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1.
Chemosphere ; 239: 124788, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31521935

RESUMO

Digestion of biomass derived carbonaceous materials such as biochar (BC) can be challenging due to their high chemical recalcitrance and vast variations in composition. Reports on the development of specific sample digestion methods for such materials remain inadequate and thus require considerable attention. Nine different carbonaceous materials; slow-pyrolyzed tea-waste and king coconut BC produced at 300 °C, 500 °C and 700 °C, sludge waste BC produced at 700 °C, wet fast-pyrolyzed Douglas-Fir BC and steam activated coconut shell BC have been tested to evaluate a relatively fast and convenient open-vessel digestion method using seven digestion reagents including nitric acid (NA), fuming nitric acid (FNA), sulfuric acid (SA), NA/SA, FNA/SA, NA/H2O2 and SA/H2O2 mixtures. From the tested digestion reagents, SA/H2O2 mixture dissolved low temperature produced BC (LTBC) within 2 h with occasional shaking and no external heating. Except peroxide mixtures, the other reagents were used to evaluate microwave digestion (MWD) efficiency. Nitric acid mixture was capable of only completely digesting LTBC in the MWD procedure whereas FNA, NA/SA and FNA/SA mixtures resulted in the successful dissolution of all tested carbonaceous materials. Amongst them, FNA provided the least matrix effect in the quantification of the four metals tested using flame atomic absorption spectrophotometry. Tested recoveries for FNA were satisfactory as well. It was concluded that FNA is a preferable reagent for microwave digestion of BC.


Assuntos
Carvão Vegetal/química , Resíduos , Cocos , Indústria de Laticínios , Peróxido de Hidrogênio , Metais/análise , Micro-Ondas , Ácido Nítrico/química , Pirólise , Esgotos , Espectrofotometria Atômica/métodos , Ácidos Sulfúricos/química
2.
Water Sci Technol ; 80(1): 86-97, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31461425

RESUMO

The present study investigated the preparation of nitric acid modified powder activated carbon (MPAC) and its adsorption of trace amounts of Ni(II) from aqueous solution. Results showed that raw powder activated carbon modified with 15% nitric acid (MPAC-15%) had the most developed pore structure and the highest adsorption efficiency for Ni(II) in aqueous solution. For MPAC-15%, the pore width was dominated by micropores with pore width about 1 nm and the total amount of chemical functional groups of MPAC-15% was 0.6630 mmol/g. Ni(II) adsorption tests indicated that the highest adsorption efficiency of MPAC-15% was 98%. The adsorption saturation time of MPAC-15% was about 120 min and the pH-dependent adsorption test showed that neutral conditions (6.5 < pH < 7.5) were suitable for Ni(II) adsorption. The adsorption kinetic analysis revealed that the pseudo-second order adsorption model fitted the adsorption process significantly. Thus, Ni(II) adsorption by MPAC-15% was dominated not only by physical adsorption via highly developed micropores but also by chemical adsorption between Ni(II) and surface functional groups. Adsorption isotherm analysis illustrated the Langmuir model was favorable for the adsorption of Ni(II), with R2 = 0.9874.


Assuntos
Níquel/química , Ácido Nítrico/química , Poluentes Químicos da Água/química , Adsorção , Carvão Vegetal , Concentração de Íons de Hidrogênio , Cinética , Purificação da Água
3.
Food Chem ; 299: 125172, 2019 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-31325716

RESUMO

The composition of inorganic elements is a key factor in determining the quality of fruit wines. However, the use of direct sample injection is challenging for multi-elemental analysis of fruit wine samples. In this paper, an analytical method using inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) was established for determining multiple elements (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Cd, Hg, and Pb) in fruit wine. The fruit wine was diluted using ultrapure water and acidified with nitric acid before injecting into the ICP-MS/MS. Spectral interferences in the complex matrix composition of different fruit wine samples, in the MS/MS mode, were eliminated using mixed reaction gases of O2/H2 and NH3/He/H2 through the mass shift and on-mass methods. The limits of detection ranged from 0.41 to 58.1 ng L-1. This study demonstrates a new approach for multi-elemental analysis in fruit wine with great convenience and high accuracy.


Assuntos
Análise de Alimentos/métodos , Espectrometria de Massas em Tandem/métodos , Oligoelementos/análise , Vinho/análise , Amônia/química , Frutas , Gases/química , Hidrogênio/química , Ácido Nítrico/química , Oxigênio/química
4.
Mater Sci Eng C Mater Biol Appl ; 103: 109795, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31349459

RESUMO

Porous gold nanoparticles (GNPs) attracted considerable attention due to their remarkable properties. The porous GNPs due to the high surface area-to-volume ratio have potential applications in areas such as drug delivery, biosensors, and fuel cells. The most frequently used method for synthesis of porous GNPs is the de-alloying approach. Despite the benefits of this approach, the nanoparticles synthesized by this method were not very stable. Nevertheless, we report herein a novel, facile and simple method for synthesis of stable porous GNPs based on Tween 20-capped GNPs (Tween GNPs) and nitric acid. On the other hand, when DNA is loaded to GNPs surface, the resulted conjugates have the potential to be used in different fields such as biomedicine, materials science and especially in nano-biotechnology. Generally, the DNA loading on GNPs is performed using a salt-aging method and its incubating time takes about 24 h. Here, GNPs was replaced by porous GNPs and the incubation time for loading was reduced to 2 h without the needs for tedious salt addition process.


Assuntos
DNA/química , Ouro/química , Nanopartículas Metálicas/química , DNA/metabolismo , Ácido Nítrico/química , Polissorbatos/química , Porosidade , Eletricidade Estática
5.
Talanta ; 204: 592-601, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31357339

RESUMO

Development of conjugated polymers with fluorescence sensing characteristics has received close attention from researchers in fields of environmental protection, biosensing and toxins detection on food. In this paper, novel polyaniline derivatives of poly(9-methyl-9H-carbazol-3-amine) and poly(9,9-dihexyl-9H-fluoren-2-amine) are prepared by facile chemical polymerization. Then they are characterized with NMR (Nuclear Magnetic Resonance), GPC (Gel Permeation Chromatography), XRD (X-Ray Diffraction), FT-IR (Fourier Transform Infrared spectroscopy), FL (Fluorescence spectrometry) and UV-vis (Ultraviolet-visible spectroscopy) characterizations and further applied to the fluorescence detection of different acids and amines. Moreover, the obtained poly(9-methyl-9H-carbazol-3-amine) displays excellent fluorescence properties in the detection for both acids and amines. Besides, this poly(9-methyl-9H-carbazol-3-amine) can not only be used for fluorescence detection in solution, but also can be prepared into solid state and applied in the gas phase fluorescence detection. This work has greatly expanded the scope of application to these polyaniline derivatives materials, opening a new path for the researches on multi-functional chemosensor.


Assuntos
Compostos de Anilina/química , Carbazóis/química , Fluorenos/química , Corantes Fluorescentes/química , Compostos de Anilina/síntese química , Carbazóis/síntese química , Etilenodiaminas/análise , Etilenodiaminas/química , Fluorenos/síntese química , Fluorescência , Corantes Fluorescentes/síntese química , Ácido Clorídrico/análise , Ácido Clorídrico/química , Ligações de Hidrogênio , Limite de Detecção , Metilaminas/análise , Metilaminas/química , Ácido Nítrico/análise , Ácido Nítrico/química , Reprodutibilidade dos Testes , Espectrometria de Fluorescência/métodos
6.
Talanta ; 204: 663-669, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31357350

RESUMO

A high-throughput, sensitive and rapid method was developed for the determination of Zn, Cu and Fe in small volumes (30 µL) of human serum using inductively coupled plasma mass spectrometry (ICP-MS). The sample preparation procedure employed simple 100-fold dilution of the serum samples with 1.0% butanol, 0.5% v/v ammonia, 0.02% v/v Triton X-100 and 0.01% v/v HNO3. The reliability of the method was evaluated using serum UTAK certified reference material, and the results matched well with the certified values. The method was applied to determine Zn, Cu and Fe in 81 human serum samples from participants in Alzheimer disease (AD) and age-related macular degeneration (AMD) studies. No significant differences were found in Zn and Cu levels between age matched controls, AD and AMD patients. Whilst iron levels appeared marginally higher in the AMD group, compared with the AD group, iron showed larger overall variability than the other two elements.


Assuntos
Cobre/sangue , Ferro/sangue , Espectrometria de Massas/métodos , Zinco/sangue , Doença de Alzheimer/sangue , Amônia/química , Humanos , Degeneração Macular/sangue , Ácido Nítrico/química , Octoxinol/química
7.
J Pharm Biomed Anal ; 174: 471-478, 2019 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-31228850

RESUMO

This study proposes an analytical procedure for microwave-assisted sample preparation of dietary supplements for athletes using dilute nitric acid solution followed by determination of elemental impurities (As, Cd, Hg and Pb) by inductively coupled plasma mass spectrometry (ICP-MS) according to the United States Pharmacopeia Chapters 2232 and 233. Calibration strategies as internal standardization (IS), multi-isotope calibration (MICal), and one-point standard addition (OP SA) were applied for correction of matrix effects. The optimization of the sample preparation procedure was performed using Doehlert experimental design based on overall desirability results (residual acidity, dissolved organic carbon and recoveries reached for certified reference material of Typical Diet) for each calibration method evaluated. Accuracy was also evaluated by recovery experiments according to the permissible daily exposure specific for each element and samples were spiked with element concentrations of 0.5J and 1.5J in order to check accuracies for As, Cd, Hg and Pb. Recoveries ranged from 82 to 120% using IS, 90 to 125% using MICal, 88 to 120% using OP SA and the repeatability was demonstrated by a precision lower than 10% RSD. Ten samples of dietary sport supplements were analyzed using the three calibration methods evaluated and the concentrations of As, Cd and Pb determined in eight samples were lower than the limits established by the Chapter 2232.


Assuntos
Arsênico/análise , Cádmio/análise , Suplementos Nutricionais/análise , Chumbo/análise , Mercúrio/análise , Micro-Ondas , Ácido Nítrico/química , Calibragem , Limite de Detecção , Espectrometria de Massas , Padrões de Referência , Reprodutibilidade dos Testes , Oligoelementos/análise
9.
Anal Chim Acta ; 1065: 1-11, 2019 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-31005141

RESUMO

This work proposed a procedure for microwave-assisted sample preparation of medicines using diluted nitric acid followed by determination of elemental impurities using inductively coupled plasma optical emission spectrometry (ICP OES) and inductively coupled plasma mass spectrometry (ICP-MS) according to the United States Pharmacopeia Chapters 232 and 233. Three solutions, i.e. inverse aqua regia, 7.0 and 2.0 mol L-1 HNO3, were evaluated for microwave-assisted digestion of nine drugs samples. The applicability of each digestion procedure was assessed by comparison of analyte concentrations determined using total (reference procedure) and partial digestions (proposed procedure) as well as by determining dissolved carbon content and evaluating matrix effects. There were none significant differences at a 95% confidence level among the concentrations determined applying reference and proposed procedures. Internal standardization (ICP OES) and aerosol dilution (ICP-MS) were applied for minimization and correction of matrix effects. Addition and recovery experiments were performed according to oral permissible daily exposures values specific for each element and each sample was spiked with element concentrations of 0.5J and 1.5J in order to check accuracies for 24 analytes. Recoveries ranged from 70 to 138% for ICP OES and from 72 to 128% for ICP-MS, for all elements but Os. All analytes were below the respective limits of quantification when applying all sample preparation procedures, except As, Ba, Co, Cu, Cr, Mo, Ni, Pb, Sb, Sn, Tl and V, however the determined concentrations for these elements were lower than the limits proposed by Chapter 232.


Assuntos
Micro-Ondas , Preparações Farmacêuticas/análise , Farmacopeias como Assunto , Oligoelementos/análise , Espectrometria de Massas , Ácido Nítrico/química , Comprimidos/análise , Estados Unidos
10.
Carbohydr Polym ; 211: 75-83, 2019 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-30824106

RESUMO

Potato peel waste (PPW) is employed as the first report on bacterial cellulose (BC) production by Gluconacetobacter xylinus. Scharification of PPW was performed by 2 M different mineral acids individually. The suitable pre-treatment conditions were determined by reducing sugar release. Although all acid PPW-hydrolysates culture media are studied to produce BCs. Nitric acid hydrolysate gives the high productivity value The influence of nitric acid PPW-hydrolysate culture condition parameters were applied throughout the Taguchi method and the optimum conditions for the highest BC yield (4.7 g/L) was observed after 6 days at 35 °C, pH 9, medium volume 55 ml and with 8% inoculum size. The instrumental analysis of PPW-BC, included FT-IR, Particle size distribution, BET, DSC, XRD and SEM are cleared that the PPW-BC recorded high crystalliny82.5%, excellent PDI. In general, this study revealed that nitric acid PPW-hydrolysate could be used as cost effective alternative medium for production of BC with sustainable processes that can overcome the environmental pollution.


Assuntos
Celulose/metabolismo , Gluconacetobacter xylinus/metabolismo , Solanum tuberosum , Química Verde , Ácido Nítrico/química , Reciclagem , Resíduos
11.
PLoS One ; 14(2): e0211859, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30721256

RESUMO

Here we propose a single acid digestion (SAD) sample preparation method for ICP-MS analysis of animal serum samples to determine trace element contents. The method was evaluated in comparison with a commonly used procedure involving dilution of samples in an alkaline solution (AKD). In the SAD procedure, aliquots (1 mL) of bovine serum samples were treated at low temperature with a mixture of concentrated nitric acid and hydrogen peroxide. Trace elements (As, B, Ba, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Mo, Ni, Pb, Sb, Se, Sr, U, and Zn) were directly determined by ICP-MS analysis of diluted solutions of samples. Both methods were sufficiently sensitive to enable quantification of most trace elements, with the exception of the AKD method for Cd, Hg and Pb. The quality of the data was verified by using certified reference material. Good results were obtained for the SAD procedure and all elements, but recoveries were unacceptable with the AKD procedure for Se (recovery: 57%), Cd (154%) and Fe (139%). Strong associations (R2>0.90, P = 0.000) between the data obtained by both methods were demonstrated for the elements considered. The proposed SAD sample preparation method produced satisfactory results for determining most toxic and essential trace elements targeted in monitoring studies.


Assuntos
Ácidos/química , Espectrometria de Massas , Oligoelementos/sangue , Oligoelementos/isolamento & purificação , Animais , Bovinos , Peróxido de Hidrogênio/química , Ácido Nítrico/química , Análise Espectral , Oligoelementos/química , Oligoelementos/classificação
12.
Food Chem ; 273: 159-165, 2019 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-30292363

RESUMO

A microwave-assisted digestion procedure using diluted HNO3 and H2O2 was developed for multi-element determination in guarana samples by ICP OES. Optimization step was performed employing a mixture design with pseudocomponents using HNO3, H2O2 and H2O. The analytical signal of each element, residual acidity and residual carbon content were optimized simultaneously using the desirability function. The best condition for digestion of a 250 mg sample mass resulted from a mixture constituted by 1.0 mL of HNO3, 3.0 mL of H2O2 and 6.0 mL of H2O. This condition allowed final digests with residual acidity and residual carbon content of 0.4 mol L-1 and 6.5%, respectively. The method was validated and applied for the determination of K, Ca, Mg, S, P, Cu, Fe, Mn and Zn in 72 guarana seed samples from Bahia state. This work presents unpublished results about the mineral composition of guarana seed samples produced in Bahia state, Brazil.


Assuntos
Análise de Alimentos/métodos , Paullinia/química , Análise Espectral/métodos , Brasil , Carbono/análise , Peróxido de Hidrogênio/química , Metais/análise , Micronutrientes/análise , Micro-Ondas , Ácido Nítrico/química , Sementes/química
13.
Anal Sci ; 35(3): 283-287, 2019 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-30393237

RESUMO

The traditional pretreatment methods for the determination of cadmium in grain are time-consuming, cost-consuming, and unfriendly to human health and the environment. To eliminate these disadvantages, we developed an accurate, time-, energy- and cost-efficient method for determination of Cd in grain coupled with graphite furnace atomic absorption spectrometry (GFAAS). The optimization conditions of the extraction were achieved, the accuracy was verified and a collaborative study was organized to evaluate the methods. The detection limit and quantification limit were 0.016 and 0.048 µg L-1, respectively. The whole pretreatment time was reduced to 15 min, and there was no significant difference (P >0.05) between the extraction method and the classic pretreatment method. The method proved to be highly consistent with the results of laboratories in different countries, as determined from two international proficiency tests (| Z | ≤0.3). The repeatability, reproducibility, and HorRat values of the collaborative results were 2.7 - 4.9%, 9.4 - 11.7%, and 0.42 - 0.58, respectively. The method of diluted acid mild extraction coupled with GFAAS is efficient, cost-saving, convenient and friendly.


Assuntos
Cádmio/análise , Fracionamento Químico/métodos , Grão Comestível/química , Poluentes Ambientais/análise , Ácido Nítrico/química , Espectrofotometria Atômica/métodos , Limite de Detecção , Reprodutibilidade dos Testes
14.
Chemosphere ; 220: 28-39, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30579171

RESUMO

Controlling of pre-oxidation conditions can effectively enhance the aimed active functional groups via promoting the oxidation and grafting reaction on biochar's surface. Here, the effect of different nitric acid pre-oxidation concentration (NAPOC) was investigated on the type and content of active oxygen-containing functional sites during the pre-oxidation stage, as well as the active nitrogen-containing binding sites for the following grafting process. And the possible reaction mechanisms for introducing nitrogen/oxygen-containing functional groups such as amide, pyridinic, carbonyl, carboxyl, etc., into the surface by ethylenediamine (EDA) were proposed. The samples were characterized by various analyses including N2 adsorption/desorption, Boehm titration, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Results showed that the NAPOC played a crucial role in promoting the formation of oxygen-containing initiators, and difference of NAPOC resulted in different reaction principles. At higher NAPOC, more carbonyl, carboxyl and hydroxyl functional groups were formed, which facilitated the decoration of nitrogen binding active sites of amide and pyridinic for mercury ions adsorption into the carbon lattice of mesoporous biomass-derived biochar (MBB). The proportions of micropore and mesopore remained basically unchanged, indicating that the decorated nitrogen/oxygen sites were highly uniformly dispersed in MBB's frame and thus resulted in high activity. The comparison of adsorption properties of MBB showed that MBB-25-EDA had the highest adsorption capacity of 153 mg g-1 at pH 6, confirming that the 25% was the optimum NAPOC for introducing nitrogen/oxygen functional binding sites for effectively anchoring mercury.


Assuntos
Carvão Vegetal/química , Etilenodiaminas/química , Mercúrio/isolamento & purificação , Ácido Nítrico/farmacologia , Adsorção , Sítios de Ligação , Domínio Catalítico , Ácido Nítrico/química , Nitrogênio/química , Oxirredução , Oxigênio/química , Porosidade
15.
Biol Trace Elem Res ; 187(2): 357-366, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29948909

RESUMO

Influence of fixation medium and storage conditions as well as impact of sample mineralisation procedure on determination of minerals in human fascia lata was examined and discussed. Freezing and storage in 10% neutral buffered formalin solution and in 2.5% glutaraldehyde were used as the preservation methods of the samples. The concentrations of, both essential and toxic, elements were measured by ICP-OES method in fascia lata samples mineralised with concentrated nitric acid in a closed microwave system and in open vessels heated on a hot plate. Freezing was found as the best preserving method of fascia lata samples because of the number of elements determined and determination precision. The trace element (Cd, Cr, Cu, Fe, Ni, Sr, Zn) concentrations obtained in samples decomposed using the conventional hot plate were different from analogous measurements in solutions obtained after application of closed vessels and microwave energy assistance. Differences between the mineral compositions of fascia samples variously preserved and mineralised were statistically evaluated and discussed. Interelement correlations were analysed taking into account an impact of various methods of sample conservation. Strong, positive association between element content was discovered for Cr-Ba, Mn-Ba, P-Ba, Sr-Ba, Sr-Ca, Zn-Ca, Mn-Cr, Pb-Cr, Sr-Cr, Mg-Fe, P-Fe, Pb-Ni, Ti-Ni and Sr-P pairs of elements.


Assuntos
Fascia Lata/química , Minerais/metabolismo , Preservação de Tecido/métodos , Oligoelementos/análise , Congelamento , Humanos , Micro-Ondas , Ácido Nítrico/química , Reprodutibilidade dos Testes , Espectrofotometria Atômica/métodos
16.
J Mol Graph Model ; 86: 256-263, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30415121

RESUMO

Hydrates of HCl, HNO3 and H2SO4 involved in polar stratospheric clouds capture the attention of researchers due to the mixtures composed with them. The molecular aggregates generated with these strong acids show different behaviors, geometries and nucleation reactions at atmospheric temperatures. Here is presented a systematic ab initio optimization study of monohydrates of HCl•HNO3•H2SO4 using the Density Functional Theory, by means of geometry optimizations carried out with B3LYP hybrid method and aug-cc-pVTZ basis set, a high level of theory, within Gaussian 09 program. This systematic optimization procedure consists to situate systematically the H2O molecule around the cluster in study, on the favorable positions to develop higher quantity of hydrogen bonds as possible, in order to obtain major quantity of different electronic structures of these monohydrates. Applying this systematic optimization methodology over previously optimized complexes of HCl, HNO3 and H2SO4, the present theoretical approach provides thirty-two different optimized electronic structures of monohydrates that were yielded from seven initial groups of (HCl•HNO3•H2SO4)-complex, placing the H2O in eight positions around them. Moreover, their Infrared spectra have been predicted for all (HCl•HNO3•H2SO4)-monohydrates achieved. Likewise, It is shown the outcomes of the electronic energies, relative Gibbs free energies, Infrared spectra, the wavenumbers of hydrogen bonds, inter-monomeric parameters, electronic structures of (HCl•HNO3•H2SO4)-monohydrates. These monohydrates could be considered precursors of the atmospheric heterogeneous nucleation reactions. These results can be useful to experimentalists of Catalysis, Astrophysics, Corrosion of metals and ceramics, aromatic compounds reactions, even environmental pollution and industrial smog.


Assuntos
Ácido Clorídrico/química , Modelos Químicos , Ácido Nítrico/química , Ácidos Sulfúricos/química , Algoritmos , Ligações de Hidrogênio , Modelos Moleculares , Estrutura Molecular
17.
Chemosphere ; 220: 514-522, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30594804

RESUMO

This study aim to explore an effective approach of persulfate (PS) activation based on multi-walled carbon nanotubes (CNTs) for the phenol degradation. The nitric acid/annealing modified CNTs were obtained by oxidation with concentrated nitric acid followed by annealing at various high temperatures (400-1000 °C). The modified CNTs catalysts were characterized and their catalytic degradation performances of phenol with PS were investigated. The results reveal that the modified CNTs can obviously enhance the phenol removal. The catalytic activity is improved by nitric acid modification and obviously influenced by the annealing temperature. PS concentration and solution pH could also affect the catalytic degradation of phenol. The mechanism of enhanced PS activation by the nitric acid/annealing modified CNTs was proposed that the nitric acid modification resulted in more defective edges and oxygen-containing groups, and subsequent annealing at high temperate facilitated the conversion of sp3 to sp2 carbon, then the catalytic activity for PS activation was enhanced by the active sites of CO group and sp2-hybridized carbon at the defective edges. In addition, a non-radical process of phenol degradation was demonstrated in terms of the radical quenching tests and electron paramagnetic resonance (EPR) spectra analyses. It is suggested that 1O2 is likely the main reactive specie generated in PS activation by the modified CNTs for the phenol removal.


Assuntos
Nanotubos de Carbono/química , Ácido Nítrico/química , Fenol/química , Sulfatos/química , Catálise , Oxirredução
18.
Phys Med ; 55: 116-126, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30473059

RESUMO

PURPOSE: In recent years the use of 68Ga (t1/2 = 67.84 min, ß+: 88.88%) for the labelling of different PET radiopharmaceuticals has significantly increased. This work aims to evaluate the feasibility of the production of 68Ga via the 68Zn(p,n)68Ga reaction by proton irradiation of an enriched zinc solution, using a biomedical cyclotron, in order to satisfy its increasing demand. METHODS: Irradiations of 1.7 Msolution of 68Zn(NO3)2 in 0.2 N HNO3 were conducted with a GE PETtrace cyclotron using a slightly modified version of the liquid target used for the production of fluorine-18. The proton beam energy was degraded to 12 MeV, in order to minimize the production of 67Ga through the68Zn(p,2n)67Ga reaction. The product's activity was measured using a calibrated activity meter and a High Purity Germanium gamma-ray detector. RESULTS: The saturation yield of68Ga amounts to (330 ±â€¯20) MBq/µA, corresponding to a produced activity of68Ga at the EOB of (4.3 ±â€¯0.3) GBq in a typical production run at 46 µA for 32 min. The radionuclidic purity of the68Ga in the final product, after the separation, is within the limits of the European Pharmacopoeia (>99.9%) up to 3 h after the EOB. Radiochemical separation up to a yield not lower than 75% was obtained using an automated purification module. The enriched material recovery efficiency resulted higher than 80-90%. CONCLUSIONS: In summary, this approach provides clinically relevant amounts of68Ga by cyclotron irradiation of a liquid target, as a competitive alternative to the current production through the68Ge/68Ga generators.


Assuntos
Ciclotrons , Radioisótopos de Gálio/química , Radioquímica/instrumentação , Ácido Nítrico/química , Prótons , Isótopos de Zinco/química
19.
Water Sci Technol ; 78(7): 1489-1498, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30427789

RESUMO

The authors used a nitric acid (HNO3)-sodium dodecyl benzene sulfonate (SDBS) method to modify a lignite-based activated carbon. These modified carbons were appraised for their removal of Cd(II) from aqueous solutions. Response surface methodology was employed to optimize the preparation factors including nitric acid concentration CN, temperature T and SDBS concentration CS. Statistical analysis indicated that the interaction of CN and CS incurred the most effect on the maximum cadmium adsorption capacity (Qm). The optimal Qm appeared at CN = 3.29 mol/L, T = 76 °C and CS=30,700 mg/L. The optimal protocol achieved 44.21 mg/g Qm for Cd(II) which was about 7 times larger than for this pristine lignite activated carbon (LAC) (6.78 mg/g). The physical-chemical properties of the modified activated carbons following each synthesis step were characterized relative to their surface area, oxygen functionality, and external surface charge. It was confirmed that the developed surface area, functional groups and negative charges were mainly responsible for the higher adsorption capacity for the LAC that have been more favorably tailored by this HNO3-SDBS protocol.


Assuntos
Cádmio/análise , Ácido Nítrico/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/análise , Adsorção , Carbono , Concentração de Íons de Hidrogênio , Tensoativos/química , Águas Residuárias
20.
Sci Rep ; 8(1): 14293, 2018 09 24.
Artigo em Inglês | MEDLINE | ID: mdl-30250221

RESUMO

In this article, the thermal-treated sericite was modified by both fluorosilicate and the combination of fluorosilicate and nitric acid in order to reduce its layer charge and gain cation exchange capabilities for the preparation of sericite/polymer nanocomposites. After several orthogonal experiments and single factor experiments, the optimal experimental conditions were set up and we found that the combination of nitric acid and fluorosilicate is much more effective than fluorosilicate alone. Chemical composition analysis showed Al3+ was dissolved out from sericite and the dissolving amount is 65 mg/g under optimal experimental conditions. Combining the NMR test, it is considered that the Si/Al ratio in the tetrasheet of the modified product increased from 3.48 to 10. The layer charge reduced and the CEC value increased after fluorosilicate modification, which means the modified sericite is a promising matrix for clay-polymer nanocomposites.


Assuntos
Fluoretos/química , Silicatos/química , Dióxido de Silício/química , Temperatura Ambiente , Cristalização , Íons , Espectroscopia de Ressonância Magnética , Ácido Nítrico/química , Soluções , Eletricidade Estática , Difração de Raios X
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