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1.
SAR QSAR Environ Res ; 31(9): 697-715, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32878494

RESUMO

Azo dyes are a group of chemical moieties joined by azo (-N=N-) group with potential usefulness in different industrial applications. But these dyes are not devoid of hazardous consequence because of poor affinity for the fibre and discharge into the water stream. The chemical aspects of 72 azo dyes towards cellulose fibre in terms of their affinity by QSPR have been explored in the present work. We have employed two approaches, namely balance of correlation without IIC (TF1) and balance of correlation with IIC (TF2), to generate 16 QSAR models from 8 splits. The determination coefficient of calibration and validation set was found higher when the QSPR models were developed using the index of ideality correlation (IIC) parameter (TF2). The model developed with TF2 for split 3 was considered as a prominent model because the determination coefficient of the validation set was maximum (r 2 = 0.9468). The applicability domain (AD) was also analysed based on 'statistical defect', d(A) for a SMILES attribute. The mechanistic interpretation was done by identifying the SMILES attributes responsible for the promoter of endpoint increase and promoter of endpoint decrease. These SMILES attributes were applied to design 15 new dyes with higher affinity for cellulose fibre.


Assuntos
Compostos Azo/química , Celulose/química , Corantes/química , Relação Quantitativa Estrutura-Atividade , Adsorção , Simulação por Computador , Método de Monte Carlo
2.
Ecotoxicol Environ Saf ; 203: 111026, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32888594

RESUMO

The detection of phenolic compounds, i.e. resorcinol (RC) catechol (CC) and hydroquinone (HQ) are important due to their extremely hazardous impact and poor environmental degradation. In this work, a novel and sensitive composite of electrochemically reduced graphene oxide-poly(Procion Red MX-5B)/gold nanoparticles modified glassy carbon electrode (GCE/ERGO-poly(PR)/AuNPs) was assembled for voltammetric detection of benzenediol isomers (RC, CC, and HQ). The nanocomposite displayed high peak currents towards the oxidation of RC, HQ, and CC compared to non-modified GCE. The peak-to-peak separations were 0.44 and 0.10 V for RC-CC and CC-HQ, respectively. The limit of detections were 53, 53, and 79 nM for HQ, CC, and RC with sensitivities of 4.61, 4.38, and 0.56 µA/µM (S/N = 3), respectively. The nanocomposite displayed adequate reproducibility, besides good stability and acceptable recoveries for wastewater and cosmetic samples analyses.


Assuntos
Compostos Azo/química , Derivados de Benzeno/análise , Técnicas Eletroquímicas/métodos , Ouro/química , Grafite/química , Nanocompostos/química , Poluentes Químicos da Água/análise , Cosméticos/química , Eletrodos , Nanopartículas Metálicas/química , Oxirredução , Reprodutibilidade dos Testes , Águas Residuárias/química
3.
Ecotoxicol Environ Saf ; 202: 110924, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32800211

RESUMO

Fabrication of poly-(N-isopropylmethacrylamide-co-methacrylic acid) [p(NMA)] microgels to be utilized as microreactors to synthesize stable Ag nanoparticles for catalytic reductive degradation of dyes has been addressed in this work. Both p(NMA) microgel and Ag-p(NMA) hybrid microgel systems have been analyzed by Fourier transform infra-red and Dynamic light scattering, Ultraviolet-Visible spectroscopy, X-ray diffraction and Transmission electron microscopy. Catalytic activity of Ag-p(NMA) towards reductive degradation of Congo Red (CR), Methyl Orange (MO) and Alizarin Yellow (AY) was investigated under different operating conditions. Spectrophotometry was employed to check the progress of reaction while the rate constant (kapp) value of degradation reaction was determined under various conditions to optimize reaction parameters for rapid and economical degradation of these dyes. An increase in kapp value was observed by increasing feed content of dye up to a certain value that decreases again by further increment in dye concentration which reflects that catalysis follows Langmuir-Hinshelwood mechanism. A gradual increase in the kapp value was also observed with increasing quantity of hybrid microgel used as a catalyst. By comparing kapp values of degradation of aforementioned dyes, it was found that Ag-p(NMA) hybrid microgel gives better activity for MO dye degradation in comparison to catalytic degradation of CR and AY.


Assuntos
Compostos Azo/química , Nanopartículas Metálicas/química , Prata/química , Catálise , Corantes/química , Vermelho Congo/química , Hidrogéis/química , Microscopia Eletrônica de Transmissão , Polímeros/química , Espectrofotometria , Difração de Raios X
4.
J Chromatogr A ; 1626: 461362, 2020 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-32797841

RESUMO

Exploring new material as adsorbent for the efficient enrichment of pollutants is always of great significance in analytical chemistry. In this work, a magnetic azobenzene framework (labeled as MAzo) was constructed as a magnetic solid phase extraction (MSPE) adsorbent by a simple and environmentally benign strategy. The MAzo exhibited the attractive features of strong magnetism, outstanding adsorption performance, as well as good reusability. Combining MAzo-based MSPE with high performance liquid-phase chromatography, a simple and effective method was developed for simultaneous determination of four phenylurea herbicides in pear juice and apple juice samples. Under optimized experimental conditions, the method offered low limits of detection of 0.05-0.15 ng mL-1, high recoveries of 86.7-109.2% with RSD less than 7%. Density functional theory calculation indicated that the good adsorption performance of MAzo for PUHs can be ascribed to the strong H-bonding forces and weak π-π interactions. The facile, green, low-cost synthesis method together with the excellent adsorption performance endows the MAzo great application prospect in sample preparation.


Assuntos
Compostos Azo/química , Poluentes Ambientais/análise , Herbicidas/análise , Compostos de Fenilureia/análise , Extração em Fase Sólida/métodos , Adsorção , Cromatografia Líquida de Alta Pressão , Poluentes Ambientais/isolamento & purificação , Sucos de Frutas e Vegetais/análise , Herbicidas/isolamento & purificação , Fenômenos Magnéticos , Malus , Estruturas Metalorgânicas , Compostos de Fenilureia/isolamento & purificação , Pyrus
5.
Chemosphere ; 259: 127466, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32615456

RESUMO

This work addresses the mineralization of the widely used Methyl Orange (MO) azo dye by technologies based on H2O2 electrogeneration at a 3D-like air-diffusion cathode. These include two Fe2+-catalyzed processes such as electro-Fenton (EF) and photoelectro-Fenton (PEF). Bulk electrolyses were performed in a recirculation flow plant, in which the Eco-Cell filter-press electrochemical reactor was connected in series with a UVA photoreactor. The former reactor was equipped with a Ti|Ir-Sn-Sb oxide plate anode alongside a 3D-like air-diffusion cathode made from graphite felt and hydrophobized carbon cloth, aimed at electrogenerating H2O2 on site. The influence of current density (j), volumetric flow rate (Q) and initial MO concentration was examined. The greatest oxidation power corresponded to PEF process. The best operation conditions to treat 30 mg L-1 of total organic carbon of MO in a 50 mM Na2SO4 solution by PEF were found at 0.50 mM Fe2+, pH 3.0, j = 20 mA cm-2 and Q = 2.0 L min-1, obtaining 100% and 94% of color and TOC removals at 30 and 240-300 min, respectively. This accounted for 35% of mineralization current efficiency and 0.12 kWh (g TOC)-1 of energy consumption at the end of the electrolysis. The oxidation power of EF and PEF was compared with that of anodic oxidation (AO), and the sequence obtained was: PEF > EF > AO. The dye was gradually degraded, yielding non-toxic short carboxylic acids, like maleic, fumaric, formic, oxalic and oxamic, whose Fe(III) complexes were rapidly photolyzed.


Assuntos
Compostos Azo/química , Poluentes Químicos da Água/química , Carbono , Ácidos Carboxílicos , Difusão , Eletrodos , Eletrólise , Compostos Ferrosos , Peróxido de Hidrogênio/química , Ferro/química , Oxirredução , Fotólise
6.
J Chromatogr A ; 1625: 461305, 2020 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-32709348

RESUMO

A novel kind of magnetic porous carbon nano-fibers (Fe3O4@P-CNFs) materials was successfully prepared and used as an adsorbent. Based on the above-mentioned adsorbent, a simple and effective magnetic disperse solid-phase extraction (MSPE) method was developed and first utilized to the enrichment and purification of five Sudan dyes (including Sudan I, Sudan II, Sudan III, Sudan IV, and Sudan Red 7B) in foodstuffs for the first time. High-performance liquid chromatography was used to determine the content of the Sudan dyes. The parameters affecting the extraction performance were studied and optimized, including the amount of the adsorbent and inorganic salt, type and the volume of the eluent, pH of the sample solution and extraction time. Under the optimized experimental conditions, the results show that the proposed method has a good linear relationship (r≥ 0.9993). The limits of detection range from 0.88 µg L-1 to 1.27 µg L-1. The recoveries range from 86.6% to 99.7% with the relative standard deviations ranging from 0.6% to 7.9% in the methodology validation. The above-mentioned results indicate that the proposed method is a sensitive and reliable procedure with good reproducibility for the detection of Sudan dyes residues in foodstuffs.


Assuntos
Compostos Azo/análise , Fibra de Carbono/química , Corantes/análise , Análise de Alimentos , Fenômenos Magnéticos , Nanofibras/química , Adsorção , Compostos Azo/química , Corantes/química , Concentração de Íons de Hidrogênio , Limite de Detecção , Nanofibras/ultraestrutura , Porosidade , Análise de Regressão , Reprodutibilidade dos Testes , Sais/química , Fatores de Tempo
7.
Arch Microbiol ; 202(8): 2135-2145, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32519019

RESUMO

In Pakistan, 55% of textile exports are contributed by textile-units of Faisalabad. The effluents of these textile units, being discharged without any treatment, contain the contamination of a huge amount of synthetic azo dyes. The objective of the current research was to evaluate the contribution of an azoreductase-encoding gene (azrS) from a pre-characterized azo dye decolorizing bacterial strain Bacillus sp. MR-1/2 in a high copy number host system (pUC19-T7-Top-T) of Escherichia coli strain DH5α followed by in-silico prediction of azoreductase enzyme (AzrS) function. The recombinant cells that contained azrS had a significantly higher rate of color removal in congo red and reactive black-5 dyes when compared to wild-type MR-1/2 and E. coli DH5α after 72 h of incubation. Moreover, we were able to show that the recombinant strain significantly reduced the values of all tested parameters (pH, EC, turbidity, TSS, and COD) in actual wastewater. In support of our results, it was also predicted through bioinformatics analysis that the deduced azoreductase protein of strain MR-1/2 is linked with the dye decolorization ability of the strain through NAD(P)H-ubiquinone: oxidoreductase activity. Furthermore, we also found that the deduced protein resembled closely related proteins of protein databank in many features, yet some unique features were predicted in the enzyme activity of strain MR-1/2. It was concluded that the recombinant strain could be examined in pilot-scale experiments for textile wastewater treatment.


Assuntos
Compostos Azo/metabolismo , Bacillus/enzimologia , Bacillus/genética , NADH NADPH Oxirredutases/genética , NADH NADPH Oxirredutases/metabolismo , Águas Residuárias/microbiologia , Purificação da Água , Compostos Azo/química , Biodegradação Ambiental , Escherichia coli/genética , Regulação Bacteriana da Expressão Gênica/genética , Paquistão
8.
J Chromatogr A ; 1624: 461265, 2020 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-32540055

RESUMO

Column miniaturization of liquid chromatography is a major trend in separation sciences with the advent of single-cell proteomics and metabolomics. Nanochannel chromatography is one of the promising tools for single-cell analyses because it provides ultra-small sample volume and high separation efficiency. However, non-fluorescent molecular detection in such small channels is still quite difficult due to fL-aL sample volume, which hinders further miniaturization of nanochannels. In this study, we overcame the size limitation of nanochannel chromatography by our label-free molecular detection method: photothermal optical diffraction (POD), which utilizes the photothermal effect of analytes and optical diffraction by nanochannel. The combination of the nanochannel chromatography and the POD enables 1.8 fL sample separation and label-free molecule detection in nanochannels with 800 nm width and 300 nm depth at the optimized experimental conditions. The limit of detection is 5.4 zmol (3300 molecules), approximately 50 times lower than the conventional label-free detection method. Furthermore, the theoretical plate number is calculated to be 105 plates/m, and the separation performance is discussed. Our label-free detection method will be widely used as a universal detector for nanochannel chromatography.


Assuntos
Cromatografia Líquida/métodos , Luz , Nanopartículas/química , Coloração e Rotulagem , Temperatura , Compostos Azo/química , Calibragem , Reprodutibilidade dos Testes , Análise de Célula Única
9.
Chemosphere ; 259: 127400, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32593002

RESUMO

Granular activated carbon (GAC) was used as catalyst for the activation of peroxydisulfate (PDS) to decolorize and degrade Acid Orange 7 (AO7) in water. EPR spectra and radical quencher experiments were employed to identify the active species for AO7 oxidation in the PDS/GAC system. Linear sweep voltammetry (LSV) and chronoamperometry test were carried out to identify the contribution of nonradical mechanism for AO7 decay. The investigation of crucial operational parameters on the decolorization indicated 100 mg/L AO7 can be almost totally decolorized in a broad range of pH. Common inorganic anions adversely affect the AO7 decolorization process and the inhibition was in the order of: HCO3- > H2PO4- > SO42- > Cl- > NO3-. UV-vis spectra showed the destruction of the aromatic moiety of AO7 molecule during the oxidation reaction of the PDS/GAC system. The transformation of nitrogen related to the azo bond in AO7 molecule in this system was observed by monitoring the released N-containing inorganic ions. Recycle experiments showed GAC cannot be reused directly but its catalytic ability can be restored by using electrochemical method.


Assuntos
Compostos Azo/química , Sulfatos/química , Poluentes Químicos da Água/química , Benzenossulfonatos , Catálise , Carvão Vegetal/química , Oxirredução , Reciclagem , Água
10.
Ecotoxicol Environ Saf ; 202: 110859, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32574861

RESUMO

The effects of quinoid compounds on azo dyes decolorization were studied. Compared with other quinones, menadione was the most effective at aiding azo dye decolorization. Sodium formate was a suitable carbon source for the anaerobic decolorization system. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis indicated that the microbial structure changed in response to varying carbon sources. Phylogenetic analysis showed that the anaerobic sludge was consisted mainly of nine genera. The mechanism studies showed that the biotransformation of menadione to its hydroquinone form was the rate-limiting step in the dye decolorization process. Moreover, study of the electron transfer mechanism of quinone-mediated reduction showed that azo dye decolorization is not a specific reaction. The NADH chain was involved in the decolorization process. The methane production test indicated that azo dyes had an inhibitory effect on methane production. However, supplementation with a redox mediator could recover the inhibited methanogenesis. High-throughput sequencing analysis revealed that the methanogenic archaeal community was altered in the anaerobic sludge with or without azo dyes and the redox mediator.


Assuntos
Compostos Azo/metabolismo , Quinonas/metabolismo , Eliminação de Resíduos Líquidos , Anaerobiose , Compostos Azo/química , Benzoquinonas , Biotransformação , Catálise , Corantes/química , Metano/metabolismo , Oxirredução , Filogenia , Quinonas/química , Esgotos
11.
Chemosphere ; 256: 127081, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32447112

RESUMO

Discharging coloring products in water bodies has degraded water quality irreversibly over the past several decades. Order mesoporous carbon (OMC) was modified by embedding neodymium(III) chloride on the surface of OMC to enhance the adsorptive removal towards these contaminants. This paper represents an artificial neural network (ANN) based approach for modeling the adsorption process of sunset yellow onto neodymium modified OMC (OMC-Nd) in batch adsorption experiments. Neodymium modified OMC was characterized using N2 adsorption-desorption isotherm, TEM micrographs, FT-IR and XPS spectra analysis techniques. 2.5 wt% Nd loaded OMC was selected as the final adsorbent for further experiments because OMC-2.5Nd showed highest removal efficiency of 93%. The ANN model was trained and validated with the adsorption experiments data where initial concentration, reaction time, and adsorbent dosage were selected as the variables for the batch study, whereas the removal efficiency was considered as the output. The ANN model was first developed using a three-layer back propagation network with the optimum structure of 3-6-1. The model employed tangent sigmoid transfer function as input in the hidden layer whereas a linear transfer function was used in the output layer. The comparison between modeled data and experimental data provided high degree of correlation (R2 = 0.9832) which indicated the applicability of ANN model for describing the adsorption process with reasonable accuracy.


Assuntos
Compostos Azo/química , Modelos Químicos , Redes Neurais de Computação , Adsorção , Carbono/química , Concentração de Íons de Hidrogênio , Cinética , Neodímio , Espectroscopia de Infravermelho com Transformada de Fourier
12.
Ecotoxicol Environ Saf ; 200: 110744, 2020 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-32460050

RESUMO

Hematite nanoparticles (α-Fe2O3 NPs) were successfully synthesized by a low-cost solvent-free reaction using Ferrous sulfate waste (FeSO4·7H2O) and pyrite (FeS2) as raw materials and employed for the decolorization of Methyl Orange by the photo-Fenton system. The properties of α-Fe2O3 NPs before and after photo-Fenton reaction were characterized by X-ray powder diffraction (XRD), Field emission scanning electron microscopy (FESEM), Fourier transform infrared (FT-IR) spectrum and X-ray photoelectron spectroscopy (XPS), and the optical properties of α-Fe2O3 NPs were analyzed by UV-vis diffuse reflectance spectra (UV-vis DRS) and Photoluminescence (PL) spectra. The analytic results showed that the as-formed samples having an average diameter of ~50 nm exhibit pure phase hematite with sphere structure. Besides, little differences were found by comparing the characterization data of the particles before and after the photo-Fenton reaction, indicating that the photo-Fenton reaction was carried out in solution rather than on the surface of α-Fe2O3 NPs. A 24 central composite design (CCD) coupled with response surface methodology (RSM) was applied to evaluate and optimize the important variables. A significant quadratic model (P-value<0.0001, R2 = 0.9664) was derived using an analysis of variance (ANOVA), which was adequate to perform the process variables optimization. The optimal process conditions were performed to be 395 nm of the light wavelength, pH 3.0, 5 mmol/L H2O2 and 1 g/L α-Fe2O3, and the decolorization efficiency of methyl orange was 99.55% at 4 min.


Assuntos
Compostos Azo/química , Corantes/química , Compostos Férricos/química , Nanopartículas Metálicas/química , Catálise , Compostos Férricos/síntese química , Compostos Ferrosos/química , Ferro/química , Solventes , Sulfetos/química
13.
Eur J Med Chem ; 200: 112403, 2020 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-32447198

RESUMO

By linking two N-methyl-N-carbocyclic quaternary ammonium groups to an azobenzene scaffold in meta- or para-positions we generated a series of photoswitchable neuromuscular ligands for which we coined the term "azocuroniums". These compounds switched between the (E)- and (Z)-isomers by light irradiation at 400-450 nm and 335-340 nm, respectively. Meta-azocuroniums were potent nicotinic ligands with a clear selectivity for the muscular nAChRs compared to neuronal α7 and α4ß2 subtypes, showed good solubility in physiologic media, negligible cell toxicity, and would not reach the CNS. Electrophysiological studies in muscle-type nAChRs expressed in Xenopus laevis oocytes showed that (E)-isomers were more potent than (Z)-forms. All meta-azocuroniums were neuromuscular blockers, with the exception of the pyrrolidine derivative that was an agonist. These new meta-azocuroniums, which can be modulated ad libitum by light, could be employed as photoswitchable muscle relaxants with fewer side effects for surgical interventions and as tools to better understand the pharmacology of muscle-type nAChRs.


Assuntos
Fármacos Neuromusculares/efeitos da radiação , Agonistas Nicotínicos/química , Receptores Nicotínicos/metabolismo , Animais , Compostos Azo/química , Humanos , Isomerismo , Ligantes , Luz , Fármacos Neuromusculares/síntese química , Agonistas Nicotínicos/efeitos da radiação , Oócitos , Compostos de Amônio Quaternário/química , Relação Estrutura-Atividade , Xenopus laevis
14.
Chemosphere ; 253: 126708, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32298912

RESUMO

The role of illumination and cathode is important to improve the efficiency of photoelectro-Fenton (PEF) system. In this study, cathodes with black carbon-poly tetra fluoro ethylene (BC-PTFE) for increase the concentration of hydrogen peroxide in PEF. A new PEF system using EIEL and BC-PTFE air-diffusion cathode was established. The electrode performance was tested and the influence factors, degradation kinetics, intermediates, pathway and mechanism of the model compound methyl orange (MO) were studied. The capacities of concentration decays and total organic carbon (TOC) removals were compared between different electrochemical advanced oxidation processes. The experimental conditions were optimized for a current density of 20 mA cm-2 with 0.5 mM Fe2+ and 100 mg L-1 MO at 20 °C and pH 3.0 in an 8 L reservoir. The higher MO concentration was, the smaller pseudo-first-order kinetic constants of concentration decays and TOC removals were. Intermediate products were identified by gas chromatography-mass spectrometry and ion-exclusion high performance liquid chromatograph in EIEL-PEF. Combined with frontier electron density, the degradation pathway was deduced as follows: destruction of azo bond, substitution of •OH, dehydrogenation and oxidation, opening-ring and mineralization. In EIEL-PEF, the concentration of oxalic acid and oxamic acid reached the maximum value 9.2 and 1.5 mg L-1 at 60 and 90 min, respectively. The photolysis of N-intermediates produced NH4+-N was released in more proportion than NO3--N and oxamic acid-N. The study indicated that PEF system has the potential to remove organic pollutants in aquatic environments.


Assuntos
Compostos Azo/química , Poluentes Químicos da Água/química , Carbono , Difusão , Eletrodos , Etilenos , Peróxido de Hidrogênio/química , Ferro/química , Cinética , Oxirredução , Fotólise , Fuligem , Raios Ultravioleta
15.
Chemosphere ; 253: 126673, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32302900

RESUMO

In this study, computational and statistical models were applied to optimize the inherent parameters of an electrochemical decontamination of synozol red. The effect of various experimental variables such as current density, initial pH and concentration of electrolyte on degradation were assessed at Ti/RuO0·3TiO0·7O2 anode. Response surface methodology (RSM) based central composite design was applied to investigate interdependency of studied variables and train an artificial neural network (ANN) to envisage the experimental training data. The presence of fifteen neurons proved to have optimum performance based on maximum R2, mean absolute error, absolute average deviation and minimum mean square error. In comparison to RSM and empirical kinetics models, better prediction and interpretation of the experimental results were observed by ANN model. The sensitive analysis revealed the comparative significance of experimental variables are pH = 61.03%>current density = 17.29%>molar concentration of NaCl = 12.7%>time = 8.98%. The optimized process parameters obtained from genetic algorithm showed 98.6% discolorization of dye at pH 2.95, current density = 5.95 mA cm-2, NaCl of 0.075 M in 29.83 min of electrolysis. The obtained results revealed that the use of statistical and computational modeling is an adequate approach to optimize the process variables of electrochemical treatment.


Assuntos
Compostos Azo/química , Eliminação de Resíduos Líquidos/métodos , Descontaminação , Eletrodos , Eletrólise , Cinética , Modelos Estatísticos , Redes Neurais de Computação , Titânio , Eliminação de Resíduos Líquidos/estatística & dados numéricos , Águas Residuárias/química , Poluentes Químicos da Água
16.
Chemosphere ; 251: 126380, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32163781

RESUMO

A detailed mechanistic investigation of the hydroxyl radical (•OH) formation and organic pollutant degradation over transition metal-doped and undoped TiO2 photocatalysts was performed by the quantitative measurement of •OH and the identification of intermediate products under various experimental conditions. The Fe-doped TiO2 as a typical subject was prepared, characterized and used to degrade an azo dye Acid Orange 7 (AO7). It is indicated that the enhanced photocatalytic activity of Fe-doped TiO2 for AO7 degradation was attributed to the increase in surface area, the facilitated charge transfer via Fe-dopant, and a red shift of absorbable wavelength, maintaining a great formation of •OH under visible irradiation. The oxidation of H2O by holes was estimated as the major pathway of •OH formation rather than the reduction of dissolved O2 by electrons, and their formation trends reached to approximately 75% and 25%, respectively. Meanwhile the synergistic effect of Fe-dopant produced nearly 10% of extra •OH by visible light photoactivation. The intermediate products and pathways of AO7 degradation varied greatly with different photocatalysts and conditions of the process, involving several reaction mechanisms such as the azo bond cleaving, naphthalene oxidation, desulfonation, and hydroxylated products generation. Through the quantification of •OH-reacted efficiency we proposed, a stoichiometry of •OH affecting overall reaction mechanisms in the TiO2-assisted photodegradation of AO7 was further established. This study can provide new insights on how to better clarify the variation regularity of organic pollutant degradation from different treatments of the •OH-based advanced oxidation processes.


Assuntos
Compostos Azo/química , Benzenossulfonatos/química , Luz , Fotólise , Catálise , Radical Hidroxila/química , Oxirredução , Titânio/química
17.
Chemosphere ; 252: 126483, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32197180

RESUMO

This study investigated the removal of Orange II by an electro-Fenton process using a novel recirculation flow-through reactor. The hydrogen peroxide was generated in-situ on the activated carbon fiber (ACF) modified with carbon black and polytetrafluoroethylene (PTFE). The modified ACF cathode was characterized by scanning electron microscopy (SEM) and nitrogen adsorption-desorption study. In light of the production of H2O2 and removal of Orange II, the optimum weight percentage of PTFE in the mixture of carbon black and PTFE was 75%. The effects of some important operating parameters such as current and flow rate were investigated. The best Orange II removal reached 96.7% with mineralization efficiency of 55.4% at 120 min under the current of 100 mA, initial pH 3, Fe2+ 0.3 mM and the flow rate of 7 mL min-1. The cathode exhibited good regeneration ability and stability. OH was proved to be the main oxidizing species in this flow-through electro-Fenton system. This work demonstrated that such electro-Fenton process using modified ACF cathode was promising for the degradation of organic pollutants.


Assuntos
Compostos Azo/química , Benzenossulfonatos/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Adsorção , Compostos Azo/análise , Benzenossulfonatos/análise , Fibra de Carbono , Carvão Vegetal/química , Fibras na Dieta , Eletrodos , Peróxido de Hidrogênio/química , Ferro/química , Oxirredução , Poluentes Químicos da Água/análise
18.
Chemosphere ; 252: 126487, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32220714

RESUMO

In this study, Electrolytic Manganese Residue (EMR) was treated by EDTA-2Na/NaOH, ultrasonic etching, and hydrothermal reaction to obtain a novel nanocomposite catalyst (called N-EMR), which then was used, together with H2O2, to treat synthetic textile wastewater containing Reactive Red X-3B, Methyl Orange, Methylene blue and Acid Orange 7. Results indicated that the N-EMR had a nano-sheet structure in sizes of 100-200 nm; new iron and manganese oxides with high activity were produced. The mixture of a small amount of N-EMR (40 mg/L) and H2O2 (0.4 × 10-3 M) could removal about 99% of azo dyes (at 100 mg/L in 100 mL) within 6-15 min, much faster than many advanced oxidation processes (AOPs) reported in the literature. The elucidation of the associated mechanism for azo dyes degradation indicates that azo dyes were attacked by superoxide radicals, hydroxyl radicals, and electron holes generated within system. N-EMR was found to be reusable and showed limited inhibition by co-existing anions and cations. Moreover, high removal efficiency of azo dyes could happen in the system with a wide range of pH (1-8.5) and temperatures (25-45 °C), indicating that the process developed in this study may have broad application potential in treatment of azo dyes contaminated wastewater.


Assuntos
Compostos Azo/química , Manganês/química , Benzenossulfonatos , Catálise , Corantes/química , Eletrólise , Peróxido de Hidrogênio/química , Ferro/química , Modelos Químicos , Nanocompostos , Oxirredução , Têxteis , Águas Residuárias/química
19.
Enzyme Microb Technol ; 135: 109507, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32146934

RESUMO

The azo dye Congo red is heavily used in textile industries and is actively present in the wastewater run-offs. Its structural complexity and physical characteristics make it resistant to the physicochemical treatments employed by the industry. Over time, application of the enzyme laccase has proved to be quite useful due to its ability to oxidize and eventually decolorize the dye. Moreover, the use of ABTS as the electron mediator also helps in enhancing the oxidizing capability of the enzyme with congo red. The present study involves establishing the role of the individual components i.e. laccase, ABTS and the dye, in the LMS electrochemically. Congo red doesn't have any form of electrochemical activity by itself, but the enzyme brings about a substantial change by increasing the rate of reduction. The effect of ABTS, though same, is concentration-dependent. For LMS, laccase helps in bringing about the rate of reduction much faster in the presence of the mediator, initiating the decolorization of the dye.


Assuntos
Vermelho Congo/metabolismo , Proteínas Fúngicas/metabolismo , Lacase/metabolismo , Trametes/metabolismo , Compostos Azo/química , Compostos Azo/metabolismo , Benzotiazóis/metabolismo , Biodegradação Ambiental , Proteínas Fúngicas/química , Cinética , Lacase/química , Ácidos Sulfônicos/metabolismo , Trametes/química , Trametes/enzimologia
20.
Chemosphere ; 244: 125588, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32050354

RESUMO

Fe@Fe2O3 core shell nanomaterials with different Fe2O3 shell thickness were synthesized and the Fe@Fe2O3/NaHSO3 Fenton-like system was used for the decomposition of Orange II. The consequences are compared with traditional Fenton Fe@Fe2O3/H2O2 system. The Fe@Fe2O3/NaHSO3 system showed extremely good applicability under both strongly acidic and alkaline conditions. The new Fe@Fe2O3-(2)/NaHSO3 system led to more than 99% degradation in 30 s when the pH was 3, which indicated that the Fe@Fe2O3 material was not corroded during the process even under strongly acidic condition. The above Fe@Fe2O3-(2) material was prepared from nano-zero-valent iron aged in solution for 2 h to synthesize the Fe2O3 shell. The reaction mechanism of Fe@Fe2O3/NaHSO3 Fenton-like system was also concluded. The oxidation efficiency was highly improved due to rapid electron transfer between Fe core and Fe2O3 shell, which promoted the direct recycling of ≡Fe3+ and ≡Fe2+ and thus accelerated the generation of SO4- and OH radicals.


Assuntos
Compostos Azo/química , Benzenossulfonatos/química , Modelos Químicos , Nanoestruturas/química , Peróxido de Hidrogênio/química , Ferro/química , Oxirredução , Sulfitos
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