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1.
Nat Commun ; 11(1): 5068, 2020 10 08.
Artigo em Inglês | MEDLINE | ID: mdl-33033251

RESUMO

The mineralized collagen fibril is the basic building block of bone, and is commonly pictured as a parallel array of ultrathin carbonated hydroxyapatite (HAp) platelets distributed throughout the collagen. This orientation is often attributed to an epitaxial relationship between the HAp and collagen molecules inside 2D voids within the fibril. Although recent studies have questioned this model, the structural relationship between the collagen matrix and HAp, and the mechanisms by which collagen directs mineralization remain unclear. Here, we use XRD to reveal that the voids in the collagen are in fact cylindrical pores with diameters of ~2 nm, while electron microscopy shows that the HAp crystals in bone are only uniaxially oriented with respect to the collagen. From in vitro mineralization studies with HAp, CaCO3 and γ-FeOOH we conclude that confinement within these pores, together with the anisotropic growth of HAp, dictates the orientation of HAp crystals within the collagen fibril.


Assuntos
Colágeno/química , Minerais/química , Orientação Espacial , Osso e Ossos/química , Criança , Colágeno/ultraestrutura , Cristalização , Durapatita/química , Elétrons , Feminino , Humanos , Modelos Moleculares , Tomografia , Difração de Raios X
2.
Nat Commun ; 11(1): 3880, 2020 08 05.
Artigo em Inglês | MEDLINE | ID: mdl-32759942

RESUMO

Geological sources of H2 and abiotic CH4 have had a critical role in the evolution of our planet and the development of life and sustainability of the deep subsurface biosphere. Yet the origins of these sources are largely unconstrained. Hydration of mantle rocks, or serpentinization, is widely recognized to produce H2 and favour the abiotic genesis of CH4 in shallow settings. However, deeper sources of H2 and abiotic CH4 are missing from current models, which mainly invoke more oxidized fluids at convergent margins. Here we combine data from exhumed subduction zone high-pressure rocks and thermodynamic modelling to show that deep serpentinization (40-80 km) generates significant amounts of H2 and abiotic CH4, as well as H2S and NH3. Our results suggest that subduction, worldwide, hosts large sources of deep H2 and abiotic CH4, potentially providing energy to the overlying subsurface biosphere in the forearc regions of convergent margins.


Assuntos
Ecossistema , Hidrogênio/química , Metano/química , Minerais/química , Compostos Orgânicos/química , Termodinâmica , Amônia/química , Fenômenos Químicos , Fenômenos Geológicos , Sulfeto de Hidrogênio/química , Fenômenos Mecânicos , Fenômenos de Química Orgânica , Alcaloides de Triptamina e Secologanina/química , Erupções Vulcânicas
3.
PLoS One ; 15(8): e0237599, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32785287

RESUMO

The microbial oxidation of metal sulfides plays a major role in the formation of acid rock drainage (ARD). We aimed to broadly characterize the ARD at Ely Brook, which drains the Ely Copper Mine Superfund site in Vermont, USA, using metagenomics and metatranscriptomics to assess the metabolic potential and seasonal ecological roles of microorganisms in water and sediment. Using Centrifuge against the NCBI "nt" database, ~25% of reads in sediment and water samples were classified as acid-tolerant Proteobacteria (61 ± 4%) belonging to the genera Pseudomonas (2.6-3.3%), Bradyrhizobium (1.7-4.1%), and Streptomyces (2.9-5.0%). Numerous genes (12%) were differentially expressed between seasons and played significant roles in iron, sulfur, carbon, and nitrogen cycling. The most abundant RNA transcript encoded the multidrug resistance protein Stp, and most expressed KEGG-annotated transcripts were involved in amino acid metabolism. Biosynthetic gene clusters involved in secondary metabolism (BGCs, 449) as well as metal- (133) and antibiotic-resistance (8501) genes were identified across the entire dataset. Several antibiotic and metal resistance genes were colocalized and coexpressed with putative BGCs, providing insight into the protective roles of the molecules BGCs produce. Our study shows that ecological stimuli, such as metal concentrations and seasonal variations, can drive ARD taxa to produce novel bioactive metabolites.


Assuntos
Ácidos/química , Metagenoma , Microbiota , Mineração , Proteobactérias/genética , Proteobactérias/metabolismo , Transcriptoma , Cobre/química , Marcadores Genéticos , Minerais/química , Proteobactérias/crescimento & desenvolvimento
4.
Artigo em Inglês | MEDLINE | ID: mdl-32615055

RESUMO

The effect of the presence of minerals in natural soil polluted with lead (II) was investigated to verify the efficiency of the electrokinetic remediation method. Natural soil "Sebkha of Oran" containing high calcite minerals and characterized by high salinity was used in experimental studies. This study investigates the effects of alkaline soil pH conditions on the transport and removal of lead by the electrokinetic treatment. XRD analyses were performed on the soil sample before and after electrokinetic treatment to determine any changes in mineral phases. Mathematical models using experimental data are developed to describe the mobility and diffusion coefficient of lead ions through the soil. Mathematical models were generated based on the physicochemical parameters characterizing the movement of cations and anions.


Assuntos
Técnicas Eletroquímicas/métodos , Recuperação e Remediação Ambiental/métodos , Chumbo/análise , Modelos Teóricos , Poluentes do Solo/análise , Solo/química , Ânions , Cátions , Minerais/química
5.
Artigo em Inglês | MEDLINE | ID: mdl-32720573

RESUMO

Glauconite is one of natural clay minerals that are low-cost and readily available. Its specific characters, including potassium cations activity, layered structure and absorption capacity, explain the comprehensive interest to this mineral. It is especially prospective in regard of water treatment. Glauconite composition depends on the formation conditions, which lead to different sorption properties. Here we studied the sorption parameters and physical characteristic of unique glauconite of the Bakchar deposit by mean of granulometric analysis, electromagnetic separation, X-ray fluorescence analysis, inductively coupled plasma-mass spectroscopy, petrographic studies, scanning electron microscopy, X-ray diffraction analysis, nitrogen thermal desorption method, inversion voltammetry. Finally, we tested this mineral as a sorbent. The studied glauconitic concentrate has the best comparative sorption properties. Results show that glauconite of the Bakchar deposit is a cheap and prospective sorbent for heavy metals.


Assuntos
Metais Pesados/química , Minerais/química , Adsorção , Nitrogênio/química , Estudos Prospectivos , Sibéria
6.
Chemosphere ; 260: 127574, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32688316

RESUMO

Artisanal and small-scale gold mining (ASGM) operations are major contributors to the Philippines' annual gold (Au) output (at least 60%). Unfortunately, these ASGM activities lacked adequate tailings management strategies, so contamination of the environment is prevalent. In this study, soil contamination with copper (Cu), lead (Pb), zinc (Zn) and arsenic (As) due to ASGM activities in Nabunturan, Davao de Oro, Philippines was investigated. The results showed that ASGM-impacted soils had Cu, Pb, Zn and As up to 3.6, 83, 73 and 68 times higher than background levels, respectively and were classified as 'extremely' polluted (CD = 30-228; PLI = 5.5-34.8). Minerals typically found in porphyry copper-gold ores like pyrite, chalcopyrite, malachite, galena, sphalerite and goethite were identified by XRD and SEM-EDS analyses. Furthermore, sequential extraction results indicate substantial Cu (up to 90%), Pb (up to 50%), Zn (up to 65%) and As (up to 48%) partitioned with strongly adsorbed, weak acid soluble, reducible and oxidisable fractions, which are considered as 'geochemically mobile' phases in the environment. Although very high Pb and Zn were found in ASGM-impacted soils, they were relatively immobile under oxidising conditions around pH 8.5 because of their retention via adsorption to hydrous ferric oxides (HFOs), montmorillonite and kaolinite. In contrast, Cu and As release from the historic ASGM site samples exceeded the environmental limits for Class A and Class C effluents, which could be attributed to the removal of calcite and dolomite by weathering. The enhanced desorption of As at around pH 8.5 also likely contributed to its release from these soils.


Assuntos
Mineração , Poluentes do Solo/análise , Poluentes do Solo/química , Solo/química , Arsênico/análise , Arsênico/química , Cobre/análise , Cobre/química , Ouro/análise , Ferro/química , Compostos de Ferro/química , Chumbo/análise , Chumbo/química , Minerais/química , Filipinas , Sulfetos/química , Difração de Raios X , Zinco/análise , Zinco/química
7.
Food Chem ; 331: 127291, 2020 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-32559598

RESUMO

This study investigated inulin and calcium-rich milk mineral incorporation into a pork sausage in order to examine the effects on microbiome and biochemical activity in the gastrointestinal tract upon ingestion. Rats (n = 48) were fed one of four sausages; a pork sausage enriched with 1) inulin (6.0%) and milk mineral (3%), 2) inulin (6.0%), 3) milk mineral (3%) or 4) control sausages without enrichment. NMR-based metabolomics revealed that inulin-enrichment increased the fecal concentration of short-chain fatty acids (SCFAs). Milk mineral-enrichment also increased SCFA concentrations, although less pronounced. In addition, milk mineral reduced the concentration of nitroso compounds in feces and small intestinal content. Combined enrichment with both inulin and milk mineral showed no cumulative effect on SCFA formation and seemed to oppose the milk mineral-induced reduction of nitroso compound formation. 16S rRNA gene amplicon sequencing indicated that alterations of the gut microbiome contributed to the observed effects.


Assuntos
Microbioma Gastrointestinal/efeitos dos fármacos , Inulina/química , Produtos da Carne/análise , Leite/química , Minerais/química , Carne Vermelha/análise , Animais , Suplementos Nutricionais/análise , Fezes/química , Masculino , Ratos
8.
J Chromatogr A ; 1624: 461242, 2020 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-32540080

RESUMO

Natural estrogens (estrone: E1, 17ß-estradiol: E2, estriol: E3) and the synthetic estrogen (17α-ethinylestradiol: EE2) are endocrine disruptors harmful to aquatic wildlife. The European Commission included these molecules in the surface water Watch Lists issued in 2015 and 2018 under the Water Framework Directive regarding emerging aquatic pollutants, proposing maximum detection limits (LOD) of 0.035 ng/L for EE2 and 0.4 ng/L for E1 and E2. Attaining these limits represents a challenge even with the most up-to-date analytical tools, in particular in surface water. A two-step sample preparation, involving a preliminary extraction of a whole water sample on a solid-phase extraction (SPE) disk and further purification on a Florisil SPE cartridge, was optimized. The purified extract was derivatized subsequently and quantified by LC-MS/MS. The main goal was to maximize the recoveries to achieve the very low LODs required by the European Watch Lists. The method was fully validated in seven surface water. The LODs calculated were below the maximum acceptable limits required by the European Commission.


Assuntos
Estrogênios/análise , Poluentes Químicos da Água/análise , Calibragem , Cromatografia Líquida , Disruptores Endócrinos/análise , Monitoramento Ambiental/métodos , União Europeia , Água Subterrânea/química , Limite de Detecção , Silicatos de Magnésio/isolamento & purificação , Minerais/química , Reprodutibilidade dos Testes , Extração em Fase Sólida , Espectrometria de Massas em Tandem
9.
PLoS One ; 15(5): e0232403, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32374774

RESUMO

We present novel multi-energy X-ray imaging methods for direct radiography and computed tomography. The goal is to determine the contribution of thickness, mass density and atomic composition to the measured X-ray absorption in the sample. Algorithms have been developed by our own to calculate new X-ray images using data from an unlimited amount of scans/images of different tube voltages by pixelwise fitting of the detected gray levels. The resulting images then show a contrast that is influenced either by the atomic number of the elements in the sample (photoelectric interactions) or by the mass density (Compton scattering). For better visualization, those images can be combined to a color image where different materials can easily be distinguished. In the case of computed tomography no established true multi-energy methodology that does not require an energy sensitive detector is known to the authors. The existing dual-energy methods often yield noisy results that need spatial averaging for clear interpretation. The goal of the method presented here is to qualitatively calculate atomic number and mass density images without loosing resolution while reducing the noise by the use of more than two X-ray energies. The resulting images are generated without the need of calibration stan-dards in an automatic and fast data processing routine. They provide additional information that might be of special interest in cases like archaeology where the destruction of a sample to determine its composition is no option, but a increase in measurement time is of little concern.


Assuntos
Radiografia/métodos , Tomografia Computadorizada por Raios X/métodos , Algoritmos , Simulação por Computador , Processamento de Imagem Assistida por Computador/métodos , Processamento de Imagem Assistida por Computador/estatística & dados numéricos , Imageamento Tridimensional/métodos , Imageamento Tridimensional/estatística & dados numéricos , Ciência dos Materiais , Minerais/química , Radiografia/estatística & dados numéricos , Espalhamento de Radiação , Tomografia Computadorizada por Raios X/estatística & dados numéricos , Raios X
10.
Chemosphere ; 255: 126948, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32387733

RESUMO

Uranium phosphites have recently emerged as promising materials to remediate radioactive contamination. In this study, the redox mechanisms of uranyl phosphites at mineral surfaces have been addressed by periodic DFT calculations with dispersion corrections. Different from other ligands, the phosphite anions (H2PO3-, HPO32-) are efficient reducing agents for uranyl reduction, and the redox reactions are divided into three steps, as isomerization between two phosphite anion isomers (Step 1), conformational transition (Step 2) and dissociation of the water molecule (Step 3). A second water molecule is critical to lower the activation barriers of Step 1, and all activation barriers are moderate so that the redox reactions occur favorably under normal conditions, which are further dramatically accelerated by the highly exergonic Step 3. Accordingly, formation of uranyl phosphites becomes an effective approach to manage uranium pollution. Moreover, the lower activation barriers for H2PO3- rather than HPO32- rationalize the superior reduction activities of uranyl phosphites and the enhanced stability of U(IV) products at lower pH conditions. Owing to the cooperative proton/electron transfer, the U(VI) reduction to U(IV) and P(III) oxidation to P(V) are completed within one step, with transition states being featured by the U(V) and P(IV) species.


Assuntos
Minerais/química , Fosfitos/química , Urânio/química , Transporte de Elétrons , Elétrons , Oxirredução , Prótons
11.
Ambix ; 67(2): 107-134, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32285758

RESUMO

The article explores the use of minerals and the nature of chemical methods employed in Lima in the sixteenth and early seventeenth centuries. It does so through examining the availability of mineral resources, including pre-European knowledge of their use, through surveying the books and equipment used by physicians and apothecaries, and finally by examining prescriptions for medicines that were used to treat patients. It concludes that minerals were probably more commonly employed in medicines in Lima than in Spain but suggests that their preparation and use at this time drew on Spain's alchemical tradition rather than on writings by Paracelsus and his followers. It argues that this did not reflect the effectiveness of censorship by the Inquisition.


Assuntos
Alquimia , Minerais/história , Médicos/história , Prescrições/história , Colonialismo , História do Século XVI , História do Século XVII , Humanos , Minerais/química , Minerais/uso terapêutico , Peru , Prescrições/estatística & dados numéricos , Espanha
12.
Ecotoxicol Environ Saf ; 197: 110629, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32325329

RESUMO

A new Electrocoagulation (EC) technique, sinusoidal AC coagulation (SACC), is creatively put forward for Cu2+ removal in the wastewater from the printed circuit board (PCB) production in this paper. The removal efficiency of Cu2+ from PCB wastewater and energy consumption are compared by SACC and conventional direct current coagulation (DCC). The optimal process parameters were established through analysis of response surface methodology (RSM). The coagulations containing Cu2+ was characterized by SEM, EDS, TEM,BET, XRD and FTIR. The nano-ferrum collosol, mainly composed of goethite (α-FeOOH) and magnetite (γ-Fe2O3), absorbs the Cu2+ and coagulates to remove Cu2+. The results show that the removal rates of Cu2+ by SACC and DCC are 99.86% and 98.21%, respectively, and the energy consumption is 2.76 × 10-2 kWh⋅m-3 for SACC and 4.42 × 10-2 kWh⋅m-3 for DCC under the optimal process conditions of c0 (Cu2+) = 41.99 mg⋅dm-3, pH = 7.14, j = 0.293 A⋅m-2, t = 16.7 min. The pilot tests indicate that the SACC technique is feasible in industrial application. Cu2+ removal were completed through electrodeposition of Cu2+ on iron electrode, the deposition of Cu(OH)2 and the adsorption of Cu2+ by ferrum collosol. The adsorption follows the pseudo-second order kinetics model well. The maximum saturated adsorption capacity (qmax) of Cu2+ on ferrum collosol produced by SACC is larger than that by DCC. The adsorption of Cu2+ on the ferrum collosol prepared by SACC and DCC are in accordance with Langmuir's adsorption isotherms. The novel SACC technique is a promising technique for the highly-efficient treatment of Cu2+ from PCB wastewater.


Assuntos
Cobre/análise , Técnicas Eletroquímicas/métodos , Águas Residuárias/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Eletrodos , Óxido Ferroso-Férrico/química , Floculação , Compostos de Ferro/química , Cinética , Minerais/química
13.
Chemosphere ; 253: 126691, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32294599

RESUMO

Low redox potential in flooded soils may affect phosphate bioavailability by reducing iron oxides or formation of new minerals. To investigate phosphate behavior in anoxic conditions, goethite was selected as a soil model and coated by humic acid (HA) and sodium borohydride was used as a reducing agent. Adsorption experiments were conducted in 0.1 M NaNO3 as a function of pH in oxic (Eh = +254 to +448 mV) and suboxic (Eh = -162 to +167 mV) conditions for four phosphate concentrations (0.05-0.8 mM). CD-MUSIC and NOM-CD models in combination with Extended Stern model were used to describe the experimental data. Results show that by increasing pH and carbon content in the organo-mineral composites, the released phosphate to the solution increases in both oxic and suboxic conditions. In suboxic conditions, as a result of sodium borohydride dissociation in water and consequently boron release to the solution, at high loading of boron and low loading of phosphate, boron can compete with phosphate for the surface reactive sites and decrease its adsorption. On the other hand, ferrous iron can attenuate boron effect and promote phosphate adsorption. The results indicated that goethite surface is resistant to the reductive transformation that may occur at relatively low redox potential due to its high crystalline character and thermodynamic stability. HA may, however, promote the formation of amorphous iron phases, which consequently might induce phosphate adsorption in OM-mineral composites. The derived affinity constants in oxic conditions described the experimental data of suboxic conditions reasonably well.


Assuntos
Compostos de Ferro/química , Minerais/química , Modelos Químicos , Fosfatos/química , Adsorção , Boro , Carbono , Compostos Férricos , Substâncias Húmicas , Ferro , Solo/química
14.
Chemosphere ; 253: 126650, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32268252

RESUMO

This study firstly reported a novel nano humboldtine/almandine composite (NHLA composite) prepared directly from almandine through one-pot method based on the interaction of almandine and oxalic acid. The formation of humboldtine/almandine binary phase from natural almandine was determined by X-ray diffraction. Analysis of scanning & transmission electron microscope showed that large amount of nano humboldtine with uniform size (average size of 15.59 nm) were loaded on the almandine sheets. Compared with raw minerals, Pb(Ⅱ) removal capacity of synthesized composite was significantly increased, demonstrating that the main active ingredient for Pb(Ⅱ) removal was humboldtine phase rather than almandine itself. Pb(Ⅱ) adsorption capacity was increased with the increasing of initial pH value or temperature. Langmuir isotherm and Pseudo-second order kinetic equation were well fitted with experimental results and the maximum Pb(Ⅱ) adsorption capacity from Langmuir isotherm was 574.71 mg/g at temperature of 25 °C. In addition, heavy metal removal experiments in coexisting systems of multiple heavy metal ions manifested that the composite had a high selectivity for Pb(Ⅱ) adsorption. Ion exchange, surface complexation and electrostatic interaction have involved in the Pb(Ⅱ) adsorption. The synthesized composite was considered as a low cost, high efficiency, super selectivity and easy to mass production material for Pb(Ⅱ) adsorption from solution.


Assuntos
Chumbo/química , Modelos Químicos , Adsorção , Concentração de Íons de Hidrogênio , Íons , Cinética , Metais Pesados , Minerais/química , Difração de Raios X
15.
Proc Natl Acad Sci U S A ; 117(14): 7719-7728, 2020 04 07.
Artigo em Inglês | MEDLINE | ID: mdl-32213582

RESUMO

Chitin is the most abundant renewable nitrogenous material on earth and is accessible to humans in the form of crustacean shell waste. Such waste has been severely underutilized, resulting in both resource wastage and disposal issues. Upcycling chitin-containing waste into value-added products is an attractive solution. However, the direct conversion of crustacean shell waste-derived chitin into a wide spectrum of nitrogen-containing chemicals (NCCs) is challenging via conventional catalytic processes. To address this challenge, in this study, we developed an integrated biorefinery process to upgrade shell waste-derived chitin into two aromatic NCCs that currently cannot be synthesized from chitin via any chemical process (tyrosine and l-DOPA). The process involves a pretreatment of chitin-containing shell waste and an enzymatic/fermentative bioprocess using metabolically engineered Escherichia coli The pretreatment step achieved an almost 100% recovery and partial depolymerization of chitin from shrimp shell waste (SSW), thereby offering water-soluble chitin hydrolysates for the downstream microbial process under mild conditions. The engineered E. coli strains produced 0.91 g/L tyrosine or 0.41 g/L l-DOPA from 22.5 g/L unpurified SSW-derived chitin hydrolysates, demonstrating the feasibility of upcycling renewable chitin-containing waste into value-added NCCs via this integrated biorefinery, which bypassed the Haber-Bosch process in providing a nitrogen source.


Assuntos
Quitina/química , Nitrogênio/química , Resíduos/análise , Acetilglucosamina/metabolismo , Animais , Carbono/farmacologia , Quitosana/química , Crustáceos , Escherichia coli/genética , Engenharia Genética , Glucose/metabolismo , Hidrólise , Levodopa/metabolismo , Minerais/química , Nitrogênio/farmacologia , Polimerização , Tirosina/metabolismo
16.
Chemosphere ; 249: 126531, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32213392

RESUMO

The mineral composition and surface physico-chemical properties, i.e., specific surface area (SSA), cation exchange capacity (CEC), and surface charge of recent sediments and their submicron mineral fractions from different sedimentological environments of the Eastern Adriatic were investigated. The influence of organic matter on these properties was also investigated. It was shown that illite and mixed-layered clay minerals (MLCM) were ubiquitous and showed no size-related preferences while the occurrence of smectites, chlorites, and kaolinites varied. The smectites content increased and the chlorites decreased slightly with decreasing particle size. The sediments from the carbonate-rich environment contained no smectites or chlorites and had the highest kaolinite content. For the first time, in the recent sediments of the Adriatic Sea the poorly- and the well-crystallised kaolinite (Kl and KlD) were distinguished. While Kl predominates in the submicron-sized fraction, KlD occurred only in micron-sized fractions. Authigenic aragonite of submicron-sized was determined in a distinct environment of the semi-enclosed marine lake. The differences in mineral composition and particle size of sediments and their separated fractions were reflected in a wide range of the SSA and CEC values obtained. The highest values of SSA and CEC were determined in the phyllosilicates-rich submicron-sized fractions range, 109 m2g-1 and 87.4 cmol+kg-1, respectively. The submicron-sized fraction from aragonite-rich marine lake showed the lowest values of SSA (56.4 m2g-1) and CEC (38.8 cmol+kg-1), which are still unexpectedly high for carbonate-rich environments. The removal of organic matter resulted in a significant increase in SSA and CEC, up to 150% and 76%, respectively.


Assuntos
Monitoramento Ambiental , Sedimentos Geológicos/química , Poluentes Químicos da Água/análise , Carbonato de Cálcio , Cátions/química , Argila , Itália , Caulim/química , Lagos , Minerais/análise , Minerais/química , Propriedades de Superfície
17.
J Fluoresc ; 30(2): 317-327, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32016910

RESUMO

Herein, we report the preparation of a fluorescent sensor based on coumarin derivative for copper (II) ion sensing in CH3CN/HEPES media. 6,7-dihydroxy-3-(4-(trifluoro)methylphenyl)coumarin (HMAC) sensor was fabricated and analyzed by spectroscopic techniques. The sensor demonstrates "turn on-off" fluorescence quenching in the presence of copper (II) ions at 458 nm. A clear complex between the chemosensor HMAC and copper (II) ions was characterized by ESI-MS as well as the Job's method. Also, the limit of detection (LOD, 3σ/k) value was determined as 24.5 nM in CH3CN/HEPES (95/5, v/v) buffer media (pH = 7.0). This value is lower than the admissible level of copper (II) ions in drinking water (maximum 31.5 µM) reported by EU Water Framework Directive (WFD) and World Health Organization (WHO) guidelines. The theoretical calculations (density functional theory, DFT) have been performed for the geometric optimized structures. As a final stage, real sample analyses have successfully been performed by using HMAC, as well as ICP-OES method. The relative standard deviation for copper (II) in mineral and drinking water samples has been determined to be below 0.15% and recovery values are in the range of 95.48-109.20%.


Assuntos
Cobre/análise , Cumarínicos/química , Teoria da Densidade Funcional , Água Potável/química , Corantes Fluorescentes/química , Minerais/química , Cumarínicos/síntese química , Fluorescência , Corantes Fluorescentes/síntese química , Íons/análise , Estrutura Molecular , Espectrometria de Fluorescência
18.
Chemosphere ; 248: 126111, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32050318

RESUMO

Leaching of toxic metallic elements (Cu, Zn, As, Cd, and Pb) from two solid mine wastes was characterized under different drying treatments. During 14 batch decant-refill leaching steps, samples were intermittently dried four times in 40 °C oven or -20 °C freezer. For all leachates, the pH, pE, Fe2+/Fe3+, and SO42- were analyzed. The parameters of the two-site model (kfast, kslow, and ffast) and labile fractions (F1 + F2) were determined. High levels of toxic metallic elements were determined in waste samples; however, their leaching was limited, as evidenced by the magnitudes of F1 + F2, ffast, and kslow. Leachate solutions were acidic, at pH 3-4, and oxic, at 150 mV < Eh 300 < mV, thus having negligible Fe2+. Leachate concentrations of toxic metallic elements increased (4-58%) after drying at 40 °C and were strongly correlated (r2 = 0.780) with those of sulfate in liquid phase. The mass of element elution was in the order of 40 °C drying > -20 °C drying ≥ continuous wetting. Results indicate that the element leachability is increased through drying events and the leachate concentration is associated with the dissolution reaction of sulfur-bearing minerals. Frequent occurrence of prolonged droughts along with high temperatures over the mine waste disposal site, can enhance the leaching potential of toxic metallic elements.


Assuntos
Metais Pesados/análise , Minerais/química , Mineração , Resíduos Sólidos/análise , Sulfatos/análise , Poluentes Químicos da Água/análise , Secas , Temperatura Alta , Metais Pesados/química , República da Coreia , Sulfatos/química , Poluentes Químicos da Água/química
19.
Chemosphere ; 248: 126112, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32069698

RESUMO

Coal fly ash (CFA) is one of the most promising secondary sources of rare earth elements and yttrium (REY). This research first studied the modes of occurrence of REY in CFA collected from a China's power generation plant which utilizes a coal feedstock with an elevated REY content. The fact that rare earth minerals remain in CFA and REY associate with metal oxides was proved by emission-scanning electron microscope with an energy-dispersive X-ray spectrometer. The technical feasibility of recovery of REY from CFA was then studied through conducting various physical separation methods followed by acid leaching. It was found that REY are concentrated in fine particle size, non-magnetic and middle density fractions. Using combined physical separation processes, the REY of CFA was enriched from 782 µg·g-1to 1025 µg g-1. The acid leaching process was optimized for various parameters via the Taguchi three-level experimental design. Upon optimization, the physical separation product was leached at the optimum condition and 79.85% leaching efficiency was obtained. Based on the obtained results, a conceptual process flowsheet was developed for recovery of REY from CFA. Such recovery maximizes REY resources utilization and enhances sustainability of CFA disposal.


Assuntos
Cinza de Carvão/química , Metais Terras Raras/análise , Minerais/química , Centrais Elétricas , Eliminação de Resíduos/métodos , Ácidos/análise , Fracionamento Químico , China , Campos Magnéticos , Solubilidade , Ítrio/análise
20.
PLoS One ; 15(2): e0228717, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32027704

RESUMO

Conservation farming (CF), involving basin tillage, residue retention and crop rotation, combined with biochar may help to mitigate negative impacts of conventional agriculture. In this study, the effects of CF on the amount and quality of soil organic matter (SOM) and potential nitrogen (N) mineralization were investigated in a maize-soya-maize rotation in an Acrisol in Zambia. A large field was run under CF for 7 years and in the subsequent three growing seasons (2015-2018), four management practices were introduced to study effects on soil characteristics and crop yield. We tested i) a continuation of regular CF (CF-NORM) ii) CF without residue retention (CF-NO-RES); iii) Conventional (CONV), with full tillage and removal of residues; and iv) CF with 4 ton ha-1 pigeon pea biochar inside basins and residue retention (CF-BC). The experiment involved the addition of fertilizer only to maize, while soya received none. Soya yield was significantly higher in CF systems than in CONV. Maize yields were not affected by the different management practices probably due to the ample fertilizer addition. CF-NORM had a higher stock of soil organic carbon (SOC), higher N mineralization rates, more hot-water extractable carbon (HWEC; labile SOC) and particulate organic matter (POM) inside basins compared to the surrounding soil (outside basins). Our results suggest that the input of roots inside basins are more effective increasing SOM and N mineralization, than the crop residues that are placed outside basins. CONV reduced both quality and quantity of SOM and N mineralization as compared to CF inside basins. CF-BC increased the amount of SOC as compared with CF-NORM, whereas N mineralization rate and HWEC remained unaffected. The results suggest benefits on yield of CF and none of biochar; larger impact of root biomass on the build-up of SOM than crop residues; and high stability of biochar in soil.


Assuntos
Agricultura/métodos , Carbono/análise , Carvão Vegetal/farmacologia , Produtos Agrícolas/crescimento & desenvolvimento , Minerais/química , Nitrogênio/química , Solo/química , Biomassa , Conservação dos Recursos Naturais , Produtos Agrícolas/efeitos dos fármacos , Umidade
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