In this paper, we show that Au nanoparticles (AuNPs) stabilized with either citrate or by low-generation dendrimers rapidly grow during electrocatalytic reduction of CO2. For example, ...citrate-stabilized AuNPs and AuNPs encapsulated within sixth-generation, hydroxyl-terminated, poly(amidoamine) dendrimers (G6-OH DENs) having diameters of ∼2 nm grow substantially in size (to 6–7 nm) and polydispersity during just 15 min of electrolysis at −0.80 V (vs RHE). This degree of instability makes it impossible to correlate the structure of AuNPs determined prior to electrocatalysis to their catalytic function. In contrast to the G6-OH dendrimer, the higher generation G8-OH analogue stabilizes AuNPs under the same conditions that lead to instability of the other two materials. More specifically, G8-OH DENs having an initial size of 1.7 ± 0.3 nm increase to only 2.2 ± 0.5 nm during electrolysis in 0.10 M NaHCO3 at −0.80 V (vs RHE). Even when the electrolysis is carried out at −1.20 V, the higher-generation dendrimer stabilizes encapsulated AuNPs. This is presumably due to the compactness of the periphery of the G8-OH dendrimer. Although the G8-OH dendrimer nearly eliminates AuNP growth, the surface of the AuNP is still accessible for electrocatalytic reactions. The smaller, more stable G8-OH DENs strongly favor formation of H2 over CO. Some previous reports have suggested that AuNPs in the ∼2 nm size range yield primarily CO, but we believe these findings are a consequence of the growth of the AuNPs during catalysis and do not reflect the true function of ∼2 nm AuNPs.
•TTO alters the morphology and ultrastructure of mitochondria in B. cinerea.•TTO decreases intracellular ATP content and increases extracellular ATP content.•TTO causes mitochondria dysfunction and ...disrupts the TCA cycle in B. cinerea.•Relative ROS levels are increased by TTO treatment.
In order to investigate the effects of tea tree oil (TTO) on mitochondrial morphology and function in Botrytis cinerea, mycelia were treated with TTO at different concentrations. TTO at 2ml/l severely damaged mitochondria, resulting in matrix loss and increased mitochondrial irregularity. Mitochondrial membrane permeability was increased by TTO, as evidenced by a decrease in intracellular adenosine triphosphate (ATP) content and an increase in extracellular ATP content. Increasing concentrations of TTO decreased the activities of enzymes related to mitochondrial function and the tricarboxylic acid (TCA) cycle, affecting malic dehydrogenase, succinate dehydrogenase, ATPase, citrate synthetase, isocitrate dehydrogenase and α-ketoglutarate dehydrogenase, while sharply increasing the level of reactive oxygen species (ROS). These results suggest that mitochondrial damage, resulting in the disruption of the TCA cycle and accumulation of ROS, is involved in the mechanism of TTO antifungal activity against B. cinerea.
It has been hypothesized that the high metabolic flux in the mitochondria is due to the self‐assembly of enzyme supercomplexes (called metabolons) that channel substrates from one enzyme to another, ...but there has been no experimental confirmation of this structure or the channeling. A structural investigation of enzyme organization within the Krebs cycle metabolon was accomplished by in vivo cross‐linking and mass spectrometry. Eight Krebs cycle enzyme components were isolated upon chemical fixation, and interfacial residues between mitochondrial malate dehydrogenase, citrate synthase, and aconitase were identified. Using constraint protein docking, a low‐resolution structure for the three‐enzyme complex was achieved, as well as the two‐fold symmetric octamer. Surface analysis showed formation of electrostatic channeling upon protein–protein association, which is the first structural evidence of substrate channeling in the Krebs cycle metabolon.
Enzymes and channels: Part of the structure of the Krebs cycle metabolon was probed by mass spectrometry. Rational protein docking with cross‐link constraints proposed an association of enzymes giving a two‐fold symmetric octamer composed of two mMDH dimers and two ACON monomers bound to one CS dimer as the core. The electrostatic channels formed by enzyme association are favorable for direct transport of intermediates between active sites.
Magnetite exhibits unique structural, electronic, and magnetic properties in extreme conditions that are of great research interest. In this work, the effects of preparation technique on X‐ray peak ...broadening, magnetic and elastic moduli properties of Fe3O4 nanoparticles prepared by coprecipitation (FcP‐NPs) and citrate (FC‐NPs) methods have been investigated. The structural characterization of the samples is evidence for a cubic structure with Fd‐3m space group. The Williamson‐Hall analysis was used to study crystallite sizes and lattice strain of the samples and also stress and energy density. In addition, the crystallite sizes are compared with the particle sizes and the magnetic core sizes obtained from TEM and VSM methods, respectively. In addition, the cation distribution obtained from calculated inversion parameter indicate that in the smaller particles, more amount of Fe2+ on the tetrahedral sites can be related to higher stress induced in the FcP‐NPs compared to the FC‐NPs. The saturation magnetization of the FcP‐NPs is almost two times bigger than the saturation magnetization of the FC‐NPs. It could be attributed to the decrease in the negative interaction on the octahedral site and also the magnetic moment on the tetrahedral site of the FcP‐NPs. The increase in force constants of the FC‐NPs determined by infrared spectra analysis compared to FcP‐NPs suggests the strengthening of their interatomic bonding. The values of shear and longitudinal wave velocities obtained from force constants have been used to determine the values of Young's modulus, rigidity modulus, bulk modulus, and Debye temperature. By comparison of the elastic results of FC‐NPs with the FcP‐NPs, we can observe that the elastic properties of the F‐NPs have been improved by synthesis method, while Poisson's ratio almost remains constant. In addition, using the values of the compliance sij obtained from elastic stiffness constants, the values of Young's modulus and Poisson's ratio along the oriented direction hkl have been calculated for the samples.
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•Ca(OH)2 treated zeolite exhibited a high P removal efficiency.•Low residual P concentrations were achieved by adsorption onto CaT-Z.•Phosphate adsorption was an endothermic and ...pH-independent process.•Ligand exchange and Ca-P surface precipitation were the dominant sorption mechanisms.•Ca associated P was the major P speciation on the loaded CaT-Z.
Phosphorus (P) recovery from wastewater is of great interest especially when the loaded adsorbent can be used in the agriculture as slow-release fertilizer. The application depends on environmental concerns related to the chemical modification of the adsorbent and the release of toxic compounds from the loaded material to the soil or the water during adsorption. The present work focused on the phosphate (PO4-P) removal from aqueous solutions under low P concentrations (0.5–10mg/L) by using Ca(OH)2-pretreated natural zeolite (CaT-Z). As activation agent, Ca(OH)2 presents benefits in terms of pretreatment costs and environmental impact of the applied adsorbent. The pretreatment of natural zeolite (clinoptilolite) with 0.25mol/L Ca(OH)2 led to an increase of P removal from 1.7 to 97.6% at initial P concentration of 10mg/L, pH 7 and 298K. Low residual concentrations of 81–238μg P/L were achieved at 298K rendering CaT-Z a promising sorbent for tertiary wastewater treatment. At 200mg P/L, the adsorption capacity was 7.57mg P/g CaT-Z. The P removal efficiency was pH-independent suggesting a beneficial use of CaT-Z under acidic and alkaline conditions. Adsorption was found to be an endothermic and slow process reaching equilibrium after 120h, whereas the half of the PO4-P was adsorbed in the first 8h. The applied kinetic models showed that both film and intraparticle diffusion contributed to phosphate removal. Phosphate sorption decreased in the presence of the anionic surfactant SDS, Fe2+, HCO3−, acetate and citrate anion. The predominant mechanisms of ligand exchange and Ca-P surface precipitation were confirmed by the IR-ATR and SEM-EDS analyses, respectively.
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•Over 80% of most of heavy metals can be removed by chlorination during pyrolysis.•P-availability was enhanced by over two times by chlorination during pyrolysis.•Phase transformation ...plays critical role in heavy metal removal and P-availability.•Sewage sludge biochar can be potentially used as P-fertilizer after chlorination.
Increasing attention has been paid on the application of sewage sludge-derived biochar as soil amendments, but is always limited by heavy metals. This study conducted experiments on heavy metal removal by adding chlorinating agents (PVC, NaCl, MgCl2, CaCl2) during sludge pyrolysis. The chlorides addition can largely remove heavy metals by achieving the highest removal efficiency with dosage of 80 g(Cl)/kg(dry sludge) at 700 °C. The most effective removal effect was observed for Zn, Mn, Cu and Pb, with removal efficiency from 37.44% to 99.45%, 5.24% to 93.64%, 9.11% to 86.15% and 16.57% to 90.75%, respectively for the sludge before and after chlorination. Furthermore, the P-solubility in neutral ammonium citrate (Pnac) was enhanced after chlorination and the maximum P-solubility can be obtained at 700 °C for each series. After 700 °C pyrolysis, the P-solubility was significantly increased from 40.08% of the sludge biochar to 72.07%, 74.05%, 74.00% and 76.57% of the biochar obtained after adding PVC, NaCl, CaCl2, and MgCl2, respectively. The highest P-solubility was observed in samples with MgCl2 due to the formation of Mg3(PO4)2. This study proposed a novel method to use the sludge biochar as potential P-fertilizer with effective heavy metal removal, finally achieving a “waste-to-resource” strategy for integrated management of sewage sludge.
Herein, trisodium citrate based magnetite nanocomposite (Fe3O4–TSC) was used for malachite green (MG) dye expulsion from aqueous medium. The adsorption tests were executed at different parameters. ...The maximum adsorption were took place at pH 4 in 40 min. The equilibrium studies were demonstrated using Langmuir and Freundlich isotherms and better agreement was attained with the Langmuir model. The maximum adsorption capacity (q e) was calculated 435 mg g–1 using Langmuir equation. The kinetic parameters displayed that MG adsorption onto Fe3O4–TSC followed pseudo-second-order kinetic model. Furthermore, the thermodynamic analysis suggested the adsorption of MG onto Fe3O4–TSC was impulsive and exothermic. The desorption studies showed the best recovery of MG dye in 0.1 M HCl. Finally, it was found that Fe3O4–TSC can be effortlessly separated from mixed solutions using external magnetic field.
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•Mn0.6Zn0.4Fe2O4 catalyst was fabricated from spent Zn-Mn alkaline batteries.•Mn0.6Zn0.4Fe2O4 catalyst was used to activate PMS and degrade BPA.•The active radicals generated during ...PMS/Mn0.6Zn0.4Fe2O4 process was identified.•The role of A-site metal and Fe(III) of spinel during oxidation was examined.•The importance of surface hydroxyl groups on activation of PMS was confirmed.
Spinel ferrites have shown great potential to activate peroxides for environmental remediation. In this work, a Mn-Zn ferrite catalyst was fabricated by the citrate combustion method from spent Zn-Mn alkaline batteries. The synthesized Mn0.6Zn0.4Fe2O4 catalysts were applied to activate peroxomonosulfate (PMS) and degrade bisphenol A (BPA) in water. A 95.8% BPA (0.1 mM) removal was achieved at initial pH of 6.2, Mn0.6Zn0.4Fe2O4 dosage of 0.2 g/L, PMS concentration of 0.5 mM, and reaction time of 60 min. The concentration of metal leaching and radical identification experiments suggested that BPA is mainly degraded by surface-adsorbed reactive radicals. Metals at A site of the spinel (AFe2O4, A = Mn and Zn) were responsible for PMS activation and Fe(III) acted as the reservoir for the surface hydroxyl groups, which substantially accelerated the degradation of BPA. The addition of Cl− improved the destruction of BPA and a NaHCO3 concentration below 5 mM had a negligible effect on the BPA removal. When the PMS/Mn0.6Zn0.4Fe2O4 process was used to treat real river water spiked with BPA, the removal of BPA was much faster than that in deionized water. This implied that the PMS/Mn0.6Zn0.4Fe2O4 process may provide some new insights not only for the recycling of spent batteries, but also for removal of contaminants from wastewater.
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•ZrO2 was added to CaO-based sorbent for enhanced high-temperature CO2 sorption.•The effects of physically mixed Zr and chemically bonded Zr were compared.•ZrO2 could be well ...distributed on the CaO-based sorbent with chemically bonded Zr.•The chemically bonded Zr could effectively hinder the thermal sintering of CaO.•Outstanding CO2 sorption of ∼70.5 wt% could be achieved during 10 cycles.
In this study, ZrO2 is introduced in a new form to reduce sintering and enhance the cyclic stability of CaO-based sorbents. Such a material has potential for high-temperature CO2 capture applications. Two Zr-modified CaO materials having a Ca/Zr molar ratio of 30 are prepared using the solid-state and citrate sol-gel methods. The solid-state method yields a physical mixture of CaO and ZrO2, while the citrate sol-gel method induces chemical bonding between ZrO2 and the CaO surface to form CaZrO3. The CO2 sorption uptake was significantly increased in both unmodified CaO and ZrO2-containing CaO 77.3 wt% (17.6 mol kg−1) and 73.2 wt% (16.6 mol kg−1), respectively, at 650 °C and 1 bar when the citrate sol-gel method was used. The CaO having the chemically bonded ZrO2 reveals significantly enhanced cyclic stabilities, with an extremely high CO2 sorption uptake of 70.5 wt% (16.0 mol kg−1) on average during 10 cycles. On the other hand, the CaO containing the physically mixed ZrO2 reveals an average cyclic CO2 sorption uptake of only 37.2 wt% (8.5 mol kg−1). The chemically bonded ZrO2 is expected to be well scattered on the CaO surface and effectively cover the sorbent, resulting in the reduction of thermal sintering. In addition to cyclic stability, CO2 sorption kinetics of CaO-based sorbents can be enhanced through the citrate sol-gel method, which is resulted from the significantly reduced size of CaO particles.
Mucor circinelloides has been commonly used as the model microbe to investigate lipid production as an oleaginous fungus. Mitochondrial citrate transporter can catalyze the translocation of the ...citrate, accumulated from TCA cycle, across the mitochondrial inner membrane. The extra-mitochondrial citrate is then cleaved by ATP-citrate lyase to oxaloacetate (OAA) and acetyl-CoA. Acetyl-CoA together with NADPH generated in cytosol is used for fatty acid biosynthesis. Thus, citrate transporters provide a link between TCA cycle in mitochondria and fatty acid biosynthesis in cytosol. However, the role of citrate transporters for lipid accumulation in oleaginous fungi is not clear. Two genes coding for citrate transporters, named citrate transporter (ct) and tricarboxylate transporter (tct) respectively, were present in the genome of oleaginous fungus M. circinelloides WJ11, a high lipid producing strain (36%, lipid/cell dry weight). As the mutant of strain CBS 277.49 (15%, lipid/cell dry weight) has been constructed and its genetic engineering tools are available for gene manipulation, so in this work, we investigated the role of citrate transporters in regulating lipid biosynthesis by overexpressing the citrate transporters of M. circinelloides WJ11 in CBS 277.49. Results: Our results showed that overexpression of ct and tct led to increased lipid accumulation by 44% (from 13.0% to 18.8%, w/w, CDW) and 68% (from 13.0% to 21.8%, w/w, CDW), respectively. Moreover, extracellular citrate concentration in ct-overexpressing strains (4.91 mM) and tct-overexpressing (3.25 mM) were significantly decreased by 20% and 47% respectively compared to the control (6.09 mM). Furthermore, overexpression of the citrate transporter genes activated the downstream steps in lipid biosynthesis, such as ATP citrate lyase (acl gene) and fatty acid synthases (fas1 and fas2 genes), indicating a greater flux of carbon went into fatty acid biosynthesis. Conclusions: This is the first report showing that citrate transporters involved in lipid accumulation in M. circinelloides. Both citrate transporter and tricarboxylate transporter could transport mitochondrial citrate to cytoplasm, which could provide more citrate to be cleaved by increased ACL to provide more acetyl-CoA and NADPH for increased FAS to synthesize fatty acids, thus, play a vital role in lipid biosynthesis in oleaginous fungus M. circinelloides.
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