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1.
Sci Total Environ ; 711: 135087, 2020 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-32000338

RESUMO

Oxygen has not been purposely introduced to the autotrophic denitrification systems and simultaneous nitrification/autotrophic denitrification (SNAD) has not been proposed. In this study, oxygen was introduced into a micro-electrolysis-enhanced Fe0-supported autotrophic denitrification (mFe0AD) system. The nitrogen removal performance was investigated and the application potential of iron-scraps-supported simultaneous nitrification/mFe0AD was evaluated. The results showed that Fe0AD was surprisingly enhanced by oxygen together with nitrification at average dissolved oxygen (DO) of 0.08-1.56 mg/L. The ammonia oxidizing bacterial, nitrite oxidizing bacteria, facultative autotrophic denitrificans, and iron compounds transformation bacteria were markedly enriched. Average denitrification rate shifted from 0.116 to 0.340 kg N/(m3·d) with increase of average total nitrogen removal efficiency from 31.4% to 90.5%. Oxygen could enhance the biological conversion and storage of iron compounds, which was capable of reducing the coating of Fe0 surface.The accelerating of oxygen on  Fe0 passivation appeared when increasing the average DO from 1.56 to 2.17 mg/L. Therefore, the SNAD was recommended to be operated at the DO range of 0.08-1.56 mg/L. ME significantly enhanced Fe0AD, and the utilization of iron-scraps reduced its cost. The denitrification rate is comparable with methanol supported heterotrophic denitrification with 58.9% reduction on the cost. The iron-scraps supported SNAD is competitive in both denitrification rate and costs in the ammonia contaminated low-carbon water treatment.


Assuntos
Desnitrificação , Nitrificação , Reatores Biológicos , Eletrólise , Ferro , Nitrogênio , Oxigênio
2.
Bioresour Technol ; 302: 122761, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32004815

RESUMO

To further enhance the bio-photoelectrochemical system (BPES) performance for nitrofurazone (NFZ) degradation and current output, the g-C3N4/CdS photocathode was optimized, and microbial community shift from inoculation to the BPES was analyzed. Results showed that photocathode with g-C3N4/CdS (mass ratio of 1:9) loading of 7.5 mg/cm2 exhibited the best performance, with NFZ removal of 83.14% (within 4 h) and current of ~9 mA in the BPES. Proteobacteria accounted for the largest proportion: 66.53% (inoculation), 71.89% (microbial electrolysis cell (MEC) anode), 74.67% (BPES anode) and 57.31% (BPES cathode), respectively. In addition, Geobacter was the most dominant genus in MEC and BPES anode and cathode, which occupied 31.64%, 67.73% and 41.34%, respectively. The microbial compositions of BPES anode and cathode were similar, but different from that of MEC anode. Notably, Rhodopseudomonas, a photosynthetic species, was detected in the BPES. Cognition of microbial community in the BPES is important for advancing its development.


Assuntos
Fontes de Energia Bioelétrica , Microbiota , Eletrodos , Eletrólise , Nitrofurazona
3.
Bioresour Technol ; 302: 122874, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32007308

RESUMO

Pretreatment of microalgal biomass possessing rigid cell wall is a critical step for enhancing the efficiency of microalgal biorefinery. However, the conventional pretreatment processes suffer the drawbacks of complex processing steps, long processing time, low conversion efficiency and high processing costs. This significantly hinders the industrial applicability of microalgal biorefinery. The innovative electricity-aid pretreatment techniques serve as a promising processing tool to extensively enhance the release of intracellular substances from microalgae. In this review, application of electric field-based techniques and recent advances of using electrical pretreatments on microalgae cell focusing on pulsed electric field, electrolysis, high voltage electrical discharges and moderate electric field are reviewed. In addition, the emerging techniques integrating electrolysis with liquid biphasic flotation process as promising downstream approach is discussed. This review delivers broad knowledge of the present significance of the application of these methods focusing on the development of electric assisted biomolecules extraction from microalgae.


Assuntos
Microalgas , Biomassa , Parede Celular , Eletricidade , Eletrólise
4.
Bioresour Technol ; 303: 122958, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32058911

RESUMO

A coupled microbial electrolysis cell - anaerobic granular sludge system (MEC-AGS) was established to explore the degradation efficiency of 2,4,6-trichlorophenol (TCP) with synchronous biogas production. Results showed that MEC-AGS yielded a higher proportion of CH4 than MEC (83.8 ± 0.4% vs 82.0 ± 1.0%, P < 0.05) with sodium acetate (NaAc) as the only carbon source. Moreover, MEC-AGS had higher tolerance to the addition of TCP, with the highest TCP degradation efficiency of 45.5 ± 0.5% under 5 mg L-1 of TCP addition in 24 h. Furthermore, microbial community structures were significantly changed based on community composition, hierarchical cluster and PCoA analysis, which proved that MEC-AGS favored the enrichment of dechlorination-related microbes such as Pseudomonas, Desulfovibrio and Longilinea, as well as their syntrophic bacteria of Anaerolineacea, Syntrophobacter, Arcobacter, etc. The coupled system provides a promising strategy for biogas production from wastewater with recalcitrant organics.


Assuntos
Biocombustíveis , Esgotos , Anaerobiose , Reatores Biológicos , Clorofenóis , Eletrólise
5.
J Environ Manage ; 260: 110106, 2020 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-32090819

RESUMO

In this study, a new electrocoagulation electrode configuration has been investigated in order to induce dielectrophoretic (DEP) force for the enhanced harvesting of marine microalgae (Tetraselmis sp.). Asymmetrical aluminum electrodes with an alternative current power supply were used. The impact of electrode configuration, current density and electrolysis time were evaluated. A maximum algal harvesting efficiency of 90.9% was achieved using 7.1 mA/cm2 current density and 10 min electrolysis time. The energy consumption was found to be 4.62 kWh/kg of microalgae. The major significance of using the new electrode configuration was found in the aluminum content in the harvested biomass which decreased by 52% compared to the conventional symmetrical electrocoagulation electrodes.


Assuntos
Clorófitas , Microalgas , Alumínio , Biomassa , Eletrocoagulação , Eletrodos , Eletrólise
6.
Bioresour Technol ; 304: 122983, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32086038

RESUMO

Growing energy demands of wastewater treatment have made it vital for water companies to develop less energy intensive processes for treating wastewater if net zero emissions are to be achieved by 2050. Microbial electrolysis cells (MECs) have the potential to do this by treating water and producing renewable hydrogen gas as a product, but capital and operational costs have slowed their deployment. By using recycled carbon fibre mats, commercially viable MECs can brought closer to reality, where recycled carbon fibre anode MECs treating real wastewater (normalised ~3100 L d-1) were producing 66.77 L H2 d-1 while graphite felt anode MECs produced 3.65 L H2 d-1 per 1 m3 reactor, anodes costing £5.53 m-2 and £88.36 m-2 respectively, resulting in a total anode cost saving of 93%. This could incentivise the development of larger pilot systems, opening the door for generating greater value and a more sustainable wastewater treatment industry.


Assuntos
Fontes de Energia Bioelétrica , Fibra de Carbono , Eletrodos , Eletrólise , Hidrogênio , Águas Residuárias
7.
Bioresour Technol ; 304: 123000, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32088625

RESUMO

An increasing interest is devoted to combined microbial electrolysis cell-anaerobic digestion (MEC-AD) system which could convert waste activated sludge into biogas. In this study series tests were initially conducted to study the effect of alkaline pretreatment on AD system and the results showed that alkaline pretreatment could promote the dissolution of organic matters in the sludge and thus improve the methane production. Then, the methane production in combined MEC-AD system fed with alkaline-pretreated sludge was investigated. The results indicated that the methane productions increased by 37% and 42% when applied voltage was 0.5 V and 0.8 V. The microbial electrochemical system strongly promoted the growth of Euryarchaeota (Methanosaeta and Methanobacterium). Meanwhile, the abundance of Paraclostridium increased from 17.9% to 38.5% when applied voltage was 0.8 V, suggesting an enhanced fermentation and acetogenesis process. The results of energy balance estimation indicated that MEC-AD system at 0.5 V could achieve higher net energy output.


Assuntos
Reatores Biológicos , Esgotos , Anaerobiose , Eletrólise , Metano , Eliminação de Resíduos Líquidos
8.
Sci Total Environ ; 713: 136647, 2020 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-31955107

RESUMO

In this work, nine types of combination advanced oxidation processes/zero-valent iron (AOP-ZVI) were tested, in order to determine if any of these combinations demonstrate good chances as pretreatment for the biological degradation processes of organochlorinated pollutants. To do this, the changes undergone in the respirometric behavior, toxicity and short-term biodegradability were compared. The three AOPs studied were anodic oxidation with mixed metal oxides anodes (AO-MMO), with boron doped diamond anodes (AO-BDD) and photolysis and they were evaluated in three different modes: without any addition of ZVI, with ZVI-dehalogenation as pre-treatment and with ZVI-dehalogenation simultaneous to the AOP treatment. Clopyralid has been used as a model of chlorinated hydrocarbon pollutant. Results show that technologies proposed can successfully treat wastes polluted with clopyralid and the biological characteristics of the waste are significantly modified by dehalogenating the waste with ZVI, either previously to the treatment or simultaneously to the treatment, being the information provided by the three techniques very important in order to evaluate later combinations of the advanced oxidation technologies with biological treatments.


Assuntos
Eletrólise , Boro , Diamante , Eletrodos , Oxirredução , Fotólise
9.
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
10.
Environ Sci Technol ; 54(5): 3002-3011, 2020 03 03.
Artigo em Inglês | MEDLINE | ID: mdl-31891257

RESUMO

Nitrate-N in wastewaters is hard to be recovered because it is difficult to volatilize with an opposite charge to ammonium. Here, we have proved the feasibility of dissimilatory nitrate reduction to ammonia (DNRA) by the easy-acclimated mixed electroactive bacteria, achieving the highest DNRA efficiency of 44%. It was then coupled with microbial electrolysis to concentrate ammonium by a factor of 4 in the catholyte for recovery. The abundance of electroactive bacteria in the biofilm before nitrate addition, especially Geobacter spp., was found to determine the DNRA efficiency. As the main competitors of DNRA bacteria, the growth of denitrifiers was more sensitive to C/N ratios. The DNRA microbial community contrarily showed a stable and recoverable ammoniation performance over C/N ratios ranging from 0.5 to 8.0. A strong competition of the electrode and nitrate on electron donors was observed at the early stage (15 d) of electroactive biofilm formation, which can be weakened when the biofilm was mature on 40 d. Quantitative PCR showed a significant increase in nirS and nrfA transcripts in the ammoniation process. nirS was inhibited significantly after nitrate depletion while nrfA was still upregulated. These findings provided a novel way to recover nitrate-N using organic wastes as both electron donor and power, which has broader implications on the sustainable wastewater treatment and the ecology of nitrogen cycling.


Assuntos
Nitrogênio , Águas Residuárias , Desnitrificação , Eletrólise , Nitratos , Óxidos de Nitrogênio
11.
Bioresour Technol ; 297: 122429, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31791919

RESUMO

In this study, a process that combines iron-carbon micro-electrolysis (IC-ME) with the anammox process was successfully established for promoting nitrogen removal, especially the removal of nitrate by-product. Compared with the conventional anammox process, the average total nitrogen removal efficiency of the combined system increased from 64.6% to 90.2% and 83.8% when the system was effectively operated for 4 days (Phase 2) and 13 days (Phase 3), respectively. In this combined system, IC-ME played a dual role: 1) converting the nitrate to ammonia as the nitrogen substrate for further degradation, and 2) producing Fe2+, Fe3+ and H2 for the nitrogen removal processes of NH4+ oxidation with Fe3+ reduction (Feammox), nitrate-dependent Fe2+ oxidation (NDFO), and denitrification, in addition to the anammox process. Microbial analysis using 16S rRNA high-throughput sequencing revealed Candidatus Kuenenia and Candidatus Brocadia as the major anammox genera, accounting for 1.01% and 0.15%, respectively.


Assuntos
Desnitrificação , Nitrogênio , Reatores Biológicos , Eletrólise , Oxirredução , RNA Ribossômico 16S
12.
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
13.
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
14.
Water Res ; 168: 115144, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31605830

RESUMO

Bromide and natural organic matter (NOM) are both precursors of halogenated disinfection byproducts (DBPs) in drinking water. During drinking water treatment process, chloride-form anion-exchange resin adsorption is expected to be capable of removing these DBP precursors and in the meantime releasing chloride ions. The released chloride as well as the chloride initially present in source water could be oxidized through electrolysis to generate free chlorine for disinfection. Based on the above assumptions, we developed a new disinfection approach using chloride-form anion-exchange resin adsorption followed by electrolysis to control halogenated DBPs. Parameter setup and optimization were performed for resin adsorption and electrolysis processes. Results showed that 93.7% of NOM and 90% of bromide could be removed at a resin dose of 20 mL per 2 L of simulated source water sample with a contact time of 1 h. Meanwhile, 49.5 mg/L of chloride was released from the resin to the water sample via anion-exchange, and the released chloride was further oxidized by electrolysis (Ti/RuO2-IrO2 anode and graphite cathode, current intensity of 0.4 A) to generate free chlorine (5 mg/L as Cl2) within 192 s. With this new approach, formation of total organic halogen, four trihalomethanes, and five haloacetic acids was reduced by 86.4%, 98.5%, and 93.2%, respectively, compared with chemical chlorination alone. Although the new approach might enhance the formation of some phenolic DBPs by decreasing bromide levels in source water, the overall cytotoxicity of the water samples treated with the new approach was significantly decreased by 68.8% according to a human hepatoma cell cytotoxicity assay. Notably, disinfection ability evaluation showed that the new approach achieved 3.36-log10 reductions of three seeded bacteria (Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus) in 19 s, suggesting that it was not only effective to E. coli but also effective to the chlorine-resistant bacteria (P. aeruginosa and S. aureus).


Assuntos
Desinfetantes , Água Potável , Poluentes Químicos da Água , Purificação da Água , Adsorção , Desinfecção , Eletrólise , Escherichia coli , Halogenação , Humanos , Staphylococcus aureus
15.
Water Res ; 168: 115130, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31606555

RESUMO

Electrochemical systems have emerged as an advantageous approach for decentralized management of source-separated urine with the possibility of recovering or removing nutrients and generating energy. In this study, the kinetics and byproduct selectivity of the electrolytic removal of urea were investigated using a boron doped diamond working electrode under varied operational conditions with a primary focus on comparing undivided and divided reactors. The urea removal rate in the undivided and divided reactors was similar, but the divided reactor had an increased required cell voltage needed to maintain the equivalent current density. The current efficiency was similar for 0.1, 0.25, and 0.5 A (33.3, 83.3, 167 mA/cm2), suggesting no interference from competing reactions at higher potentials. In a divided reactor, increasing the anolyte pH reduced the urea removal rate presumably from hydroxyl radical scavenging by hydroxide. Further, for all divided reactor experiments, the final pH was less than 1, suggesting that the transport of protons across the ion exchange membrane to the cathode was slower than the oxidation reactions producing protons. The nitrogen byproduct selectivity was markedly different in the undivided and divided reactors. In both reactors, nitrate (NO3-) formed as the main byproduct at the anode, but in the undivided reactor it was reduced at the stainless steel cathode to ammonia. In the presence of 1 M chloride, the urea removal kinetics improved from the generation of reactive chlorine species, and the byproduct selectivity was shifted away from NO3- to presumably chloramines and N2. Overall, these results indicate that the electrochemical reactor configuration should be carefully considered depending on the desired outcome of treating source-separated urine (e.g., nitrogen recovery, H2 generation).


Assuntos
Boro , Diamante , Eletrodos , Eletrólise , Cinética , Nitrogênio , Oxirredução , Ureia
16.
Water Res ; 168: 115170, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31655435

RESUMO

Consumption of drinking water containing arsenic at concentrations even below the World Health Organization provisional limit of 10 µg/L can still lead to unacceptable health risks. Consequently, the drinking water sector in the Netherlands has recently agreed to target 1 µg/L of arsenic in treated water. Unfortunately, in many poor, arsenic-affected countries, the costs and complexity of current methods that can achieve <1 µg/L are prohibitive, which highlights the need for innovative methods that can remove arsenic to <1 µg/L without costly support infrastructure and complicated supply chains. In this work, we used Fe(0) electrolysis, a low cost and scalable technology that is also known as Fe(0) electrocoagulation (EC), to achieve <1 µg/L residual dissolved arsenic. We compared the arsenic removal performance of green rust (GR), ferric (oxyhydr)oxides (Fe(III) oxides) and magnetite (Mag) generated by EC at different pH (7.5 and 9) in the presence of As(III) or As(V) (initial concentrations of 200-11,000 µg/L). Although GR and Fe(III) oxides removed up to 99% of initial arsenic, neither Fe phase could reliably meet the 1 µg/L target at both pH values. In contrast, EC-generated Mag consistently achieved <1 µg/L, regardless of the initial As(V) concentration and pH. Only solutions with initial As(III) concentrations ≥2200 µg/L resulted in residual arsenic >1 µg/L. As K-edge X-ray absorption spectroscopy showed that Mag also sorbed arsenic in a unique mode, consistent with partial arsenic incorporation near the particle surface. This sorption mode contrasts with the binuclear, corner sharing surface complex for GR and Fe(III) oxides, which could explain the difference in arsenic removal efficiency among the three Fe phases. Our results suggest that EC-generated Mag is an attractive method for achieving <1 µg/L particularly in decentralized water treatment.


Assuntos
Arsênico , Poluentes Químicos da Água , Purificação da Água , Eletrólise , Compostos Férricos , Óxido Ferroso-Férrico , Países Baixos , Oxirredução
17.
Bioresour Technol ; 295: 122270, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31678890

RESUMO

Flexible control of CH4/H2 ratio in biohythane is important to its applications but remains a challenge. Herein, a dual-cathode bioelectrochemical system (BES) was developed for achieving biohythane production with controllable composition through adjusting external resistance. The BES was started as a microbial electrolysis cell to produce hydrogen in both cathodes ("H2-cathode") and then evolved to produce methane production in one cathode with inoculation of anaerobic sludge ("CH4-cathode"). When increasing the external resistance of the H2-cathode from 10 to 330 Ω, its H2 production decreased from 173 ±â€¯11 to 8 ±â€¯2 L m-3 d-1. This redistribution of electrons has benefited the CH4-cathode that had an increased CH4 production from 25 ±â€¯3 to 90 ±â€¯5 L m-3 d-1. The CH4/H2 ratio increased from 0.14 to 11, making biohythane more applicable to natural gas engines. Those results will help to formulate a BES-based approach to accomplish controllable biohythane production.


Assuntos
Hidrogênio , Metano , Eletrodos , Eletrólise , Esgotos
18.
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
19.
J Sci Food Agric ; 100(1): 184-192, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31472017

RESUMO

BACKGROUND: Slight acidic electrolyzed water (SAEW) has been widely used in cleaning systems of fruit and vegetables. It strongly reduces microbial contamination. However, no information is available on whether SAEW offers the potential for fresh jujube cleaning. The purposes of this study were, first, to compare the effectiveness of SAEW with commercial sanitizers (i.e. sodium hypochlorite (NaClO) or calcium hypochlorite (Ca(ClO)2 )) on 'Jiancui' jujube; second, to determine the response of fruit decay, tissue calcium (Ca) content, and quality attributes to dip application of calcium nitrate (Ca(NO3 )2 ) by concentration; and third, to investigate the effects of SAEW combined with Ca(NO3 )2 or calcium acetate (Ca(OAc)2 )) on fruit Ca uptake, quality attributes, and bioactive compounds. RESULTS: Fruits washed with NaClO, Ca(ClO)2 , or an SAEW solution showed no difference in reduction of decay incidence. In contrast to NaClO treatment, SAEW or Ca(ClO)2 significantly retarded losses in fruit firmness (FF), green color (hue angle), and skin lightness (L*), and maintained intact pericarp tissue structure during storage at 1 °C. Application of Ca(NO3 )2 at 5-10 g L-1 effectively promoted Ca2+ uptake and minimized declines in FF and L* value but had no effect on decay development. Adding 10 g L-1 Ca(NO3 )2 or Ca(OAc)2 to SAEW provided an additional benefit in increasing decay resistance, increasing Ca2+ into fruit and increasing levels of bioactive compounds in jujube fruit. CONCLUSION: SAEW in combination with Ca(NO3 )2 or Ca(OAc)2 has commercial potential for fresh jujube disinfection and improving storage quality as a result of the cleaning processes. © 2019 Society of Chemical Industry.


Assuntos
Acetatos/farmacologia , Compostos de Cálcio/farmacologia , Cálcio/análise , Conservação de Alimentos/métodos , Conservantes de Alimentos/farmacologia , Frutas/química , Nitratos/farmacologia , Ziziphus/efeitos dos fármacos , Eletrólise , Armazenamento de Alimentos , Frutas/efeitos dos fármacos , Controle de Qualidade , Água/química , Ziziphus/química
20.
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
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