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1.
Chemosphere ; 239: 124670, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31505441

RESUMO

The objectives of this study were to determine the viability of removing Orange II (OII) dye by simulated solar photoelectro-Fenton (SSPEF) and to evaluate the stability of a WO2.72/Vulcan XC72 gas diffusion electrode (GDE) and thus determine its best operating parameters. The GDE cathode was combined with a BDD anode for decolorization and mineralization of 350 mL of 0.26 mM OII by anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF) and photoelectro-Fenton (PEF) at 100, 150 and 200 mA cm-2 and SSPEF at 150 mA cm-2. The GDE showed successful operation for electrogeneration, good reproducibility and low leaching of W. Decolorization and OII decay were directly proportional to the current density (j). AO-H2O2 had a reduced performance that was only half of the SSPEF, PEF and EF treatments. The mineralization efficiency was in the following order: AO-H2O2 < EF < PEF ≈ SSPEF. This showed that the GDE, BDD anode and light radiation combination was advantageous and indicated that the SSPEF process is promising with both a lower cost than using UV lamps and simulating solar photoelectro-Fenton process. The PEF process with the lowest j (100 mA cm-2) showed the best performance-mineralization current efficiency.


Assuntos
Compostos Azo/análise , Benzenossulfonatos/análise , Técnicas Eletroquímicas , Peróxido de Hidrogênio/química , Ferro/química , Poluentes Químicos da Água/análise , Eletrodos , Oxirredução , Reprodutibilidade dos Testes , Luz Solar
2.
Chemosphere ; 238: 124693, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31524627

RESUMO

In this work, self-assembled gels were prepared with exfoliated montmorillonite and chitosan (EMCG) as the adsorbent for removing methyl orange (MO) from water in absence and presence of methylene blue (MB). Several techniques including scanning electron microscope (SEM), zeta potential, fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used for the characterization of the EMCG before and after removal of MO. The EMCG performed well in the removal of MO attributing to the electrostatic attraction, cation exchange and hydrogen bond. The adsorption behaviors were followed pseudo-second-order and Langmuir isotherm. More surprisingly, the maximum adsorption capacity of MO was obviously enhanced in the presence of MB that it increased from 545 mg g-1 (absence of MB) to 1060 mg g-1 with the shielding effect of MB on EMCG which allowed MO and MB to alternately arrange at the adsorption sites. This finding of the synergistic effect between the two dyes on the proposed composite opens up new vistas to imagine the enhanced purification of the wastewater with multiple dyes co-existed using the multifunctional adsorbents.


Assuntos
Compostos Azo/análise , Bentonita/química , Quitosana/química , Azul de Metileno/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Compostos Azo/química , Corantes/química , Géis , Espectroscopia Fotoeletrônica , Espectroscopia de Infravermelho com Transformada de Fourier , Águas Residuárias/química , Poluentes Químicos da Água/química
3.
Chemosphere ; 238: 124692, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31545214

RESUMO

Diatomaceous earth or diatom (DE) are naturally available and low cost micro particles with distinct porous structure were used as an adsorbent for the removal of a hazardous dye, Eriochrome Black T (EBT). The surface modification of these DE were performed by sol-gel and hydrothermal methods to obtain a series of adsorbents such as diatom-ceria (DC), diatom-silica xerogel (DX), and diatom-silica xerogel-ceria (DXC). A cauliflower like morphology structure of ceria was observed on DE and DX. The adsorption performance of EBT was conducted by varying various parameters such as pH, adsorbent dosage, initial concentration, contact time and ionic strength. The materials DE, DC, DX and DXC showed the EBT removal efficiencies of 52, 77, 20, and 93%, respectively. The maximum adsorption capacity (qm) of DE, DC, DX and DXC was found to be 13.83, 23.64, 0.2 and 47.02 mgg-1 for the adsorption of EBT, respectively. The selectivity of EBT towards DXC was evaluated by treating a mixture of anionic dyes. The dye removal experiments was performed in presence of inorganic salts, however the presence of these salts did not affect the removal efficiency of DXC. Furthermore, the reusability of DXC was studied by recycling it up to 5 times and even at 5th cycle a removal efficiency of ∼66.8% was found. Thus, these studies demonstrate that the DXC material could be a promising candidate for the removal of EBT via adsorption for real time application in water treatment.


Assuntos
Compostos Azo/análise , Corantes/análise , Terra de Diatomáceas/metabolismo , Diatomáceas/metabolismo , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Porosidade , Reciclagem , Sílica Gel/química
4.
Anal Bioanal Chem ; 411(28): 7539-7549, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31641825

RESUMO

Starting from simple graphite flakes, an electrochemical sensor for sunset yellow monitoring is developed by using a very simple and effective strategy. The direct electrochemical reduction of a suspension of exfoliated graphene oxide (GO) onto a glassy carbon electrode (GCE) surface leads to the electrodeposition of electrochemically reduced oxide at the surface, obtaining GCE/ERGO-modified electrodes. They are characterized by cyclic voltammetry (CV) measurements and field emission scanning electron spectroscopy (FE-SEM). The GCE/ERGO electrode has a high electrochemically active surface allowing efficient adsorption of SY. Using differential pulse voltammetry (DPV) technique with only 2 min accumulation, the GCE/ERGO sensor exhibits good performance to SY detection with a good linear calibration for concentration range varying 50-1000 nM (R2 = 0.996) and limit of detection (LOD) estimated to 19.2 nM (equivalent to 8.9 µg L-1). The developed sensor possesses a very high sensitivity of 9 µA/µM while fabricated with only one component. This electrochemical sensor also displays a good reliability with RSD value of 2.13% (n = 7) and excellent reusability (signal response change < 3.5% after 6 measuring/cleaning cycles). The GCE/ERGO demonstrates a successful practical application for determination of sunset yellow in commercial soft drinks. Graphical abstract.


Assuntos
Compostos Azo/análise , Bebidas/análise , Técnicas Eletroquímicas/instrumentação , Corantes de Alimentos/análise , Grafite/química , Calibragem , Cromatografia Líquida de Alta Pressão , Limite de Detecção , Reprodutibilidade dos Testes
5.
Chemosphere ; 235: 1007-1014, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31561289

RESUMO

Electro-peroxone is a novel advanced oxidation process that surpasses ozonation or peroxone because of its advantages. In this technology, combining ozone and hydrogen peroxide generated electrochemically leads to the production of hydroxyl radicals, which are the strongest oxidizing agents. In this study, a cylindrical reactor with a continuous circular flow using novel arrangements of electrodes was used to examine the effects of variant parameters on dye removal efficiency. Acid Orange 7 (C16H11N2NaO4S) served as an indicator pollutant. Based on overall energy consumption and energy consumption per dye removed weight, electro-peroxone not only has proper efficiency at high dye concentrations, it also has the least energy consumption per dye removed weight; 53 KWh kg-1 is achieved for 500 mg L-1 initial dye concentration at 99% removal efficiency after 40 min. The results show that at the optimum condition of [Dye] = 500 mg L-1, pH = 7.7, applied current = 0.5 A, O3 rate = 1 L min-1, and [Na2SO4] = 0.1 M, dye is removed completely after 90 min and COD and TOC removal is 99% and 90%, respectively. LC-MS results also showed that AO7 initially was converted to more toxic compounds than AO7 like benzoic acid but finally linear acidic intermediate with less toxicity such as fumaric acid was formed.


Assuntos
Compostos Azo/química , Benzenossulfonatos/química , Eletrodos , Peróxido de Hidrogênio/química , Radical Hidroxila/química , Oxidantes/química , Ozônio/química , Poluentes Químicos da Água/química , Compostos Azo/análise , Benzenossulfonatos/análise , Eletrólise , Oxirredução , Poluentes Químicos da Água/análise
6.
Artigo em Inglês | MEDLINE | ID: mdl-31535956

RESUMO

Non-destructive, simple and fast techniques for identifying authentic palm oil and those adulterated with Sudan dyes using portable NIR spectroscopy would be very beneficial to West Africa countries and the world at large. In this study, a portable NIR spectroscopy coupled with multivariate models were developed for detecting palm oil adulteration. A total of 520 samples of palm oil were used comprising; 40 authentic samples together with 480 adulterated samples containing Sudan dyes (I, II, III, IV of 120 samples each). Multiplicative scatter correction (MSC) preprocessing technique plus Principal component analysis (PCA) was used to extract relevant spectral information which gave visible cluster trends for authentic samples and adulterated ones. The performance of Linear discriminant analysis (LDA) and Support vector machine (SVM) were compared, and SVM showed superiority over LDA. The optimised results by cross-validation revealed that MSC-PCA + SVM gave an identification rate above 95% for both calibration and prediction sets. The overall results show that portable NIR spectroscopy together with MSC-PCA + SVM model could be used successfully to identify authentic palm oils from adulterated ones. This would be useful for quality control officers and consumers to manage and control Sudan dyes adulteration in red palm oil.


Assuntos
Compostos Azo/análise , Corantes/análise , Contaminação de Medicamentos , Contaminação de Alimentos/análise , Naftóis/análise , Óleo de Palmeira/química , Espectroscopia de Luz Próxima ao Infravermelho
7.
Artigo em Inglês | MEDLINE | ID: mdl-31449473

RESUMO

A new, simple, low cost, high efficiency, and rapid floating technique was developed for the determination of Sunset Yellow in beverage and effervescent vitamin C. The method is based on two main steps: 1)- formation of dye-surfactant complex by the addition of a cationic surfactant, cetyltrimethylammonium bromide, to the solution containing an anionic dye (Sunset Yellow) and 2)- flocculation of the dye-surfactant complex with the participation of sodium perchlorate as a coagulant followed by aggregation and enlargement of the flocs while floating at the top of the solution. After the extraction, separated and preconcentrated Sunset Yellow was investigated by spectrophotometric determination. IR spectrum, scanning electron microscopy (SEM), and light microscopy were used to characterise the flocs. The effects of different parameters such as pH, concentration of surfactant, concentration of sodium perchlorate, and temperature on the extraction of dye were investigated and optimized. Under optimum conditions, a linear calibration curve was obtained in the range of 0.05-5 mg L-1. The detection limit (3Sb/m) was 0.02 mg L-1 with a preconcentration factor of 25. The relative standard deviation (RSD) for 0.1 mg L-1 of Sunset Yellow was 2.6% (n = 10). The applicability of the method was evaluated by measuring the amount of dye in beverage and effervescent vitamin C. Interferences of typical cations and anions which may participate in the matrices were also checked. The amount of Sunset Yellow found in real samples was 1.32-3.89 mgL-1.


Assuntos
Ácido Ascórbico/química , Compostos Azo/análise , Bebidas/análise , Comprimidos/química , Espectrofotometria
8.
Food Chem ; 299: 125144, 2019 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-31323440

RESUMO

Magnetic nanoparticles were synthesised to extract Sudan dyes from chilli powders. The adsorbents used were magnetic ferroferric oxide nanoparticles coated with polystyrene. The extraction procedures for Sudan dyes comprised liquid-solid extraction and magnetic solid phase extraction. The conditions were optimised to achieve efficient magnetic solid phase extraction, including extraction and desorption time, type and volume of the desorption solvent, and the mass of the adsorbents. Repeatability tests showed satisfactory recovery rates of 80.2-115.8%, with a relative standard deviation <3.8%. The results suggested that the proposed extraction method was effective and efficient to extract Sudan dyes from chilli powders. The extraction process was simpler compared with traditional approaches because the adsorbents can be rapidly removed from the sample matrix using a permanent magnet. The use of recyclable adsorbents decreased the cost greatly. Chilli powder samples collected from local markets in Singapore were tested using the proposed method under optimum conditions.


Assuntos
Capsicum/química , Corantes/análise , Contaminação de Alimentos/análise , Nanopartículas de Magnetita/química , Compostos Azo/análise , Fracionamento Químico/métodos , Cromatografia Líquida de Alta Pressão , Análise de Alimentos/instrumentação , Análise de Alimentos/métodos , Pós/química , Reprodutibilidade dos Testes , Singapura , Extração em Fase Sólida/instrumentação , Extração em Fase Sólida/métodos
9.
BMC Res Notes ; 12(1): 460, 2019 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-31349864

RESUMO

OBJECTIVE: Excipients are needed in the formulation of oral liquid medicines intended for children; they have however been reported to trigger safety issues. This study evaluated the concentrations and prevalence of ethanol and other potentially harmful excipients in pediatric formulations marketed in South Eastern Nigeria in line with international labeling guidelines and allowable daily limits (ADL). The study sampled oral pediatric formulations offered for sale in registered pharmacies. Those with accessible information leaflets were assessed for the presence and quantity of previously flagged excipients with potential to harm the pediatric population. RESULT: Of the 380 oral pediatric medicines, 140 provided access to list/quantity of ingredients. 47.9% (67) of the formulations contain at least one of the flagged excipients while the remaining only listed the active ingredients. Ethanol had the highest occurrence (62.7%) and was more in cough/cold medicines. A homeopathic cough and cold remedy had concentration of 90% v/v. Ethanol and sucrose in some formulations exhibited concentrations with a potential of crossing their approved daily intake (ADI) (1-90% v/v and 1.7 g-3.7 g/5 ml respectively). Ethanol use in studied pediatric formulations was quite high, with ethanol-containing formulations being prescribed for children 0-6 years and older. Only 26 (38.8%) completely satisfied the labelling requirements for ethanol containing formulations.


Assuntos
Formas de Dosagem , Etanol/análise , Excipientes/análise , Farmácias/ética , Administração Oral , Aspartame/análise , Compostos Azo/análise , Criança , Humanos , Nigéria , Parabenos/análise , Polissorbatos/análise , Propilenoglicol/análise , Sacarina/análise , Benzoato de Sódio/análise , Sorbitol/análise , Sacarose/análise , Inquéritos e Questionários
10.
Environ Pollut ; 252(Pt A): 749-757, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31195175

RESUMO

CuFeO2/CeO2 as a novel catalyst was synthesized and its catalytic performance was evaluated for electro-Fenton degradation of acid orange 7 (AO7). It was demonstrated from the characterization results that the rhombohedral structure of CuFeO2 and face-centered cubic fluorite structure of CeO2 remained stable after nanocomposite construction. The impact of such operating parameters as pH, current intensity and, catalyst amount was investigated and the optimum conditions (100 mgL-1 AO7, pH 3, 150 mgL-1 CuFeO2/CeO2, I: 150 mA) determination led to 99.3% AO7 removal and 79.1% COD removal in 60 min. The introduction of CeO2 as non-inert support had a significant impact on H2O2 electro-generation as an important step in AO7 removal. CuFeO2/CeO2 presented negligible metal leaching (iron 4.13%, copper 2.4%, and cerium 0.33%) which could be due to the strong interaction between active species and support. The nanocomposite performed efficiently in salty systems and two samples of real wastewaters due to Brønsted acidity character of ceria, which makes it a potential choice in industrial applications. The good performance of nanocomposite could be the result of the synergistic effect between Fe, Cu, and Ce. Regarding scavenging measurements results, the electro-Fenton process followed the Haber-Weiss mechanism. The by-products detection was performed using GC-MS analysis to propose an acceptable pathway for EF degradation of AO7. The BMG kinetics model (1/b = 0.969 (min) and 1/m = 0.269 (min-1)) was matched with the experimental data and described the kinetics of reaction very well. The catalytic activity of CuFeO2/CeO2 almost remained after six cycles. Based on the obtained results, CuFeO2/CeO2 using the benefit of the synergistic effect of Ce3+ with Fe2+ and Cu+can be introduced as a promising novel catalyst for the electro-Fenton reaction in wastewater treatment.


Assuntos
Compostos Azo/química , Benzenossulfonatos/química , Nanocompostos/química , Poluentes Químicos da Água/química , Compostos Azo/análise , Benzenossulfonatos/análise , Catálise , Peróxido de Hidrogênio/análise , Peróxido de Hidrogênio/química , Cinética , Águas Residuárias/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos
11.
Food Chem ; 293: 340-347, 2019 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-31151621

RESUMO

A green and simple method was designed to synthesize polyethyleneimine (PEI)-modified magnetic nanoparticles (MNPs), which were later used as adsorbents in magnetic solid phase extraction (MSPE) process. A new MSPE-HPLC method was then established for the simultaneous determination of four representative synthetic colorants (Amaranth, Ponceau 4R, Sunset yellow and Allure red) in food samples. Several important factors, such as the pH of the sample solution, the amount of adsorbent, the adsorption time, and the type of the eluent were investigated in detail. Under the optimized experimental conditions, the four colorants were measured with good linearity, detection limit and quantification limit. Adsorption kinetics and isotherms were also investigated to elucidate the adsorption mechanism. The detection of four colorants in candy, jelly and carbonated drink proved that the established MSPE-HPLC method was simple and effective and can be used for the analysis of colorants in real samples.


Assuntos
Bebidas/análise , Análise de Alimentos/métodos , Corantes de Alimentos/análise , Nanopartículas de Magnetita/química , Polietilenoimina/química , Adsorção , Compostos Azo/análise , Doces/análise , Cromatografia Líquida de Alta Pressão , Química Verde , Concentração de Íons de Hidrogênio , Limite de Detecção , Naftalenossulfonatos/análise , Reprodutibilidade dos Testes , Extração em Fase Sólida/instrumentação , Extração em Fase Sólida/métodos
12.
Artigo em Inglês | MEDLINE | ID: mdl-31180811

RESUMO

Spices are added in order to enhance the organoleptic characteristics of food and culinary dishes, making them more attractive for consumers. The use of illicit cheap colourants might be profitable along the food supply chain, posing undue risks to human health. This work evaluates the feasibility of NIR spectroscopy with chemometrics as a rapid, simple, non-destructive and affordable screening tool to determine the presence of Sudan I, II, III, IV and Para-red dyes in paprika. The dataset comprised unadulterated and adulterated samples with the five studied dyes at different concentration levels. Several multivariate classification models were built with Linear Discriminant Analysis (LDA) and different machine learning techniques. Preliminary results show that a classifier based on only six wavenumbers is able to determine the presence of some of these dyes in food samples in levels that may represent risk to human health. Sensitivities and specificities above 90% were obtained in almost all cases. These results show the feasibility of inexpensive and portable devices that can be useful for screening out adulterated stock along the food chain supply.


Assuntos
Compostos Azo/análise , Naftóis/análise , Análise Discriminante , Contaminação de Alimentos/análise , Humanos , Sensibilidade e Especificidade , Espectroscopia de Luz Próxima ao Infravermelho
13.
Environ Pollut ; 252(Pt A): 784-793, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31200204

RESUMO

Dust samples were collected from four indoor environments, including childcare facilities, houses, hair salons, and a research facility from the USA and were analyzed for brominated compounds using full scan liquid chromatography high-resolution mass spectrometry. A total of 240 brominated compounds were detected in these dust samples, and elemental formulas were predicted for 120 more abundant ions. In addition to commonly detected brominated flame retardants (BFRs), nitrogen-containing brominated azo dyes (BADs) were among the most frequently detected and abundant. Specifically, greater abundances of BADs were detected in indoor dusts from daycares and salons compared to houses and the research facility. Using authentic standards, a quantitative method was established for two BADs (DB373: Disperse Blue 373 and DV93: Disperse Violet 93) and 2-bromo-4,6-dinitroaniline, a commonly used precursor in azo dye production, in indoor dust. Generally, greater concentrations of DB373 (≤3850 ng/g) and DV93 (≤1190 ng/g) were observed in indoor dust from daycares highlighting children as a susceptible population to potential health risk from exposure to BADs. These data are important because, to date, targeted analysis of brominated compounds in indoor environments has focused mainly on BFRs and appears to underestimate the total amount of brominated compounds.


Assuntos
Poluição do Ar em Ambientes Fechados/análise , Compostos de Anilina/análise , Compostos Azo/análise , Poeira/análise , Retardadores de Chama/análise , Hidrocarbonetos Bromados/análise , Criança , Creches , Cromatografia Líquida , Éteres Difenil Halogenados/análise , Humanos , Nitrogênio/análise , Espectrometria de Massas em Tandem
14.
Environ Sci Pollut Res Int ; 26(18): 18392-18402, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31049863

RESUMO

The removal of Acid Orange 51 (AO 51) dye in aqueous solution by microscale zero-valent iron (m-ZVI) was investigated. The m-ZVI powder was characterized granulometrically by laser particle sizer and morphologically by transmission electron microscopy (TEM). The effects of pH, m-ZVI concentration, H2O2 addition, and dye concentration on the decolorization of AO 51 were experimentally investigated. Results indicate that the removal efficiency is independent from pH values, increases with increasing ZVI dosage, and decreases with dye concentration. With 1 g/L of m-ZVI, AO 51 was effectively removed without and with addition of 25 mM H2O2, yielding a decolorization efficiency of around 70% and 98%, respectively, at pH 3 within 60 min of reaction time. The involvement of ˙OH in oxidizing AO 51 was examined by measuring the removal rates based on ˙OH scavenging molecule. Finally, the disappearance of AO 51 was estimated by monitoring the UV-Vis spectral evolution after 120 min of treatment while the Fourier-Transform Infrared spectroscopy (FT-IR) was performed to verify the occurrence of organic sorption on m-ZVI surface. The scanning electron microscope (SEM) images before and after the reaction illustrated morphological changes on m-ZVI surface. The detoxification of the treated solution was demonstrated using phytotoxicity test.


Assuntos
Compostos Azo/análise , Peróxido de Hidrogênio/química , Ferro/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Propriedades de Superfície
15.
Water Sci Technol ; 79(7): 1287-1296, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31123228

RESUMO

Our findings proved that micron-scale zero-valent iron (mZVI) particles with pre-magnetization combined with peroxymonosulfate (PMS) can markedly enhance the removal of acid orange 7 (AO7). Investigation into the mechanism showed that PMS accelerated the corrosion of ZVI to release Fe2+ under acidic conditions, and the in-situ generated Fe2+ further activated PMS to produce SO4•- and •OH, resulting in AO7 removal. Further, the Lorentz force strengthened the convection in the solution and the field gradient force tended to move Fe2+ from a higher to a lower field gradient at the pre-magnetized ZVI (Pre-ZVI) particle surfaces, thus indicating that pre-magnetization promoted the corrosion of ZVI to release Fe2+, which resulted in the enhancement of PMS activation. Nano-scale ZVI (nZVI) was more effective than mZVI in activating PMS to degrade AO7, but the pre-magnetization effect on mZVI was better than on nZVI. AO7 removal increased with higher ZVI and PMS dosage, lower AO7 concentration, and acidic conditions (pH = 2, 3). This study helps to understand the reactive radicals-based oxidation process with application of pre-magnetized ZVI in activating PMS.


Assuntos
Compostos Azo/química , Benzenossulfonatos/química , Peróxidos/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Compostos Azo/análise , Benzenossulfonatos/análise , Catálise , Corrosão , Ferro/química , Poluentes Químicos da Água/análise
16.
IET Nanobiotechnol ; 13(2): 134-143, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31051443

RESUMO

This work explores the rapid synthesis of silver nanoparticles (AgNPs) from Musa paradisiaca (M. paradisiaca) bract extract. The bio-reduction of Ag+ ion was recorded using ultraviolet-visible spectroscopy by a surface plasmon resonance extinction peak with an absorbance at 420 nm. The phytoconstituents responsible for the reduction of AgNPs was probed using Fourier transform infrared spectroscopy. The X-ray diffraction pattern confirmed the formation of crystalline AgNPs that were analogous to selected area electron diffraction patterns. Morphological studies showed that the obtained AgNPs were monodispersed with an average size of 15 nm. The biologically synthesised AgNPs showed higher obstruction against tested phytopathogens. The synthesised AgNPs exhibited higher inhibitory zone against fungal pathogen Alternaria alternata and bacterial pathogen Pseudomonas syringae. Free radical scavenging potential of AgNPs was investigated using 1,1-diphenyl-2-picryl hydroxyl and 2,2-azinobis (3-ethylbenzothiazoline)-6-sulphonic acid assays which revealed that the synthesised AgNPs act as a potent radical scavenger. The catalytic efficiency of the synthesised AgNPs was investigated for azo dyes, methyl orange (MO), methylene blue (MB) and reduction of o-nitrophenol to o-aminophenol. The results portrayed that AgNPs act as an effective nanocatalyst to degrade MO to hydrazine derivatives, MB to leucomethylene blue, and o-nitro phenol to o-amino phenol.


Assuntos
Anti-Infecciosos/química , Depuradores de Radicais Livres/química , Nanopartículas Metálicas/química , Musa/química , Extratos Vegetais/metabolismo , Prata/química , Anti-Infecciosos/metabolismo , Anti-Infecciosos/farmacologia , Compostos Azo/análise , Compostos Azo/metabolismo , Bactérias/efeitos dos fármacos , Compostos de Bifenilo/análise , Compostos de Bifenilo/metabolismo , Depuradores de Radicais Livres/metabolismo , Depuradores de Radicais Livres/farmacologia , Fungos/efeitos dos fármacos , Química Verde , Picratos/análise , Picratos/metabolismo , Extratos Vegetais/química , Prata/metabolismo
17.
IET Nanobiotechnol ; 13(2): 144-149, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31051444

RESUMO

Azo dyes are widely used in industries and their release in the environment contributes to the pollution of effluents. The authors aim to develop a new eco-friendly water treatment method for the degradation of azo dyes based on in situ magnetic separation and immobilisation of bacterial cells. The immobilisation was achieved using superparamagnetic Fe3O4 nanoparticles and offers the possibility of reusing bacteria by magnetic separation for several degradation cycles. The iron-oxide nanoparticles were synthesised by reverse co-precipitation. The Gram-positive bacteria Bacillus subtilis were immobilised using iron-oxide nanoparticles by adsorption and then separated with an external magnetic field. Transmission electron microscopy observation showed that the particles' diameter was ∼20 nm with a narrow size distribution. Moreover, the iron-oxide nanoparticles were adsorbed onto the surface in order to coat the cells. B. subtilis has proved its ability to decolorise and degrade several azo dyes at different values of pH, with the highest decolorisation rate for Congo red. Furthermore, immobilised cells have a degradation activity similar to that of free cells. The system provided a degradation rate up to 80% and could be reused for seven batch cycles.


Assuntos
Compostos Azo/metabolismo , Bacillus subtilis , Células Imobilizadas , Nanopartículas de Magnetita/química , Purificação da Água/métodos , Compostos Azo/análise , Bacillus subtilis/citologia , Bacillus subtilis/metabolismo , Células Imobilizadas/citologia , Células Imobilizadas/metabolismo , Química Verde/métodos
18.
Environ Sci Pollut Res Int ; 26(19): 19207-19219, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31069651

RESUMO

Cedar bark (Cedrella fissilis), a waste from wood processing, was evaluated as an adsorbent for the removal of red 97 dye from effluents. The material exhibited an amorphous structure, irregular surface, and was mainly composed of lignin and holocellulose. The adsorption was favored at pH 2.0. The general order model was most suitable for describing the experimental kinetic data, being the equilibrium reached in around 30 min. The isotherm experiments were better described by the Langmuir model. The maximum adsorption capacity was 422.87 mg g-1 at 328 K. The values of standard Gibbs free energy change (ΔG0) were from - 21 to - 26 kJ mol-1, indicating a spontaneous and favorable process. The enthalpy change (ΔH0) was 18.98 kJ mol-1, indicating an endothermic process. From the fixed bed adsorption experiment, an inclined breakthrough curve was found, with a mass transfer zone of 5.36 cm and a breakthrough time of 329 min. Cedar bark was able to treat a simulated effluent attaining color removal of 86.6%. These findings indicated that cedar bark has the potential to be applied as a low-cost adsorbent for the treatment of colored effluents in batch and continuous adsorption systems.


Assuntos
Compostos Azo/análise , Casca de Planta/química , Resíduos/análise , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Termodinâmica
19.
Water Sci Technol ; 79(6): 1164-1173, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31070596

RESUMO

The removal of methyl orange (MO) in a copper-loaded silicon carbide (Cu/SiC) system under microwave (MW) irradiation was studied. Cu/SiC was synthesized by employing an impregnation method and the effects of parameters such as reaction time, catalyst dosage, hydrogen peroxide (H2O2) dosage, microwave power and pH on the rate of degradation of MO were also studied. The obtained results showed that almost complete degradation was obtained in the presence of Cu/SiC catalyst within 8 min of irradiation when 100 mL of MO solution (20 mg/L), 3 ml/L of H2O2, 2 g/L of catalyst dose, 600 W of MW power, and pH 7 were applied. The Cu-bearing catalyst with H2O2 formed a Fenton-like system and the rate of generation of hydroxyl radicals (·OH) was also accelerated by subjecting to MW. From the kinetic analysis, it is revealed that the degradation of MO using the MW-Cu/SiC-H2O2 system follows the pseudo-first-order.


Assuntos
Compostos Azo/química , Peróxido de Hidrogênio , Micro-Ondas , Poluentes Químicos da Água/química , Purificação da Água/métodos , Compostos Azo/análise , Catálise , Cinética , Oxirredução , Poluentes Químicos da Água/análise
20.
Water Sci Technol ; 79(6): 1184-1194, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31070598

RESUMO

In this study, Eriochrome Black T (EBT) in water was decolorized by means of argon atmospheric pressure plasma jet (APPJ), which showed great decolorization performance. The results showed that the relatively high decolorization rate (approximately 80%) was obtained after plasma treatment for 6 min. Changes to some reactive oxygen and nitrogen species (RONS) in the liquid phase were detected. The contents of peroxide, HO·, O2-·, and NO· in the plasma-treated EBT solution were much less than those in the activated water. The roles of H2O2 and HO· in the decolorization of EBT solution were explored by evaluating the effects of their scavengers, and by exploring the direct effect of H2O2. The results indicated that reactive oxygen species (ROS), especially HO· and O2-·, played significant roles in the decolorization of the EBT solution. Analysis of degradation by-products indicated that plasma discharge could destroy the azo bond first and gradually break the aromatic rings of EBT molecules into small molecular compounds.


Assuntos
Pressão Atmosférica , Compostos Azo/química , Peróxido de Hidrogênio , Poluentes Químicos da Água/química , Purificação da Água/métodos , Compostos Azo/análise , Nitrogênio , Poluentes Químicos da Água/análise
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