Stable Cr Research Articles

Abstract CT157: Phase 1 trial of MEK1 inhibitor E6201 plus dabrafenib in patients (pts) with BRAF V600-mutated metastatic melanoma (MM) with central nervous system (CNS) metastases (mets)

Abstract Background: The prognosis of patients with MM with CNS mets is poor. E6201 is an intravenous (IV) MEK inhibitor with activity against BRAF V600-mutated MM cell lines, including MAPK resistance alteration. A previous phase I trial demonstrated activity of E6201 in BRAF V600E mutated MM with a Maximal Tolerated Dose of 320mg/m2 given IV once a week x 3 weeks q 28 days. 2/23 (8.7%) of patients had a PR, 8/23 (34.8%) had SD. Two patients with MM and brain mets achieved near-CR which led to preclinical studies that demonstrated E6201 is unaffected by P-gp and BCRP transport and achieved higher brain to blood concentration (266%).In this trial, patients with BRAF mutation + MM with brain mets, single agent E6201 given at 320mg/m2 twice weekly x 3 weeks q 28 days was determined to be safe. One patient had CNS SD and a PR in lung mets, and a second patient achieved CNS stable disease and CR in a leg melanotic lesion. The drug was well-tolerated with one reversible AE thrombocytopenia (Gr 2). The final review showed intracranial response of SD in 2/4 (50%) patients and systemic SD in 3/4 (75%) patients. Methods: We are currently accruing to the dose escalation cohort of E6201 with dabrafenib 150 mg twice daily orally (n=up to 22 evaluable patients). E6201 is administered IV at 320mg/m2 twice weekly for 3 weeks every 28 days. Patients must have stage IV melanoma with BRAF mutation with at least one active lesion in the brain. Prior local therapy is allowed if done at least 3 weeks prior to cycle 1. Participants must be on a stable dose of steroids for at least 7 days and have an ECOG <!–=2. The study allows one prior BRAF/MEK inhibitor therapy. The primary objectives are to determine the MTD of E6201 when combined with dabrafenib and the response rate of brain mets. The secondary objectives include duration of response, extracranial response, progression free survival, overall survival, and impact of BRAF mutation subtype and safety of the combination. Clinicaltrials.gov: NCT05388877

Rapid determination of chromium species in environmental waters using a diol-bonded polymer-stationary column under water-rich conditions coupled with ICPMS.

Chromium speciation analysis in environmental water is of great significance for the monitoring of water pollution and assessing its influences on human health. This study proposes a rapid analytical approach for the simultaneous determination of Cr(VI) and Cr(III) in environmental waters by hydrophilic interaction chromatography (HILIC) coupled with ICPMS under a water-rich condition. 2,6-Pyridinedicarboxylic acid (PDCA) was used to unify Cr(III) species in various chemical forms into a stable Cr(III)-PDCA anion complex and then separated from Cr(VI) oxyanion on a diol-bonded polymer-based HILIC column. An aqueous mobile phase containing 50mmol L-1 ammonium acetate (pH 7.0), 2mmol L-1 PDCA, and 4% acetonitrile successfully separates chromium species as well as chloride ions. In addition, our method elutes Cr(VI) preferentially over Cr(III)-PDCA, enabling rapid determination of Cr(VI), and both chromium species were analyzed within 6.2min. The detection limits of 0.19μg L-1 for Cr(VI) and 0.35μg L-1 for Cr(III) at m/z 52 under He collision mode are comparable to or better than the conventional ion exchange chromatography-ICPMS methods, and quantitative recovery was obtained from spike-recovery tests on river water samples containing various levels of matrix. Optimization experiments of the HPLC conditions indicate that the retentions of Cr(VI) and Cr(III)-PDCA are characterized by electrostatic and nonpolar interactions, respectively. The retention behavior of inorganic anions and cations in water-rich conditions observed in this study will provide new insights into the separation mechanism in polymer-based HILIC columns, which has been poorly understood.

Highly stable chiral Cr(iii)-based metal–organic frameworks for enantioadsorption separation of aromatic alcohols

Highly stable Cr-HMOFs Cr-HMOF-1 and Cr-HMOF-2 were synthesized for the first time directly using enantiomerically pure chiral ligands, showing excellent enantioselective separation performance for aromatic alcohol racemates.

Effect of Minor Mo Addition on Microstructure and Corrosion Resistance of High-Velocity Air Fuel-Sprayed Fe-Based Amorphous Coatings

In this work, Fe64Nb3B17Si6Cr6Ni4 and Fe60Nb3B17Si6Cr6Ni4Mo4 (at. %) coatings were prepared with a high-velocity air fuel spraying method, and the effects of minor Mo addition on the microstructure, glass formation, and corrosion resistance of the coating were studied. It was found that the Mo addition improves the glass-forming ability of the alloy and a fully amorphous structure with a higher compactness was obtained in the Mo-containing coating. The thermal stability of the coating is enhanced by Mo addition and the onset crystallization temperature was increased by 20 K. In addition, the Mo-containing amorphous coating exhibited higher corrosion resistance than the Mo-free coating. The superior corrosion resistance can be attributed to the increased proportion of protective, stable Cr, Nb, and Mo oxides in the passive film and fewer defects of the Mo-containing coating.

Superior reduction and immobilization of Cr(VI) in soil utilizing sulfide nanoscale zero-valent iron supported by phosphoric acid-modified biochar: Efficiency and mechanism investigation

A novel strategy was proposed to remediate Cr(VI)-contaminated soil via phosphoric acid-modified biochar supported sulfide nanoscale zero-valent iron (SnZVI@PBC). Results of characterizations revealed that FeSX shell existed in outer layer of nZVI to prevent its oxidation after sulfidation modification, and SnZVI was effectively dispersed owing to the support of PBC, accelerating the electron transport for Cr(VI) reduction. The SnZVI@PBC presented pH-dependence and fast capture for Cr(VI) with outstanding binding amount of 335.55 mg/g. More importantly, the Cr(VI) content declined from 1300.75 to 223.30 mg/kg with conversion into stable Cr(III) in soil after 42 d of remediation with 2.0 % SnZVI@PBC under 60 % moisture content. Furthermore, leaching experiments showed that SnZVI@PBC could effectively immobilize Cr(VI), decreasing its migration and harmful risks to plants and human. Particularly, the fractions of exchangeable and carbonate-bound Cr decreased by 96.77 % and 83.60 %, which transformed to relatively stable fractions. Interestingly, the presence of humic acid, and the freezing-thawing/wetting-drying process promoted the immobilization performance of SnZVI@PBC for Cr(VI). SnZVI@PBC could alleviate the migration and poisonousness of Cr(VI) in soil primarily via reduction, co-precipitation, pore filling, and electrostatic attraction. Overall, SnZVI@PBC could be considered as a feasible amendment with superior reducing capacity and immobilization performance for Cr(VI)-contaminated soil.

Biochar derived from coffee grounds with molybdenum disulfide composites for Cr (VI) removal from wastewater

Discharging pollutants containing toxic metal ions has become a global problem, and improper disposal of coffee grounds can also cause environmental pollution. In this work, 1T-MoS2@STC (Solvothermal Carbonization, STC) was prepared from coffee grounds and molybdenum disulfide by a one-step solvothermal method that is simple in operation, low in energy consumption and low in cost, which possesses efficient adsorption of Cr (VI) in wastewater. The 1T-MoS2@STC was characterized by SEM, TEM, XRD, XPS, Zeta potential, FTIR, and BET analyses. The results showed that MoS2 was successfully loaded on coffee grounds. According to the pseudo-second order (R2 = 0.99) kinetics model, chemisorption was the main cause of adsorption. The adsorption process followed the Langmuir (R2 = 0.99) isothermal model, and the maximum adsorption capacity was 795.17 mg/g. The adsorption mechanism can be attributed to electrostatic interaction, redox reaction between Cr (VI) and active sites, and chelation between Cr (III) and hydroxyl. When 1T-MoS2@STC was applied to the treatment of actual water samples, the removal rate was also maintained at a high level (90%). In addition, 1T-MoS2@STC can maintain long-term stability (90 days) and low leaching of molybdenum (<3 mg/L) in wastewater. Therefore, in the treatment of chromium-containing wastewater, the 1T-MoS2@STC composite material simultaneously exhibited significant adsorption capacity, high interference resistance, stability and low leaching rate. This study provides a new efficient and stable Cr (VI) adsorbent and promotes the practical application of MoS2 biomass derivatives composites in water purification.

Front Cover: The Best of Both Worlds: Combining the Power of MICs and WCAs To Generate Stable and Crystalline CrI‐Tetracarbonyl Complexes with π‐Accepting Ligands (Chem. Eur. J. 50/2023)

Front Cover: The Best of Both Worlds: Combining the Power of MICs and WCAs To Generate Stable and Crystalline Cr^I‐Tetracarbonyl Complexes with <i>π</i>‐Accepting Ligands (Chem. Eur. J. 50/2023)

#5026 ESTIMATED PROXIMAL TUBULE FLUID PHOSPHATE CONCENTRATION AS AN ELEMENT OF DECREASED RENAL FUNCTION IN PATIENTS UNDERGOING UNILATERAL NEPHRECTOMY

Abstract Background and Aims Patients with chronic renal failure (CRF) develop early alterations in mineral metabolism called Chronic Kidney Diseases Mineral Bone Disorders (CKD-MBD), detectable with the available markers (PTH, Ca, Ps) only in the most advanced stages of disease. Recent evidence suggests that the early development of CKD-MBD is related to the nutritional phosphorus intake and the reduction of the number of nephrons (renal functional reserve). Infact with the reduction in the nephrons number, compensation systems must be activated for the maintenance of the phosphoric balance with an increase in urinary phosphate and in the concentration of phosphorus in the single nephron (ePTFp). Therefore, the measurement of ePTFp has been proposed as a new early marker of CKD-MBD and effective renal functional reserve. Threshold values of ePTFp (2.2 mg/dl) have been identified to indicate patients with reduced renal functional reserve and therefore at increased risk of progression of renal damage. The measurement of residual renal function with ePTFp may be a useful parameter to be evaluated in patients who undergo unilateral nephrectomy due to renal neoplasia. In fact, post-nephrectomy some patients have a high reduction of the renal function not identified by preoperative GFR assessment or other risk factors. In these patients, ePTFp could represent a measure of pre nephrectomy kidney functional reserve and thus indicate the risk of reduce renal function after nephrectomy. The aim of the study was to evaluate the relationship between pre-operative ePTFp and renal function after nephrectomy. Methods This is a transversal monocentric observational study. From January 2022 to November 2022, we enrolled patients diagnosed with renal cell carcinoma for which has been indicated unilateral nephrectomy surgery. In all patients we evaluated pre nephrectomy and three months after surgery, renal function, and ePTFP with the formula [ePTFp = (Phosphaturia / creati-ninuria) x creatininemia x 3,33]. 30 subjects with normal renal function (eGFR 100±10 ml/min, no proteinuria) were evaluated for the ePTFp reference values. Results We evaluated 13 patients: age 57.5 ± 13.6; Cr 1.48±0.7 mg/dl; eGFR 58.5 ± 23.3, mil/min; Pi, mg/dl 3.2± 0.6; Ca 9.9± 0.6 mg/dl,PTH 58,8± 41 pg/ml FA 176,7± 108 IU/L, proteinuria 500±150 mg 24H. Compared to the control population (GFR 100 ml/min) the 24-hour phosphaturia was no different while ePTFp was increased 2.1± 0.9 vs 1.2±0.2 mg/dl; p: 0.05. In the post-nephrectomy assessment, creatinine and GFR were stable (Cr 1.48±0.7 vs 1.5 ±0.7 mg/dl; p: n.s; eGFR 58.5 ± 23.3, vs 56.5 ± 22.3, mil/min; p: n.s), while ePTFp was increased (ePTFp pre 2.1± 0.9 vs ePTFp post 3.3± 2.7; p&amp;lt;0.01). Patients with pre-nephrectomy ePTFP ≥ 2.2 mg/dl (n. 6, eGFR 56.5 ± 20.3, proteinuria 550±100 mg/24h) had a greater renal function reduction post nephrectomy (mean GFR delta -9.5±2 ml/min) respect to patients with pre-nephrectomy ePTFP &amp;lt;2.2 mg/dl (n. 7, eGFR 59.7 ± 24.3, proteinuria 500±200 mg/24h; mean GFR delta -0.5±2 ml/min; p: 0.05). In all the population there was direct correlation between ePTFp and the reduction of GFR post nephrectomy (r: 0.667; p: 0.05). Conclusion In our patients ePTFp was higher than the control group and correlate with the entity of the GFR reduction post nephrectomy. The group with a preoperatory ePTFp ≥ 2,2 mg/dl had a higher post nephrectomy GFR reduction. These results suggest that ePTFp identify the pre nephrectomy kidney functional reserve. In particular and ePTFp higher than limits highlighted in the literature (2.2 mg/dl) pre nephrectomy identify a greater risk of kidney function reduction post nephrectomy. ePTFp may be proposed as a parameter to identify patients with higher risk of decreased renal function post nephrectomy.

Thermal-induced decomposition and mechanical properties of AlN/CrN superlattice coating

Here, the thermal-induced decomposition and mechanical properties of AlN/CrN superlattice coating with modulation period of ∼8 nm are investigated in detail. Introduction of CrN template layers stabilizes the cubic growth of AlN layers, where the coherent AlN/CrN coating exhibits the higher hardness value of ∼24.1 GPa than CrN (∼16.9 GPa) and AlN (∼18.5 GPa) monolithic coatings. After thermal exposure, the AlN/CrN coating decomposes into stable body-centered cubic Cr and wurtzite AlN via intermediate phases of hexagonal Cr2N and cubic AlN. Especially, the formation of metastable cubic AlN is observed due to the destruction of coherent interfaces. Meanwhile, the thermal load leads to the grain deformation, which causes the change of AlN and CrN sublayers from the crossover to pinch-off to finally dissociation. The driving force of grain deformation mainly arises from the N-loss of CrN sublayers and the high-density stacking faults formation of AlN sublayers. Furthermore, the occurrence of stacking faults and h-Cr2N phase offset the softening effect caused by the thermal decomposition. Correspondingly, the hardness almost remains unchanged between 900 and 1100 °C.

Two-dimensional Heisenberg model with material-dependent superexchange interactions

The two-dimensional (2D) van der Waals ferromagnetic semiconductors, such as CrI$_3$ and Cr$_2$Ge$_2$Te$_6$, and the 2D ferromagnetic metals, such as Fe$_3$GeTe$_2$ and MnSe$_2$, have been obtained in recent experiments and attracted a lot of attentions. The superexchange interaction has been suggested to dominate the magnetic interactions in these 2D magnetic systems. In the usual theoretical studies, the expression of the 2D Heisenberg models were fixed by hand due to experiences. Here, we propose a method to determine the expression of the 2D Heisenberg models by counting the possible superexchange paths with the density functional theory (DFT) and Wannier function calculations. With this method, we obtain a 2D Heisenberg model with six different nearest-neighbor exchange coupling constants for the 2D ferromagnetic metal Cr$_3$Te$_6$, which is very different for the crystal structure of Cr atoms in Cr$_3$Te$_6$. The calculated Curie temperature Tc = 328 K is close to the Tc = 344 K of 2D Cr$_3$Te$_6$ reported in recent experiment. In addition, we predict two stable 2D ferromagnetic semiconductors Cr$_3$O$_6$ and Mn$_3$O$_6$ sharing the same crystal structure of Cr$_3$Te$_6$. The similar Heisenberg models are obtained for 2D Cr$_3$O$_6$ and Mn$_3$O$_6$, where the calculated Tc is 218 K and 208 K, respectively. Our method offers a general approach to determine the expression of Heisenberg models for these 2D magnetic semiconductors and metals, and builds up a solid basis for further studies.

Evaluation and Assessment of Trivalent and Hexavalent Chromium on Avena sativa and Soil Enzymes.

Chromium (Cr) can exist in several oxidation states, but the two most stable forms-Cr(III) and Cr(VI)-have completely different biochemical characteristics. The aim of the present study was to evaluate how soil contamination with Cr(III) and Cr(VI) in the presence of Na2EDTA affects Avena sativa L. biomass; assess the remediation capacity of Avena sativa L. based on its tolerance index, translocation factor, and chromium accumulation; and investigate how these chromium species affect the soil enzyme activity and physicochemical properties of soil. This study consisted of a pot experiment divided into two groups: non-amended and amended with Na2EDTA. The Cr(III)- and Cr(VI)-contaminated soil samples were prepared in doses of 0, 5, 10, 20, and 40 mg Cr kg-1 d.m. soil. The negative effect of chromium manifested as a decreased biomass of Avena sativa L. (aboveground parts and roots). Cr(VI) proved to be more toxic than Cr(III). The tolerance indices (TI) showed that Avena sativa L. tolerates Cr(III) contamination better than Cr(VI) contamination. The translocation values for Cr(III) were much lower than for Cr(VI). Avena sativa L. proved to be of little use for the phytoextraction of chromium from soil. Dehydrogenases were the enzymes which were the most sensitive to soil contamination with Cr(III) and Cr(VI). Conversely, the catalase level was observed to be the least sensitive. Na2EDTA exacerbated the negative effects of Cr(III) and Cr(VI) on the growth and development of Avena sativa L. and soil enzyme activity.

Highly stable and efficient Cr(VI) immobilization from water by adsorption with the La-substituted ferrihydrite as a naturally-occurring geosorbent in soils

Ferrihydrite (Fh) is a vital geosorbent in the natural environment. Here, Fh materials with lanthanum (La) substituted in varied La/La + Fe ratios were synthesized, and these La-Fh materials were investigated in-depth via adsorption kinetic and isothermal experiments to explore their adsorption performance for chromate [Cr(VI)] in soils. Material properties of La-Fh were further characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FTIR), and X-ray photoelectron spectroscopy (XPS). The results clearly indicate that La3+ can be integrated into the Fh lattice, but the increase in La amount substituted into Fh is slowed down when the La/La + Fe ratio reaches to a larger value. Those La3+ cations that fail to become integrated may either get adsorbed or form a phase of La(OH)3 on La-Fh surfaces. We also find that La substitution reduces the specific surface area (SSA) of La-Fh samples but raises their pHpzc, which hampers La-Fh conversion to hematite and thus increases the chemical stability. These changes are related to the La-Fh structure and surface aspects, but they do not negatively affect the Cr(VI) adsorption efficacy, which can be promoted over a wide pH range to an alkaline pH. For instance, the maximum adsorption amount of Cr(VI) by 20%La-Fh is 30.2 mg/g at a near-neutral pH. However, the entire chromate adsorption processes are affected by H2PO4− and humic acid due to their strong affinities for Cr(VI), but almost not influenced by NO3− and Cl−. All the Cr(VI)-Fh reactions are well described by the fitted adsorption Freundlich model and conform to the pseudo-second-order reaction kinetic equation. The mechanisms which enhance La-Fh's adsorption ability for Cr(VI) are governed by chemical interactions, because La substitution can increase the hydroxyl density on Fh surfaces and thus improve the reactivity of La-Fh towards Cr(VI), leading to an evidently enhanced Cr(VI) immobilization onto La-Fh.

Chromium removal at neutral pHs via electrochemical Cr(VI) reduction and subsequent Cr(III) adsorption with MoS2 nanoflowers-modified graphite felt

The operation performance and stability of electrochemical Cr(VI) reduction are strongly restricted at neutral pHs (e.g., drinking water and groundwater) by the high Cr(VI) oxidation potentials and cathode passivation of Cr(OH)3 precipitates. Herein, we fabricated MoS2 nanoflowers-modified graphite felt (GF-MoS2) to construct the electrochemical apparatus (EA) and adsorption column (AC), attempting to stable and effective Cr(VI) removal at neutral pHs via electrochemical Cr(VI) reduction and subsequent Cr(III) adsorption. In EA with a sequential oxidation-reduction process, Cr(VI)-contaminated influent (5 mg/L) at neutral pHs (6.0–8.0) was oxidized first by anode to generate large amounts of H+ ions via H2O oxidation, decreasing the pH of anode-oxidized influent to ∼2.5 at 2.6 V and 1000 L/m2/h. Subsequently, the acidic anode-oxidized influent was further reduced by GF-MoS2 cathode, promoting significantly Cr(VI) reduction via decreasing Cr(VI) oxidation potentials and alleviating Cr(III) precipitation on cathode. These results enabled the stable and effective operation of GF-MoS2-based EA with almost Cr(VI) reduction to Cr(III). With further assembling GF-MoS2-based AC, Cr(III) species in EA effluent were easily adsorbed or intercepted by GF-MoS2, achieving undetectable Cr species in AC effluent. Combination techniques of GF-MoS2-based electrochemical reduction and adsorption can be an effective approach for remediating Cr(VI)-contaminated water at neutral pHs.

Light stable Cr isotope compositions of mid-ocean ridge basalts: Implications for mantle source composition

Stable isotopes of chromium (Cr) and iron (Fe), both multivalent elements in silicate melts, are valuable proxies of redox conditions in magmatic systems. Partial melting and fractional crystallization have been identified as the dominant fractionation processes for Cr and Fe isotopes in high-temperature reservoirs that can lead to small but detectable isotope variations in igneous rocks. More recently, however, the source mineralogy has been suggested to play an important role, which can ultimately affect the magnitude of Cr and Fe isotopic fractionation during partial melting and thus the Cr and Fe isotopic composition of the originating melt.With the aim to investigate the role of magmatic processes and the source Cr and Fe isotope signatures on the isotope composition of these transition metals in normal mid-ocean ridge basalts (N-MORB), we analyzed 21 well-characterized MORB glasses from the southern East-Pacific Rise, Pacific-Antarctic Ridge and Mid-Atlantic Ridge. The Cr isotope compositions of N-MORB show a narrow range from −0.278 to −0.186 ‰ in δ53/52Cr (i.e., difference of a sample’s 53Cr/52Cr ratio relative to the international reference material NIST SRM979), with an average value of −0.237 ± 0.050 ‰ (2SD; n = 19). As such, the average N-MORB δ53/52Cr value is significantly lower than that of Bulk Silicate Earth of −0.12 ± 0.06 ‰ and the Cr isotope compositions reported for most ocean island basalts ranging from ∼ −0.23 to 0.00 ‰. Iron isotopic compositions of these MORB range from +0.032 to +0.137 ‰ in δ56/54Fe (i.e., difference of a sample’s 56Fe/54Fe ratio relative to the international reference material IRMM014) and are within the range of previously published MORB data. The lack of correlations between N-MORB Cr isotope signatures and indices of magmatic differentiation suggests a negligible control of this process on Cr stable isotopes. Partial melting modeling using pMELTS provides evidence that the significant offset towards lower δ53/52Cr values of N-MORB cannot be produced by decompression partial melting of a lherzolithic source such as the depleted upper mantle alone. Instead, we suggest that the lower δ53/52Cr values of MORB could be linked to intrinsic small-scale 53Cr-depleted pyroxene-rich domains in the upper mantle that influence the melt’s Cr isotopic budget during partial melting.

A new resonance Rayleigh scattering method for phenol based on Cr(III) metal–organic framework probe and 4-aminoantipyrine reaction

Stable Cr(III) metal–organic framework (CrMOF) was prepared and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier infrared spectroscopy (FTIR). It was found that in the presence of potassium periodate (KIO4), phenol (PN) reacted with 4-aminoantipyrine (AAP) to form red quinone imine (QI) product, and a resonance Rayleigh scattering energy transfer (RRS-ET) occurred between the acceptor QI and the donor CrMOF. With the increase of PN concentration, RRS-ET increased, and the RRS intensity at 500 nm decreased. Based on this, a new and simple RRS-ET method for the detection of PN was established, with a detection range of 0.01–0.15 mmol/L and a detection limit (DL) of 0.005 mmol/L. The new RRS-ET method was applied to the determination of PN in water. The relative standard deviation (RSD) was 0.94–7.43%, and the recovery was 97–107%.

Synergistic effect of sulfidated nano zerovalent iron and proton-buffering montmorillonite in reductive immobilization of alkaline Cr(VI)-contaminated soil

Effective remediation of Cr(VI)-contaminated soil with strong alkalinity and high Cr(VI) concentration is a severe challenge. Herein, a proton-buffering montmorillonite-supported sulfidated nano zerovalent iron (nFeS/Fe0@H–Mt) was developed for remediation of alkaline Cr(VI)-contaminated soil. The reductive efficiencies of water-soluble Cr(VI) reached 99.7%, 99.3% and 99.8% in three tested soils with initial concentrations of 439.6, 3307.5 and 4626.7 mg kg−1, respectively, after 15 d of nFeS/Fe0@H–Mt treatment. Further speciation analyses demonstrated most available Cr species (exchangeable and carbonate-bound Cr) were transformed into more stable Cr species. The leachable Cr(VI) and total Cr obtained by toxicity leaching procedures decreased to extremely low levels and maintained long-term stability for 120 d. Such superior reductive immobilization performance of FeS/Fe0@H–Mt was attributed to the synergistic effect of sulfidated nano zerovalent iron and proton-buffering montmorillonite, which induced the coordination of proton donation and electron transfer. The proton-buffering montmorillonite (H–Mt) could prevent the aggregation of nanoparticles and provide protons to accelerate the corrosion of Fe0. In addition, the FeS component improved electron selectivity and facilitated electron transfer of Fe0 to Cr(VI). Our study demonstrated that the coordination of proton donation and electron transfer significantly enhanced the Cr(VI) reduction under the alkaline condition thus leading to effective remediation of alkaline Cr(VI)-contaminated soil.

Electrochemistry and computational mechanisms responsible for the anti-corrosion properties of particular biomolecules on Fe-Cr-Mn alloy in a bio-simulated environment

The electrochemical performance of the Fe–14Cr–8Mn alloy in physiological fluids was investigated in this study. In simulated body solutions, the capacities of the significant biomolecules tyrosine, tryptophan, and l-histidine to inhibit the corrosion of the alloy were also studied. Scanning electron microscopy, energy dispersive X-ray, and X-ray photoelectron spectroscopy were utilized to investigate the surface morphology and elemental composition of the alloy in various simulated solutions. Potentiodynamic polarization and electrochemical impedance spectroscopy data were used to analyze the electrochemical performance of the alloy. The results showed that the amino acids inhibited the corrosion of Fe–14Cr–8Mn alloy in the simulated body solutions, with maximum inhibitory efficiencies of 55%, 63%, and 70.1% for histidine, tyrosine, and tryptophan, respectively. Quantum chemical computations were also conducted and the findings indicated that even in very aggressive solutions, the alloy had a good passivation capacity. The high stability of the alloy was attributed to the formation of a stable Cr protective film on the alloy surface, which was found to depend on the Cr/Fe oxide ratio. The quantum chemical calculations agreed with the electrochemical results. Tyrosine and l-histidine were effective corrosion inhibitors, but tryptophan protected the solutions better.

Corrosion behaviors and protective layer stabilization mechanism of 316 stainless steel in NaCl–KCl–NaF reciprocal salts at high temperatures

Corrosion tests of 316 stainless steel (316SS) in NaCl–KCl–NaF reciprocal salts were conducted at different temperatures. Results showed that the reciprocal salts had perfect compatibility with 316SS even without special treatment, and a stable Cr–O enriched layer was first observed. The stabilization mechanism of chromium oxides in molten salts was explored, where the low oxoacidity was conducive to from the stable chromium oxides. These findings can provide a new direction for the design and corrosion control of molten salts.

Improving high-temperature oxidation behavior by modifying Al and Co content in Al-Co-Cr-Fe-Ni high-entropy alloy

• Oxidation performance of Al-Co-Cr-Fe-Ni system at 1173–1373 K was investigated. • At temperature less than 1273 K, oxidized alloys covered by unstable oxide products. • At temperature higher than 1273 K, oxidation was controlled by Al 2 O 3 or Cr 2 O 3 . • Phase stability beneath oxide layer contributed to oxidation performance • Electron valence concentration affected oxidation behavior of Al-Co-Cr-Fe-Ni system. Composition modification was introduced to improve the oxidation resistance by varying Al and excluding Co from the Al-Co-Cr-Fe-Ni system. Since adjusting the composition shifted the valence electron concentration (VEC) of the alloys, the dual-phase structure of the alloys is expected to be more stable. At low temperatures ( T < 1273 K), the alloys formed mixed oxide products. As oxidation temperature increased, only Cr 2 O 3 or Al 2 O 3 dominated the alloy's surface. Compared to equiatomic AlCoCrFeNi (5-Equi), non-equiatomic AlCoCrFeNi (5-B 40) and four-component AlCrFeNi (4-B 2013) had better oxidation resistance due to monocrystalline-Al 2 O 3 formation. Besides the role of oxide formation, maintaining BCC and B2 phases within the alloys is also beneficial to supporting the stable Cr 2 O 3 or Al 2 O 3 .

Rational construction of micron-sized zero-valent iron/graphene composite for enhanced Cr(VI) removal from aqueous solution

Micron-sized zero-valent iron (mZVI) has been widely used in wastewater treatment. However, the readily formation of FeCr hydroxide passivation layer limited its application in Cr(VI)-containing wastewater treatment. This study reports the rational construction of mZVI/graphene composite (mZVI/G) through a simple and environmental-friendly mechanochemical method. Owing to the extraordinary mechanical strength, graphene nanosheets intertwine with the mZVI particles to form a strong coupled system, leading to the decoupling of water corrosion of Fe0 to two half reactions:1) Fe0 as anode lose electron to produce Fe(II); 2) Graphene nanosheets serve as cathode for hydrogen gas formation involving atomic hydrogen (H*) as intermediate. Compared to carbon nanotubes and activated carbon, graphene nanosheets could stabilize H* due to the electron sponge effect related to large π conjugation system. When mZVI/G was used for Cr(VI) removal, the Cr(VI) species were preferentially adsorbed onto the graphene nanosheets, on which to be reduced to Cr(III) by Fe(II) as well as H*. The mZVI/G achieved a stable Cr(VI) removal capacity for eight consecutive cycles, reaching 102.35 mg·g-1 with the optimal composition, which was 11, 3.12 and 2.17 times higher than that of physical mixed mZVI and GO, mZVI/AC and mZVI/CNT, respectively. Moreover, mZVI/G can achieve efficient removal of Cr(VI) over a wide pH range (3.0 – 9.0). Given the low cost and green chemistry nature, the mechanochemical synthesized mZVI/G was considered to be a promising material for the treatment of Cr(VI) contaminated water.