Chromium Content Research Articles

Fluxes of Cadmium, Chromium, and Lead Along with Throughfall and Stemflow Vary Among Different Types of Subtropical Forests

The interaction between forests and precipitation plays a crucial role in the material cycling of forest ecosystems. Atmospheric deposition and rainfall leaching promote the transfer of heavy metals to the forest floor, while canopy exchange may potentially slow this process. Therefore, studying heavy metal fluxes and their influencing factors, along with canopy rainfall partitioning, is essential for understanding forest material cycling. We conducted a year-long experiment to examine the dynamics of chromium (Cr), cadmium (Cd), and lead (Pb) concentrations and fluxes in four types of forests (Cunninghamia lanceolata plantations, Castanopsis carlesii plantations, Cas. carlesii natural forests, and Cas. carlesii secondary forests) located in the subtropical regions of southeast China. Results showed that (1) the annual mean concentrations of Cr, Cd, and Pb were 167.6, 13.8, and 6180.5 μg L−1 in the throughfall and 204.7, 28.4, and 2251.1 μg L−1 in the stemflow, respectively, and the annual fluxes of Cr, Cd, and Pb through throughfall were 29.3, 2.4, and 847.7 g ha−1, respectively, and were 1.7, 0.2, and 12.7 g ha−1 through stemflow, respectively; (2) the concentrations of these heavy metals associated with throughfall did not vary between forest types, but their fluxes were highest in Cas. carlesii natural forests; (3) Cr concentration and flux were higher during the rainy than dry seasons, while Cd and Pb concentrations and fluxes showed an opposite trend. Overall, our results indicate that the fluxes of heavy metals along with rainfall partitioning were highest in natural forests and are primarily controlled by meteorological factors, indicating that the conversion of natural forests to other forest types will substantially change the fluxes of heavy metals along with hydrological processes. These results will contribute to a better understanding of the natural fluxes of heavy metals in forest ecosystems and are valuable for sustainable forest management, particularly in the context of forest type transformation.

Evaluating and optimizing metals for kitchen equipment production

This study assesses the mechanical properties and corrosion resistance of three stainless steel grades (316, 201, and 304) used in kitchen equipment manufacturing, emphasizing their performance based on specific metrics. Brinell hardness tests revealed values of 310.13 HB for 316, 286.49 HB for 201, and 276.13 HB for 304. Impact strength and tensile strength tests showed that 316 outperformed the others due to its higher chromium, nickel, and molybdenum content and enhanced mechanical properties from annealing, quenching, and tempering processes. Fatigue strength testing indicated that 316 had the highest endurance strength. Corrosion tests confirmed that all three grades exhibited no corrosion. These results indicate that stainless steel 316 has superior mechanical properties and corrosion resistance, making it an excellent choice for manufacturing durable and reliable kitchen equipment.

Characteristics and Comprehensive Quality Assessment of Heavy Metals in Soil-crop System of High Geological Background Area

Heavy metals （HMs） pollution in agricultural soil-rice systems has attracted worldwide attention as it directly threatens regional ecological security and human health. To understand the heavy metal pollution of agriculture soil and rice in the high geological background areas, a total of 200 paddy soil and rice samples were collected in southeast Chongqing. The concentrations of arsenic （As）, cadmium （Cd）, chromium （Cr）, copper （Cu）, mercury （Hg）, nickel （Ni）, lead （Pb）, and zinc （Zn） in paddy soil and rice were analyzed. The comprehensive impact index （IICQ） was used to evaluate the quality of heavy metals in soil-rice. The results showed that the mean concentrations of As, Cd, Cr, Hg, and Pb in soil were higher than their corresponding background values of Chongqing soil and the average values of Chinese surface soil, indicating the accumulation of HMs enrichment of these metals in the paddy soils. Compared with China's soil environmental quality standard of agricultural land （GB 15618-2018）, only 20.5% of rice samples containing Cd exceeded the national food safety standard （GB 2762-2022）, though the Cd and Hg sample contamination rates of the sampling sites were 82% and 22.5%, respectively. The evaluation results of heavy metal pollution, such as Cd in soil and crops, were quite different. With the increase in soil pH value, the average content of Cd in the soil gradually increased, but the average content of Cd in rice seeds decreased by 0.245 mg·kg-1, and the excess rate of rice seeds decreased by 42.14%. The Cd content in rice seeds was significantly correlated with the Cd ion exchange state and water-soluble state in the soil. The higher the soil pH value, the lower the proportion of bioactive components in the soil, and the pH of the soil was the main factor affecting the safety of rice in the study area. The comprehensive quality evaluation results showed that moderate and severe pollution were the main pollution levels in the study area, but most of the rice seeds were in a clean state, a few were slightly polluted, and none showed mild or above pollution. The basic safety of rice was in the alkaline area with a pH>7.5. In strongly acidic soil with pH<5.5 and below, the excess rate of rice seeds could reach 45%. Moreover, it is recommended to apply quicklime or calcareous soil conditioner to improve soil acidification, reduce the activity of Cd bioactive components, and improve the safety of rice and other agricultural products.

Safety of the use of a microtracer with the feed additive consisting of chromium propionate (KemTRACE™ chromium) for all growing poultry species.

In the context of the FEEDAP opinion on the safety and efficacy of a feed additive consisting of chromium propionate (KemTRACE™ Chromium) of 18 March 2021, the EU Reference Laboratory for feed additives (EURL) was not in a position to recommend the method: proposed by the applicant for official control for the quantification of the organic chromium content in premixtures and feedingstuffs. The applicant subsequently proposed a new method of analyses, incorporating a tracer in the composition of a premix, which has been evaluated by EURL and recommended as official method for the quantification of the organic chromium content in premixtures and feedingstuffs. In view of the above, the Commission asked EFSA to issue a new opinion on the safety and efficacy of chromium proprionate (KemTRACE™ Chromium) as feed additive for all growing poultry species including the newly submitted information by the applicant that involves the use of the microtracer. The present opinion is limited to the assessment of the new information submitted by the applicant in support of safety of the proposed use of the microtracer in the composition of the premix. The FEEDAP Panel concluded that the use of the microtracer in the premixture, at the proposed level of use, does not present a risk for the target species and the consumer. The microtracer should be considered a dermal and respiratory sensitiser. Therefore, any exposure of users to the microtracer via skin or the respiratory tract is considered a risk. The use of the microtracer at proposed conditions of use is safe for the terrestrial environmental compartment, but no conclusion can be made for the groundwater. The addition of the microtracer in the premix/feedingstuffs is not expected to have any impact on the efficacy of the additive, and therefore, the previous conclusion on the efficacy is still valid.

Influence of increasing chromium content on additively manufactured tool steels: Microstructural and mechanical evolution before and after heat treatment

Influence of increasing chromium content on additively manufactured tool steels: Microstructural and mechanical evolution before and after heat treatment

Effects on lethal concentration 50 % hematological parameters and plasma components of Starry flounder, Platichthys stellatus exposed to hexavalent chromium.

Starry flounders (Platichthys stellatus, mean weight 105 ± 14 g, mean total length 20.2 ± 0.7 cm) were exposed to hexavalent chromium concentrations of 0, 5, 10, 20, 40, and 80 mg Cr6 +/L for 96 hours. The half-lethal concentration (LC50) of P. stellatus induced by acute exposure to waterborne hexavalent chromium for 96 hours was found to be 58.84 mg Cr6+/L. In hematological parameters, red blood cell counts (RBCs), hemoglobin and hematocrit were significantly increased (P < 0.05). Major plasma components also changed significantly due to exposure to waterborne hexavalent chromium. Calcium in plasma inorganic components significantly increased, and glucose and cholesterol in plasma organic components also showed significant increases (P < 0.05). Plasma enzyme components such as AST, ALT and ALP were significantly increased (P < 0.05) at high levels of waterborne hexavalent chromium exposure. The results of this study suggest that acute exposure to waterborne hexavalent chromium in P. stellatus affects survival rates, hematological properties and plasma components.

Chromium adsorption using a composite adsorbent of corn waste and bentonite

Chromium, a highly toxic heavy metal, poses significant risks to both human health and environmental quality. Its adsorption in wastewater using low-cost, easily implementable technologies has emerged as a crucial solution for mitigating its harmful impact. This study explores the effectiveness of a composite adsorbent made from bentonite and corn waste for chromium adsorption. Experiments were conducted in a laboratory-scale batch system. The research examined the adsorption kinetics and equilibrium, process optimization, and the mechanisms of chromium adsorption. For optimization, a response surface methodology was applied considering three variables: adsorption time (min), adsorbent dosage (g/L), and initial chromium concentration (mg/L). The findings suggest that the adsorption kinetics fit best with the pseudo-first-order model (R2 = 0.968), and the adsorption equilibrium fits with the Freundlich model (R2 = 0.997). During optimization, the adsorbent dosage emerged as the most critical factor for chromium removal. The optimal operating conditions were determined to be 103 minutes, 29.71 g/L of adsorbent, and an initial chromium concentration of 31.13 mg/L. The results indicate that chromium adsorption is a multifaceted process involving diffusion and subsequent interaction at the surface and edges of the bentonite layers. Chemical analysis, coupled with changes in the FTIR spectrum, suggests an interaction between chromium and the silicon and aluminum components of the bentonite. These findings underscore the potential of the composite adsorbent for effective chromium removal.

Chromium Substitution Extraction Method for Its Recovery from Chromium-Tanned Leather Waste.

The leather industry generates significant amounts of waste, including chromium-tanned leather waste (CTLW), which poses environmental and health hazards due to chromium's potential toxicity. Efficient management of CTLW is crucial for environmental sustainability and resource recovery. Various methods exist for chromium recovery, including physical, chemical, and biological processes, with chemical methods, particularly substitution extraction using organic acids, showing promising results. This study investigates the use of organic acids for the substitution extraction of chromium from CTLS, with a focus on safety by monitoring the concentration of toxic chromium (VI). It was found that oxalic acid (OA) at a temperature of 43.6 °C and a concentration of 1.34% achieved an extraction efficiency of 63.1% while maintaining minimal hydrolysis at 0.70%. This method offers a sustainable and environmentally friendly approach to chromium extraction from CTLW, addressing a critical need in waste management practices.

Monitoring of chrome and nickel contents in agroecosystems of Central Chernozem region of Russia

The research was carried out within the framework of the state agroecological monitoring program. The goal was to conduct an environmental assessment of chromium and nickel content in agroecosystems of the southwestern part of the Central Chernozem region using the example of the Belgorod region. All analytical studies were carried out in an accredited testing laboratory using generally accepted methods. During the research, it was found that the average gross content of chromium and nickel in the arable layer in leached chernozems is 19.8 and 24.5, in typical chernozems – 20.0 and 24.9, in ordinary chernozems – 20.9 and 26.6 mg/kg, respectively. The average content of mobile forms of chromium in the studied soils was in the range of 0.13–0.14, nickel – 0.37–0.41 mg/kg. Exceeding the levels of the approximately permissible amount of nickel and the maximum permissible concentration of mobile forms of these heavy metals in soils was not detected. In the agroecosystems of the Belgorod region, chromium and nickel are mainly supplied with organic fertilizers, but this does not pose a risk for soil contamination and crop production. The highest average chromium content (0.45 mg/kg) was observed in sunflower seeds, and the lowest (0.22 mg/kg) in corn grain. Soybean grain is characterized by an abnormally high nickel content (4.81 mg/kg), and the lowest concentration (0.63 mg/kg) is observed in corn grain.

Spatial-temporal analysis of groundwater well features from neural network prediction of hexavalent chromium concentration

Groundwater monitoring is a crucial part of groundwater remediation that produces data from various strategically placed wells to maintain a water quality standard. Using the United States Department of Energy’s Hanford 100-HRD area well data, recurrent neural networks are trained in the form of one-dimensional Convolutional Neural Networks (CNNs), Long Short Term Memory (LSTM) networks, and Dual-stage Attention-based LSTM (DA-LSTM) networks to reduce monitoring costs and increase data sampling responsiveness that is subject to laboratory analysis delays, with the best network being DA-LSTM achieving an R2 score of 0.82. There is also the provision of novel well relation analysis through two method of explanation coming from SHapley Additive exPlanations (SHAP) and attention mechanisms within DA-LSTM. Extracting feature well importance from these two methods and using target wells as vehicles for pipeline demonstration, it is found that wells 199-D5-160, 199-D4-68, 199-D2-11, 199-D8-94, and 199-D2-10 have had the most year-long impact on Hexavalent Chromium (CrVI) concentration at the target during the testing year, while wells 199-D8-94, 199-D4-95, 199-D8-53, 199-D4-85, and 199-D4-99 are found to be strong candidates affecting target CrVI instantaneous change during a particular timeframe.

Effect of Chromium Concentration on the Microstructure and Magnetic Properties of FeCr Nanostructured Powders Prepared by Mechanical Alloying

Effect of Chromium Concentration on the Microstructure and Magnetic Properties of FeCr Nanostructured Powders Prepared by Mechanical Alloying

Temperature and Cr-Co ratio on Production of Diethyl Ether from Ethanol Dehydration using Cr-Co/γ-Al2O3 Catalyst

The running down of fossil fuels and rising environmental concerns, there is an increasing emphasis on identifying eco-friendly alternative energy sources. Diethyl ether (DEE) is considered one such additive fuel that can replace fossil fuels. In this study, DEE was synthesized through the reaction dehydration of ethanol using γ-alumina catalysts impregnated with chromium and cobalt. The dehydration of ethanol performed in a fixed bed reactor using Cr-Co/γ-Al2O3catalysts loading. The effect of metal ratio of Cr-Co was examined. Catalyst characterization was carried out using XRD, BET, and SEM-EDX analyses. The dehydration reaction was conducted in a fixed-bed reactor at temperatures 100 to 200 ºC, with nitrogen gas flowrates between 200 and 600 mL/min as the carrier gas. The findings revealed that the increase chromium contents, and the temperature were augmenting the diethyl ether yield. And the increase of nitrogen flow rate is slightly increasing the yield of DEE and conversion of ethanol. Copyright © 2024 by Authors, Published by BCREC Publishing Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Design and Optimization of W-Mo-V High-Speed Steel Roll Material and Its Heat-Treatment-Process Parameters Based on Numerical Simulation

W-Mo-V high-speed steel (HSS) is a high-alloy high-carbon steel with a high content of carbon, tungsten, chromium, molybdenum, and vanadium components. This type of high-speed steel has excellent red hardness, wear resistance, and corrosion resistance. In this study, the alloying element ratios were adjusted based on commercial HSS powders. The resulting chemical composition (wt.%) is C 1.9%, W 5.5%, Mo 5.0%, V 5.5%, Cr 4.5%, Si 0.7%, Mn 0.55%, Nb 0.5%, B 0.2%, N 0.06%, and the rest is Fe. This design is distinguished by the inclusion of a high content of molybdenum, vanadium, and trace boron in high-speed steel. When compared to traditional tungsten-based high-speed steel rolls, the addition of these three types of elements effectively improves the wear resistance and red hardness of high-speed steel, thereby increasing the service life of high-speed steel mill-roll covers. JMatPro (version 7.0) simulation software was used to create the composition of W-Mo-V HSS. The phase composition diagrams at various temperatures were examined, as well as the contents of distinct phases within the organization at various temperatures. The influence of austenite content on the martensitic transformation temperature at different temperatures was estimated. The heat treatment parameters for W-Mo-V HSS were optimized. By studying the phase equilibrium of W-Mo-V high-speed steel at different temperatures and drawing CCT diagrams, the starting temperature for the transformation of pearlite to austenite (Ac1 = 796.91 °C) and the ending temperature for the complete dissolution of secondary carbides into austenite (Accm = 819.49 °C) during heating was determined. The changes in carbide content and grain size of W-Mo-V high-speed steel at different tempering temperatures were calculated using JMatPro software. Combined with analysis of Ac1 and Accm temperature points, it was found that the optimal annealing temperatures were 817–827 °C, quenching temperatures were 1150–1160 °C, and tempering temperatures were 550–610 °C. The scanning electron microscopy (SEM) examination of the samples obtained with the aforementioned heat treatment parameters revealed that the martensitic substrate and vanadium carbide grains were finely and evenly scattered, consistent with the simulation results. This suggests that the simulation is a useful reference for guiding actual production.

Isolation and Identification of Chromium-Tolerant Bacteria from Poultry Litter in Dhaka, Bangladesh

Tannery waste, known for its high chromium content, often contaminates chicken feed, accumulating chromium in chickens and their excreted waste. This study aimed to isolate chromium-tolerant bacteria from chicken litter and evaluate their ability to withstand various chromium concentrations. Four bacterial isolates—CM3, CM4, CM5, and CM6 were presumptively identified as Pseudomonas sp., Bacillus sp., Staphylococcus sp., and Bacillus sp., respectively. The isolate CM4 showed the highest tolerance, growing at 800 mg/L concentrations. A subsequent experiment focused on CM4, where growth was measured by absorbance at 600 nm across chromium concentrations from 0 mg/L to 3200 mg/L. The results indicated a significant decrease in growth with increasing chromium levels, with near-complete inhibition at the highest concentrations. This study highlights the potential of chromium-tolerant bacteria from poultry litter for bioremediation, particularly in environments contaminated with this heavy metal. These findings contribute to ongoing efforts to mitigate chromium pollution through microbial interventions. Stam. J. Microbiol. 2024;14(1):18-21

Dependence of wear intensity on the coating material of the hydraulic cylinder of the garbage truck’s sealing plate

The article is dedicated to the study of the influence of the coating material on the wear rate of the hydraulic cylinder of the mechanism of the garbage truck’s sealing plate. By means of a first-order planning of experiment with first-order interaction effects using the Box-Wilson method, an adequate dependence of the wear rate of the hydraulic cylinder of the mechanism of the garbage truck’s sealing plate on the coating material was determined. It is established that according to the Student’s criterion, among the studied factors of influence, the intensity of wear of the hydraulic cylinder of the mechanism of the garbage truck’s sealing plate is most affected by the iron content in the coating, the least – by the chromium content, and the nickel content affects only indirectly in interaction with the iron content. The response surfaces of the goal function – the intensity of wear of the hydraulic cylinder of the mechanism of the garbage truck’s sealing plate and their two-dimensional sections in the planes of the influence parameters are shown, which allow to clearly illustrate the specified dependence of this goal function on individual influence factors. The expediency of conducting further research to determine ways to further improve the wear resistance of the hydraulic cylinder of the mechanism of the garbage truck’s sealing plate is shown

Reconstruction of the Passive Layer of AISI 304 and 316 Steel After Scratching.

Austenitic stainless steels are used widely in many fields due to their good mechanical properties and high resistance to corrosion. This work focuses on the reconstruction of the passive film after scratching. The purpose of the study was to compare changes in the rate of passive layer reconstruction and to discuss the effect of both the type of material and its electrochemical treatment on the reconstruction of the passive layer for two types of stainless steel: 304 and 316. The XPS tests performed indicate a significantly higher Cr/Fe ratio for the samples after the electropolishing process of 1.41-1.88 compared to the as-received samples of 0.82-0.86. After 2-3 min of sputtering the surface with Ar+ ions, a decrease in chromium content can be observed, with a simultaneous increase in nickel content, visible especially for the electropolished samples. A new approach in the conducted research was to scratch the test samples under controlled conditions, then evaluate the dynamics of the passive layer reconstruction using the AFM method, and then confront the obtained results with XPS measurements for the corresponding samples. For the as-received samples (2B finish) and those after surface treatment, regardless of the level of contamination of the electropolishing process bath, the reconstruction time was similar, which was approximately 2 h, although certain differences in the process dynamics were noticeable.

Exploring Metal-Metal Composites: A Study on AA5083 Matrix-Cr Particles Reinforced Composites.

The objective of this study is to develop chromium-reinforced metal-metal composites utilizing an AA5083 aluminum alloy matrix through powder metallurgy while also examining their properties. Samples were produced by incorporating varying quantities of chromium (5%, 10%, and 15% by weight) into the AA5083 matrix. In order to ensure a uniform distribution of chromium particles, the powders were blended in a ball mill and subsequently hot-pressed at 500 °C under 500 MPa for a period of two hours in an argon atmosphere. The resulting samples were subjected to analysis in order to determine the effect of chromium content on the composites, with particular attention being paid to their microstructure, hardness, density, tensile properties, tribological performance and corrosion resistance. The findings demonstrated that an elevated chromium concentration markedly augmented the hardness of the composite, exhibiting a 50% enhancement in the 15 wt.% Cr composite. A 30% reduction in wear loss was observed for the same sample. The A10 sample (10 wt.% Cr) exhibited the greatest corrosion resistance, although this declined in the A15 sample due to increased porosity. Tensile strength increased by up to 10 wt.% Cr before decreasing at 15 wt.% Cr, which was also attributed to porosity. These findings demonstrate that chromium reinforcement enhances the mechanical and tribological performance of AA5083 composites, rendering them suitable for applications requiring high hardness and wear resistance.

Electrospun Carbon Nanofibers Derived from Polyvinyl Alcohol Embedded with Bimetallic Nickle-Chromium Nanoparticles for Sodium Borohydride Dehydrogenation.

Bimetallic NiCr nanoparticles decorated on carbon nanofibers (NiCr@CNFs) were synthesized through electrospinning and investigated as catalysts for hydrogen generation from the dehydrogenation of sodium borohydride (SBH). Four distinct compositions were prepared, with chromium content in the catalysts ranging from 5 to 25 weight percentage (wt%). Comprehensive characterization confirmed the successful formation of bimetallic NiCr@CNFs. Notably, among the compositions, the catalyst containing 20 wt% Cr exhibited the highest efficiency in SBH dehydrogenation. Kinetic studies revealed that hydrogen production followed a first-order reaction with respect to the catalyst quantity. Additionally, the reaction time decreased with increasing temperature. The activation energy (Ea), entropy change (ΔS), and enthalpy change (ΔH) were calculated as 34.27 kJ mol-1, 93.28 J mol·K-1, and 31.71 kJ mol-1, respectively. The improved catalytic performance is attributed to the synergistic interaction between Ni and Cr. This study proposes a promising strategy for the advancement of Ni-based catalysts.

Parametric Optimisation of Wire Electrical Discharge Machining of 15CDV6 HSLA Steel Using Taguchi Method

15CDV6 steel is a high strength bainitic High Strength Low Alloy (HSLA) steel with low concentrations of chromium, molybdenum, and vanadium as the main alloying constituents. This steel is very robust and well-tempered i.e., it has High strength and good toughness. It is used in the manufacture of transformers, electric motors, nuclear reactors, and its application to the aerospace industry for the manufacture of rocket motor cases is immense. Simplifying any process of machining is very difficult, since it basically includes forecasts of machining parameters and working requirements that are unpredictable and extremely non-linear in nature which influence the overall production Quality and costs. A key component of producing novel products, particularly for the automotive and aerospace sectors, is wire electro discharge machining (Wire-EDM). This technology got success and offers unique advantages for specific applications, such as working with hard, super-tough, brittle, or difficult-to-machine materials, producing intricate shapes, or achieving high precision. The high degree of the obtainable accuracy and the fine surface quality makes Wire-EDM valuable. The right selection of the process parameters or input variables is the considered as most important task in Wire Electro Discharge Machining of 15CDV6 HSLA steel material. The present work concentrates on optimisation of various process parameters are Pulse-on Time, Pulse-off Time, Water pressure and sensitivity on work material 15CDV6 HSLA steel, the output responses considered are Material Removal Rate (MRR), Surface Roughness (Ra), and Power Consumption (PC). Taguchi Method technique used on experimental results for optimisation and same results are analysed using Analysis of Variance (ANOVA) for identify percentage contribution of process parameters. This work helps in analysing the suitable process parameters and machining performance for machining of 15CDV6 steel and also reveals the research work area in which maximum research work can be done in future.

Unserpentinized harzburgites of the Voikaro-Synyinsky massif of the Polar Urals as the initial source of chromium for the formation of deposits

The composition and age of unserpentinized harzburgites, which are found in the Voikaro-Synyinsky massif in the form of budins and relict bodies in the fields of olivine-antigorite rocks development, have been studied. The structure, compositions of rocks and minerals, as well as the distribution of rare-earth elements and Sm-Nd absolute dating (≈2330 million years) allow us to consider these unserpentinized harzburgites as fragments of the mantle and the earliest formations among the ultramafic Voikaro-Synyinsky massif. The silicates of these harzburgites are characterized by increased chromium content, which in subsequent different processes turns into chromium spinelide. Based on the data obtained, the resources of chromium mobilized during the transformation of primary ultramafics were evaluated.