The superior antimicrobial properties of silver nanoparticles (Ag NPs) are well-documented, but the exact mechanisms underlying Ag-NP microbial toxicity remain the subject of intense debate. Here, we ...show that Ag-NP concentrations as low as 10 ppm exert significant toxicity against Bacillus subtilis, a beneficial bacterium ubiquitous in the soil. Growth arrest and chromosomal DNA degradation were observed, and flow cytometric quantification of propidium iodide (PI) staining also revealed that Ag-NP concentrations of 25 ppm and above increased membrane permeability. RedoxSensor content analysis and Phag-GFP expression analysis further indicated that reductase activity and cytosolic protein expression decreased in B. subtilis cells treated with 10-50 ppm of Ag NPs. We conducted X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses to directly clarify the valence and fine structure of Ag atoms in B. subtilis cells placed in contact with Ag NPs. The results confirmed the Ag species in Ag NP-treated B. subtilis cells as Ag2O, indicating that Ag-NP toxicity is likely mediated by released Ag+ ions from Ag NPs, which penetrate bacterial cells and are subsequently oxidized intracellularly to Ag2O. These findings provide conclusive evidence for the role of Ag+ ions in Ag-NP microbial toxicity, and suggest that the impact of inappropriately disposed Ag NPs to soil and water ecosystems may warrant further investigation.
•MOF-74(Co, Ni) were modified with Pd-loaded activated carbon.•Pristine MOF-74(Ni) and MOF-74(Co) were adsorbed 11.06 and 10.28mmolg−1 of CO2 at 298K and 32bar.•CO2 adsorption capacities were ...enhanced to 12.24 and 11.42mmolg−1 respectively, at same condition after modification.•MOFs are capable to separate CO2 completely from the mixture of CO2/N2 gases.•The CO2/N2 selectivity for MOF-74(Ni)-Pd and MOF-74(Co)-Pd were calculated as 14.6 and 12.4, respectively.
MOF-74(Ni, Co) were synthesized, characterized, modified with Pd-loaded activated carbon (AC) and evaluated for CO2 adsorption capacity and CO2/N2 separation efficiency. The BET specific surface areas of MOF-74(Ni) and MOF-74(Co) were measured as 1418 and 1404m2g−1 with the pore volumes of 0.86 and 0.82cm3g−1, respectively. CO2 adsorption capacity of these MOFs was enhanced with Pd containing AC doping. CO2 adsorption capacities of modified MOF-74(Ni)-Pd and MOF-74(Co)-Pd were 12.24 and 11.42mmolg−1 respectively, measured at 298K and 32bar. The breakthrough curves of mixed CO2/N2 gases demonstrate the complete separation of CO2 from N2 stream. The adsorption and separation of CO2 were facilitated due the interaction between partially negative charge oxygen atoms of polarized CO2 molecule and partially positive Pd metal due to its low electronegativity. The fine structures of synthesized MOFs were further characterized with XANES and EXAFS. The bond distances of Ni–O, and Co–O in synthesized MOF-74(Ni) and MOF-74(Co) are 1.96 and 1.97Å with the coordination numbers of 5.4 and 5.3, respectively.
Hydrogen storage capacity has been investigated on a copper-based metal organic framework named HKUST-1 with fine structural analyses. The crystalline structure of HKUST-1 MOF has been confirmed from ...the powder X-ray diffraction and the average particle diameter has been found about 15–20 μm identified by FE-SEM. Nitrogen adsorption isotherms show that HKUST-1 MOF has approximately type-I isotherm with a BET specific surface area of 1055 m2g−1. Hydrogen adsorption study shows that this material can store 0.47 wt.% of H2 at 303 K and 35 bar. The existence of Cu (II) in crystalline framework of HKUST-1 MOF has been confirmed by pre-edge XANES spectra. The sharp feature at 8985.8 eV in XANES spectra represents the dipole-allowed electron transition from 1s to 4pxy. In addition, EXAFS spectra indicate that HKUST-1 MOF structure has the Cu–O bond distance of 1.95 Å with a coordination number of 4.2.
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► The as-synthesized HKUST-1 MOF was highly pure with almost no impurity. ► Average diameter of HKUST-1 MOF particles was about 15–20 μm. ► Gravimetric H2 uptake of HKUST-1 was 1.95 wt.% carried out at 77 K and 1 bar. ► The Cu–O bond distance in HKUST-1 was 1.95 Å with a coordination number of 4.20. ► HKUST-1 MOF can be used in high temperature systems as it is stable up to 250 °C.
Zinc oxide nanoparticles (ZnO NPs) are an important antimicrobial additive in many industrial applications. However, mass-produced ZnO NPs are ultimately disposed of in the environment, which can ...threaten soil-dwelling microorganisms that play important roles in biodegradation, nutrient recycling, plant protection, and ecological balance. This study sought to understand how ZnO NPs affect Bacillus subtilis, a plant-beneficial bacterium ubiquitously found in soil. The impact of ZnO NPs on B. subtilis growth, FtsZ ring formation, cytosolic protein activity, and biofilm formation were assessed, and our results show that B. subtilis growth is inhibited by high concentrations of ZnO NPs (≥ 50 ppm), with cells exhibiting a prolonged lag phase and delayed medial FtsZ ring formation. RedoxSensor and Phag-GFP fluorescence data further show that at ZnO-NP concentrations above 50 ppm, B. subtilis reductase activity, membrane stability, and protein expression all decrease. SDS-PAGE Stains-All staining results and FT-IR data further demonstrate that ZnO NPs negatively affect exopolysaccharide production. Moreover, it was found that B. subtilis biofilm surface structures became smooth under ZnO-NP concentrations of only 5-10 ppm, with concentrations ≤ 25 ppm significantly reducing biofilm formation activity. XANES and EXAFS spectra analysis further confirmed the presence of ZnO in co-cultured B. subtilis cells, which suggests penetration of cell membranes by either ZnO NPs or toxic Zn+ ions from ionized ZnO NPs, the latter of which may be deionized to ZnO within bacterial cells. Together, these results demonstrate that ZnO NPs can affect B. subtilis viability through the inhibition of cell growth, cytosolic protein expression, and biofilm formation, and suggest that future ZnO-NP waste management strategies would do well to mitigate the potential environmental impact engendered by the disposal of these nanoparticles.
The use of fossil fuels, emission of greenhouse gases (GHG) into the atmosphere, and waste pose a problem to the environment and public health that urgently needs to be dealt with. Among numerous ...chemical activating agents that can be added to anaerobic digestion (AD) to enhance nutrient removal and increase the quality and quantity of biomethane, iron chloride (FeCl3) is the one that has the lowest cost and is the most environmentally friendly. This state-of-the-art review aims to revise the influence of FeCl3 on the Brunauer–Emmett–Teller (BET) surface area of biochar and its ability to increase methane (CH4) yield and remove contaminants from biogas and wastewater. The novelty of the study is that FeCl3, an activating agent, can increase the BET surface area of biochar, and its efficacy increases when combined with zinc chloride or phosphoric acid. Regarding the removal of contaminants from wastewater and biogas, FeCl3 has proven to be an effective coagulant, reducing the chemical oxygen demand (COD) of wastewater and hydrogen sulfide in biogas. The performance of FeCl3 depends on the dosage, pH, and feedstock used. Therefore, FeCl3 can increase the BET surface area of biochar and CH4 yield and remove contaminants from wastewater and biogas. More research is needed to investigate the ability of FeCl3 to remove water vapor and carbon dioxide during biogas production while accounting for a set of other parameters, including FeCl3 size.
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•BET surface area of biochar increases when FeCl3 is combined with ZnCl2.•The amount of H2S removed from biogas depends on the iron chloride dose used.•A circular economy approach of biochar-aided with iron chloride was evaluated.•The factors affecting the efficacy of FeCl3 for wastewater treatment were discussed.
The present work provides a comprehensive overview of the recent progress of research work toward developing new one dimensional (1-D) ceria (CeO(2)) nanomaterials. The review has been classified ...into three parts: the preparation procedures with identification of the existing different dimensional ceria nanomaterials, the formation mechanisms, and an analysis of their applications. From literature survey, it is inaugurated that the fundamental structures of the ceria nanomaterials constructively dominate their properties and applications. In addition, this work will also provide a perspective on the future technical trends for the development of different dimensional CeO(2) nanomaterials.
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•Recent progress of nanoparticles to remediate contaminants from wastewater.•Strategies of nanotechnology in the production and purification of biogas.•Advantage and limitation of ...nanoparticle performances are discussed.•Performance of nanoparticles depends on various factors such as type of feedstock, dosage, pH and type of nanoparticles.
The challenges of managing fossil fuels, the continued emission of greenhouse gases into the atmosphere, and the global water crisis are increasingly drawing researchers’ attention toward alternative ways to increase the efficiency of biogas production and wastewater treatment. To the best of our knowledge, no previous study has yet summarized the performance of nanomaterials in biogas production and the removal of waste contaminants from wastewater. Thus, this current review aims to describe the performance of nanomaterials in biogas production, wastewater treatment, and the removal of contaminants. Based on the identified research, the performance of nanoparticles (NPs) depends significantly on the dosage and feedstock used, the biodegradability of the feedstock, pH, and the type of nanoparticles. For the removal of contaminants, NPs have proved effective at removing CO2 and H2S from biogas, as well as reducing the chemical oxygen demand (COD) and biological oxygen demand (BOD) of wastewater. Based on the evidence, NPs can improve biogas production and reduce contaminants in biogas and wastewater. The use of nanomaterials is recently an advance method over conventional approach for biogas production. The novelty of this study highlights that metal NPs, metal nutrient NPs, and iron oxide NPs are more suitable to increase biogas and CH4 production as compared to metal oxide NPs (e.g., CuO, Mn2O3, Al2O3, and ZnO). More research is needed to investigate the carbon footprint reductions in biogas production and wastewater treatment while accounting for various other parameters, including nanoparticle size and water temperature.
The management of environmental pollution and carbon dioxide (CO2) emissions is a challenge that has spurred increased research interest in determining sustainable alternatives to decrease biowaste. ...This state-of-the-art review aimed to describe the preparation and utilization of carbon-based nanomaterials (CNM) for biogas enhancement and wastewater contaminant (dyes, color, and dust particles) removal. The novelty of this review is that we elucidated that the performance of CNMs in the anaerobic digestion (AD) varies from one system to another. In addition, this review revealed that increasing the pyrolysis temperature can facilitate the transition from one CNM type to another and outlined the methods that can be used to develop CNMs, including arc discharge, chemical exfoliation, and laser ablation. In addition, this study showed that methane (CH4) yield can be slightly increased (e.g. from 33.6% to 60.89%) depending on certain CNM factors, including its type, concentration, and feedstock. Temperature is a fundamental factor involved in the method and carbon sources used for CNM synthesis. This review determined that graphene oxide is not a good additive for biogas and CH4 yield improvement compared with other types of CNM, such as graphene and carbon nanotubes. The efficacy of CNMs in wastewater treatment depends on the temperature and pH of the solution. Therefore, CNMs are good adsorbents for wastewater contaminant removal and are a promising alternative for CO2 emissions reduction. Further research is necessary to determine the relationship between CNM synthesis and preparation costs while accounting for other factors such as gas flow, feedstock, consumption time, and energy consumption.
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•Preparation and characterization of carbon-based nanomaterials (CNMs) are discussed.•Temperature is a fundamental factor in the preparation of CNMs.•The CNMs have great efficacy for methane yield and biogas enhancement.•Graphene oxide has a low toxicity level in biogas production.
Remediation of dense non-aqueous phase liquid (DNAPL), which consists primarily of chlorinated solvents, is considered a top priority in the field of groundwater decontamination. Downward migration ...of DNAPL can lead to formation of impermeable strata due to low solubility and high density. Remediation is therefore one of the most complex technical challenges faced by environmental engineers. In the present work, remediation of trichloroethylene (TCE), perchloroethene (PCE), and 1,2-dichloroethene (1,2-DCE) DNAPL-contaminated groundwater was studied by a reductive reaction with polyethylenimine (PEI) surface-modified zero-valent iron nanoparticles (PEI–nZVI). Compared with fresh nZVI, PEI–nZVI exhibited smaller spherical particles of 20–80 nm and a greater surface area of 53.4 m2/g. Furthermore, slow desorption of the PEI indicated its potential application as a protective shell layer for efficient delivery of active nZVI to the water/DNAPL interface. Laboratory batch remediation results indicate that both nZVI and PEI–nZVI can remove 99% of TCE, PCE, and 1,2-DCE. The rate of reaction for fresh nZVI was higher in the early stage. Comparatively, PEI–nZVI had a higher removal rate and efficiency after 2 h. The kinetic studies also revealed that the removal rate for 1,2-DCE was greater than that for TCE and PCE. Additionally, X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy studies indicated that the nZVI and PEI–nZVI have two central Fe atoms coordinated by primarily FeO and FeFe with bond distances of 1.87 Å and 3.05 Å, respectively. Furthermore, after the reductive reaction, nZVI and PEI–nZVI were oxidized to Fe3O4, and bond distance values for the reacted samples were 1.94 Å and 1.96 Å, respectively.
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•A tiny PEI-nZVI nanocomposite with diameter of 20–80 nm was prepared.•99% of DNAPLs were removed by core-shell PEI-nZVI within 10 min.•Degradation mechanism of DNAPLs over PEI-nZVI surface was proposed.•PEI surface coating enhanced the stability, mobility, and activity of nZVI.•On-site DNAPLs degradation process by shell-soluble PEI-nZVI was designed.
Metal-organic frameworks (MOFs) have had varied applications in the biomedical field for decades, with considerable attention on intelligence-triggered drug delivery. In this study, MIL‒88B(Fe) ...nanomaterials, with gas capture and good biocompatibility, were developed in a fusiform shape. For optimal drug delivery release tests, three Fe sources of MIL‒88B(Fe) were considered for comparing the crystallinity, particle size, morphology, and surface area or pore size distribution. Here, a Pluronic F127 with positive temperature sensitivity was applied during MIL‒88B(Fe) synthesis in a polytetrafluoroethylene-lined autoclave. The pyrolyzed polymer monomers, doped into the lattice during the MIL reassembly, supported the crystallinity and increased the surface area by four times. DLS was used to demonstrate the effectiveness of the changes in particle size distribution. The size distribution of F127‒MIL‒88B(Fe) was sensitive to the increase in temperature, and the size of particles decreased with increasing temperature. As the temperature increased from 25 to 37 °C, the drug release rate of F127‒MIL‒88B(Fe) doubled. The MOFs split into smaller crystals with increase in temperature, which released the drug loaded in the mesoporous frameworks. Thus, polymer-supported F127‒MIL‒88B(Fe) was synthesized with a higher drug capacity based on surface enhancement. Furthermore, a smart temperature-sensitive drug-releasing system was proposed, and it was designed with a releasing allometric kinetics model with release times of t = 0–14.5 h.
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•MIL-88B(Fe) has been synthesized with different iron precursors.•Pluronic F127 applied as support during MIL-88B(Fe) formation.•F127-MIL-88B(Fe) have temperature sensitivity of size.•Drug release rate response positive with temperature raising.
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