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Abstract\nNOVELTY STATEMENTThe toxic Cr(VI) contaminating water released from the metallurgical, dyeing, and electroplating industries is getting worse day by day and is extremely hazardous to human health. Thus, the development of a cost-effective, quick, and efficient adsorbent is highly essential for the Cr(VI) decontamination from wastewater. Herein, a microwave-assisted carbon-based composite called Mg-Fe LDH@OPAC was prepared by assembling Mg-Fe LDH onto orange peel-activated carbon (OAPC). Prior to investigating deeply into the adsorption behavior of the composite, the Mg-Fe LDH@OPAC formation was confirmed by using instrumental techniques like FESEM, EDS, Zeta potential, XRD, FTIR, Raman, XPS, and BET analyzer. The material had a high surface area of 143.9 m2/g and showed a good monolayer Langmuir uptake capacity of 118.36 mg/g. Under ideal circumstances, the maximum amount of Cr(VI) was removed within just 120 min and showed high efficiency in the presence of other coexisting anions respectively. The adsorption was accounted by pseudo-second-order kinetics and spontaneous in nature. Ultimately, a possible adsorption mechanism was suggested, confirmed by XPS studies; which showed that oxidation-reduction, electrostatic interaction, and surface complexation reaction were responsible for Cr(VI) adsorption on Mg-Fe LDH@OPAC surface.Environmental contaminants like Cr(VI) in drinking water are highly toxic, and their long-term persistence in the water environment causes mutagenic effects on human beings. We present a novel material for the first time (yet not been reported) by intercalating activated carbon (from a low-cost wedge of orange peel) into Mg-Fe layered double hydroxide (abbreviated as Mg-Fe LDH@OPAC), which has superior hazardous hexavalent chromium metal uptake capability. With the order of SO42->F->CO32->I->PO43->NO3- the as-prepared Mg-Fe LDH@OPAC exhibits strong selectivity toward Cr(VI) in the presence of varied competing ions with a modest drop in removal effectiveness. The combined properties of AC and LDH make Mg-Fe LDH@OPAC potentially efficient adsorbent to remove Cr(VI) from the different water sources and potentially applied in wastewater treatment. [ABSTRACT FROM AUTHOR]

Hexavalent chromium (Cr(VI)) contamination in drinking water due to industrial activities is a growing worldwide concern. Cr(VI) concentrations exceeding a few parts per billion (ppb) can cause serious health problems such as asthma, blood cancer, kidney-related diseases, liver and spleen damage, as well as neurological system, immunological deficiencies, and reproductive issues. This study, thus, explored the feasibility of employing a novel polymeric ferromagnetic nanocomposite adsorbent made of low-cost, biodegradable, and ultra-permeable materials from pulp and paper sludge for adsorptive removal of hexavalent chromium (Cr6+) from synthetic wastewater. Vibrating-sample magnetometer (VSM), X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmet-Teller surface area (BET), and Fourier transform infrared (FTIR) were used to analyze the produced nanocomposite adsorbent. The Fourier transform infrared results confirmed the presence of adsorptive peaks attributed to −OH, −NH2, and FeO. Scanning electron microscopy micrographs revealed a porous adsorbent surface. XRD revealed the existence of the crystalline spinel-structured magnetite (Fe3O4) phase of iron oxide, while the saturation magnetization was established to be 26.90 emu/g. The Brunauer–Emmett–Teller analysis confirmed a slight decrease in the surface area of the nanocomposite adsorbent to 6.693 m2.g−1, compared to Fe3O4 (7.591 m2.g−1). The optimum conditions for Cr6+ removal were pH 2.0, 1.0 g/L adsorbent dose, room temperature (25°C), 120 min contact time, and 20 mg/L pollutant concentration. During removal, the Cr(VI) was adsorbed by electrostatic attraction and/or reduced to trivalent chromium Cr(III). At low starting Cr(VI) concentrations, chemisorption dominated the removal process, but as concentrations increased, physisorption became more significant. The prepared nanocomposite adsorbent presented exceptional removal efficiency of up to 92.23%, indicating that it may be useful for the adsorption of metal ions from industrial and household wastewater. [ABSTRACT FROM AUTHOR]

AbstractHexavalent Chromium (Cr(VI)) is essential in many industrial processes. However, it finds its way into water bodies, posing health problems, including lung cancer and the inhibition of DNA and RNA in biological systems. Several chemical and traditional water purification methods have been developed in the past, but most are expensive, tedious and ineffective. This study aimed to prepare and characterize a low-cost hybrid adsorbent, β-Cyclodextrin capped magnetic nanoparticles anchored on a cellulosic matrix (CNC-Fe3O4NP-CD). The characterization techniques confirmed the integration of CNCs, Fe3O4NP and CD into the prepared CNC-Fe3O4NP-CD nanocomposite adsorbent. The adsorbent was employed in batch adsorption experiments by varying adsorption parameters, including solution pH, adsorbent dosage, initial Cr(VI) concentration, and contact time. From the findings, the nanocomposite adsorbent achieved a maximum Cr(VI) removal efficiency of 97.45%, while the pseudo-second-order kinetic model best fitted the experimental data with high linear regression coefficients (R2 > 0.98). The Elovich model indicated that the adsorption process was driven by chemisorption on heterogeneous surface sites, with initial sorption rates surpassing desorption rates. These findings established that CNC-Fe3O4NP-CD presents high efficiency for Cr(VI) removal under acidic pH, offering the potential for optimization and application in real-world wastewater treatment. [ABSTRACT FROM AUTHOR]

Ce2(SO4)3 was doped into 4,6-diamino-2-mercaptopyrimidine (DAMP)-encapsulated copper nanoclusters (CuNCs) via a facile, rapid, low-temperature, and green self-assembly synthesis method to obtain fluorescent S,N-codoped Cu/Ce-DAMP nanoparticles (S,N-codoped Cu/CeNPs) for the detection of Cr(VI). The prepared Cu/CeNPs exhibit double emission peaks at 470 nm and 610 nm. The fluorescence emission at 610 nm is significantly enhanced due to the aggregation-induced emission (AIE) effect, and the quantum yield is as high as 20.19%. The fluorescence emission at 610 nm can be selectively quenched by Cr(VI) due to the internal filter effect (IFE) and dynamic quenching, whereas the weak fluorescence at 470 nm remains almost stable. On this basis, a fluorescence assay method for Cr(VI) was established, with good linearity in the concentration range 0.5–120 µM and a detection limit (LOD) of 134 nM. Using a smartphone to take photos of the fluorescence signals changes caused by Cr(VI) rapid visual detection is achieved with a linear range of 10–130 μM and a LOD of 2.35 μM. The proposed method was successfully applied to the detection of Cr(VI) in actual water samples. [ABSTRACT FROM AUTHOR]

This article presents a low-cost photometer for experimental teaching designed to determine hexavalent chromium in aqueous solutions based on the detection of yellow chromate ions with ultraviolet light at 373 nm. This procedure replaces the colorimetric method that uses a spectrophotometer for the detection of the red-violet 1.5-diphenylcarbazide complex at 540 nm. To demonstrate the operation of the photometer, the Beer-Lambert law was evaluated using the linear regression technique, and the absorbance values obtained by the photometer were compared with those of a Shimadzu UV-2600 series UV-Vis spectrophotometer in five samples of hexavalent chromium in the range of 1 - 25 mg L-1. The experimental results demonstrated the linearity required by the Beer-Lambert law with a determination coefficient of 0.9988, and similarity between both analytical instruments with a relationship of 1.0041 between the absorbance values with a determination coefficient of 0.9993. In conclusion, the low-cost photometer is an excellent proposal for teaching the Beer-Lambert law in the classroom because it reduces the formation of waste, and dispenses with the reagents of the colorimetric method. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe-doped cerium-based adsorbents exhibited better Cr(VI) adsorption advantages than pure cerium material. • Fe doping promoted the formation of Ce(III) in cerium-based adsorbents. • Fe doping contributed to the formation of oxygen vacancy in cerium-based adsorbents. • Fe doping facilitated the valence transition of Ce(IV)/Ce(III) in Cr(VI) adsorption. • DFT calculation result revealed that Fe doping accelerated the electron transfer in Cr(VI) reduction. Cerium-based adsorbents possessed unique advantages of valence variability and abundant oxygen vacancies in hexavalent chromium (Cr(VI)) adsorption, but high cost and unstable properties restricted their application in Cr(VI) contained wastewater treatment. Herein, a series of bimetallic adsorbents with different cerium/iron ratios (CeFe@C) were prepared by adding inexpensive Fe into Ce-based adsorbents (Ce@C), and the effect of Fe doping on adsorption properties of Ce@C for Cr(VI) was investigated thoroughly. Compared with pristine Ce@C, CeFe@C exhibited excellent removal performance for Cr(VI), and the improved maximum adsorption capacity reached 75.11 mg/g at 25℃. Benefiting from Fe doping, CeFe@C had good regeneration property, with only 25 % decrease after five adsorption–desorption cycles. Contents of trivalent cerium (Ce(III)) and oxygen vacancies (O v) in bimetallic adsorbents were positively correlated with divalent iron (Fe(II)) doping, indicating that the formation of Ce(III) and surface defects on Ce@C could be effectively regulated by Fe doping. Density functional theory (DFT) calculation results further proved that the doped Fe enhanced the electron transfer effectively and lowered the energy barriers of Cr(VI) adsorption onto Ce@C surface, strengthening the reduction and complexation to Cr(VI). This study provides new insights for improving the Cr(VI) removal performance by modified Ce-based adsorbents, and further promotes the utilization potentiality of low-cost and low-toxicity Ce-based adsorbents in Cr(VI)-containing wastewater treatment. [ABSTRACT FROM AUTHOR]

The article discusses a project in Italy that addressed the issue of hexavalent chromium (Cr(VI)) in groundwater in the province of Piacenza. Due to new regulations, an iterative process was developed to assess the problem, identify treatment technologies, define project priorities, and implement solutions within budget and time constraints. The project included site identification, technology choices, intervention planning, and process improvements, resulting in improved water quality and reduced Cr(VI) levels ahead of regulatory deadlines. The project showcased efficient planning and technology selection for successful implementation. [Extracted from the article]

Microbial electrochemical technologies represent innovative approaches to contaminated soil and groundwater remediation and provide a flexible framework for removing organic and inorganic contaminants by integrating electrochemical and biological techniques. To simulate in situ microbial electrochemical treatment of groundwater plumes, this study investigates Cr(VI) reduction within a bioelectrochemical continuous flow (BECF) system equipped with soil‐buried electrodes, comparing it to abiotic and open‐circuit controls. Continuous‐flow systems were tested with two chromium‐contaminated solutions (20–50 mg Cr(VI)/L). Additional nutrients, buffers, or organic substrates were introduced during the tests in the systems. With an initial Cr(VI) concentration of 20 mg/L, 1.00 mg Cr(VI)/(L day) bioelectrochemical removal rate in the BECF system was observed, corresponding to 99.5% removal within nine days. At the end of the test with 50 mg Cr(VI)/L (156 days), the residual Cr(VI) dissolved concentration was two orders of magnitude lower than that in the open circuit control, achieving 99.9% bioelectrochemical removal in the BECF. Bacteria belonging to the orders Solirubrobacteriales, Gaiellales, Bacillales, Gemmatimonadales, and Propionibacteriales characterized the bacterial communities identified in soil samples; differently, Burkholderiales, Mycobacteriales, Cytophagales, Rhizobiales, and Caulobacterales characterized the planktonic bacterial communities. The complexity of the microbial community structure suggests the involvement of different microorganisms and strategies in the bioelectrochemical removal of chromium. In the absence of organic carbon, microbial electrochemical removal of hexavalent chromium was found to be the most efficient way to remove Cr(VI), and it may represent an innovative and sustainable approach for soil and groundwater remediation. Integr Environ Assess Manag 2024;20:2033–2049. © 2024 The Author(s). Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC). Key Points: The research offers valuable insights that can contribute to advancing microbial electrochemical remediation systems designed to reduce Cr(VI) in water‐saturated soils.There were substantial differences from previously reported studies: acclimatization and/or adaptation and transfer of the electroactive bacterial community to Cr(VI) to a bioelectrochemical continuous flow system, no ion exchange membranes, and no nutrients and/or organic carbon added.The research was conducted to simulate most realistically the real conditions of Cr(VI)‐contaminated aquifers, in terms of solid‐to‐liquid ratio, interactions among soil phases, and physicochemical parameters (pH and electrical conductivity).The outcomes achieved in the system for Cr(VI) reduction in water‐saturated soil can demonstrate the feasibility of employing microbial electrochemical technology for the in situ treatment of contaminated aquifers, with interesting implications for economic and environmental sustainability. [ABSTRACT FROM AUTHOR]

Removing heavy metal ions from wastewater reduces health and ecological risks and allows for their reuse. Polymer inclusion membranes with integrated ion carriers offer an efficient solution for removing toxic metal ions from industrial wastewater. These membranes can be further enhanced by using biodegradables polymer blends and incorporating nanofillers to improve their selectivity, stability, extraction efficiency, and biodegradability. In this study, a novel biodegradable polymer blend consisting of 54% poly(lactic acid) (PLA) and 13% polybutylene adipate terephthalate (PBAT) was utilized as the base polymer, with 30% Aliquat 336 as an ion carrier and either 3% graphene oxide (GO) or 3% cloisite 30B (C30B) as nanofillers. The hybrid blend contained a total of 3% nanofillers, with 1.5% graphene oxide (GO) and 1.5% cloisite 30B (C30B). These components were integrated through the evaporation casting method and evaluated for their potential as polymer inclusion membranes (PIMs) for Cr(VI) extraction. Various analytical methods, including X-ray diffraction (XRD), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA), were employed to explore the microstructure-property relationships of the fabricated nanocomposite PIMs. The analyses revealed the development of new semi-crystalline membrane structures, resulting in enhanced hexavalent chromium extraction. It was found that the presence of nanofillers altered the bulk structure, creating apparent microvoids in the membranes filled with 3% GO and the hybrid membrane, which were not observed in membranes filled with C30B. This resulted in higher extraction efficiency in the membranes loaded with GO, whereas membranes loaded with C30B exhibited decreased Cr(VI) extraction. An intermediate extraction percentage was found in the hybrid membrane filled with both nanofillers. Additionally, the incorporation of GO and C30B significantly improved membrane stability across various media, reducing mass loss in NaCl/NaOH to 13.36%. The TGA analyses further confirmed that membranes incorporating GO and C30B exhibited improved thermal stability. [ABSTRACT FROM AUTHOR]

AbstractContamination of hexavalent chromium (Cr(VI)) is a major environmental issue since it has the ability to cause cancer and genetic mutations. Bioremediation techniques using Pseudomonas aeruginosa have emerged as potential methods to tackle this problem. This study offers a thorough examination of the underlying mechanisms and potential future paths in the process of P. aeruginosa-mediated Cr(VI) remediation. Herein, the strategies used by P. aeruginosa were examined for the removal of Cr(VI) via processes such as biosorption, intracellular reduction, and extracellular metabolism. In addition, the function of extracellular polymeric substances (EPS) in capturing and isolating Cr(VI) was studied and the possibility of using genetic engineering techniques to improve P. aeruginosa’s ability to remove Cr(VI) from the environment was explored. In addition, we investigate the difficulties related to the use of P. aeruginosa for Cr(VI) bioremediation, such as environmental conditions and the presence of other microorganisms, and suggest potential areas for further study. These include the development of bioremediation strategies using consortia of microorganisms and the incorporation of nanomaterials to improve the removal of Cr(VI). This study seeks to enhance the development of sustainable solutions for remediating Cr(VI) by integrating existing information and identifying future research directions, with a focus on employing P. aeruginosa. [ABSTRACT FROM AUTHOR]

Hexavalent chromium (Cr(VI)) has attracted much attention because it is a harmful pollutant. In this study, acid hydrolyzed hydrothermal double modified starch (AHS) and hydroperoxide oxidized starch (HOS) are prepared from natural starch and used for the reduction of chromium (VI) in aqueous systems. The effects of hydrothermal acidolysis and oxidative modification of starch on the reduction rate of Cr(VI) are discussed, including the changes of solubility, swelling power, particle size, content of straight‐chain starch, and carbonyl/carboxylic group content. The results of response surface methodology (RSM) optimization show that the influence of reaction conditions on the reduction rate of Cr(VI) by NS is as follows: reaction time > initial pH of solution > reaction temperature > starch to Cr(VI) mass ratio; and on the reduction rate of Cr(VI) by AHS and HOS is as follows: initial pH of solution > reaction time > starch to Cr(VI) mass ratio > reaction temperature. [ABSTRACT FROM AUTHOR]

Given the high solubility and mobility of hexavalent chromium in the environment and edible plants, the development of a suitable method for the screening and quantification of Cr(VI) is highly desirable. Herein, a selective and sensitive sensing method for detecting Cr(VI) in food grains was established, using an electrodeposited gold‐palladium bimetallic nanoparticles (BNPs) based electrochemical sensor and a microwave digestion procedure for chromium dissolution. The sensor interface was characterized by scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDX) and cyclic voltammetry. The results indicate that the fabricated sensor has a larger active surface area and an enhanced electrocatalytic effect compared to the monometallic modification, leading to a significant increase in the electrochemical reduction current of Cr(VI) as a consequence of synergistic effects. Using square wave anodic stripping voltammetry, the sensor demonstrates a wide linear range (5–3000 μg L−1) and a low detection limit of 2.7 μg L−1 for Cr(VI), as well as considerable repeatability and stability. Satisfactory selectivity towards Cr(VI) was also demonstrated, even in the presence of 500‐fold Cr(III) and 100‐fold common heavy metal ions like Cd(II), Pb(II), and Hg(II). The proposed sensing method offers a promising alternative for rapidly identifying toxic Cr(VI) in water and food grains. [ABSTRACT FROM AUTHOR]

This work explores the impact of reaction temperature during thermal exfoliation treatment of bulk-g-C3N4 in the air atmosphere on the structure and performance of the resulting CN photocatalyst. The analysis conducted using XRD, FT-IR, XPS, SEM, and elements mapping tests, illustrated an increase in nitrogen-vacancy and oxygen content on the surface of the CN photocatalyst, resulting in a porous and sparse structure, changes in crystal size, and improved visible light absorption performance. The photocatalytic reduction experiments of hexavalent chromium (Cr(VI)) showed that the CN-540 showed the highest reduction rate of 96.9%, with a reaction rate constant 6.21 times that of bulk-g-C3N4. After 100 min of illumination, the photocatalytic degradation rates of CN-540 for TC-HCl and RhB were 66.7% and 60.6%, respectively. The TOC test results indicated mineralization rates of 51.5% for TC-HCl and 46.6% for RhB. Room temperature fluorescence spectroscopy (PL), transient photocurrent response (TPC), and electrochemical impedance spectroscopy (EIS) measurements confirmed the excellent photogenerated charge carrier separation and transport efficiency of CN-540. The photocatalytic mechanism for reducing Cr(VI) by CN-540 was elucidated based on the active species •OH and •O2 - and Mott-Schottky (M-S) tests. This study provides experimental data for optimizing the photocatalytic performance of g-C3N4 and paves a new way for developing efficient photocatalysts. [ABSTRACT FROM AUTHOR]

The removal of hexavalent chromium [Cr (VI)] using non-living cells of Yarrowia lipolytica was investigated. Batch and continuous studies on removal of Cr (VI) achieved 97% and 99% removal from aqueous phase, respectively. The specific uptake values at pH of 2 in batch process were 40.73 ± 1.3 mg/g and 30.09 ± 0.23 mg/g on non-living cells, when 100 and 200 mg/L of metal Cr (VI) concentrations were used. In order to investigate the regulation of Cr (VI) under continuous operation based on reaction volume numerically a new class of feedback controller from structure polynomial was designed. The proposed methodology was used to an experimentally kinetic model for a removal Cr (VI) from Yarrowia lipolytica biomass was showed satisfactory closed-loop performance the proposed controller. Starting from an off-line optimization performed in simulation, we present the controller implementation, focussing on the methodology required to could be suitable for implementation in real time. In our experimental results, we highlight some discrepancies between simulation and reality despite these differences, the controller managed to perform convergence to removal Cr (VI). Finally, the results validated with off-line samples suggest that the proposed control could be suitable for in application in potential scenarios for wastewater treatment. [ABSTRACT FROM AUTHOR]

A series of Sb x Bi 2-x S 3 solid solution photocatalysts with certain sulfur vacancy were constructed by adjusting the molar ratio of Sb to Bi through a simple hydrothermal strategy and applied for the efficient elimination of Cr(VI). [Display omitted] • Sb x Bi 2-x S 3 solid solution was constructed by a simple hydrothermal strategy. • Sb 1.75 Bi 0.25 S 3 can effectively remove Cr(VI) and exhibit excellent stability. • The certain sulfur vacancy effectively accelerates the separation of charge. The development of environmentally friendly and cost-effective photocatalysts is of vital significance for the effective removal of heavy metal contamination in water, but it is still a crucial challenge. Herein, the novel Sb x Bi 2-x S 3 solid solution photocatalysts with a certain amount of sulfur vacancy were prepared by adjusting the molar ratio of Sb to Bi through a simple hydrothermal strategy, and was applied to the effective photocatalytic reduction of hexavalent chromium (Cr(VI)). Sb 1.75 Bi 0.25 S 3 with optimized ratio has superior reduction performance of Cr(VI), and the photocatalytic efficiency of Cr(VI) can achieve 91.9 % within 1 h of visible light illumination. The remarkable catalytic efficiency is due to the more applicable band structure of the solid solution photocatalyst, which is conducive for the photocatalytic reaction. Moreover, the substitution of Bi causes the crystal distortion of Sb 2 S 3 and induce the generation of sulfur defects, which can effectively capture photoelectrons, accelerate the carriers separation, and improve the reduction performance. This study provides a hopeful photocatalyst for wastewater purification and promotes the exploration of solid solution photocatalyst in water environment remediation. [ABSTRACT FROM AUTHOR]

Text: The novel photocatalyst OrPhC 2 Cu was developed by creatively converting the adsorbed oxygen on the surface of PhC 2 Cu into a functional Cu–O bond. It proves to be effective in promoting Cr(VI) photoreduction, as well as the photodegradation of pharmaceuticals and personal care products (PPCPs) and dyes. This effectiveness is attributed to its enhanced visible-light response, as well as the promotion of exciton dissociation and charge transfer. [Display omitted] The widespread contamination of hexavalent chromium (Cr(VI)), pharmaceuticals and personal care products (PPCPs), and dyes is a growing concern. necessitating the development of convenient and effective technologies for their removal. Copper(I) phenylacetylide (PhC 2 Cu) has emerged as a promising photocatalyst for environmental remediation. In this study, we introduced a functional Cu–O bond into PhC 2 Cu (referred to as OrPhC 2 Cu) by creatively converting the adsorbed oxygen on the surface of PhC 2 Cu into a Cu–O bond to enhance the efficiency of Cr(VI) photoreduction, PPCPs photodegradation, and dyes photodegradation through a facile vacuum activating method. The incorporation of the Cu–O bond optimized the electron structure of OrPhC 2 Cu, facilitating exciton dissociation and charge transfer. The exciton dissociation behavior and charge transfer mechanism were systematically investigated for the first time in the OrPhC 2 Cu system by photoelectrochemical tests, fluorescence and phosphorescence (PH) techniques, and density functional theory (DFT) calculations. Remarkably, the enhanced visible-light response of OrPhC 2 Cu improved photon utilization and significantly promoted the generation of reactive species (RSs), leading to the highly efficient Cr(VI) photoreduction (98.52% within 25 min) and sulfamethazine photodegradation (94.65% within 60 min), with 3.91 and 5.23 times higher activity compared to PhC 2 Cu. Additionally, the photocatalytic efficiency of OrPhC 2 Cu in degrading anionic dyes surpassed that of cationic dyes. The performance of the OrPhC 2 Cu system in treating electroplating effluent or natural water bodies suggests its potential for practical applications. [ABSTRACT FROM AUTHOR]

Zinc oxide and nickel oxide nanocomposite was successfully synthesized using the co-precipitation technique and evaluated for their photocatalytic efficiency in the degradation of hexavalent chromium. The synthesized nanocomposite was characterized using various techniques such as X-ray diffraction, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy to analyze its structure, morphology, chemical bonding, photoabsorption properties, and elemental composition. X-ray diffraction exhibits the presence of zinc oxide, nickel oxide, and zinc oxide and nickel oxide nanocomposite, with average crystallite sizes of 37.92 nm, 56.23 nm, and 41.77 nm, respectively. Fourier transform infrared spectroscopy was used to analyze the chemical composition of zinc oxide and nickel oxide nanocomposite. The ultraviolet–visible spectroscopy exhibited an absorption peak at 447 nm, indicating a bandgap of 2.77 eV. A novel industrial-oriented photoreactor was designed for the reduction of hexavalent chromium under ultraviolet–visible illumination with varying operational parameters. The effectiveness of the experiment was assessed using response surface methodology based on central composite design, which demonstrated a remarkable 95% reduction of hexavalent chromium under optimized conditions. This study validates the accuracy of central composite design in predicting levels of hexavalent chromium reduction. The rate constant for the degradation kinetics of hexavalent chromium was studied to be 0.00450 min−1, indicating adherence to pseudo-second-order kinetics. Additionally, the prepared nanocomposite exhibited significant antibacterial activity against Bacillus subtilis, Escherichia coli, and Pseudomonas putida at different concentrations. [ABSTRACT FROM AUTHOR]

Hexavalent chromium (Cr[VI]) is a widespread environmental pollutant in air and water that is primarily attributed to industrial pollution. The current maximum contaminant levels (MCLs) for drinking water from the World Health Organization and the U.S. Environmental Protection Agency (0.05 and 0.1 mg/L, respectively) were set based on contact dermatitis and warrant further toxicological investigation. While Cr(VI) is neurotoxic and accumulates in the brain, most animal studies only report whole-brain Cr, leaving large knowledge gaps. Few studies consider differences between ages or sexes, and fewer consider essential metal dyshomeostasis. We sought to investigate where Cr accumulates in the brain, considering sex and age differences, following a 90-day drinking water exposure to current MCLs. Here, we report Cr levels in six brain regions of rats exposed to drinking water Cr(VI). We observed Cr only accumulated in the hippocampus, and only in older females. We further assessed changes to essential metals in the hippocampus, observing opposite effects across sexes and between young rats compared to older rats. In sum, our data indicate drinking water Cr(VI) selectively targeted the hippocampus, with geriatric females accumulating the most Cr, and induced significant essential metal dyshomeostasis even in tissues lacking evident Cr accumulation. [ABSTRACT FROM AUTHOR]

To solve the problem of heavy metal hexavalent chromium (Cr(VI)) pollution in water bodies, this study was carried out to prepare nitrogen-doped porous carbon by using bamboo shoots as the raw material and KHCO3 as the activator, which has a good ability to remove Cr(VI) from water bodies. The prepared N-doped carbon materials were characterized by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), elemental analysis, and scanning electron microscopy (SEM). The results showed that the prepared carbon material had hierarchical pore structures and abundant functional groups, which is conducive to the adsorption of Cr(VI). The effects of various factors on the adsorption performance of Cr(VI), such as the carbon materials prepared under different conditions, the pH of the initial solution, the concentration of the initial solution, and the contact time between the carbon and Cr(VI), were explored. The results showed that the bamboo shoot-based nitrogen-doped carbon materials, especially BSNC-800 (prepared at 800 °C with a mass ratio of KHCO3 to bamboo shoot of 4:1), performed well in removing Cr(VI) from a water solution. The maximum adsorption of Cr(VI) by BSNC-800 under equilibrium conditions was 385.8 mg g−1 (conditions: at the pH of 2 with the initial concentration of 400 mg L−1). The adsorption kinetics and isotherms were analyzed, and the adsorption mechanism was discussed. It can be found that the adsorption of Cr(VI) by BSNC-800 fits better with the Langmuir isotherm model and the pseudo-second-order kinetic model. The adsorption mechanism between the Cr(VI)-containing solution and BSNC-800 was controlled by membrane diffusion and chemisorption. The results broaden the ways of utilizing biomass resources as precursors of carbon materials, which is significant and helpful for applying biomass carbon materials as adsorbents for wastewater treatment. [ABSTRACT FROM AUTHOR]

Nanocomposites (NCs) consisting of zero-valent iron nanoparticles (nZVI) immobilized in chitosan (CS) were prepared and employed for the removal of hexavalent chromium (Cr(VI)) from both synthetic and real wastewater. Medium (MCS)- and high (HCS)-molecular-weight chitosan and stabilization with carboxymethylcellulose (CMC) and different nZVI loads were explored. Characterization through scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDS) and X-ray diffraction (XRD) revealed millimeter-sized spheres with micrometer-sized nZVI clusters randomly distributed. Better nanoparticle dispersion was observed in NCs from the CMC-MCS and HCS combinations. Fourier-transform infrared spectroscopy (FTIR) analysis indicated that CS binds to Fe(II) or Fe(III) on the surface of nZVI through its functional groups -CONH-, -N-H, and -C-OH and through the - COO − functional group of CMC, forming a bidentate bridge complex. Through experiments with synthetic waters, it was found that the elimination of Cr(VI) was favored by lowering the pH, obtaining the maximum percentage of Cr(VI) removal at pH 5.5. With real waters, it was shown that increasing the mass of NCs also improved the removal of Cr(VI), following a pseudo-second-order adsorption kinetics. The synthesized materials show great potential for applications in environmental remediation, showing good efficiency in the removal of Cr(VI) in wastewater. [ABSTRACT FROM AUTHOR]

Industrial activities are paramount to sustaining the economy in a rapidly developing nation and global powerhouse like India. Leather industries are important in the country's economic map due to the high revenue and employment generation opportunities. Several of these industries contribute largely to environmental pollution. The pollution of the environment is mainly caused by improper disposal of the tannery effluents that are highly rich in hexavalent chromium, a potent human carcinogen. Hexavalent chromium imparts toxic effects on the biotic components, which include plants, animals, and humans. The review portrays the current status of the Indian leather tanning sector and its impact on the Indian economy. The process of chromium tanning and its adverse effects on the environmental biotic components have been briefly discussed. Phytoremediation of these effluents using suitable hyperaccumulating plants has been suggested as an eco-friendly and cost-effective approach for the sustainable restoration of the polluted environment. The mechanism behind the remediation approach and the factors influencing it have been detailed. The manuscript briefly discusses some important advancements in the field of phytoremediation and emerging technologies and concludes by emphasizing further research for sustainable management of tannery wastes. [ABSTRACT FROM AUTHOR]

In this research, activated carbon was prepared from terrestrial moss and utilized as a low-cost adsorbent to remove hexavalent chromium [Cr(VI)] from aqueous solution. The study examined important biosorption factors including initial pH (1–3), contact time (0.5–24 h), initial Cr(VI) concentration (20–400 mg/L), and biosorbent dosage (0.05–0.4 g) to assess their impact on the efficiency of modified terrestrial moss (MAC) in eliminating Cr(VI) from water. The biosorbent capacity was evaluated using different kinetic models and isotherms. The highest removal efficiency of Cr(VI) onto MAC was ascertained as 97.8% at an initial solution pH of 1, MAC dose of 0.2 g, initial Cr(VI) concentration of 50 mg. L−1, and contact time of 15 h. The FTIR analysis revealed the interactions of certain functional groups in the adsorption of chromium ions. The biosorption occurred through the anionic adsorption mechanism and followed the pseudo-second order kinetic model. The experimental data was best fitted with Freundlich isotherm. Furthermore, the thermodynamic studies suggest that the biosorption process is both spontaneous and exothermic. The positive entropy change implied the randomness at the solid–liquid interface. In light of these compelling results, the study recommends the consideration of MAC as an efficient and practical solution for the removal of Cr (VI) from aqueous environments. [ABSTRACT FROM AUTHOR]

The present investigation involved the isolation of a Cr(VI) tolerant fungal (native) isolate (DK04) from Sukinda Chromite Mine, Odisha, exhibiting a tolerance potential of Cr(VI) 300 mg/L for the metal species. The isolate was identified as Trichoderma virens DK04 based on sequencing of the ITS region. The ability of the isolate to reduce and remove Cr(VI) demonstrated that at 100 mg/L concentration of Cr(VI) 99.83% reduction in titer was acheived within 144 hours. SEM, FTIR, EDX, and XRD analysis, reveal deficiency of mycelia pellets for removal of chromium by an adsorption/precipitation mechanism. The isolate DK04, showed promising bioreducing capabilities over a range of temperature (20-400C), pH (5.0-9.0), heavy metals (Zn, Fe, Ni, As) and metabolic inhibitors (phenol and EDTA). The result showed that T. virens isolate has an exceptional potentialto cope with Cr(VI) under stress and has a huge possibility for application performance in Cr(VI) detoxification at Sukinda Chromite Mine as well as other Chromium contaminated sites. [ABSTRACT FROM AUTHOR]

Combined electrokinetic remediation employing reducing agents represents an extensively utilized approach for the remediation of hexavalent chromium (Cr(VI))-contaminated soil. In this investigation, electrokinetic remediation of artificially contaminated kaolin was conducted utilizing a separate circulation system for the anolyte, with a 0.5M solution of acetic acid (HAc) as the electrolyte and foamed iron serving as the anode. The experimental outcomes demonstrated that employing HAc as the electrolyte enhances the electromigration of Cr(VI) and establishes an acidic milieu conducive to the reduction of Cr(VI) by foamed iron, thereby facilitating the rapid reduction of Cr(VI) accumulated in the anolyte through electrokinetic remediation. In the self-prepared contaminated kaolin, the initial concentration of Cr(VI) was 820.26 mg/L. Following the remediation process under optimal experimental conditions, the concentration was significantly reduced to 11.6 mg/L, achieving a removal efficiency of Cr(VI) in the soil of 98.59%. In the optimal experimental setup, the Cr(VI) concentration in the anolyte was reduced to 0.05 mg/L, which is below the EPA's Safe Drinking Water Act standard for Cr(VI) content of 0.1 mg/L. The removal mechanism of Cr(VI) from the electrolyte primarily involves reduction, precipitation, and co-precipitation, with the foamed iron playing a predominant role. HAc and foamed iron exhibit a synergistic effect. The findings of this study substantiate that the integration of foamed iron with HAc is efficacious for the electrokinetic remediation of soil contaminated with Cr(VI). [ABSTRACT FROM AUTHOR]

The toxicity and reactivity of chromium (Cr) depend on its chemical form or oxidation state which directs the significance of chromium speciation. Cr(VI) is a 'Class A' carcinogen whereas Cr(III)) is considered as essential for metabolism. In this work, concentrations of Cr species in different sampling sites of a tannery effluent have been spectroscopically determined. Cr(VI) was determined by UV-visible spectrophotometer through azo dye formation. Total Cr was determined by FAAS while Cr(III) was through subtraction. The Cr(IV) concentration before and after treatment was found in close proximity since the wastewater treatment process was evidently not effective at reducing the level of Cr(IV) in the waste stream (i.e., 3.34 mg/ L versus 3.15 mg/L). The Cr(VI) concentration after treatment (3.15 mg/L) is more than 31 times higher than the permissible limit of WHO (0.1 mg/L). Furthermore, the concentration of Cr(VI) in the downstream of the receiving river (0.59 mg/L) is more than 12 times higher than the upstream (0.046 mg/L) while Cr(III) in the downstream (25.73 mg/L) is more than 50 times higher than the upstream concentration (0.51 mg/L), confirming that the pollution of the river is from the tannery effluent. [ABSTRACT FROM AUTHOR]

Soil contamination, particularly by chromium from industrial effluents, remains a significant global environmental concern. Contaminant removal stands out as a pressing requirement in the current environmental landscape. The increased levels of these contaminants underscore the urgency for effective removal measures. This study focuses on the electrokinetic remediation of chromium-contaminated soil collected from Puliyantangal Lake, Ranipet, Tamil Nadu. Investigating the effects of supply voltage and bone dust amendment on chromium removal efficiency, the research sheds light on the details of this emerging in situ remediation technique. The results indicate that the optimal removal efficiency of hexavalent chromium [Cr(VI)] was achieved at 15 V with a maximum removal of 66.97%. Increased voltage enhanced Cr(VI) remediation through electromigration, while the dissociation of bone dust constituent (hydroxyapatite) positively impacted the removal process through chromium (III) hydroxide [Cr(OH)3] deposition and elevated Cr(VI) reduction. Furthermore, the study reveals a synergistic reduction in total chromium content through electromigration and chemical reduction of chromium species under direct current source application. The decreasing trend of Cr(VI) content from cathode to anode was observed for both 15 and 30 V, with enhanced reduction at higher voltages. Interestingly, the combination of bone dust amendment showed superior Cr(VI) removal efficiency at 15 V, emphasizing the significance of the relationship between voltage and amendment effectiveness. This unique interaction between hindered electromigration and enhanced Cr(VI) reduction holds promise for optimizing electrokinetic remediation strategies, providing valuable insights for future environmental remediation studies. [ABSTRACT FROM AUTHOR]

The objective of the present study was the biosynthesis of nonhazardous and cost-effective silver nanoparticles (AgNPs) using plant extracts of Azadirachta indica (neem), for the removal of hexavalent chromium [Cr (VI)] ions from an aqueous solution. Fourier transform infrared (FT-IR) and energy dispersive X-ray (EDX) spectroscopy characterization results confirmed successful biosynthesis and the presence of elemental silver in the AgNPs. Further, scanning electron microscopy (SEM) and particle size analysis indicated that AgNPs have an amorphous structure and are highly monodispersed. Batch adsorption studies were conducted to investigate the impact of parameters, like pH, time, and initial concentration on Cr (VI) removal efficiency at a fixed AgNP dose of 50 mg and 150 rpm. From the batch study, maximum chromium removal of 87.68% was achieved at an initial concentration of 5 mg/L, pH of 1, and time of 50 min. Results from equilibrium and kinetic study indicated pseudo-second-order reactions kinetics with monolayer coverage. The maximum adsorption capacity of 7.2 mg/g was obtained at an equilibrium time of 50 min and temperature of 30°C. These synthesized AgNPs also displayed significant antibacterial activity against both Gram-positive Bacillus subtilis and Gram-negative Escherichia coli. Based on the results obtained, biosynthesized AgNPs from extracts of A. indica could be utilized for the removal of water pollutants. [ABSTRACT FROM AUTHOR]

Abstract\nNOVELTY STATEMENTThe release of hazardous hexavalent chromium from chromite mining seriously threatens habitats and human health by contaminating water, air, and soil. Vulnerability to hexavalent chromium can result in significant health risks, viz, respiratory issues, gastrointestinal illnesses, skin problems in humans, and a plethora of toxic effects in animals. Moreover, Cr(VI) toxicity can adversely affect plant physiology by inhibiting seed germination, nutrient uptake, cell division, and root development, ultimately impairing growth and vitality. Fortunately, innovative techniques such as phytoremediation and nanotechnology have been developed to address heavy metal contamination, offering a promising solution, mainly through the use of hyperaccumulating plants. Biochar derived from plant waste is widely used and is emerging as a sustainable strategy for remediating Cr(VI) contamination. Biochar is rich in carbon and highly influential in removing Cr(VI) from contaminated soils. This approach addresses immediate challenges while providing a sustainable pathway for environmental rehabilitation in chromium mining. Integrating innovative technologies with nature-based solutions offers a holistic approach to reducing the harmful effects of chromium mining, thus protecting both human well-being and ecosystems. This review highlights the impact of Cr(VI) on different living biotas and further emphasizes the use of plants and plant-based materials for the sustainable remediation of chromite mining regions.Cr(VI) pollution is a primary environmental crisis, and remediation using natural entities such as plants has been widely practiced. Most of these studies have documented the efficiency of plants in the remediation process. The current review emphasizes the different criteria for the selection of Cr(VI) hyperaccumulators. It also outlines the drawbacks of the technique and emphasizes the use of biochar derived from plant biomass as a better alternative. This review provides the latest updates in the field of remediation of Cr(VI) by employing both plants and plant-based biochar. Moreover, it highlights the possible biases and ethical deliberations that need to be taken into due consideration. [ABSTRACT FROM AUTHOR]

Magnetic graphene hybrid has encouraging application in environmental remediation. Herein, adsorption-reduction behavior of Cr (Ⅵ) on Fe 3 O 4 -graphene oxide (Fe 3 O 4 -GO) surface was inspected via both theoretical and experimental methods. In the theoretical level, acidity impact on Cr (Ⅵ) species evolution and Cr (Ⅵ)→Cr (Ⅲ) reduction was investigated with the methodology of equilibrium thermodynamics. In the experimental level, adsorption fittings and spectroscopic tests (FTIR, UV–Vis, XPS) were performed to clarify the adsorbent-adsorbate interaction. Results indicate: (1) Under acidic condition, Cr (Ⅵ) is adsorbed by Fe 3 O 4 -GO in the form of H 2 CrO 4. Afterwards, over three-fifths of H 2 CrO 4 is reduced to Cr (Ⅲ), reaching adsorption percent and quantity 95.53 % and 382.10 mg g−1 in 10 min (2) Under basic condition, Cr (Ⅵ) is adsorbed in the form of CrO 4 2− without reduction. In the context of environmental remediation, two special implications are thereby procured. (1) Under acidic condition, Cr (Ⅵ) removal efficiency at the first cycle is maximized, while magnetic recovery is deteriorated, resulting in unsatisfactory cyclic performance. (2) Under basic condition, Cr (Ⅵ) removal efficiency is inferior to that under acidic condition, while magnetic recovery is guaranteed, leading to satisfactory cyclic performance. Exploration of this work provides reference especially for developing Fe 3 O 4 -GO architecture towards efficient sequestering of hexavalent chromium. Adsorption-reduction behavior of Cr (Ⅵ) on Fe 3 O 4 -GO surface(a) Illumination of redox reaction between Cr (Ⅵ) and Fe 3 O 4 given by thermodynamic calculation. Under acidic condition: spontaneous reaction H2CrO4+3Fe 2+ +6H + ⇌Cr 3+ +3Fe 3+ +4H2O owing to highly negative standard molar Gibbs free energy change. Under basic condition, non spontaneous reaction CrO4 2− +3Fe 2+ +4H2O⇌Cr(OH)4 - +3Fe 3+ +4OH − owing to highly positive standard molar Gibbs free energy change. (b) Adsorption-reduction behavior of Cr (Ⅵ) on Fe 3 O 4 -GO surface deciphered by Cr (Ⅵ) species distribution and XPS test. Under acidic condition: five small orange balls symbolizing H 2 CrO 4 adsorbed onto the surface of the big green ball representing Fe 3 O 4 -GO. Subsequently, three out of five small orange balls were transformed into small violet balls representing Cr3+, approaching the molar ratio Cr (Ⅲ)/Cr (Ⅵ) = 1.52 of the sample Fe 3 O 4 -GO-Cr as determined by XPS test (Fig. 8). The big blue ball represents Fe 3 O 4 -GO oxidized by H 2 CrO 4. Under basic condition: five small pink balls symbolizing CrO 4 2− adsorbed onto the surface of the big green ball representing Fe 3 O 4 -GO ensued by no reduction, as confirmed by thermodynamic analysis. [Display omitted] • Adsorption-reduction behavior of Cr (Ⅵ) on Fe 3 O 4 -graphene oxide surface is inspected. • In acidic media, H 2 CrO 4 is adsorbed, three-fifths of which is reduced to Cr (Ⅲ). • In basic media, CrO 4 2− is adsorbed without reduction. • Superior Cr (Ⅵ) removal efficiency but unsatisfactory cyclic performance in acidic media. [ABSTRACT FROM AUTHOR]

In this study, the porous graphite phase carbon nitride photocatalyst (P-g-C3N4) is prepared by the CaCO3 template method, and then P-g-C3N4/T-polyethylene terephthalate (T-PET) catalytic fibre is prepared by the padding method. P-g-C3N4 can provide more active sites than g-C3N4 as proved by the Brunauer–Emmett–Teller and the UV–Visible diffuse reflectance test. P-g-C3N4 powder catalyst successfully supports PET fibre as proved by scanning electron microscope, Fourier infrared spectroscopy and X-ray diffraction spectroscopy. The photocatalytic performance of P-g-C3N4/T-PET catalytic fibre is tested by constructing a single hexavalent chromium or hexavalent chromium/organic pollutant binary pollution system. The potential application value of P-g-C3N4/T-PET catalytic fibre is further explored by simulating the complex actual water environment. After five recycles, P-g-C3N4/T-PET catalytic fibre shows good catalytic performance. The mechanism of P-g-C3N4/PET photocatalytic degradation of organic pollutants is proposed through the capture agent experiment and electron paramagnetic resonance spectroscopy. Among them, •O2− is the most important active species of P-g-C3N4 catalytic fibre, which is used for the oxidation of organic pollutants. At the same time, photoelectrons generated by the catalytic fibre are used to reduce hexavalent chromium. The efficiency of P-g-C3N4 to remove pollutants is improved by using PET fibre as a carrier, which not only solves the problem of difficult recovery of powder catalysts but also provides more active sites. [ABSTRACT FROM AUTHOR]

Photoreduction is recognized as a desirable treatment method for hexavalent chromium (Cr(VI)). However, it has been limited by the intermittent solar flux and limited light absorption. In this work, a novel Z-scheme photocatalyst combining a covalent organic framework (COF) with Eu2+, Dy3+ co-doped Sr2MgSi2O7 (Sr2MgSi2O7:Eu2+, Dy3+) is synthesized, which shows the high spectral conversion efficiency and works efficiently in both light irradiation and dark for Cr(VI) reduction. Sr2MgSi2O7:Eu2+, Dy3+ serves as both an electron transfer station and active sites for COF molecule activation, thus resulting in 100% photoreduction of Cr(VI) (50 mL, 10 mg/L) with high light stability and over 1 h dark activity. Moreover, the XPS and FT-IR analyses reveal the existence of functional groups (Si-OH on Sr2MgSi2O7:Eu2+, Dy3+, and -NH- on COFTP-TTA) on the composited catalyst as active sites to adsorb the resultant Cr(III) species, demonstrating a synergistic effect for total Cr removal. This work provides an alternative method for the design of a round-the-clock photocatalyst for Cr(VI) reduction, allowing a versatile solid surface activation for establishing a more energy efficient and robust photocatalysis process for Cr pollution cleaning. [ABSTRACT FROM AUTHOR]

The present work focused on the isolation of a bacterial strain multi-resistant to heavy metals with a high potential for reducing hexavalent chromium (Cr(VI)) and studied its Cr(VI) removal performance in immobilized state and the mechanisms involved. Bacterial isolate was identified as Bacillus safensis CCMM B629 (B. safensis), is able to completely reduce 50, 100 and 200 mg/L of Cr(VI) after 24, 48 and 120 h, respectively under optimized conditions of pH 7 and 30°C. The coexistence of nitrates, cadmium and mercury inhibits reduction, while copper and iron significantly improve removal efficiencies. Additionally, the presence of electron donors such as glycerol, glucose and citrate significantly increases bioreduction rate. Cells immobilized in alginate beads successfully reduced Cr(VI) compared to free cells, showing the performance of biobeads in Cr(VI) reduction. Membrane fraction exhibited highest rate of Cr(VI) reduction (65%) compared to other cellular components, indicating that Cr(VI) reduction occurred primarily in cell membrane. Further characterization of Cr(VI) removal by B. safensis cells using scanning electron microscopy and energy-dispersive X-ray (SEM-EDX) analysis showed its ability to reduce and adsorb Cr(VI), confirming that hexavalent chromium was taken up successfully on bacterial cell surfaces. Based on Fourier transform infrared spectroscopy analysis (FTIR), hydroxyl, carboxyl, amide, and phosphoryl functional groups participated in combination with Cr(III). In conclusion, B. safensis is a bacterium with great potential for Cr(VI) removal, and it is a promising and competitive strain for use in bioremediation of Cr(VI) contaminated industrial effluents. [ABSTRACT FROM AUTHOR]

Chromium and arsenic are among the priority pollutants to be controlled by regulatory and health agencies due to their ability to accumulate in food chains and the harmful effects on health resulting from the ingestion of food contaminated with metals and metalloids. In the present work, four biohybrid membrane systems were developed as alternatives for the removal of these pollutants, three based on polyvinyl alcohol polymeric mesh (PVA, PVA-magnetite, PVA L-cysteine) and one based on polybutylene adipate terephthalate (PBAT), all associated with bioremediation agents. The efficiency of the bioassociation process was assessed through count methods and microscopy. The removal capacity of these systems was evaluated in synthetic liquid medium, both in the absence and in the presence of soybean (Glycine max L.) seedlings. The content of chromium and arsenic was also analyzed in aerial and hypogeous tissues of seedlings grown on contaminated solid substrate. PVA and PVA-magnetite biohybrid membranes showed the highest removal rates, between 57 and 75% of the initial arsenic content and more than 80% of the initial chromium content after 48 h of treatment, when evaluated in synthetic liquid media with initial concentrations of 2.5 ppm of pentavalent arsenic and 5 ppm of hexavalent chromium, both in presence and absence of seedlings. PVA and PBAT promoted a significant reduction of arsenic translocation to the aerial parts, generally edible, of this crop of agronomic interest. The systems tested showed a high potential for biotechnological applications in matrices affected by the presence of arsenic and chromium. [ABSTRACT FROM AUTHOR]

Background and aims: Heavy metals pollution, particularly by hexavalent chromium, is a topic of global concern due to its high toxicity and environmental persistence. Phytoremediation emerges as a nature-based economic technology for the recovery of environments contaminated by metals. In the case of water bodies, aquatic macrophytes such as Salvinia minima Baker are excellent candidates as remedial species. To optimize its use, it is important the identification of efficient and reliable biomarkers. The objective of this work was to carry out a temporal analysis of different biochemical parameters to identify both biomarkers of exposure to Cr(VI) and the most appropriate time for their analysis in S. minima plants under laboratory conditions. M&M: Specimens of S. minima were cultured in the presence or absence of hexavalent chromium for seven days under controlled light and temperature conditions. Tissue and culture solution samples were taken at 0, 2, 4 and 7 days. The levels of H2O2, malondialdehyde, soluble and insoluble phenols and sucrose were quantified in floating pinnae and submerged rachis. Remaining Cr(VI) was determined in the treatment solution. All determinations were performed spectrophotometrically. Results: The results allowed us to identify, among the selected parameters, early (malondialdehyde), medium-term (sucrose and insoluble phenols) and late (hydrogen peroxide) biomarkers. Conclusions: The physiological implications of the observed variations are analyzed and discussed. [ABSTRACT FROM AUTHOR]

Hexavalent chromium (Cr(VI)) exposure has been linked with gastrointestinal toxicity, whereas the molecular pathways and key targets remain elusive. Computational toxicology analysis predicted the correlation between protein phosphatase 2A (PP2A) and genes regarding Cr(VI)-induced intestinal injury. Here, we generated a mouse model with intestinal epithelium-specific knock out of Ppp2r1a (encoding PP2A Aa subunit) to investigate the mechanisms underlying Cr(VI)- induced small intestinal toxicity. Heterozygous (HE) mice and matched WT littermates were administrated with Cr(VI) at 0, 5, 20, and 80 mg/l for 28 successive days. Cr(VI) treatment led to crypt hyperplasia, epithelial cell apoptosis, and intestinal barrier dysfunction, accompanied by the decline of goblet cell counts and Occludin expression in WT mice. Notably, these effects were aggravated in HE mice, indicating that PP2A Aa deficiency conferred mice with susceptibility to Cr(VI)-induced intestinal injury. The combination of data analysis and biological experiments revealed Cr(VI) exposure could decrease YAP1 phosphorylation at Ser127 but increase protein expression and activity, together with elevated transcriptional coactivator with PDZ-binding motif protein driving epithelial crypt cells proliferation following damage, suggesting the involvement of Hippo/YAP1 signaling pathway in Cr(VI)-induced intestinal toxicity. Nevertheless, the enhanced phosphorylation of YAP1 in HE mice resulted in proliferation/repair defects in intestinal epithelium, thereby exacerbating Cr(VI)-induced gut barrier dysfunction. Notably, by molecular docking and further studies, we identified urolithin A, a microbial metabolite, attenuated Cr(VI)-induced disruption of intestinal barrier function, partly by modulating YAP1 expression and activity. Our findings reveal the novel molecular pathways participated in Cr(VI)-caused small intestinal injury and urolithin A could potentially protect against environmental hazards-induced intestinal diseases. [ABSTRACT FROM AUTHOR]

For a long time, the leather industry has considered the chromium tanning process to be the easiest and fastest way to treat raw hides and transform them into valuable products. In the last few decades, increasing attention has been paid to the potential oxidation of the trivalent chromium in tanned leather. This happens for many reasons, such as the quality of the tanning agent or the adoption of good manufacturing practices. Anyway, the main problem, which is difficult to solve, is the sensibility of the free residual chromium tanned leather, which is high enough for possible harmful activity. Given this scenario, this work proposes a solution to decrease hexavalent chromium formation by using antioxidants during the leather tanning process. In this regard, a screening work was started, to find the worst-case scenario for trivalent chromium oxidation. To do this, commercial tanning products were employed, especially fatliquoring agents, which, in some cases, are the main source that could easily react with ROS (Reactive Oxygen Species) to drive chromium oxidation. After the determination of conditions, different groups of common antioxidants were tested to analyse the antioxidation performances and their possible use in the chromium-based tanning process. The results underline the efficient action of the antioxidants studied, paving the way for some interesting perspectives to limit the drawbacks of chromium tanned leather. [ABSTRACT FROM AUTHOR]

Hexavalent chromium [Cr(VI)] is an established human lung carcinogen, but the carcinogenesis mechanism is poorly understood. Chromosome instability, a hallmark of lung cancer, is considered a major driver of Cr(VI)-induced lung cancer. Unrepaired DNA double-strand breaks are the underlying cause, and homologous recombination repair is the primary mechanism preventing Cr(VI)-induced DNA breaks from causing chromosome instability. Cell culture studies show acute Cr(VI) exposure causes DNA double-strand breaks and increases homologous recombination repair activity. However, the ability of Cr(VI)-induced DNA breaks and repair impact has only been reported in cell culture studies. Therefore, we investigated whether acute Cr(VI) exposure could induce breaks and homologous recombination repair in rat lungs. Male and female Wistar rats were acutely exposed to either zinc chromate particles in a saline solution or saline alone by oropharyngeal aspiration. This exposure route resulted in increased Cr levels in each lobe of the lung. We found Cr(VI) induced DNA double-strand breaks in a concentration-dependent manner, with females being more susceptible than males, and induced homologous recombination repair at similar levels in both sexes. Thus, these data show this driving mechanism discovered in cell culture indeed translates to lung tissue in vivo. [ABSTRACT FROM AUTHOR]

• Repeated-measure design in workers exposed to chromate was conducted. • Blood chromium was positively correlated with liver enzyme levels and bilirubin levels, suggesting that chromate exposure may cause liver injury. • Blood chromium was positively correlated with systemic inflammatory markers PLT and PLR, suggesting that chromate exposure may lead to increased systemic inflammation. • Systemic inflammatory markers PLT and PLR mediate the increase of liver enzymes and bilirubin induced by chromium exposure, with the mediating ratio ranging from 8.26% to 15.58%. Hexavalent chromium and its compounds are prevalent pollutants, especially in the work environment, pose a significant risk for multisystem toxicity and cancers. While it is known that chromium accumulation in the liver can cause damage, the dose-response relationship between blood chromium (Cr) and liver injury, as well as the possible potential toxic mechanisms involved, remains poorly understood. To address this, we conducted a follow-up study of 590 visits from 305 participants to investigate the associations of blood Cr with biomarkers for liver injury, including serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin (TBIL), and direct bilirubin (DBIL), and to evaluate the mediating effects of systemic inflammation. Platelet (PLT) and the platelet-to-lymphocyte ratio (PLR) were utilized as biomarkers of systemic inflammation. In the linear mixed-effects analyses, each 1-unit increase in blood Cr level was associated with estimated effect percentage increases of 0.82% (0.11%, 1.53%) in TBIL, 1.67% (0.06%, 3.28%) in DBIL, 0.73% (0.04%, 1.43%) in ALT and 2.08% (0.29%, 3.87%) in AST, respectively. Furthermore, PLT mediated 10.04%, 11.35%, and 10.77% increases in TBIL, DBIL, and ALT levels induced by chromate, respectively. In addition, PLR mediated 8.26% and 15.58% of the association between blood Cr and TBIL or ALT. These findings shed light on the mechanisms underlying blood Cr-induced liver injury, which is partly due to worsening systemic inflammation. [Display omitted] [ABSTRACT FROM AUTHOR]

Chromite ore processing residue (COPR), which is created during the chromite preparation process of chromite compounds, is considered hazardous waste because it contains chromium trivalent and chromium hexavalent. Recently, the harmless disposal of COPR has received a lot of research interest. COPR is a type of resource attributable to its abundant content of chromium, iron, aluminum, etc. This article starts from the main sources, properties, and pollution characteristics of COPR. It summarizes the methods and approaches used by scholars in recent years to handle COPR: chemical reduction, dry detoxification, pyrolysis, mineralization, solidification/stabilization, biotechnology, electrochemical methods, and resource utilization, achieving harmless treatment of COPR. Among them, research on resource utilization stands out, not only improving resource utilization efficiency but also reducing environmental pollution. This provides new ideas and directions for our future treatment of COPR. [ABSTRACT FROM AUTHOR]

The efficient removal of Cr(VI) from water is a crucial environmental concern, and in this study, the focus was on addressing this issue by investigating a new flower-like cerium phosphate polyaniline nanocomposite (CePO4-PANI) material. This material was synthesized using an in situ oxidative polymerization method, resulting in a flower-like morphology that was confirmed through field emission scanning electron microscopy and transmission electron microscopy images. The adsorption of Cr(VI) onto the material followed the pseudo-second-order kinetic model and the Langmuir isotherm model, with a high adsorption capacity of 129.87 ± 2.1 mg g−1 at room temperature in a wide pH range of 2 to 6. The CePO4-PANI nanocomposite is a promising adsorbent for the treatment of Cr(VI), with high tolerance to co-anions and efficient regeneration after multiple adsorption-desorption cycles. XPS spectra revealed the simultaneous adsorption of Cr(VI) and in situ chemical reduction to Cr(III) via electrostatic attractions and chelation methods. Its unique flower-like morphology, coupled with its impressive adsorption capacity, co-anion tolerance, and efficient regeneration, make it a promising alternative to existing technologies for water treatment. [ABSTRACT FROM AUTHOR]

Prolonged use of the chromate [Cr(VI)]-contaminated water originates severe health problems for the public. Thus, the societal urgency is a reusable and cost-effective material for efficient scavenging of Cr(VI) from contaminated industrial wastewater. Aiming this, we had targeted to prepare some cheap and effective materials for scavenging Cr(VI) from the contaminated water. Herein, we report the preparation of hydrous cerium-copper oxide (HCCO) with some tailored compositions and employed toward the abstraction of chromate from water solution. The HCCO (Ce: Cu = 1:4, mole/mole) has shown the highest Cr(VI) scavenging capacity. Experimentally, highest Cr(VI) abstraction efficiency is recorded at pH ~ 3.0 (508.853 mg. g−1 at 303 K). Kinetically, the Cr(VI) scavenging reaction with HCCO surfaces agrees better with the pseudo second-order model (R2 = 0.987) equation and the equilibrium Cr(VI) distribution data explain the Freundlich isotherm model (R2 = 0.998) equation, which anticipates the multi-layered adsorption on heterogeneous sites of the adsorbent. A negative value of the Gibbs free energy change indicates that the Cr(VI) adsorption over HCCO surfaces is spontaneous. The positive enthalpy change indicates the endothermic nature of the said reaction. HIGHLIGHTS: One-pot synthesis of hydrous Ce(IV)-Cu(II) oxide (HCCO) and characterizations. Systematic Cr(VI) scavenging from modeled ground water with HCCO. Best fit pseudo-second-order kinetic model, implying the chemisorption mechanism. Very high amount of Cr(VI) scavenging at ambient condition reported to be 508.85 mg.g−1. Coulombic interaction between HCCO and Cr(VI) is responsible for scavenging Cr(VI). [ABSTRACT FROM AUTHOR]

Semi-rigid V-shaped bis(N,N-trimellitoyl)-4,4′-oxydianiline linker was designed to construct a novel mesoporous cobalt (II) metal organic framework (Co-MOF). Optical band gap of 3.23 eV was obtained using a Tauc formula, which confirms the semiconducting property of the synthesized Co-MOF. Further, the resulting Co-MOF, as photocatalyst, was investigated in environmental application for the reduction of toxic Cr (VI) to less toxic Cr (III) as well as in the degradation of organic rhodamine B (Rh B) dye in an aqueous medium under natural sunlight. As pH value is essential for the Cr (VI) reduction reaction, thus control experiment was conducted in the acidic pH range 2–6, where 90.76, 77.23 and 37.43% of reduction was observed at pH of 2, 4 and 6, respectively. Furthermore, the degradation of Rh B dye was also performed, where 98.89% degradation obtained within 90 min. The recyclability test was also assessed for Cr (VI) reduction reaction at pH 2 and for degradation of Rh B. [ABSTRACT FROM AUTHOR]

This study investigated the colour and corrosion resistance of a commercial sulphate-based versus a chloride-based trivalent chromium electrodeposit, as well as the effects of post-treatment in a hexavalent chromium passivate solution. Surface composition and depth profiles were analysed using X-ray Photoelectron Spectroscopy (XPS). The factors influencing the appearance and corrosion performance in a Russian Mud Test are discussed. [ABSTRACT FROM AUTHOR]

Anthropogenic activities and increasing human population has led to one of the major global problems of heavy metal contamination in ecosystems and to the generation of a huge amount of waste material biomass. Hexavalent chromium [Cr(VI)] is the major contaminant introduced by various industrial effluents and activities into the ecosystem. Cr(VI) is a known mutagen and carcinogen with numerous detrimental effects on the health of humans, plants, and animals, jeopardizing the balance of ecosystems. Therefore, the remediation of such a hazardous toxic metal pollutant from the environment is necessary. Various physical and chemical methods are available for the sequestration of toxic metals. However, adsorption is recognized as a more efficient technology for Cr(VI) remediation. Adsorption by utilizing waste material biomass as adsorbents is a sustainable approach in remediating hazardous pollutants, thus serving the dual purpose of remediating Cr(VI) and exploiting waste material biomass in an eco- friendly manner. Agricultural biomass, industrial residues, forest residues, and food waste are the primary waste material biomass that could be employed, with different strategies, for the efficient sequestration of toxic Cr(VI). This review focuses on the use of diverse waste biomass, such as industrial and agricultural by-products, for the effective remediation of Cr(VI) from aqueous solutions. The review also focuses on the operational conditions that improve Cr(VI) remediation, describes the efficacy of various biomass materials and modifications, and assesses the general sustainability of these approaches to reducing Cr(VI) pollution. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Inorganic Analytical Chemistry / Zhongguo Wuji Fenxi Huaxue is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Inorganic Analytical Chemistry / Zhongguo Wuji Fenxi Huaxue is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Hexavalent chromium (Cr(VI)) ions are among the most common hazardous metals that pose a serious risk to human health, causing human carcinogenesis and chronic kidney damage. In this study, a point-of-care testing (POCT) kit is proposed for Cr(VI) ions detection at room temperature. The kit contains a hydrophobic parafilm, a nylon membrane to resist outflow, and a hydrophilic Whatman filter paper suitable for coating the fluorescent graphitic carbon nitride sheet (g-C3N4). Crystalline, nano-porous, blue-emitting g-C3N4 was produced by pyrolysis utilizing carbohydrazide. The electrostatic interactions between the g-C3N4 and Cr(VI) ions inhibit the fluorescence behavior. The POCT kit can be used for on-site Cr(VI) ion detection dependent upon the blue emission value. The detection limit was attained at 4.64 nM of Cr(VI) ions. This analytical methodology was utilized on real samples from tap, pond, river, and industrial wastewater. This POCT kit can be a useful alternative for on-site detection of Cr(VI) ions. [ABSTRACT FROM AUTHOR]

Electric arc furnace (EAF) slag is a coproduct of steel production used primarily for construction purposes. Some applications of EAF slag result in residential exposures by incidental ingestion and inhalation of airborne dust. To evaluate potential health risks, an EAF slag characterization program was conducted to measure concentrations of metals and leaching potential (including oral bioaccessibility) in 38 EAF slag samples. Arsenic, hexavalent chromium, iron, vanadium, and manganese (Mn) were identified as constituents of interest (COIs). Using a probabilistic risk assessment (PRA) approach, estimated distributions of dose for COIs were assessed, and increased cancer risks and noncancer hazard quotients (HQs) at the 50th and 95th percentiles were calculated. For the residents near slag‐covered roads, cancer risk and noncancer HQs were <1E − 6 and 1, respectively. For residential driveway or landscape exposure, at the 95th percentile, cancer risks were 1E − 6 and 7E − 07 based on oral exposure to arsenic and hexavalent chromium, respectively. HQs ranged from 0.07 to 2 with the upper bound due to ingestion of Mn among children. To expand the analysis, a previously published physiologically based pharmacokinetic (PBPK) model was used to estimate Mn levels in the globus pallidus for both exposure scenarios and further evaluate the potential for Mn neurotoxicity. The PBPK model estimated slightly increased Mn in the globus pallidus at the 95th percentile of exposure, but concentrations did not exceed no‐observed‐adverse‐effect levels for neurological effects. Overall, the assessment found that the application of EAF slag in residential areas is unlikely to pose a health hazard or increased cancer risk. [ABSTRACT FROM AUTHOR]

At present, developing countries, including Ethiopia, are undergoing a phase of industrial transformation. As a result, there has been a significant rise in the presence of harmful pollutants in groundwater. The release of deleterious heavy metals, such as Cr (VI), into the surrounding ecosystem is a result of various industrial operations. The present investigation utilized activated sodium bentonite clay as an adsorbent agent to facilitate the elimination of Cr (VI). The clay was subjected to acidification and thermal modification techniques to enhance its adsorption capacity. The investigation involved an examination of the particular surface area, capacity for cation exchange, crystalline properties, functional groups on the surface, and structural morphology. The methylene blue test method was employed to ascertain the maximum specific surface area and cation exchange capacity of the adsorbent, which were found to be 512 m2/g and 65.5 meq/100 g, respectively. The clay mineral composition was analyzed using X‐ray diffraction, which indicated that the primary constituent was montmorillonite. The presence of impurities such as quartz, feldspar, muscovite, cristobalite, and hematite was also detected. The study employed response surface methodology, Box–Benkhen design (RSM‐BBD) to investigate the impact of operational parameters, including agitation time, initial Cr (VI) concentration, and adsorbent dosage. Under the optimal conditions, a removal efficiency of 98.05% was achieved for Cr (VI) for a contact duration of 120 min, a dosage of 3.913 g/L, and an initial concentration of 50 mg/L. The sodium bentonite clay that was activated demonstrated a maximum capacity for adsorption of 22.72 mg/g in regards to the adsorption of Cr (VI). The experimental data were best fitted by the Langmuir isotherm, which exhibited a correlation coefficient of 0.9699. The adsorption kinetics were assessed and determined to adhere to a pseudo‐second‐order pattern, exhibiting a coefficient of determination (R2) value of 0.999. Furthermore, the activated sodium bentonite clay demonstrated remarkable potential for repeated utilization in the adsorption of Cr (VI) ions in aqueous solutions. [ABSTRACT FROM AUTHOR]