Efficient remediation of different concentrations of Cr-contaminated soils by nano zero-valent iron modified with carboxymethyl cellulose and biochar.

Nano zero-valent iron (nZVI) is widely used in soil remediation due to its high reactivity. However, the easy agglomeration, poor antioxidant ability and passivation layer of Fe-Cr coprecipitates of nZVI have limited its application scale in Cr-contaminated soil remediation, especially in high concentration of Cr-contaminated soil. Herein, we found that the carboxymethyl cellulose on nZVI particles could increase the zeta potential value of soil and change the phase of nZVI. Along with the presence of biochar, 97.0% and 96.6% Cr immobilization efficiency through CMC-nZVI/BC were respectively achieved in high and low concentrations of Cr-contaminated soils after 90-days remediation. In addition, the immobilization efficiency of Cr(VI) only decreased by 5.1% through CMC-nZVI/BC treatment after 10 weeks aging in air, attributing to the strong antioxidation ability. As for the surrounding Cr-contaminated groundwater, the Cr(VI) removal capacity of CMC-nZVI/BC was evaluated under different reaction conditions through column experiments and COMSOL Multiphysics. CMC-nZVI/BC could efficiently remove 85% of Cr(VI) in about 400 hr when the initial Cr(VI) concentration was 40 mg/L and the flow rate was 0.5 mL/min. This study demonstrates that uniformly dispersed CMC-nZVI/BC has an excellent remediation effect on different concentrations of Cr-contaminated soils.

Investigation into enhanced performance of toluene and Hg0 stimulative abatement over Cr-Mn oxides co-modified columnar activated coke.

In this study, a string of Cr-Mn co-modified activated coke catalysts (XCryMn1-y/AC) were prepared to investigate toluene and Hg0 removal performance. Multifarious characterizations including XRD, TEM, SEM, in situ DRIFTS, BET, XPS and H2-TPR showed that 4%Cr0.5Mn0.5/AC had excellent physicochemical properties and exhibited the best toluene and Hg0 removal efficiency at 200℃. By varying the experimental gas components and conditions, it was found that too large weight hourly space velocity would reduce the removal efficiency of toluene and Hg0. Although O2 promoted the abatement of toluene and Hg0, the inhibitory role of H2O and SO2 offset the promoting effect of O2 to some extent. Toluene significantly inhibited Hg0 removal, resulting from that toluene was present at concentrations orders of magnitude greater than mercury's or the catalyst was more prone to adsorb toluene, while Hg0 almost exerted non-existent influence on toluene elimination. The mechanistic analysis showed that the forms of toluene and Hg0 removal included both adsorption and oxidation, where the high-valent metal cations and oxygen vacancy clusters promoted the redox cycle of Cr3+ + Mn3+/Mn4+ ↔ Cr6+ + Mn2+, which facilitated the conversion and replenishment of reactive oxygen species in the oxidation process, and even the CrMn1.5O4 spinel structure could provide a larger catalytic interface, thus enhancing the adsorption/oxidation of toluene and Hg0. Therefore, its excellent physicochemical properties make it a cost-effective potential industrial catalyst with outstanding synergistic toluene and Hg0 removal performance and preeminent resistance to H2O and SO2.

Carbon paste based sensor for sensitive Cr(III) ion determination in different water samples and anti-diabetic supplement.

A modified carbon paste sensor based on N,N'-(((ethane-1,2-diylbis(oxy))bis(2,1-phenylene))bis(methanylylidene))bis(pyridine-2-amine; BPA Schiff base as Cr(III) selective carrier was fabricated and studied in this work. The proposed sensor homogenization and mechanism of action was studied by infra-red (IR) and scanning electron microscope (SEM) with energy dispersive X-ray (EDX) tools. The sensor covered 1.0 × 10-7-1.0 × 10-1 mol L-1 linear range and a detection limit of 7.22 × 10-8 mol L-1 for Cr(III) with 20.17 ± 0.13 mV decade-1 Nernstian slope. 5 s was the response time of the prepared sensor and it was reproducible and stable for 3 months. The working pH range was 3.3-6.0 and it also works well to determine Cr(III) ion in presence of water miscible solvents up to 12.5% content of the methanol and 17.5% of ethanol. The electrode's selectivity was studied using separate and mixed solution methods for selectivity coefficients determination and the sensor showed good selectivity relative to a variety of metal ions (selectivity coefficients = 1.01 × 10-5-8.57 × 10-3). In addition, the practical analysis value of the sensor was demonstrated by measurement of Cr(III) quantitatively in mineral water, supplement and also as an indicator electrode in Cr(III) against EDTA potentiometric titration with good reproducibility (RSDs of 0.91-2.15%).

Preliminary study of microbiologically influenced corrosion by Pseudomonas aeruginosa on high Chromium white iron.

Microbiologically Influenced Corrosion (MIC) poses a significant challenge to various industries, leading to substantial economic losses and potential safety hazards. Despite extensive research on the MIC resistance of various materials, there is a lack of studies focusing on High Chromium White Iron (HCWI) alloys, which are widely used in wear-resistant applications. This study addresses this knowledge gap by providing a comprehensive investigation of the MIC resistance of three HCWI alloys with varying chromium contents (22 wt%, 30.7 wt%, and 21 wt%) in the presence of Pseudomonas aeruginosa (P. Aeruginosa), a common bacterial species associated with MIC. The alloys were exposed to an artificial seawater medium inoculated with P.Aeruginosa for 14 days, and their corrosion behaviour was evaluated using electrochemical techniques, surface analysis, and microscopy. Electrochemical Impedance Spectroscopy (EIS) results revealed that the alloy with the highest chromium content (A2, 30.7 wt% Cr) exhibited superior MIC resistance compared to the other alloys (A1, 22 wt% Cr and M1, 21 wt% Cr). The enhanced performance of alloy A2 was attributed to the formation of a more stable and protective passive film, as well as the development of a more compact and less permeable biofilm. The EIS data, interpreted using equivalent circuit models, showed that alloy A2 had the highest charge transfer resistance and the lowest biofilm capacitance, indicating a more effective barrier against corrosive species. Bode plots further confirmed the superior corrosion resistance of alloy A2, with higher impedance values and phase angles at low frequencies compared to alloys A1 and M1. Scanning Electron Microscopy (SEM) and optical microscopy analyses corroborated these findings, showing that alloy A2 had the lowest pit density and size after 14 days of exposure. The insights gained from this study highlight the critical role of chromium content in the MIC resistance of HCWI alloys and have significant implications for the design and selection of materials for applications prone to microbial corrosion.

Novel Ag@NH2-UiO-66(Zr) photocatalyst with controllable charge transfer pathways for efficient Cr(VI) remediation.

Rational fabrication of core-shell photocatalysts to hamper the charge recombination is extraordinarily essential to enhance photocatalytic activity. In this work, core-shell Ag@NH2-UiO-66 (Ag@NU) Schottky heterojunctions with low Ag content (1 wt%) were constructed by a two-step solvothermal method and adopted for Cr(VI) reduction under LED light. Typically, the one with the Ag: NH2-UiO-66 mass ratio (1 : 100) led to 100% Cr(VI) removal within 1 h, superior to bare NH2-UiO-66 and Ag/NH2-UiO-66 (Ag was directly decorated on NH2-UiO-66 surface). The enhanced photocatalytic activity was related to the migration of the electrons on the CB of NH2-UiO-66 to Ag NPs through a Schottky barrier, and thus the undesired charge carriers recombination was avoided. This result was also evidenced by Density functional theory (DFT) calculations. The computational simulations indicate that the introduction of Ag effectively narrowed the band gap of NH2-UiO-66, facilitating the transfer of photo-generated electrons, expanding the light absorption area, and significantly enhancing photocatalytic efficiency. Most importantly, such a core-shell structure can inhibit the formation of •O2-, letting the direct Cr(VI) reduction by photo-excited e-. In addition, this structure can also protect Ag from being oxidized by O2. Ten cyclic tests evidenced the Ag@NU had excellent chemical and structural stability. This research offers a novel strategy for regulating the Cr(VI) reduction by establishing core-shell photocatalytic materials.

Fenton-conditioning of landfill leachate biological sludge enables biochar for efficient Cr(â ¥)removal: Occurrence of oxygen-centered free radicals.

Fenton-conditioning is commonly used to improve dewatering ability for municipal biological sludge, however, its application in industries is scarce. In this study, biochar (FT-BC) was successfully synthesized from a Fenton-conditioned landfill leachate biological sludge under oxygen-limited. As compared to the corresponding blank and poly ferric-pretreated biochars (BC and PF-BC), moderate Fenton conditioning of the sludge could enable good removal performance for Cr (Ⅵ) by FT-BC. It was found that the oxygen central free radicals (OCFRs) on the biochar surface was intensively promoted due to Fenton electrophilic addition of ·OH onto the oxygen-containing functional groups in biomass. The amounts of OCFRs correlated positively well with the removal efficiency, indicating these persistent free radicals (PFRs)would mainly responsible for the reductive immobilization of Cr(VI)on the FT-BC surface. This study is expected to provide a new method for reclamation of industrial biological sludges with poor agglomeration by introducing simple Fenton pre-conditioning.

Chromium (VI) removal by magnetite nanoparticles immobilized with extracellular polymeric substances extracted from Lysinibacillus sp. WH.

Magnetite nanoparticles (nano-Fe3O4) and nano-Fe3O4 immobilized with bacterial extracellular polymeric substances (EPSs) extracted from Lysinibacillus sp. WH (Fe3O4/bact) were comparatively studied for the removal of Cr (VI) ions from aqueous solution in batch study. The objectives were to explore the removal of Cr (VI) efficiency by nano-Fe3O4 and Fe3O4/bact under varying bacterial concentrations at a range of acidic pH. Results indicated that 150 ppm Cr (VI) could be effectively removed by 5 g/L of nano-Fe3O4 at pH 4, with the efficiency of 89.2 ± 12%. The equilibrium time, determined by a pseudo-second-order model (R2 = 0.9983), was after 5 h, indicating chemical adsorption. The Cr (VI) removal by the nano-Fe3O4 immobilized with bacterial EPS was effective and steady under a wide range of acidic conditions although bacterial EPS has an alkaline nature. Here, we are the first to demonstrate that Cr (VI) removal efficiency by different concentrations of EPS was not significantly different, suggesting EPS concentration is possibly not the most crucial factor to be optimized for Cr (VI) removal in the future. This study shows the potential application of nano-Fe3O4 immobilized with bacterial EPS for wastewater treatment. PRACTITIONER POINTS: The equilibrium time for magnetite nanoparticles to remove Cr (VI) is 5 h, suggesting chemical adsorption. The Cr (VI) removal efficiency of either magnetite nanoparticles or bacterial EPS is stable under a wide range of acidic conditions. Magnetite nanoparticles immobilized with bacterial EPS extracted from Lysinibacillus sp. WH has a potential application for Cr (VI) removal in wastewater.

Promising deep-red emitting Cr3+-doped SrAl12O19 phosphors for plant growth LEDs.

Recently, deep-red-emitting phosphors that can be excited by ultraviolet (UV) and near-ultraviolet (NUV) light have been extensively investigated for plant growth LED applications. However, due to the harmful effects of these high-energy rays on plants, violet- or blue-excited deep-red-emitting phosphors are considered a more appropriate solution. In this work, SrAl12O19:Cr3+ phosphors were synthesized using a simple solid-state reaction, revealing a strikingly sharp deep-red emission band centered at 694 nm and effective excitation by violet light. The optimal SrAl12O19:1.0%Cr3+ phosphor, annealed at 1500°C, exhibits an extended lifetime of 0.549 ms, an energy activation level of 0.239 eV, a good quantum efficiency (QE) of 36.2%, and superior color purity at 100%. Further, an LED prototype with a precise absorption spectrum for far-red phytochrome (Pfr) has been demonstrated. These results indicate that the synthesized SrAl12O19:1.0%Cr3+ phosphors could be used as a promising deep-red-emitting phosphor for plant growth LED.

Effects of ionic strength and bentonite ratio on the migration of Cr(VI) in clayey soil-bentonite engineered barrier.

Soil-bentonite (S-B) barriers have been widely used for heavy metal pollution containment. This study conducted batch adsorption tests and diffusion-through tests to evaluate how ionic strength and bentonite ratio influence the migration of Cr(VI) in natural clay-bentonite mixtures. The test results indicated that the adsorption of Cr(VI) exhibited an obvious anion adsorption effect, the pH of the soil mixture increased with the addition of bentonite, resulting in a decrease in the positive surface charge. This change led to a decrease in Cr(VI) adsorption capacity, from 775.19 mg/kg for pure clay to 378 mg/kg for mixture samples with excessive bentonite. Furthermore, as the ionic strength increases from 0 to 0.1 M, the Cr(VI) adsorption capacity increases slightly due to the weakening of electrostatic repulsion on the clay particle surface, but the effective diffusion coefficient (De) increases by 21.97%. The compression of the diffusion double layer (DDL) under high ionic strength conditions enlarges the diffusion path and enhances the migration of Cr(VI) through the pore flow paths. Moreover, hydrated bentonite effectively fills the interaggregate pores of natural clay, thus creating narrower and more tortuous flow paths. However, excessive bentonite increases the pH value and pore volume, resulting in changes to the soil microstructure and disrupting the continuous skeleton of natural clay, which is unfavorable for Cr(VI) containment. Based on the study of the Cr(VI) contaminated site, a bentonite ratio of 2:10 is recommended for optimal natural performance of the natural clay-bentonite barrier.

Microbially induced carbonate precipitation with Arthrobacter creatinolyticus: An eco-friendly strategy for mitigation of chromium contamination.

Chromium contamination from abandoned industrial sites and inadequately managed waste disposal areas poses substantial environmental threat. Microbially induced carbonate precipitation (MICP) has shown promising, eco-friendly solution to remediate Cr(VI) and divalent heavy metals. In this study, MICP was carried out for chromium immobilization by an ureolytic bacterium Arthrobacter creatinolyticus which is capable of reducing Cr(VI) to less toxic Cr(III) via extracellular polymeric substances (EPS) production. The efficacy of EPS driven reduction was confirmed by cellular fraction analysis. MICP carried out in aqueous solution with 100 ppm of Cr(VI) co-precipitated 82.21% of chromium with CaCO3 and the co-precipitation is positively correlated with reduction of Cr(VI). The organism was utilized to remediate chromium spiked sand and found that MICP treatment decreased the exchangeable fraction of chromium to 0.54 ±â€¯0.11% and increased the carbonate bound fraction to 26.1 ±â€¯1.15% compared to control. XRD and SEM analysis revealed that Cr(III) produced during reduction, influenced the polymorph selection of vaterite during precipitation. Evaluation of MICP to remediate Cr polluted soil sample collected from Ranipet, Tamil Nadu also showed effective immobilization of chromium. Thus, A. creatinolyticus proves to be viable option for encapsulating chromium contaminated soil via MICP process, and effectively mitigating the infiltration of Cr(VI) into groundwater and adjacent water bodies.

Effect of Ho3+ Substitution on Magnetic Properties of ZnCr2Se4.

A series of ZnCr2-xHoxSe4 microcrystalline spinels (where x = 0.05, 0.075, and 0.10) containing holmium ions in octahedral coordination were obtained by sintering of adequate reactants at high temperatures. The obtained doped materials were characterized by X-ray diffraction, Scanning Electron Microscopy, UV-Vis-NIR, molecular field approximation, and XPS spectroscopies. Their thermal properties were also investigated. The doping of the ZnCr2S4 matrix with paramagnetic Ho3+ ions with a content of not more than 0.1 and a screened 4f shell revealed a significant effect of orbital and Landau diamagnetism, a strong reduction in short-range ferromagnetic interactions, and a broadening and shift of the peak of the first critical field by simultaneous stabilization of the sharp peak in the second critical field. These results correlate well with FPLO calculations, which show that Cr sites have magnetic moments of 3.19 µB and Ho sites have significantly larger ones with a value of 3.95 µB. Zn has a negligible magnetic polarization of 0.02 µB, and Se induces a polarization of approximately -0.12 µB.

Efficient removal of Chromium(VI) from wastewater based on magnetic multiwalled carbon nanotubes coupled with deep eutectic solvents.

Industrial wastewater containing heavy metal Cr(VI) seriously affects the health of organisms and may even lead to cancer. Developing efficient adsorbents that can quickly separate heavy metals is crucial for treating wastewater. In this study, magnetic multiwalled carbon nanotubes (MMWCNTs) with moderate particle size and abundant surface active sites were prepared by coating multiwalled carbon nanotubes with magnetic nanoparticles. The results of FTIR, XRD, TG, VSM, BET, and EDS showed MWCNTs completely encapsulated on the surface of the magnetic nanoparticles, with a particle size of approximately 30 nm. Oxygenated groups provided abundant surface active sites and formed numerous mesopores. The response surface methodology was used to optimize the adsorbent dose, adsorption contact time and adsorption temperature, and the removal rate of Cr(VI) was more than 95%. The quasi-second order kinetics and Freundlich adsorption isotherm model explained the adsorption process to Cr(VI). MMWCNTs interacted with Cr(VI) through electrostatic attraction, reduction reactions, complexation, and other means. The extensive hydrogen bonding of the green solvent deep eutectic solvent (DES) was employed to desorb the MMWCNTs and desorption rate exceed 90%. Even after five adsorption-regeneration cycles, the adsorbent maintained a high capacity. In conclusion, these novel MMWCNTs, as efficient adsorbents paired with DES desorption, hold broad potential for application in the treatment of Cr(VI)-contaminated wastewater.

A META analysis on the efficacy of functional materials for soil chromium remediation.

Metallic chromium pollution in soil is widespread, which aroused intensive research in recent decades. In mainstream research, most studies use materials with a reducing ability to adsorb and reduce hexavalent chromium. However, comprehensive analyses and systematic verifications of these different materials are scarce. Therefore, this study conducted a meta-analysis of relevant papers published from 2013 to October 2024 to compare and analyze the performance and usage conditions of some common materials, such as iron-based materials, mineral inorganic materials, organic materials, and layered double hydroxide materials. We synthesized 31 papers for 186 pairwise comparisons and selected the Standardized Mean Difference (SMD) as the appropriate effect size for mean-to-mean comparisons. Fe-based materials had the most stable performance based on its numerous data support, while organic materials had the worst performance. The difference in performance between inorganic mineral materials was the greatest, which was closely related to the selection of components. The difference in the effectiveness of inorganic materials was the greatest, which was closely related to the selection of components and there was room for further improvement. Through further analysis of the impact of environmental factors on material performance, it can be concluded that the effect of the material was better under alkaline, non-sandy, low organic matter, and high CEC soil conditions.

Enhancing photocatalytic reduction of Cr(VI) in water through morphological manipulation of g-C3N4 photocatalysts: A comparative study of 1D, 2D, and 3D structures.

In this research, the dimensional catalysts of pure g-C3N4 photocatalysts (1D, 2D, and 3D) were investigated for the reduction of the highly toxic/carcinogenic Cr(VI) under visible light irradiation. The catalysts underwent explanation through various surface analysis techniques. According to the BET data, the specific surface area of the 3D catalyst was 1.3 and 7 times higher than those of the 2D and 1D CN catalysts, respectively. The 3D catalyst demonstrated superior performance, achieving an efficiency greater than 99% within 60 min under visible light irradiation in the presence of EDTA due to the abundance of active sites. The study also delved into the influence of factors such as the amount of EDTA-hole scavenger, pH, catalyst dosage, and temperature on the photocatalytic reduction of Cr(VI). Moreover, the 3D catalyst showed excellent reusability, maintaining an efficiency of more than 80% even after 10 cycles, and performed effectively in real water samples. The 3D CN catalyst, with its facile synthesis process, excellent visible light harvesting properties, high reduction efficiency that sustains over multiple cycles, and outstanding performance in real water samples, presents a significant advancement for practical applications in environmental remediation. This research contributes to a new understanding of developing efficient degradation methods for heavy metals in polluted water, highlighting the potential of 3D g-C3N4 catalysts in environmental cleanup efforts.

Desulfovibrio-induced gauzy FeS for efficient hexavalent chromium removal: The influence of SRB metabolism regulated by carbon source and electron carriers.

Biosynthetic metal sulfides showed great application prospects in the environmental treatment against high-valence metal pollutants. However, the efficiency of biosynthesis, agglomeration during the reaction process, and the formation of the passivation layer during the reduction process were always the important factors restricting its development. This study explored the composition of the culture medium to promote the growth of highly corrosive sulfate-reducing bacteria (SRB) and its metabolism to produce FeS nanoparticles (NPs). The results showed that reducing the carbon source (CS) and adding electron carriers in the culture medium effectively promoted the production of small, dispersed, and loose FeS NPs in cells. At pH = 7, 24 °C and 10 min reaction time, 0.1 g/L FeS NPs produced by SRB under the conditions of 10 % CS with 10 ppm cytochrome c medium could achieve 100 % removal efficiency of 1 mM hexavalent chromium (Cr(VI)). Under this condition, FeS NPs could be produced by intracellular metabolism in SRB cells, and environmental factors such as pH, metal cations, and Cl- had little effect on the removal of Cr(VI) by this FeS NPs. The surface proteins of FeS NPs significantly enhanced their antioxidant properties. After 7 days of natural environment exposure, the Cr(VI) removal efficiency of FeS NPs was only reduced by 16 % compared with the initial sample. This work provided an in-depth understanding of Cr(VI) removal by SRB biosynthesis of FeS and contributes to the widespread application of FeS in the future.

Fluorescence detection of valence speciation of Cr(III) based on the catechol oxidase mimic enzyme activity of CuSeNP nanozymes.

Copper selenide nanoparticles (CuSeNP) were synthesized using histidine, ethylenediamine, and sodium selenate as precursors by one-step microwave digestion methods. The as-prepared CuSeNPs exhibit excellent catechol oxidase mimic enzyme and catalase (CAT)-like activities. Dopamine (DA) can be oxidized to aminochrome with H2O2 by CuSeNPs, and the intermediate product aminochrome can further react with α-naphthol to yield a highly fluorescent derivative. It was confirmed that Cr(III) could adsorb on the surface of CuSeNPs and inhibit the production of semiquinone radicals in the reaction system, and the catalytic activity of CuSeNPs was inhibited. The detection mechanisms, kinetics, and catalytic properties of CuSeNPs were systematically investigated. As a result, a novel fluorescence method for the assay of Cr(III) was established. The feasibility of CuSeNP nanozyme in detecting speciation Cr(III) in food samples was explored with satisfactory results. It showed the obvious potential for developing effective and dependable fluorescent detection method for protecting food safety.

An investigation into the aging mechanism of disposable face masks and the interaction between different influencing factors.

In the natural environment, a symphony of environmental factors including sunlight exposure, current fluctuations, sodium chloride concentrations, and sediment dynamics intertwine, potentially magnifying the impacts on the aging process of disposable face masks (DFMs), thus escalating environmental risks. Employing Regular Two-Level Factorial Design, the study scrutinized interactive impacts of ultraviolet radiation, sand abrasion, acetic acid exposure, sodium chloride levels, and mechanical agitation on mask aging. Aging mechanisms and environmental risks linked with DFMs were elucidated through two-dimensional correlation analyses and risk index method. Following a simulated aging duration of three months, a single mask exhibited the propensity to release a substantial quantity of microplastics, ranging from 38,800 ± 360 to 938,400 ± 529 particles, and heavy metals, with concentrations from 0.06 ± 0.02 µg/g (Pb) to 29.01 ± 1.83 µg/g (Zn). Besides, specific contaminants such as zinc ions (24.24 µg/g), chromium (VI) (4.20 µg/g), thallium (I) (0.92 µg/g), tetracycline (0.51 µg/g), and acenaphthene (1.73 µg/g) can be adsorbed significantly by aged masks. The study elucidates pivotal role of interactions between ultraviolet radiation and acetic acid exposure in exacerbating the environmental risks associated with masks, while emphasizing the pronounced influence of many other interactions. The research provides a comprehensive understanding of the intricate aging processes and ensuing environmental risks posed by DFMs, offering valuable insights essential for developing sustainable management strategies in aquatic ecosystems.

Plant endophyte immobilization technology: A promising approach for chromium-contaminated water and soil remediation.

Microbial immobilization technology is considered an efficient bioremediation method for chromium (Cr) pollution. However, it is currently unclear which strain is more beneficial for the remediation of Cr-contaminated water and soil. Therefore, corn straw biochar was used as a carrier to prepare materials for fixing the endophytes Serratia sp. Y-13 (BSR1), Serratia nematodiphila (BSR2), Lysinibacillus sp. strain SePC-36 (BLB1), Lysinibacillus mangiferihumi strain WK63 (BLB2) and the commercial bacteria Shewanella oneidensis MR-1 (BSW). The results demonstrated that, compared with BSW, endophyte-loaded biochar (especially BSR1) was more effective at remediating Cr pollution in water and soil. Endophyte-loaded biochar reduced the abundance of soil pathogenic bacteria, enhanced the number of beneficial plant endophytes, reduced the soil Cr(VI) concentration, improved soil fertility, reduced the plant Cr concentration and improved the yield of lettuce. Redundancy analysis (RDA) and structural equation modelling (PLS-PM) suggested that soil microbes are closely related to soil Cr(VI), plant fresh weight and soil organic matter, whereas endophyte-loaded biochar directly influences plant cell motility pathways by altering plant microbes. This study represents a pioneering investigation into the efficacy of endophyte-loaded biochar as a remediation strategy for Cr pollution.

Efficient removal of chromate from wastewater using a one-pot synthesis of chitosan cross-linked ceria incorporated hydrous copper oxide bio-polymeric composite.

Remediating hexavalent chromium [Cr(VI)] from contaminated water systems is a significant concern due to its harmful effects on human health, aquatic life, and plants. To tackle this issue, scientists have created a chitosan cross-linked hydrous ceria incorporated cupric oxide bio-polymeric composite (CHCCO) by combining chitosan biopolymer with corresponding metal ions using glutaraldehyde as a cross-linker. The composite was characterized using advanced analytical instruments such as FTIR, p-XRD, SEM, XPS, etc. The synthesized composite (CHCCO) was then tested for its efficiency in removing Cr(VI) from synthetic Cr(VI) aqueous samples. The parameters examined included pH, material dose, contact time, concentration, temperature, and co-existing ions. The experimental data showed that the kinetics and equilibrium data fit well with the pseudo-second-order and the Freundlich isotherm models, respectively. Thermodynamic analysis demonstrated that the investigated surface adsorption process is spontaneous and endothermic. Except for the SO42- ion, no other species imparts adverse influence significantly on the reaction. The CHCCO bio-composite surfaces were refreshed using a dilute NaOH (1.0 M) solution and effectively recycled five times for Cr(VI) adsorption, indicating no significant surface activity deterioration. This study highlights the high effectiveness of CHCCO bio-polymeric composites in Cr(VI) remediation and the potential for this technology as an easy-to-use technique for environmental restoration.

Adsorption mechanism of hexavalent chromium on electron beam-irradiated aged microplastics: Novel aging processes and environmental factors.

Microplastics are widely present in the natural environment and exhibit a strong affinity for heavy metals in water, resulting in the formation of microplastics composite heavy metal pollutants. This study investigated the adsorption of heavy metals by electron beam-aged microplastics. For the first time, electron beam irradiation was employed to degrade polypropylene, demonstrating its ability to rapidly age microplastics and generate a substantial number of oxygen-containing functional groups on aged microplastics surface. Adsorption experiments revealed that the maximum adsorption equilibrium capacity of hexavalent chromium by aged microplastics reached 9.3 mg g-1. The adsorption process followed second-order kinetic model and Freundlich model, indicating that the main processes of heavy metal adsorption by aged microplastics are chemical adsorption and multilayer adsorption. The adsorption of heavy metals on aged microplastics primarily relies on the electrostatic and chelation effects of oxygen-containing functional groups. The study results demonstrate that environmental factors, such as pH, salinity, coexisting metal ions, humic acid, and water matrix, exert inhibitory effects on the adsorption of heavy metals by microplastics. Theoretical calculations confirm that the aging process of microplastics primarily relies on hydroxyl radicals breaking carbon chains and forming oxygen-containing functional groups on the surface. The results indicate that electron beam irradiation can simultaneously oxidize and degrade microplastics while reducing hexavalent chromium levels by approximately 90%, proposing a novel method for treating microplastics composite pollutants. Gas chromatography-mass spectrometry analysis reveals that electron beam irradiation can oxidatively degrade microplastics into esters, alcohols, and other small molecules. This study proposes an innovative and efficient approach to treat both microplastics composite heavy metal pollutants while elucidating the impact of environmental factors on the adsorption of heavy metals by electron beam-aged microplastics. The aim is to provide a theoretical basis and guidance for controlling microplastics composite pollution.