Water-soluble Iron Research Articles

Enhancing biogas production from palm oil mill effluent through the synergistic application of surfactants and iron supplements

In this study, the effects of various surfactants on the soluble chemical oxygen demand (COD) fraction and biogas production from palm oil mill effluent (POME) were investigated. A cationic surfactant (cetyltrimethylammonium bromide, CTAB) and a nonionic surfactant (Tween 80; TW80) were found to adsorb onto the particulate matter from POME, markedly reducing the soluble COD, unlike an anionic surfactant (sodium dodecyl sulfate, SDS). The mechanism underlying this phenomenon might be the adsolubilization of oil on particulate matter induced by the adsorbed surfactants. In terms of biogas production, 0.1 % w/v SDS and CTAB dramatically reduced the biogas yield, while 0.1 % w/v TW80 did not have this negative effect. A synergistic effect was observed when TW80 (0.1 % w/v) was combined with FeSO4 (400 mg/L), resulting in a 17 % greater biogas yield than that achieved with treatments using TW80 or FeSO4 alone. Moreover, the combination of TW80 and FeSO4 increased the biogas production rate. Surprisingly, the water-soluble iron fraction remained consistent across all treatments, suggesting that the adsorption of TW80 on particulate matter may limit micelle formation. Importantly, the proportion of methane in the generated biogas remained stable in all the treatments. Microbial community analysis revealed that the introduction of TW80 and FeSO4 had no discernible impact on the microbial community of the system. Pretreatment with TW80 and an iron supplement significantly enhanced biogas production and reduced the retention time of the anaerobic digestion (AD) system while maintaining the biogas quality and microbial community stability.

A Water-Soluble Chitosan Derivative for the Release of Bioactive Deferoxamine.

Deferoxamine (DFO) is a water-soluble iron chelator used pharmacologically for the management of patients with transfusional iron overload. However, DFO is not cell-permeable and has a short plasma half-life, which necessitates lengthy parenteral administration with an infusion pump. We previously reported the synthesis of chitosan (CS) nanoparticles for sustained slow release of DFO. In the present study, we developed solid dispersions and nanoparticles of a carboxymethyl water-soluble chitosan derivative (CMCS) for improved DFO encapsulation and release. CS dispersions and nanoparticles with DFO have been prepared by ironical gelation using sodium triphosphate (TPP) and were examined for comparison purposes. The successful presence of DFO in CMCS polymeric dispersions and nanoparticles was confirmed through FTIR measurements. Furthermore, the formation of CMCS nanoparticles led to inclusion of DFO in an amorphous state, while dispersion of DFO in the polymeric matrix led to a decrease in its crystallinity according to X-ray diffraction (XRD) and differential scanning calorimetry (DSC) results. An in vitro release assay indicated sustained release of DFO from CS and CMCS nanoparticles over 48 h and 24 h, respectively. Application of CMCS-DFO dispersions to murine RAW 264.7 macrophages or human HeLa cervical carcinoma cells triggered cellular responses to iron deficiency. These were exemplified in the induction of the mRNA encoding transferrin receptor 1, the major iron uptake protein, and the suppression of ferritin, the iron storage protein. Our data indicate that CMCS-DFO nanoparticles release bioactive DFO that causes effective iron chelation in cultured cells.

Shape-dependent cellular uptake of iron oxide nanorods: mechanisms of endocytosis and implications on cell labeling and cellular delivery.

The effects of nanoparticle morphology, especially size and shape, on their interactions with cells are of great interest in understanding the fate of nanoparticles in biological systems and designing them for biomedical applications. While size and shape-dependent cell behavior, endocytosis mechanism, and subcellular distribution of nanoparticles have been investigated extensively with gold and other nanoparticles, studies on iron oxide nanoparticles (IONP), one of the most promising and well-thought-of nanomaterials in biomedical applications, were limited. In this study, we synthesized oligosaccharide-coated water-soluble iron oxide nanorods (IONR) with different core sizes (nm) and different aspect ratios (i.e., length/width), such as IONR(L) at 140/6 nm and IONR(S) at 50/7 nm as well as spherical IONP (20 nm). We investigated how their sizes and shapes affect uptake mechanisms, localization, and cell viability in different cell lines. The results of transmission electron microscopy (TEM) and confocal fluorescence microscopic imaging confirmed the internalization of these nanoparticles in different types of cells and subsequent accumulation in the subcellular compartments, such as the endosomes, and into the cytosol. Specifically, IONR(L) exhibited the highest cellular uptake compared to IONR(S) and spherical IONP, 1.36-fold and 1.17-fold higher than that of spherical IONP in macrophages and pediatric brain tumor medulloblastoma cells, respectively. To examine the cellular uptake mechanisms preferred by the different IONR and IONP, we used different endocytosis inhibitors to block specific cellular internalization pathways when cells were treated with different nanoparticles. The results from these blocking experiments showed that IONR(L) enter macrophages and normal kidney cells through clathrin-mediated, dynamin-dependent, and macropinocytosis/phagocytosis pathways, while they are internalized in cancer cells primarily via clathrin/caveolae-mediated and phagocytosis mechanisms. Overall, our findings provide new insights into further development of magnetic IONR-based imaging probes and drug delivery systems for biomedical applications.

Impact of atmospheric water-soluble iron on α-pinene-derived SOA formation and transformation in the presence of aqueous droplets

Increased secondary organic aerosol formation in the presence of soluble iron and H2O2 acidic conditions in the aqueous phase.

SPIONs magnetic nanoparticles for MRI applications: Microwave synthesis and physicochemical, magnetic and biological characterizations

More and more biomedical applications used nanoparticles to improve their quality and their possibilities. Among the nanoparticles used, Superparamagnetic Iron Oxide Nanoparticles (SPIONs) are often used because these nanoparticles are biocompatible, non-toxic and the ease of synthesizing them. The aim of this study is to obtain highly water-soluble iron oxide nanoparticles using a microwave process. The SPIONs developped with this technique have a diameter between 2 nm and 4 nm range, are monodisperse and stable in an aqueous media. Indeed, with the microwaves, the control of the temperature is more precise and allows so to obtain nanoparticles with a same diameter. After the synthesis, several characterizations are carried out to determine the shape, the size, the chemical composition, the stability and the magnetic properties. Then, these SPIONs can use to control the regeneration of tissues such as cartilage tissue. For that, SPIONs are internlasized in mesenchymal stromal cells (MSCs) because these cells can to differenciate into all humans cells and allows so to regenerate all tissues: these cells are good candidate for tissue engineering. In this work, the internalization of SPIONs and the cytotocixity are studied and confirm the biocompatibility of our SPIONs. Then, for the control of the regeneration of tissues, relaxometry and MRI (Magnetic Resonance Imaging) of SPIONs are realized to compare with the commercial contrast agent present (Endorem®). For our SPIONs, the values of transverse and longitudinal relaxivities are high and in the same order to Endorem®.

One pot, scalable synthesis of hydroxide derived ferrite magnetic nanoparticles

Herein we describe a new, quite simple, highly scalable, one-pot protocol for the synthesis of ferrite nanoparticles, NPs. We immerse water insoluble iron boride, FeB, powders – in plastic bottles at temperatures between 50 °C and 80 °C and ambient pressures – for tens of hours in high pH aqueous solutions of potassium-, sodium-, tetramethylammonium-, or tetrabutylammonium-hydroxides. The resulting powder is comprised of iron oxide, Fe3O4, NPs with, in one case, a saturation magnetization of 75 Am2kg−1, that exhibit ferrimagnetic behavior, with a critical temperature of 820 K. The same protocol was used to convert water soluble iron sulphate, FeSO4, to the same NPs. The average size of the NPs depends on reaction time; after 24 h, they are in the 15 nm range; after 48 h, they are closer to 25 nm. While our approach may appear to be similar to the co-precipitation method for making such NPs, we make a strong case that our approach is significantly simpler, nonetheless reaching high magnetization of NPs.

Water soluble iron tetrasulfophthalocyanine for quantification and removal of dibutylamine from water

Water soluble iron tetrasulfophthalocyanine for quantification and removal of dibutylamine from water

Thermodynamic Characteristics of the Reactions of Formation of Iron and Magnesium Humates in Aqueous Solution

The thermodynamic stability of iron and magnesium ions at different acidity of an aqueous medium was determined using chemical thermodynamics methods and Pourbaix diagrams. The temperature dependence of the thermodynamic functions of corresponding reactions was calculated. The thermodynamic feasibility of the reactions of replacing potassium and sodium ions in aqueous solutions of humic acid salts containing carboxyl and hydroxyl functional groups with iron and magnesium ions was established. The resulting water-soluble iron and magnesium humates can have a high potential for practical use.

An effective strategy to synthesize water-soluble iron heterocomplexes containing Dubb humic acid chelating agent as efficient micronutrients for iron-deficient soils of high pH levels

Humic acid (HA), the most known and popular water-soluble organic matter extracted from a variety of sources, has many applications in agriculture. Moreover, Fe-HA complexes are water-insoluble at high pH levels and thus they cannot be applied for iron-delivery to alkaline Fe-deficient soils. To solve this issue and to increase solubility and stability of Fe-HA complexes in alkaline soils (iron delivery to plants), herein, Dubb humic acid (DHA) extracted from lignite source was used and characterized by various techniques including X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), Brunauer-Emmett-Teller (BET) surface area, UV–Visible (UV–Vis) absorption and photoluminescence (PL) spectra, diffuse reflectance spectra (DRS), Fourier-transform infrared (FT-IR) spectra, gel permeation chromatography (GPC), and laser scattering particle size distribution analysis. To achieve iron complexes which were suitable for application in iron-deficient soils, firstly, some heterocomplexes containing non-DHA primary complexing agents were designed and synthesized using ammonium citrate (AC), ammonium sulfate (AS), and fulvic acid (FA) ligands. These complexes were water-soluble and could be easily used to synthesize final iron heterocomplexes with DHA coordinating agent, which were water-soluble in neutral and alkaline conditions. The desired heterocomplex structures with general formula of (A)n-(Metal)x-(B)m (A = DHA, Metal = Fe, B = AC, AS or FA) were synthesized through optimizing pH, DHA percentage, and initial iron ion concentration. Structural characterizations of the synthesized heterocomplexes were conducted by above-mentioned techniques. Elemental analysis of these heterocomplexes (particularly the AS containing sample) showed very much higher iron contents compared with commercial iron containing chelates. These results established that iron heterocomplexes designed in this study had an extraordinary potential for acting as valuable inorganic micronutrients for iron-deficient soils in alkaline conditions.

Contrasting Effects of Nitrogen and Organic Fertilizers on Iron Dynamics in Soil after 38–Year Fertilization Practice

Various environmental factors and anthropogenic practices can affect the Fe biogeochemical cycles in soils. Nitrogen and carbon states are closely associated with Fe dynamics. However, we still have a limited understanding of the complex response of Fe biogeochemical processes to long–term nitrogen– and organic–fertilization regimes. This study investigated the Fe fraction and distribution, as well as the link between Fe and nitrogen/carbon, in bulk soil and in soil aggregates. The results showed that the long–term application of the nitrogen fertilizer increased the contents of water–soluble iron (Ws–Fe) and carbonate–bound iron (Ca–Fe) in the bulk soil and various sizes of aggregates, as well as the iron contents in soybeans. The decreased pH and enhanced Feammox reaction in response to the nitrogen–fertilizer treatments were responsible for the increase in the Ws–Fe and Ca–Fe fractions. By contrast, the long–term application of the organic fertilizer decreased the contents of Ws–Fe and Ca–Fe, while it increased the contents of Ox–Fe and Or–Fe. Moreover, the contents of Ox–Fe and Or–Fe were positively correlated with the organic–carbon contents in the micro–aggregates of 0.053–0.25 mm and <0.053 mm. These results indicated that the long–term use of the organic fertilizer encouraged Fe immobilization in organo–inorganic compounds. However, the application of the nitrogen fertilizer alleviated the Fe retention induced by the organic fertilizer. In conclusion, long–term nitrogen and organic fertilization have contrasting influences on the mineralogy and availability of Fe in soil. This study is useful for understanding the mechanism underlying the interaction between Fe and nitrogen/carbon, as well as Fe’s phytoavailability in response to different fertilization practices in brown soil.

Effects of Iron on the Occurrence Form and Release of Phosphorus in The Yellow River Sediments

There is a close relationship between Fe and P in the sediments of the Yellow River, and iron has a great influence on the occurrence form of phosphorus, except that the content of exchangeable iron increases, and the content of Pex and PAl decreases, showing a negative correlation; Water soluble iron and residual iron have a significant positive relationship with ΣP, water soluble iron and Porg, residual iron and Paut, PDe, and the correlation coefficient is high, indicating that the contents of Pex, PAl, Porg, Paut, PDe, and ΣP in the Yellow River sediments are controlled by iron forms.

μ-Oxo Dimerization Effects on Ground- and Excited-State Properties of a Water-Soluble Iron Porphyrin CO2 Reduction Catalyst

Iron 5,10,15,20-tetra(para-N,N,N-trimethylanilinium)porphyrin (Fe-p-TMA) is a water-soluble catalyst capable of electrochemical and photochemical CO2 reduction. Although its catalytic ability has been thoroughly investigated, the mechanism and associated intermediates are largely unknown. Previous studies proposed that Fe-p-TMA enters catalytic cycles as a monomeric species. However, we demonstrate herein that, in aqueous solutions, Fe-p-TMA undergoes formation of a μ-oxo porphyrin dimer that exists in equilibrium with its monomeric form. The propensity for μ-oxo formation is highly dependent on the solution pH and ionic strength. Indeed, the μ-oxo form is stabilized in the presence of electrolytes that are key components of catalytically relevant conditions. By leveraging the ability to chemically control and spectrally address both species, we characterize their ground-state electronic structures and excited-state photodynamics. Global fitting of ultrafast transient absorption data reveals two distinct excited-state relaxation pathways: a three-component sequential model consistent with monomeric relaxation and a two-component sequential model for the μ-oxo species. Relaxation of the monomeric species is best described as a ligand-to-metal charge transfer (τ1 = ∼500 fs), an ionic strength-dependent metal-to-ligand charge transfer (τ2 = 2-4 ps), and finally relaxation of a ligand field excited state to the ground state (τ3 = 5 ps). Conversely, excited-state relaxation of the μ-oxo species proceeds via cleavage of an FeIII-O bond to generate transient FeIV═O and FeII porphyrin species (τ1 = 2 ps) that recombine to the ground-state μ-oxo species (τ2 = ∼1 ns). This latter lifetime extends to timescales relevant for chemical reactivity. It is therefore emphasized that further consideration of catalyst speciation and chemical microenvironments is necessary for elucidating the mechanisms of catalytic CO2 reduction reactions.

Melatonin promotes iron uptake and accumulation in peach

• Melatonin promoted growth of peach. • Melatonin increased iron content in peach. • Melatonin increased chemical form of iron content that can be absorbed by plants. Iron deficiency leads to stunted growth in fruit trees and reduces the yield and quality of fruits. To increase the uptake of iron in fruit trees and provide a reference to control iron deficiency, the effects of different concentrations of melatonin (MT) on iron uptake in peach ( Prunus persica ) were studied by a pot experiment. Concentrations of 0, 50, 100, 150, and 200 µM MT were used in this experiment. MT increased the biomass of peach. Concentrations of 100, 150, and 200 µM MT increased the contents of total and active iron in peach. Concentration of 150 µM MT got the maxmiums of total iron contents in stems and leaves, which increased by 28.79% and 36.11%, respectively, compared with the control. Correspondingly, concentrations of 100 and 150 µM MT upregulated the genes related to iron absorption, including the ferric reduction oxidase 7 ( FRO7 ), vacuolar iron transporter 1 ( VIT1 ), and ferric reduction oxidase 4 ( FRO4 ), while downregulating the vacuole genes vacuolar iron transporter homolog 4 ( VITH4 ) and natural resistance-associated macrophage protein 3 ( NRAMP3 ) that are related to vacuolar iron transport. The concentrations of absorbable iron forms, including the water soluble iron, adsorbed iron, carbonate and strongly adsorbed iron, and manganese oxide bound iron, in the soil increased, and the soil pH value decreased following the addition of 100, 150, and 200 µM MT. A correlation analysis showed that the contents of total and active iron in peach correlated with the biomass, soil pH value, absorbable soil iron forms, and level of expression of the iron absorption related genes. These observations indicate that treated with 100–200 µM MT could promote the iron uptake and accumulation in peach by regulating the physiological metabolism related to iron.

Water-soluble iron in PM2.5 in winter over six Chinese megacities: Distributions, sources, and environmental implications

Water-soluble iron (ws-Fe) in PM2.5 plays a crucial role in biogeochemical cycles and atmospheric chemical processes. The anthropogenic sources of ws-Fe have attracted considerable attention owing to its high solubility. However, few studies have investigated the content of PM2.5 ws-Fe in the urban environment. In the present study, we characterized the spatial distributions of ws-Fe in six Chinese megacities in the winter of 2019. Furthermore, we investigated the speciation of PM2.5 ws-Fe (ws-Fe(II) and ws-Fe(III)), potential sources of ws-Fe, and association between ws-Fe and particle-bound reactive oxygen species (ROS). Higher ws-Fe concentrations were observed in northern cities (Harbin, Beijing, and Xi'an) than in southern cities (Chengdu, Wuhan, and Guangzhou). Moreover, atmospheric ws-Fe concentrations in urban China were several folds higher than those in urban areas of the United States and several orders of magnitude higher than those in remote oceans, indicating that China is a key contributor to global atmospheric ws-Fe. The dominant form of ws-Fe was ws-Fe(III) in Beijing, whereas ws-Fe(II) was more abundant in the other five cities. The concentrations of ws-Fe and ws-Fe(II) concentrations increased with increasing PM2.5 levels in all the six cities, however, we did not observe any consistent pattern of ws-Fe(III) concentration. Biomass burning was a dominant source of ws-Fe in all cities except Beijing. A strong positive correlation was observed between particle-bound ROS content and ws-Fe; this finding is consistent with those of previous studies indicating that ws-Fe in PM2.5 notably influences atmospheric chemical processes and human health.

The influence of phenyl substitutions on the dimerization of highly substituted iron(III) porphyrin hydroxo complexes

The modeling of iron porphyrins is essential in the study of heme proteins. These complexes readily undergo autooxidation and dimerization; however, this dimerization process can be inhibited by introducing phenyl groups. Herein, the dimerization of highly substituted iron(III) porphyrins is investigated. The stability of water-insoluble iron(III) hydroxo complexes was monitored via thin-layer chromatography and was found to increase with the number of phenyl groups. Dodecaphenyl-substituted complexes formed hydroxo complexes, tetraphenyl and hexaphenyl complexes formed [Formula: see text]-oxo dimers, and octaphenyl and decaphenyl complexes existed as hydroxo complex-[Formula: see text]-oxo dimer mixtures. Crystals of the dodecaphenyl-substituted iron(III) hydroxo complexes were successfully isolated. The decaphenyl-substituted complex was unique in that the respective crystals of both the hydroxo complexes and [Formula: see text]-oxo dimer could be isolated from the chloride complexes. Furthermore, the synthesis and proton equilibria of the new porphyrin iron(III) water-soluble complexes were investigated. Under neutral to basic conditions, at equilibrium, dodecaphenyl-substituted complexes exclusively formed hydroxo complexes, whereas octaphenyl, hexaphenyl, and tetraphenyl complexes exclusively formed [Formula: see text]-oxo dimers, and decaphenyl complexes existed as hydroxo complex-[Formula: see text]-oxo dimer mixtures. Additionally, the order of the dimerization reaction was examined using the initial-rate and half-life methods, which confirmed that the dimerization is a second-order reaction that follows a mechanism wherein two hydroxo complexes form a dihydroxo-bridged intermediate. This result was supported by the dimerization of water-soluble iron(III) hydroxo complexes. The new hydroxo complexes with non-planar porphyrin cores synthesized in this study are expected to have a significant impact on heme protein reaction modeling.

Low source-inherited iron solubility limits fertilization potential of South American dust

Where atmospheric processing is weak due to low anthropogenic emissions, fertilization of iron-limited oceans by non-volcanic mineral dust aerosols strongly depends on iron solubility at the sources. Southern South America (SSA) is a pristine environment and the main dust supplier to the southern oceans, the most sensitive to iron fertilization. Thus, the present-day lack of SSA dust fertilization of the southern oceans is hypothesized to reflect low source-inherited iron bioavailability. However, a dearth of geochemical studies on SSA dust prevents testing this hypothesis. To remedy this, we conducted the first systematic sampling of SSA dust sources. Iron leaching experiments showed fractional solubilities of close-to-source dust (bulk) and dust-emitting surface sediments (<63 µm) in pure water (0.05 ± 0.05%), seawater (0.03 ± 0.04%) and 1% nitric acid (5 ± 6%) that imply a low mass-normalized fertilization potential of SSA dust compared to dust from other regions. Based on grain size, size-resolved mineralogy, elemental chemistry and iron speciation determinations, we found that variability in labile iron is enhanced by high clay contents, small grain size and higher proportions of paramagnetic versus non-paramagnetic iron, irrespective of oxidation state. The independence of the most labile, water-soluble iron on grain size and its strong negative correlation to the Chemical Index of Alteration may imply that we currently underestimate the role of coarse glaciogenic dust as a supplier of bioavailable iron during drier-than-present ice ages when continental chemical weathering was reduced, and during which enhanced supply of dust-borne bioavailable iron to the southern oceans is observed.

Ultrafiltration to characterize PM2.5 water-soluble iron and its sources in an urban environment

Soluble forms of transition metals in airborne particles are linked to adverse health impacts. Iron (Fe) is often the most abundant transition metal in ambient PM2.5. In Atlanta, the water-soluble fraction of Fe had a stronger association with adverse cardiovascular outcomes than PM2.5 mass and total Fe. Water solubility is operationally defined. One determining factor is the pore size in the liquid filtration (0.45 μm in this study) used to isolate water-soluble species, implying colloidal particles smaller than the pore size may be included in the water-soluble group. Here, we characterize the properties of PM2.5 water-soluble iron (WS Fe) utilizing ultrafiltration and investigate sources of the various isolated fractions based on one-year of samples collected in urban Atlanta (N = 355). Annual average Fe solubility (WS Fe divided by total Fe) was 12%, with the highest solubility in the warm season (May–Sept.) when aerosol acidity (pH of 1.8–2.7) and oxalate concentrations were highest. Ultrafiltration showed that 84% of WS Fe (extract that passed through 0.45 μm pore filter) was smaller than nominally 4 nm, with 61% of the soluble iron was smaller than nominally 2 nm. A correlation analysis, experiments involving addition of oxalate to sample extract and a pH cycling experiment with selected Fe species were consistent with the oxalate-Fe ligand being mainly found in the smallest ultrafiltrate size (< nominally 2 nm), whereas pH cycling could lead to the formation of colloidal particles with sizes between nominally 2–4 nm. Magnetite, a solid Fe nanoparticle (smaller than 0.1 μm) detected in human organs in previous studies, was undetectable in the PM2.5 WS Fe in urban Atlanta. These data show that most WS Fe is composed of soluble species or very small colloidal particles (roughly <4 nm), making them highly bioavailable.

Understanding the mechanisms of zeolite in inhibiting Pb accumulation in different rice cultivars (Oryza sativa).

Zeolite is one of the potential passivating amendments for the immobilization of lead (Pb) in contaminated farmland soils. In this study, pot experiments were carried out to investigate the effects and the mechanisms of zeolite on Pb accumulation in two rice cultivars grown in a slightly Pb-contaminated soil. Results showed that Pb content in grains of Zheyou 18 (ZY-18) decreased by the addition of 6g zeolite kg-1 soil (E6), which can be attributed to the reduction in soil Pb availability, dissolved organic carbon (DOC), water-soluble iron (Fe) and manganese (Mn), and the transfer factor from soil to grain (TFsoil-grain). These reductions were mainly resulting from the significant increase in soil pH, glutathione (GSH), phytochelatins (PCs), and non-protein (NPT) content in rice root, and the decrease in soil redox potential (Eh), due to zeolite addition. Pb content in brown rice of DL-5 was not significantly affected with E6 treatment, whereas it was raised by applying 12g zeolite kg-1 soil (E12). The increase of Pb content of Donglian 5 (DL-5) grains with E12 treatment can be attributed to more Pb uptake by the root, higher Pb transfer factors (TFs) between various parts of rice, and significant decrease in GSH, PCs, and NPT contents in the root. It is concluded that a suitable rate of zeolite addition can immobilize Pb in slightly Pb-contaminated acidic soil. However, the final immobilization effect also depends on rice cultivars.

Effects of organic acids on heavy metal release or immobilization in contaminated soil

In order to explicit the environmental activity of heavy metals affected by different organic acids in soil, a batch incubation experiment was explored to investigate the influence of high relative molecular mass organic acid (HMWOA) (humic acid and fulvic acid) and low relative molecular mass organic acid (LMWOA) (threonic acid and oxalic acid) on the release or immobilization of Pb, Cu and Cd in soils. Results showed that LMWOA, especially threonic acid, had a good performance in the release of Pb, Cu and Cd from soils, and decrease in the fractions of HOAc-extractable, reducible and oxidable Pb, Cu and Cd. Conversely, HMWOA, especially humic acid, decreased the release of Pb, Cu and Cd, while it increased the fractions of HOAc-extractable, reducible and oxidable Pb, Cu and Cd, indicating that HMWOA can immobilize heavy metals. The release of Pb, Cu and Cd caused by LMWOA was attributed to the dissociation of soil organic matter and amorphous iron oxides since the total organic carbon and the water-soluble iron increased. The immobilization of Pb, Cu and Cd by HMWOA was attributed to the adsorption onto HMWOA followed by amorphous iron since HMWOA resulted in a significant decrease of zeta potential and an increase of amorphous iron oxide. It can be concluded that LMWOA has a potential application in soil washing remediation, while HMWOA can be used in the immobilization remediation for heavy metals contaminated soils.

Fortification of foods with nano-iron: its uptake and potential toxicity: current evidence, controversies, and research gaps.

Iron fortification is a very popular practice in several countries, particularly in countries in which a large proportion of the population is suffering from iron deficiency, as in lower-middle-income countries. Food fortification with iron salts is a difficult operation, because most iron complexes (ferrous sulfate, ferrous chloride) are water soluble, which can cause undesirable alterations to the sensory properties of the food carriers. On the other hand, insoluble iron salts (eg, ferric pyrophosphate) do not have an unpleasant taste or color, but their bioavailability is low. These issues can be addressed with iron nanoparticles. The small particle size has been shown to have a significant impact on iron absorption. Iron nanoparticles with smaller particle sizes have more surface area, which improves their solubility in gastric juice and leads to better bioavailability. When compared with water-soluble iron complexes, nano-sized iron compounds generate negligible organoleptic alterations in food carriers. As a result, iron nanoparticles could be potentially used in food fortification to minimize iron-deficiency anemia. This review focuses on the absorption pathway and the toxicity of various forms of iron nanoparticles. In vitro cell studies and animal studies indicate that nano-sized iron particles can be taken up either by the Divalent Metal Transporter 1 pathway or the endocytic pathway. Nano-sized ferric phosphate and iron(III) oxo hydroxide show the most promising results, based on recent studies on fortification. To date, there are insufficient studies on the maximum intake level and potential adverse effects. Further extensive work is essential before introducing nano-iron compounds as food fortificants.