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1.
Food Chem ; 336: 127675, 2021 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-32795781

RESUMO

The present study explores the biosorption potential of Pleurotus ostreatus immobilized magnetic iron oxide nanoparticles for solid-phase extractions of Ni(II) and Pb(II) ions from the water and food samples. It was characterized using FTIR, FE-SEM/EDX before and after analyte ions biosorption. Important operational parameters including the effect of initial pH, the flow rate of the sample solution and volume, amount of biomass and support material, interfering ions, best eluent, column reusability were studied. The biosorption capacities of fungus immobilized iron oxide nanoparticles were found as 28.6 and 32.1 mg g-1 for Ni(II) and Pb(II), respectively. The limit of detection (LOD) and limit of quantitation (LOQ) were achieved as 0.019 and 0.062 ng mL-1 for Ni(II), 0.041 and 0.14 ng mL-1 for Pb(II), respectively. The proposed method was validated by applying to certified reference materials and successfully applied for the preconcentrations of Ni(II) and Pb(II) ions from water and food samples by ICP-OES.


Assuntos
Chumbo/isolamento & purificação , Nanopartículas/química , Níquel/isolamento & purificação , Pleurotus/química , Extração em Fase Sólida/métodos , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Células Imobilizadas , Compostos Férricos/química , Análise de Alimentos/instrumentação , Análise de Alimentos/métodos , Contaminação de Alimentos/análise , Concentração de Íons de Hidrogênio , Limite de Detecção , Fenômenos Magnéticos , Níquel/química , Reprodutibilidade dos Testes , Extração em Fase Sólida/instrumentação , Poluentes Químicos da Água/química
2.
Sci Total Environ ; 753: 141743, 2021 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-32891989

RESUMO

Nickel oxide nanoparticles (NiO-NPs) have extensively used in industrial and consumer products. The present study conducted to gain more knowledge about the safe use of NiO-NPs and also to understand their impact on the environment and biological systems. Herein, we examined the genotoxic and ultra-structural effects of a sublethal dose of NiO-NPs (0.03 mg/g) on the ovarian tissues of the ground beetle, Blaps polycresta. The mean diameter of NiO-NPs was 24.49 ± 3.88 nm, as obtained through transmission electron microscopy (TEM). In terms of DNA damage levels, the frequency of micronucleus (MN) formation was highly significant in the NiO-NPs treated group versus the controls. Besides, NiO-NPs treatment resulted in a significant increase in the tail length of comets. Further, electron microscopy revealed a progressive increase in chromatin condensation of the ovarian nurse and follicular cells, in addition to the accumulation of lysosomes and endo-lysosomes in their cytoplasm. In conclusion, NiO-NPs are capable of gaining access to the ovary of B. polycresta and causing DNA damage and a high degree of cellular toxicity in the ovarian cells. The present study highlights, for the first time, the adverse effects of these NPs to female gonads of insects and raised the concern of its genotoxic potential. It would be of interest to investigate NiO-NPs mediated intracellular ROS generation in future studies.


Assuntos
Besouros , Nanopartículas Metálicas , Nanopartículas , Animais , Dano ao DNA , Feminino , Nanopartículas Metálicas/toxicidade , Níquel/toxicidade
3.
Zhonghua Lao Dong Wei Sheng Zhi Ye Bing Za Zhi ; 38(10): 767-769, 2020 Oct 20.
Artigo em Chinês | MEDLINE | ID: mdl-33142384

RESUMO

Objective: To set up a new method to determine the nickel of urine in urine using dispersive liquid-liquid microextraction (DLLME) coupled with graphite furnace atomic absorption spectrometry (GFAAS) . Methods: From September 2018 to September 2019, the methanol, pyrrolidine dithiocarbamate and ionic liquid 1-hexyl-3-methyl-imidazolium hexafluorophosphate were used as dispersive solvent, the chelating agent and extraction solvent for the preconcentration of nickel, respectively. After adding into buffer solution of pH 9, ultrasonic dissolving for 10 minutes, centrifugal separation and then discarding the supernatant, the precipitate was saved. Dissolving the precipitate by methanol, mixing thoroughly on a vortex mixer, the 15 µl of the mixed solution was used for determination by graphite furnace atomic absorption spectrometry. Results: The linear correlation coefficient of urine nickel concentration in the range of 2.0-10.0 µg/L, r=0.999, with the detection limitation of 0.43 µg/L. The recovery rate and the relative standard deviations were 95.6%-103.7% and 2.53%-4.82%, respectively. Conclusion: The method, which has low detection limit, high recovery rate and good precision, is suitable for the determination of nickel in urine for the occupational populations exposure to nickel and non-occupational exposure.


Assuntos
Grafite , Líquidos Iônicos , Limite de Detecção , Níquel , Espectrofotometria Atômica , Ultrassom
4.
Waste Manag ; 118: 677-687, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33011545

RESUMO

A multi-analytical methodology is implemented to characterize several sieving fractions of industrial samples of Black Mass (BM) powders originating from the thermo-mechanical treatment of cylindrical and prismatic-type spent nickel metal-hydride (Ni-MH) batteries. Elemental analyses of 17 elements (including C and O) indicate that the elemental composition of the powders (greater than93 %wt) does not depend on the battery type nor on the sieving fraction. XRD analyses evidence several phases (including Ni, NiO, CeO2 and C) but their quantification is not possible. Beyond these standard characterisations, magnetic susceptibility measurements demonstrate that the amount of metallic nickel versus nickel oxide increases with the sieving fraction, and that powders from prismatic-type batteries contain twice as much metallic nickel than cylindrical ones. Thanks to statistical analysis (based on clustering algorithms) of an electron probe µ-analysis (EPMA) compositional map, the complete methodology allows us to propose a full phase distribution for the BM particles. Three types of particles are identified and quantified. They originate from the partial oxidation of the battery components (anode active mass, anode current collector, cathode active mass and cathode current collector). The whole picture highlights the joint importance of battery ageing mechanisms, thermal deactivation and BM sieving steps on powder composition.


Assuntos
Metais , Níquel , Fontes de Energia Elétrica , Eletrodos , Pós
5.
Nat Commun ; 11(1): 5075, 2020 10 08.
Artigo em Inglês | MEDLINE | ID: mdl-33033245

RESUMO

Nickel-iron composites are efficient in catalyzing oxygen evolution. Here, we develop a microorganism corrosion approach to construct nickel-iron hydroxides. The anaerobic sulfate-reducing bacteria, using sulfate as the electron acceptor, play a significant role in the formation of iron sulfide decorated nickel-iron hydroxides, which exhibit excellent electrocatalytic performance for oxygen evolution. Experimental and theoretical investigations suggest that the synergistic effect between oxyhydroxides and sulfide species accounts for the high activity. This microorganism corrosion strategy not only provides efficient candidate electrocatalysts but also bridges traditional corrosion engineering and emerging electrochemical energy technologies.


Assuntos
Desulfotomaculum/metabolismo , Hidróxidos/metabolismo , Níquel/metabolismo , Oxigênio/metabolismo , Corrosão , Teoria da Densidade Funcional , Eletroquímica , Eletrodos , Análise Espectral Raman , Espectroscopia por Absorção de Raios X
6.
J Contemp Dent Pract ; 21(6): 636-639, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-33025932

RESUMO

AIM: Variation in the surface roughness of archwires not only leads to more accumulation of plaque but also modifies the coefficient of friction. This necessitated for the present study to evaluate the surface characteristics of 0.016 × 0.022-inch nickel-titanium, beta-titanium, and copper-nickel-titanium archwires, before and after their use in the oral cavity using atomic force microscopy. MATERIALS AND METHODS: The control and experimental samples were measured at three different positions under atomic force microscopy. The surface roughness was measured using roughness average, root mean square, and maximum height before and after use in the oral cavity among 60 adult participants. Data were analyzed using a one-way analysis of variance and Student's t tests using the Statistical Package for Social Software (SPSS) v.20.0. RESULTS: The surface roughness of archwires increased considerably after their clinical use compared to controls for nickel-titanium (p = 0.013) and beta-titanium (p = 0.002). A similar trend was noticed for root mean square where nickel-titanium (p = 0.014) and beta-titanium (p = 0.013) had increased root mean square. Maximum height was also noticed in nickel-titanium (p = 0.031) and beta-titanium (p = 0.016). CONCLUSION: Surface roughness and the level of friction of the orthodontic wires increase significantly for nickel-titanium and beta-titanium after the clinical use. There is a difference in increase of surface roughness of the archwire within and between the bracket slots. CLINICAL SIGNIFICANCE: Nickel-titanium and beta-titanium wires show more roughness and resultant higher friction levels after use in the oral cavity. Hence, care related to plaque accumulation is essential.


Assuntos
Cobre , Níquel , Ligas Dentárias , Humanos , Teste de Materiais , Propriedades de Superfície , Titânio
7.
Yakugaku Zasshi ; 140(10): 1213-1224, 2020.
Artigo em Japonês | MEDLINE | ID: mdl-32999200

RESUMO

In basic pharmaceutical sciences to achieve drug development, research on the efficient chemical synthesis of small molecules having cyclic skeletons is important. We have been engaged in the development of artificial catalysts for asymmetric ring formation reactions that exclusively synthesize right-handed or left-handed cyclic compounds and have achieved the construction of optically active cyclic skeletons using our original catalysts. The synthesis of biologically active compounds was facilitated through six-membered ring construction by Diels-Alder reaction of Danishefsky diene; however, no asymmetric variant of the reaction has been achieved. We approached this unresolved issue using multi-coordinated lanthanide metals. A new chiral lanthanide catalyst was developed, and the catalytic asymmetric Diels-Alder reaction of Danishefsky diene was realized for the first time. By modifying the chemical structure of Danishefsky diene, we applied the lanthanide catalyst to the syntheses of polycyclic compounds and biologically active compounds. We achieved the asymmetric synthesis of natural products, antibacterial and antimalarial compounds, and an anti-obesity drug lead compound. Moreover, the novel catalyst exhibited higher performance than the previously reported ones. The latest generation of the catalyst can be handled stably in air at room temperature. Furthermore, we succeeded in the development of new catalysts by focusing on the properties of its metal precursors, such as nickel and indium, and achieved the construction of polycyclic skeletons by using these catalysts.


Assuntos
Compostos Heterocíclicos/síntese química , Compostos Policíclicos/síntese química , Alcenos/química , Antibacterianos/síntese química , Fármacos Antiobesidade/síntese química , Antimaláricos/síntese química , Produtos Biológicos/síntese química , Catálise , Reação de Cicloadição , Desenvolvimento de Medicamentos , Índio , Elementos da Série dos Lantanídeos/química , Níquel , Estereoisomerismo
8.
Indian J Dent Res ; 31(4): 569-573, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33107458

RESUMO

Aim: To evaluate the biodegradability of preformed stainless steel crowns at varying salivary pH and the cytotoxic effect of leached out elements on fibroblasts. Methodology: A total of 243 stainless steel crowns were selected and were divided into 3 groups (I, II, III) based on Ph of immersion media. The pH of samples in group I, II, III were 4.3, 5.5 and 6.3 with 81 crowns in each group. Each group has 9 samples with 8 crowns in each sample. All samples were immersed in polyethylene bottles containing 10ml of artificial saliva and incubated at 37°C for 4 weeks. All the samples were analyzed on 1,7,14 and 21 days by atomic absorption spectrophotometer for the quantitative assement of Ni, Cr and Fe. Fibroblast tissue culture was used to assess the cytotoxicity of the samples. Statistical Analysis: Analysis of variance. Results: Maximum release of Ni, Cr, Fe ions were observed at pH 4.3 followed by pH 5.5 and least release of ions were observed at pH 6.3 from SS crowns. The cytotoxic results showed that the least cell viability of cells was seen at pH 4.3. Conclusion: With decrease in pH, there is an increase in ion release from stainless steel crowns and the mean release of nickel, chromium and iron were very much below the average dietary intake. But the allergic manifestations of ions like nickel can't be ruled out.


Assuntos
Níquel , Aço Inoxidável , Cromo , Coroas , Concentração de Íons de Hidrogênio
9.
Indian J Dent Res ; 31(4): 579-584, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33107460

RESUMO

Aims: To evaluate and compare the efficacy of four rotary instrumentation systems in root canal retreatment and to determine retreatment time. Materials and Methods: To achieve the purpose of this study, canals of 60 distal roots in mandibular molar teeth were selected and randomly divided into four groups A, B, C and D (n = 15). Using step-back technique, the canals were prepared and filled with gutta-percha and AH Plus employing cold lateral compaction technique. The root filling material was removed with the following retreatment systems: Group A: Mtwo R, group B: D-RaCe, group C: ProTaper R and group D: R-Endo. In order to record retreatment time, a stopwatch was used. The samples were split longitudinally, examined under a stereomicroscope, photographed and assessed with AutoCAD software. Finally, the percentages of remaining filling material were calculated and the extracted data were analyzed using one-way ANOVA and Tukey HSD test. Results: All examined groups showed traces of remaining filling material within the canals. No statistically significant difference was found among the four groups in the coronal, middle, and apical thirds. The same result was obtained with regard to retreatment time (P > 0.05). However, within each one of the groups, significant difference was observed in the three regions (P < 0.05). Conclusions: Based on the findings of this study, none of the examined systems could completely remove root filling material from the root canals. However, they were all found to be effective in this regard. The most amount of remaining filling material was found in the apical third.


Assuntos
Guta-Percha , Materiais Restauradores do Canal Radicular , Cavidade Pulpar , Níquel , Retratamento , Preparo de Canal Radicular , Titânio
10.
Mol Cell ; 80(2): 210-226.e7, 2020 10 15.
Artigo em Inglês | MEDLINE | ID: mdl-33002424

RESUMO

Many bacterial pathogens regulate their virulence genes via phase variation, whereby length-variable simple sequence repeats control the transcription or coding potential of those genes. Here, we have exploited this relationship between DNA structure and physiological function to discover a globally acting small RNA (sRNA) regulator of virulence in the gastric pathogen Helicobacter pylori. Our study reports the first sRNA whose expression is affected by a variable thymine (T) stretch in its promoter. We show the sRNA post-transcriptionally represses multiple major pathogenicity factors of H. pylori, including CagA and VacA, by base pairing to their mRNAs. We further demonstrate transcription of the sRNA is regulated by the nickel-responsive transcriptional regulator NikR (thus named NikS for nickel-regulated sRNA), thereby linking virulence factor regulation to nickel concentrations. Using in-vitro infection experiments, we demonstrate NikS affects host cell internalization and epithelial barrier disruption. Together, our results show NikS is a phase-variable, post-transcriptional global regulator of virulence properties in H. pylori.


Assuntos
Helicobacter pylori/genética , Helicobacter pylori/patogenicidade , RNA Bacteriano/genética , Sequências Repetitivas de Ácido Nucleico/genética , Fatores de Virulência/metabolismo , Proteínas de Bactérias/metabolismo , Sequência de Bases , Contagem de Colônia Microbiana , Endocitose/efeitos dos fármacos , Deleção de Genes , Regulação Bacteriana da Expressão Gênica/efeitos dos fármacos , Helicobacter pylori/efeitos dos fármacos , Interações Hospedeiro-Patógeno/efeitos dos fármacos , Níquel/farmacologia , Fenótipo , Regiões Promotoras Genéticas , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Transcrição Genética/efeitos dos fármacos
11.
Bull Environ Contam Toxicol ; 105(5): 777-783, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33044567

RESUMO

The capacity of Lemna minor to remediate toxic heavy metals from wastewater is reasonably well documented. In view of the pivotal role of this species in the environmental clean-up, here we evaluated the bioaccumulation potential of L. minor for cadmium (Cd), lead (Pb), and nickel (Ni) through a controlled experiment. L. minor tolerated the metals Cd, Ni, and Pb up to 0.5, 5, and 8 mg/L, respectively, and beyond these concentrations the toxicity symptoms appeared. Bio-concentration factor varied at different concentrations of heavy metals tested. Overall, L. minor showed good phytoremediation potential for all the three tested heavy metals (Cd, Ni, and Pb), though in relative terms it was more effective in extracting Ni and Cd, as compared to Pb, both in single and mixed concentrations. In view of the growing pollution in Kashmir Himalayan aquatic habitats the phytoremediation by invasive species such as L. minor promises to be one of the best choices than other native plants for cleaning up of polluted soils/water because of its fast growth rate, high abundance, easy handling, and wide distribution in Kashmir Himalayan aquatic ecosystems.


Assuntos
Organismos Aquáticos/metabolismo , Araceae/metabolismo , Bioacumulação , Metais Pesados/metabolismo , Águas Residuárias/química , Organismos Aquáticos/crescimento & desenvolvimento , Araceae/crescimento & desenvolvimento , Biodegradação Ambiental , Cádmio/análise , Cádmio/metabolismo , Ecossistema , Índia , Lagos , Chumbo/análise , Chumbo/metabolismo , Metais Pesados/análise , Níquel/análise , Níquel/metabolismo
12.
Int J Nanomedicine ; 15: 7215-7234, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33061377

RESUMO

Background: With excellent shape memory and superelastic properties, shape memory alloy (SMA) is an ideal actuator, and it can form smart structure for different applications in medical field. However, SMA devices cause apparent thermal damage to the surrounding tissues when it works in vivo, making the application of smart structure that is composed of SMA actuator in vivo is greatly limited. Methods: In this paper, coating (APA) with PLA as the main body to limit the heat conduction, a multifunctional Ag nanoparticles (AgNPs)/polylactic acid (PLA)/Al2O3 was synthesized. The Al2O3 layer was formed by micro-arc oxidation (MAO) and AgNPs were synthesized by silver nitrate and ethylene glycol. Scanning electron microscopy, transmission electron microscope, and Fourier transform infrared spectra were applied to analyze the morphology and characterization of APA coating. The antimicrobial activity, thermal insulation activity, and biocompatibility of APA coating were furtherly explored and verified through animal experiments and immunohistochemistry. Results: With different particle sizes and concentrations of AgNPs, APA multi-functional films were successfully prepared. The Al2O3 layer was closely combined with SMA and formed a porous surface, so the PLA and AgNPs layers can firmly adhere to SMA, thus reducing the release of nickel ions in SMA. AgNPs gave APA coating excellent antibacterial activity and effectively inhibited the growth of Staphylococcus aureus. In addition, coupled with the low thermal conductivity of PLA and Al2O3, AgNPs were tightly anchored on the surface of PLA, which has high infrared reflectivity, making the APA coating obtain good thermal insulation performance. Conclusion: We have successfully prepared the APA coating and obtained the optimum amount of AgNPs, which makes it have good thermal insulation performance, good antibacterial activity and good biocompatibility, which provides a new prospect for the application of SMA.


Assuntos
Antibacterianos/farmacologia , Materiais Revestidos Biocompatíveis/farmacologia , Níquel/farmacologia , Temperatura , Titânio/farmacologia , Óxido de Alumínio/farmacologia , Animais , Linhagem Celular , Nanopartículas Metálicas/química , Nanopartículas Metálicas/ultraestrutura , Camundongos , Testes de Sensibilidade Microbiana , Poliésteres/farmacologia , Coelhos , Prata/farmacologia , Staphylococcus aureus/efeitos dos fármacos
13.
J Contemp Dent Pract ; 21(7): 728-732, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-33020354

RESUMO

AIM: The aim of the present study is twofold: to evaluate cyclic fatigue resistance differences of two different nickel-titanium rotary instruments, brand new and after an ex vivo instrumentation of single root extracted teeth. MATERIALS AND METHODS: Twenty new S One 20.06 were randomly divided into two groups. The first group (n = 10) was immediately subjected to a cyclic fatigue test (S One Group I). The second group (n = 10) (S one Group II) performed a cyclic fatigue test after three ex vivo root canal treatment with a single-file technique. The same process has been carried out for 20 M-Two 20.06 instruments. RESULTS: Mean time to fracture (TtF) for Group I was 51.14 ± 1.28 for S One and 32.62 ± 0.17 for M-Two 20.06 and for Group II was 46.00 ± 0.99 for S One and 27.75 ± 1.58 for M-Two 20.06. The reduction in TtF values from Group I to Group II was 11% for S One and 15% for M-Two. Statistical analysis found significant differences in all the groups examined (p value < 0.05). Mean fragment length (FL) for Group I was 3.07 ± 0.17 for S One and 3.05 ± 0.14 for M-Two 20.06 and for Group II was 3.05 ± 0.07 for S One and 3.05 ± 0.14 for M-Two 20.06. Statistical analysis was pursued, and no significant difference was found (p value > 0.05). CONCLUSION: The S-One showed significantly more resistance to cyclic fatigue stress than M-Two for both new and used instruments. This validates the hypothesis that the AF H wire enables the S One files to endure more the cyclic fatigue stresses. CLINICAL SIGNIFICANCE: This study demonstrates the cyclic fatigue resistance of a new endodontic instrument after repetitive usage.


Assuntos
Níquel , Titânio , Cavidade Pulpar , Desenho de Equipamento , Falha de Equipamento , Teste de Materiais , Preparo de Canal Radicular
14.
Nat Commun ; 11(1): 5101, 2020 10 09.
Artigo em Inglês | MEDLINE | ID: mdl-33037208

RESUMO

Urease converts urea into ammonia and carbon dioxide and makes urea available as a nitrogen source for all forms of life except animals. In human bacterial pathogens, ureases also aid in the invasion of acidic environments such as the stomach by raising the surrounding pH. Here, we report the structure of urease from the pathogen Yersinia enterocolitica at 2 Å resolution from cryo-electron microscopy. Y. enterocolitica urease is a dodecameric assembly of a trimer of three protein chains, ureA, ureB and ureC. The high data quality enables detailed visualization of the urease bimetal active site and of the impact of radiation damage. The obtained structure is of sufficient quality to support drug development efforts.


Assuntos
Proteínas de Bactérias/química , Proteínas de Bactérias/metabolismo , Urease/química , Urease/metabolismo , Yersinia enterocolitica/enzimologia , Domínio Catalítico , Microscopia Crioeletrônica , Lisina/metabolismo , Modelos Moleculares , Níquel/química , Níquel/metabolismo , Conformação Proteica , Domínios Proteicos , Água/química
15.
Bull Environ Contam Toxicol ; 105(5): 685-691, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33067667

RESUMO

Owls are predators that perform important ecological functions. There are several threats to owl conservation such as the bioaccumulation of chemicals through environmental contamination. The high probability of bioaccumulation in these animals is related to their role as predators and high trophic positions. The objective of this study was to quantify four elements (cadmium, chromium, nickel, and lead) as the biomarkers of environmental exposure in owls. To this end, we analyzed pellets and feathers of different owl species. These matrices were contaminated with all four elements, with chromium most commonly detected. Chromium and nickel were found in the pellets in all 10 months of the study, and May was the month with the highest concentrations of all the elements. Tyto furcata appears to bioaccumulate more elements in its feathers than Megascops spp. and Athene cunicularia. Our findings showed bioaccumulation of these four elements in owls and their environment.


Assuntos
Monitoramento Biológico/métodos , Poluição Ambiental/análise , Plumas/química , Conteúdo Gastrointestinal/química , Metais Pesados/análise , Estrigiformes/crescimento & desenvolvimento , Animais , Cádmio/análise , Cromo/análise , Refluxo Laringofaríngeo , Chumbo/análise , Metais Pesados/metabolismo , Níquel/análise
17.
Chemosphere ; 254: 126869, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32957283

RESUMO

This paper presents the results of Co(II) and Ni(II) extraction from model and real solutions using bis(2,4,4-trimethylpentyl)phosphinic acid (i.e. Cyanex 272) that are in agreement with waste-to-resources approach, i.e. the recovery of valuable components from wastes. The results from this study shows that, extraction using Cyanex 272 is an efficient method to recover Co(II) selectively from sulfate electrolytes obtained from the leaching of steel scraps of aircraft engines. The highest selectivity value (∼160) of Co(II) extraction over Ni(II) was obtained at a pH of 4.8, the lowest selectivity value (∼30) was observed at a pH of 5.5, while above this value the selectivity only increased slightly with increasing pH. A pH of 5.2 was selected as a compromise between Co(II) selectivity and Ni(II) amount in the organic phase. The essence of the investigation is to propose important parameters to extract Co(II) from real leach solutions, and to further recover valuable Co(II) from the loaded organic phase by stripping with 1 M H2SO4, thus producing an electrolyte of Co(II) for electrowinning - a possible alternative route for resource recovery. Small volume of the stripping phase (w/o = 1:5) used in this study, lead to an enrichment of sulfate electrolyte in Co(II), resulting in ∼50 g/dm3 of Co(II) in the solution, which is a great advantage of the approach proposed. Such a solution is a valuable source for the electrowinning of metallic cobalt, which can be used for the production of steel alloys, Li-ion batteries or catalysts.


Assuntos
Cobalto/química , Modelos Químicos , Níquel/química , Ácidos Fosfínicos/química , Fontes de Energia Elétrica , Lítio , Sulfatos
18.
Water Sci Technol ; 82(4): 759-772, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32970627

RESUMO

In recent years, carbon tetrachloride (CT) has been frequently detected in surface water and groundwater around the world; it is necessary to find an effective way to treat wastewater contaminated with it. In this study, Ni/Fe bimetallic nanoparticles were immobilized on reduced graphene oxide (NF@rGO), and used to dechlorinate CT in aqueous solution. Scanning electron microscopy (SEM) demonstrated that the two-dimensional structure of rGO could disperse nanoparticles commendably. The results of batch experiments showed that the 4N4F@rGO (Fe/GO = 4 wt./wt., and Ni/Fe = 4 wt.%) could reach a higher reduction capacity (143.2 mgCT/gcatalyst) compared with Ni/Fe bimetallic nanoparticles (91.7 mgCT/gcatalyst) and Fe0 nanoparticles (49.8 mgCT/gcatalyst) respectively. That benefited from the nickel metal as a co-catalyst, which could reduce the reaction activation energy of 6.59 kJ/mol, and rGO as an electrical conductivity supporting material could further reduce the reaction activation energy of 4.73 kJ/mol as presented in the conceptual model. More complete dechlorination products were generated with the use of 4N4F@rGO. Based on the above results, the reductive pathway of CT and the catalytic reaction mechanism have been discussed.


Assuntos
Ferro , Níquel , Tetracloreto de Carbono , Grafite , Cinética
19.
Nat Commun ; 11(1): 4557, 2020 09 11.
Artigo em Inglês | MEDLINE | ID: mdl-32917908

RESUMO

Why metalloenzymes often show dramatic changes in their catalytic activity when subjected to chemically similar but non-native metal substitutions is a long-standing puzzle. Here, we report on the catalytic roles of metal ions in a model metalloenzyme system, human carbonic anhydrase II (CA II). Through a comparative study on the intermediate states of the zinc-bound native CA II and non-native metal-substituted CA IIs, we demonstrate that the characteristic metal ion coordination geometries (tetrahedral for Zn2+, tetrahedral to octahedral conversion for Co2+, octahedral for Ni2+, and trigonal bipyramidal for Cu2+) directly modulate the catalytic efficacy. In addition, we reveal that the metal ions have a long-range (~10 Å) electrostatic effect on restructuring water network in the active site. Our study provides evidence that the metal ions in metalloenzymes have a crucial impact on the catalytic mechanism beyond their primary chemical properties.


Assuntos
Anidrases Carbônicas/química , Íons/química , Metaloproteínas/química , Metais/química , Sítios de Ligação , Anidrase Carbônica II/química , Anidrase Carbônica II/metabolismo , Anidrases Carbônicas/metabolismo , Catálise , Domínio Catalítico , Cobalto/química , Cobre/química , Cristalografia por Raios X , Humanos , Íons/metabolismo , Cinética , Metaloproteínas/metabolismo , Metais/metabolismo , Modelos Moleculares , Níquel/química , Conformação Proteica , Relação Estrutura-Atividade , Especificidade por Substrato , Zinco/química
20.
PLoS One ; 15(9): e0238790, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32903275

RESUMO

The potential mechanical impact of different rotary systems used for root canal preparation has been a matter of debate for long. The aim of this study was to explore the incidence of dentinal cracks after root canal instrumentation with various rotary systems, in vitro. One hundred and eighty intact lower central incisors were selected and randomly divided into fourteen treatment groups (n = 12/group) and a control group (n = 12). After decoronation, the root canals were instrumented with fourteen different rotary systems (E3, E3 azure, NT2, Hyflex CM, Hyflex EDM, 2Shape, OneCurve, ProTaper Next, ProTaper Gold, WaveOne Gold, Mtwo, Reciproc Blue, TF adaptive, K3XF). All roots were horizontally sectioned at 3, 6, and 9 mm from the apex with a low-speed saw under water-cooling. The slices were then examined under stereomicroscope for dentinal cracks. No cracks were found in the control group. Cracks were found in all treatment groups, predominantly in the 3 mm slices. There was no statistically significant difference in the number of cracks when comparing the different systems to each other at any section level. At 3 mm, however, five of the studied systems, namely K3XF (p = 0.004), Protaper Next (p = 0.001), Reciproc Blue (p<0.001), TF adaptive (p = 0.050), and 2Shape (p = 0.009) presented a significantly higher number of cracks than the control group. Within the limitations of this study, instrumented canals presented dentinal cracks, while uninstrumented ones presented no cracks after sectioning. There seems to be no significant difference among the tested systems regarding crack formation in the instrumented root canal wall. Crack formation occurred irrespective of the motion of the rotary system (rotational or reciprocation). Further studies are needed to clarify the factors that contribute to crack formation in the case of each individual rotary system.


Assuntos
Níquel , Preparo de Canal Radicular/instrumentação , Titânio , Ligas Dentárias , Dentina/lesões , Desenho de Equipamento , Humanos , Técnicas In Vitro , Tratamento do Canal Radicular/métodos
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