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1.
Chemosphere ; 262: 128215, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33182126

RESUMO

The effluent from conventional treatment process (including anaerobic digestion and anoxic-oxic treatment) for pig farm wastewater was difficult to treat due to its low ratio of biochemical oxygen demand to chemical oxygen demand (BOD5/CODCr) (<0.1). In the present study, electro-Fenton (EF) was used to improve the biodegradability of the mentioned effluent and the properties of self-prepared CeO2-doped multi-wall carbon nanotubes (MWCNTs) electrodes were also studied. An excellent H2O2 production (165 mg L-1) was recorded, after an 80-min electrolysis, when the mass ratio of MWCNTs, CeO2 and pore-forming agent (NH4HCO3) was 6:1:1. Results of scanning electron microscopy (SEM), transmission electron microscope (TEM) and x-ray photoelectron spectroscopy (XPS) showed that addition of NH4HCO3 and the doping of CeO2 could increase the superficial area of the electrode as well as the oxygen reduction reaction (ORR) electro-catalytic performance. The BOD5/CODCr of the wastewater from the first stage AO process increased from 0.08 to 0.45 and CODCr reduced 71.5% after an 80-min electrolysis, with 0.3 mM Fe2+ solution. The non-biodegradable chemical pollutants from the first stage AO process were degraded by EF. The non-biodegradable pollutants identified by LC-MS/MS in the effluent from AO process including aminopyrine, oxadixyl and 3-methyl-2-quinoxalinecarboxylic acid could be degraded by EF process, with the removal rates of 81.86%, 34.39% and 7.13% in 80 min, and oxytetracycline with the removal rate of 100% in 20 min. Therefore, electro-Fenton with the new CeO2-doped MWCNTs cathode electrode will be a promising supplement for advanced treatment of pig farm wastewater.


Assuntos
Cério/química , Eletrólise/métodos , Nanotubos de Carbono/química , Águas Residuárias/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Animais , Biodegradação Ambiental , Análise da Demanda Biológica de Oxigênio , Catálise , Eletrodos , Fazendas , Peróxido de Hidrogênio/análise , Oxirredução , Suínos
2.
Chemosphere ; 254: 126899, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32957294

RESUMO

In this study, the reduction of iron-carbon internal electrolysis was reinforced by persulfate for p-nitrophenol removal. The effects of persulfate dosage, initial pH and iron-carbon mass ratio were comprehensively studied in batch experiments. In the system of iron-carbon internal electrolysis coupled with persulfate, the iron-carbon internal electrolysis and persulfate had a significant mutual influence, exhibiting a wide range of pH in the treatment process. Moreover, the coupled system also showed the remarkable removal and degradation efficiency of p-nitrophenol according to the contrast experiments. The satisfactory results should be attributed to the potential reduction of iron-carbon internal electrolysis, which was stimulated by persulfate to transform the nitro group to the amine group, accompanying the subsequent oxidation. Furthermore, persulfate possessed the ability that the dynamically destructive effect on external and internal of Fe0 and the scavenging action on activated carbon, effectively strengthening the potential energy for release and transfer of reductive substances. Both HO• and SO4•- as the main free radicals were formed to mineralize the intermediates in the coupled system. These findings indicate that the system of iron-carbon internal electrolysis coupled with persulfate can be a promising strategy for the treatment of the toxic and refractory wastewater.


Assuntos
Carvão Vegetal/química , Eletrólise/métodos , Ferro/química , Nitrofenóis/análise , Sulfatos/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Modelos Teóricos , Nitrofenóis/química , Oxirredução , Águas Residuárias/química , Poluentes Químicos da Água/química
3.
Biochem Biophys Res Commun ; 530(1): 1-3, 2020 09 10.
Artigo em Inglês | MEDLINE | ID: mdl-32828268

RESUMO

Alcohol-based disinfectant shortage is a serious concern in the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Acidic electrolyzed water (EW) with a high concentration of free available chlorine (FAC) shows strong antimicrobial activity against bacteria, fungi, and viruses. Here, we assessed the SARS-CoV-2-inactivating efficacy of acidic EW for use as an alternative disinfectant. The quick virucidal effect of acidic EW depended on the concentrations of contained-FAC. The effect completely disappeared in acidic EW in which FAC was lost owing to long-time storage after generation. In addition, the virucidal activity increased proportionately with the volume of acidic EW mixed with the virus solution when the FAC concentration in EW was same. These findings suggest that the virucidal activity of acidic EW against SARS-CoV-2 depends on the amount of FAC contacting the virus.


Assuntos
Betacoronavirus/efeitos dos fármacos , Cloro/farmacologia , Desinfetantes/farmacologia , Desinfecção/métodos , Inativação de Vírus/efeitos dos fármacos , Ácidos/química , Ácidos/farmacologia , Antivirais/química , Antivirais/farmacologia , Betacoronavirus/fisiologia , Cloro/química , Infecções por Coronavirus/prevenção & controle , Infecções por Coronavirus/virologia , Desinfetantes/química , Eletrólise/métodos , Humanos , Pandemias/prevenção & controle , Pneumonia Viral/prevenção & controle , Pneumonia Viral/virologia , Água/química , Água/farmacologia
4.
Chemosphere ; 258: 127325, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32540541

RESUMO

This study investigates the effectivenesses of electrocoagulation, ultrasound, and ultrasound-assisted electrocoagulation processes for the removal of color and chemical oxygen demand (COD) from aqueous dye solutions. The coupling of electrocoagulation processes with ultrasound has been found useful for water and wastewater treatment in recent years. These experimental results demonstrate that ultrasound-assisted electrocoagulation processes provide greater color and COD removal than ultrasound or electrocoagulation processes alone. The optimum conditions for the combined process were found to be Fe-Fe-SS-SS/Al-Al-SS-SS (electrode connection type) in the monopolar electrode connection mode; 75 and 50 A m-2 (current density) for RR241 and DB 60, respectively, at a fixed frequency of 40 kHz; and an ultrasound power of 180 W in a 1 L aqueous solution. Under these optimum conditions, the color and COD removal efficiencies for an aqueous solution of 100 mg L-1 reached 99-99.9% and 100 - 100% for RR241 and DB 60, respectively. Complete removal was achieved for both COD and color by employing a combination of ultrasound-assisted electrocoagulation (US + EC) with only 4 min of electrolysis, while the traditional EC treatment achieved removal of approximately 87% of COD and 92% color for both dyes using the MP-P connection mode for 5 min. Conversely, ultrasound power alone removed approximately 34-60% of color and 30-36% of COD for RR241 and DB 60, respectively. Compared with the traditional EC treatment, the combination of ultrasound irradiation and electrocoagulation treatment significantly reduced electrode passivation and increased the removal of pollutants in shorter operation times.


Assuntos
Corantes , Resíduos Industriais/análise , Eliminação de Resíduos Líquidos/métodos , Análise da Demanda Biológica de Oxigênio , Cor , Eletrocoagulação/métodos , Eletrodos , Eletrólise/métodos , Concentração de Íons de Hidrogênio , Águas Residuárias , Água
5.
Chemosphere ; 258: 127368, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32554018

RESUMO

Boron-doped diamond (BDD) is an excellent electrode material. As the anode in an electrochemical degradation tank, BDD has been receiving widespread attention for the treatment of azo dye wastewater. In this study, electrochemical oxidation (EO) was applied to electrolyze reactive brilliant yellow X-6G (X-6G) using BDD as the anode and Pt as the cathode. To balance the degradative effects and power consumption in the electrolysis process, the effects of a series of operating parameters, including current density, supporting electrolyte, initial pH, reaction temperature and initial dye concentration, were systematically studied. The oxidative process was analyzed by color removal rate, and the degree of mineralization was evaluated by TOC. The optimal experimental parameters were finally determined: 100 mA cm-2, 0.05 M Na2SO4 electrolyte, pH 3.03, 60 °C, and an initial X-6G concentration of 100 mg L-1. As a result, color completely disappeared after 0.75 h of electrolysis, and TOC was removed by 72.8% after 2 h of electrolysis. In conclusion, the EO of a BDD electrode as an anode can be a potent treatment method for X-6G synthetic wastewater.


Assuntos
Compostos Azo/análise , Benzenossulfonatos/análise , Boro/química , Eletrólise/métodos , Águas Residuárias/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Diamante , Eletrodos , Oxirredução
6.
Chemosphere ; 251: 126674, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32359720

RESUMO

Dimensionally stable anodes (DSA) have been widely used to degrade organic compounds because these surfaces promote the electrogeneration of active chlorine species in the bulk of the solution, as well as in the vicinity of the anode when NaCl is used as supporting electrolyte. In this work, the nanoparticles synthesis of IrO2 and RuO2 was performed to obtain two types of DSA electrodes named Class I and II to degrade oxamic acid. For Class I and II DSA, the nanoparticles used were synthesized separately and in the same reaction medium, respectively. Electrolysis were carried out in an open cylindrical cell without division at 25 °C, DSAs were used as anodes and a stainless-steel electrode as cathode, both elements have a geometric area of 2.8 cm2 immersed in 0.05 mol L-1 of NaCl or Na2SO4 and a current density of 3 mA cm-2 was applied for 6 h. Active chlorine species generated in the absence of oxamic acid in NaCl were also detected and quantified through ion chromatography. In Na2SO4 there was no degradation of the compound, but in NaCl the oxamic acid concentration reaching 85% with Class I DSA. The same tendency is observed in mineralization, in which Class I DSA allowed reaching a CO2 transformation close to 73%. The difference in the results occurs because with Class I DSA, more hypochlorite is generated than with Class II and therefore there is a larger amount of oxidizing species in the solution that enables the degradation and mineralization of oxamic acid.


Assuntos
Irídio/química , Modelos Químicos , Ácido Oxâmico/química , Compostos de Rutênio/química , Cloro/análise , Eletrodos , Eletrólise/métodos , Nanopartículas , Oxirredução , Poluentes Químicos da Água/análise
7.
Chemosphere ; 256: 127139, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32470737

RESUMO

The existence of ß-naphthoxyacetic acid (BNOA) pesticide in water system has aroused serious environmental problem because of its potential toxicity for humans and organisms. Therefore, exploiting an efficient method without secondary pollution is extremely urgent. Herein, a promising Ti/PbO2-Co-Pr composite electrode has been successfully fabricated through simple one-step electrodeposition for efficiently electrocatalytic degradation of BNOA. Compared with Ti/PbO2, Ti/PbO2-Co and Ti/PbO2-Pr electrodes, Ti/PbO2-Co-Pr electrode with smaller pyramidal particles possesses higher oxygen evolution potential, excellent electrochemical stability and outstanding electrocatalytic activity. The optimal degradation condition is assessed by major parameters including temperature, initial pH, current density and Na2SO4 concentration. The degradation efficiency and chemical oxygen demand removal efficiency of BNOA reach up to 94.6% and 84.6%, respectively, under optimal condition (temperature 35 °C, initial pH 5, current density 12 mA cm-2, Na2SO4 concentration 8.0 g L-1 and electrolysis time 3 h). Furthermore, Ti/PbO2-Co-Pr electrode presents economic energy consumption and superior repeatability. Finally, the possible degradation mechanism of BNOA is put forward according to the main intermediate products identified by liquid chromatography-mass spectrometer. The present research paves a new path to degrade BNOA pesticide wastewater with Ti/PbO2-Co-Pr electrode.


Assuntos
Eletrólise/métodos , Glicolatos/química , Chumbo/química , Praguicidas/química , Titânio/química , Águas Residuárias/análise , Poluentes Químicos da Água/química , Análise da Demanda Biológica de Oxigênio , Eletrodos , Eletrólise/instrumentação , Galvanoplastia , Oxirredução , Óxidos/química , Sulfatos/química
8.
Chemosphere ; 251: 126364, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32443231

RESUMO

This study is among the first to systematically study the electrochemical reduction of nitrate on boron-doped diamond (BDD) films with different surface terminations and boron-doping levels. The highest nitrate reduction efficiency was 48% and the highest selectivity in the production of nitrogen gas was 44.5%, which were achieved using a BDD electrode with a hydrogen-terminated surface and a B/C ratio of 1.0%. C-H bonds served as the anchor points for attracting NO3- anions close to the electrode surface, and thus accelerating the formation of NO3-(ads). Compared to oxygen termination, hydrogen-terminated BDD exhibited higher electrochemical reactivity for reducing nitrate, resulting from the formation of shallow acceptor states and small interfacial band bending. The hydrophobicity of the hydrogen-terminated BDD inhibited water electrolysis and the subsequent adsorption of atomic hydrogen, leading to increased selectivity in the production of nitrogen gas. A BDD electrode with a boron-doping level of 1.0% increased the density of acceptor states, thereby enhancing the conductivity and promoting the formation of C-H bonds after the cathodic reduction pretreatment leading to the direct reduction of nitrate.


Assuntos
Boro/química , Técnicas Eletroquímicas , Diamante/química , Doping nos Esportes , Eletrodos , Eletrólise/métodos , Hidrogênio/química , Nitratos , Óxidos de Nitrogênio , Oxirredução , Oxigênio , Água
9.
J Phys Chem Lett ; 11(8): 2941-2948, 2020 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-32223169

RESUMO

A highly efficient CO2 electrolysis system could be created by introducing biomass oxidation as an alternative anodic reaction to the sluggish oxygen evolution reaction in a CO2-saturated and near-neutral electrolyte. Here, we successfully demonstrate anodic biomass oxidation by synthesizing 5 nm nickel oxide nanoparticles (NiO NPs). NiO NPs show a unique electrocatalytic activity for 5-hydroxymethylfurfural (HMF) oxidation under near-neutral conditions, exhibiting an anodic current onset (1 mA cm-2) at 1.524 V versus the reversible hydrogen electrode and a total Faradaic efficiency of ≤70%. Electrokinetic and in situ ultraviolet-visible spectroscopic analyses suggest that a redox active nickel hydroxide species is formed on the surface of NiO electrocatalysts during HMF oxidation, and this oxidation of Ni(II) hydroxide to Ni(III) oxyhydroxide could be the rate-determining step. This mechanistic study of biomass oxidation in a CO2-saturated electrolyte provides insight into constructing a highly efficient system for the paired electrolysis of CO2 reduction and biomass oxidation.


Assuntos
Biomassa , Dióxido de Carbono/química , Eletrólise/métodos , Eletrólitos/química , Nanopartículas Metálicas/química , Níquel/química , Dióxido de Carbono/metabolismo , Técnicas Eletroquímicas/métodos , Eletrólitos/metabolismo , Níquel/metabolismo , Oxirredução
10.
Chemosphere ; 250: 126225, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32114338

RESUMO

For the purification of heavy metal wastewater, internal micro-electrolysis (IME) was considered as an effective method but some disadvantage greatly restricts its application. Electrocatalytic internal micro-electrolysis (ECIME) fluidized bed using iron-carbon particles was proposed to avoid disadvantaging of IME. The principal aim of this study was to investigate the enhanced removal characteristics, mechanism, and kinetic behavior of Cu(II) that none clear before. ECIME reactor shows a better copper removal performance and depends much on the polarization of the external electric field (EEF). Both the reaction rate and removal efficiency of copper electrodeposition improved obviously. Noteworthy is more than 88.0% of Cu(II) in aqueous solutions was removed by enhanced electrodeposition, and only about 10.0% of Cu(II) was absorbed and flocculated through the in situ formed iron hydroxyl compounds. Through scanning electron microscopy (SEM) and electrochemical analysis, copper can effectively electrodeposition on the surface of iron-carbon particles in ECIME reactor and accordingly the enhanced mechanisms were proposed. 1) Iron-carbon particles of ECIME formation of microelectrodes with high surface potential, larger specific area, and active sites through electrode collision and repolarization. 2) Copper electrodeposition on the formed microelectrodes exhibited greater reduction peak potential, reaction overpotential and exchange current density, which influenced by the polarization voltage significantly. 3) The electrocatalytic environment tend to in situ generate iron polymer hydroxyl compounds help to further remove residual Cu(II). ECIME fluidized-bed has promised potential for heavy metal containing wastewater purification and metal recovery. In addition, the proposed reaction models will be useful for field application.


Assuntos
Cobre/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Técnicas Eletroquímicas/métodos , Eletrodos , Eletrólise/métodos , Ferro/química , Cinética , Metais Pesados/análise , Águas Residuárias/química , Água/análise , Poluentes Químicos da Água/análise
11.
Chemosphere ; 250: 126163, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32109696

RESUMO

Due to the potential threatening of antibiotics in aqueous environment, a novel electro-oxidation (EO) - electro-Fenton (EF) -persulfate (PS) system with the addition of peroxydisulfate and Fe2+ was installed for the degradation of cefotaxime. Ti/CNT/SnO2-Sb-Er with an ultra-high oxygen evolution potential (2.15 V) and enhanced electrocatalytic surface area was adopted as anode. The OH production and electrode stability test demonstrated great improvement in the electrochemical performances. Ni@NCNT cathode was tested with higher H2O2 generation by the presence of nitrogen functionalities due to the acceleration of electron transfer of O2 reduction. Experiment results indicated CNT and ErO2 modification increased the molecular and TOC removal of cefotaxime. Coupling processes of EO-EF and EO-PS both resulted in shorter electrolysis time for complete cefotaxime removal, however, the mineralization ability of EO-PS process was lower than EO-EF, which might result from the immediate vanishing of PS. Thus, a further improved treatment EO-EF-PS system achieved an 81.6% TOC removal towards 50 mg L-1 cefotaxime after 4 h electrolysis, under the optimal working condition Fe2+ = PS = 1 mM. The influence of current density and initial concentration on the performance of all processes was assessed. Methanol and tert-butanol were added in the system as OH and SO4- scavengers, which illustrating the mechanism of EO-EF-PS oxidizing process was the result of the two free radicals. Major intermediates were deduced and the degradation pathway of cefotaxime was analyzed. This research provides a potential coupling process with high antibiotic removal efficiency and effective materials for practical uses.


Assuntos
Cefotaxima/química , Poluentes Químicos da Água/química , Antibacterianos/química , Eletrodos , Eletrólise/métodos , Peróxido de Hidrogênio/química , Oxirredução , Titânio , Águas Residuárias/química , Água , Purificação da Água/métodos
12.
Chemosphere ; 247: 125813, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31951953

RESUMO

Heterogeneous electro-Fenton (HEF) is as an alternative to the conventional electro-Fenton (EF) process. HEF uses a solid phase catalyst, whereas EF employs a solubilized one. This implies that in HEF, material can be recovered through a simple separation process such as filtration or magnetic separation in HEF. HEF also has the advantage of not requires a previous pH adjustment, which facilitates working in a higher pH range. In this work, Fe, Cu and Fe/Cu bimetallic nanoparticles (Fe/Cu NPs) were synthesized, characterized and used for the degradation of Nafcillin (NAF). The effect of the adsorption and the anodic oxidation (AO-H2O2) process was tested to assess their influence on HEF. NAF adsorption did not exceed 24% of antibiotic removal and the AO-H2O2 process eliminated the total NAF after 240 min of electrolysis. Through the HEF process, the antibiotic was completely removed using Fe/Cu NPs after 7.0 min of electrolysis, while these NPs, mineralization reached 41% after 240 min. In this case, NAF degradation occurs mainly due to the generation of hydroxyl radicals in the BDD electrode, and the Fenton reaction with Fe and Cu NPs. The main organic intermediates produced during the degradation of NAF by HEF were identified allowing the proposal of degradation pathway. Finally, the antibiotic was also completely eliminated from a wastewater from slaughterhouse after 15 min of treatment by HEF and using Fe/Cu bimetallic NPs.


Assuntos
Cobre/química , Peróxido de Hidrogênio/química , Ferro/química , Nanopartículas Metálicas/química , Nafcilina/química , Antibacterianos/química , Catálise , Técnicas Eletroquímicas , Eletrólise/instrumentação , Eletrólise/métodos , Radical Hidroxila/química , Oxirredução , Águas Residuárias/química , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/química
13.
Chemosphere ; 243: 125456, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31995895

RESUMO

In this paper degradation of cytarabine drug has been studied through electrochemical oxidation process by using graphite electrode. The performance of graphite electrode on the degradation of cytarabine was evaluated by investigating the effects of key parameters: pH (3-9), current density (5-20 mA cm-2) and initial pollutant concentration (5-50 mg L-1) with 0.05 M NaCl as supporting electrolyte. Highest removal efficiency (98%) for 20 mg L-1 of initial cytarabine solution was attained within 60 min electrolysis at 10 mA cm-2. The increase in degradation rate of cytarabine was possibly because of the active chlorine species originated at anode during the electrolysis. Further, efficiency of the graphite electrodes was compared with a metal electrode (copper) and results showed that the cytarabine degradation was facilitated by the in-situ generated OH radicals. However, only 82% of cytarabine was removed after 60 min of reaction time at 15 mA cm-2. The scum of Cu2+ ions deposited on the anode surface inhibit the mass transfer among the cytarabine molecules and generated hydroxyl radicals. The kinetic study also suggests faster reaction rate at graphite (0.12 min-1) than copper (0.05 min-1) electrode. The increase in electrolyte concentration enhanced the degradation rate and decreased the energy consumption from 3.66 to 0.66 kWh m-3. Cytosine was identified as the major transformation product from the UV-Vis spectral analysis and LC-MS analysis. Further, total organic carbon analysis depicts that only 60% of the parent molecule was mineralized. Hence, graphite was found to be an efficient anode material as compared to copper for cytarabine degradation.


Assuntos
Citarabina/isolamento & purificação , Eletrólise/métodos , Grafite/química , Poluentes Químicos da Água/isolamento & purificação , Antineoplásicos/isolamento & purificação , Cloro , Eletrodos , Cinética , Oxirredução , Poluentes Químicos da Água/química
14.
J Biosci Bioeng ; 129(1): 67-76, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31445821

RESUMO

This study reports the fabrication of a new cathode electrode assembly using polyaniline (PANI) and graphene on a stainless steel mesh (SSM) as an alternative for the conventional expensive cathode of microbial electrolysis cells (MECs). With respect to the previous efforts to propose an efficient and cost-effective alternative for platinum (Pt) catalysts and cathode electrodes, the present study investigates the assessment of different catalysts to elucidate the potential of the modified SSM cathode electrode for larger-scale MECs. In the case of feeding dairy wastewater to the MEC, the maximum hydrogen production rate and COD removal were obtained by SSM/PANI/graphene cathode and had the values 0.805 m3 H2 m-3 anolyte day-1 and 82%, respectively, at the applied potential of 1 V. These values were only 20% and 7% lower than those of the MEC with Pt on the carbon cloth cathode, respectively. The coulombic efficiencies of SSM/Pt and SSM/PANI/graphene were seen to be 64.48% and 56.67%, respectively. It was also concluded that the fabrication cost of the modified cathode was 50% lower than the conventional cathodes with Pt on the carbon cloth. Finally, the evaluation of the modified cathode performance was achieved based on Fourier transform infrared spectroscopy, linear sweep voltammetry, scanning electron microscopy, and atomic force microscopy.


Assuntos
Bactérias/química , Eletrólise/métodos , Hidrogênio/química , Bactérias/metabolismo , Fontes de Energia Bioelétrica/microbiologia , Carbono/química , Catálise , Eletrodos , Eletrólise/instrumentação , Hidrogênio/metabolismo , Platina/química , Águas Residuárias/química , Águas Residuárias/microbiologia
15.
Chemosphere ; 238: 124543, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31450109

RESUMO

Nano micro-electrolysis materials (nMETs) have been used to degrade refractory pollutants in batch experiments. The reasonable formation mechanism of nMETs was given through DMXY digital biomicroscopy. Based on the kinetic data of Chlortetracycline (CTC) removal by nMETs in batch experiments, combined with the binomial distribution equation of CTC reduction by nano materials an experimental-scale fluidized bed (ESFB) was designed. The effects of CTC removal performance, pH and iron ion concentration were investigated. Under pure CTC solution environment, the experimental data showed that the average removal rates of CTC by nMET and nano micro-electrolysis material with loading copper (Cu-nMET) are 90.0% and 95.7% in ESFB, respectively. In the presence of nitrate, although the consumption of two kinds of nano-materials increased, their removal efficiencies of pollutants have 2.2%, 0.2% increase compared with the nitrate-free ESFB. At the same time, the CTC degradation pathway and the enhanced removal mechanism by Cu-nMET was proposed. Through microelectrolysis reaction, complexation reaction and the active substances produced, the intermediate products can be degraded completely to NH4+, CO2, H2O and so on. This study aims to provide a theoretical basis for the environmental application of nMETs.


Assuntos
Clortetraciclina/isolamento & purificação , Cobre/química , Eletrólise/métodos , Ferro/química , Nitratos/química , Poluentes Químicos da Água/isolamento & purificação , Clortetraciclina/análise , Clortetraciclina/química , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/química
16.
Chemosphere ; 238: 124671, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31473527

RESUMO

In this study, Fe/Cu, Fe/Al/Cu, Fe/Cu/C and Fe/Al/Cu/C internal electrolysis systems (IESs) were constructed and used to treat methylene blue dye (MB) wastewater. The effects of filler mass ratio, filler dosage, solution pH, reaction time and reaction temperature on COD removal were discussed, while the kinetics, thermodynamics and mechanism of COD removal were also investigated. The results showed that when the COD removal rates were basically the same, the reaction times of Fe/Al/Cu, Fe/Cu/C and Fe/Al/Cu/C IESs were shorter, and the filler dosages were lower. For the four systems, the appropriate pH was around 5, while the suitable reaction temperature was in the range of 20-25 °C. The COD removals of these four IESs were generally greater than 90%. The COD removal processes of the four systems could be better described by the improved pseudo-second-kinetic model, and the liquid film diffusion was the rate-controlling step. Moreover, the COD removal was a spontaneous and endothermic process. MB was degraded into inorganic substances in four steps. In addition, the FTIR characterization of the fillers before and after reaction suggests the four IESs have good stability.


Assuntos
Eletrólise/métodos , Azul de Metileno/química , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Adsorção , Eletrólise/normas , Cinética , Termodinâmica , Eliminação de Resíduos Líquidos/normas , Poluentes Químicos da Água/química
17.
Chemosphere ; 241: 125010, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31605993

RESUMO

In this study, electrochemical oxidation of Acid Orange 7 (AO 7) azo dye has been investigated using a Fe-doped PbO2 electrode. The degradation of AO 7 followed pseudo-first-order reaction kinetics. The removals of AO 7, chemical oxygen demand (COD) and total organic carbon (TOC) were 87.15%, 49.88% and 44.94% after 60 min of electrolysis at the optimal conditions (Na2SO4 concentration 0.1 M, initial pH 5, initial AO 7 concentration 100 mg L-1 and applied current density 20 mA cm-2), respectively. And the corresponding degradation rate constant was 0.035 min-1. The intermediates formed during electrochemical process were identified, and a possible degradation pathway was proposed, which was initiated by the oxidation of azo bond (-NN-), hydroxylation and substitution reaction of -NH2 and -SO3H under the attack of OH, and ended with the formation of mineralization products such as NH4+, NO3-, SO42-, CO2 and H2O. The toxicity of treated AO 7 solution towards Vibrio fischeri increased slightly at first and then rapidly reduced to non-toxicity with prolonging time. The results indicate that electrochemical oxidation of AO 7 using Fe-doped PbO2 electrode is a promising way.


Assuntos
Compostos Azo/química , Benzenossulfonatos/química , Técnicas Eletroquímicas/métodos , Eletrólise/métodos , Chumbo/química , Óxidos/química , Poluentes Químicos da Água/química , Análise da Demanda Biológica de Oxigênio , Eletrodos , Eletrólise/normas , Cinética , Oxirredução , Poluentes Químicos da Água/análise
18.
Chemosphere ; 240: 124912, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31574437

RESUMO

In this work, the combination of biological and electrochemical processes to mineralize oxyfluorfen has been studied. First, an acclimatized mixed-culture biological treatment was used to degrade the biodegradable fraction of the pesticide, reaching up to 90% removal. After that, the non-biodegraded fraction was oxidised by electrolysis using boron-doped diamond as the anode. The results showed that the electrochemical technique was able to completely mineralize the residual pollutants. The study of the influence of the supporting electrolyte on the electrochemical process showed that the trace mineral solution used in the biological treatment was enough to completely mineralize the oxyfluorfen, resulting in total organic carbon removal rates that were well-fitted by a first-order model with a kinetic constant of 0.91 h-1. However, the first-order degradation rate increased approximately 20% when Na2SO4 was added as supporting electrolyte, reaching a degradation rate of 1.16 h-1 with a power consumption that was approximately 70% lower.


Assuntos
Eletrólise/métodos , Éteres Difenil Halogenados/química , Éteres Difenil Halogenados/metabolismo , Poluentes Químicos da Água/química , Poluentes Químicos da Água/metabolismo , Reatores Biológicos/microbiologia , Boro , Diamante , Eletrodos , Eletrólise/instrumentação , Cinética , Oxirredução , Praguicidas/química , Praguicidas/metabolismo , Sulfatos/química , Eliminação de Resíduos Líquidos/métodos
19.
Chemosphere ; 244: 125455, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31790985

RESUMO

This paper studies the applicability of a novel laser-prepared mixed metal oxide (MMO-RuO2TiO2) anode in the photoelectrochemical degradation of clopyralid, a toxic and biorefractory herbicide. Results are compared to those obtained using the well-known boron-doped diamond (BDD) anode and demonstrate that, although the electrolysis with diamond is more effective than that obtained with the new electrode, the irradiation of UVC light makes the novel MMO material more effective in chloride media. It was explained in terms of the homolysis of hypochlorous acid/hypochlorite to form chloride and hydroxyl radicals. Photoelectrochemical degradation with MMO produced a marked synergistic effect in TOC removal, especially in the presence of chloride ions. On the contrary, for the BDD anode, at the tested conditions, antagonisms were found in both sulfate and chloride media. These important synergisms allows finding conditions in which the novel anode can be competitive with the BDD.


Assuntos
Herbicidas/química , Modelos Químicos , Ácidos Picolínicos/química , Boro , Cloretos , Diamante , Eletrodos , Eletrólise/métodos , Radical Hidroxila , Lasers , Luz , Oxirredução , Óxidos , Sulfatos
20.
Sci Rep ; 9(1): 19955, 2019 12 27.
Artigo em Inglês | MEDLINE | ID: mdl-31882630

RESUMO

There is increasing demand for safe and effective sanitizers for irrigation water disinfection to prevent transmission of foodborne pathogens to fresh produce. Here we compared the efficacy of pH-neutral electrolyzed oxidizing water (EOW), sodium hypochlorite (NaClO) and chlorine dioxide (ClO2) against single and mixed populations of E. coli, Listeria and Salmonella under a range of pH and organic matter content. EOW treatment of the mixed bacterial suspension resulted in a dose-dependent (<1 mg/L free chlorine), rapid (<2 min) and effective (4-6 Log10) reduction of the microbial load in water devoid of organic matter under the range of pH conditions tested (pH, 6.0, 7.0, 8.4 and 9.2). The efficacy of EOW containing 5 mg/L free chlorine was unaffected by increasing organic matter, and compared favourably with equivalent concentrations of NaClO and ClO2. EOW at 20 mg/L free chlorine was more effective than NaClO and ClO2 in reducing bacterial populations in the presence of high (20-100 mg/L) dissolved organic carbon, and no regrowth or metabolic activity was observed for EOW-treated bacteria at this concentration upon reculturing in rich media. Thus, EOW is as effective or more effective than other common chlorine-based sanitizers for pathogen reduction in contaminated water. EOW's other characteristics, such as neutral pH and ease of handling, indicate its suitability for fresh produce sanitation.


Assuntos
Desinfetantes/análise , Desinfetantes/química , Desinfecção/métodos , Antibacterianos/análise , Antibacterianos/química , Cloretos/química , Cloro/química , Compostos Clorados/química , Eletrólise/métodos , Escherichia coli O157/crescimento & desenvolvimento , Manipulação de Alimentos/métodos , Listeria/crescimento & desenvolvimento , Oxirredução , Óxidos/química , Salmonella/crescimento & desenvolvimento , Hipoclorito de Sódio/química , Água/química , Purificação da Água/métodos
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