Metal Ions Cu2 Research Articles

Inhibiting mechanisms of metal ion complexation on photogenerated reactive intermediates derived from dissolved black carbon

Dissolved black carbon (DBC), an important photosensitizer in surface waters, can influence the photodegradation of various organic micropollutants. In natural water systems, DBC often co-occurs with metal ions as DBC–metal ion complexes; however, the influence of metal ion complexation on the photochemical activity of DBC is still unclear. Herein, the effects of metal ion complexation were investigated using common metal ions (Mn2+, Cr3+, Cu2+, Fe3+, Zn2+, Al3+, Ca2+, and Mg2+). Complexation constants (logKM) derived from three-dimensional fluorescence spectra revealed that Mn2+, Cr3+, Cu2+, Fe3+, Zn2+, and Al3+ quenched the fluorescence components of DBC via static quenching. The steady-state radical experiment suggested that in the complex systems of DBC with various metal ions, Mn2+, Cr3+, Cu2+, Fe3+, Zn2+ and Al3+ inhibited the photogeneration of 3DBC* via dynamic quenching, which reduced the yields of 3DBC*-derived 1O2 and O2·-. Moreover, 3DBC* quenching by metal ions was associated with the complexation constant. A strong positive linear relationship existed between logKM and the dynamic quenching rate constant of metal ions. These results indicate that the strong complexation ability of metal ions enabled 3DBC quenching, which highlights the photochemical activity of DBC in natural aquatic environments enriched with metal ions.

The efficient degradation of high concentration phenol by Nitrogen-doped perovskite La2CuO4 via catalytic wet air oxidation: Experimental study and DFT calculation

Herein, N-doped perovskite La2CuO4 (LCO) (N-LCO(M)) was fabricated by sol–gel rapid calcination method using melamine (M) as N source/ligand, and applied for the catalytic wet air oxidation (CWAO) to degrade high-concentration phenol-containing simulated wastewater. The experimental results exhibited that N-LCO(M) illustrated enhanced phenol degradation efficiency. Thereinto, 87.9% COD degradation efficiency was achieved in simulated wastewater containing 8000 mg/L phenol, while for undoped LCO prepared with citric acid (CA) as ligand (LCO(CA)) was only 43.8%. The systematic characterizations and density functional theory (DFT) calculations were utilized to verify the above results. The results revealed that N doping favored the formation of more oxygen vacancies (*) and facilitated the charge transfer between Cu and O. More oxygen vacancies (*) reinforced the ability of N-LCO(M) to adsorb O2 to form reactive oxygen species (O*), and meanwhile, the charge transfer between Cu and O was manifested as the redox cycle of the catalytic active metal Cu2+/Cu1+. The redox cycle also promoted the formation of O2− and HO, making the more exhaustive degradation of phenol. This successfully proved that N doping was core to improving the activity and stability of N-LCO(M). Moreover, a possible mechanism of phenol degradation was proposed based on the experimental results and DFT calculations. Eventually, the toxicity of the intermediate products was further evaluated by quantitative structure–activity relationship (QSAR) analysis, showing the significantly reduced toxicity of the intermediate products. Overall, the proposed CWAO technique is a green and promising wastewater treatment method.

English

β-glucosidases are found in all domains of life and has the ability to hydrolyse the glycosidic bond between carbohydrates and non-carbohydrates residues making it a potent enzyme from an industrial and agricultural perspective. The aim of the current study was isolation, screening, and identification of bacterial strains having maximum β-glucosidase activity from soil sample of Jacobabad, Pakistan. The isolates were screened primarily, and efficient isolates were confirmed for β-glucosidase production through secondary screening. Among the different isolated strains, 1j2 was selected as the best β-glucosidase producer. The isolate showed 99% similarity with Bacillus stercoris after 16S rRNA sequencing. Different culture conditions were optimized for effective β-glucosidase production. Enhanced level of β-glucosidase was achieved at 40°C, pH 8 at 150 rpm in a β-glucosidase production medium supplemented with a combination of agricultural residues of wheat bran 0.25% (w/v) and orange peel 0.25% (w/v), using 5% inoculum. Bacillus stercoris produced a higher yield (2.89U/mg) of β-glucosidase under optimized conditions. Partial purification of β-glucosidase was achieved after 80% ammonium sulfate precipitation. The enzyme was purified and had shown maximum specific activity of 53.2 U/mg with molecular weight of approximately 36 kDa. In all the tested metals Cu2+ was observed to have inhibitory effect while Ca2+ had not affected the enzyme activity significantly. While organic solvents and surfactants had significantly reduced the β-glucosidase activity. Based on the afore mentioned abilities of purified β-glucosidase from Bacillus stercoris strain it could be a promising player for the industrial applications of lignocellulose hydrolysis found in agricultural residues for the cheap production of biofuels.

Enhanced separation capacity of carbonaceous materials (hydrochar, biochar, and activated carbon) toward potential toxic metals through grafting copolymerization

Oxygen-containing groups on the surfaces of materials (i.e., –COOH and –OH) are vital to the adsorption of toxic metals. Acrylic acid is used as a green grafter to enhance the density of these groups in carbonaceous materials, whereas ammonium cerium nitrate is used as an initiator. Hydrochar (prepared via hydrothermal carbonization at 190 °C), biochar (generated via pyrolysis at 800 °C), and activated carbon (AC; generated via chemical activation with K2CO3 at 800 °C) derived from ginger residues are used as feedstock materials for the grafting process. Carbonaceous materials are characterized using scanning electron microscopy, X-ray photoelectron spectrometry, Brunauer–Emmett–Teller analysis, Fourier transform infrared spectroscopy, and zeta potential measurements. Cu2+, Cd2+, and Pb2+ are selected as adsorbates. Equilibrium adsorption experiments for the three metal ions on ungrafted and grafted carbonaceous materials are conducted at 25 °C and pH 5.0. Results indicated that the oxygen content in the grafted material is higher than that in the ungrafted material. Grafting can increase the number of OH and COOH functional groups on the carbonaceous materials, thus resulting in more metal ions being absorbed. The Langmuir maximum adsorption capacity (Qmax) of the carbonaceous materials for the toxic metal ions (mol/kg) is ranked in the order Cu2+ > Cd2+ > Pb2+. The amount of potentially toxic metal ions adsorbed on the ungrafted and grafted (abbreviated as G) materials are in the order hydrochar > AC > biochar. The Qmax values of hydrochar (72.8, 74.7, and 109.3 mg/g), biochar (53.6, 69.1, and 53.9 mg/g), AC (54.4, 73.1, and 101.8 mg/g), G-hydrochar (130.9, 146.0, and 271.4 mg/g), G-biochar (92.6, 143.6, and 153.6 mg/g), and G-AC (96.3, 146.1, and 259.1 mg/g) for the adsorbing metals (Cu2+, Cd2+, and Pb2+) are higher than that of commercial activated carbon (21.83, 22.13, and 25.15 mg/g, respectively). The adsorption capacity of the grafted hydrochar is restored after five adsorption–desorption cycles. The primary adsorption mechanisms are complexation and ion exchange.

Enhancing the CO2, CH4, and N2 adsorption and kinetic performance on FAU zeolites for CO2 capture from flue gas by metal incorporation technique

Various metals including alkali (Na+, K+), alkaline earth (Mg2+ and Ca2+), and transition metals (Cu2+ and Fe3+) were successfully incorporated into the structure of faujasite zeolites (X and Y) by novel post-synthesis modification method. The effect of metal-doping on the CO2, CH4, and N2 adsorption and kinetic performance in the context of flue gas carbon capture and natural gas purification was examined by four approaches; (i) the impact on structural properties was examined by XRD, FTIR, UV–visible, H2-TPR, FESEM, EDX Dot-Mapping, and BET analysis; (ii) the influence on the CO2, CH4, and N2 adsorption capacity was acquired by volumetric method up to 100 kPa at 25 °C (iii) the effect on binary CO2/CH4 and CO2/N2 selectivity was determined by the Henry constant and IAST selectivity; (iv) the micropore - macropore kinetic model was utilized to study the influence on diffusion coefficients. The dual-site Langmuir-Freundlich (DSLF) isotherm was found to be the best adaptability to the experimental isotherms data. The results showed an extraordinary increase in CO2 absorption capacity to 4.9 and 7 for KX and KY, respectively. Faujasite zeolite with a lower Si/Al ratio (zeolite X) outperforms CO2/CH4 and CO2/N2 separation performance than higher ones (zeolite Y). Among all samples, KX showed the highest CO2/CH4 and CO2/N2 IAST selectivity with values of 61 and 152 at 100 kPa, respectively, in addition to the highest diffusion coefficients for CH4 and N2. The incorporated potassium metal into the faujasite zeolites showed promising sorbents for the separation of CO2 from flue gas and natural gas streams.

SORPTION OF IONS OF SOME METAL ON CLINOPTILOLITE IN THE PRESENCE OF GALLIC ACID

The Gibbs energy changes for the reaction between the copper, cadmium, and lead ions complexes with gallic acid and clinoptilolite containing single-charged (Na, K) and double-charged (Ca, Mg) exchange ions were calculated. The software PRIRODA with the PBE/3ζ theoretical method has been used for these calculations:
 (GalAn)2X×2H2O + Clin-Me + 2H3O+ → X(H2O)n-Clin + 2GalAn– + (6-n)H2O + 2Me+(Me2+).
 The thermodynamic possibility of spontaneous ion exchange between complexes of heavy metal ions (Cu2+, Cd2+, Pb2+) with gallic acid and exchange ions of clinoptilolite was shown. This indicates the possibility of removal of these ions from the soil, with their coordination by polyphenols. The possibility of a significant decrease in the content of Cu2+, Cd2+, and Pb2+ ions was investigated both in the absence of gallic acid and in its presence in solution (initial concentration of metal ions of 2 mmol/l, the ratio of Me2+: gallic acid is 1:0, 1:1, and 1:2). It has been found that the sodium form of clinoptilolite influences the growth of sorption properties of clinoptilolite, allowing to exclude 22% more copper ions, compared to the natural clinoptilolite of Sokyrnytsya deposit. Two mechanisms for reducing the concentration of heavy metals in soil have been proposed.
 Keywords: clinoptilolite; sorption; heavy metal; quantum-chemical calculations; gallic acid.

Preparation of Eco-Friendly Chelating Resins and Their Applications for Water Treatment.

In the present study, two chelating resins were prepared and used for simultaneous adsorption of toxic metal ions, i.e., Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, and Pb2+ (MX+). In the first step, chelating resins were prepared starting with styrene-divinylbenzene resin, a strong basic anion exchanger Amberlite IRA 402(Cl-) with two chelating agents, i.e., tartrazine (TAR) and amido black 10B (AB 10B). Key parameters such as contact time, pH, initial concentration, and stability were evaluated for the obtained chelating resins (IRA 402/TAR and IRA 402/AB 10B). The obtained chelating resins show excellent stability in 2M HCl, 2M NaOH, and also in ethanol (EtOH) medium. The stability of the chelating resins decreased when the combined mixture (2M HCl:EtOH = 2:1) was added. The above-mentioned aspect was more evident for IRA 402/TAR compared to IRA 402/AB 10B. Taking into account the higher stability of the IRA 402/TAR and IRA 402/AB 10B resins, in a second step, adsorption studies were carried out on complex acid effluents polluted with MX+. The adsorption of MX+ from an acidic aqueous medium on the chelating resins was evaluated using the ICP-MS method. The following affinity series under competitive analysis for IRA 402/TAR was obtained: Fe3+(44 µg/g) > Ni2+(39.8 µg/g) > Cd2+(34 µg/g) > Cr3+(33.2 µg/g) > Pb2+(32.7 µg/g) > Cu2+ (32.5 µg/g) > Mn2+(31 µg/g) > Co2+(29 µg/g) > Zn2+ (27.5 µg/g). While for IRA 402/AB 10B, the following behavior was observed: Fe3+(58 µg/g) > Ni2+(43.5 µg/g) > Cd2+(43 µg/g) > Cu2+(38 µg/g) > Cr3+(35 µg/g) > Pb2+(34.5 µg/g) > Co2+(32.8 µg/g) > Mn2+(33 µg/g) > Zn2+(32 µg/g), consistent with the decreasing affinity of MX+ for chelate resin. The chelating resins were characterized using TG, FTIR, and SEM analysis. The obtained results showed that the chelating resins prepared have promising potential for wastewater treatment in the context of the circular economy approach.

Synthesis of hydrogel nanocomposites and their application in removing dyes and impurities

Polyacrylate hydrogels containing starch, ZeSe and Fe3O4 nanoparticles were obtained. The polymerization process was carried out in an ultrasonic field. The structure (SEM, FTIR), swelling properties and the ability of hydrogels to adsorb dyes (methylene blue, methyl orange, methyl red and Eriochrome black T) and heavy metals (Cu2+) from wastewater were investigated. Hydrogels containing AgCl nanoparticles were also obtained.

A Dye-Assisted Paper-Based Assay to Rapidly Differentiate the Stress of Chlorophenols and Heavy Metals on Enterococcus faecalis and Escherichia coli

Biological toxicity testing plays an essential role in identifying the possible negative effects induced by substances such as organic pollutants or heavy metals. As an alternative to conventional methods of toxicity detection, paper-based analytical device (PAD) offers advantages in terms of convenience, quick results, environmental friendliness, and cost-effectiveness. However, detecting the toxicity of both organic pollutants and heavy metals is challenging for a PAD. Here, we show the evaluation of biotoxicity testing for chlorophenols (pentachlorophenol, 2,4-dichlorophenol, and 4-chlorophenol) and heavy metals (Cu2+, Zn2+, and Pb2+) by a resazurin-integrated PAD. The results were achieved by observing the colourimetric response of bacteria (Enterococcus faecalis and Escherichia coli) to resazurin reduction on the PAD. The toxicity responses of E. faecalis-PAD and E. coli-PAD to chlorophenols and heavy metals can be read within 10 min and 40 min, respectively. Compared to the traditional growth inhibition experiments for toxicity measuring which takes at least 3 h, the resazurin-integrated PAD can recognize toxicity differences between studied chlorophenols and between studied heavy metals within 40 min.

Изучение возможности взаимодействия различных металлов с альфа-2-макроглобулином и другими белками крови человека in vitro

Homeostasis of metals plays an important role in functioning of the body. Not only the concentrations of toxic and essential metals in bodily fluids, but also their ability of interaction with proteins and enzymes defining the enzyme activity, are important. The study was aimed to compare the possibilities of binding interactions between various metal ions and human serum proteins. Chemical reactions between the immobilized metal ions (Cu2+, Zn2+, Mn2+, Ca2+, Fe3+, Mg2+, Hg+, Cd2+, Pb2+, Cr3+, Co2+, Ag+, Bi2+, Ba2+, Sr2+) and the serum proteins or highly purified blood metalloprotein (alpha-2-macroglobulin, α2M) were assessed by the crossed immunoelectrophoresis with in situ adsorption in the second dimension. It has been shown that Hg+, Cu2+, Zn2+, Cd2+ ions more actively interact with metalloproteins (particularly, with α2M) and many other human blood proteins in in vitro reactions than other ions. We have demonstrated that α2M interacts not only with Zn2+ and Cd2+ ions, as earlier reported, but also with Ca2+, Mg2+, Fe3+, Mn2+, Pb2+, Sr2, Ag+. Interaction of a number of metal ions, including highly toxic ones, with blood proteins that are not metalloproteins has been revealed. The findings confirm the fundamental possibility of the metal ion imbalance active involvement in metabolic disorders via effects on the body's regulatory and transport proteins, which requires further investigation

Mussel inspired Cu-tannic autocatalytic strategy for rapid self-polymerization of conductive and adhesive hydrogel sensors with extreme environmental tolerance

Conductive hydrogels have broad application prospects in skin sensors and biomedical monitoring. However, the time-consuming and energy-consuming polymerization process and functional declination in harsh environments hinder its practical application. Herein, highly ionic conductive hydrogels with adhesiveness, flexibility, water-retention and anti-freezing properties are fabricated by a facile and rapid strategy through the combination of tannic acid coated cellulose nanofibers (TA@CNF), metal ion Cu2+, glycerol and polyacrylamide (PAM) chains. Interestingly, the reversible redox catalytic system constructed by TA and Cu2+ in an alkaline environment can significantly shorten the time required (<1 min) for hydrogel polymerization at room temperature. Meanwhile, hydrogen bonds between glycerol and water molecules elevate hydrogel environmental tolerance (-20 to 60 °C), endowing them with excellent flexibility and reproducible adhesion in a long-term usage environment. CNFs, as nano-reinforcements, construct a three-dimensional network structure with PAM for energy dissipation through multiple bonding and endowing the hydrogel with excellent mechanical strength (156.4 kPa) and stretchability (1624.8 %) while providing a tough and stable electron transport network for copper ions, which in turn exhibits excellent electrical conductivity (43.6 mS/m). Obviously, this strategy of preparing multifunctional hydrogels based on catechol metal ion rapid catalytic system will provide a new way for the design and development of advanced skin sensors.

3D Vascular-structured Flame-retardant Cellulose-based photothermal aerogel for Solar-driven interfacial evaporation and wastewater purification

Solar-driven interfacial evaporation is recognized as a green and sustainable strategy to address the global freshwater problem. Efficient vapor generation relies on the creation of high-performance evaporators, which concentrate on improving solar energy conversion efficiency, water transport capacity and thermal localization. Herein, a functionalized cellulose aerogel with a novel three-dimensional vascular structure was designed by decorating the cellulose nanofiber with ZIF-67 and MXene (CZM3), which can be used as a solar-driven multifunctional evaporator. When exposed to 1 sun, the CZM3 aerogel demonstrated a high evaporation rate of 2.034 Kg·m−2·h−1 and an efficiency of 139.4 %, outperforming many advanced evaporators. What’s more, CZM3 aerogel maintained its stable water evaporation property after multiple test cycles. This was due to the hydrophilic vascular-like channels continuously transport water, while the photothermal materials encapsulated in CNF provide the power for water vaporization. Additionally, through the interfacial evaporation of CZM aerogel, the removal rates of salt ions (Na+, Mg2+, Ca2+ and K+) and heavy metal ions (Cu2+, Zn2+ and Cd2+) reached 98.2 %∼99.5 % and 81.6 %∼98.2 %, showing outstanding water purification ability. Contrary to the flammability of pure CNF, the peak heat release rate and total heat release of CZM3 aerogel were reduced by 75.2 % and 69.9 %, exhibiting superior fire safety. The high-performance evaporator designed in this work becomes a promising candidate material in the field of solar-driven water desalination and wastewater purification.

Controllable synthesis of CuPc/N-rich doped (0 0 1) TiO2 S-scheme nanosheet heterojunctions for efficiently wide-visible light-driven CO2 reduction

Inspired by natural photosynthesis, the rational design of efficient S-scheme heterojunctions holds promises for CO2 conversion by utilizing solar light. Herein, nitrogen-rich doped 001-exposed anatase nanosheets (NPT) have been designed and fabricated by post-treatment with NH3 at a high temperature of 600 °C to phosphate modified TiO2 firstly, and then controllably coupled with copper phthalocyanine (CuPc) via a hydroxyl-induced assembly process to construct a wide-visible-light responsive heterojunction towards CO2 conversion. The optimized CuPc/NPT heterojunction achieves a high production rate of CO (∼5 μmol/g/h) under visible light irradiation, with ∼9-fold enhancement compared with generally N-doped TiO2. Based on the experimental results mainly from photocurrent action spectra, electron paramagnetic resonance measurements, electrochemical reduction curves and in-situ diffuse reflectance infrared Fourier transform spectra, it is confirmed that the exceptional photoactivity is attributed to the N-rich doping for increasing visible-light absorption of TiO2, the effective S-scheme charge transfer from the closely-contacted CuPc/NPT heterojunction with wide visible-light absorption, and subsequently to the electron transfer from the Pc ligand to central metal Cu2+ with good catalytic function for CO2 reduction. This work provides feasible routes for the design and preparation of TiO2-based photocatalysts for solar-driven CO2 conversion.

A simple TICT/ICT based molecular probe exhibiting ratiometric fluorescence Turn-On response in selective detection of Cu2+

The work reported herein describes photophysical behavior of a new fluorescent probe APDA. The probe exhibited sensitivity for Cu2+ ion in 80% aqueous acetonitrile medium. Probe shows dual emission due to TICT and ICT states and upon interaction with different metal ions Cu2+ induces hydrolysis of imine bond to rejuvenate aldehyde derivative with ratiometric “turn–On” fluorescence response, through ICT state while emission due to TICT state get diminished. Similarly, the synthesized model compound ADA under similar experimental condition supported hydrolysis of imine bond in the presence of copper. Jobs plot analysis, based on emission titration data suggested a 1:1 binding stoichiometry between probe APDA and Cu2+ ion. The limit of detection (LOD) was found to be 4.4 × 10-8 M (44 nM). The probe has been applied on test paper strip to detect Cu2+ ion with naked-eye sensitive response. Also, the cell imaging studies revealed the potential applicability of probe to detect Cu2+ ion in live cells. The mechanism of sensing was confirmed by 1H, 13C NMR, FTIR and mass spectrometry data analysis.

The ion flotation of copper, nickel, and cobalt using the biosurfactant surfactin

Heavy metal contaminated waters are a significant environmental hazard, which require novel treatment methodologies. Further, the metals which might be recovered from these streams have significant intrinsic value, if they can be collected and concentrated. This work demonstrates, for the first time, the use of surfactin, an environmentally benign biosurfactant, for the flotation of metal ions (Cu2+, Ni2+, and Co2+). Surfactin, at a molar ratio of 1:3, has been shown to float 75.2%, 94.7%, and 98.2% of initial 100 mu M solutions of copper nickel and cobalt, respectively. Increasing the gas flow rate modifies the float by increasing the carryover of water into the overflow. A pH of 5 was found to be ineffective (due to surfactin precipitation), while a pH of 10 was less effective than pH 7, likely due to the ionic speciation of the metals in solution tending to hydroxyl precipitates at a high pH. This work demonstrates an opportunity for the recovery of metals (at low concentrations) using biosurfactant-based froth flotation.

Low temperature pyrolytic biochar is a preferred choice for sulfonamide-Cu(II) contaminated soil remediation in tropical climate region

Biochar is getting increasing consideration for eco-friendly soil amendment and environmental remediation. Once added to the soil, biochar would undergo the natural ageing process, affecting its physicochemical properties and, as a result, the adsorption and immobilization of pollutants in the water and soil. To evaluate the high/low temperature pyrolyzed biochar performance on complex contaminants and the effect of climate ageing, the batch experiments were conducted on the adsorption of the pollutants of antibiotics sulfapyridine (SPY) and a typical coexisting heavy metal Cu2+ as one or binary system on low/high pyrolytic temperature biochars before and after the simulated tropical climate and frigid climate region ageing treatment. The results showed that high-temperature ageing could enhance the SPY adsorption in biochar-amended soil. The SPY sorption mechanism was fully elucidated, and the result confirmed that H-bonding was the dominant role in biochar-amended soil, and π-π electron-donor-acceptor (EDA) interaction and micro-pore filling was another factor for SPY adsorption. This study could lead to the conclusion that low-temperature pyrolytic biochar is a better option for sulfonamide-Cu(II) contaminated soil remediation in tropical regions.

A highly sensitive and specific luminescent MOF determines nitric oxide production and quantifies hydrogen sulfide-mediated inhibition of nitric oxide in living cells.

The synthesis of a novel carboxylate-type organic linker-based luminescent MOF (Zn(H2L) (L1)) (named PUC2) (H2L = 2-aminoterephtalic acid, L1 = 1-(3-aminopropyl) imidazole) is reported by the solvothermal method and comprehensively characterized using single-crystal XRD, PXRD, FTIR, TGA, XPS, FESEM, HRTEM, and BET. PUC2 selectively reacts with nitric oxide (▪NO) with a detection limit of 0.08µM, and a quenching constant (0.5 × 104M-1) indicating a strong interaction with ▪NO. PUC2 sensitivity remains unaffected by cellular proteins or biologically relevant metals (Cu2+/ Fe3+/Mg2+/ Na+/K+/Zn2+), RNS/ROS, or H2S to score ▪NO in living cells. Lastly, we used PUC2 to demonstrate that H2S inhibition increases ▪NO production by ~ 14-30% in various living cells while exogenous H2S suppresses ▪NO production, indicating that the modulation of cellular ▪NO production by H2S is rather generic and not restricted to a particular cell type. In conclusion, PUC2 can successfully detect ▪NO production in living cells and environmental samples with considerable potential for its application in improving the understanding of the role of ▪NO in biological samples and study the inter-relationship between ▪NO and H2S.

Metal-Responsive Transcription Factors Co-Regulate Anti-Sigma Factor (Rsd) and Ribosome Dimerization Factor Expression.

Bacteria exposed to stress survive by regulating the expression of several genes at the transcriptional and translational levels. For instance, in Escherichia coli, when growth is arrested in response to stress, such as nutrient starvation, the anti-sigma factor Rsd is expressed to inactivate the global regulator RpoD and activate the sigma factor RpoS. However, ribosome modulation factor (RMF) expressed in response to growth arrest binds to 70S ribosomes to form inactive 100S ribosomes and inhibit translational activity. Moreover, stress due to fluctuations in the concentration of metal ions essential for various intracellular pathways is regulated by a homeostatic mechanism involving metal-responsive transcription factors (TFs). Therefore, in this study, we examined the binding of a few metal-responsive TFs to the promoter regions of rsd and rmf through promoter-specific TF screening and studied the effects of these TFs on the expression of rsd and rmf in each TF gene-deficient E. coli strain through quantitative PCR, Western blot imaging, and 100S ribosome formation analysis. Our results suggest that several metal-responsive TFs (CueR, Fur, KdpE, MntR, NhaR, PhoP, ZntR, and ZraR) and metal ions (Cu2+, Fe2+, K+, Mn2+, Na+, Mg2+, and Zn2+) influence rsd and rmf gene expression while regulating transcriptional and translational activities.

Type-wide biochars loaded with Mg/Al layered double hydroxide as adsorbent for phosphate and mixed heavy metal ions in water

This study discussed the adsorption of mixed heavy metal ions (Cu2+, Co2+, Pb2+) and phosphate ions by ten pristine biochars and those with precipitated Mg/Al layered double hydroxide (LDH). The pristine biochars have adsorption capacities of 6.9–13.4 mg/g for Cu2+, 1.1−9.7 mg/g for Co2+, 7.8−20.7 mg/g for Pb2+, and 0.8−4.9 mg/g for PO43−. The LDH-biochars have markedly increased adsorption capacities of 20.4–25.8 mg/g for Cu2+, 8.6−15.0 mg/g for Co2+, 26.5−40.4 mg/g for Pb2+ with mixed metal ions, and 13.0−21.8 mg/g for PO43−. Part of the Mg ions but Al ions are released from the LDH-biochars during adsorption, counting less than 7.2% of the adsorbed ions. The pristine biochars have specific adsorption sites for Cu2+ and Co2+, separate Pb2+ sites related to ether groups on biochar, and areal-dependent sites for PO43−. There is no universal adsorption mechanism corresponding to mixed metal ion adsorption for individual pristine biochar involving different contributions of C–O–C, C–O–H, and CO groups and graphitic-N, pyrrolic-N, and pyridine-N groups. The LDH complexes with hydroxyl and carbonyl groups of biochar, and the LDH interacts with biochar's ether groups, which contributes to metal adsorption, against the conception that the biochar is merely a carrier of LDH as adsorbents.

Metal ion-catalyzed interfacial polymerization of functionalized covalent organic framework films for efficient separation

Covalent organic frameworks (COFs), with high porosity, uniform and tunable pore size, which are advantageous to prepare defect-free membranes with high separation performance and high permeability, and have achieved efficient applications in the field of separation membranes in numerous directions. According to our knowledge, the transition metal ion (Cu2+) which is used in Schiff base condensation reaction has been rarely described. Herein, we report the interfacial polymerization of ternary amines and binary aldehyde monomers via the catalyst Cu(ClO4)2·6H2O. In this work, we report the fabrication of covalent organic framework films from four different functional structure monomers by using the transition metal ion-catalyzed interfacial polymerization at room temperature. The four as-synthesized films are flexible, continuous, defect-free and have large areas, which have excellent performance in the direction of dye separation as well as solvent penetration. After the COF films were transferred to the polyethersulfone support, the composite films exhibited enhance the rejection of methylene blue (98.43%), high-water flux (81.46 L m−2 h−1 bar−1) and solvent flux (ethanol (13.03 L m−2 h−1 bar−1), acetonitrile (50.38 L m−2 h−1 bar−1)). The large area, tunable pore size, and tailored molecular composite membranes show potential for nanofiltration applications.