Metals Chromium Research Articles

Unusual nanoscale amorphization of metallic chromium interfacing with SiC under high energy irradiation

Layered metal/silicon carbide (SiC) materials systems are becoming increasingly relevant to solve materials challenges in advanced fission and fusion nuclear energy systems, necessitating a deeper understanding of how interfaces between dissimilar materials behave under high energy irradiation. In this work, we use a Cr-SiC bilayer system as a model to study the behavior of such interfaces under high energy ion irradiation (80 MeV Xe26+ ions) at elevated temperatures (∼350 °C). Through high resolution characterization of the interface, we observed the formation of a nanoscale Cr-rich amorphous layer adjacent to crystalline SiC. We explain this phenomenon through a multi-scale computational approach incorporating ballistic mixing simulations, density functional theory calculations, and CALPHAD-based non-equilibrium modeling that shows the localized amorphization of Cr to be driven by the synergistic action of irradiation-induced point defects within Cr and transport of Si and C atoms across the interface. In particular, the accumulation of radiation damage results in the thermodynamic destabilization of the point-defect containing, metastable Cr-Si-C solid solution with respect to an amorphous phase of identical composition. This study advances the understanding of how metal/SiC interfaces behave under irradiation and establishes a modeling framework that can be applied to interfacial systems to understand irradiation-induced amorphization.

Recent Development in Nanoparticle-Assisted Microbial Fuel Cell for Enhanced Reduction of Chromium.

Chromium metal is a potential toxin released by various industries as by products. Reduction of the same costs an ample amount of manpower and wealth. Alternate, economical, efficient, and sustainable form of chromium reduction while generating electricity is a boon that microbial fuel cell (MFC) has provided to man. It paves way for an attractive technique to process hazardous elements. Nature as well as the type of electrode modulates the efficiency of reduction and power production. Many previously published studies have reviewed chromium removal from effluents as well as through MFCs, but utilization of nanoparticle-based MFC for chromium removal has not been exclusively done before. Hence, the objective of the current review is to provide exclusive study on nanoparticle-assisted MFC for chromium reduction. Reputed published data from the past 5years have been studied meticulously to compare the best outcomes of MFC in chromium removal. Chromium is found to be removed mostly in double-chambered MFC with a maximum removal of 100% when iron is used as an electrode. Removal of the same has led to generation of maximum power of 1965.4 mW m-2 when palladium nanoparticles are used at the electrode. Removal rates of Cr(VI) from a mixture of NiCo2O4, MoS2, and graphite felt in a dual-chamber MFC showed an 8.13% increase after 24h of light exposure. Another efficient setup used MoS2 nanosheets and Alpha-FeOOH nanoparticles in a dual-chamber MFC to completely remove Cr(VI) and achieve a high removal ratio of 91.45%. The current study reviews the recent updates in chromium reduction through MFC and its significance in future as a potential instrument for bioremediation and energy source.

Optimization of the chromium (Cr+6) reduction from waterways using chemically and bacterially treated agro-waste.

Heavy metals, a major source of pollution in the environment, pose a substantial threat due to their non-biodegradability and ability to accumulate in living organisms, causing health problems. Recently, researchers have been searching for cost-effective and safe ways to remove heavy metals from polluted waterways using agricultural waste substitutes. The present study focused on the low-cost treatments for the reduction of chromium Cr+6 metal from the effluent, wherein it has been found that chemically and bacterially treated agro-waste had increased heavy metal ion adsorption capabilities. A sequential optimization of the process parameters was attempted using Plackett-Burman design (PBD) and central composite design of response surface methodology (CCD-RSM) for the maximum reduction of the chromium metal from the effluent. A total of eight parameters were screened out using a 12-run PBD experiment. Out of the eight parameters, time, HCl, NaOH, and bacterial treatments were found to be significantly affecting the maximum reduction of Cr+6 from the effluent. To investigate the interactions' effects of the chosen parameters, they were evaluated using CCD-RSM. Maximum 74% Cr+6 reduction was achieved under the optimum treatment to rice husk of HCl 4.52 N, NaOH 3.53 N, bacterial suspension 7.41%, and with an interaction time 14.32 min using 30 run CCD-RSM experiment. A scanning electron microscope was used to confirm the effects of selected variables on the agro-waste for the Cr+6 reductions, as well as a Fourier transform infrared spectrometer.

Sensitivity enhancement of thermal acoustic particle velocity sensor based on metal film optimization

Thermal acoustic particle velocity sensors find widespread application in sound field measurements and sound source localization, owing to their capacity to capture vectorial information. This paper focuses on enhancing the sensitivity of detecting weaker signals by elevating the temperature coefficient of resistance (TCR) in the platinum thin film on the sensor's sensing wires. The study delves into the impact of annealing on the TCR of Pt thin films applied to small-sized elongated wires for thermal acoustic particle velocity sensors. The augmented effects of annealing Pt thin films with three adhesion layer metals—Chromium (Cr) and Titanium (Ti), previously commonplace in this sensor, and the newly introduced Tantalum (Ta) are scrutinized. Additionally, the influence of the deposition of Au electrodes, employed for wire bonding, both before and after annealing, on the annealing effect is also explored. In conclusion, a Pt thin film annealing process tailored for thermal acoustic particle velocity sensors is proposed, along with the recommendation of the optimal adhesion layer metal. This approach results in a substantial 20 % improvement in the TCR of the Pt thin film on the sensing wires, coupled with a corresponding 2.2 dB increase in sensor sensitivity.

Effective removal of chromium, copper, and nickel heavy metal ions from industrial electroplating wastewater by in situ oxidative adsorption using sodium hypochlorite as oxidant and sodium trititanate nanorod as adsorbent

Sodium hypochlorite and synthesized sodium trititanate nanorods (Na2Ti3O7, 186 × 1270 nm) were used as the oxidant and adsorbents for in situ oxidative adsorption treatment of actual electroplating wastewaters containing Cr(VI) (2.6‒5.2 mg∙L‒1), Cu2+ (2.7‒5.4 mg∙L‒1), and Ni2+ (0.2705‒0.541 mg∙L‒1) ions at pH of 8.8‒9.1 and 20‒60 °C. The as-synthesized sodium trititanate nanorods were characterized by XRD, HRTEM, N2 adsorption/desorption, SEM, EDX, and Zeta potential techniques. The concentrations of heavy metal ions in wastewaters were analyzed by ICP technique. After in situ oxidative adsorption treatment under the concentrations of 25 g∙L‒1 for sodium hypochlorite and 125 mg∙L‒1 for sodium trititanate nanorods at 60 °C for 5 h, the heavy metal ion concentrations could be reduced from initial value of 2.6 to final value of 1.92 mg∙L‒1 for Cr(VI), 3.6 to 0.17 mg∙L‒1 for Cu2+, and from 0.2705 to 0.097 mg∙L‒1 for Ni2+, respectively. Cr(VI), Cu2+, and Ni2+ ions could be effectively removed by the in situ oxidative adsorption method. The in situ oxidative adsorption processes of Cr(VI), Cu2+, and Ni2+ ions are satisfactorily simulated by the pseudo-second order adsorption kinetics and Langmuir adsorption isotherm, respectively. Adsorption thermodynamics analyses reveal that the oxidative adsorption processes of Cr(VI), Cu2+, and Ni2+ ions are spontaneous and endothermic. The oxidation degree of metal-contained complexes influences the values of thermodynamics functions.

The influence of heavy metals on cytotoxicity in Tilapia zillii

The present study was designed to investigate the cytotoxic effects and bioaccumulation of heavy metals iron (Fe), zinc (Zn), copper (Cu), cadmium (Cd), lead (Pb), manganese (Mn), nickel (Ni), and chromium (Cr) in different parts (muscle, gills, and liver) of Tilapia zillii occurring in polluted drainage canal and fish farm, which is located in Abiece region in front of village number 10, Alexandria governorate, Egypt. Results of water analysis revealed the concentration of Cd, Pb, Mn, Ni, and Cr exceeded the limits defined by the American Public Health Association (APHA) in the polluted drainage canal. In addition, the concentration of Ni elevated to the standard limits of APHA and Cu was not detected in the fish farm. Different types of chromosomal aberrations were recorded (e.g., stickiness, fragmented chromosomes, centromeric gaps, chromatid break, chromatid deletion, and tetraploid). Micronucleus frequency was found to be 5.58 in the polluted drainage canal group and 0.32 in the fish farm group. Other nuclear abnormalities such as blebbed nucleus, segmented nucleus, enucleated erythrocyte, kidney-shaped nucleus, heart-shaped nucleus, polymorphic irregular nuclei, binucleated cell, nuclear fragmented erythrocyte, long nucleus, putative fragmented notched nucleus, lobed nuclei, fused erythrocytes, necrotic erythrocyte, and vacuolated nucleus were recorded. The total of erythrocytes nuclear morphological abnormalities was 70.33% in the polluted drainage canal and 1.78% in the fish farm.

Treatment of greywater using a non-aerated combined horizontal and vertical flow constructed wetland

ABSTRACT Human, animal, and plant health is universally paramount, yet the release of poorly treated wastewater into the environment poses a significant risk to all life forms. Hence the need to employ wastewater treatment technologies to curb these health risks. Due to the need to adopt sustainable wastewater treatment technologies, this study investigated the use of a non-aerated hybrid horizontal and vertical flow constructed wetland for the removal of heavy metals and microorganisms from greywater. This was done at six different hydraulic retention times. Results showed significant reductions (p < 0.05) in heavy metal (manganese, zinc, cadmium, magnesium, chromium, and iron) concentrations, with some showing compliance to Ghana's Environmental Protection Agency and the United Kingdom National Environment Regulation recommended discharge limits. Heavy metal concentrations in effluent samples ranged from as low as 0.00 ± 0.15–0.23 ± 0.06 mg/L. Furthermore, there were significant reductions in Escherichia coli and Salmonella typhi (p < 0.05), which also showed compliance to Ghana's Environmental Protection Agency effluent discharge standards. The effluents from the system at HRT 3 days showed high removal efficiency ranges of 82–90% of bacteria. It is recommended that hybrid constructed wetlands should be incorporated in the treatment of greywater.

Determination of Heavy Metals Concentrations in Local and Imported Chicken Meat Found in Hilla Province Markets

This study was carried out in Hilla province, the chicken samples were collected of both local and imported chicken, the concentration of eight heavy metals (iron, copper, zinc, nickel, manganese, cadmium, lead and chromium) were measured in all samples in order to find if the concentrations of these metals were within or exceeded the permissible limit, The samples were analysis by used the Atomic Absorption spectrophotometer. The result show that for iron, copper, Zinc, nickel, manganese, cadmium, lead and chromium the concentrations were ranged from 70.66 - 81.33 ppm, 0.34 - 0.71 ppm, 6.06 - 8.21 ppm , 6.13 - 8.02 ppm, 0.213- 0.51ppm, 0.276 - 0.833 ppm, 0.733 -1.39 ppm and 0.37 - 0.716 ppm respictively . Generally, the highest heavy metal concentration was recorded in Iraqi house breading chicken. While the lowest concentrations of almost all measured heavy metal in Iraqi Farm breed in chickens.

High-Entropy Metal Nitride Embedded in Concave Porous Carbon Enabling Polysulfide Conversion in Lithium-Sulfur Batteries.

The practical implementation of lithium-sulfur batteries is severely hindered by the rapid capacity fading due to the solubility of the intermediate lithium polysulfides (LiPSs) and the sluggish redox kinetics. Herein, high-entropy metal nitride nanocrystals (HEMN) embedded within nitrogen-doped concave porous carbon (N-CPC) polyhedra are rationally designed as a sulfur host via a facile zeolitic imidazolate framework (ZIF)-driven adsorption-nitridation process toward this challenge. The configuration of high-entropy with incorporated metal manganese (Mn) and chromium (Cr)will optimize the d-band center of active sites with more electrons occupied in antibonding orbitals, thus promoting the adsorption and catalytic conversion of LiPSs. While the concave porous carbon not only accommodates the volume change upon the cycling processes but also physically confines and exposes active sites for accelerated sulfur redox reactions. As a result, the resultant HEMN/N-CPC composites-based sulfur cathode can deliver a high specific capacity of 1274 mAh g-1 at 0.2C and a low capacity decay rate of 0.044% after 1000 cycles at 1C. Moreover, upon sulfur loading of 5.0mg cm-2, the areal capacity of 5.0mAhcm-2 can still be achieved. The present work may provide a new avenue for the design of high-performance cathodes in Li-S batteries.

Heavy metal accumulation in the phytomass of plants in the Bolshoy Yugan River valley, Surgut District, Khanty-Mansi Autonomous Okrug–Yugra

Processes of heavy metal accumulation in plants are increasingly attracting research attention due to the high toxicity of such substances. The pollutants accumulated in the aerial (green leaves, stems, inflorescences) and underground (roots) mass of plants cause oxidative stress associated with the production of reactive oxygen species. In this work, we investigate the accumulation of heavy metals (nickel, lead, chromium, and cadmium) in the aerial mass of plants growing in the Surgut district of Khanty-Mansi Autonomous Okrug–Yugra. In total, leaves from 15 plant species widespread in the studied area were collected for elemental analysis by atomic absorption spectroscopy. About 6–7 mg/kg of nickel was found in the green mass of reed canary grass and heal-all (Prunella vulgaris), which exceeds significantly the nickel amount in the aerial mass of сouch grass, marsh bedstraw, and broadleaf plantain. The aerial parts of reed canary grass and broadleaf plantain were found to accumulate more than 4 mg/kg of lead, while those of bladder sedge, сouch grass, and marsh bedstraw accumulate about 2–3 mg/kg of chromium. More than 2 mg/kg of cadmium was found in сouch grass. The results obtained were used to compile series of accumulation of elements in the aerial parts of floodplain plant species. The content of the studied heavy metals in the aerial phytomass of all studied plants, except for сouch grass, ranges within standard values, corresponding to their maximum permissible concentrations.

Study on the adsorption performance of fly ash loaded on nano-FeS for chromium-containing wastewater treatment

In view of the problems caused by chromium-containing wastewater, such as environmental pollution, biological toxicity, and human health risks. Based on fly ash adsorption and nano-FeS reduction characteristics, fly ash loaded nano-FeS composite (nFeS-FA) was synthesized using mineral supported modification technology and ultrasonic precipitation method. The effect of adsorbent dosage, initial pH, contact time, and initial concentration of the solution on the adsorption of Cr(VI) and total Cr by nFeS-FA was investigated. The characteristics of Cr(VI) and total Cr adsorption by nFeS-FA were studied using adsorption isotherms, adsorption kinetics principles, as well as XRD, TEM, SEM-EDS, and BET analysis. The results demonstrated that under the conditions of nFeS-FA of 8 g/L, initial pH of 4, contact time of 150 min, and initial concentration of the solution at 100 mg/L, nFeS-FA achieved removal efficiency of 87.85 % for Cr(VI) and 71.77 % for total Cr. The adsorption of Cr(VI) and total Cr by nFeS-FA followed the Langmuir model and pseudo-second-order kinetic model, indicating monolayer adsorption with chemical adsorption as the dominant mechanism. XRD, TEM, SEM-EDS, and BET revealed that the flaky nano-FeS was uniformly distributed on the surface of fly ash, exhibiting good dispersion and thereby increasing the specific surface area. During the adsorption experiments, nFeS-FA reacted with Cr(VI), and the generated Fe3+ mainly existed as FeOOH precipitation, while S2− reacted with Cr(III) to produce Cr2S3 precipitation. Therefore, nFeS-FA exhibited excellent adsorption performance towards Cr(VI) and total Cr. It can serve as a technological reference for the remediation of heavy metal chromium pollution in the field of water treatment.

Effect of Chlorhexidine and Povidone-iodine Mouth Rinses on Corrosion Resistance and Surface Characteristics of Stainless Steel Orthodontic Brackets - An in vitro and in vivo Study.

Stainless steel (SS) orthodontic brackets may have varying corrosion resistance when used with mouthwashes during orthodontic treatment. Studying their effects on orthodontic brackets will be beneficial. The study's objective was to analyze the surface characteristics of SS orthodontic brackets and their resistance to corrosion, exposed to chlorhexidine and povidone-iodine mouth rinses - an in vitro and in vivo study. The in vitro test: MBT 0.022" slot SS orthodontic brackets were immersed in three groups - Group A - Modified Meyer-Fusayama artificial saliva (AS), Group B - Chlorhexidine, and Group C - Povidone-iodine mouthwash. The in vivo test: Brackets were conventionally bonded on the patient's teeth and divided into Group I - control group, Group II - patients used chlorhexidine, and Group III used povidone-iodine mouth rinse. The corrosion resistance and surface characteristics of SS brackets were determined using scanning electron microscope (SEM), electrochemical impedance spectroscopy, and X-ray photoelectron spectroscopy. Higher corrosion resistance was obtained for brackets immersed in chlorhexidine mouth rinse. The polarization resistance value of the orthodontic SS bracket was 109 MΩ, 1383 MΩ, and 769 MΩ immersed in AS, chlorhexidine, and povidone-iodine mouth rinse, respectively. After surface chemical analysis, XPS data showed the largest intensity peak of metallic chromium (CrO) fresh sample and in the sample immersed in chlorhexidine mouthwash. According to SEM, brackets immersed in chlorhexidine showed a relatively smooth surface. In this study, chlorhexidine was found to be less corrosive followed by povidone-iodine.

Quantitative prediction of soil chromium content using laboratory-based visible and near-infrared spectroscopy with different ensemble learning models

Soil heavy metal chromium pollution poses significant threats to human health and ecosystems, necessitating accurate quantitative prediction methods for effective monitoring and management. This study aims to develop robust predictive models for soil chromium content in farmland soils of Mojiang Hani Autonomous County, Pu’er City, Yunnan Province, China. These models utilize ensemble learning techniques based on visible and near-infrared spectroscopy. Operations before model building involved partitioning datasets with the Kennard-Stone algorithm to ensure representative training and testing sets. Visible and near-infrared spectroscopy-data preprocessing was performed using Savitzky-Golay smoothing and first-order derivative transformations to enhance signal quality. Bands selection was achieved through the Successive Projections Algorithm (SPA), effectively reducing data dimensionality and collinearity. Six ensemble learning models were constructed and assessed for their predictive performance: Bagging-DTR, Random Forest (RF), Adaboost-DTR, XGBoost-DTR, Stacking-1, and Stacking-2. These models utilized Decision Trees (DTR) and Linear Regression (LR) as base learners. Results demonstrated that ensemble models significantly outperformed individual base learners. Notably, the Stacking-2 model achieved the highest accuracy with an R^2 of 0.954, RMSE of 125.967 mg/kg, and RPD of 4.667. To validate the model’s practical applicability, spatial interpolation of soil Cr content was conducted using the Kriging method based on Stacking-2 model predictions. The spatial distribution maps of measured and predicted values exhibited high congruence, underscoring the model’s effectiveness in accurately mapping Cr distribution across the study area. This study underscores the efficacy of integrating ensemble learning with visible and near-infrared spectroscopy-data preprocessing and SPA for precise soil heavy metal prediction. The findings offer valuable insights and a scientific basis for enhanced soil quality monitoring, environmental risk assessment, and informed agricultural land management and pollution control.

Molecular Identification of Potent Chromium Reducing Bacteria Isolated from Hydrocarbon-Contaminated Soil within Sokoto Metropolis

Study’s Novelty/Excerpt This study investigates chromium reduction potential of bacteria isolated from hydrocarbon-contaminated soils in the Sokoto metropolis, a specific environment previously underexplored in this context. It uniquely identifies Brucella intermedia and Bacillus sp. as potent chromium-tolerant isolates with significant reduction efficiencies, providing new insights into the bioremediation capabilities of these strains. Additionally, the research demonstrates a high chromium removal efficacy at various concentrations, highlighting the potential application of these isolates for effective bioremediation of chromium-polluted soils and water bodies. Full Abstract Hydrocarbon-contaminated soils are recognised as reservoirs for heavy metal-utilizing bacteria due to the phenomenon of co-selection. These bacteria can have a potential in the biosorption of chromium heavy metal. This research aimed to screen the chromium reduction potential of bacteria isolated from hydrocarbon-contaminated soils. The soil samples used in this study were collected from hydrocarbon-affected sites in the Sokoto metropolis; additionally, a control sample was collected from non-polluted soil. Bacteria were isolated using standard protocols. Variable amounts of chromium were prepared using potassium monochromate (K2CrO4) and then incorporated into a nutrient broth medium. The most potent, molecularly-identified hydrocarbonoclastic bacteria were screened for chromium tolerance, and the percentage reduction in chromium content was also measured. Mean colony counts from the hydrocarbon-contaminated soil ranged from1.00×106 to 1.30×106 CFU/g while the control soil had 2.30×105 CFU/g. From the 14 strains, two, molecularly identified using NCBI BLAST as Brucellaintermedia and Bacillus sp., were shown to be the most potent chromium tolerant isolates. B. intermedia reduced Cr from an initial value of 350 mg/L to 198 mg/L within 72 hours (44 % removal efficiency). At the lowest concentration used in this study (50 mg/L), a removal efficacy of 96% was achieved. Bacillus sp. recorded the highest chromium reduction compared to Brucellaintermedia at the tested concentrations (50, 150, 250, and 350 mg/L). A 100% reduction in Cr was obtained at the 50 mg/L concentration. This study demonstrated that Bacillus sp. and Brucellaintermedia are particularly effective at reducing chromium from chromium metal solutions of different concentrations. These isolates can be used for bioremediation of chromium-polluted soils or water bodies.

The Risks and Impacts of Chromium Metals on Human Health and Ecosystems

The Risks and Impacts of Chromium Metals on Human Health and Ecosystems

Heavy Metals Contamination in Snow Cover of Pavlodar (Kazakhstan)

A study of the concentration of heavy metals in snow cover was carried out in Pavlodar in the area of influence of the Pavlodar Petrochemical Plant and other industrial facilities. Significant excesses of background concentrations of manganese, chromium, vanadium and other metals were detected. The distribution of metals in the snow cover showed that the elements have high values near the oil refinery and decrease at a distance of 700 m. The possible influence of other industrial enterprises and the direction of winds from CHP-3 are also noted. Manganese and barium show more stable values, and chromium, zinc, lead and cadmium have increased concentration near JSC “Kaustik”. The total concentration of manganese, strontium, cobalt and arsenic varies slightly across all sites, indicating uniform contamination by these substances. Lead is highest in industrial areas and in populated areas with highways. Aluminum and iron are widespread, with the lowest values in the Zhanaul village at a distance of 3 km from the Petrochemical Plant. The results of the study highlight the importance of controlling and monitoring heavy metal pollution and the need to take measures to reduce anthropogenic impacts on the natural environment.

Alleviation of heavy metals chromium, cadmium and lead and plant growth promotion in Vigna radiata L. plant using isolated Pseudomonas geniculata.

Plants exposed to heavy metals (HMs) stress negatively affect their development and production capacity. Chromium (Cr), Cadmium (Cd), and Lead (Pb) are the most common hazardous trace metals in agriculture. The physiological, biochemical, and molecular characteristics of crops are being affected. Phytoremediation is a method to alleviate heavy metals from the contaminated soil. The study aims to evaluate the phytoremediation ability of Vigna radiata L. (mung bean) in the absence and the presence of multi-metal tolerant and plant growth promoting Pseudomonas geniculata strain TIU16A3 isolated from soil of tannery industrial estate, Kolkata, West Bengal, India. The strain was further assessed with increasing concentrations of Cr, Cd, and Pb (10, 20, 40, and 80µg/mL) when the mung bean plant was a test crop. The strain significantly increased plant growth, chlorophyll content, increased level of antioxidant enzymes such as superoxide dismutase, peroxidase, and catalase, and decreased oxidative stress indicators like H2O2 and electrolyte leakage in the presence of Cr, Cd, and Pb as compared to plants grown in the absence of Pseudomonas geniculata strain. Shoot length responsive gene (Aux/IAA) in the presence of heavy metal alone and Pseudomonas geniculata treated Cd and Cr showed higher relative expression of (Aux/IAA) compared to Pb. Due to these intrinsic abilities, Pseudomonas geniculata strain TIU16A3 can be a plant growth promoter and thus can help in the remediation of heavy metal (Cr, Cd, and Pb) contaminated soil.

Visible-light-driven Z-scheme La-MOF/BiOBr heterojunction for the efficient removal of rhodamine B and hexavalent chromium from wastewater

Addressing the formidable challenge of treating significant quantities of organic dyes and heavy metal chromium in tannery wastewater, this study synthesized a novel Z-scheme La-MOF/BiOBr composite heterojunction photocatalyst via the hydrothermal method and established an efficient visible-light photocatalytic system. To comprehensively evaluate the photocatalytic redox activity, rhodamine B (RhB) and heavy metal Cr(VI) were selected as target pollutants. Kinetic analysis revealed that the optimal LM-BB-50 catalyst achieved over 99 % degradation of RhB and Cr(VI) within 15 min illumination, indicating the remarkable enhancement of Z-scheme heterojunction in photocatalytic oxidation and reduction efficiency. Based on various photoelectric analysis techniques, it was elucidated that the superior activity of the Z-scheme heterojunction originated from the modulation of the band structure upon La-MOF and BiOBr integration, significantly improving visible light absorption, electron-hole pair separation efficiency, and endowing the energy band with robust redox capabilities. Free radical capture and quenching experiments confirmed that photogenerated holes and superoxide radicals played a crucial role in RhB oxidation, while photogenerated electrons were the primary active species for Cr(VI) reduction.

The Speciation of Heavy Metal Chromium in Water Environment by Carbon Quantum Dots System

The Speciation of Heavy Metal Chromium in Water Environment by Carbon Quantum Dots System

PET microplastics influenced microbial community and heavy metal speciation in heavy-metal contaminated soils

Co-occurrence of microplastics and heavy metals is common in soils. The interactions between microplastics and heavy metals have received increasing attention in recent years, particularly for revealing the mechanisms underpinning their interactions. In the present study, Polyethylene Terephthalate (PET) microplastics are added in soil, which have led to variations in soil physicochemical properties, enzymatic activity, microbial community structure, and chemical speciation of chromium (Cr), cadmium (Cd), copper (Cu), and zinc (Zn) in heavy metal contaminated soils. Soil physicochemical properties (pH, SWC and SOC) and enzymatic activities (urease and dehydrogenase) alter as result of PET addition, which promoted the transformation of heavy metal chemical speciation from bioavailable fraction to oxidizable and residual fraction. The results suggested that PET microplastics in heavy metal contaminated soil may reduce the heavy metal bioavailability by altering the properties of the soil microenvironment. The significant variations in microbial community have been observed. The relative abundance of Gp6, Gaiella, Nocardia, Herbaspirllum and Gp16 changed dramatically throughout the incubation period, which were either heavy metal tolerant or played crucial roles in modifying the chemical composition of heavy metals. This work contributes to an in-depth understanding of the effects of microplastics on the biochemical transformation of heavy metal contaminated soils, which will be valuable to the development of clean up strategy for soils with co-contaminant of microplastics and heavy metals.