Metals Manganese Research Articles

Manganese(II) and Zinc(II) metal complexes of novel bidentate formamide-based Schiff base ligand: synthesis, structural characterization, antioxidant, antibacterial, and in-silico molecular docking study.

A new bidentate Schiff base ligand (C16H16Cl2N4), condensation product of ethylene diamine and 4-chloro N-phenyl formamide, and its metal complexes [M(C16H16Cl2N4)2(OAc)2] (where M = Mn(II) and Zn(II)) were synthesized and characterized using various analytical and spectral techniques, including high-resolution mass spectrometry (HRMS), elemental analysis, ultraviolet-visible (UV-vis), Fourier-transform infrared (FTIR) spectroscopy, AAS, molar conductance, 1H NMR, and powder XRD. All the compounds were non-electrolytes and nanocrystalline. The synthesized compounds were assessed for antioxidant potential by DPPH radical scavenging and FRAP assay, with BHT serving as the positive control. Inhibitory concentration at 50% inhibition (IC50) values were calculated and used for comparative analysis. Furthermore, the prepared compounds were screened for antibacterial activity against two Gram-negative bacteria (Staphylococcus aureus and Bacillus subtilis) and two Gram-positive bacteria (Escherichia coli and Salmonella typhi) using disk-diffusion methods, with amikacin employed as the standard reference. The comparison of inhibition zones revealed that the complexes showed better antibacterial activity than the ligand. To gain insights into the molecular interactions underlying the antibacterial activity, the ligand and complexes were analyzed for their binding affinity with S. aureus tyrosyl-tRNA synthetase (PDB ID: 1JIL) and S. typhi cell membrane protein OmpF complex (PDB ID: 4KR4). These analyses revealed robust interactions, validating the observed antibacterial effects against the tested bacterial strains.

Current status of stream water quality around selected Tea Gardens from Southern Western Ghats, Tamil Nadu, India – A case study

In this study, metal concentration in tea garden-associated stream water samples from the south Western Ghats of Tamil Nadu was evaluated using ICP-MS to know the current status of pollution level, sources of pollution, probable water quality, and impacts of heavy metals. Stream water pollution of hill regions communities using the heavy metal pollution index, principal compound analysis, and Pearson correlation analysis were measured. In addition, for this purpose, water phy-chem parameters were also measured, such as (pH, temperature, conductivity, salinity, and TDS) using a pH meter. PO4 and F- UV-spectrophotometer, Na, K, and calcium (flame photo meter), NO3- NO3-N (Electronic method-horiba), and turbidity meter to evaluate the stream-water quality were used, and heavy metals, particularly Al, As, Cd, Fe, Cr, Cu, Zn, Pb, Ni, and Mn are analyzed as heavy metal pollutions. The phy-chem average values of pH, Temp, EC, Tds, Salinity, alkalinity, cod, bod, do, chloride, calcium, C. hardness, M. hardness, T. hardness, N-Nitrogen, Phosphate, Potassium, Sodium, Turbidity, Fluoride, Sulphate, and Sulphur are found 8.13, 27.57 °C, 218, 111.67, 78.67, 70.39, 2029, 5.70, 3.83, 70.83, 737, 62.30, 166.11, 679, 1132, 149, 11, 28.33, 4.44, 07, 178, 180 respectively. Heavy metal concentrations, including aluminum, arsenic, cadmium, iron, chromium, copper, zinc, lead, nickel, and manganese, are detected at 32, 7.2, 6.24, 96.4, 0.00, 0.00, 40, 0.00, 0.00, 30 μg/L, respectively. Concentrations of studied heavy metals, particularly, Mn, Ni, Cd, and Fe, have measurements that are greater than the permissible standard limits of BIS, WHO.

Bioremediation of Selected Heavy Metals from Industrial Influent Collected at Wupa Wastewater Treatment Plant, Abuja

One of the primary issues brought about by the industrialization's rapid development is aquatic pollution. Utilizing microorganisms to remediate industrial wastewater (IWW) is a sustainable approach. This study was conducted to assess pollution load in Wupa wastewater treatment plant and to use introduced microbes (Bacillus subtillis and Aspergillus niger) individually and in a consortium for bioremediation. The Wupa wastewater treatment plant in Abuja provided the wastewater samples, which were then analysed for heavy metal content and other physicochemical characteristics. Measurements were made of the pH, colour, temperature, turbidity, electrical conductivity (EC), total suspended solids (TSS), chemical oxygen demand (COD), biological oxygen demand (BOD), and total dissolved solids (TDS). Wastewaters samples were subjected to heavy metal analysis using Atomic absorption spectrometry (AAS). For eight days, a container experiment was conducted to assess the effectiveness of the chosen species. Selected species were used to remediate the wastewater samples both alone and collectively. Following treatment, turbidity (41.2%), BOD (95.2%), COD (96%), TSS (87-99%), TDS (27-8%), and EC (45-8%) all showed significant decreases. Following the experiment, atomic absorption spectrophotometry was used to determine the metal concentrations in water samples. 98.4% of Zn, 92.4% of Fe, and 92.4% of Mn were eliminated by the chosen species. Heavy metal removal percentage from Wupa wastewater using Aspergillus niger and Bacillus subtillis. Zinc significantly (p>0.05) record high removal efficiency as compared to Mangane and Iron in the waste water treated with Bacillus subtilis, A. Niger and the combination of both organisms.The bioremoval efficiency of Aspergillus niger and Bacillus subtillis for heavy metals in Wupa wastewater. The control treatment significantly (p<0.05) has lower bioremoval efficiency of the heavy metals (Manganese, Iron and Zinc) when compared to the waste water treated with Bacillus subtilis, A. Niger and the combination of both organisms. Based on the findings of this study, it can be concluded that the Bacillus subtillis and Aspergillus niger and other ingineous wastewater isolsates had the capacity to resist and grow on heavy metals and thus contributes in the removal of heavy metals present in the wastewater by absorbing them which also increased the biomass of the microbes.

ДИНАМИКА КОНЦЕНТРАЦИЙ РАСТВОРЕННЫХ ФОРМ ТЯЖЕЛЫХ МЕТАЛЛОВ В ВОДЕ РЕКИ МОСКВЫ ПО ДАННЫМ МОНИТОРИНГОВЫХ ИССЛЕДОВАНИЙ В 2021-2023 ГОДА

Background. The Moskva River is a prime example of a natural urban watercourse subjected to strong and varied anthropogenic pressure. For many years, this river has been characterized by increased content of heavy metals. The exceedance of the maximum allowable concentrations of harmful substances in the waters of water bodies used for fishery can result in disruption of the normal functioning of aquatic ecosystems. Relevance. The summarized data collected over the course of monitoring surveys of the Moskva River for three years will be indicative of the relative contribution of natural and anthropogenic sources into its pollution. The aim of this work is to identify the dynamics of spatial and temporal distribution of heavy metals in the Moskva River water and its relation to hydrological seasons, as well as to assess the anthropogenic pressure exerted by the city of Moscow on the river. Methods. Water samples were collected in 2021-2023 during four hydrological seasons. Identification of heavy metals in the collected samples has been carried out using the atomic absorption method. Results. The analysis of the content of dissolved heavy metals (iron, cadmium, cobalt, manganese, copper, nickel, lead, and chrome) in the Moskva River water in various seasons of 2021-2023 has been conducted, and the same was done for zinc in 2023. The dynamics of the spatial and temporal distribution of these heavy metals has been identified, as well as its dependence on the hydrological phases. The influence of the urban infrastructure on the composition of the Moskva River water has been elucidated. Within the investigated area, the exceedance of the values prescribed by the water quality standards for the water bodies used for fishery (MACfish) has been recorded. Conclusion. The waters of the Moskva River have been characterized as polluted, mainly with iron, manganese, copper, and zinc. For lead, chrome, cobalt, nickel, and cadmium, no exceedance of the MACfish has been recorded. It has been found that the majority of the investigated elements were exceeding the values prescribed by the established standards in the spring season, but their concentrations decreased in summer.

Assessment of the concentration of toxic metals (aluminum, cadmium and manganese) in the soil and evergreen plant species at the Sastavci surface mine and its vicinity

The study aims to determine the concentration of Al+3, Cd+2 and Mn+2 in the soil and parts of evergreen plant species - juniper and white pine - at the surface mine Sastavci (Badanj) and its vicinity in order to determine the possibility of using evergreen plants as an ecological indicator or for phytoremediation. Globally, as a result of various anthropogenic activities such as traffic, agricultural activities, waste incineration, industrial production, mining, etc., it represents a serious problem leading to pollution with toxic and potentially toxic metal cations. One of the more innovative techniques used for the remediation of mining areas is phytoremediation. By applying phytoremediation, certain plant species in polluted areas have the ability to act as accumulators or hyperaccumulators, absorbing toxic metals from the soil through the plant roots and transporting them to the upper parts. This research has been conducted to determine the concentration of Al+3, Cd+2 and Mn+2 at the surface mine itself and its surroundings, as well as to monitor the distribution of metal cations in the system of roots, branches, needles, and fruits of the evergreen plant species - white pine and juniper. The results showed that the sampled soil was contaminated with Cd in zones I and II for both plant species, since the concentrations exceeded the limit values, while the concentration of Cd in zone III as well as in the control zone was below the determination limits for both plant species. The concentration of Mn in the soil from the white pine and juniper zone was above the world average in all three zones, as well as in the control zone itself. The soil was most enriched with the analyzed elements in the surface mine of zone I and zone II. According to the analysis of elements in the parts of white pine, roots, branches, needles and fruits, the highest concentration of Al was detected in the root in zone I, while the lowest concentration was recorded in the fruit (cones) in the control zone, an increased concentration of Cd was recorded in the branches in zones I and II, and the highest concentration of Mn was recorded in needles in zone II. The highest Al concentration was recorded in the juniper root in zone I and the lowest in the juniper fruit in the control zone, the Cd concentration was the highest in the juniper root zone I, and the lowest in the juniper fruit and the highest Mn concentration was recorded in the juniper needles in zone I. Based on the obtained values of the coefficient of biological absorption, it can be concluded that white pine is not suitable for phytoextraction or phytostabilization of the tested elements. The analysis of biological factors (bioconcentration, translocation and bioaccumulation factor) indicated possible usage of juniper in phytoextraction only for Cd.

The content of heavy metals in the gray-brown soils of the karakul pasture Karnabchul in Samarkand, Uzbekistan

This article presents the results of X-ray fluorescence analysis (XFA) of gray-brown soils on the content of heavy metals nickel, antimony, copper, zinc, arsenic, lead, vannadium, chromium, manganese, iron, cobalt and aluminum of the karakul pasture Karnabchul. The dynamics of the distribution of heavy metals over the soil profile of graybrown soils is described in graphic images. The drawings depict the landscape of the karakul breeding pasture Karnabchul and the soil section of gray-brown soils.

Improving Acid Mine Drainage Treatment through Electrocoagulation: Effect of Time, Electrode Distance, and Electrode Types

This study explores the feasibility of employing electrocoagulation technology to manage Acid Mine Drainage (AMD) wastewater, focusing on reducing heavy metal concentrations, particularly iron (Fe) and manganese (Mn). Samples of AMD liquid waste from PT Lhoong Setia Mining in Aceh Province, Indonesia, underwent electrocoagulation using Al-Zn and Al-Fe electrodes with Direct Current (DC). The investigation considered various parameters, including contact time (ranging from 0 to 45 minutes), electrode distance (2, 2.5, and 3 cm), and electrode type (Al-Fe and Al-Zn). The study revealed that prolonged electrocoagulation increased the reduction of Fe and Mn metals due to enhanced Al(OH)3 formation. While Al-Zn electrodes exhibited rapid coagulant formation initially, Al-Fe electrodes sustained effectiveness throughout the process. Optimal reduction of Fe and Mn concentrations occurred at different electrode distances, emphasizing the critical role of spacing in electrocoagulation efficiency. Furthermore, the electrocoagulation process successfully elevated pH levels within acceptable limits and effectively reduced Total Suspended Solids (TSS) in AMD waste, aligning with regulatory standards. This research underscores the potential for electrocoagulation as a viable technology for mitigating the environmental impact of AMD and addresses knowledge gaps related to efficient pollutant removal in mining wastewater treatment. Future studies should explore parameter optimization and consider transitioning to continuous operation for increased effectiveness, particularly in remote mining locations.

Using structural equation modeling to assess the genotoxic and mutagenic effects of heavy metal contamination in the freshwater ecosystems: A study involving Oreochromis niloticus in an urban river

Chemical pollutants represent a leading problem for aquatic ecosystems, as they can induce genetic, biochemical, and physiological changes in the species of these ecosystems, thus compromising their adaptability and survival. The Capibaribe River runs through the state of Pernambuco, located in Northeastern Brazil, and passes through areas of agricultural cultivation, densely populated cities, and industrial centers, primarily textiles. Despite its importance, few ecotoxicological studies have been conducted on its environment, and knowledge about pollution patterns and their effects on its biota is still being determined. The objective of this study was to evaluate the water quality and the damage supposed to be caused by pollutants on the DNA specimens of Nile tilapia (Oreochromis niloticus) obtained from seven strategic points of Capibaribe. Tilapia specimens and water were collected during the rainy and dry seasons from 2015 to 2017. The following characteristics were analyzed: physicochemical (six), metal concentration (seven), local pluviosity, micronuclei, and comet assay. The physicochemical and heavy metal analyses were exploratory, whereas the ecotoxicological analyses were hypothetical. To verify this hypothesis, we compared the groups of fish collected to the results of the micronuclei test and comet assay. We created a Structural Equation Model (SEM) to determine how each metal's micronuclei variables, damage index, pluviosity, and concentration were related. Our results demonstrated that the highest values for markers of genetic damage were detected at points with the highest heavy metal concentrations, especially iron, zinc, manganese, chromium, and cadmium. The SEM demonstrated that metals could explain the findings of the genotoxicity markers. Moreover, other pollutants, such as pesticides, should be considered, mainly where the river passes through rural areas. The results presented here demonstrate that the Capibaribe River has different degrees of contamination and confirm our hypothesis.

Ecological and Health Risk Assessment of Heavy Metals Bioaccumulation in Ganges Fish Near Varanasi, India.

Heavy metal contamination in river Ganga is one of the factors for deterioration in its water quality and also adds to human health risks. We designed our study to achieve a holistic approach by not only estimating the concentration of heavy metals (lead, manganese, chromium, and cadmium) in the river water at different sites based on human anthropogenic activities but also in the fishes residing in the same sites that are collected for human consumption on daily basis. We found that Ganga River in Varanasi is highly loaded with metals (PLI = 6.698). Mean concentration in water was 1.29mg/L for Pb, 1.325mg/L for Mn, 0.169mg/L for Cr, and 0.161mg/L for Cd, which were above the permissible limits stated by Environment Protection Agency (EPA) in drinking water. Fish, including exotic and invasive species, were collected from the wild and were processed for the presence of these metals in their tissues. Degree of heavy metal concentration followed liver > gills > muscles. The highest accumulation of Pb was observed in Carpio (Cyprinus carpio) liver (8.86µg/g) and lowest in Baikari (Clupisoma garua) muscles (0.07µg/g). Total target hazard quotient (THQ) value, i.e., hazard index (HI) showed values in following sequence: Cyprinus carpio > Oreochromis niloticus > Channa gachua > Johnius coitor > Mastacembelus armatus > Mystus tengara > Clupisoma garua. Maximum HI value was recorded in C. carpio, which is highly consumed fish by humans, hence, may be harmful to them.

Optimizing phosphate removal by manipulating manganese and cobalt levels in soil aquifer treatment system

Manganese (Mn2+) and cobalt (Co2+) metals have been reported to exhibit complex interactions with phosphate (PO43-) ions, which can influence their mobility, reactivity, and removal behavior in soil aquifer treatment system (SAT). This study aimed to investigate the role of manganese (Mn2+) and cobalt (Co2+) in phosphate (PO43-) removal within a soil aquifer treatment system. A lab-scale column experiment was conducted using sand as the filtration media, and a synthetic wastewater containing 20 mg/L PO43-, 60 mg/L Mn2+, and 40 mg/L Co2+ was used. The breakthrough curves showed efficient removal of PO43- during the infiltration process, with concentrations reaching as low as 1 mg/L. The regression analysis revealed that Mn2+ had a strong negative correlation effect on PO43- concentration, indicating its stimulatory role in PO43- removal. Conversely, Co2+ showed a strong positive correlation effect, suggesting its promoting effect on PO43- concentration. Optimization analysis identified optimal concentrations of 57.4 mg/L for Mn2+ and 4.8 mg/L for Co2+ that interacted with lower PO43- concentrations, achieving the desired outcome of reducing PO43- levels. These findings highlight the importance of considering Mn2+ and Co2+ concentrations in soil aquifer treatment systems for effective phosphate removal.

Formation of silyl metal hydride, HMnSiH3 and silylidyne, H3ReSiH in the activation of silane by manganese and rhenium atoms

The reactions of laser ablated manganese and rhenium metal atoms with silane molecules in low temperature argon matrix were studied. The experimental and theoretical results indicate that the reaction happened after the metal atoms were excited to Mn(6P) or Re(6P) excited states upon photolysis. Combining the isotopic shifts of the infrared absorptions and quantum chemical calculations, the silyl metal hydride HMnSiH3 and the silylidyne H3ReSiH were identified in the argon matrix. The vibronic coupling between the ground state X2A' and the first excited state A2A'' leads to a bond angle H-Si-Re of 130.4° in the doublet ground state H3ReSiH.

Exploring the association between two groups of metals with potentially opposing renal effects and renal function in middle-aged and older adults: Evidence from an explainable machine learning method

BackgroundMachine learning models have promising applications in capturing the complex relationship between mixtures of exposures and outcomes. ObjectiveOur study aimed at introducing an explainable machine learning (EML) model to assess the association between metal mixtures with potentially opposing renal effects and renal function in middle-aged and older adults. MethodsThis study extracted data from two cycle years of the National Health and Nutrition Examination Survey (NHANES). Participants aged 45 years or older with complete data on six metals (lead, cadmium, manganese, mercury, and selenium) and related covariates were enrolled. The EML model was developed by the optimized machine learning model together with Shapley Additive exPlanations (SHAP) to assess the chronic kidney disease (CKD) risk with metal mixtures. The results from EML were further compared in detail with multiple logistic regression (MLR) and Bayesian kernel machine regression (BKMR). ResultsAfter adjusting for included covariates, MLR pointed out the lead and arsenic were generally positively associated with CKD, but manganese had a negative association. In the BKMR analysis, each metal was found to have a non-linear association with the risk of CKD, and interactions can exist between metals, especially for arsenic and lead. The EML ranked the feature importance: lead, manganese, arsenic and selenium were close behind in importance after gender, age or BMI for participants with CKD. Strong interactions between mercury and lead, manganese and cadmium and arsenic and manganese were identified by partial dependence plot (PDP) of SHAP and bivariate exposure-response effect plots of BKMR. The EML model determined the “trigger point” at which the risk of CKD abruptly changed. ConclusionCo-exposure to metals with different nephrotoxicity could have different joint association with renal function, and EML can be a powerful method for studying complex exposure mixtures.

The crucial role of ligand deprotonation in manganese catalyzed hydrogenation reactions

Hydrogenation catalysts based on the abundant early transition metal manganese recently received growing attention. A common motif found in most of the reported systems is a deprotonatable hydrogen atom in the ligand, usually considered necessary within an outer-sphere mechanism. Here we investigated the mechanism of the catalytic hydrogenation of ketones, focusing on the crucial function of the deprotonatable H atom in the ligand. Therefore, we synthesized phosphine-free Mn(I) complexes of the type [(L)MnBr(CO)3)] utilizing pyridyl-imidazole ligands, having a deprotonatable H atom within the imidazole ring. They were found to be active catalysts for the hydrogenation of ketones with molecular hydrogen. Kinetic and spectroscopic studies together with DFT calculations point towards an inner-sphere mechanism with the hydride transfer to the substrate being the rate determining step. Most importantly, we demonstrate that the NH-motif remains deprotonated throughout the catalytic cycle maintaining an anionic manganese species. Thereby, the anionic ligand is a more potent electron donor which enhances the rate determining hydride transfer.

Development of the supercapacitor efficiency of the two-dimensional graphene oxide decorated by nano magnetite through building novel nanocomposites using nanoparticles of cobalt, manganese, vanadium, and zirconium oxides

The targeting of the current work is enhancing the supercapacitor efficiency of the magnetite nanocomposite with graphene oxide (GO) nanostructure via the addition of metal oxide nanoparticles (NPs) such as cobalt, manganese, vanadium, and zirconium for building a novel nano combination. The sol/gel method is utilized to fabricate the nanocomposites, and the potentiostat device measures the electrochemical performances. The supercapacitors of the magnetite (Fe3O4) NPs that decorate the graphene oxide (GO) surface and the modified electrode building have been examined by different tests for supercapacitor applications, and are studied via the impedance spectroscopy (EIS) data that confirm the building progress of the electron transfer and surface structure that enable it to be a favorable candidate for supercapacitors applications. The areal capacitance (Carea) of NCPs was measured and presented at 622.65 mFcm−2 (GO@Fe3O4), 62.428 mFcm−2 (GO@ Fe3O4.Co3O4), 388.4 mFcm−2 (GO@ Fe3O4.Mn3O4), 851.1 mFcm−2 (GO@Fe3O4.V4O7), 966.4 mFcm−2 (GO@Fe3O4.ZrO2). The NCPs have capacitance values related to CPE (C = 9.404 nF/cm2), GO@Fe3O4 (C = 40.886 nF/cm2), GO@Fe3O4.Co3O4 (C = 13.17 nF/cm2), GO@Fe3O4.Mn3O4 (C = 17.56 nF/cm2), GO@Fe3O4.V4O7 (C = 126.9 nF/cm2), and GO@Fe3O4.ZrO2 (C = 183.6 nF/cm2). By adding cobalt, manganese, vanadium, and zirconium metal oxide NPs, the new building electrodes have capacitance at 13.17, 17.56, 183.6, and 126.9 nF/cm2, respectively. The capacitance retention finished at 100 cycles is recorded and exhibited good cycle stability. From the results, the fabricated NCPS electrodes are a promising candidate for supercapacitor manufacturing applications and other applications such as water treatment.

Exploration of the effects of electrolytic manganese residue on the environmental, economic, and engineering performance of magnesium oxychloride cement: A possible utilization method of electrolytic manganese residue

The widespread use of magnesium oxychloride cement (MOC) can effectively solve the waste problem in the potash industry. However, its poor water resistance limits its practical application. Electrolytic Manganese Residue (EMR), as a solid waste from manganese metal smelting, requires an effective utilization method. In this work, we have attempted to incorporate EMR into MOC after its treatment in order to improve the water resistance of MOC and increase the utilization rate of EMR. The addition of EMR to MOC increased the density of MOC. The incorporation of EMR did not significantly reduce the strength of the MOC samples. The incorporation of EMR reduced the relative content of magnesium oxide in the specimens and EMR can be used as a source of soluble Al, Si and Fe to produce insoluble amorphous gels. The combined effect resulted in an effective improvement in the water resistance of the samples. The 28-day water immersion strength of the EMR100 can reach 38.3 MPa, and its water resistance coefficient was 82.10%. The appropriate doping of EMR can improve the pore structure of the specimens, reduce the porosity and refine the pore size distribution. Carbon emission per unit compressive strength and cost per unit compressive strength were used as evaluation indices of environmental and economic benefits. A high dosage of EMR-incorporated MOC resulted in low cost and carbon emission, especially the strength of the specimen after water immersion as a strength index. Taking into account the strength after 14 days of air curing and 28 days of water immersion, the advantages of cost per unit compressive strength and carbon emission per unit compressive strength of EMR100 were further extended and reduced by 86.23% and 22.15% respectively compared to the benchmark group. The heavy metal curing of EMR was evaluated by ion leaching test, and the result showed that MOC effectively cured the heavy metal ions in EMR and reduced the environmental risk of EMR. The good performance of EMR in MOC systems not only provides an effective breakthrough for the efficient utilization of EMR and its heavy metal curing, but also effectively improves the performance of MOC and reduces the production cost.

Theoretical Study on the Mechanism of the Hydrogenation of Azo (N═N) Bonds to Amines Catalyzed by Manganese.

The mechanism of the transition metal manganese complex Mn(PhPNN)(CO)2Br (CA-4) that catalyzed the hydrogenation of the azo (N═N) bond to amines has been investigated using the PBE0 function. The results show that the whole reaction involves three basic processes: (1) the addition of H2 to CA gives IN2, which can hydrogenate the azo (N═N) bond at the later stage; (2) hydrogenation of azobenzene by IN2, which gives 1,2-diphenylhydrazine (PhNHNHPh); and (3) hydrogenation of 1,2-diphenylhydrazine by IN2, which affords aniline (PhNH2). The results suggest that the hydrogenation of CA and hydrogenation of azobenzene by IN2 to afford PhNHNHPh are easy to occur due to the low barriers, and the overall rate-determining step is the formation of IN11 and PhNH2 by breaking the N-N bond in the stage of hydrogenation of 1,2-diphenylhydrazine by IN2, with an energy barrier of 39.1 kcal/mol. The computed results are in good agreement with the experimental results. The mechanism of the azobenzene reaction catalyzed by manganese was analyzed by charge and orbital analysis in detail. The theoretical results provide a deeper understanding of the mechanism and fully explain the experimental facts.

Heavy Metal Concentration of Okra (Abelmoschus Esculentus) Grown on Dumpsite Soil in Benin City, Nigeria

The study investigates the concentrations of heavy metals in Okra (Abelmoschus esculentus) planted in dumpsite soil obtained from the University of Benin and Ekosodin in Benin City. Soil samples were collected before and after planting and analyzed for pH, total nitrogen (N), total organic carbon (C), phosphorus (P), iron (Fe), zinc (Zn), manganese (Mn), and heavy metal concentrations (Cu, Pb, Cd, and Cr). The study reveals variations in soil acidity levels across different locations before and after planting. In Table 1, soil pH was moderately acidic in Farmland (5.61), neutral in Market (6.79) and Residential (6.76) areas, and slightly acidic in Faculties (6.14). In Table 2, after planting, the pH remained moderately acidic in Market (5.68) and Residential (5.80), while becoming strongly acidic in Farmland (5.42) and Faculties (5.36). Total N and P decreased in most dumpsites after planting, while total organic carbon increased. Fe, Zn, and Mn concentration varied between dumpsites and after planting stages. Particle size distribution remained predominantly sandy across dumpsites and planting stages. The study suggests that Okra plants cultivated in various dumpsite soils showed no toxic levels for the selected heavy metals, with concentrations generally falling within acceptable limits for vegetable consumption. The copper concentration highest uptake observed in Okra plants from Residential Land (36.0 mg/kg) and the lowest in Farmland (23.3 mg/kg). Lead (Pb) uptake varied across dumpsites: Market (0.15 mg/kg), Farmland (0.10 mg/kg), Residential Land (0.12 mg/kg), and Faculties (0.06 mg/kg). Cadmium (Cd) uptake was observed at Market dumpsites (0.05 mg/kg), Farmland (0.02 mg/kg), Residential Area (0.01 mg/kg), and Faculties (0.04 mg/kg). Heavy metal concentrations in the soil and Okra plants were generally below the permissible limits set by the Department of Petroleum Resources (DPR) for soil and World Health Organization (WHO) for vegetables intended for human consumption.

A statistical method for source approtionment of soil pollution

The present study was conducted to evaluate the source apportionment of soil pollution and its impact on soil quality using multivariate statistical analysis tools. Multivariable statistical techniques such as cluster analysis (CA), principal component analysis (PCA), factor analysis (FA) and correlation offers superior interpretation of complicated data sets to better understand the soil quality. Soil samples were analyzed for physicochemical parameters (pH, temperature, electrical conductivity, organic carbon, moisture content, phosphate, potassium and sulphar) and for some important heavy metals (zinc, iron, manganese and copper). Sampling stations have been classified into three groups using Cluster Analysis (CA) in a convincing way. Results revealed that among all the sampling stations, three significantly different groups: (1) stations having highest pollution sources (HW and MW), (2) Moderate polluted area (SW and IW) & (3) control site (VW) of the study stretch. The PCA generated 2 significant factors having eigenvalues >1 which explain 82.78% of the variance in the dataset. Each soil quality parameter with strong correlation coefficient value was considered to be significant (p<0.01). Therefore, the present study revealed that mining activities, dumping of municipal sewage, disposal of biomedical waste and industrial effluent including solid waste (e.g fly ash) have greater influence on the soil quality. Results also showed that the concentrations of heavy metals (Cu, Mn and Zn) in highly polluted soil are beyond the permissible limit. The pollutant levels were significantly different in the three groups of soil pollution character samples, which were confirmed by ANOVA analysis.

Isolation and identification of bacteria from solid waste deposit sites for the degradation of heavy metals

Heavy metals from solid waste deposits that are toxic, mutagenic, and carcinogenic contaminate natural water supplies and agricultural environments. The purpose of this project is to separate and characterize naturally occurring bacteria that can reduce and detoxify heavy metals (lead, cadmium, nickel, zinc, manganese, iron, copper, chromium, and mercury) from solid waste dumping sites. Ten strains in total were isolated from the samples; the two best-performing isolates, Shewanella oneidensis strain AGB 4 (Isolate 5) and Bacillus pumilus strain AGB 11 (Isolate 6) were recognized up to the genus level based on their 16S rRNA identification studies. These isolates demonstrated resistance to every heavy metal that was examined in the solid waste. The MICs for the two isolates varied in relation to the amounts of the heavy metals listed above. The solid waste isolates grew best at pH 7.0, 30°C and an incubation period of 24 hours. Utilizing an atomic absorption spectrophotometer to measure degradation potential, Shewanella oneidensis demonstrated the most removable capability for copper (60%) and the lowest removable capability for lead, arsenic and mercury (45%) and Bacillus pumilus demonstrated a reduction of 48% in mercury and arsenic and 65% in copper. Bacillus pumilus and Shewanella oneidensis may be able to break down heavy metals through plasmids, which could be used to change plasmids so they can carry the ability to accumulate heavy metals. Thus, determining the resistance to heavy metals and biodegradation potential of two bacteria could serve as a foundational investigation for the development of viable local biological remediation agents in solid waste deposit sites.

Nickel‐Catalyzed Asymmetric Propargyl‐Aryl Cross‐Electrophile Coupling

AbstractPerforming asymmetric cross‐coupling reactions between propargylic electrophiles and aryl nucleophiles is a well‐established method to build enantioenriched benzylic alkynes. Here, a catalytic enantioselective propargyl‐aryl cross‐coupling between two electrophiles was achieved for the first time in a stereoconvergent manner. Propargylic chlorides were treated with aryl iodides as well as heteroaryl iodides in the presence of a chiral nickel complex, and manganese metal was used as a stoichiometric reductant, allowing for the construction of a propargyl C‐aryl bond under mild conditions. An alternative dual nickel/photoredox catalytic protocol was also developed for this cross‐electrophile coupling in the absence of a metal reductant. The potential utility of this conversion is demonstrated in the facile construction of stereoenriched bioactive molecule derivatives and medicinal compounds based on the diversity of acetylenic chemistry. Detailed experimental studies have revealed the key mechanistic features of this transformation.