Typical Cr Research Articles

On-site monitoring and numerical simulation on groundwater flow and pollution plume evolution in a hexavalent-chromium contaminated site

Accurately ascertaining spatiotemporal distribution of pollution plume is critical for evaluating the effectiveness of remediation technologies and environmental risks associated with contaminated sites. This study concentrated on a typical Cr(VI) contaminated smelter being currently remediated using pump-and-treat (PAT) technology. Long-term on-site monitoring data revealed that two highly polluted regions with Cr(VI) concentrations of 162.9 mg/L and 234.5 mg/L existed within the contaminated site, corresponding to previous chromium slag yard and sewage treatment plant, respectively. The PAT technology showed significant removal performance in these highly polluted areas (>160 mg/L) after six months of pumping, ultimately achieving complete removal of the pollutants in these high-pollution areas. Numerical simulation results showed that although the current remediation scheme significantly reduced the Cr(VI) pollution degree, it did not effectively prevent the incursion of the pollution plume into the downstream residential area after 20 years. Additionally, an improved measure involving supplementary pumping wells was proposed, and its remediation effects were quantitatively evaluated. Results indicated that the environmental pollution risk of groundwater downstream could be effectively mitigated by adding pumping wells, resulting in a reduction of the pollution area by 20 % in the case of adding an internal well and 41 % with the addition of external wells after 20 years. The findings obtained in this study will provide an important reference and theoretical guidance for the reliability analysis and design improvement of the PAT remediation project.

Characterization of Red, Pink, Orange, and Purple Gem-Quality Spinel from Four Important Areas

Spinel is a precious stone with a long history. In ancient societies spinel was considered to be an imitation of ruby. With the depletion of ruby mineral resources, gem—grade spinel has attracted more and more attention from consumers. In the last decade, as the popularity of spinel in the global colored gem market continues to rise, plenty of domestic and foreign jewelry brands have launched spinel based jewelry. This study takes spinels from Burma, Vietnam, Sri Lanka, and Tanzania as its research objects and performs a series of tests to obtain their gemological characteristics, spectral characteristics, and chemical composition, with the aim of comparing the differences between spinels with different colors from different areas and exploring the chromogenic mechanism of spinels. Only Burmese red spinels have a typical Cr spectrum. The types of inclusions and the contents of trace elements are the main differences between spinels from the four areas. Burmese spinel is characterized by an octahedral negative crystal filled with dolomite or a mixture of dolomite and calcite. Magnesite is present in Sri Lankan spinels, and dolomite is present in Tanzanian spinel. Dislocation systems and the presence of titanite and talc inclusions are strongly indicative features of Vietnamese spinel. Sri Lankan spinel is characterized by abundant gas–liquid inclusions, such as the beaded healing fissure. The trace element contents of the four areas are different. Burmese spinel is poor in Fe and Zn (Fe: 135.68–3925 ppm; Zn: 338.58–1312 ppm), while Burmese red spinel is rich in Cr (up to 7387 ppm). Vietnamese spinel is rich in Fe (3669.63–19,425 ppm) and poor in Ti content (<89 ppm), while Tanzanian spinel is rich in Zn (5129.96–7008 ppm). High content of Cr + V can lead to the red color in spinel, and the contents of Cr and V change obviously with color. Spinels appear red when Cr content is higher than V, while spinels appear orange when V content is higher than Cr. The red, pink, and orange spinels are colored by Cr3+ and V3+, showing a wide absorption band centered at 400 nm and 550 nm. Fe plays a dominant role in purple spinels. The purple spinel is colored by Fe3+ and Fe2+.

Cr silicate as a prototype for engineering magnetic phases in air-stable two-dimensional transition-metal silicates

Identifying environmentally inert, ferromagnetic two-dimensional (2D) materials with high Curie temperatures (T c) down to the single layer limit has been an obstacle to fundamental studies of 2D magnetism and application of 2D heterostructures to spin-polarized devices. To address this challenge, the growth, structure and magnetic properties of a 2D Cr-silicate single layer on Pt(111) was investigated experimentally and theoretically. The layer was grown by sequentially depositing SiO and Cr followed by annealing in O2. Scanning tunneling microscopy (STM), low-energy electron diffraction (LEED), and low energy electron microscopy all indicated a well-ordered layer that uniformly covered the surface, with STM and LEED indicating that the silicate relaxed to its favored lattice constant. Further experimental characterizations demonstrated that the Cr was nominally 3+ but with a lower electron density than typical trivalent Cr compounds. Comparison with theory identified a Cr2Si2O9 structure that resembles a single layer of a dehydrogenated dioctahedral silicate. Magnetic circular dichroism in x-ray absorption spectroscopy revealed a ferromagnetically ordered state up to at least 80 K. Theoretical analysis revealed that the Cr in a dehydrogenated Cr-silicate/Pt(111) is more oxidized than Cr in freestanding Cr2Si2O9H4 layers. This greater oxidation was found to enhance ferromagnetic coupling and suggests that the magnetism may be tuned by doping. The 2D Cr-silicate is the first member of a broad series of possible layered first-row transition metal silicates with magnetic order; thus, this paper introduces a new platform for investigating 2D ferromagnetism and the development of magnetoelectronic and spintronic devices by stacking 2D atomic layers.

Ecological risk evaluation and sensitivity analysis of heavy metals on soil organisms under human activities in the Tibet Plateau, China.

The Tibetan Plateau (TP), once considered a pristine environment, is now facing increased heavy metal pollution due to human activities, causing unprecedented ecological risks to soil organisms. However, little is known about the sensitivity and tolerance of different soil organisms to heavy metal toxicity in the high-altitude areas of the TP under the background of human activity intensity and future risk control priorities. In this study, we conducted an ecological risk assessment and threshold calculation for 10 heavy metals in soil for typical soil organisms, including Cd, Co, Cr, Cu, Ni, Pb, Zn, Mn, Sb, and Sn, using the species sensitivity distribution (SSD) method in the zone between Ranwu town and Renlongba glacier on the TP. The results revealed that most sampling sites had average levels of Cd, Sb and Ni exceeding their regional soil environmental background values and were the major contaminants. Impressively, the hitherto undeveloped Renlungba Glacier showed relatively high contamination levels of Sb and Ni. From the view of sensitivity differences, the toxicity risks of Cd, Cr, Cu, Ni and Pb were higher for terrestrial plants than for soil invertebrates based on the fitted heavy metal SSD curve trends. In terms of the ecological risk level, the average potentially affected fraction values of Zn and Ni reached 18.5% and 17.0%, respectively, with significant ecological risk at a few sampling sites. In terms of ecological risk thresholds, the Cd concentration at the 5% hazard concentration (HC5) control level was 0.05 mg/kg, which was the heavy metal with the highest risk in this study. Comparing the HC5 values of each heavy metal with the limit values in the current Chinese soil environmental quality standards, the existing administrative policies as a whole lack a powerful prevention of the potential ecological risk posed by heavy metals to soil organisms.

Heavy metals immobilization of ternary geopolymer based on nickel slag, lithium slag and metakaolin

To solve heavy metals leaching problem in the utilization of various industrial solid wastes, this work investigated the heavy metals immobilization of ternary geopolymer prepared by nickel slag (NS), lithium slag (LS), and metakaolin (MK). Compressive strength was measured to determine the optimum and appropriate mix proportions. The leaching characteristics of typical heavy metals (Cu (Ⅱ), Pb (Ⅱ), and Cr (Ⅲ)) in acid, alkali, and salt environments were revealed by Inductively Coupled Plasma (ICP). The heavy metals immobilization mechanism was explored by Mercury Intrusion Porosimetry (MIP), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM) tests. The experimental results show that the group with a mass ratio of NS, LS and MK of 1:1:8 exhibits the highest compressive strength, which reaches 69.1 MPa at 28 d. The ternary geopolymer possesses a desirable capacity for immobilizing inherent heavy metals, where the immobilization rates of Cu and Pb reach 96.69 %, and that of Cr reaches 99.97 %. The leaching concentrations of Cr and Pb increase when the samples are exposed to acidic and alkaline environments. Cu and Pb are mainly physically encapsulated in geopolymer. Additionally, immobilization of Cr mainly involves physical encapsulation and chemical bonding.

Effect of Cutting Fluid on Machined Surface Integrity and Corrosion Property of Nickel Based Superalloy

Superalloy parts place high demands on machined surface integrity and serviceability. In the machining process of superalloys, the cutting fluid is usually used to improve the machining performance. Cutting fluids with cooling and lubrication functions have a relatively large effect on the surface microstructure and residual stress as well. The corrosion damage caused by cutting fluid to the machined surface, during machining and residual, are also worth considering. In this paper, the machining performance of typical binary Ni Cr solid solution, age-hardened, nickel-based superalloy NiCr20TiAl T6, under two commonly used cutting fluids, Blasocut and E709, was analyzed, including cutting performance, surface quality, machining surface corrosion characteristics, and so on. The results showed that the surface residual stress could be improved by adding both cutting fluids compared with the deionized water. Blasocut had better lubrication properties, which could reduce friction and heat production. Pitting holes were found on the polished surface after 45 days with E709 cutting fluid, which was more corrosive than Blasocut. According to this research, a reasonable cutting fluid can be selected to reduce the surface corrosion and improve the service life and performance of parts.

Visible Light Accelerates Cr(III) Release and Oxidation in Cr-Fe Chromite Residues: An Overlooked Risk of Cr(VI) Reoccurrence.

The reduced chromite ore processing residue (rCOPR) deposited in environments is susceptible to surrounding factors and causes reoccurrence of Cr(VI). However, the impact of natural sunlight on the stability of rCOPR is still unexplored. Herein, we investigated the dissolution and transformation behaviors of Cr(III)-Fe(III) hydroxide, a typical Cr(III)-containing component in rCOPR, under visible light. At acidic conditions, the release rate of Cr(III) under illumination markedly increased, up to 7 times higher than that in the dark, yet no Cr(VI) was produced. While at basic conditions, only Cr(VI) was obtained by photo-oxidation, with an oxidation rate of ∼7 times higher than that by δ-MnO2 under dark conditions at pH 10, but no reactive oxygen species was generated. X-ray absorption near-edge structure and density functional theory analyses reveal that coexisting Fe in the solid plays a critical role in the pH-dependent release and transformation of Cr(III), where photogenerated Fe(II) accelerates Cr(III) produced at acidic conditions. Meanwhile, at basic conditions, the production of intermediate Cr(III)-Fe(III) clusters by light leads to the oxidation of Cr(III) into Cr(VI) through the nonradical "metal-to-metal charge transfer" mechanism. Our study provides a new insight into Cr(VI) reoccurrence in rCOPR and helps in predicting its environmental risk in nature.

Coagulation characteristic and mechanism of Fe(III) salts toward typical Cr(III) complexes in wastewater treatment.

Cr(III) complexes are typical pollutants in various industrial wastewater and pose a serious threat to the ecosystem and humans. The coagulation process is commonly used in water treatment plants, yet its removal characteristic and mechanism toward Cr(III) complexes have been rarely reported. In this study, the Fe(III) coagulation process was adopted for the evaluation of Cr(III) complex removal in terms of Cr residual concentration as well as floc size. The results showed that Fe(III) with a dose of 0.8mM removed more than 80% of total Cr for Cr3+ and Cr(III)-acetate, whereas poor removal rate (~ 50%) was obtained for Cr(III)-citrate under the same conditions. Neutral and alkaline conditions facilitated Cr(III)-acetate removal by Fe(III) coagulation, while limited influence was observed for Cr(III)-citrate with various pH. The main removal mechanism of Cr(III)-acetate was precipitation. Cr(III)-citrate elimination largely relied on the adsorption property and sweeping effect of Fe floc. Moreover, Cr(III)-acetate was easier to be separated from a solution since the generated floc sizes were 270μm. Flocs that formed in the Cr(III)-citrate treatment were only 0.3μm, resulting in separation difficulties during the coagulation process. The presence of Cr(III)-acetate and Cr(III)-citrate caused a significant decline in membrane flux. This study provided fundamental knowledge of Fe coagulation treatment in Cr(III) complex-containing wastewater.

Occurrence, leaching behavior, and detoxification of heavy metal Cr in coal gasification slag

Coal gasification slag (CGS) is a type of solid waste produced during coal gasification, in which heavy metals severely restrict its resource utilization. In this work, the mineral occurrence and distribution of typical heavy metal Cr in CGS is investigated. The leaching behavior of Cr under different conditions is studied in detail. Acid leaching–selective oxidation–coprecipitation method is proposed based on the characteristics of Cr in CGS. The detoxification of Cr in CGS is realized, and the detoxification mechanism is clarified. Results show that Cr is highly enriched in CGS. The speciation of Cr is mainly residual fraction (74.47%–86.12%), which is combined with amorphous aluminosilicate. Cr3+ and Cr6+ account for 90.93%–94.82% and 5.18%–9.07% of total Cr, respectively. High acid concentration and high liquid–solid ratio are beneficial to destroy the lattice structure of amorphous aluminosilicate, thus improving the leaching efficiency of Cr, which can reach 97.93% under the optimal conditions. Acid leaching–selective oxidation–coprecipitation method can realize the detoxification of Cr in CGS. Under the optimal conditions, the removal rates of Fe3+ and Cr3+ in the leaching solution are 80.99%–84.79% and 70.58%–71.69%, respectively, while the loss rate of Al3+ is only 1.10%–3.35%. Detoxification slag exists in the form of Fe–Cr coprecipitation (Fe1-xCrxOOH), which can be used for smelting. The detoxification acid leaching solution can be used to prepare inorganic polymer composite coagulant poly-aluminum chloride (PAC). This study can provide theoretical and data guidance for detoxification of heavy metal Cr in CGS and achieve resource utilization of coal gasification solid waste.

Co-catalytic effect of WS2 on the copper slag mediated peroxodisulfate activation for the simultaneous elimination of typical flotation reagent benzotriazole and Cr(VI)

In this study, efficient simultaneous elimination of typical mine pollutants benzotriazole (BTA) and Cr(VI) was achieved by using a copper slag (CS) activated peroxodisulfate (PDS) Fenton system, with WS2 as a co-catalyst. The combined use of these two mine-sourced materials enables excellent pollution removal efficiency. CS can continuously release ferrous ions for the advanced oxidation processes (AOPs), while WS2 as a co-catalyst has key roles in acceleration of the rate-limiting step of Fe3+/Fe2+ conversion and prevention of Fe3+ precipitation. In this process, Fe3+/Fe2+ conversion primarily occurs on the surface of WS2, whereas PDS decomposition and BTA degradation are dominated by homogeneous Fenton reactions. Dissolved Fe2+ has a main role in the activation of PDS and generation of ROS. The contributions of free radicals, singlet oxygen and Fe(IV) in BTA degradation were carefully evaluated. Fe(IV) was identified as the major ROS responsible for degradation of BTA in the CS/WS2/PDS system. This was further confirmed by the Raman spectra and the detection of BTA degradation products formed by the transfer of oxygen atoms. Kinetics calculation showed that Fe(IV) was responsible for 63.4 % of the degradation of BTA. More importantly, water matrix had a low impact on the degradation of BTA due to the high selectivity of Fe(IV). This study provides a new strategy for a cost-effective and efficient decontamination of the environment in mining areas.

Geoenvironment and weathering of silicate minerals in sediments of the Brahmaputra river, India: Implications for heavy metal pollution assessment

We carried out detailed compositional studies on fifteen sediment samples from the Brahmaputra River that were collected in the pre-monsoon period, to obtain the inherent contamination factor. The present study demonstrates that the degrees of metal contamination in the sediments of the Brahmaputra river. Typical metals Fe, Al, Ti, Pb, Zn, Cu, Ni, Co, Mn and Cr, have been evaluated using several parameters like, enrichment factor (EF), contamination factor (CF), geo-accumulation index (Igeo) and pollution load index (PLI). The relative distributions of the contamination are found to be: Al > Fe > Ca > Mg > Ti > Mn > Cr > Cu > Zn > Ni > Pb > Co. The suspended sediments have been found to be moderately contaminated by the elements Cu, Pb, Cr, Mn and Ni. The nature of weathering is estimated using plagioclase index of alteration (PIA), chemical index of alteration (CIA), chemical index of weathering (CIW) and index of compositional variation (ICV). The studied suspended sediment samples indicate an intermediate silicate weathering of adjoins area.

Ab initio study of local structures during cooling of liquid Fe-C and Fe-Cr-C alloys

The cooling process of liquid Fe-C and Fe-Cr-C systems from 2100 K to 1100 K was studied by ab initio molecular dynamics simulations. The evolution of local atomic structure was statistically analyzed by the pair correlation function, structure factor, coordination number, bond angle distribution, and the Honeycutt-Anderson (HA) index as well as the Voronoi index. We found that C atoms tend to be surrounded by metal atoms and the strong chemical bonds of Fe-C and Cr-C make the C-centered clusters more stable than Fe-centered clusters. The two alloy systems are dominated by icosahedral order in the liquid state but show different evolutionary trends of atomic structures during the cooling process. The Fe-C system undergoes a bcc-like crystalline phase transition at 1500 K, while the Fe-Cr-C system can be supercooled to an amorphous state with decreasing disclination density in the polytetrahedral packing. The analyses of clusters indicated that doping Cr can introduce new local topological and chemical orderings and thus renders a better glass-forming ability. Furthermore, to understand the mechanism of carbides precipitation from undercooled liquid of high-carbon chromium bearing steel, we simulated the local structures of several typical Fe and Cr carbides. We identified a close connection in the short-range order between the carbides and metallic liquids, which provides a theoretical basis for the formation of primary carbides.

Bioaccessibility of microplastic-associated heavy metals using an in vitro digestion model and its implications for human health risk assessment.

Microplastics can act as carriers of heavy metals and may enter humans through ingestion and threaten human health. However, the bioaccessibility of heavy metals associated with microplastics and its implications for human health risk assessments are poorly understood. Therefore, in this study, four typical heavy metals (As(V), Cr(VI), Cd(II), and Pb(II)) and one typical microplastic (polyvinyl chloride, PVC) were chosen to estimate the human health risk of microplastic-associated heavy metals by incorporating bioaccessibility. Significant adsorption of heavy metals was observed with the following order for adsorption capacity: Pb(II) > Cr(VI) > Cd(II) > As(V); the efficiencies for desorption of these four heavy metals from PVC microplastics were all below 10%. The Fourier transform infrared spectroscopy results indicated that the functional groups on the surface of the virgin PVC microplastics did not play an important role in the capture process. Heavy metals in both gastric and small intestinal phases were prone to release from PVC microplastics when bioaccessibility was evaluated with the in vitro SBRC (Soluble Bioavailability Research Consortium) digestion model. In addition, Pb(II) bioaccessibility in the gastric phase was significantly higher than those in the other phases, while As(V), Cr(VI), and Cd(II) bioaccessibilities showed the opposite trend. After incorporating bioaccessibility adjustments, the noncarcinogenic hazards and carcinogenic risks determined were lower than those based on total metal contents. The individual hazard quotients (HQ) and carcinogenic risks (CR) for ingestion of these four heavy metals from PVC microplastics were all lower than the threshold values for adults and children. In summary, this study will provide a new view of the human health risks of heavy metals associated with microplastics.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11356-022-20983-8.

An all-in-one photocatalyst: Photocatalytic reduction of Cr(VI) and anchored adsorption of Cr(III) over mesoporous titanium@sulfonated carbon hollow hemispheres

Completely removing chromium (Cr) from contaminated water with simultaneous reduction of Cr(VI) and sequestration of Cr(III) is an efficient strategy to restrain its migration in natural water. Herein, sulfonated carbon hemisphere (Labeled as CHS, Inner diameter: 150 nm) worked as a supporter to hold mesoporous TiO2 (MT) nanoparticles (Diameter: 10 nm), constructing a bifunctional catalyst with photocatalytic activity and adsorption capacity. During a typical Cr removal process, efficient photocatalytic reduction Cr(VI) performed alongside the utter adsorption of the generated Cr(III) on the sulfonated CS by ion exchange for the grafted -SO3H+. The reaction rate constant (k) for removing Cr(VI) by TiO2-C-SO3H is 0.04998 min−1, which is 3.72 times higher than that (0.01342 min−1) unmodified TiO2-C, and 23.68 times and that of MT (0.00223 min−1). No residual Cr was determined in the treated water. The highest removal efficiency was achieved when the mass ratio of carbon and TiO2 hemispheres is 0.62%. Two factors contributing to the exceptional reduction efficiency include improved electron-hole separation efficiency endowed by the CHS conductive framework, sensitive light absorption. Ultimately, the -SO3H+ grafted on CHS can immobilize Cr(III) by ion exchange, performing like a resin, which realizes the total removal of Cr(VI) or Cr(III) and restrains the possible hazardous influence.

Heavy Metals in Soils From Intense Industrial Areas in South China: Spatial Distribution, Source Apportionment, and Risk Assessment

Heavy metal pollution from various industrial activities has raised global concern. The present study collected 71 surface and 67 subsurface soils from the area with intensive industrial activities in South China. The typical heavy metals, including Cd, As, Hg, Cu, Ni, Pb, Zn, and Cr concentrations, were detected for studying their spatial distribution patterns. Sources apportionment and risks were analyzed using geographical information system and combined approach, including principal component analysis (PCA), positive matrix factorization (PMF), and geo-accumulation index. The concentrations of Cd, As, Hg, Cu, Ni, Pb, and Zn (except Cr) were higher than relevant background levels while exhibiting different pollution degrees in surface and subsurface soils. The PMF results showed that agriculture, industry, transportation, and nature were the four primary contributing sources of heavy metals in soils from the study area. In general, anthropogenic activities were the dominant factors, significantly influencing heavy metal distributions in surface and subsurface soils. Health risks of heavy metals in soil to the population via soil inhalation, skin contact, and ingestion indicated the non-carcinogenic and carcinogenic risks were at an unacceptable level. Each exposure route contribution is higher for adults than for children, whereas there is a relatively high risk of cancer for adults than for children. Therefore, increasing attention shall be needed for monitoring the heavy metal pollution in soils in the areas with dramatic economic development, e.g., South China.

Plasma-assisted in-situ preparation of graphene-Ag nanofiltration membranes for efficient removal of heavy metal ions

Graphene-based membranes have been considered as promising separation membranes for water treatments due to their unique two-dimensional confined channels. However, subject to the preparation technology, the effective construction of graphene-based filtration membranes with suitable separation ability on heavy metal ions still face considerable challenges. Herein, we have successfully constructed a kind of graphene-based (reduced graphene oxide, rGO) nanofiltration membranes by adopting a plasma-assisted in-situ photocatalytic reduction method. Graphene oxide-Ag (GO-Ag) composite sheets are prepared firstly and then assembled into membranes by vacuum filtration. With the use of Ag nanoparticles as plasmonic photocatalyst, GO-Ag films can be in-situ reduced, leading to the formation of rGO-based composite membranes. Thanks to the mild in-situ reduction process, the filtration ability on heavy metal ions (Cr(VI), Cr3+, Cu2+ and Pb2+) caused by lamellar structure is well retained in the as-formed rGO-Ag membranes. Especially, when treating the typical toxic Cr(VI) solution, the retention capacity, water flux and stability of rGO-Ag membranes are all improved compared with that of the original GO-Ag ones. In addition, the effectively rejection of Cr(VI) from mixed solutions containing both Cr(VI) and Cr(III) also suggests the good applicability of such rGO-Ag membranes in a complex wastewater system.

Simultaneous removal of typical flotation reagent 8-hydroxyquinoline and Cr(VI) through heterogeneous Fenton-like processes mediated by polydopamine functionalized ATP supported nZVI

The heavy metal and organic pollution caused by mining activities keep attracting attention, thus an economic and efficient treatment for combined pollution is pressing. In this study, the simultaneous removal performance of typical organic flotation reagent 8-hydroxyquinoline (8-HQ) and Cr(VI) was investigated via heterogeneous Fenton process induced by a novel polydopamine (PDA) functionalized attapulgite supported nano sized zero-valent iron (nZVI) composite (PDA/ATP-nZVI). Batch experiments showed that PDA/ATP-nZVI had better catalytic reactivity and reduction ability than both ATP-nZVI and nZVI. Under acidic condition, 96.0% of 8-HQ was degraded accompanied with the 42.5% of total organic carbon (TOC) decrease, while 95.8% of Cr(VI) removal efficiency was accomplished by PDA/ATP-nZVI. PDA not only served as redox mediator in expediting electron transfer, but also acted as electron donor that accelerated transformation from Fe(III) to both dissolved Fe(II) and surface Fe(II), which resulted in the increased degradation of 8-HQ. The synergic removal behavior between 8-HQ and Cr(VI) was discussed and the reaction mechanism in the persulfate (PS)-PDA/ATP-nZVI system was also explored. This study developed a highly efficient heterogeneous catalyst, and demonstrated that the PS-PDA/ATP-nZVI system had a potential for remediation of mine environment polluted by both heavy metals and organic flotation reagents.

Consumer noticeability of performance differences in battery powered devices

AbstractIn U.S. households alone, approximately 1.1 billion devices are powered by disposable, primary (single‐use) batteries. About one‐third of these devices are driven by constant resistance (cR) electronics whereby the performance of these devices is dependent on the load voltage provided by the battery, unlike constant current (cI) and constant power (cP) devices where device performance is regulated electronically to be largely similar throughout the life of the battery and regardless of the load voltage provided by the battery. Performance signals provided by cR devices can include movement (as with motorized toys), vibration (as with toothbrushes and grooming devices), light intensity (as with flashlights), and sound (as with a multitude of devices). In typical cR devices, performance signals will change and decrease as battery load voltage decreases. This exploratory study demonstrated that typical users of cR devices were able to perceive decreasing performance of a variety of cR devices as battery load voltage decreased. Furthermore, data acquired from panelists regarding likelihood of changing batteries due to decreased device performance suggests that consumers were prone to battery changeout at a performance threshold above the electronic/device cutoff in cR devices.Practical applicationsThe results of the present work showed that untrained, naive panelists could determine performance differences in cR devices supplied with varying load voltage and suggests consumers may be willing to sacrifice battery longevity for device performance in devices where the performance varies with the state of battery power supply. These data could provide important guidance to device manufacturers (OEMS; Original Equipment Manufacturers) for design of less variably performing cR devices and to battery manufacturers for design of batteries with higher running voltages. Most importantly, the results of this study suggest that both battery and device manufacturers should focus on balancing between better device performance and longer device‐battery service life for cR devices rather than singular focus on device‐battery service life. Although placed in the United States, the methodology and results could have implications for both battery and cR device design globally.

Assessment of Cr Isotopic Heterogeneities of Volatile-rich Asteroids Based on Multiple Planet Formation Models

Abstract Describing the comprehensive evolutionary scenario for asteroids is key to explaining the various physical processes of the solar system. Bulk-scale carbonaceous chondrites (CCs) possibly record the primordial information associated with the formation processes of their parent bodies. In this study, we tried to estimate the relative formation region of volatile-rich asteroids by utilizing the nucleosynthetic Cr isotopic variation (54Cr/52Cr) in bulk-scale CCs. Numerical calculations were conducted to track the temporal evolution of isotopically different (solar and presolar) dust and 54Cr/52Cr values for mixed materials with disk radius. First, we found that isotopic heterogeneities in CC formation regions were preserved with a weak turbulence setting that increased the timescales of the advection and diffusion in the disk. Second, we assessed the effects of gaps formed by giant planets. Finally, the distance from the injected supernovae and Cr isotopic compositions of the presolar grains were investigated in terms of the estimated formation region of CCs. In our results, a plausible formation region of four types of CCs could be obtained with the supernova from approximately 2 pc and typical Cr isotopic compositions of presolar grains. Among the parent bodies of CCs (i.e., volatile-rich asteroids), B-type asteroids formed in the outermost region, which is inconsistent with the present population, showing that D-type asteroids are generally located beyond most of the C-complex asteroids. Both the initial and present orbits of asteroids might be explained by the scatter attributed to the inward-outward migration of Jupiter and Saturn.

The correlation between chemical effect and segregation behavior in metallic Al liquid

In this work, a study of melt Al1−xMx alloys was carried out by ab initio molecular dynamics (AIMD) simulation within GGA and LDA. Two groups of typical elements Fe, Co, Ni and Cr, V, Ti, showing opposite segregation behaviors in metallic liquid Al, were chosen as the solutes M. The short-range orders (SROs) were analyzed based on the calculation of the static structure factor, pair-correlation function, common neighbor analysis, bond angle distribution function (BADF) and Voronoi polyhedron (VP) analysis. The affinity between unlike species in molten Al1-xMx divides into two groups according to the segregation tendency. The solute atoms with distribution coefficient smaller than 1 (k < 1) prefer to bond with heterogeneous atoms and tend to form medium-range order (MRO) in sharing of common Al atoms, while the solute atoms with distribution coefficient smaller than 1 (k > 1) tend to bond with homogeneous atoms directly. The abundant Voronoi polyhedron (VP) using the solute atom with k < 1 as centered atom is crystal-like cluster (〈0,3,6,0〉 and 〈0,3,6,1〉), whereas that using the solute atom with k > 1 as centered atom is mixed cluster (〈0,2,8,1〉 or 〈0,2,8,2〉). The difference of VP around different solute atoms is mainly caused by the diversity of fraction of different types of bonded pairs of various solute atoms. Our results exhibit that there indeed exist the correlations between the segregation behavior of solutes and the chemical effects in the Al melt. The diffusion of solute elements is not closely related to segregation. This paper also illustrates that the simulations within GGA or LDA yield similar results except for the minor difference. Our work sheds light on the segregation nature of typical solutes from a structural perspective.