Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 1.738
Filtrar
1.
Chemosphere ; 252: 126639, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32443281

RESUMO

Excess fluoride (F-, >1.5 mg F-/L) in drinking water affects >260 million people across the globe and leads to dental and skeletal fluorosis. In this study, commercially available granular activated carbon (GAC) was modified with 0.3 M citric acid to get citric acid modified GAC (CAGAC). Over 70% of fluoride was removed in the first 60 min by CAGAC, whereas unmodified GAC removed only 30%. There were negligible interferences by co-existing ions (NO3-, Cl-, HCO3-, SO42-, PO43-) and organic matters. Maximum adsorption capacity of CAGAC was two times (1.65 mg/g) that of unmodified GAC (0.88 mg/g). Dubinin-Radushkevich (D-R) isotherm described the experimental data well indicating that ion exchange was involved in fluoride removal. CAGAC worked effectively over a wide range of pH (2-10) even though the point-of-zero-charge (PZC) was 4.89, and so the removal was not controlled by electrostatic interaction alone; surface adsorption and intra-particle diffusion were the rate-determining processes.


Assuntos
Ácido Cítrico/química , Poluentes Químicos da Água/química , Purificação da Água , Adsorção , Carvão Vegetal , Água Potável , Fluoretos , Troca Iônica , Cinética
2.
Bull Environ Contam Toxicol ; 104(5): 658-667, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32322932

RESUMO

The leaching behavior of five additives, including citric acid (CA), wood vinegar (WV), 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), polyaspartic acid (PASP) and FeCl3, was investigated to evaluate the possibility of enhanced phytoextraction of Pennisetum sp. from cadmium-contaminated soil. FeCl3 and CA have the highest leaching potential due to the ability that could convert large amounts of mobile fractions of Cd. The pot experiment showed that HEDP, WV, and PASP treatments could not only significantly increase the biomass of Pennisetum sp., but also maintain high uptake capacity of Cd by activating the stable fractions. HEDP has the highest Cd extraction efficiency and metal extraction ratio (MER) value. The phytoremediation efficiency could be improved mainly by increasing the biomass of the tolerant shoots, and Pennisetum sp. seems to have the maximum potential of phytoextraction to Cd with HEDP which could achieve a higher phytoextraction effect than Cd-hyperaccumulator.


Assuntos
Cádmio/análise , Pennisetum/crescimento & desenvolvimento , Poluentes do Solo/análise , Solo/química , Ácido Acético/química , Biodegradação Ambiental , Biomassa , Cloretos/química , Ácido Cítrico/química , Ácido Etidrônico/química , Compostos Férricos/química , Pennisetum/química , Peptídeos/química
3.
Chemosphere ; 251: 126331, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32145572

RESUMO

The present study deals with the potential application of Purolite S957 and Diphonix Resin® for the removal of rare earth elements from aqueous liquors as a result of the extraction of spent Ni-MH batteries in the presence of citric acid. The effects of the metal ion and the citric acid ratio, pH, ion exchanger dose, contact time, initial concentration and temperature were studied using the batch technique. The Langmuir and Freundlich adsorption isotherm models were used for the description of the adsorption process. The equilibrium adsorption data were fitted using the pseudo first order, pseudo second order, intraparticle diffusion, Boyd, film diffusion and Dumwald-Wagner models. The maximum adsorption capacity q0 obtained from the Langmuir isotherm was found to be 46.63 mg/g for Ni(II) and 60.75 mg/g for La(III) on Purolite S957 as well as 46.55 mg/g for Ni(II) and 60.12 mg/g for La(III) on Diphonix Resin®. The kinetics followed the pseudo second order reaction. Based on the Weber-Morris model the adsorption process proved to proceed in two stages. Based on the Boyd model the rate controlling steps were film and intraparticle diffusions. The adsorption process was spontaneous and endothermic in nature. Reusability of ion exchangers in the desorption studies was also evaluated as a sustainable approach. The physicochemical properties of Purolite S957 and Diphonix Resin® were studied using the ASAP analysis, optical and scanning electron microscopy, potentiometric titration, pHPZC and FT-IR as well as XPS analysis.


Assuntos
Ácido Cítrico/química , Troca Iônica , Metais/química , Poluentes Químicos da Água/química , Adsorção , Difusão , Concentração de Íons de Hidrogênio , Íons , Cinética , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura , Termodinâmica , Poluentes Químicos da Água/análise
4.
Food Chem ; 315: 126217, 2020 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-32007812

RESUMO

This study investigated the direct citric acid hydrolysis extraction method to optimize phytosterols extraction from hickory husk. Single factor experiments followed by a three-level three-factor Box-Behnken experiments were performed. The optimal extraction parameters were determined as: pH of 2.0, liquid-to-solid ratio of 17.12: 1 mL/g, and temperature of 55.81 °C. Practical experiments were carried out in triplicate, and subsequently yielded phytosterols of 912.452 ± 17.452 µg/g DW, in good consistence with the predicted extraction yield of 902.874 µg/g DW. The conductivity of the extract was also found to play effective role under direct citric acid hydrolysis and recorded 36.30 ± 1.08 µs/cm at optimum extraction condition. ß-Sitosterol stigmasterol, campsterol, ergosterol and lupeol were detected as main PSs and triterpenoids in hickory husk using UPLC-Triple-TOF/MS. Finally, the comparison between direct hydrolysis extraction and traditional solvent extraction showed that this new method was more effective and eco-friendlier to extract both free and conjugated phytosterols.


Assuntos
Carya/química , Modelos Teóricos , Fitosteróis/isolamento & purificação , Triterpenos/isolamento & purificação , Ácido Cítrico/química , Ergosterol/química , Ergosterol/isolamento & purificação , Concentração de Íons de Hidrogênio , Hidrólise , Triterpenos Pentacíclicos/química , Triterpenos Pentacíclicos/isolamento & purificação , Fitosteróis/química , Sitosteroides/química , Sitosteroides/isolamento & purificação , Estigmasterol/química , Estigmasterol/isolamento & purificação , Triterpenos/química
5.
Chemosphere ; 248: 126029, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32035385

RESUMO

The use of electrokinetic Fenton (EK Fenton) process, as promising soil remediation approach, was investigated by using an iron electrode with different supporting electrolytes (tap water, H2O2, and citric acid) to depollute soil spiked with petroleum where kaolin was selected as low hydraulic conductivity. The results clearly confirm that, the combination of electrokinetic remediation (EK) and Fenton technologies, is an efficient oxidizing approach for removing hydrocarbons from this kind of soil. In fact, the electrokinetic Fenton reactions and the control of the soil pH conditions by adding citric acid enhanced the oxidation process because the addition of the H2O2 with iron electrode resulted in higher removal efficiencies (89%) for total petroleum hydrocarbons (TPHs). These figures allowed to confirm that EK Fenton process with pH control contributed for the transport of H2O2 and Fe2+ ions in the soil by electromigration and eletro-osmotic phenomena. Conversely, no control of pH conditions when only EK was applied, achieved lower hydrocarbons removal (27%) after 15 d of treatment due to the precipitation of iron ions. Finally, the efficiency of the EK Fenton remediation prevented the generation of secondary effluent with higher organic content, avoiding its treatment by other advanced oxidation process.


Assuntos
Recuperação e Remediação Ambiental/métodos , Poluição por Petróleo , Poluentes do Solo/química , Ácido Cítrico/química , Técnicas Eletroquímicas/instrumentação , Eletrodos , Recuperação e Remediação Ambiental/instrumentação , Hidrocarbonetos/química , Peróxido de Hidrogênio/química , Concentração de Íons de Hidrogênio , Ferro/química , Caulim/química , Osmose , Oxirredução , Solo/química
6.
Food Chem ; 317: 126457, 2020 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-32106009

RESUMO

In this work, a novel, selective and sensitive fluorescent probe (sulfur doped graphene quantum dots, SGQDs) was designed for real-time detection of quercetin in red wine samples. SGQDs were synthesized by pyrolyzing citric acid (CA) and 3-Mercaptopropionic acid (MPA) and characterized through advanced techniques. It was observed that fluorescence intensity of SGQDs could be substantially quenched by the addition of quercetin through inner filter effect (IFE) mechanism. Additionally, a visual color change (colorless to light yellow) was also noticed after addition of quercetin into a solution of SGQDs. The change in SGQDs fluorescence intensity with varying quercetin content revealed good linearity in the 0-50.0 µM range with regression coefficient of 0.9943 and a lowest detection limit of 0.006 µg/mL. To authenticate the real-time application of SGQDs as a potential fluorescent probe, red wine samples having different quercetin concentrations were used for quantitative analysis, after the optimization of several analytical parameters.


Assuntos
Corantes Fluorescentes/química , Pontos Quânticos/química , Quercetina/análise , Enxofre/química , Ácido 3-Mercaptopropiônico/química , Ácido Cítrico/química , Cor , Flavonoides/química , Fluorescência , Análise de Alimentos/métodos , Grafite/química , Concentração de Íons de Hidrogênio , Limite de Detecção , Solventes/química , Espectrometria de Fluorescência/métodos , Vinho/análise
7.
Aquat Toxicol ; 221: 105445, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32078886

RESUMO

Despite the widespread use of nanoparticles (NPs), there are still major gaps of knowledge regarding the impact of nanomaterials in the environment and aquatic animals. The present work aimed to study the effects of 7 and 40 nm gold nanoparticles (AuNPs) - citrate and polyvinylpyrrolidone (PVP) coated - on the liver proteome of the estuarine/marine fish gilthead seabream (Sparus aurata). After 96 h, exposure to AuNP elicited alterations on the abundance of 26 proteins, when compared to the control group. AuNPs differentially affected several metabolic pathways in S. aurata liver cells. Among the affected proteins were those related to cytoskeleton and cell structure, gluconeogenesis, amino acids metabolism and several processes related to protein activity (protein synthesis, catabolism, folding and transport). The increased abundance of proteins associated with energy metabolism (ATP synthase subunit beta), stress response (94 kDa glucose-regulated protein) and cytoskeleton structure (actins and tubulins) may represent the first signs of cellular oxidative stress induced by AuNPs. Although higher gold accumulation was found in the liver of S. aurata exposed to 7 nm PVP-AuNPs, the 7 nm cAuNPs were more bioactive, inducing more effects in liver proteome. Gold accumulated more in the spleen than in the other assessed tissues of S. aurata exposed to AuNPs, highlighting its potential role on the elimination of these NPs.


Assuntos
Ouro/toxicidade , Fígado/efeitos dos fármacos , Nanopartículas Metálicas/toxicidade , Proteoma/metabolismo , Dourada/metabolismo , Poluentes Químicos da Água/toxicidade , Animais , Ácido Cítrico/química , Fígado/metabolismo , Redes e Vias Metabólicas/efeitos dos fármacos , Oxirredução , Estresse Oxidativo/efeitos dos fármacos , Povidona/química , Proteômica , Propriedades de Superfície
8.
Talanta ; 209: 120593, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31892006

RESUMO

The impact of preanalytical sample handling on lipid stability has been assessed in human plasma using targeted LC-MS/MS quantification of endocannabinoids, sphingolipids and LPA, complemented by non-targeted lipidomics screening with LC-QTOFMS. The study involved incubation of whole blood and plasma from healthy volunteers at room temperature or in ice water for time periods ranging from 20 min to 24 h. The impact of two different anticoagulants, K3EDTA and sodium fluoride/citrate, on lipid stability was evaluated. It was found that the concentrations determined for several endogenous lipids vary when whole blood and plasma samples are processed at room temperature, whereas the concentrations of most lipids were stable for 4 h in ice water. Surprisingly, the detected amounts of endocannabinoids 1- and 2-arachidonoyl glycerol and arachidonoyl ethanolamide increased markedly by 60, 95, and 30% in K3EDTA whole blood after storage in ice water for only 20 min. When using sodium fluoride/citrate blood collection tubes, the stability of several lipids, including that of the endocannabinoids, was improved. Accordingly, it is absolutely necessary to keep the blood sampling and plasma processing time below 1 h to avoid ex-vivo formation of endocannabinoids. It is worth mentioning that baseline lipid levels differ when using K3EDTA or sodium fluoride/citrate blood sampling tubes, which emphasizes the importance of traceability of reported plasma concentrations to the used anticoagulant.


Assuntos
Coleta de Amostras Sanguíneas/métodos , Endocanabinoides/sangue , Lipidômica/métodos , Lisofosfolipídeos/sangue , Esfingolipídeos/sangue , Adulto , Cromatografia Líquida/métodos , Ácido Cítrico/química , Feminino , Fluoretos/química , Humanos , Masculino , Espectrometria de Massas/métodos
9.
Nat Commun ; 11(1): 458, 2020 01 23.
Artigo em Inglês | MEDLINE | ID: mdl-31974386

RESUMO

Assembly of the peptidoglycan is crucial in maintaining viability of bacteria and in defining bacterial cell shapes, both of which are important for existence in the ecological niche that the organism occupies. Here, eight crystal structures for a member of the cell-shape-determining class of Campylobacter jejuni, the peptidoglycan peptidase 3 (Pgp3), are reported. Characterization of the turnover chemistry of Pgp3 reveals cell wall D,D-endopeptidase and D,D-carboxypeptidase activities. Catalysis is accompanied by large conformational changes upon peptidoglycan binding, whereby a loop regulates access to the active site. Furthermore, prior hydrolysis of the crosslinked peptide stem from the saccharide backbone of the peptidoglycan on one side is a pre-requisite for its recognition and turnover by Pgp3. These analyses reveal the noncanonical nature of the transformations at the core of the events that define the morphological shape for C. jejuni as an intestinal pathogen.


Assuntos
Campylobacter jejuni/metabolismo , Endopeptidases/química , Endopeptidases/metabolismo , Peptidoglicano/metabolismo , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Domínio Catalítico , Ácido Cítrico/química , Ácido Cítrico/metabolismo , Cristalografia por Raios X , Endopeptidases/genética , Hidrólise , Metaloproteases/química , Modelos Moleculares , Mutação , Peptidoglicano/química , Conformação Proteica , Fatores de Virulência/química
10.
Artigo em Inglês | MEDLINE | ID: mdl-31941097

RESUMO

Adding chelating agents is a critical technique of heavy metal activation for enhancing phytoextraction through the formation of soluble metal complexes which will be more readily available for extraction. The preliminary, dynamic, equilibrium activation experiments and speciation analysis of Pb, Cd and Tl in contaminated red soils were used to select six chelates with relatively good activation performance from nine chelates, and the effects of dosage and pH on the heavy metals activation were studied systematically. Results showed that the activation of Pb, Cd and Tl by chelates reached equilibrium within 2 h, and the activation process showed three stages. Under neutral conditions, chelates had better activation performance on Pb- and Cd-contaminated soils. Except for S,S-ethylenediamine disuccinic acid (S,S-EDDS) and citric acid (CA), the maximum equilibrium activation effect (MEAE) of ethylenediaminetetraacetic acid (EDTA), N,N-bis (carboxymethyl) glutamic acid (GLDA), diethylenetriaminepentaacetic acid (DTPA) and aminotriacetic acid (NTA) was over 81%. The MEAE of Tl-contaminated soil was less than 15%. The decreasing order of the dosage of chelating agents corresponding to MEAE for three types of contaminated soils was Pb-, Cd- and Tl-contaminated soil, relating to the forms of heavy metals, the stability constants of metal-chelates and the activation of non-target elements Fe in red soil. Under acidic conditions, the activation efficiencies of chelates decreased to differing degrees in Pb- and Cd-contaminated soils, whereas the activation efficiencies of chelating agents in Tl-contaminated soils were slightly enhanced.


Assuntos
Cádmio/química , Quelantes/química , Chumbo/química , Poluentes do Solo/química , Tálio/química , Biodegradação Ambiental , Ácido Cítrico/química , Ácido Edético/química , Etilenodiaminas/química , Glutamatos/química , Glicina/análogos & derivados , Glicina/química , Ácido Pentético/química , Solo/química , Succinatos/química
11.
Food Chem ; 310: 125815, 2020 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-31757491

RESUMO

Developing green solvents with low toxicity and low energy consumption is an important issue for edible oil production. In this study, a novel extraction system, specifically a citric acid/citric acid sodium mixture, was developed for oil extraction from seed crops. Peanut and pumpkin seeds were used to evaluate extraction efficiency and more than 70% and 57% oils, respectively, were extracted from peanut and pumpkin seeds at 4 °C. After extraction, the oils floated on the surface of the solution and could be separated from the solvent system without evaporation. The extraction of edible oils was achieved without the use of toxic chemicals or energy-intensive equipment. This study provided a green and efficient method, and showed the potential of the proposed citric acid/citric acid sodium extraction system for production of edible oils from natural sources.


Assuntos
Fracionamento Químico/métodos , Óleos Vegetais/isolamento & purificação , Sementes/química , Solventes/química , Arachis/química , Ácido Cítrico/química , Cucurbita/química , Química Verde , Sódio/química
12.
Chemosphere ; 241: 124960, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31590017

RESUMO

Acidity of aerosol particles plays important roles in atmospheric chemistry, in turn, impacting climate system and public health. Current knowledge of acidity in atmosphere aerosols remains fairly scarce largely because of difficulty in direct measurement. On the other hand, indirect methods for estimating aerosol pH are often inconsistent with pH values predicted by thermodynamic models. Recently, a direct Raman spectroscopy method has been reported to determine pH values of acid-conjugate base equilibria systems based on Raman intensity of distinct characteristic peaks of conjugate acid-base pair. Nevertheless, for pure carboxylic acid aerosol particles, such as malonic acid (MA), characteristic peak of its conjugate base cannot be clearly observed in Raman spectra owing to small Ka value (weak acid dissociation constant), which leads to little dissociation of weak acid and low concentration of its conjugated base. As a result, pH of carboxylic acid particles cannot be directly determined by calibrating concentrations of acid and its conjugated base using the above-mentioned method. To address such an issue, we demonstrate a new approach for determining pH values of malonic acid (MA) and citric acid (CA) droplets under different relative humidity (RH) based on calibration curves. We measure Raman intensity ratios of acid solutions at different concentrations and their pH values to establish a calibration curve, and then using the intensity ratio of MA and CA droplets under different RH to determine aerosol particle pH based on calibration curves. Results have shown that aerosol pH of MA droplet decreases with a decreasing RH and pH values ranges from 1.03 to -0.12, when RH value is reduced from 90% to 26%, in good agreement with model prediction values. In addition, we also, for the first time, report pH values of CA droplets under different RH conditions and its pH values range from 1.13 to -0.74 when RH is reduced from 91% to 28%.


Assuntos
Aerossóis/química , Ácido Cítrico/química , Umidade , Concentração de Íons de Hidrogênio , Malonatos/química , Análise Espectral Raman/métodos , Atmosfera/química , Clima
13.
Chemosphere ; 243: 125327, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31733538

RESUMO

The aim of the present study is to assess the influence of vermi-wash (VW) and citric acid (CA) on Sorghum bicolor growth and phytoaccumulation of lead (Pb) and nickel (Ni) contaminated soil. The biomass of the S. bicolor has been enhanced by the addition of VW (24 and 26%) and CA (11 and 9%) in Pb and Ni contaminated soil, respectively. The VW treatment showed enhanced shoot and root lengths and chlorophyll concentrations compared to CA. The shoot anatomic structure showed an accumulation of Pb and Ni were positively impacted by the amendment of VW and CA. In addition, VW treatment showed enhanced antioxidant enzymes activity (140, 125 and 152 U/mg of CAT, SOD and POD). Further, the plants grown in Pb contaminated soil treated with VW showed enhanced Rubisco activity of 1.49 U/ml, whereas, CA treatment showed 1.23 U/ml of Rubisco. It has been observed that the VW showed as a potential chelator as well as plant beneficial formulation for the enhanced phyto-remediation of Pb and Ni.


Assuntos
Biodegradação Ambiental , Chumbo/metabolismo , Níquel/metabolismo , Poluentes do Solo/metabolismo , Sorghum/metabolismo , Antioxidantes , Biomassa , Quelantes , Clorofila , Ácido Cítrico/química , Chumbo/análise , Níquel/análise , Solo/química , Poluentes do Solo/análise , Sorghum/crescimento & desenvolvimento
14.
Environ Sci Pollut Res Int ; 27(5): 5572-5583, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31853846

RESUMO

This study focused on enhanced electrokinetic remediation of Cr(VI) in real contaminated soil. The citric acid (CA) as the electrolyte and Fe(II) released from zero-valent iron (ZVI) under anoxic conditions functioned as the main reducer. They were used for overcoming the high insoluble Cr(VI) fraction in real contaminated soil and high Cr(VI) residue in acidic soil near the anode simultaneously. The synergism of CA and ZVI is that CA helps the release of Cr(VI) to react with the generated Fe(II) and alleviates the hindrance of Fe and Cr co-precipitates in electromigration of Cr; meanwhile, the end product Fe(III) from ZVI catalyzed the Cr(VI) reduction by CA. The removal of Cr(III) and Cr(VI) was significantly improved in real contaminated soil. The optimum result (82.86%) was obtained at a voltage gradient of 2.5 V/cm after 12-day remediation with a 10 g ZVI dose when the catholyte and anolyte were 0.2 mol/L and 0.1 mol/L CA, respectively. This configuration has a significant improvement in overcoming the current obstacles for Cr(VI) electrokinetic remediation from real contaminated soil and prospects for large-scale practical applications.


Assuntos
Cromo/química , Recuperação e Remediação Ambiental/métodos , Poluentes do Solo , Ácido Cítrico/química , Ferro/química , Solo
15.
Colloids Surf B Biointerfaces ; 185: 110555, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31629095

RESUMO

In this study synthesis of graphene oxide-poly citric acid/MnCe0.5Fe1.5O4 nanoferrofluid with a simple method and its ability for enhancing the contrast of magnetic resonance images was reported. The co-precipitation method has been used for the production of MnCe0.5Fe1.5O4 nanoparticles with a size distribution of 25-40 nm, which has shown a very good superparamagnetic property with saturation magnetization (Ms) 53.6 emu g-1. Graphene oxide (GO) was prepared by a modified Hummers method and polymerized with citric acid to produce GO-PCA. The nanoparticles were loaded on the GO-PCA surface to produce nanoferrofluid that showed excellent colloidal stability, extra dispersibility, and good magnetic properties with Ms equal to 47.8 emu g-1. This nanoferrofluid has an increased effect on the contrast of T2 and T2*-weighted images, with the values 109.15 and 180.23 mM-1 s-1 for r2 and r2*, respectively at 3.0 T. The cellular uptake evaluation revealed adequate uptake for HeLa cell lines.


Assuntos
Grafite/química , Ferro/química , Imagem por Ressonância Magnética , Nanopartículas/química , Polimerização , Ácido Cítrico/química , Meios de Contraste/química , Endocitose , Células HeLa , Humanos , Fenômenos Magnéticos , Nanopartículas/ultraestrutura , Espectrometria por Raios X , Espectroscopia de Infravermelho com Transformada de Fourier
16.
Talanta ; 208: 120409, 2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31816787

RESUMO

A new and simple method for Ni determination in hydrogenated vegetable fat (HVF) has been developed using a RP-DLLME sample preparation procedure for further determination by flame atomic absorption spectrometry (FAAS) and graphite furnace atomic absorption spectrophotometry (GFAAS). The RP-DLLME procedure includes simultaneous microextraction and preconcentration of Ni in HVF, using 5.0 g of HVF preheated (75 °C) and diluted in 5.0 mL of xylene, with the addition of a dispersant/extractant mixture (n-propanol/dilute HNO3). The sample was manually stirred and centrifuged and the aqueous phase was collected for further Ni determination by FAAS and GFAAS. RP-DLLME was carried out using only 700 µL of n-propanol and 300 µL of 2.0 mol L-1 HNO3. The recovery varied from 93.3% to 101.5% for HVF. The LODs and LOQs were 40 and 90 ng g-1 for FAAS, and 0.41 and 1.36 ng g-1 for GFAAS. The proposed analytical method is viable and this is the first application of RP-DLLME to solid fat samples, with Ni determination as an example of application. This method consumes small amounts of reagents, with lower toxicity as compared to microwave decomposition. Furthermore, the key features of the RP-DLLME method include simplicity of operation, high sample mass, reduced reagent consumption, and use of diluted HNO3 as an extractant.


Assuntos
Gorduras na Dieta/análise , Contaminação de Alimentos/análise , Microextração em Fase Líquida/métodos , Níquel/análise , Óleo de Soja/química , Antioxidantes/química , Hidroxitolueno Butilado/química , Ácido Cítrico/química , Hidrogenação , Espectrofotometria Atômica/métodos
17.
Chemosphere ; 240: 124930, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31574440

RESUMO

The adverse industrial activities discharged contaminated wastewater directly into the water bodies that contain toxic substances such as heavy metals. The contours use of marble industrial effluents may affect the fertility of soil and crop growth. The present study was conducted to investigate the toxic effects of marble industrial effluents (M.E) on Zea mays L under the exogenous application of citric acid (CA) with different combinations such as marble industrial effluent (0, 30%, 60%, 100%) diluted with distilled water and CA (10 mM). The results showed significant decrease in the growth of Zea mays with increasing concentration of marble industrial effluent. The maximum reduction in plant height, root length, number of leaves, leaf area and fresh and dry biomass was observed at the application of 100% M.E as compared to control. Similar to growth conditions the photosynthetic machinery and the activities of antioxidant enzymes (Superoxide dismutase (SOD), Peroxidases (POD), Catalases (CAT), Ascorbate peroxidase (APX)) was also decreased with increasing concentration of M.E. The application of CA significantly alleviated the M.E induced toxic effect on Zea mays and ameliorated the growth, biomass, photosynthesis and antioxidant enzymes activities by reducing the production of reactive oxygen species. The C.A application also enhanced the heavy metal content such as chromium (Cr), cadmium (Cd), Zinc (Zn) in different parts of Zea mays. The results concluded that the Zea mays tolerant varieties can be a potential candidate for the M.E irrigated soil and might be suitable for the phyto-extraction of Cr, Cd and Zn.


Assuntos
Folhas de Planta/metabolismo , Poluentes do Solo/análise , Solo/química , Águas Residuárias/química , Purificação da Água/métodos , Zea mays/metabolismo , Antioxidantes/farmacologia , Ascorbato Peroxidases/metabolismo , Biomassa , Cádmio/análise , Catalase/metabolismo , Cromo/análise , Ácido Cítrico/química , Fotossíntese/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Superóxido Dismutase/metabolismo
18.
Chemosphere ; 239: 124706, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31493754

RESUMO

The remediation effect of organic acids in heavy metal contaminated soil was widely studied. However, the comprehensive evaluation of organic acids on micro-ecological environment in heavy metal contaminated soil was less known. Herein, this experiment was conducted to investigate the impact of malic acid, citric acid and oxalic acid on soil fertility, cadmium (Cd) speciation and ecotoxicity in contaminated soil. Especially, to evaluate the ecotoxicity of Cd, high-throughput sequencing was used to investigate the soil bacterial community structure and diversity after incubation with organic acids. The results showed that obvious changes in soil pH were not observed. Whereas, the contents of available phosphorus (Olsen-P) and alkali hydrolysable nitrogen (Alkeline-N) evidently increased with a significant difference. Furthermore, compared to control, the proportion of acetic acid-extractable Cd increased by 3.06-6.63%, 6.11-9.43% and 1.91-6.22% respectively in the groups amended with malic acid, citric acid and oxalic acid, which indicated that citric acid did better in improving the availability of Cd than malic acid and oxalic acid. In terms of biological properties, citric acid did best in bacteria count increase, enzyme activities and bacterial community structure improvement. Accordingly, these results provided a better understanding for the influence of organic acids on the micro-ecological environment in Cd contaminated soil, based on physicochemical and biological analysis.


Assuntos
Cádmio/toxicidade , Ácidos Carboxílicos/farmacologia , Recuperação e Remediação Ambiental/métodos , Microbiologia do Solo , Poluentes do Solo/química , Bactérias/efeitos dos fármacos , Cádmio/análise , Cádmio/química , Ácidos Carboxílicos/química , Ácido Cítrico/química , Ácido Cítrico/farmacologia , Ecotoxicologia , Poluição Ambiental/análise , Malatos/química , Malatos/farmacologia , Ácido Oxálico/química , Ácido Oxálico/farmacologia , Solo/química , Poluentes do Solo/análise
19.
Food Chem ; 306: 125610, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31586816

RESUMO

The industrial implementation of new eco-friendly solvents has highlighted the need to analyse both the structures and thermophysical properties of these solvents. Here, two deep eutectic solvents (DESs) used in the agro-food field were studied: xylitol:choline chloride:water (1:2:3 M ratio), XoCH, and citric acid:choline chloride:water (1:1:6 M ratio), CiCH. The H-bond network between the components of each DES was evaluated and the diffusion coefficients at 298.15 K were calculated using NMR spectroscopy. In addition, seven thermophysical properties were determined from 278.15 to 338.15 K. Also, the solubility of quercetin in water and in the two eutectic mixtures was measured and the interactions between components were studied. NMR experiments revealed the presence of water within the supramolecular structure of XoCH, but CiCH is a "DES-in-water" solution. Based on the results, XoCH is the most compact mixture. Finally, quercetin was remarkably more soluble in the studied DESs than in pure water.


Assuntos
Ácido Cítrico/química , Quercetina/química , Xilitol/química , Colina/química , Solubilidade , Solventes/química , Água/química
20.
Carbohydr Polym ; 227: 115346, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31590873

RESUMO

This study reports excellent supercapacitor performance of hierarchical composite porous carbon (HPC) materials successfully fabricated by one-step carbonization and activation process derived from polysaccharides carboxymethyl cellulose, bacterial cellulose, and citric acid. The resultant HPC displayed unique porous nanosheet morphology with high specific surface area (2490 m2 g-1) and rich oxygen content (7.3%). The developed structures with macropores, mesopore walls, micropores, and high oxygen content led to excellent electrochemical performance for electrode of electric double-layer capacitors (EDLCs). In a three-electrode system, the HPC electrode showed a high specific capacitance of 350 F g-1, good rate performance, and excellent cycling stability. The energy density of supercapacitor based on HPC was comparable to or higher than that of commercially supercapacitors. More importantly, two series-wound devices were easy to light light-emitting diode (LED, 3.0 V). These results suggest that the current material is a promising candidate for low-cost and eco-friendly energy storage devices.


Assuntos
Celulose/química , Ácido Cítrico/química , Capacitância Elétrica , Polissacarídeos Bacterianos/química , Carbono/química , Fontes de Energia Elétrica , Eletrodos , Porosidade
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA