Geobacter-associated prophages confer beneficial effect on dissimilatory reduction of Fe(III)oxides

The dissimilatory reduction of Fe(III)oxides driven by Fe(III)-reducing bacteria(FRB)is an important biogeo-chemical process that influences not only iron cycling but also the biogeochemical cycles of carbon,trace metals,nutrients and contaminants.Phages have central roles in modulating the population and activity of FRB,but the mechanism for phage-involved Fe(III)oxide reduction is still unclear.This work used a common FRB,Geobacter soli,to explore the roles and underlying mechanisms of FRB-harboring prophages in the dissimilatory reduction of Fe(III)oxides.Bioinformatic analysis predicted 185 phage-related genes in the G.soli genome,comprising functional prophages that were verified to be induced to form tailed phage particles.Ferrihydrite reduction was facilitated as prophage induction was stimulated and declined as prophage induction was inhibited,which indi-cated a positive role of G.soli-harboring prophages in Fe(III)oxide reduction.A comparison of gene expression and released phage particles in the cells grown with Fe(III)-citrate and ferrihydrite suggested that microbial fer-rihydrite reduction would activate the SOS response and consequently induce the prophages to enter lytic cycles.The prophage-mediated lysis of the subpopulation resulted in an increased release of extracellular DNA and mem-brane vesicles that were conducive to Fe(III)oxide reduction,which might explain the positive role of prophages in ferrihydrite reduction.In summary,our results revealed the functional roles and underlying mechanisms of FRB-associated prophages in facilitating the dissimilatory reduction of Fe(III)oxides,which will advance our understanding of iron cycling in natural ecosystems.

Preparation of hexagonal and amorphous chromium oxyhydroxides by facile hydrolysis of K_xCrO_y

The hydrolysis process and mechanisms of unique as-prepared KCrO2 and K3 CrO4 were systematically investigated. The characterization results of XRD, IR and SEM show that the hydrolysis reaction can be realized at a low reaction temperature of 80 ℃ and a reaction time of 24 h. Moreover, the greyish-green α-CrOOH with a hexagonal plate-like morphology and a large size of 10 μm is formed via the hydrolysis of the single-phase hexagonal KCrO2, while the green sol-gel of amorphous Cr(OH)3 with a lumpy aggregate morphology is generated through the hydrolysis of a cubic K3 CrO4. It is a facile and rapid method to synthesize pure-phase chromium oxyhydroxide via the above hydrolysis.

Reduction of chromium oxides in stainless steel dust

The recovery of metal oxides from stainless steel dust using C（graphite）, SiFe, and Al as reductants was investigated under various conditions. The apparent distribution ratio of Cr（L Cr ′^m/s ） in the recovered metal and residual slag phases was defined as the major performance metric. The results show that the recovery ratio of metals increases as the ratio of CaO ：SiO2 by mass in the residual slag increases to 1.17. The residual content of metals in the slag decreases as the Al2O3 content of the slag is increased from approximately 8wt% to 10wt%. The recovery ratio of Cr increases with increasing L Cr ′^ m/s , and a linear relationship between L Cr ′^m/s and the activity coefficient ratio of CrO in the slag and the recovered metal phase is observed. The combination of C and SiFe or Al as the reducing agents reveals that Si is the more effective coreductant.

Effect of partial pressure of reactive gas on chromium nitride and chromium oxide deposited by arc ion plating

The effects of reactive gas partial pressure on droplet formation, deposition rate and change of preferred orientation of CrN and Cr2O3 coatings were studied. For CrN coatings, as nitrogen partial pressure increases, the number and size of droplets increases, the deposition rate initially increases obviously and then slowly, and the preferred orientation of CrN changes from high-index plane to low-index one. For Cr2O3 coatings, with the increase of oxygen partial pressure, the number and size of droplets decreases, the deposition rate decreases and the (300) becomes the preferred orientation. These differences are ascribed to the formation of CrN (with a lower melting point) and Cr2O3 (with a higher melting point) on the surface of Cr target during the deposition of CrN and Cr2O3. Complete coatings CrN or Cr2O3 film can be formed when reactive gas partial pressure gets up to 0.1 Pa. The optimized N2 partial pressure for CrN deposition is about 0.1?0.2 Pa in order to suppress the formation of droplets and the suitable O2 partial pressure for Cr2O3 deposition is approximately 0.1 Pa for the attempt to prevent the peel of the coating.

Effects of iron oxide on crystallization behavior and spatial distribution of spinel in stainless steel slag

Chromium plays a vital role in stainless steel due to its ability to improve the corrosion resistance of the latter.However,the re-lease of chromium from stainless steel slag(SSS)during SSS stockpiling causes detrimental environmental issues.To prevent chromium pollution,the effects of iron oxide on crystallization behavior and spatial distribution of spinel were investigated in this work.The results revealed that FeO was more conducive to the growth of spinels compared with Fe2O3 and Fe3O4.Spinels were found to be mainly distrib-uted at the top and bottom of slag.The amount of spinel phase at the bottom decreased with the increasing FeO content,while that at the top increased.The average particle size of spinel in the slag with 18wt%FeO content was 12.8μm.Meanwhile,no notable structural changes were observed with a further increase in FeO content.In other words,the spatial distribution of spinel changed when the content of iron oxide varied in the range of 8wt%to 18wt%.Finally,less spinel was found at the bottom of slag with a FeO content of 23wt%.

Evaluation of Acute Chromium (III) Toxicity in Relation to Daphnia Similis

Acute chromium (III) toxicity in relation to Daphnia similis, most appropriate for Brazilian environment has been evaluated. The preliminary toxicity test showed that the median effective concentration was 10 mg/l. After having performed the final test, the immobility percentage was calculated for each concentration in relation to the total number of the used organisms within the chosen pH range. It was shown that the proposed methodology rendered realistic results and the 48-h CE50 value under the test conditions is 3.24 mg/l. The minimum concentration that did not show any toxicity to Daphnia similis was 2.5 mg of chromium (III) per liter. The obtained level is superior to the maximum limit recommended by the Brazilian norms, 0.5 mg/l.

Effect of Atmosphere on Sintering Behavior of Chromium Oxide Materials

The chromium oxide materials were prepared using Cr2O3 micropowder as main starting material, TiO2 micropowder as sintering aid, polyvinyl alcohol as binder, by a series of processes such as slurrying, spraying granulation, machine moulding and cold isostatic pressing, and firing at 1 500 ℃ for 3 h in air （ oxygen partial pressure was 2. 1× 10^4 Pa ）, industrial nitrogen （ oxygen partial pressure was 1×10^3 Pa ） , pure nitrogen （ oxygen partial pressure was 10 Pa） , high purity nitrogen （ oxygen partial pressure was 0.1 Pa ） , and carbon cake embedded atmosphere （ oxygen partial pressure wtas 2.3×10-12 Pa ）. Effects of oxygen partial pressures on the sintering behavior of Cr2 O3 materials were investiga- ted. The results show that （ 1 ） for 3 wt% TiO2-doped specimeas, there is a substantial dependence of sintering on oxygen partial pressure （0. 1 Pa - 2. 1 ×10^4 Pa ） , and the bulk density increases and apparent porosity decreases with oxygen partial pressure decreasing; （2） even if the oxygen partial pressure is 0. 1 Pa, the specimen without TiO2 cannot reach densification sintering; （3） under very low oxygen partial pressure of carbon embedded atmosphere, Cr2O3 materials containing TiO2 or not can attain denzification.

Preparation and Characterization of Plasma-Sprayed Ultrafine Chromium Oxide Coatings

Ultrafine chromium oxide coatings were prepared by plasma spraying with ultrafine feedstock. Processing parameters of plasma spraying were optimized. Optical microscope （OM） was used to observe the microstructure of the ultrafine chromium oxide coatings. Scanning electron microscopy （SEM） was used to observe the morphology and particle size of ultrafine powder feedstock as well as to examine the microstructure of the chromium oxide coating. In addition, hardness and bonding strength of the ultrafine chromium oxide coatings were measured. The results showed that the optimized plasma spraying parameters were suitable for ultrafine chromium oxide coating and the properties and microstructure of the optimized ultrafine chromium oxide coating were superior compared to conventional chromium oxide wear resistant coatings.

Effect of Chromium Powder on Sintering Property of Chrome Oxide Materials

The specimens were prepared using Cr2O3 micropowder, TiO2 micropowder and chromium powder as starting materials, PVA as binder, after spraying granulation and cold isostatic pressing, firing at 1 450 ℃ for 3 h in standard nitrogen and oxygen control atmosphere （ oxygen partial pressure was 1 010 Pa and 10. 1 Pa, respectively）. Effects of chromium powder （ mass percent were 0, 0. 5% , 1.0% , 1.5% and 2.0% , respectively） on sintering behaviors of Cr2O3 materials were researched. The results show that： adding 0. 5% chromium powder can obviously decrease the oxygen partial pressure in the specimens. Meanwhile, because the expansion caused by the oxidation reaction is small, Cr2O3 materials could realize the densifieation sintering under 1 010 Pa and 10. 1 Pa of oxygen partial pressure. The chromium powder addition in Cr2O3 materials shouldn＇t be excessive, otherwise, the expansion reaction occupies a dominant position, which deteriorates the properties of the materials.

The Electrode for Potentiometric Determinаtion of Chromium (III, VI) in Wаter Solutions

The possibility of determining of chromium (III, VI) ions was investigated in this paper. It is shown that the electrode on а basis of heаzlewoodite has high selectivity to chromium (III) ions. Also the stability constants of complexes, forming in system “Cr3+-Mohr’s salt-Ca(OH)2-PVA ÷ PAA” were determined by potentiometric titration with ion-selective electrode.

Synthesis, characterization of a multi-component metal oxide (Al_0.88Fe_0.67Zn_0.28O₃) and elimination of As (III) from aqueous solution.

The multi-component oxide (Al0.88Fe0.67Zn0.28O3)) surface (abbreviated as MCOS) was prepared to optimize the effectiveness of the elimination of As (III) from aqueous solution. The oxide surface was synthe-sized by co-precipitation method using corresponding metal carbonates. It was characterized by XRD, TGA and DSC. The surface morphology of MCOS was observed in SEM and the elemental analysis was accomplished by EDX. The composition of Al2O3, Fe2O3 & ZnO was 23.6, 39.9 and 20.6 wt% respectively in XRF analysis. The specific surface area was found 389.85 m2 g-1. Batch experiments were performed to remove As (III) from aqueous solution considering various parameters such as effect of pH, contact time, initial arsenic concentration, temperature and sor-bent dosage. The maximum sorption capacity of the surface was almost steady from pH 4 to pH 9. Kinetic study shows that As (III) sorption is following second order rate equation with the rate constant of 80×10-2 g mg-1 min-1 at room temperature and this rate was increased with increasing temperature which indicates the sorption was endothermic process. The free energy change, ΔGo was negative which proves that the sorption was spontaneous and thermodynamically favorable. Sorption isotherm was interpreted by Langmuir equation and the maximum sorption capacity of oxide monolayer was 13×10-2 mg g-1.

Periodate Oxidation of a Ternary Complex of Nitrilotriacetatochromium(III) Involving ß-Alanine as Co-Ligand

The kinetics of the periodate oxidation of chromium(III)-complex, [CrIII(NTA)(Ala)(H2O)]-(NTA = Nitrilotriacetate and Ala = ß-alanine) to Cr(VI) have been carried out for the temperature range 15°C - 35°C under pseudo-first order conditions, >>?[complex]. Reaction obeyed first order dependence with respect to and [Cr(III)], and the rate of reaction increases with increasing of pH for the range 3.40 - 4.45. Experimentally, the mechanism of this reaction is found to be consistent with the rate law in which the hydroxo species, [CrIII(NTA)(Ala)(OH)]2- is considerably much more reactive than their conjugate acid. ΔH* and ΔS* have been calculated. It is proposed that electron transfer occurs through an inner-sphere mechanism via coordination of to chromium(III).

Removal of Chromium(III) from the Waste Solution of an Indian Tannery by Amberlite IR 120 Resin

The extraction of chromium(III) from a model waste solution and also from a waste solution of an Indian tannery with Amberlite IR 120 resin is described, and the performance of this resin is compared with other similar resins. The parameters that were optimized include effect of mixing time, pH, loading and elution behaviours of chromium(III) for this resin. Sorption of chromium(III) on Amberlite IR 120 followed Freundlich isotherm and Langmuir isotherm model, and the maximum sorption capacity was determined to be 142.86 mg Cr(III)/g of the resin. Higher Freundlich constant (Kf) values (6.30 and 13.46 for aqueous feed of 500 and 1000 ppm Cr(III)) indicated strong chemical interaction through ion exchange mechanism of the metal ion with the resin. The kinetic data showed good fit to the Lagergren first order model for extraction of chromium(III). Desorption of chromium(III) from the loaded resin increased with the increase in concentration of eluent (5-20% H2SO4). With 20% (v/v) sulphuric acid solution 94% chromium(III) was eluted in three stages. Elution of the Cr(III) in the column experiments was however, found to be lower (82%) than that of the shake flask data. In case of Indian tannery’s waste solution, it was observed that almost total chromium was extracted in four stages with Amberlite IR 120.

Trace amount of chromium（III） in waste water measured by extraction spectrophometry in H2CrO6-n-CsH11OH system

A novel, simple, rapid, economic and hypersensitive method of measuring Cr3＋ is described in this paper. Cr3＋ could be oxidated to H2CrO6, which is extracted by n-C5H11OH, so a trace amount of chromium is measured directly by spectrometers, Sandra sensitivity is S=6.40×10^-3 ug.cm-2.

Finite Element Analysis of Large Size Chromium Oxide Green Bodies During Firing

To prevent dense chromium oxide covers from cracking during firing,such as internal cracking,surface cracking and fracture,the firing process of dense chromium oxide products was simulated,and the performance parameters at several specific temperatures before and after densification of chromium oxide green bodies were tested.The temperature difference and the stress difference of chromium oxide green bodies were calculated by Finite Element Software at heating and cooling rates of 10,20,30 and 40℃·h^(-1),respectively.The results show that large temperature difference and thermal stress difference are the main causes of internal cracking,surface cracking and fracture of the brick.Suitable heating rates reduce or avoid internal cracking of the brick.When the heating rate is 30℃·h^(-1) below 1450℃and 10℃·h^(-1) above 1450℃,the temperature difference and the thermal stress difference in the brick are below 4℃and 4 MPa,respectively,and there is no internal crack in the brick after firing.The initial cooling stage is the key stage that causes cracking or fracture of bricks.When the cooling rate is 20℃·h^(-1) above 1450℃,the thermal stress difference in the brick is less than 4 MPa,which can significantly reduce the surface cracks and fracture of the brick.

Use of Chromium Oxide and Alkane Indicator Methods for Determination of Feed Intake for Grazing Sheep

This experiment was carried out to determine feed intake and digestibility of grazing sheep on pasture. A total of 14 animals randomly divided into two groups with seven animals each group were used in the experiment. Digestibility of pastures was determined using two types of markers-alkane （C32-C36） and chromium oxide. Dry matter intake （DMI） was 717.22 g/d based on chromium oxide method in the experiment, while according to alkane method, DMI was 965.93 g/d and 1,051.07 g/d for C32 and C36, respectively. In conclusion, pastures met 74%-81% of crude protein （CP） and 57%-61% of energy requirements of lambs grazing on Yuzuncu Yil University pasture, who are mid-quality and 4-7 month-old with a 275 g/d expected daily gain. It was calculated that when 628-693 g/d of barley is given, both CP and metabolizable energy （ME） requirements of animals can be met.

Kinetics and Mechanism of Interaction between Chromium(III) and Ethylenediaminetetra-3-Propinate in Aqueous Acidic Media

The kinetics of the formation of 1:1 complex of chromium(III) with ethylenediaminetetra-3-propinate (EDTP) was followed spectrophotometrically at lmax = 557 nm. The reaction was found to be first order in chromium(III) and was accelerated by EDTP. Increasing the pH from 3.3 to 4.7 accelerated the reaction rate, the reaction rate was retarded by increasing ionic strength and dielectric constant of the reaction medium. A mechanism was suggested to account for the results obtained which involves ion pair formation between the various species of the reactants. Values of the activation parameters obtained indicate an associative mechanism.

Comparative Study of Removal of Hexavalent Chromium from Water Using Metal Oxide Nanoparticles

Hexavalent chromium is one of the important heavy metals found in water and wastewater. The hexavalent form of chromium is considered to be a human carcinogen because of its mutagenic and carcinogenic properties. This work has focused on the comparison of copper oxide nanoparticles and aluminium oxide nanoparticles for the removal of chromium(VI) from water. The cooper oxide nanoparticles (CuNP) and aluminium oxide nanoparticles (AlNP) were synthesised by sol gel method. Both the adsorbents were evaluated for the adsorption capacity using Langmuir and Freundlich adsorption model. The CuNP and AlNP were characterized for X-ray diffraction and SEM. The study indicated that the AlNP showed better removal as compared to CuNP and can be further explored as potential adsorbent for hexavalent chromium removal.

THE SELECTIVE OXIDATION OF ALCOHOLS-STUDIES ON THE SYNTHESIS AND PROPERTIES OF HEXAHYDROPYRIDINE CHROMIUM TRIOXIDE HYDROCHLORIDE

A new Cr(Vl)complex,hexahydropyridine chromium trioxide hydrochloride is developed.Its behavior and seiectivity on alcohols are investugated

Fabrication of graphene oxide decorated with poly(dimethyl amino ethyl methacrylate) brush for efficient Cr(Ⅵ) adsorption from aqueous solution

Confronting the severe health threats and environmental impacts of Cr(Ⅵ) in aquatic environments demands innovative and effective remediation approaches. In this study, Graphene oxide(GO)-decorated poly(dimethyl amino ethyl methacrylate)(PDMAEMA) brush nanocomposites(GOP1, GOP2, GOP3, and GOP4) were fabricated using atom transfer radical polymerization(ATRP) by the “graft from” method.The resulting nanocomposites were utilized for removing Cr(Ⅵ) with good adsorption performance due to the electrostatic interaction of protonated nitrogen groups in the brush chains with negatively charged particles in the solution. The kinetic model of pseudo-second-order best represented the contaminants' adsorption characteristics. The Weber-Morris model further indicated that surface adsorption and intraparticle diffusion mechanisms primarily controlled the adsorption procedure. Additionally, the Langmuir and Temkin isotherm models were found to most accurately represent the adsorption characteristics of the pollutants on the nanocomposites, and GOP4 can achieve the maximum adsorption capacity of 164.4 mg·g^(-1). The adsorbents' capacity maintains above 85% after five cycles of adsorption-desorption. The nanocomposites in this study demonstrate promising potential for eliminating Cr(Ⅵ) from aqueous solutions.