Fe Values Research Articles

Dry matter yield, mineral contents and proximate composition of Panicum maximum (Jacq var. Ntchisi) sown with forage legumes

This study assessed the dry matter yield, mineral and proximate composition of Panicum maximum Jacq var. Ntchisi planted with Lablab purpureus (Lablab), Centrosema pubescens (Centro), Aeschynomene histrix (A. histrix) and Stylosanthes guianensis (Stylo) in a 3 x 5 factorial experiment using Randomized Complete Block Design in early, mid and late rainy season. The dry matter yields (DMY) of panicum sown with Lablab (11.82 t/ha/yr) was significantly higher (P<0.05) than that observed for other mixtures. The least DMY of 9.46 t/ha/yr was observed for panicum in panicum/ A. histrix mixture. The yields recorded for Stylo and Lablab were highest in mid and late rainy seasons than in the early rain. Panicum sown with Lablab had the highest DM (37.71g/100g DM), Crude protein (CP) (11.36g/100g DM), ether extracts (7.20g/100g DM) and ash content (2.52g/100g DM). Among the legumes, Lablab had the highest CP (23.29 g/100g DM), crude fibre (10.61 g/100g DM) and ash content (3.96 g/100g DM). However, Centro was highest in ether extract (9.30g/100g DM). Panicum sown with Lablab had higher concentration of sodium (Na) and iron (Fe) while panicum planted with Stylo had highest concentration of phosphorus (P). The concentration of calcium (Ca) was similar (P>0.05) among the mixtures but differed (P<0.05) in the legumes. Stylo had the highest Ca concentration (0.72%) whereas highest P and Fe values were observed in Lablab. In conclusion, panicum harvested from panicum/lablab mixture had the highest DMY, CP, EE and ash content of grass in early, mid and late rainy season than the other mixtures. 

Investigation of mechanical and thermal activation on metal extraction from red mud

Red mud is an inevitable and under-utilized byproduct of the aluminium industry. The current study evaluates the effect of mechanical and thermal activation on the acid leaching of red mud. The acid leaching of the pretreated product is followed by acid-base treatment to precipitate the dissolved aluminium values from solution and enrich the residue with Fe and Ti values. Mild acid leaching yielded ~76% aluminium dissolution with 81% silicon removal. The direct acid leaching resulted in dissociation of sodium aluminosilicate; meanwhile, gibbsite phase remains in the residue. The mechanical milling for 1 h enhanced the aluminium dissolution to 89.5% with silicon and iron dissolution of 98.5 and 9.6%, respectively. The silica and iron oxide values were separated before HCl leaching by thermal pretreatment step using microwave heating with NaOH and carbon additives respectively. The sodium silicate and sodium aluminate phases formed during alkali thermal treatment resulted in ~33% silicon and ~ 27% aluminium removal by water washing. Meanwhile, HCl leaching of the water wash residue resulted in 82% aluminium dissolution with 70% recovery and residue containing ~52% Fe2O3, and 28% TiO2 is obtained. The carbothermal reduction yielded iron-rich magnetic concentrate having 48% iron grade with 20% metallic iron, and ~ 83% iron recovery. Leaching of the non-magnetic fraction containing hercynite and fayalite as the major aluminium and silicon bearing phases resulted in 81% aluminium dissolution with overall aluminium recovery of only 37%. Mullite formation is also observed in the precipitate with a high Al/Si molar ratio. The carbothermal route was found as an energy-efficient route, whereas the mechanical milling route yielded maximum Al extraction of ~90% with Fe and Ti content of 41.1% and 16.8% in the residue.

Efficient Electrocatalytic CO2 Reduction to C2+ Alcohols at Defect-Site-Rich Cu Surface

Summary Electrochemical CO2 reduction is a promising approach for upgrading excessive CO2 into value-added chemicals, while the exquisite control of the catalyst atomic structures to obtain high C2+ alcohol selectivity has remained challenging due to the intrinsically favored ethylene pathways at Cu surface. Herein, we demonstrate a rational strategy to achieve ∼70% faradaic efficiency toward C2+ alcohols. We utilized a CO-rich environment to construct Cu catalysts with stepped sites that enabled high surface coverages of ∗CO intermediates and the bridge-bound ∗CO adsorption, which allowed to trigger CO2 reduction pathways toward the formation alcohols. Using this defect-site-rich Cu catalyst, we achieved C2+ alcohols with partial current densities of > 100 mA·cm−2 in both a flow-cell electrolyzer and a membrane electrode assembly (MEA) electrolyzer. A stable alcohol faradaic efficiency of ∼60% was also obtained, with ∼500 mg C2+ alcohol production per cm2 catalyst during a continuous 30-h operation.

A comparison of the physicochemical properties of chestnut and highland honey: The case of Senoz Valley in the Rize province of Turkey

The aim of this study was to determine the physicochemical parameter changes, aroma, melissopalynological properties, and heavy metal content of honey produced from different types of flora (chestnut and highland) in the Senoz Valley. For this purpose, the distribution of beehives at different elevation levels in the research area was determined by a layered random sampling method. Some characteristics of the honey samples were analyzed by standard laboratory methods. The highest average color (L and b) and the glucose, sucrose, Brix, Cd, Pb, Ni, Zn, and Cr values were found in the highland honeys; the highest color (a) and fructose, F/G ratio, proline, pH, conductivity, Fe, Cu, Al, and Mn values were found in the chestnut honeys. The difference between highland and chestnut honeys was statistically significant in terms of color (L and a), F/G ratio, proline, pH, electrical conductivity, Pb, Cu, and Mn. A total of 146 aromatic components were isolated in the chestnut and highland honeys.

PENGARUH PENAMBANGAN MANGAN TERHADAP KUALITAS AIR SUMUR DI DESA SUPUL, KECAMATAN KUATNANA, KABUPATEN TIMOR TENGAH SELATAN

The aim of this study is to determine the effect of Manganese (Mn) mine in Supul village on the water quality of the residents' dug wells. Research method is used purposive sampling. Water sampling is required for chemical and biological analysis in the laboratory to determine the content of Fe, Mn, E. coli bacteria and pH level in the water. The results showed that the terms of threshold levels of Fe, Mn, and pH values, well water in Hamlet C (Oefenu) which is 200 to 300 meters away that is more polluted than others because those parameters are over the average threshold that required by the Ministry of Health on drinking and cleaning water quality standards. This condition is caused by very close to the mine site and the tailing Manganese. Keywords: Manganese mine, Well water quality, Supul Village

Pedogenesis and spatial distribution of soil magnetic properties along a lithotoposequence in an arid region of Southern Iran

Magnetic susceptibility (χ) measurements are widely used to study soil-forming processes. This study was conducted to determine the role of lithology, geomorphology, and soil processes in soil magnetic properties in an arid region of Southern Iran. For this purpose, ten representative pedons (in 3 zones, based on lithology) on different geomorphic positions, were studied. In addition, 82 topsoil samples were collected to investigate spatial distribution maps using GIS software. The χlf range of soils was from 74 to 1495 × 10−8 m3 kg−1. The average amounts of χlf in the soils of the three zones were 1082, 245, and 153 × 10−8 m3 kg−1, respectively. While the highest value of χlf of the soils of zone 1 (with metamorphic parent material), was observed at the bottom-profile, the highest value of χlf of the other zones (with fine-grained evaporates and coarse-grained sandstone parent materials, respectively) was observed at the profile-top. Spatial distribution of χlf and total Fe values exhibited the highest amount in the soils of zone 1, which were attributed to adjacent iron-rich metamorphic formations. Higher values of χfd were observed in the soils of zones 2 and 3, suggesting a higher proportion of pedogenic ultrafine grains. The maximum value of pedogenic susceptibility (χp) was observed in the soils of zones 2 and 3, indicating higher proportions of pedogenic secondary iron oxides; however, the negative value of χp in the soils of zone 1, support this hypothesis that most of the χlf signal is carried by bedrock magnetic minerals.

Magnetic Signature of Serpentinization at Zedang in the South Tibetan Ophiolite Belt

AbstractMagnetic signature of serpentinized mantle peridotite has crucial importance in understanding the serpentinization process and interpreting the origin of strong magnetization anomalies at ultramafic‐hosted hydrothermal settings. However, different groups of serpentinized peridotites from both ocean drillings and ophiolite complexes have shown considerable variations in the abundance of magnetite (Oufi et al., 2002; Bonnemains et al., 2016; Li et al., 2017). We examined the magnetic properties, petrography and mineral chemistry of variably serpentinized peridotites from Zedang ophiolite in the eastern Yarlung‐Zangbo suture in south Tibet to evaluate the conditions of serpentinization and magnetite formation as well as magnetic sources in suture zones.The studied samples were 0–90% serpentinized with densities from 3.316 to 2.593 g cm–3 and show typical mesh textures of olivine replaced by serpentine on thin sections of core specimen. Serpentines were divided into type‐1 Fe‐poor serpentine mesh (1.84–2.88 wt% FeO) associated with magnetite in the early stage and type‐2 Fe‐rich serpentine cores (3.92–5.12 wt% FeO) with no formation of magnetite in the late serpentinization. Brucite vein appeared in central serpentine veins and show Mg/(Mg+Fe) values of 0.74–0.87 at ∼50–70% of serpentinization. Pure magnetite was identified as the main magnetic carrier by thermomagnetic analyses, but minor Cr‐magnetite (∼0.8 mole fractions of Fe3O4) was also detected due to oxidation of early spinel.All the peridotite samples show a rapid increase of magnetic susceptibility from ∼0.001 to ∼0.03 SI before 40–50% of serpentinization and a following flat trend in values 0.02–0.03 SI at > 50% of serpentinization. This density–susceptibility relationship differs from the rapid production of magnetite above 60–70% of serpentinization for many abyssal peridotites (Oufi et al., 2002; Bach et al., 2006) and suggests that magnetite formation was coupled with hydration of olivine in the early serpentinization but the two decoupled at ∼ 40–50% of serpentinization. This transition is consistent with the petrographic observation that magnetite‐free serpentinization was developed in higher degrees (> 50%) of serpentinization.Prior studies suggested that serpentinization of < 200°C would generate Fe‐rich brucite, serpentine and little magnetite, whereas magnetite‐rich serpentinization was associated with Fe‐poor brucite and occurred at higher temperatures of 200–300°C (Klein et al., 2014). The petromagnetic features of serpentinized peridotites from the Zedang ophiolite indicate that the serpentinization process took place initially above 250°C (estimate from brucite composition) and continued to lower temperatures of < 200°C, probably during the mantle lithosphere cooling down in forearc settings (Xiong et al., 2017). These serpentinized peridotites have higher magnetization intensities (average 2.26 Am–1) than mafic dolerite dykes and basaltic volcanic rocks (mostly < 1 Am–1) and should be significant sources of aeromagnetic highs in the Yarlung‐Zangbo suture.

Three-dimensional weights of evidence modelling of a deep-seated porphyry Cu deposit

Given the challenges in data acquisition and spatial modelling at the detailed exploration stage, it is difficult to develop a prospectivity model, particularly for disseminated ore deposits. Recently, the weights of evidence (WofE) method has demonstrated a high efficiency for modelling such deposits. In this study, we propose a framework for creating a three-dimensional (3D) WofE-based prospectivity model of the Nochoun porphyry Cu deposit in SE Iran. The input data include qualitative geological and quantitative geochemical information obtained from boreholes and field observations. We combine ordinary and fuzzy weights of evidence for integrating qualitative and quantitative exploration criteria in a 3D space constrained by a metallogenic model of the study area for identifying a deep-seated ore body. Ordinary weights of evidence are determined for geological data, including lithology, alteration, rock type and structure. Moreover, we determine the fuzzy weight of evidence for each class of the continuous geochemical models created based on the factors analysis of Fe, Mo and Zn concentration values derived from boreholes. We integrate the input evidential models using WofE and create the posterior probability model. We also determine anomalous voxels in the probability model using a concentration–volume fractal model and validate them using a prediction–volume plot and test boreholes. The modelling results indicate the efficiency of the posterior probability model in identifying the anomalous voxels representing copper mineralized rock volumes. We provide open source software for the proposed framework which can be used for exploring deep-seated ore bodies in other regions. Supplementary data : Python scripts for implementing the proposed framework and supplementary files including more details on the evidential models are available at https://github.com/intelligent-exploration/3D_WofE .

LET-Dependent Intertrack Yields in Proton Irradiation at Ultra-High Dose Rates Relevant for FLASH Therapy.

FLASH radiotherapy delivers a high dose (≥10 Gy) at a high rate (≥40 Gy/s). In this way, particles are delivered in pulses as short as a few nanoseconds. At that rate, intertrack reactions between chemical species produced within the same pulse may affect the heterogeneous chemistry stage of water radiolysis. This stochastic process suits the capabilities of the Monte Carlo method, which can model intertrack effects to aid in radiobiology research, including the design and interpretation of experiments. In this work, the TOPAS-nBio Monte Carlo track-structure code was expanded to allow simulations of intertrack effects in the chemical stage of water radiolysis. Simulation of the behavior of radiolytic yields over a long period of time (up to 50 s) was verified by simulating radiolysis in a Fricke dosimeter irradiated by 60Co γ rays. In addition, LET-dependent G values of protons delivered in single squared pulses of widths, 1 ns, 1 µs and 10 µs, were obtained and compared to simulations using no intertrack considerations. The Fricke simulation for the calculated G value of Fe3+ ion at 50 s was within 0.4% of the accepted value from ICRU Report 34. For LET-dependent G values at the end of the chemical stage, intertrack effects were significant at LET values below 2 keV/µm. Above 2 keV/µm the reaction kinetics remained limited locally within each track and thus, effects of intertrack reactions remained low. Therefore, when track structure simulations are used to investigate the biological damage of FLASH irradiation, these intertrack reactions should be considered. The TOPAS-nBio framework with the expansion to intertrack chemistry simulation provides a useful tool to assist in this task.

Eigen vector based analysis of Landsat OLI principal components and constrained energy minimization maps for discriminating iron enriched zones in banded iron formation (BIF) in Sidhi, Madhya Pradesh

In this study, we have used visible near infrared (VNIR) and shortwave infrared (SWIR) spectral bands of the Operational Land Imager (OLI) sensor of Landsat 8 satellite to delineate promising areas for iron exploration in the parts of Madhya Pradesh, India. OLI bands resampled laboratory reflectance spectra of Banded Iron Formation (BIF) were used as the reference to identify OLI spectral bands suitable in recording spectral features of Iron bearing minerals. Subsequently, BIFs were delineated in the principal component (PC) image prepared using those PC bands; which had opposite Eigen vector loading for the spectral bands; which recorded absorption minima and shoulder of the spectral feature of iron. Within the BIF, iron enriched zones were identified by integrating constrained energy minimization (CEM) maps of BIF, hematite and limonite-goethite. Integrated CEM map delineating iron enrichment zones was validated in the field based on measured Fe values of samples using X-ray Fluorescence Instrument.

Avaliação ambiental da qualidade limnologica e de sedimentos em córrego do Centro Oeste do Brasil

O estudo teve como objetivo avaliar qualidade limnologica no córrego Curral de Arame, determinar concentrações de metais na água e nos sedimentos, avaliar se os tipos de uso e cobertura do solo interfere na qualidade aquática. Além de correlacionar o uso e a cobertura do solo em relação as concentrações de metais na água entre os períodos seco e chuvoso e investigar os potenciais riscos não-carcinogênicos de metais na água para a biota aquática. Os valores do pH, no período seco foram inferiores ao limite estabelecido pela legislação brasileira na porção média e baixa do córrego. O Fe na água ultrapassou o limite estabelecido pela resolução brasileira, nos quatro locais. As concentrações de metais nos sedimentos estavam dentro dos limites seguro para a vida aquática. O córrego Curral de Arame apresentou a vegetação ciliar reduzida em alguns locais, decorrente da expansão de atividades agrícolas. Constatamos, nos períodos seco e chuvoso, correlação negativa entre as proporções de agricultura e fragmentos florestais, mostrando quando há aumento de áreas agricultáveis ocorre o inverso a redução da cobertura vegetal nativa. No período chuvoso, houve correlação negativa e significativa, entre os fragmentos florestais em comparação ao Fe na água no córrego Curral de Arame, demostrando quando há maiores aporte de vegetação reduz o carreamento de contaminantes no curso do sistema aquático. No córrego Curral de Arame, nos períodos seco e chuvoso, apresentou risco não-carcinogênica na água para a biota aquática em relação aos valores de Fe. Neste sentido, o córrego Curral de Arame está passando por algum tipo de estresse ambiental, principalmente devido a redução da cobertura vegetação nativa no entono deste ambiente aquático.

Was the Tynong Batholith, Lachlan Orogen, Australia, extremely hot? Application of pseudosection modelling and TitaniQ geothermometry

Tonalites to granites of the Tynong Batholith, Lachlan Orogen, southeastern Australia contain primary clino- and orthopyroxenes as well as in enclaves and have produced very broad (2-10 km) contact aureoles that contain an anatectic zone within metagreywackes. The very broad contact aureoles can be related with the 3-D shape of the pluton and the Cpx and Opx we assume as remnants of higher temperature crystallization that were preserved due to water loss or low water content in the magma. Estimates of P and T based on x(Fe) values for coexisting cordierite and biotite in P-T pseudosections for a typical migmatitic hornfels, providing minimum temperature of pluton emplacement, indicate emplacement of the Toorongo tonalite at 4-10 km (1-3 kbar) and 680-750oC. However, the isopleths of An content of plagioclase indicates depths of up to 14 km at 660-740oC. We suggest that plagioclase was partially re-equilibrated during melt loss and post-emplacement decompression. Cathodoluminescence (CL) imaging shows that quartz both in the tonalities and hornfels are typically zoned from higher Ti contentsin cores to lower in the margins, suggesting a response to falling temperature. Calculated temperatures for quartz crystallization using a Ti-in-quartz calibrated for 2.5 kbar gave a wide range of values between 870 and 570 oC. This suggests that although the granitoids contain two pyroxenes and have produced a broad contact aureole, they were not emplaced at temperatures as high as it has been inferred. The new estimates are similar to the crystallization temperature of rapakivi granitoids of the Fennoscandian Peninsula.

Indoor Concentration and Composition of Fine Particulate Matter (PM2.5) Near an Intense Circulated Road in an Industrial City

The purpose of the present work is to present results from a measuring campaign during February-March 2020, in Galati city, Romania, aiming the concentration of fine particulate matter (PM2.5) in air and their heavy metal concentrations, then comparing the results with the air quality determined by the national monitoring system from the same city. Results show considerable differences concerning the air quality measured in this study compared with measurements of the national monitoring system that consist in four stations placed across the city. While values recorded in this study exceeded, in some situations, the maximum target from PM2.5, the reports from the national monitoring system presented a good air quality, using a colour- and number-coding (maximum level 4 out of 6 was reported). Heavy metal concentrations of the fine particulate matters collected in this study was compared with other studies across the world, high Fe and Zn values being registered in agglomerated and industrialized cities, including the city considered in the present study, while in a study conducted in Beijing, China most higher values between all analysed heavy metals were recorded.

Partitioning behaviour of heavy metals in Ashtamudi estuary, india

The pH, salinity, SSC and variations of heavy metals were studied for Ashtamudi estuary during the pre-monsoon period of 2019. Both pH and salinity decreased from the mouth of the estuary, while SSC exhibited a higher value within 4 to 10 Kms from the estuarine mouth. Concentrations of Fe, Cr, Cu, Zn and Ni decreased from the mouth towards the head of the estuary. Among which both Fe and Cr showed higher concentrations within 4 to 10 Kms. Variation of the distribution coefficients (Kd) of trace metals with pH, salinity and suspended sediments indicated lower values for Fe, Cr and Zn at the locations 2 and 3, . As the dissolved concentrations of Fe and Cr showed higher values at locations with higher SSC, adsorption and desorption studies were performed using sediments at those locations. Adsorption studies on Fe indicated higher adsorption at higher salinity values, while for Cr, the adsorption decreased with salinity. Kinetic adsorption and desorption studies for Fe and Cr indicated that the adsorption rates of Fe and Cr approached equilibrium after 2 hours and 1.5 hours respectively, while the desorption rates did not exhibit an equilibrium within the experiment duration. The results of kinetic sorption and desorption studies conducted for Fe and Cr exhibiting higher rate of adsorption for Fe and lower rate of adsorption for Cr at higher salinities, were in agreement with the higher Kd values of Fe and lower Kd values of Cr obtained from the field analysis.

The effects of adding Hibiscus sabdariffa L. flowers marmalade on some quality properties, mineral content and antioxidant activities of yogurt.

In this study, the effect of Hibiscus sabdariffa L. flowers marmalade (HM) addition at different ratios (0%, 15%, 20%) was determined on the certain quality properties, total phenolic contents, antioxidant activity, mineral composition and heavy metal content of stirred-type yogurts (C, HM15, and HM20). The marmalade addition increased dry matter, ash, titratable acidity and viscosity whereas decreased pH, fat and protein values. HM addition significantly increased the antioxidant properties of yogurt samples. 2,2-Diphenylpicrylhydrazyl radical-scavenging activity, Copper (II) reducing antioxidant capacity and total phenolic content were found to be in the range of 5.92-26.73mg TE/100g, 4.88-15.03mg TE/100g, and 5.57-14.69mg GAE/100g, respectively. There were no statistically differences between control and HM-added groups in terms of lactic acid bacteria (LAB) counts, also in all samples the total LAB count was above 6 Log cfu/g during the storage. Fe, Mn, B, and Ba mineral values of samples with HM were higher than control sample. Cd, As, Hg and Li heavy metals were not detected in any of the samples, consequently results were within reliable limits reported by JECFA (Joint FAO/WHO Expert Committee on Food Additives) and Turkish Food Codex. As a result of the sensory evaluation, the samples containing 20% HM generally received higher scores than the samples containing 15% HM. Considering all the parameters, it was concluded that HM yogurts can be used as a different type in the functional yogurt industry due to its pleasant and characteristic taste.

Mineral elements content of wild growing edible mushrooms from the southeast of Spain

Wild-growing mushrooms could be a potential source of mineral elements The aim of this study was to analyze the mineral composition of 18 species of wild-growing mushrooms collected in a natural park from the Spanish southeast (province of Granada). Ca, Mg, K, Na, Fe, Cu and Zn, were determined by flame atomic absorption spectroscopy and P was analyzed colorimetrically by the vanadomolybdate procedure; the accuracy of methods was assessed by the use of certified reference materials. The contribution of mushrooms consumption to the mineral daily recommended intakes was calculated. Although large variations were observed between species, the most abundant mineral elements in the analyzed mushrooms were K and P, with average contents of 29.3 ± 8.1 and 8.60 ± 4.8 g/kg dry matter (dm), respectively. Low Na concentrations were observed (26.5–579 mg/kg dm), with the only exception of Amanita ovoidea, and high Fe values, exceeding in some cases 1000 mg/kg dm (such as in Lactarius deliciosus and Morchella conica). Mushrooms may be significant contributors of K and P in the human diet and also good sources of trace elements, especially Cu and Fe, providing negligible quantities of Na. Strong correlations were observed for Ca/Mg and Cu/Zn contents in the mushrooms analyzed.

Spatial Pattern of a Comprehensive fE Index for Provincial Carbon Emissions in China

China has committed to ambitious targets to reduce its carbon emissions in the next decades, in order to combat climate change and improve the environment. The realization of the targets depends on the fair and effective mitigation plans of all provinces. However, with varying ecological and environmental conditions and social-economic development, it is a critical issue to quantify the provinces’ efforts equally. This paper proposed a comprehensive fE index in coordinating ecology, equity and economy, by accounting for carbon emissions and sinks to characterize provincial carbon emission status in China, from 2000 to 2017, which shows a spatial pattern of “boundary high, central low”. The provinces with higher fE value (>1.5) in boundary areas can be seen as “relative equality” provinces with good ecology circulation, equity and economic efficiency. The provinces with lower fE value (<0.7) in central areas around Bohai Bay are regarded as “severe inequality” provinces, and are identified as the hot-spot provinces, which have emitted more CO2 than their equity share by occupying the carbon emission space of other provinces in recent decades. These results could provide a reference for a provincial guide for carbon reduction and sustainable development of the low-carbon economy.

(Invited) Boron and Nitrogen Co-Doped Porous Carbon Nanofibers As Metal-Free Electrocatalysts for Highly Efficient Ammonia Electrosynthesis

NH3 synthesis via the electrocatalytic nitrogen reduction reaction (NRR) under ambient conditions has been regarded as a sustainable strategy for fertilizer production, hydrogen fuel storage, and mitigating greenhouse gas emissions. Electrochemical reduction reaction of nitrogen to ammonia has been widely investigated as a potential technology to overcome thermodynamic barrier of high-temperature and high-pressure needed for industrial Haber-Bosch process. The design of construction of heteroatoms (e.g., B, N, P, S) doped carbon materials have become a research focus as metal-free electrocatalysts owing to their good electrochemical stability and high electronic conductivity. N-doping carbon materials could induce the protonated pyridinic N and adjacent atomic vacancy site, which are favor of N2 adsorption. Besides, on account of charge density difference, B-doping carbon materials could induce inhomogeneity for carbon to adsorb N2 molecules. Compared with single heteroatom dopant, heteroatom co-doping could bring in charge redistribution of carbon, which can facilitate the chemisorption of N2 molecules and following electron transfer.Herein, we present a metal-free B and N co-doped porous carbon nanofibers (B/N-CNF) fabricated by an electrospinning and calcination strategy. The FESEM image of B/N-CNF showed the typical morphology of the cross-linked carbon networks composed of nanofibers with a diameter of ~100 nm. The contents of B and N dopant for B/N-CNF were 29.9% and 27.6%, respectively. The N2 adsorption-desorption isotherms curve of B/N-CNF exhibited a high BET specific surface area of 748 m2 g-1 and a mesopores structure with pore diameter of around 4 nm and volume of ~0.39 cm3 g-1. Benefitting from a high surface area and synergistic effect between B and N dopants, the B/N-CNF exhibited a high electrocatalytic activity for NRR in a basic electrolyte, achieving the highest FE of 13.2% at -0.5 V and the NH3 yield rate of 32.5 μg h-1 mg-1 cat. at -0.7 V. Such a high NRR activity was superior to most of the previously reported B- or N- doped carbon materials. It was found that B atoms facilitated the cleavage of N≡N bonds, and the N atoms enhanced the electronic conductivity of CNF nanofibers.The B/N-CNF delivered superior catalytic activity for electrochemical NRR, featured by the highest FE of 13.2% at -0.5 V and NH3 yield of 32.5 μg h-1 mg-1 cat. at -0.7 V in basic electrolytes. The high NRR performance could be attributed to the synergistic effect between B and N co-dopants. The FE value of B/N-CNF was almost the highest among all previously reported carbon-based materials with single N- or B-doping. Moreover, an electrolyzer with B/N-CNF as the cathode and commercial Ir/C as the anode was successfully fabricated to confirm the NRR activity of B/N-CNF driven by alkaline batteries and solar panels. The developed B/N-CNF presented in this work paves a promising pathway for rational design of highly efficient dual heteroatoms doped carbon materials for not only NRR, but other electrochemical energy conversion reactions.

Physical Processing of Discarded Integrated Circuits for Recovery of Metallic Values

Recycling of discarded integrated circuits is an important issue related to waste management, resource conservation, and metal recovery aspects. In this study, physical processing comprising water fluidization, magnetic separation, and density separation of discarded units was followed to recover Cu, Fe, Ni, and Si values. The fluidization technique provided an enriched metal concentrate comprising 53.05% Cu, 16.2% Fe, and 10.5% Ni in the underflow fraction, and the overflow fraction comprised 63.1% Si with 17.8% C. High metallic dissolution was attained for the processed samples compared with the feed leaching because of effective separation of the non-metallic fraction during physical processing. Overall, 1 kg of discarded ICs yielded ~ 120 g ferrous metal with ~ 57.4% Fe and ~ 26% Ni purity and ~ 390 g metallic values with 85% Cu and ~ 490 g non-metallic values with ~ 84% Si.

English

The study assessed the seasonal variations in the physico-chemical properties of surface water and sediments in some villages located around a scrap metal recycling industry in Ile-Ife. This is with a view to monitor the impact of the industry on the quality of surrounding water. The three water bodies (one river, one stream and one pond) identified in the area were sampled every other month for ten months. Water and sediment were sampled from the water bodies and their physico-chemical properties were determined using standard methods. Highest and least pH values: 7.15 ± 0.29 and 6.27 ± 0.26 were recorded in river and pond water sample, respectively during dry season, while the least pH values: 5.64 ± 0.09 were recorded in sediment samples from the river during wet season. Fe in water was highest in pond during dry season with (0.10 ± 0.01) mg/L. Stream sediment recorded higher values of Fe (1.02 ± 0.05) mg/kg, Zn (0.48 ± 0.01) mg/kg and Pb (0.09 ± 0.01) mg/kg than in stream water samples, while the values of pH, Mn, Cd and Cr (6.95 ± 0.03, 0.67 ± 0.11, 0.11 ± 0.02, 0.17 ± 0.03)mg/L respectively in stream water were higher than in stream sediment samples. In River, Fe and Zn values were higher in sediment (0.63 ± 0.04 and 0.52 ± 0.01)mg/kg respectively than in water samples, while in the pond pH, Mn, Cd and Cr were higher in water (6.51 ± 0.12, 0.71 ± 0.07, 0.09 ± 0.01 and 0.22 ± 0.03)mg/L respectively than in sediment samples. The study concluded that the scrap metal recycling industry has impact on the surrounding water bodies as the values of cadmium, lead and iron significantly exceeded the national and international standards. Key words: Physico-chemical, standards, sediment, scrap metal, seasonal, surface water. &nbsp