Absence Of Fe2 Research Articles

Sulfidation of Nanoscale Zero-Valent Iron by Sulfide: The Dynamic Process, Mechanism, and Role of Ferrous Iron.

Sulfidation of nanoscale zerovalent iron (nZVI) can enhance particle performance. However, the underlying mechanisms of nZVI sulfidation are poorly known. We studied the effects of Fe2+ on 24-h dynamics of nZVI sulfidation by HS- using a dosed S to Fe molar ratio of 0.2. This shows that in the absence of Fe2+, HS- rapidly adsorbed onto nZVI particles and reacted with surface iron oxide to form mackinawite and greigite (<0.5 h). As nZVI corrosion progressed, amorphous FeSx in solution deposited on nZVI, forming S-nZVI (0.5-24 h). However, in the initial presence of Fe2+, the rapid reaction between HS- and Fe2+ produced amorphous FeSx, which deposited on the nZVI and corroded the surface iron oxide layer (<0.25 h). This was followed by redeposition of colloidal iron (hydr)oxide on the particle surface (0.25-8 h) and deposition of residual FeSx (8-24 h) on S-nZVI. S loading on S-nZVI was 1 order of magnitude higher when Fe2+ was present. Surface characterization of the sulfidated particles by TEM-SAED, XPS, and XAFS verified the solution dynamics and demonstrated that S2- and S22-/Sn2- were the principal reduced S species on S-nZVI. This study provides a methodology to tune sulfur loading and S speciation on S-nZVI to suit remediation needs.

Chitosan-based fluorescent probe for the detection of Fe3+ in real water and food samples

Iron ions play a crucial role in the environment and the human body. Therefore, developing an effective detection method is crucial. In this paper, we report CNS2, a chitosan-based fluorescent probe utilizing naphthalimide as a fluorophore. CNS2 is designed to “quench” its own yellow fluorescence through the specific binding of compounds containing enol structures to Fe3+. Studying the fluorescence lifetime of CNS2 in the presence or absence of Fe3+ reveals that the quenching mechanism is static. The presence of multiple recognition sites on the chitosan chain bound to Fe3+ gave CNS2 rapid recognition (1 min) and high sensitivity, with a detection limit as low as 0.211 μM. Moreover, the recognition of Fe3+ by CNS2 had a good specificity and was not affected by interferences. More importantly, in this study, CNS2 was successfully utilised to prepare fluorescent composite membranes and to detect Fe3+ in real water samples and a variety of food samples. The results show that the complex sample environment still does not affect the recognition of Fe3+ by CNS2. All the above experiments obtained more satisfactory results, which provide strong support for the detection of Fe3+ by the probe CNS2 in practical applications.

The blue color mechanism on sapphires from different gem deposits before and after heating under oxidizing atmosphere

The blue color of sapphire is commonly related to the amount of Fe and Ti impurities replacing Al3+ in the Al2O3 structure. Generally, the color intensity on sapphires is related to the gem deposits including the basaltic-related and metamorphic-related ones. The color of sapphires has been changed after heating under oxidizing atmosphere. However, the explanation about the color mechanism from some previous research contradicted each other and it was still wondered. For this reason, this research is focused on the role of Fe and Ti oxidation states as well as the blue color mechanism on sapphires before and after heating under oxidizing atmosphere. In this study, the sapphire samples were collected from different gem deposits including basaltic-related sapphires from Kanchanaburi province, Thailand and metamorphic-related ones from Sri Lanka before and after heating at 1100 °C under oxidizing atmosphere. As a result, the blue color on sapphires before heating can be described as a hole color center assigned to Fe3+-Ti4+ mixed acceptor states inside an energy band gap that could receive an electron from the valence band for charge-balancing after excitation. After heating, the basaltic-related sapphires turned from dark blue to light blue and the metamorphic-related ones turned from light blue to colorless. The Fe3+-Ti4+ mixed acceptor states were decreased because a hole color center was filled by an electron from oxygen during the heating process instead of an electron from the valence band. Therefore, it can be concluded that the blue color mechanism on sapphires before and after heating under an oxidizing atmosphere can be explained by an energy band model involving the presence or absence of Fe3+-Ti4+ mixed acceptor states as well as a hole color center inside an energy band gap.

Molecular Regulatory Mechanism of the Iron-Ion-Promoted Asexual Sporulation of Antrodia cinnamomea in Submerged Fermentation Revealed by Comparative Transcriptomics.

Antrodia cinnamomea is a precious edible and medicinal fungus with activities of antitumor, antivirus, and immunoregulation. Fe2+ was found to promote the asexual sporulation of A. cinnamomea markedly, but the molecular regulatory mechanism of the effect is unclear. In the present study, comparative transcriptomics analysis using RNA sequencing (RNA-seq) and real time quantitative PCR (RT-qPCR) were conducted on A. cinnamomea mycelia cultured in the presence or absence of Fe2+ to reveal the molecular regulatory mechanisms underlying iron-ion-promoted asexual sporulation. The obtained mechanism is as follows: A. cinnamomea acquires iron ions through reductive iron assimilation (RIA) and siderophore-mediated iron assimilation (SIA). In RIA, ferrous iron ions are directly transported into cells by the high-affinity protein complex formed by a ferroxidase (FetC) and an Fe transporter permease (FtrA). In SIA, siderophores are secreted externally to chelate the iron in the extracellular environment. Then, the chelates are transported into cells through the siderophore channels (Sit1/MirB) on the cell membrane and hydrolyzed by a hydrolase (EstB) in the cell to release iron ions. The O-methyltransferase TpcA and the regulatory protein URBS1 promote the synthesis of siderophores. HapX and SreA respond to and maintain the balance of the intercellular concentration of iron ions. Furthermore, HapX and SreA promote the expression of flbD and abaA, respectively. In addition, iron ions promote the expression of relevant genes in the cell wall integrity signaling pathway, thereby accelerating the cell wall synthesis and maturation of spores. This study contributes to the rational adjustment and control of the sporulation of A. cinnamomea and thereby improves the efficiency of the preparation of inoculum for submerged fermentation.

Ferric Hydroxide Recovery from Iron-Rich Acid Mine Water with Calcium Carbonate and a Gypsum Scale Inhibitor

The focus of this study was to improve the Reverse Osmosis Cooling (ROC) process by using CaCO3 for neutralization and selective recovery of Fe(OH)3 at pH 3.5. By using a specific inhibitor, ferric hydroxide was recovered separately from gypsum and other metals present in mine water. Ferric hydroxide was processed to pigment, a product that is imported and used as colorant in paints and tiles. In addition to pigment recovery, aluminum hydroxide and calcium carbonate can also be recovered from mine water. The following conclusions were made: (i) the rate of gypsum crystallization, in the absence of Fe3+, is influenced by the over saturation concentration in solution, the seed crystal concentration and temperature; (ii) gypsum crystallization from an over-saturated solution, in the presence of Fe(OH)3 sludge, required an inhibitor dosage of 100 mg/L to keep gypsum in solution for a period of 30 min; (iii) gypsum crystallization from an over-saturated solution, in the presence of both Fe(OH)3 sludge and CaCO3 reactant, required a higher inhibitor dosage than 100 mg/L to keep gypsum in solution for a period of 30 min. A dosage of 200 mg/L kept gypsum in solution for the total reaction period; (iv) when only Fe(OH)3 is present in the slurry, gypsum inhibition is more effective when Fe(OH)3 sludge is allowed to settle after the initial mixing; (v) when both Fe(OH)3 and CaCO3 are present in the slurry, gypsum inhibition is more effective when the inhibitor is added over a period of time (10 min) rather than applying the total dosage at time zero; (vi) Fe(OH)3 can be changed to yellow pigment (Goethite) by heating to 150 °C and to red pigment (Hematite) by heating to 800 °C. Pigment of nano particle size was produced; (vii) in the case of Na2CO3, the TDS increased from 12,660 mg/L in the feed to 13,684 mg/L due to the replacement of metal ions (Fe3+, Al3+, Fe2+, Mn2+ and Ca2+) with Na+ in solution. In the case where CaCO3 was used for the removal of Fe3+ and Al3+, Ca(OH)2 for the removal of Fe2+, Mn2+, and Na2CO3 for the removal of Ca2+, the TDS dropped from 12,661 mg/L to 2288 mg/L, due to gypsum precipitation. The alkali cost in the case of calcium alkalis amounted to ZAR29.43/m3 versus ZAR48.46/m3 in the case of Na2CO3.

Enhanced Fenton-like degradation of Rhodamine B and Congo red by benzene and K+ co-doped carbon nitride with in situ-generated H2O2

BackgroundFe2+/H2O2-based photo-Fenton process is often used in pollutions removal. But, Fe-species related low activity at neutral condition hinders their practical applications. Activation of in situ generated H2O2 for Fenton-like degradation of pollutions through catalysts absences of Fe species is expected. MethodsA strip-like benzene and K+ co-doped g-C3N4 (KBCN) was constructed by the thermal polymerization of assembly of melamine and 2-aminoterephthalic acid, then post-calcination in LiCl–KCl molten salt, which was then used to degrade Rhodamine B (RhB) and Congo red (CR) via in situ generated H2O2. Significant findingsBenzene and K+ co-doping were critical both in increasing charge separation and enhancing the H2O2 production. The yield of H2O2 for KBCN was 57.5 μM in pure water after 60 min irradiation. In the absence of Fe2+, the in situ generated H2O2 could subsequently degrade RhB and CR with the formed ·OH. The apparent rate constants of KBCN for RhB and CR degradation were 0.0446 and 0.0497 min−1, respectively. The advantages of degradation with in situ generated H2O2 in the absence of Fe2+ can provide a new prospective to the environmental friendly Fenton-like reaction.

Kinetic comparison of photocatalysis with H2O2-free photo-Fenton process on BiVO4 and the effective antibiotic degradation

In order to eliminate the serious environment pollution and the super bacteria generation caused by antibiotics discharge, it is an urgently challenging task for effective degradation of antibiotics. Many advanced oxidation technologies including Fenton and photocatalytic reactions have been adopted to face with the challenge of this issue. Herein, we developed a H2O2-free photo-Fenton process using BiVO4 as a light absorbing semiconductor with the addition of Fe3+ to degrade antibiotic under a 300 W Xenon lamp and further comparably investigated the kinetics of H2O2-free photo-Fenton and photocatalytic reactions to degrade rhodamine B (Rh B) and rhodamine 6G (Rh 6G). The corresponding reaction mechanism was proposed based on detailed experiments and data analysis. Subsequently using norfloxacin (NOR) as a model, the H2O2-free photo-Fenton reactions were adopted to evaluate the effectiveness of antibiotic degradation with the optimized conditions of pH = 3.0 and the Fe3+ concentration of 100 mg/L. The results displayed that the H2O2-free photo-Fenton reaction on BiVO4 conformed to pseudo-first-order kinetics and exhibited excellent antibiotic removing performance, the degradation ratio of NOR reached 96% within 1 h. While its photocatalytic cousin abided by pseudo-zero-order kinetics and its degradation ratio was only 25% with the absence of Fe3+ under the same conditions. It is anticipated that this study can deepen the understanding of mechanism and kinetics between photo-Fenton with photocatalytic reactions on the same catalyst and the expansion of H2O2-free photo-Fenton reactions on other semiconductors has great potential in the treatment of wastewater containing various antibiotics.

On the performance of distinct electrochemical and solar-based advanced oxidation processes to mineralize the insecticide imidacloprid

Water contamination by contaminants of emerging concern is one of the main challenges to be solved by our desired sustainable society. In the same time, different technologies for water treatment are becoming enough mature to be implemented. In this work, two different advanced oxidation processes (AOP) were investigated: i) electrochemical processes (electrochemical, photoassisted electrochemical, electro Fered-Fenton, and photo-electro Fered-Fenton – PEF-Fered) using a BDD and DSA® electrodes under UVA and UVC irradiation (9 W) and ii) solar-based AOP using four distinct oxidants (HOCl, H2O2, S2O82−, HSO5−) in the presence or absence of Fe2+ ions to oxidize and mineralize imidacloprid (IMD: 50 mg L−1) containing solutions. The PEF-Fered (1.0 mM Fe2+ and 50 mg L−1 h−1 H2O2) under UVA or UVC irradiation and HOCl/UVC (NaCl 17 mM) processes using a BDD and DSA® electrodes (10 mA cm −2), respectively, performed equally well to completely oxidize and mineralize (∼90%) IMD at the expense of only ∼0.3 kWh g−1. Low amounts and highly oxidized byproducts identified through liquid chromatography tandem mass spectrometry were observed for the HOCl/UVC process using a DSA® electrode. Concerning the solar-based AOP, all assessed oxidants (4 mM h−1) successfully oxidized IMD within 3 h of treatment, whereas only H2O2 and HOCl led to significant (∼60%) TOC abatement after 6 h treatment. The use of Fe2+ (0.5 or 1.0 mM) had no significant improvement in the oxidation and mineralization of IMD.

Enhanced biodegradation of chlorobenzene via combined Fe3+ and Zn2+ based on rhamnolipid solubilisation

Biotrickling filters (BTFs) for hydrophobic chlorobenzene (CB) purification are limited by mass transfer and biodegradation. The CB mass transfer rate could be improved by 150 mg/L rhamnolipids. This study evaluated the combined use of Fe3+ and Zn2+ to enhance biodegradation in a BTF over 35 day. The effects of these trace elements were analysed under different inlet concentrations (250, 600, 900, and 1200 mg/L) and empty bed residence times (EBRTs; 60, 45, and 32 sec). Batch experiments showed that the promoting effects of Fe3+/Zn2+ on microbial growth and metabolism were highest for 3 mg/L Fe3+ and 2 mg/L Zn2+, followed by 2 mg/L Zn2+, and lowest at 3 mg/L Fe3+. Compared to BTF in the absence of Fe3+ and Zn2+, the average CB elimination capacity and removal efficiency in the presence of Fe3+ and Zn2+ increased from 61.54 to 65.79 g/(m3⋅hr) and from 80.93% to 89.37%, respectively, at an EBRT of 60 sec. The average removal efficiency at EBRTs of 60, 45, and 32 sec increased by 2.89%, 5.63%, and 11.61%, respectively. The chemical composition (proteins (PN), polysaccharides (PS)) and functional groups of the biofilm were analysed at 60, 81, and 95 day. Fe3+ and Zn2+ significantly enhanced PN and PS secretion, which may have promoted CB adsorption and biodegradation. High-throughput sequencing revealed the promoting effect of Fe3+ and Zn2+ on bacterial populations. The combination of Fe3+ and Zn2+ with rhamnolipids was an efficient method for improving CB biodegradation in BTFs.

Iron speciation in Opalinus clay minerals

Clay formations are under considerations in various countries to host a deep geological repository for high-level nuclear waste owing to beneficial physicochemical properties. These properties can, however, be influenced by the chemical form of structural Fe. The goal of this study was to obtain information on speciation of Fe associated with the clay fraction separated from the Opalinus clay rock, one of the clay formations at an advanced stage of repository planning. The clay rock was purified and the clay fraction was separated. Analyses by X-ray powder diffraction evidenced the presence of 1:1 (kaolinite) and 2:1 layer minerals (e.g., illite and possibly illite/smectite mixed layers), no other phase in significant amounts could be detected. Infrared spectroscopy corroborated the presence of both 1:1 and 2:1 layer minerals, and the absence of Fe3+2-OH bending in the spectrum ruled out extensive Fe clustering and hinted at a rather homogeneous distribution within the structure. Information on Fe speciation was obtained by X-ray absorption spectroscopy (XAS) at the K-edge. To reduce uncertainties on structural parameters, overlapping contributions from in-plane and out-of-plane shells were filtered by recording polarized XAS data. The position of the pre-edge features indicated the prevalence of Fe3+, while the intensity and splitting were typical of Fe located at octahedral site. The pre-edge of the reference kaolinite differed from that of the Opalinus clay sample, excluding the prevalence of Fe within that 1:1 layer mineral. Data thus suggested the prevalence of Fe3+ within the octahedral sheet of 2:1 layers. Polarized XANES and EXAFS exhibited significant angular dependencies hinting at the presence of various neighboring shells with specific orientations. The first O shell located at 2.03 Å contains about six O atoms oriented in-plane. At higher distances, three in-plane Al/Mg and Fe and about four out-of-plane Si atoms were detected at ~3.05 Å and 3.23 Å, respectively, suggesting that Fe is located in a dioctahedral octahedral sheet of 2:1 layers. The presence of significant amounts of Fe in the tetrahedral sheet was excluded. Combining results from XAS with that from chemical analysis enabled to estimate first the structural formula of the 2:1 layer fraction and subsequently the proportions of 1:1 and 2:1 layer minerals within the purified clay fraction of the Opalinus rock. The estimated proportions of 1:1 and 2:1 layer minerals were in reasonable agreement with that of the whole Opalinus rock.

Selenium enhances iron plaque formation by elevating the radial oxygen loss of roots to reduce cadmium accumulation in rice (Oryza sativa L.)

The inhibition of cadmium (Cd) absorption by selenium (Se) in rice may be associated with iron plaque (IP) formation, but the driving mechanisms are still unclear. This study investigated the effects of Se on the growth, oxidative toxicity, radial oxygen loss (ROL), IP formation, and Cd absorption of rice exposed to Cd. The results of this study showed that Cd stress elevated the levels of O2– and H2O2 and depressed superoxide dismutase (SOD) and catalase (CAT) activities. The maximum ROL and IP were reduced by 43.3 % and 74.5 %, respectively. However, Se alleviated Cd toxicity by stimulating SOD and CAT activities by scavenging O2– and H2O2 and enhancing the ROL profiles. Under culture conditions without Fe2+, Se had no impact on the total Cd levels in rice (TCd). However, with the addition of Fe2+, TCd was significantly reduced by 23.3 % due to the enhancement of IP formation by Se. These results indicated that Se can reduce Cd accumulation in rice in the presence of Fe2+ treatments. However, Se just alleviated Cd toxicity in the absence of Fe2+ treatments. The enhancement of ROL was a potential reason for the elevated IP formation induced by Se.

Degradation of sulfathiazole by electro-Fenton using a nitrogen-doped cathode and a BDD anode: Insight into the H2O2 generation and radical oxidation

In this work, nitrogen-doped cathodes for high H2O2 production and sulfathiazole (STZ) degradation in electro-Fenton (EF) systems were prepared by the carbonization of three carbon/nitrogen-enriched precursors. Among the cathodes elaborated from different precursors, the one using 1h-1,2,4-triazole-3,5-diamine as the precursor showed the best oxygen reduction reaction (ORR) ability with the normalized H2O2 accumulation of 9.49 ± 0.03 mg L−1 h−1 cm−2 compared to the other two N-containing cathodes. The enhanced H2O2 accumulation was attributed to the high electroactive surface area and pyrrolic N (60.45%) content. Regarding reactive oxygen species in the absence of Fe2+, aside from the H2O2, O2−and 1O2 were identified using spectroscopic techniques and chemical probes. As a result, a degradation and mineralization efficiency of 98.25 ± 0.14% and 70.57 ± 0.27% of STZ were attained in the 180-min treatment, mainly coming from the homogeneous OH from classical Fenton, anodic OH on BDD anode and direct/indirect oxidation of O2−and 1O2. In addition, the plausible degradation pathway of STZ was proposed based on the density functional theory (DFT) combined with experimental data derived by ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). The frontier orbital theory and Fukui function theoretically suggested the vulnerable sites of STZ for different active species including OH, O2− and 1O2. This study provides a new strategy for improving the ORR process and analyzing the generation and conversion of reactive oxygen species in the EF process.

Outer membrane protein OmpU is related to iron balance in Vibrio alginolyticus

Outer membrane protein U (OmpU) is a major porin from Vibrio alginolyticus and has been considered a vaccine candidate against infection by V. alginolyticus. After pre-incubated with polyclonal antibody against rOmpU, V. alginolyticus showed a 78% decrease in extracellular iron level, suggesting that interruption of OmpU could increase intracellular iron level. The mRNA expression of ompU under iron-limited conditions was determined using real-time reverse transcriptase PCR. The mRNA level of ompU was downregulated to 0.27-, 0.036- and 0.019-fold after the addition of the iron chelator 2,2′-bipyridyl for 10, 30 and 60 min, respectively. In addition, the promoter of ompU contained a ferric uptake regulator (Fur) binding site, which revealed the potential regulation of ompU by Fur and iron. Fur from V. alginolyticus was purified and used for electrophoretic mobility shift assay. The result showed that in the absence of Fe2+, purified recombinant Fur could specifically bind to the promoter DNA of ompU, while in the presence of Fe2+, the binding of Fur and the promoter DNA was suppressed. Our study preliminarily explored the function of OmpU in iron balance in V. alginolyticus, and these findings were helpful in understanding iron metabolism in V. alginolyticus.

Dual-mode colorimetric and fluorometric probe for ferric ion detection using N-doped carbon dots prepared via hydrothermal synthesis followed by microwave irradiation

Dual-mode colorimetry and fluorescence detection methods have gained more attentions in recent years. In this paper, a colorimetric and fluorescent dual-mode probe was constructed based on N-doped carbon dots (CDs) that was synthesized using hydrothermal heating followed by microwave irradiation. The CDs were purified using a polarity-based method followed by a size-based method. The CDs selectively form a purple-colored complex with Fe3+ ions accompanied by quenching of the fluorescence emission. The fluorescence emission of CDs was not affected by common metal cations and anions, but was only complexed and quenched by Fe3+ ions. Cyclic voltammetry and optical spectroscopy were used to measure the HUMO and LUMO levels of the CDs. The fluorescence quenching is due to the transfer of the photo-induced electrons from the excited state of the CDs to the LUMO of Fe3+ ions. The fluorescence lifetime of CDs in the presence and absence of Fe3+ was examined by time-correlated single-photon counting. These results along with changes in the absorption spectra suggest a static fluorescence quenching mechanism. The CDs were used as a dual-readout probe for the colorimetric and fluorescent detection of Fe3+ ions in real samples. The lower limit of detection obtained using colorimetry was 0.5 μM (S/N = 3), while that obtained using fluorimetry was 50 nM. The fluorescence intensity of the CDs is pH independent between 2 and 9, which increases the working range for practical application. Furthermore, the CDs in aqueous solution are photostable, thermostable, and stable under high ionic strength, which makes the probe robust and rugged.

An XAS study of silver species evolution in silver-catalysed chalcopyrite bioleaching

The catalysing effect of Ag+ or Ag nanoparticle (AgNp) on chalcopyrite (bio)leaching at 30 °C was studied in this paper, and the change of Ag speciation was investigated by Ag K-edge X-ray Absorption Near-edge Spectroscopy (XANES). The solution studies indicate that the addition of 0.2% Ag (fraction of Ag to chalcopyrite) can effectively improve the dissolution of chalcopyrite in both bioleaching and chemical leaching. Further increasing the silver concentration to 1% only marginally increase the rate of chalcopyrite dissolution compared with the rate with 0.2% Ag added. No obvious difference has been found between the catalytic effect of Ag+ and AgNp (Silver Nanoparticle). XRD studies indicate the formation of jarosite, elemental sulfur in both bioleaching and chemical leaching. However, the speciation of Ag in the residual cannot be confirmed by XRD analysis. Ag k-edge XANES spectra show that Ag+ or AgNp have completely changed to Ag2S within 7 days in both bioleaching and chemical leaching process. In-situ XANES analysis shows that the Ag+ or AgNp changed to Ag2S very rapidly in the absence of Fe3+. In contrast, AgCl was firstly detected with the presence of 3 g/L Fe3+, which only partially changed to Ag2S in about 36 h, which is likely because the stability of Ag2S was decreased by Fe3+.

Logic gate behavior and intracellular application of a fluorescent molecular switch for the detection of Fe3+ and cascade sensing of F- in pure aqueous media.

The nature and coordination sites of the Schiff base 3,3'-(1E,1'E)-(1,3-phenylenebis(azan-1-yl-1-ylidene))bis(methan-1-yl-1-ylidene)dinaphthalen-2-ol (APHN) were tuned by its selective reduction to design a highly efficient fluorescent probe, 3,3'-(pyridine-2,6-diylbis(azanediyl))bis(methylene)dinaphthalen-2-ol (RAPHN). The structures of APHN, RAPHN, and the RAPHN-Fe3+ complex were satisfactorily modeled from the results of density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations. RAPHN worked in pure aqueous medium as a turn on-off-on probe of Fe3+ and F-. The fluorescence nature of the probe in the presence and absence of Fe3+/F- was regulated by a set of mechanisms including -CH[double bond, length as m-dash]N isomerization and LMCT. A 2 : 1 (M : L) binding stoichiometry was established from a fluorescence Job's plot and further substantiated from HR-MS studies. The limits of detection of RAPHN for Fe3+ and RAPHN-Fe3+ for F- were found to be 2.49 × 10-7 M and 1.09 × 10-7 M, respectively. The RAPHN probe caused no cytotoxicity in gut tissue of Drosophila even at high concentrations. The probe displayed excellent bioimaging applications for detection of Fe3+ and F- in gut tissue of Drosophila. A combinatorial logic gate was constructed for the proper understanding of the working principle of RAPHN.

Comment on Jiang Y, Zhang J, Xi B, et al. [Degradation of toluene-2,4-diamine by persulphate. Environ Tech. 2015;36:1441–1447

This paper reports studies on the reaction between peroxydisulfate and 2,4-diaminotoluene. The variables include pH, peroxydisulfate concentration, and the presence or absence of Fe2+. A radical re...

Color mechanisms in spinel: a multi-analytical investigation of natural crystals with a wide range of coloration

Twenty natural spinel single crystals displaying colors almost representative for the entire spinel variability were investigated by electron microprobe and UV–VIS–NIR–MIR and FTIR spectroscopies. Eight of them, selected among the Fe-bearing ones, were also analyzed by X-ray diffraction, and five by Mossbauer spectroscopy to obtain information on the oxidation state and site distribution of Fe. The adopted multi-analytical approach was successful in revealing that the color displayed by aluminate spinel crystals is due to a combination of two or more minor transition elements acting as chromophore, such as V3+, Cr3+, Fe2+, Fe3+, Mn2+ and Mn3+, variably distributed in the tetrahedrally and octahedrally coordinated sites of the spinel structure. Iron-poor orange, red and magenta spinel crystals owe their color mainly to the presence of V3+ and Cr3+ at the M sites (with predominance of V3+ for orange and of Cr3+ for red color). Iron-rich pink, blue and green spinel crystals, in spite of exhibiting very different colors, have relatively similar optical absorption spectra characterized by a strong UV-edge absorption and a series of weak absorption bands in the visible range. From pink to blue and green spinel samples, color differences depend on the increase of Fetot (primarily) and Fe3+ contents (secondarily), which are responsible for both the intensification of UV-edge absorption and the different intensity, width and position of the prominent absorption bands occurring in the range 18,000−15,000 cm−1. The scarcity in nature of yellow spinel is explained by the rarity of conditions necessary to obtain the yellow color, such as the exclusive presence of Mn acting as a chromophore or at least the absence of Fe2+, to avoid masking of the weak electronic transitions in Fe3+, Mn2+ and Mn3+.

Degradation kinetics and mechanism of desethyl-atrazine and desisopropyl-atrazine in water with [rad]OH and SO4[rad]− based-AOPs

Desethyl-atrazine (DEA) and desisopropyl-atrazine (DIA) are the two major degradation by-products of atrazine (a suspected human carcinogen and endocrine disrupting herbicide), and show an equal toxicity to their parent compound. This study investigated the degradation of DEA and DIA with OH and SO4− generated from the activation of peroxides, i.e., persulfate (S2O82−), peroxymonosulfate (HSO5−) and hydrogen peroxide (H2O2), by UV-254nm radiation in the presence or absence of Fe2+. Quantum yields of DEA and DIA were independent of pH (3.0–11.0). The higher quantum yield of reactive radicals from UV/S2O82−, i.e., 1.8 compared to 1.04 for UV/HSO5− and 1.0 for UV/H2O2, resulted in greater efficiency of UV/S2O82− for both DEA and DIA degradation. The second-order rate constants of DEA and DIA with SO4− were calculated to be (6.42±0.12)×108 and (1.70±0.30)×109 M−1s−1, and that with OH were (1.14±0.09)×109 and (2.22±0.44)×109 M−1s−1, respectively, suggesting a strong impact of side chains toward radical reactions. Fe2+ promoted slightly the activation of the examined peroxides at pH 7.4. Presence of organic matter and alkalinity in field water samples negatively influenced the efficiency of UV/S2O82−. Based on the identified degradation by-products by GC–MS, potential degradation pathways were proposed for both compounds. The results obtained suggested that DEA and DIA can be efficiently removed from the contaminated water by OH and SO4− based-AOPs.

Structural, thermal and magnetic studies of MgxZn1−xFe2O4 nanoferrites: Study of exchange interactions on magnetic anisotropy

Polycrystalline nanoferrites with chemical formula MgxZn1−xFe2O4 (x=0.5, 0.6, 0.7) have been synthesized by co-precipitation technique and then subsequently heated to 800°C in order to investigate structural, thermal and magnetic properties. The samples are characterized by using XRD, FTIR, TGA-DSC, SQUID and Mössbauer spectroscopy techniques. The synergic effect of heat treatment with substitution of Mg2+, results in random variation of lattice parameter (a) and crystallite size (D). FTIR studies revealed the formation of cubic spinel structure. The broadening at octahedral bands for compositions x=0.6 and 0.7 attributes to distribution of ferrite particles of different sizes in these samples. The characteristic feature of hysteresis loops reflects the nature of ferrite particles in the state of superparamagnetism. The saturation magnetization at room temperature has been reported for composition x=0.7 is 44.03emu/g. The variation of coercivity is due to variation in magnetic anisotropy which is predominately affected by the exchange interactions arising from the nature of nanoparticles. The blocking temperatures are in the range of 10–30K and their variation is in the line of change in magnetocrystalline anisotropy but not due to variation in crystallite sizes. The Zeeman splitting at tetrahedral (A) and octahedral (B) sites for composition x=0.6 is expected due to increase in size of core of the nanoparticles/or increasing of magnetocrystalline anisotropy. The range of isomer shift values and quadruple splitting values are evident for the presence of Fe3+ ions and the absence of Fe2+ ions in the present systems. The present ferrite nanoparticles in the superparamagnetic state are the potential candidates for biomedical applications like cancer treatment through hyperthermia. The results are interpreted in terms of cation redistribution presuming exchange coupling energy variation on magnetocrystalline anisotropy.