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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]

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]

ABSTRACT Hexavalent chromium (Cr(VI)) has attracted great considerations due to their high toxicity, teratogenicity, and carcinogenicity. In this study, four Zr‐MOFs were synthesized and used to comparative study their catalytic performances of oxalic acid (OA) for Cr(VI) removal. Results showed that the removal efficiency for Cr(VI) was reached 65.91%, 78.64%, 53.58%, and 96.32% by MOF‐525, MOF‐525(Co), MOF‐525(Zn), and MOF‐525(Fe) in the presence of OA when the initial Cr(VI) concentration was 100 mg·L−1, respectively. The single‐factor experiments for further improving the Cr(VI) removal by MOF‐525(Fe)/OA demonstrated that the optimal conditions were OA dosage of 790 mg·L−1, and MOF‐525(Fe) dosage of 500 mg·L−1 and pH of 2.0, and the MOF‐525(Fe)/OA system could be used to treat Cr(VI)‐containing wastewater at concentrations below 50 mg·L−1. Ionic strength studies indicated that Na+, K+, Mg2+, Cl−, and SO42− had little effect on the catalytic reduction of Cr(VI), while high concentrations of Ca2+ (0.10 and 0.25 mol·L−1), NO3− (0.25 mol·L−1), and PO43− (0.25 mol·L−1) had significant inhibition effects. The reusability experiments showed that the stability of MOF‐525(Fe) was excellent, and it could be used for potential applications. Based on the results of Fourier transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), and Electron Paramagnetic Resonance spectrometer (EPR), the possible reduction mechanism of Cr(VI) by MOF‐525(Fe)/OA system was proposed as follows: The complexation of OA with Fe3+ was first complexed to produce Fe2+ and CO2•−, then Cr(VI) was combined with Zr–O and Fe–O clusters in MOF‐525(Fe) to obtain activation energy, and the reduction ability was enhanced at the same time; finally, Cr(VI) obtained electrons from CO2•− and was sequentially reduced as Cr(V) and Cr(III). [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]

Chromium(VI) is one of the most toxic metal ions as it can bioaccumulate and its excessive assimilation may result in anaemia, nervous system failure, kidney damage, cancers of the digestive tract and lungs. In this study a polypyrrole (PPy) modified with histidine (His) by in situ polymerisation technique was investigated for the removal of Cr(VI) from aqueous and characterised by means of Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy/energy dispersive X-ray spectroscopy (FE-SEM/EDS), high resolution-transmission electron microscopy (HR-TEM) and X-ray photoelectron spectroscopy (XPS).The influence of solution pH, adsorption time, initial adsorption concentration, temperature and coexisting ions on its adsorption were investigated. The results showed that the optimum adsorption pH was 2.0 with the adsorption being endothermic and chemisorption in nature. Mono-layer adsorption was witnessed as the Langmuir isotherm best described the process with a maximum adsorption capacity 274.73 mg g−1 at 25 °C. Although the removal of Cr(VI) was the primary drive, the reduction of Cr(VI) to Cr(III) during treatment turned out to be very significant to avoid secondary pollution. The adsorption mechanisms were mainly ion exchange, electrostatic attractions, complexation, chelation reactions with protonated histidine sites and reduction. Remarkably, the His-PPy nanocomposite exhibited an exceptional removal for Cr(VI) ions after three cycles of adsorption–desorption (over 99%) suggesting the adsorbent's exceptional recyclability. The adsorption equilibrium was attained from 60 to 150 min and best described by pseudo-second-order kinetics. The high adsorption efficiency, stability and selectivity makes the His-PPy nanocomposite adsorbent potentially suitable for large-scale Cr(VI) ions removal from water. [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]

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.)

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]

Effective management and remediation strategies are crucial to minimize the impacts of both organic and inorganic contaminants on environmental quality and human health. This study investigates a novel approach utilizing cotton shell activated carbon (CSAC), rice husk activated carbon (RHAC), and wasp hive activated carbon (WHAC), produced through alkali treatment and carbonization under N2 atmosphere at 600 °C. The adsorption capacities of biomass-derived mesoporous activated carbons (CSAC, RHAC, WHAC) alongside macroporous commercial activated carbons (CAC) were evaluated for removing rhodamine B (Rh B) and hexavalent chromium (Cr6+). The CSAC exhibits remarkable adsorption efficiency (255.4 mg.g−1) for Cr(VI) removal, while RHAC demonstrates superior efficacy (174.2 mg.g−1) for Rh B adsorption. Investigating various optimal parameters including initial pH (pH 3 for Cr and pH 7 for Rh B), catalyst dosage (200 mg.L−1), and initial concentration (20 mg.L−1), the Redlich-Peterson isotherm model is applied to reveal a hybrid adsorption mechanism encompassing monolayer (chemisorption) and multilayer (van der Waals adsorption) processes. Kinetic analysis highlights the pseudo-second-order and Elovich models as the most suitable, suggesting physiochemisorption mechanisms. Thermodynamic analysis indicates the endothermic nature of the adsorption process, with increased randomness at the solid-solution interface. Isosteric heat investigations using Clausius-Clapeyron, Arrhenius, and Eyring equations reveal a heterogeneous surface nature across all activated carbons. Further confirmation of Rh B and Cr(VI) adsorption onto activated carbons is provided through FTIR, FESEM, and EDAX analysis. This study highlights the innovation and promise of utilizing biomass-derived activated carbons for effective pollutant removal. [ABSTRACT FROM AUTHOR]

In situ CO2 mixing technology is a potential technology for permanently sequestering CO2 during concrete manufacturing processes. Although it has been approved as a promising carbon capture and utilisation (CCU) method, its effect on the leachability of heavy metals from cementitious compounds has not yet been studied. This study focuses on the effect of in situ CO2 mixing of cement paste on the leaching of hexavalent chromium (Cr(VI)). The tank leaching test of the CO2 mixing cement specimen resulted in a Cr(VI) cumulative leaching of 0.614 mg/m2 in 28 d, which is ten times lower than that of the control mixing specimens. The results in thermogravimetric analysis indicated that a relatively significant amount of CrO42− is immobilised as CaCrO4 during the CO2-mixing, and a higher Cr–O extension is observed in the Fourier transform infrared spectra. Furthermore, a portion of the monocarboaluminate is inferred from microstructural analyses to incorporate CrO42− ions. These results demonstrate that in situ CO2 mixing is beneficial not only in reducing CO2 emissions, but also in controlling the leaching of toxic substances. [ABSTRACT FROM AUTHOR]

Simple Summary: Hexavalent chromium (Cr(VI)) poses a considerable threat to aquatic ecosystems and aquatic organisms due to pollution. This study explored the toxic effects of Cr(VI) on the primary hepatocytes of the Reeves' turtles (Mauremys reevesii) by isolating the hepatocytes. The results showed that Cr(VI)-treated cells exhibited increased antioxidant enzyme activity and reactive oxygen species levels. ATP levels decreased, and related mitochondrial dynamics genes underwent changes. Ultimately, this led to apoptosis and autophagy in the cells. These findings indicate that Cr(VI) pollution is a critical health issue, offering fresh perspectives and guiding principles for the protection of turtles. Hexavalent chromium (Cr(VI)), a pervasive industrial contaminant, is highly toxic to both humans and animals. However, its effects on turtles are largely unexplored. Our study aimed to investigate the toxic effects of Cr(VI) on the Reeves' turtles (Mauremys reevesii) primary hepatocytes. We exposed hepatocytes to two concentrations (25 μM and 50 μM) of Cr(VI) for 24 h. The results showed that compared to controls, Cr(VI)-treated cells showed elevated antioxidant enzyme activity (catalase (CAT) and superoxide dismutase (SOD)) and increased reactive oxygen species (ROS) levels. Adenosine triphosphatae (ATP) levels decreased, indicating mitochondrial dysfunction. Additionally, we found significant changes in mitochondrial dynamics related genes, with downregulation of mitofusin 2 (Mfn2) and silent information regulator 1 (SIRT1) and a decrease in sirtuin 3 (SIRT3) and tumor protein 53 (p53) mRNA levels. Annexin V-FITC fluorescence staining-positive cells increased with higher Cr(VI) concentrations, marked by elevated bcl-2-associated X protein (Bax) and cysteinyl aspartate specific proteinase (Caspase3) mRNA levels and reduced B-cell lymphoma-2 (Bcl2) expression. Autophagy-related genes were also affected, with increased microtubule-associated protein 1 light chain 3 (LC3-I), microtubule-associated protein light chain 3II (LC3-II), unc-51-like autophagy-activating kinase 1 (ULK1), and sequestosome 1 (p62/SQSTM1) mRNA levels and decreased mammalian target of rapamycin (mTOR) and Beclin1 expression. Taken together, Cr(VI) promotes cell apoptosis and autophagy in turtle hepatocytes by inducing oxidative stress and disrupting mitochondrial function. These findings highlight the serious health risks posed by Cr(VI) pollution and emphasize the need for protecting wild turtle populations. [ABSTRACT FROM AUTHOR]

We introduce an enhanced light-harvesting MoS2-based nanocomposite exhibiting improved solar light induced photocurrent generation, both in solution and solid phases. The MoS2-CdS composite was synthesized via easy to achieve, cost effective, two-step solution process for the photocatalytic potassium dichromate [Cr(VI)] reduction and photocurrent generation in thin-film optoelectronic devices. Incorporating 10 wt% MoS2 into the composite increased the degradation efficiency of CdS from 43.9 to 91.9%. Furthermore, the MoS2-CdS composite demonstrated a 2.88-fold increase in the degradation rate constant and a 2.15% enhancement in the apparent quantum yield compared to controlled CdS. Additionally, the electrical power consumption per order decrease in Cr(VI) reduced from 25.74 kWh m−3 for controlled CdS to 9 kWh m−3 aimed at 10 wt% MoS2-CdS composite, indicating optimal synergy between the counterparts of MoS2-CdS in its composite. The resulting thin-film device with 10 wt% MoS2-CdS exhibited robust photocurrent generation and nonlinear I–V characteristics under solar illumination, attributed to the unique electronic properties of the MoS2-CdS heterojunction, influencing carrier transport via band alignment and interface carrier trapping effects. Moreover, photocurrent generation increased linearly with illumination intensity, and dynamic photo response studies revealed rapid photocurrent generation under illumination. Furthermore, the optoelectronic key parameters of CdS, including photosensitivity, photoresponsivity, and detectivity, were enhanced by factors of 5.09, 3.33, and 12.3, respectively, upon composite formation with MoS2. This study offers novel insights into developing high-performance and cost-effective bimetallic sulfide photocatalysts for efficient solar light-induced photocurrent generation in both solution and solid phases. [ABSTRACT FROM AUTHOR]

The Cr(VI) removal efficiency of a Brazilian Oxisol collected from the A horizon (15.2% iron oxides, 4.6% organic matter, pH 4.3) was assessed and compared with synthesized iron minerals (SM), to mitigate contamination as a nature-based solution. Batch tests revealed that Cr(VI) removal efficiency was higher and faster for SM than for Oxisol: to remove ∼ 100% Cr(VI) from a solution containing 5 mg L− 1Cr(VI), SM took 24 h, while for the same concentration Oxisol removed 80% Cr(VI) in 30 days. At a higher concentration (30 mg L− 1), Cr(VI) removal efficiency dropped to 90% in 24 h for SM and 22% in 30 days for Oxisol. The Cr(VI) removal of Oxisol and SM fitted, respectively, to the pseudo-first and pseudo-second order, reflecting the way Cr(VI) is removed - by adsorption for SM (since pHPZC> pHsolution) and by reduction to Cr(III) for Oxisol organic matter. To simulate a contamination event, Oxisol was incubated with 300 mg L− 1 of Cr(VI) for 5, 10 and 30 days, followed by sequential extraction. The results of this test revealed that all the chromium was reduced to Cr(III) in all the time periods, and was mostly bound to the less mobile fractions of the soil: organic matter (75–85%), iron oxide/hydroxide (∼ 15%), and the residual fraction (< 5%); and only 5–10% was bound to the exchangeable fraction (more mobile). Although Cr(VI) is better adsorbed by SM, in Oxisol chromium is found in the less toxic form (trivalent) and bound to the less mobile fractions, promoting a more sustainable solution. [ABSTRACT FROM AUTHOR]

Hexavalent chromium (Cr (VI)) is a heavy metal that is distributed globally and poses a significant threat to the environment through various mechanisms. It can react with soil and water, leading to severe environmental damage. In this study, the toxicity of Cr (VI) was investigated by analyzing two major cyanobacteria species, Nostoc commune and Anabaena variabilis, commonly found in soil along with their consortia. The findings revealed that the toxicity mechanisms of Cr (VI) differed in individual monocultures, with Cr (VI) competing with various components. However, when the cyanobacteria species were combined, i.e., in consortia, they demonstrated an impressive retention of their functioning even in Cr (VI) concentration at 10 ppm. The study also concluded that non-photochemical quenching played a critical role in minimizing Cr (VI) toxicity. Furthermore, the research examined the role of the S-cycle in the process. The quantum yield of electron flux revealed that the Cr (VI) was competing with Qa in A. variabilis and with Qb in N. commune, albeit the photosystem dysfunction is only visible in the latter. The mechanism seemed to be quantum tunneling alteration because of the Cr (VI) having different energized quantum wells. The consortia proved to be behaving in a better manner as compared to the control. Overall, this study reveals the mode of toxicity of Cr (VI) in these two important cyanobacterial strains as well as it also discusses the mechanism of tolerance of consortia against Cr (VI) toxicity. [ABSTRACT FROM AUTHOR]

Being a recognized carcinogen, hexavalent chromium is hazardous to both human and environmental health. Thus, it is imperative to regulate and oversee their levels in a variety of industries, including textiles, dyes, pigments, and metal finishing. This study strives to reduce Cr(VI) in wastewater by using capacitive deionization in conjunction with an activated carbon-based electrode and a continuous electrochemical reactor (CER). Activated carbon derived from rubberwood sawdust demonstrated excellent properties, including a high surface area of 1157 m2 g−1. The electrical conductivity and mechanical stability of the electrode were enhanced by the incorporation of synthesized expanded graphite (EG) into the AC. Key parameters were optimized via systematic batch electroreduction experiments with an optimal response surface design. The efficacy of the fabricated CER was proved when it successfully reduced Cr(VI) in a 5 mg L−1 solution within 15 min under optimized conditions, in contrast to the considerably longer durations anticipated by conventional methods. Validation of these findings was done by treating industrial wastewater of 30 mg L−1 in the CER. The electroreduction of Cr(VI) followed the Langmuir isotherm with a maximum capacity of 13.491 mg g−1 and pseudo-second-order kinetics. These results indicate that the combined use of the modified AC electrode and CER holds potential as a sustainable and economical approach to effectively eliminate Cr(VI) from wastewater. [ABSTRACT FROM AUTHOR]

Among xenobiotics, metals gained attention because of their toxicity and harmful effects on aquatic ecosystems, fish and human health. Present research work focused on the toxicological effects of hexavalent chromium on the DNA of three major carps viz. Cirrhina mrigala, Labeo rohita and Catla catla by using the comet assay. All three fish species were exposed to four sub-lethal concentrations (2/3rd, 1/3rd, 1/4th and 1/5th of LC50) of chromium for six exposure durations (14, 28, 42, 56, 70 and 84 days). All three fish species exhibited significantly variable exposure dose and time dependent DNA damage in terms of damaged nuclei, GDI and CTL in their erythrocytes. Among the fish species, C. mrigala showed maximum DNA damage with the highest damaged nuclei (44.28±25.97%), GDI (1.52±0.84) and CTL (126.91±75.71 µm), whereas significantly lower DNA damage was observed in C. catla. At various exposure durations, DNA damage was observed to be significantly higher at 56 days of exposure which then reduced afterward, however, at various exposure concentrations of chromium, maximum DNA damage was observed at 2/3rd of LC50 of metal followed by 1/3rd, 1/4th and 1/5th of acute toxicity of chromium for all three fish species under study. [ABSTRACT FROM AUTHOR]

A simple method for purifying water using household items has been developed. The solution containing an environmental pollutant was added to the PET bottle. The lid of the PET bottle was closed, and the bottle was then placed with the lid down in a freezer for 9 h. The pourer of the PET bottle was surrounded by shredded paper scraps as a lagging material. Before the solution was completely frozen, the sample was removed from the freezer. The unfrozen portion (liquid) was sampled. The pollutant was concentrated in the liquid. The remaining frozen portion was completely thawed. As results, the concentration of the pollutant (Congo Red, Cr (VI), Pb (II), pentachlorophenol, fluoride, nitrate, or phosphate) in the thawed liquid was decreased by more than 90% compared with the initial concentration (0.10 mM). Practitioner Points: A pollutant in a water sample can be removed by freezing a portion of the solution using a PET bottle, shredder scrap, and household freezer.Fluorine and hexavalent chromium can be removed from water to levels that meet water quality standards.The present method can efficiently remove a wide range of contaminants from water, including azo dyes, heavy metals, and pentachlorophenol. [ABSTRACT FROM AUTHOR]

This study explored the fabrication of Polypyrrole (PPy) and Granular Activated Carbon (GAC) composites (PPy‐GAC) for effective removal of toxic hexavalent chromium (Cr(VI)) from aqueous solutions. Two synthesis methods are employed: (1) electrostatic deposition of PPy onto pre‐charged GAC paper and (2) in‐situ chemical polymerization of pyrrole monomer with GAC particles. Batch adsorption experiments investigated the impact of various operational parameters on Cr(VI) removal. Compared to pristine GAC (54.64 mg g−1), the PPy‐GAC composite exhibited a remarkable 3‐fold increase in equilibrium adsorption capacity, reaching 175.44 mg g−1. Pseudo‐second‐order kinetic model (R2 > 0.999) accurately described the adsorption kinetics, while the Langmuir isotherm model (R2 > 0.99) provided a good fit for the equilibrium data. Maximum adsorption capacity (qmax) increased with temperature, reaching 204.08, 243.90, and 270.27 mg g−1 at 298, 308, and 318 K, respectively. Furthermore, a fixed‐bed column experiment examined the composite's effectiveness in continuous Cr(VI) removal, demonstrating its suitability for practical applications. Notably, the PPy‐GAC composite successfully removed Cr(VI) from a real wastewater sample containing 68 µg L−1 Cr(VI) obtained from a ferrochrome industry, highlighting its potential for real‐world remediation. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel Z-scheme heterojunction was attained by in-situ synthesized on the surface of BiVO 4. • Efficient photocatalytic performance of BiVO 4 /0.6CdS for removing binary combined pollution of tetracycline and hexavalent chromium simultaneously. • The photocatalytic mechanism was studied through experimental and theoretical calculations. • Possibly generated intermediate products during the degradation process of TC were examined. In this study, a novel Z-scheme heterojunction on bismuth vanadium/cadmium sulfide (BiVO 4 /0.6CdS) was developed and evaluated for simultaneous photocatalytic removal of combined tetracycline (TC) and hexavalent chromium Cr(Ⅵ) pollution under visible light. Based on the analysis of intermediate products and theoretical calculation, the property of the intermediate products of TC degradation and the effect of built-in electric field (IEF) of composite materials on photo-generated carrier separation were illustrated. According to the experiments and evaluation results, the performance of BiVO 4 /0.6CdS is higher than CdS 2.83 times and 4.82 times under the visible light conditions, with the aspect of simultaneous oxidizing TC and reducing Cr(Ⅵ), respectively. The catalyst has a faster removal rate in the binary composite pollution system than the single one. Therefore, the photocatalytic degradation of TC using BiVO 4 /0.6CdS can reduce the toxic effect of TC on the environment. The aforementioned evaluation provides a new design strategy for Z-scheme heterojunction to simultaneous photocatalytic degradation of composite organic and inorganic pollutants. [ABSTRACT FROM AUTHOR]

Grass carp intestinal waste-mediated biosynthesized nanosilver (AgNPs) was valorized using guaran and zeolite matrices, resulting in AgNPs-guaran, AgNPs-zeolite, and AgNPs-guaran -zeolite composites. The valorized products were examined using Environmental Scanning Electron Microscopy, Energy Dispersive X-ray analysis and X-ray Diffraction analysis to confirm uniform dispersion and entrapment of AgNPs within the matrixes. These valorized products were evaluated for their efficacy in detoxifying the ubiquitous and toxic hexavalent chromium (Cr6+) in aquatic environments, with Anabas testudineus exposed to 2 mg l−1 of Cr6+ for 60 days. Remarkable reduction of Cr6+ concentration to 0.86 ± 0.007 mg l−1 was achieved with AgNPs-guaran-zeolite composite, indicating successful reclamation of contaminated water and food safety assurance. Consistency in results was further corroborated by minimal stress-related alterations in fish physiological parameters and integrated biomarker response within the experimental group treated with the AgNPs-guaran-zeolite composite. Despite observed chromium accumulation in fish tissues, evidence of physiological stability was apparent, potentially attributable to trivalent chromium accumulation, serving as an essential nutrient for the fish. Additionally, the challenge study involving Anabas testudineus exposed to Aeromonas hydrophila exhibited the lowest cumulative mortality (11.11%) and highest survival rate (87.5%) within the same experimental group. The current study presents a novel approach encompassing the valorization of AgNPs for Cr6+ detoxification under neutral to alkaline pH conditions, offering a comprehensive framework for environmental remediation. [ABSTRACT FROM AUTHOR]

Within the scope of eco-friendly green technology, the interest in alternative biosorbents in heavy metal removal from water is increasing. However, chemical- or thermal- activation pretreatments are needed for biomass to have good biosorbent properties. The thermal processes such as carbonization and pyrolysis, which are frequently applied for activation, cause high energy consumption and lead to severe degradation in biomass structure and in surface functional groups. The importance of this study stems from the torrefaction of various biomass species at low temperatures for the purpose of biosorbent preparation and the testing of the biosorbents' heavy metal removal capacity. Thus, biomasses such as tea production waste, corn stalk, pine cone, brown seaweed, rhododendron, and grape seed were torrefied at temperatures of 150–300 °C and the obtained biosorbents were used to remove Pb(II), Cr(VI), and Cd(II) from aqueous solution where concentrations of each metal were 1000 ppm. Effects of the torrefaction temperature, solution temperature, and solution pH on metal uptake were studied by batch adsorption tests. It was determined that the biomasses torrefied at 150 °C has the optimum metal removal capacity. When torrefied corn stalk was used, 17.9 mg/g for Pb(II) and 16.8 mg/g Cr(VI) could be separated from solution, while the maximum Cd(II) uptake was 20.8 mg/g for torrefied tea production waste. It was concluded that the heavy metal removal capacity of biosorbents prepared by low-temperature torrefaction is at non-negligible levels. [ABSTRACT FROM AUTHOR]

Purpose: The Cr(VI) removal capacity of green synthesized nano-zero-valent iron (GnZVI) using tea polyphenols (TPs) remains limited. To improve their application in contaminated soil and groundwater, the GnZVI was modified. This is necessary for in-situ remediation of heavy metal-contaminated soil and groundwater. Materials and methods: The GnZVI-based carbon-composite (L&GnZVI@BC) was successfully constructed via the synergistic effect of L-cysteine modification and biochar support. The Cr(VI) removal capacity and transportability of L&GnZVI@BC were investigated in soil–water system by batch and column experiments. Results and discussion: Comparison with two materials of GnZVI separately modified by L-cysteine (L-GnZVI) or supported by biochar (GnZVI@BC)), GnZVI composite with a combination modification of L-cysteine and biochar (L&GnZVI@BC, L-cysteine/biochar/Fe = 0.1/0.1/1) showed a much higher Cr(VI) removal capacity in soil and groundwater. The synergistic effect of the reduction of L-cysteine functional groups and the dispersibility of biochar support can enhance the transportability of L&GnZVI@BC in water-saturated sand media for more Cr(VI) adsorption at neutral pH; while that improved the soluble Fe(II) released from composite for the higher reduction of Cr(VI) into Cr(III) at acidic pH. Particularly, L&GnZVI@BC favored more Cr(III) generation during transport in porous media at lower pH when applied in the treatment of Cr(VI) contamination. Conclusion: This research highlights that the modification of both L-cysteine and biochar was beneficial to sufficient transport and efficient remediation in Cr(VI)-contaminated soil and groundwater environments at different pH ranges. This study's results provide a theoretical support for the practical application of nZVI composites in in-situ remediation of Cr(VI)-contaminated soil and groundwater via an environmental-friendly approach. [ABSTRACT FROM AUTHOR]

Hexavalent chromium (Cr(VI) contamination in water and wastewater can be treated by reduction of Cr (VI) to Cr(III) with reductants. In this study, the practicality of using FeOx crystals obtained from wastewater was evaluated by studying their reaction with Cr(VI). Cr(VI) was completely removed within 1 to 8 hours of reaction with FeOx, depending on the initial concentration up to 1.9 mM tested. After complete removal of Cr(VI) by FeOx, 22%-38% of the original concentration of Cr(VI) was converted to Cr(III) in the solution, indicating the remaining 62%-78% of the Cr(VI) was associated with the FeOx surface. Cr(VI) was removed by FeOx via reduction to Cr(III) and adsorption/precipitation on the FeOx surface. At pH 3, Cr(VI) was completely removed by FeOx within 20 minutes. Around 20% of the initially added Cr(VI) remained in the solution as Cr(III), while approximately 80% was removed from the solution. At pH 7, roughly 30% of the Cr(VI) was reduced to Cr(III) and the remaining 40% appeared to be in the solid phase after 2-hour reaction. At pH 10, approximately 40% of the Cr(VI) was removed, but Cr(III) was not observed in the solution. The Cr(VI) removal by FeOx is mainly achieved by the reduction of Cr(VI) to Cr(III) under acidic to neutral conditions, and by the adsorption of Cr(VI) onto the solid phase under alkaline conditions. The reduction of Cr(VI) occurred mainly through the reaction with ferrous iron of FeOx, which was enhanced by oxalate of FeOx, forming a soluble Fe(III)-oxalate complex with Fe(III) and reducing the passivation of the FeOx surface. Our study indicates that FeOx is effective at removing Cr(VI) at various concentrations and pH levels. [ABSTRACT FROM AUTHOR]

Potential toxic element (PTE) pollution has emerged as a significant environmental and social concern in global agriculture. Chromium (Cr) occurs in different oxidation states naturally, among them Cr(VI), which is highly toxic. This study carried out biochemical and molecular tests to elucidate the accumulation of total soluble phenolics (TSPs) in rice plants exposed to Cr(VI) at 2.0, 8.0, and 16.0 mg Cr/L, emphasizing the interaction between polyamines (PAs) and abscisic acid (ABA). The results revealed significant Cr accumulation in different tissues of rice plants, which hindered their growth. Cr(VI) exposure increased the ABA concentration, with higher levels detected in the shoots than in the roots. The TSP concentration in rice tissues showed a positive relationship with the supplied concentrations of Cr(VI). The measured PAs, including spermine (Spm), putrescine (Put), and spermidine (Spd), exhibited varied responses to Cr(VI) stress, with only Spm concentration increasing with Cr(VI) concentrations. Real-time qRT-PCR showed PAs and ABA synthesis-associated genes such as OsADC1, OsAIH, OsCPA1, and OsCPA4 were significantly up-regulated in shoot of rice plants treated with Cr(VI). These genes are associated with the second pathway of Put synthesis, originating from Arg. Almost all genes activated in the Met pathway were significantly up-regulated as well. Moreover, the genes involved in the interconversion among the three species of PAs exhibited completely different responses to Cr(VI) exposure. Overall, the biochemical analysis and gene expression data indicate that the interaction between ABA and Spm is likely to enhance the TSP levels in rice plants subjected to Cr(VI) toxicity. [ABSTRACT FROM AUTHOR]

Industrial effluents contain the hazardous metal hexavalent chromium [Cr(VI)], which is potentially lethal to all organisms in the environment. In this work, we developed a transition metal chalcogenide (TMC)-based reduced graphene oxide (rGO) nanocomposite (CeTe/rGO) via the hydrothermal method for the photoreduction of chromium(VI) metal into less hazardous Cr(III). Various analytical tools including x-ray diffraction (XRD), UV–visible spectroscopy (UV–Vis), Brunauer-–Emmett–Teller (BET) and scanning electron microscopy (SEM) analysis were employed for determining characteristics of the CeTe/rGO photocatalyst. The photocatalytic efficiency of transition metal chalcogenide-based rGO nanocomposite was measured under UV–Vis light with a UV–Vis spectrophotometer. The photocatalytic efficiency of CeTe (76.54%) and rGO (81.94%) is smaller than that of the CeTe/rGO (96.50%) due to the larger surface area of the rGO. Scavengers analysis revealed that superoxide anion, hydroxyl radical and holes play a great role in the photocatalysis process. Our results suggest that the CeTe/rGO nanocomposites can potentially be used to reduce the toxic material present in the environment. [ABSTRACT FROM AUTHOR]

Herein, a cationic hydrogel microsphere (CHMS) was prepared by inverse suspension polymerization and freeze‐drying and was applied to the adsorptive removal of hexavalent chromium (Cr(VI)) from aqueous solution. Morphological characterization shows that there are lots of folds and pores on the surface of CHMS with a unique petal‐like appearance. According to the chemical structure analysis, CHMS contains plenty of functional groups such as amine and hydroxyl groups. These features give CHMS a larger specific surface area, faster adsorption rate, and higher adsorption capacity than the conventional cationic hydrogel microparticle (CHMP) adsorbent. The adsorption of Cr(VI) in water by CHMS is mainly based on the combination of electrostatic adsorption and redox reaction, with the electrostatic interaction between the protonated amine and Cr(VI) serving as the predominant adsorption mechanism. Experimental results reveal that CHMS can efficiently remove Cr(VI) from simulated wastewater in both batch and continuous adsorption modes, which is primarily due to its distinctive surface morphology and rich functional groups. Furthermore, the common coexisting metal ions in Cr(VI)‐containing wastewater have no substantial negative influence on the adsorption. Therefore, it can be concluded that CHMS has a promising application prospect in the treatment of Cr(VI)‐containing wastewater. [ABSTRACT FROM AUTHOR]

A new mesoporous Mn(II)‐MOF [Mn2(phen)2(nia)2]∞ with 4‐c uninodal net topology and reiterating rectangular channels in its cargo‐net like extension was synthesized using π‐conjugated phenanthroline (phen) and syn‐syn bridging 5‐nitroisopthalic acid (nia) linkers. The MOF (1) exhibited phase purity, uniform morphology, photo and thermal stability, and robustness; duly triggered by the exceptional framework rigidity via intermolecular H‐bonding and interlayer π–π stacking interactions. The bright‐blue luminescence of the MOF nano‐dispersion was explored for sensitive, specific and ultrafast detection of trinitrophenol (TNP) with extremely low LOD (90.62 nM), high KSV (18.27×104 M−1) and Kq (4×1014 M−1s−1). The vapor‐phase TNP sensing was also accomplished. Additionally, 1 served towards discriminatory, aqueous‐phase monitoring of Cr(VI)‐oxoanions, depicting LODs: 36.08 and 35.70 ppb; KSV: 3.46×104 and 4.87×104 M−1; Kq: 3.26×1013 M−1s−1 and 4.31×1013 M−1s−1; and response time: 32 and 40s for CrO42− and Cr2O72− respectively. The quenching mechanisms (i. e., RET, PET, IFE, weak interactions, collisional quenching and π⋅⋅⋅π stacking) was explained from several experimental investigations and theoretical DFT calculations. The recyclable sensing events and quantification from complex environmental matrices with admirable recovery rates and high KSV (13.02–22.44×104; ~6.31–10.98×104 and ~6.60–11.42×104 M−1 for TNP, CrO42− and Cr2O72−) undoubtedly advocated the consistency of the probe. [ABSTRACT FROM AUTHOR]

A hydrothermal method was employed to synthesise zinc aluminate oxides doped with manganese, with the aim of enhancing the photocatalytic reduction of hexavalent chromium to trivalent chromium. The optical, textural, microscopic, and structural features of the materials were assessed by a range of analytical techniques. These results revealed that incorporation of Mn dopant into the ZnAl 2 O 4 (ZAO) reduced to band gap of ZAO and MD-ZAO are 3.56 and 2.79 eV, respectively. The best photoreduction efficiency was found with manganese-doped ZnAl 2 O 4 (MD-ZAO) is 86.39 % than ZAO (69.38 %) after 120 min. The surface area study displays the 21.43 and 38.65 m2 g−1 for ZAO and MD-ZAO, respectively. When surface area of a nanomaterial is increased, a greater percentage of the material in contact with Cr ion, which increases the photocatalytic activity. A large interfacial area and pore volume aids in development of photoinduced electrons (e−) as well as hole pairs. The impedance study indicates the lower Rct value of ZAO and MD-ZAO are 0.45 Ω and 0.7 Ω, respectively. The finding indicates that Mn doped ZnAl 2 O 4 work as excellent photocatalyst for photoreduction of hexavalent of Cr. The doped material can also act as potential catalyst in different future electrochemical and photocatalytic study. [ABSTRACT FROM AUTHOR]

We are facing a critical aging crisis, with geriatric populations (65+) growing to unprecedented proportions and ~4 million people (a 6.5-fold increase) expected to become centenarians by 2050. This is compounded by environmental pollution, which affects individuals of all ages and contributes to age-related diseases. As we have a limited understanding of how environmental pollutants affect older populations distinctly from younger populations, these longer-lived geriatric populations present a key knowledge gap. To address this knowledge gap, we employ a "Toxic Aging Coin" approach: heads consider how age impacts chemical toxicity, and tails consider how chemicals act as gerontogens—or how they accelerate biological aging. We employed this approach to investigate hexavalent chromium (Cr[VI]) impacts on female rats exposed to 0.05 or 0.1 mg Cr(VI)/L in drinking water for 90 days; these are the maximum contaminant levels (i.e., the highest levels permitted) from the World Health Organization and U.S. Environmental Protection Agency, respectively. During exposure, rats performed a battery of behavior assays to assess grip strength, locomotor coordination, anxiety, spatial memory, sociability, and social novelty preference. We observed age differences in Cr(VI) neurotoxicity, with grip strength, locomotor function, and spatial memory in middle-aged females being particularly affected. We further compared these results in females to results in males, noting many sex differences, especially in middle-aged rats. These data emphasize the need to consider age and sex as variables in toxicology and to revisit drinking water regulations for Cr(VI). [ABSTRACT FROM AUTHOR]

Hexavalent chromium removal from the environment remains a crucial worldwide challenge. To address this issue, microbiological approaches are amongst the straightforward strategies that rely mainly on the bacteria's and fungi's survival mechanisms upon exposure to toxic metals, such as reduction, e flux system, uptake, and biosorption. In this work, scanning electron microscopy, energy-dispersive X-ray spectrophotometry, Fourier transform infrared spectroscopy, and zeta potential measurements were used to investigate the ability of chromium adsorption by Bacillus licheniformis, Bacillus megaterium, Byssochlamys sp., and Candida maltosa strains isolated from tannery wastewater. Scanning electron microscopy combined with energy dispersive X-ray spectroscopy revealed alterations in the cells treated with hexavalent chromium. When exposed to 50 mg/L Cr6+, Bacillus licheniformis and Candida maltosa cells become rough, extracellular secretions are reduced in Bacillus megaterium, and Byssochlamys sp. cells are tightly bound and exhibit the greatestCr weight percentage. In-depth analysis of Fourier transforminfrared spectra of control and Cr-treated cells unveiled Cr-microbial interactions involving proteins, lipids, amino acids, and carbohydrates. These findings were supported by zeta potential measurements highlighting significant variations in charge after treatment with Cr(VI) with an adsorption limit of 100 mg/L Cr6+ for all the strains. Byssochlamys sp. showed the best performance in Cr adsorption, making it the most promising candidate for treating Cr-laden wastewater. [ABSTRACT FROM AUTHOR]

Microplastics are omnipresent in aquatic environments and can act as vectors to carry other pollutants, modifying their pathway through the systems. In this study, the differences in the adsorption capacity and mechanism for Cr(VI) sorption with polyethylene (PE, a conventional microplastic) and polylactic acid (PLA, a biodegradable microplastic) were investigated via characterization of the MPs, the determination of kinetic behavior (pseudo-first- and second-order model, the Elovich model), and the degree of fit to Langmuir and Freundlich isothermal models; the adsorption behavior was also studied under different solution conditions. The results indicated that when the dose of MPs was 1 g/L, the adsorption capacity of Cr(VI) on MPs reached the highest value, the adsorption capacities were PLA(0.415 mg/g) > PE(0.345 mg/g). The adsorption of Cr(VI) on PE followed the Langmuir isotherm model, while PLA had a stronger fit with the Freundlich model. Sorption in both cases followed a pseudo-first-order kinetics model. The maximum adsorption capacity of Cr(VI) on PLA (0.54 mg/g) is higher than that on PE (0.38 mg/g). In addition, PLA could reach adsorption equilibrium in about 8 h and can adsorb 72.3% of the total Cr(VI) within 4 h, while PE required 16 h to reach equilibrium, suggesting that PLA adsorbs at a significantly faster rate than PE. Thus, biodegradable MPs like PLA may serve as a superior carrier for Cr(VI) in aquatic environments. When the pH increased from 2 to 6, the adsorption of Cr(VI) by PE and PLA decreased from 0.49 mg/g and 0.52 mg/g to 0.27 mg/g and 0.26 mg/g, respectively. When the concentration of sodium dodecyl sulfate in the Cr(VI) solution was increased from nil to 300 mg/L, the adsorption of Cr(VI) by PE and PLA increased by 3.66 and 3.05 times, respectively. In addition, a higher temperature and the presence of Cu2+ and photoaging promoted the adsorption of Cr(VI) by MPs, while higher salinity inhibited the adsorption. The desorption efficiencies of Cr(VI) on MPs were PLA(57.8%) > PE(46.4%). The characterization results further confirmed that the adsorption mechanism could be attributed to electrostatic attraction, hydrogen bonding, and surface complexation. In sum, PLA could potentially serve as better vectors for Cr(VI) than PE, but the risk associated with PLA might be higher than that with PE. [ABSTRACT FROM AUTHOR]

The present study reports the surfactant modification of Bolivian natural zeolite with hexadecyltrimethylammonium bromide (HTDMA-Br) for the adsorption of hexavalent chromium Cr (VI) anions from water. The surfactant-modified natural zeolite was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption/desorption isotherms, and Fourier-transform infrared spectroscopy (FTIR) to analyze the effect of its modification with HTDMA-Br and to verify its charge on the zeolite surface. We report a maximum adsorption capacity of 17 mg/g of Cr (VI) anions, surpassing the findings of some of the previous investigations on surfactant-modified natural zeolites of different geological origins. The analysis of the equilibrium data described the Cr (VI) anions adsorption by Langmuir isotherm and the pseudo second-order kinetic model. In addition, thermodynamics revealed an exothermic adsorption. Furthermore, anion exchange, electrostatic attraction, and chemical reduction were indicated to be dominating sorption mechanisms by X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) characterization techniques. [ABSTRACT FROM AUTHOR]

A hydrogel is a three-dimensional structural body with a polymer network that effectively absorbs and stabilizes a wide range of small molecules and ions, thereby reducing the precipitation of metal ions from the matrix. In this study, we successfully prepared a hydrogel named N-GQDs/CuS/Cv-CNNs-70-2 (abbreviated as NCCH-X) by employing the chemical cross-linking method of sodium alginate and calcium chloride and conducted an in-depth study on the morphological and optoelectronic properties of the hydrogel with different photocatalyst contents, as well as on its effectiveness at removing hexavalent chromium Cr(VI). The study's findings indicated that the composite photocatalyst exhibited high treatment efficiency for chromium-containing wastewater when the photocatalyst content was NCCH-10. The hydrogel achieved a high removal rate of 96.37% with a Cr(VI) concentration of 100 mg L−1 under visible light irradiation for 60 min. Moreover, the unique hydrogel structure effectively avoids the precipitation of excessive Cu2+, which reduces the possibility of the lethal risk of copper to organisms in the environment. [ABSTRACT FROM AUTHOR]

• AEP acting as an effective Cr(VI) reducing agent. • Cr(VI) toxicity in rice was significantly alleviated with AEP application. • AEP promoted Cr adsorption to the root cell walls and limited the Cr transport. • AEP application actively triggered the expression of Cr defense-related genes in rice. Hexavalent chromium (Cr(VI)) is a toxic element that has negative impacts on crop growth and yield. Using plant extracts to convert toxic Cr(VI) into less toxic Cr(III) may be a more favorable option compared to chemical reducing agents. In this study, the potential effects and mechanisms of using an aqueous extract of Psidium guajava L. leaves (AEP) in reducing Cr(VI) toxicity in rice were comprehensively studied. Firstly, the reducing power of AEP for Cr(VI) was confirmed by the cyclic voltammetry combined with X-ray photoelectron spectroscopy (XPS) assays. The highest Cr(VI) reduction efficiency reached approximately 78% under 1.5 mg gallic acid equivalent (GAE)/mL of AEP and 10 mg/L Cr(VI) condition. Additionally, Cr(VI) stress had a significant inhibitory effect on rice growth. However, the exogenous application of AEP alleviated the growth inhibition and oxidative damage of rice under Cr(VI) stress by increasing the activity and level of enzymatic and non-enzymatic antioxidants. Furthermore, the addition of AEP restored the ultrastructure of root cells, promoted Cr adsorption onto root cell walls, and limited the translocation Cr to shoots. In shoots, AEP application also triggered the expression of specific genes involved in Cr defense and detoxification response, including photosynthesis pathways, antioxidant systems, flavonoids biosynthesis, and plant hormone signal transduction. These results suggest that AEP is an efficient reduction agent for Cr(VI), and exogenous application of AEP may be a promising strategy to mitigate the harm of Cr(VI) on rice, ultimately contributing to improved crop yield in Cr-contaminated environments. [Display omitted] [ABSTRACT FROM AUTHOR]

With increasing interest in using stannous chloride without filtration to achieve hexavalent chromium maximum contaminant level compliance in California, there is new urgency to quantify its effects on water quality and risks to public health manifested in distribution and premise plumbing systems. Accordingly, a 12‐week groundwater pilot study was completed using ubiquitous premise plumbing materials under flowing (to waste) and stagnating conditions of hexavalent chromium‐containing groundwater following stannous chloride addition without filtration. Results quantified the accumulation and release of chromium and tin, with total chromium concentrations exceeding regulatory or acceptable levels under stagnating conditions. Sediment with elevated chromium, tin, arsenic, and manganese concentrations was also observed. Given these observations would likely occur and worsen over time in distribution systems that cumulatively serve large populations, the use of stannous chloride without filtration represents an unacceptable risk to public health compared to other, more well‐established, best available technologies. [ABSTRACT FROM AUTHOR]

Contamination of aquatic environment by hexavalent chromium Cr (VI) is a major threat due to its health and environmental risks. The biosorption of Cr (VI) using various microorganisms has been extensively examined. The aim of the present study was to evaluate the effectiveness of using the dead biomass of the black yeast Hortaea werneckii SAHE, isolated from sediment samples collected from a solar saltern, as a biosorbent for the removal of Cr (VI). The yeast surface characteristics were examined, and batch experiments were applied to get isothermal and kinetic data. The results revealed that the biosorption process followed the pseudo-second order and intra-particle diffusion kinetic models. The experimental data closely matched both Dubinin–Radushkevich and Langmiur isotherms with a maximum sorption capacity of 4.44mg/ g. The calculated thermodynamic parameters (ΔG°, ΔH° and ΔS°) indicated that the biosorption of Cr (VI) ions onto H. werneckii was feasible, endothermic and spontaneous. A complete removal of Cr (VI) ions was recorded at a concentration of 10mg/ L at room temperature and a pH value of 1.0 after 15min. This study demonstrated that the toxic Cr (VI) could be effectively removed from different wastewater samples by H. werneckii biomass with an adsorption efficiency ranging between 89.06 and 91.95%. [ABSTRACT FROM AUTHOR]

Chromium occurs naturally in different oxidation states. Amongst them, hexavalent chromium is classified as both genotoxic and carcinogenic while trivalent chromium can be considered as an essential element. Therefore, speciation analysis is essential when conducting dietary exposure assessment. Several critical reviews have been published on chromium speciation analysis in foodstuffs in the last decade. However, a method that can account for species interconversion during the extraction procedure has not been reported in the reviews. In recent years, an online method using species-specific isotope dilution mass spectrometry has been developed for the simultaneous determination of trivalent and hexavalent chromium in foodstuffs. Apart from that, new methods based on offline analytical techniques, to analyse trivalent and hexavalent chromium separately, are still under development. Therefore, one of the objectives of this paper is to review these recently published analytical methods and assess whether they are fit for chromium speciation analysis in foodstuffs. Additionally, an objective is also to assess whether their limits of detection are sufficiently low for dietary exposure assessment with respect to the neoplastic effects of hexavalent chromium. Moreover, possible future research gaps are identified based on the current knowledge and existing literature. [ABSTRACT FROM AUTHOR]

Co-transport of Cr(VI) with bentonite colloids (Bc) at different flow rate, pH, ion strength (IS), and colloid concentration in heterogeneous sand media was investigated. The results showed that obvious penetration of dissolved Cr(VI) in co-transport occurred at about 0.5PV, which was mainly due to the heterogeneity of the sand column. The maximum dimensionless transport fraction ((Ct/C0)max) of dissolved Cr(VI) was 0.73 in the co-transport (200 mg·L-1 Bc and 2.5 ml min-1), much lower than that in the single transport of Cr(VI) (0.98). The increase of pH promoted the transport of Cr(VI) in co-transport with Bc. Elevated flow rate, ion strength, and Bc concentration reduced Cr(VI) transport. Cr(VI) in the effluent in co-transport with Bc was dominated by dissolved Cr(VI), and a small amount of colloidal Cr(VI) (～4.97%) was observed. The recovery rates of total transported Cr(VI) (dissolved +colloidal) in co-transport with Bc were obviously lower than those in single transport. (Ct/C0)max values of dissolved Cr(VI) in the co-transport with Bc were also lower than those with other colloids, e.g. kaolin colloid, montmorillonite colloid, and inorganic soil colloid. Application of bentonite may alleviate the transport risk of Cr(VI) to groundwater. [ABSTRACT FROM AUTHOR]

In order to transform hazardous substances into their less harmful or nontoxic constituent elements, microorganisms are used in the remediation process known as "bioremediation." Any biological process that uses microorganisms such as fungi, algae, yeast, bacteria, or green plants, or the enzymes produced by the microorganisms, can restore the natural environment altered by heavy metal pollutants. Among the heavy metals, hexavalent chromium (Cr (VI)) is the most toxic pollutant in the environment. Several human activities are responsible for its release into the environment. The chemical, physical, and biological characteristics have a positive influence on the dissolution within the aqueous medium. Exposure to Cr (VI) may have an influence on both human health and the flora and fauna of the environment. Because of its mutagenic and carcinogenic properties, chromium (VI) is a much more hazardous substance than other chromium species, such as Cr (V) and Cr (III). Dermatitis, asthma, pneumonitis, and bronchiogenic cancer are all possible outcomes of chronic Cr (VI) exposure. The effective management of Cr (VI) to address concerns about public health is absolutely essential from an environmental point of view. This study focuses on the toxicity of chromium and its interactions with various strains of microbes, specifically examining how they might bio-reduce Cr (VI). [ABSTRACT FROM AUTHOR]

Chromium contamination of soils is a worldwide issue because of the risks related to such a heavy metal as it presents elevated carcinogenic, mutagenic, and teratogenic characteristics. This highlights the importance of developing feasible remediation strategies for chromium-contaminated sites. The present research employs the adjusted porosity/cement index (η /(Civ)0.28 = 18, 20, and 23) to define the dosages for stabilizing a hexavalent chromium-contaminated silty soil, considering stabilization and solidification S/S approach. Mechanical (unconfined compressive strength, small strain stiffness, and durability) and environmental (solubility and leachability tests) were conducted on different compacted silty sand-Portland cement mixtures contaminated with hexavalent chromium considering a seven-day curing period. The main findings indicate the usefulness of the porosity/cement index approach in defining the dosage for S/S applications, particularly when considering the mechanical aspects. Also, the tested dosages were helpful in substantially reducing the solubility and leachability of chromium. Still, they were not capable of reducing to the toxicity and potability levels preconized by some agencies. [ABSTRACT FROM AUTHOR]

Hexavalent chromium (Cr(VI)) is a hazardous metallic compound commonly used in industrial processes. The liver, responsible for metabolism and detoxification, is the main target organ of Cr(VI). Toxicity experiments were performed to investigate the impacts of low-dose exposure to Cr(VI) on rat livers. It was revealed that exposure of 0.05 mg/kg potassium dichromate (K2Cr2O7) and 0.25 mg/kg K2Cr2O7 notably increased malondialdehyde (MDA) levels and the expressions of P-AMPK, P-ULK, PINK1, P-Parkin, and LC3II/LC3I, and significantly reduced SOD activity and P-mTOR and P62 expression levels in liver. Electron microscopy showed that CR(VI) exposure significantly increased mitophagy and the destruction of mitochondrial structure. This study simulates the respiratory exposure mode of CR(VI) workers through intratracheal instillation of CR(VI) in rats. It confirms that autophagy in hepatocytes is induced by low concentrations of CR(VI) and suggest that the liver damage caused by CR(VI) may be associated with the AMPK-related PINK/Parkin signaling pathway. [ABSTRACT FROM AUTHOR]

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The municipal wellfield in Collierville, Tennessee, is contaminated with trichloroethylene (TCE) and hexavalent chromium (Cr (VI)) due to industrial operations dating back to the 1970s and 1980s. This study aims to elucidate the aquifer's contaminant transport mechanisms by determining longitudinal and transverse dispersivities through inverse modeling. Utilizing MT3DMS for contaminant transport simulation, based on a well-calibrated groundwater flow model, and leveraging Python's multiprocessing library for efficiency, the study employs a trial-and-error methodology. Key findings reveal that longitudinal dispersivity values range from 5.5 m near the source to 20.5 m further away, with horizontal and vertical transverse dispersivities between 0.28 m and 3.88 m and between 0.03 m and 0.08 m, respectively. These insights into the aquifer's dispersivity coefficients, which reflect the scale-dependent nature of longitudinal dispersivity, are crucial for optimizing remediation strategies and achieving cleanup goals. This study underscores the importance of accurate parameter estimation in contaminant transport modeling and contributes to a better understanding of contaminant dynamics in the Collierville wellfield. [ABSTRACT FROM AUTHOR]