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1.
Carbohydr Res ; 488: 107910, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31968295

RESUMO

This work presents a kinetic investigation of dilute sulfuric acid hydrolysis of bleached hardwood kraft pulp. The temperature-time dependence shows fast xylose extraction during the initial period of the process, while the glucose content increases slowly and permanently over the period. A conversion of xylose into furfural and furfural-derived chromophores is observed. It is established that only a low-brightness microcrystalline cellulose when a degree of polymerization below 300 can be obtained from hardwood pulp. The study of the acid hydrolysis kinetics, with respect to the degree of polymerization of microcrystalline cellulose, shows that the modified Prout-Tompkins equation describes most adequately the process. According to that kinetic model, the hydrolysis rate depends on a combination of chemical interaction and diffusion processes. It is evident that the activation energy does not change in the course of the process, i.e. the cellulose active centers do not change their activity.


Assuntos
Celulose/química , Ácidos Sulfúricos/química , Madeira/química , Cromatografia Líquida de Alta Pressão , Glucose/química , Hidrólise , Cinética , Xilose/química
2.
Chemosphere ; 243: 125331, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31995863

RESUMO

The effects of reaction temperature, residence time, sulfuric acid and potassium hydroxide on the total concentration and speciation of N and P, potentially toxic elements (salts and metal elements) of pig manure during its hydrothermal carbonization (HTC) were investigated. Concentrations of Cl, K, Na and Mg in the hydrochars were much lower but total N, P and nitrate-nitrogen (NO3--N) contents were significantly higher than in untreated pig manure. The acid-extractable fractions of Cu and Zn in hydrochars were 0.03-0.63 and 0.17-0.66 times lower than those in pig manure and decreased significantly with increasing reaction temperature. The addition of sulfuric acid (H2SO4) or potassium hydroxide (KOH) in HTC reduced the contents of P, Ca, Mg, Cl and heavy metal elements (HMEs) in hydrochars, and the removal rates of Cu and Zn were up to 55% and 59%, respectively. Overall, the rapid treatment of pig manure by HTC reduced the harm of salts and HMEs, and effectively recovered the nutrients in pig manure. The HTC under alkaline conditions was desirable for optimizing the main elemental composition of the hydrochars.


Assuntos
Esterco , Eliminação de Resíduos Líquidos/métodos , Animais , Carbono , Hidróxidos/química , Esterco/análise , Metais Pesados/análise , Minerais/análise , Nitrogênio/análise , Fósforo/química , Compostos de Potássio/química , Ácidos Sulfúricos/química , Suínos , Temperatura , Fatores de Tempo
3.
Eur J Med Chem ; 186: 111894, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31787361

RESUMO

Green chemistry is becoming the favored approach to preparing drug molecules in pharmaceutical industry. Herein, we developed a clean and efficient method to synthesize 3-benzoylquinoxalines via activated carbon promoted aerobic benzylic oxidation under "on-water" condition. Moreover, biological studies with this class of compounds reveal an antiproliferative profile. Further structure modifications are performed and the investigations exhibited that the most active 12a could inhibit the microtubule polymerization by binding to tubulin and thus induce multipolar mitosis, G2/M phase arrest, and apoptosis of cancer cells. In addition, molecular docking studies allow the rationalization of the pharmacodynamic properties observed. Our systematic studies provide not only guidance for applications of O2/AC/H2O system, but also a new scaffold targeting tubulin for antitumor agent discovery.


Assuntos
Antineoplásicos/farmacologia , Compostos de Benzil/química , Quinoxalinas/farmacologia , Tubulina (Proteína)/metabolismo , Antineoplásicos/síntese química , Antineoplásicos/química , Carbono/química , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Relação Dose-Resposta a Droga , Ensaios de Seleção de Medicamentos Antitumorais , Formiatos/química , Humanos , Modelos Moleculares , Estrutura Molecular , Oxirredução , Polimerização/efeitos dos fármacos , Quinoxalinas/síntese química , Quinoxalinas/química , Relação Estrutura-Atividade , Ácidos Sulfúricos/química , Ácido Trifluoracético/química
4.
Chemosphere ; 243: 125323, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31739252

RESUMO

Amines are important atmospheric nucleation precursors in polluted areas. However, specific roles of various amines in enhancing the stability of pre-nucleation clusters are poorly understood. Herein, different roles of trimethylamine (TMA) and monoethanolamine (MEA) in the formation of sulfuric acid (SA)-based pre-nucleation clusters were investigated. The hydration effects of up to four water (W) molecules on the interaction of the acid-base pairs of (TMA)(SA) and (MEA)(SA) were computationally investigated at the M06-2X/6-311++G (3df, 3pd) level of theory. Results show that the formation thermodynamics of key intermediate clusters are different with amines. Besides, MEA-enhanced formation of pre-nucleation clusters plays an important role in environments with high humidity while TMA may be the dominant nucleation precursors in dry conditions. The concentration of dominant MEA-containing pre-nucleation cluster is at least three orders of magnitude higher than that of TMA and dimethylamine near emission sources at conditions of T = 298.15 K and RH = 60%, indicating that alkanolamine may play an important role in atmospheric nucleation. Furthermore, the hydration of MEA is easier than that of alkylamines. Our results put forward the need to distinguish the performance of different types of amine under specific conditions to better model the new particle formation events in highly polluted areas. Besides, this study indicates that alkanolamines such as MEA are important participator in new particle formation.


Assuntos
Aminas/química , Modelos Químicos , Atmosfera/química , Dimetilaminas , Modelos Teóricos , Ácidos Sulfúricos/química , Termodinâmica , Água
5.
Chemosphere ; 239: 124737, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31493755

RESUMO

Antibiotics are of concern due to their prevalent detection in aquatic environment. Sulfate radical based advanced oxidation processes show a great capacity to degrade antibiotics, but the mechanisms are still unclear. In this work, the degradation mechanism of fluoroquinolones (FQs), a major group of antibiotics, in UV/Fe2+/PMS was deeply investigated. The degradation process was in-situ and real-time monitoring by illumination-assisted droplet spray ionization mass spectrometry. A series of reactive intermediates were captured, and further characterized by high-resolution mass spectrometry (HRMS) and tandem MS. About 50 different transformation products have been identified for ciprofloxacin and norfloxacin. More than 15 products were the first time reported. Taking into consideration of the sequential formation and intensity change of intermediates, the feasible and complete transformation pathways of FQs were proposed. Compared with the photolysis process, the defluorination of FQs was not observed in this system. This work provided abundant information of FQs degradation by persulfate advanced oxidation processes (AOPs) and meanwhile demonstrated the importance of HRMS and on-line MS in mechanism research of AOPs.


Assuntos
Antibacterianos/química , Fluoroquinolonas/química , Peróxidos/química , Sulfatos/química , Ciprofloxacino/química , Ferro/química , Espectrometria de Massas , Norfloxacino/química , Oxirredução , Fotólise , Ácidos Sulfúricos/química , Raios Ultravioleta , Poluentes Químicos da Água/química
6.
Chemosphere ; 239: 124724, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31505447

RESUMO

Combination of sulfuric acid modified bagasse activated carbon-bone biochar beads and Acinetobacter indicus screened from petroleum contaminated soil was the best condition for gaseous methyl tert-butyl ether (MTBE) removal. It was found that H2SO4 modified bagasse AC in powder form had higher adsorption capacity (989.33 mg g-1) than that in bead form (1.94 mg g-1). In addition, bone biochar in powder form (3.51 mg g-1) also had higher adsorption capacity than that in bead form (1.63 mg g-1). This was the fact that material beads contained high moisture content that inhibited the penetration of gaseous MTBE into the material. And a mixed material of H2SO4 modified bagasse AC-bone biochar beads had the highest adsorption capacity (2.22 mg g-1) compared to individual H2SO4 modified bagasse AC beads (1.94 mg g-1) and bone biochar beads (1.63 mg g-1) due to a mixed material had more rough surface and high surface area on its material. So, gaseous MTBE can penetrate through this material more easily. Although the maximum adsorption capacity of H2SO4 modified bagasse AC in powder form was the highest but microorganism cannot sustain and survive in this form for a long time. Therefore, the material beads were more suitable for microorganism to grow and degrade gaseous MTBE. Microorganism can degrade MTBE and caused no secondary wastes. Moreover, A. indicus was a novel strain for MTBE removal that has not been previously reported. Therefore, a combination of A. indicus-mixed material beads was a good choice for MTBE removal in a biofilter system.


Assuntos
Acinetobacter/metabolismo , Celulose/química , Carvão Vegetal/química , Éteres Metílicos/química , Acinetobacter/isolamento & purificação , Adsorção , Biodegradação Ambiental , Células Imobilizadas , Poluição Ambiental , Gases , Éteres Metílicos/isolamento & purificação , Éteres Metílicos/metabolismo , Petróleo , Microbiologia do Solo , Ácidos Sulfúricos/química , Gerenciamento de Resíduos/métodos
7.
Chemosphere ; 238: 124598, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31446276

RESUMO

Sewage sludge dewatering is an efficient approach to reduce the volume of sludge for the subsequent disposal. In this study, a novel one-step acidification sludge dewatering method was developed with using oxalic acid as a conditioner. In laboratory-scale experiments with the dosage of 200 mg/g dry solid (DS), the normalized capillary suction time and the specific resistance to filtration were respectively decreased by 78.7% and 60.0% after 30 min of oxalic acid conditioning, much more efficient than those conditioned with sulfuric acid and hydrochloric acid at the same pH value. This superior dewatering performance was attributed to two factors. One was that oxalic acid could more efficiently promote the hydrolysis of polysaccharide, especially pectins, to release bound water. The other was that OA could dissolve more Fe3+ and Al3+, as well as form precipitate with Ca2+ in sludge, which may act as flocculants or co-precipitator for the subsequent sludge particles coagulation. In pilot-scale experiments, the water content of oxalic acid conditioned sludge cake was reduced to 60% under the optimum conditions, while the reagent cost was as low as 110.0 USD/t DS. This work provides a cost-effective and easy-operated sewage sludge disposal technique, and also sheds light on the potential of oxalic acid in environmental waste treatment.


Assuntos
Dessecação/métodos , Ácido Oxálico/química , Esgotos/química , Eliminação de Resíduos Líquidos/métodos , Filtração , Floculação , Ácido Clorídrico/química , Concentração de Íons de Hidrogênio , Hidrólise , Polissacarídeos/metabolismo , Ácidos Sulfúricos/química , Água/química
8.
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
9.
Chemosphere ; 245: 125554, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31874321

RESUMO

A recent quantitative measurement of rates of new particle formation (NPF) in urban Shanghai showed that the high rates of NPF can be largely attributed to the sulfuric acid (SA)-dimethylamine (DMA) nucleation due to relatively high DMA concentration in urban atmosphere (Yao et al., Science. 2018, 361, 278). In certain atmospheric conditions, the release of DMA is accompanied with the emission of high concentration of ammonia. As a result, the ammonia (A) may participate in SA-DMA-based NPF. However, the main sources of DMA and A can be different, thereby leading to different mechanism for the SA-DMA-A-based nucleation under different atmospheric conditions. Near industrial sources with relatively high DMA concentration of 108 molecules cm-3, the contribution of binary SA-DMA nucleation to cluster formation is 61% at 278 K, representing a dominant pathway for NPF. However, in the region not too close to major source of DMA emission, e.g., near agriculture farmland, the routes involving ternary SA-DMA-A nucleation make a 64% contribution at 278 K with DMA concentration of 107 molecules cm-3, showing that A has marked impact on the cluster formation. Under such a condition, we predict that coexisting DMA and A could be detected in the process of NPF. Moreover, at winter temperatures or at higher altitudes, our calculations suggest that the clustering of initial clusters likely involve ternary SA-DMA-A clusters rather than binary SA-DMA clusters. These new insights may be helpful to analyze and predict atmospheric-condition-dependent NFP in either urban or rural regions and/or in different season of the year.


Assuntos
Poluentes Atmosféricos/química , Atmosfera/química , Dimetilaminas/química , Modelos Químicos , Ácidos Sulfúricos/química , Amônia , China , Clima , Temperatura
10.
Carbohydr Polym ; 229: 115539, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31826480

RESUMO

Cellulose nanocrystals with cellulose I and II allomorphs (CNC-I and CNC-II) were prepared from eucalyptus cellulose I substrate by controlling the sulfuric acid hydrolysis conditions, including acid concentration (56-64 wt%), reaction temperature (45 or 60 °C) and time (10-120 min). The crystalline structures were verified by XRD and 13C-NMR. CNC-II only appeared at very restricted reaction conditions. The rapid cellulose supramolecular structure transition under sulfuric acid concentration of around 60 wt% resulted in an abrupt change in CNC yield. A maximal CNC yield of 66.7% was obtained at acid concentration of 58 wt% and reaction temperature of 60 °C. CNC-I exhibited spindle-shape, while CNC-II showed a twisted strip structure. The state of order in cellulose during the acid hydrolysis process has been studied using a coagulation method. A tentative model of CNC-I and CNC-II formation was then proposed. This work provided significant knowledge for the production of CNCs with high yield and controllable allomorph.


Assuntos
Celulose/química , Nanopartículas/química , Ácidos Sulfúricos/química , Eucalyptus/metabolismo , Ligação de Hidrogênio , Hidrólise , Temperatura , Difração de Raios X
11.
J Pharm Pharmacol ; 71(12): 1784-1791, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31579947

RESUMO

The alkylaminoalkanethiosulfuric acids (AAATs) are amphipathic compounds effective against experimental schistosomiasis, of low toxicity, elevated bioavailability after a single oral dose and prompt tissue absorption. OBJECTIVES: To explore the in-vitro antileishmanial potential of AAATs using five compounds of this series against Leishmania (Viannia) braziliensis. METHODS: Their effects on promastigotes and axenic amastigotes, and cytotoxicity to macrophages were tested by the MTT method, and on Leishmania-infected macrophages by Giemsa stain. Effects on the mitochondrial membrane potential of promastigotes and axenic amastigotes and DNA of intracellular amastigotes were tested using JC-1 and TUNEL assays, respectively. KEY FINDINGS: The 2-(isopropylamino)-1-octanethiosulfuric acid (I) and 2-(sec-butylamino)-1-octanethiosulfuric acid (II) exhibit activity against both promastigotes and intracellular amastigotes (IC50 25-35 µm), being more toxic to intracellular parasites than to the host cell. Compound I induced a loss of viability of axenic amastigotes, significantly reduced (30%) the mitochondrial membrane potential of both promastigotes and axenic amastigotes and promoted selective DNA fragmentation of the nucleus and kinetoplast of intracellular amastigotes. CONCLUSIONS: In this previously unpublished study of trypanosomatids, it is shown that AAATs could also exhibit selective antileishmanial activity, a new possibility to be investigated in oral treatment of leishmaniasis.


Assuntos
Antiprotozoários/farmacologia , Leishmania braziliensis/isolamento & purificação , Leishmaniose/tratamento farmacológico , Ácidos Sulfúricos/farmacologia , Administração Oral , Animais , Antiprotozoários/administração & dosagem , Antiprotozoários/química , Concentração Inibidora 50 , Leishmania braziliensis/efeitos dos fármacos , Potencial da Membrana Mitocondrial/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos BALB C , Relação Estrutura-Atividade , Ácidos Sulfúricos/administração & dosagem , Ácidos Sulfúricos/química
12.
Sensors (Basel) ; 19(19)2019 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-31569329

RESUMO

There is a growing desire for wearable sensors in health applications. Fibers are inherently flexible and as such can be used as the electrodes of flexible sensors. Fiber-based electrodes are an ideal format to allow incorporation into fabrics and clothing and for use in wearable devices. Electrically conducting fibers were produced from a dispersion of poly (3,4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT: PSS). Fibers were wet spun from two PEDOT: PSS sources, in three fiber diameters. The effect of three different chemical treatments on the fibers were investigated and compared. Short 5 min treatment times with dimethyl sulfoxide (DMSO) on 20 µm fibers produced from Clevios PH1000 were found to produce the best overall treatment. Up to a six-fold increase in electrical conductivity was achieved, reaching 800 S cm-1, with no loss of mechanical strength (150 MPa). With a pH-sensitive polyaniline coating, these fibers displayed a Nernstian response across a pH range of 3.0 to 7.0, which covers the physiologically critical pH range for skin. These results provide opportunities for future wearable, fiber-based sensors including real-time, on-body pH sensing to monitor skin disease.


Assuntos
Técnicas Eletroquímicas/instrumentação , Eletrodos , Poliestirenos/química , Solventes/química , Tiofenos/química , Dispositivos Eletrônicos Vestíveis , Dimetil Sulfóxido/química , Condutividade Elétrica , Técnicas Eletroquímicas/métodos , Formiatos/química , Concentração de Íons de Hidrogênio , Análise Espectral Raman , Ácidos Sulfúricos/química , Resistência à Tração
13.
J Chromatogr A ; 1605: 460371, 2019 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-31375330

RESUMO

The genus Primula (Primulaceae) comprises species with high medicinal as well as ornamental values. Plants belonging to this genus are well recognized for their richness in bioactive constituents. The huge variety of secondary metabolites make their complete analysis impossible. In order to cope with this challenge, effect-directed analysis (EDA) via HPTLC coupled to structure elucidation techniques was applied on Primula species for the first time. As straightforward non-target bioanalytical technique, HPTLC-UV/Vis/FLD-EDA-ESI-HRMS hyphenates three different orthogonal dimensions, i.e. chromatography with spectrometric detection, biological/enzymatic assays and HRMS. The bioactive metabolites were determined in the middle polar extracts of two Primula species, P. veris (flower) and P. boveana (leaf). The bioactivity profiling comprised the antibacterial activity against Aliivibrio fischeri and Bacillus subtilis bacterial strains and acetyl-/butyrylcholinesterase (AChE/BChE) inhibition assays. The compounds were characterized and identified via their recorded spectral data (HRMS and 1H NMR). The results showed that linoleic and linolenic acids were the principle bioactive compounds present in the studied P. veris flower extract. In the P. boveana leaf extract, flavone, 2'-methoxy-, 2'-hydroxy- and 5,6,2',6'-tetramethoxyflavone (zapotin) were determined as active metabolites. The identification of zapotin, which was previously undescribed in the investigated plant, was considered as the strength of the straightforward non-target bioanalytical technique. Flavone turned out to be the highest potent metabolite, and at the same time, a multipotent compound referring to its various bioactivities discovered. An equivalency calculation of the HPTLC-AChE inhibition by flavone was performed with reference to the well-known inhibitor rivastigmine. As a result, the amount of flavone contained in 10.0 µg dry powder of P. boveana (corresponding to 0.1 µL extract) inhibited as strong as 4.5 µg rivastigmine. In other words, the flavone contained in P. boveana leaf extract powder turned out to be half as strong as the well-known AChE inhibitor rivastigmine.


Assuntos
Cromatografia em Camada Delgada/métodos , Flores/metabolismo , Metaboloma , Extratos Vegetais/metabolismo , Primula/metabolismo , Antibacterianos/análise , Antibacterianos/química , Antibacterianos/farmacologia , Bactérias/efeitos dos fármacos , Benzaldeídos/química , Inibidores da Colinesterase/análise , Inibidores da Colinesterase/farmacologia , Indicadores e Reagentes , Espectroscopia de Prótons por Ressonância Magnética , Ácidos Sulfúricos/química
14.
Molecules ; 24(11)2019 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-31185655

RESUMO

The health claims of olive oil represent an important marketing lever in raising the willingness to pay for a product, but world producers of extra virgin olive oil (EVOO) do not take advantage of it because there are still obstacles to their use. Among these, one issue is the lack of an official method for determination of all free and linked forms derived from secoiridoidic structures of hydroxytyrosol and tyrosol. In this study, different acidic hydrolytic procedures for analyzing the linked forms were tested. The best method was validated and then applied to more than 100 EVOOs. The content of oleuropein and ligstroside derivatives in EVOOs was indirectly evaluated comparing the amount of phenols before and after hydrolysis. After acidic hydrolysis, a high content of total tyrosol was found in most of the EVOOs. The use of a suitable corrective factor for the evaluation of hydroxytyrosol allows an accurate determination only using pure tyrosol as a standard. Further knowledge on the concentration of total hydroxytyrosol will assist in forecasting the resistance of oils against aging, its antioxidant potential and to better control its quality over time.


Assuntos
Formiatos/química , Azeite de Oliva/química , Álcool Feniletílico/análogos & derivados , Polifenóis/química , Ácidos Sulfúricos/química , Hidrólise , Itália , Álcool Feniletílico/análise , Álcool Feniletílico/química , Padrões de Referência
15.
Environ Sci Pollut Res Int ; 26(20): 20308-20315, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31093918

RESUMO

In order to study the radon release behavior when heap leaching uranium ores with dilute sulfuric acid, unleached uranium ores from a uranium mine in southern China were selected as test samples. Adopting parameters from leaching processes commonly used in uranium mines, a laboratory experiment was carried out for 21 days with a one-dimensional acid heap leaching experimental column. The surface radon exhalation rate of uranium ore column was determined by static accumulation method while spraying with deionized water and dilute sulfuric acid. The uranium leaching rate and ore column height for all 21 days of the experiment were also measured. The results show that (1) when sprayed with a leaching agent, the surface radon exhalation rate of uranium ore column initially increased with time sharply. After a maximum value was reached, the rate gradually decreased and stabilized. When the spraying stopped, the surface radon exhalation rate of uranium ore column initially decreased, before increasing until it tended to stabilize. (2) During the entirety of the 21-day leaching experiment, the cumulative leaching rate of uranium increased gradually with time. On the other hand, the surface radon exhalation rate of uranium ore column fluctuated, but the leaching of uranium from uranium ores had almost no effect on the radon exhalation rate. (3) There was no linear correlation between the surface radon exhalation rate and the residual height of ore column during leaching, but the collapsing event of ore column was the direct inducing factor of the fluctuation of surface radon exhalation rate.


Assuntos
Mineração , Radônio/análise , Ácidos Sulfúricos/química , Urânio/química , China , Humanos , Exposição Ocupacional , Radônio/química , Poluentes Radioativos do Solo/análise , Água/química
16.
Carbohydr Polym ; 216: 167-179, 2019 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-31047053

RESUMO

In this paper, acid-catalyzed conversion of nine sugars (xylose, glucose, fructose, galactose, sucrose, maltose, lactose, raffinose, and ß-cyclodextrin) with different sizes, steric structures and functionalities were investigated and impacts of the varied sugars on structures of resulting polymers were focused. Under similar reaction conditions, the yields of the carbon materials (insoluble polymers) formed followed the order: xylose ¼ lactose > galactose > ß-cyclodextrin > maltose > sucrose > fructose > glucose > raffinose. Increasing temperature enhanced transformation of soluble oligomers into insoluble ones. Morphologies of the carbon materials were closely related to sugar structures. Diameters of carbon materials (microsphere form) obtained from the disaccharides and oligosaccharides were larger than that of monosaccharides. Furthermore, the microspheres from oligosaccharides had a higher affinity to each other, resulting from continued polymerization as some reactive functionalities were retained in carbon materials. In addition, graphite structure was formed in the carbon materials, even at 160 °C.


Assuntos
Monossacarídeos/química , Oligossacarídeos/química , Polímeros/química , beta-Ciclodextrinas/química , Catálise , Hidrólise , Microesferas , Estrutura Molecular , Polímeros/síntese química , Solubilidade , Ácidos Sulfúricos/química , Temperatura
17.
Biomolecules ; 9(5)2019 05 08.
Artigo em Inglês | MEDLINE | ID: mdl-31072043

RESUMO

In this paper, a nanocomposite of cuprous oxide and electrochemically reduced graphene oxide (Cu2O‒ERGO) was prepared by a simple and low-cost method; hereby, a new method for the electrochemical determination of tryptophan (Trp) by this composite modified glassy carbon electrode (GCE) is proposed. The prepared materials and modified electrodes were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and cyclic voltammetry (CV). The results showed that Cu2O‒ERGO/GCE had good electrocatalytic activity for Trp. The effects of supporting electrolyte, scanning rate, accumulation potential, and accumulation time on the determination of Trp were studied. Under the optimum experimental conditions, Trp was quantitatively analyzed by square-wave voltammetry (SWV). The oxidation peak current of Trp had a good linear relationship with its concentration in the range of 0.02‒20 µM, and the detection limit was 0.01 µM (S/N = 3). In addition, the modified electrode has high sensitivity, good repeatability, and long-term stability. Finally, the proposed method has been successfully applied in the determination of Trp concentration in practical samples.


Assuntos
Cobre/química , Eletroquímica/métodos , Grafite/química , Nanocompostos/química , Nanopartículas/química , Triptofano/análise , Calibragem , Eletrodos , Humanos , Limite de Detecção , Nanopartículas/ultraestrutura , Oxirredução , Reprodutibilidade dos Testes , Ácidos Sulfúricos/química , Triptofano/sangue , Difração de Raios X
18.
J Environ Sci Health B ; 54(6): 514-524, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31014207

RESUMO

Humans and animals can be exposed to mixtures of chemicals from food and water, especially during disasters such as extended droughts, hurricanes and floods. Drought stress facilitates the occurrence of mycotoxins such as aflatoxins B1 (AfB1) and zearalenone (ZEN), while hurricanes and floods can mobilize toxic soil and sediments containing important pesticides (such as glyphosate). To address this problem in food, feed and water, we developed broad-acting, clay-based enterosorbents that can reduce toxin exposures when included in the diet. In this study, we processed sodium and calcium montmorillonite clays with high concentrations of sulfuric acid to increase surface areas and porosities, and conducted equilibrium isothermal analyses and dosimetry studies to derive binding parameters and gain insight into: (1) surface capacities and affinities, (2) potential mechanisms of sorption, (3) thermodynamics (enthalpy) of toxin/surface interactions and (4) estimated dose of sorbent required to maintain toxin threshold limits. We have also used a toxin-sensitive living organism (Hydra vulgaris) to predict the safety and efficacy of newly developed sorbents. Our results indicated that acid processed montmorillonites were effective sorbents for AfB1, ZEN and glyphosate, with high capacity and tight binding, and effectively protected hydra against individual toxins, as well as mixtures of mycotoxins.


Assuntos
Bentonita/química , Exposição Ambiental/prevenção & controle , Aflatoxina B1/química , Aflatoxina B1/metabolismo , Aflatoxina B1/toxicidade , Animais , Argila , Desastres , Glicina/análogos & derivados , Glicina/química , Humanos , Hydra/efeitos dos fármacos , Ácidos Sulfúricos/química , Termodinâmica , Água/química , Zearalenona/química , Zearalenona/metabolismo , Zearalenona/toxicidade
19.
Food Chem ; 286: 467-474, 2019 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-30827634

RESUMO

Physicochemical and emulsification properties of dialdehyde starch nanocrystals (DASNCs) and dialdehyde starch nanoparticles (DASNPs) were measured in this study. The starch nanocrystals (SNCs), which are prepared by sulfuric acid hydrolysis, were oxidized by sodium periodate to obtain the DASNCs. The DASNPs were prepared by gelatinization and alcohol precipitation of dialdehyde starch. After oxidization by sodium periodate, the SNCs and SNPs became smaller and more suitable for dispersion. X-ray diffraction results showed that the crystal pattern of the SNCs was preserved after oxidation. However, only a single broad peak at the Bragg angle of the DASNPs was observed. The SNCs and DASNCs can form Pickering emulsions, but the emulsions stabilized by the SNPs and DASNPs could be easily broken. The preparation methods for the two kinds of dialdehyde starch nanoparticles are different, so their structures, properties and applications are different.


Assuntos
Emulsificantes/química , Emulsões/química , Nanopartículas/química , Amido/análogos & derivados , Hidrólise , Oxirredução , Tamanho da Partícula , Ácido Periódico , Amido/química , Amido/farmacologia , Ácidos Sulfúricos/química , Difração de Raios X
20.
SAR QSAR Environ Res ; 30(4): 229-245, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30895805

RESUMO

Persistent organic contaminants in the environment pose an environmental risk due to widespread occurrence and toxic properties. Advanced oxidation processes (AOPs) are treatment methods that have been used to successfully degrade organic contaminants in water, soil, sediments and sludge. Reaction rate constants (k) for peroxy acid treatment of 10 substituted naphthalene compounds were determined. The treatment method utilized acetic acid, hydrogen peroxide and a sulphuric acid catalyst to degrade the polyaromatic structures found in the compounds. Molecular structures of the selected compounds were derived at the B3LYP/6-31G* level of theory. Property-encoded surface translator (PEST) descriptors were calculated from B3LYP/6-31G* optimized structures and were found to have significant levels of correlation with k. Models using minimum local ionization potential (PIP.MIN) and a histogram [bin] of the gradient of the K electronic kinetic energy normal to the isosurface (DKN) were evaluated and found to agree within 10% of experimentally derived values of k in most instances. Results show that a combination of PEST descriptors could be used to predict reactivity by the peroxy-acid process. The PEST technology could prove to be a valuable asset for effective remediation design by predicting reaction outcomes for substituted naphthalene compounds and possibly other hydrophobic organic compounds (HOCs).


Assuntos
Ácido Acético/química , Peróxido de Hidrogênio/química , Naftalenos/química , Ácidos Sulfúricos/química , Catálise , Modelos Moleculares , Oxirredução , Relação Estrutura-Atividade
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