

Effect of Receiver pH on Infinite Dose Diffusion of 55FeCl3 across the Sweet Cherry Fruit Exocarp

Recent studies established that some ferric salts, including FeCl3, decrease water permeability of the sweet cherry (Prunus avium L.) fruit exocarp and fruit cracking, presumably by a pH-dependent precipitation reaction that blocks high-flux pathways across the fruit surface. The objectives of our study were the following: to establish the effect of receiver pH on penetration of 55FeCl3 through excised exocarp segments (ES) and isolated cuticular membranes (CM) and to localize any Fe precipitates in the epidermal system of mature sweet cherry fruit. Penetration was studied using an infinite dose diffusion system where 55Fe penetrated from donor solutions of ferric salts (10 mm, pH 2.2–2.6) or EDTA-Na-Fe(III) (10 mm, pH 5.0) across an interfacing ES or CM into aqueous receiver solutions of pH values ranging from 2.0 to 6.0. For receiver pH 2.0, 55Fe penetration of the ES from a 10 mm FeCl3 donor (pH 2.6) was linear with time, but for receiver pH ≥ 3.0, penetration was low and insignificant. Increasing the pH of the water receiver from 2.0 to 6.0 in the course of an experiment resulted in an immediate halt of penetration regardless of whether 55Fe penetration occurred from FeCl3 (pH 2.6), Fe(NO3)3 (pH 2.6), or Fe2(SO4)3 (pH 2.4) as donor solutions (all at 10 mm). Only from EDTA-Na-Fe(III) (pH 5.0) 55Fe penetration continued to occur albeit at a decreased rate (−30%). At receiver pH 2.0, the 55FeCl3 flux through stomatous ‘Sam’ ES averaged 10.4 ± 2.3 pmol·m−2·s−1 and was positively correlated to stomatal density. Conventional and analytical electron microscopy (energy dispersive X-ray analysis, electron spectroscopic imaging, and electron energy loss spectroscopy) identified ferric precipitates in periclinal and anticlinal cell walls of epidermal cells underlying the cuticle, but not within the cuticle. These data indicate that the lack of 55Fe penetration from donor solutions of ferric salts through the ES into a receiver solution at pH ≥ 3 and the previously reported decrease in water uptake and cracking as a response to immersing fruit in solutions of ferric salts are the result of a precipitation reaction at the cuticle/cell wall interface in the sweet cherry exocarp. Although spray application of ferric salts is prohibitive for ecotoxicological reasons, understanding their mechanism in decreasing water uptake and fruit cracking may be helpful in the search for alternate compounds that are effective and ecotoxicologically acceptable.

Characterization of hydrolyzed Fe(III) species produced in Fenton’s reaction

In this paper, the applicability of the ferron assay for the characterization of hydrolyzed Fe(III) produced in the Fenton’s reaction system was investigated, and then the hydrolysis process of Fe(III) under typical Fenton’s reaction conditions was compared with that in a normal ferric sulphate solution system, by applying the ferron assay method and the modified hydrolyticity, B*, a parameter that takes into account all the possibilities of base generation and reduction. It was found that the residual Fe(II) and H2O2 under normal Fenton’s reaction conditions had little influence on the Fe(III)–ferron colorimetric reaction. Experimental results showed that the hydrolysis process of Fe(III) in the Fenton system was quite different from that in the ferric salt solution system. Under the same hydrolyticity, the hydrolysis rate of Fe(III) in the Fenton system was faster and more complicated than that in the ferric sulphate system, and the Fe(III) species produced in the Fenton system had a larger polymerization degree. With the increase in H2O2/Fe, Fea and Feb (the monomers and small polymeric Fe(III) species) increased gradually while Fec (the colloidal part) decreased, indicating that the increase in H2O2 had restrained the hydrolysis of Fe(III). This conclusion was also supported by the comparison of effective particulate diameters in the two systems. The fact that larger particles were produced with a shorter time in the Fenton system provided direct proof for the observation of the differences in the hydrolysis of Fe(III) in the two systems. The results of this study are useful for the possible utilization of the hydrolyzed Fe(III) produced in the Fenton’s system for the removal of organic pollutants.

Thermal stability of magnetite (Fe3O4) nanoparticles

ABSTRACTMagnetite (Fe3O4) nanoparticles are prime candidates for biomedical applications due to their biocompatibility and good magnetic properties. However, magnetite is highly susceptible to oxidation when exposed to the atmosphere. In order to preserve their properties, it is important for the particles to maintain their magnetite phase. In this study, magnetite nanoparticles were prepared using the conventional co3precipitation of ferrous (Fe2+) and ferric (Fe3+) chloride salt solutions with sodium hydroxide (NaOH). Thermogravimetric analysis (TGA) was subsequently carried out to identify the transition temperatures. Energy Dispersive X3Ray (EDX) spectrum shows the presence of impurities, such as sodium (Na) and chloride (Cl) ions in the as3synthesized magnetite nanoparticles. The as3synthesized samples were then calcined in a chamber furnace according to TGA data. The calcined samples were next characterised by X3ray Powder Diffraction (XRD), Transmission Electron Microscopy (TEM) and Vibrating Sample Magnetometer (VSM) to determine the changes in phase and magnetic properties of the nanoparticles as a function of different calcination temperatures.

Effect of initial pH and temperature of iron salt solutions on formation of magnetite nanoparticles

We report the effect of initial pH and temperature of iron salt solutions on formation of magnetite (Fe 3O 4) nanoparticles during co-precipitation. We synthesized nanoparticles by keeping the initial pH at 0.7, 1.5, 3.0, 4.7, 5.7, 6.7 for two different temperatures of 30 and 60 °C. When the initial pH (prior to alkali addition) of the salt solution was below 5, the nanoparticles formed were 100% spinel iron oxide. Average size of the magnetite particles increases with initial pH until ferrihydrite is formed at a pH of 3 and the size remains the same till 4.7 pH. The percentage of goethite formed along with non-stoichiometric magnetite was 35 and 78%, respectively, when the initial pH of the solution was 5.7 and 6.7. As the reaction temperature was increased to 60 °C, maintaining a pH of 6.7, the amount of goethite increased from 78 to 100%. These results show that the initial pH and temperature of the ferrous and ferric salt solution before initiation of the precipitation reaction are critical parameters controlling the composition and size of nanoparticles formed. We characterize the samples using X-ray diffraction, transmission electron microscopy and vibrating sample magnetometer. The results of the present work provide the right conditions to synthesis pure magnetite nanoparticles, without goethite impurities, through co-precipitation technique for ferrofluid applications.

Scalable synthesis of activated carbon with superparamagnetic properties

Magnetic activated carbons were obtained by in situ formation of coated superparamagnetic iron nanoparticles in the pores of carbons initially impregnated with ferric salt solution.

Akaganeite and goethite-type nanocrystals: synthesis and characterization

The synthesis of iron oxyhydroxides and hydroxides is reported in this work, by the use of a novel, simple and low-cost method. The preparation involves the hydrolysis of aqueous solutions of ferric salts followed by membrane purification and freeze drying of the products. Three different iron precursors have been tested and combined to three different volatile precipitating agents. The obtained products were akaganeite, goethite and iron(III) hydroxide. Irrespective of the starting materials used, all three products, although different in chemical nature, presented some very interesting and unique features; they consisted of nanoparticles with mean sizes ranging from 1 to 10 nm and they had very high surface areas and pore sizes in the meso- and micropore regions. The produced materials were examined by powder X-ray diffraction for crystalline phase identification, TEM and XRD for particle size estimation and nitrogen sorption for surface area, pore volume and pore size distribution measurement.