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1.
J Environ Manage ; 279: 111793, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-33360275

RESUMO

This paper provides a unique review of hydrogen production methods with wastewater treatment to depict a clean and sustainable approach. Various methods for hydrogen production from wastewaters are identified and discussed with recent details by discussing the critical challenges, opportunities, and future directions. Five main performance sectors are considered in detail for each hydrogen production method of the recent case studies, including economic, environmental, social, technical, and reliability. Eight hydrogen production methods are reviewed, including anaerobic method, photo fermentation, dark fermentation, electrolysis, electrodialysis, photocatalysis, photoelectrochemical methods, and super water gasification. A comparative assessment of six reviewed methods for hydrogen production, including environmental, economic, energetic, and exergetic impacts, is evaluated. The comparative assessment results indicate that dark fermentation technology is the most economical method, and it is followed by microbial electrolysis and photofermentation. The most environmentally friendly method for the lowest global warming potential (GWP) is the microbial electrolysis method, and it is followed by photocatalysis and photoelectrochemical methods. Furthermore, the highest energy and exergy efficiencies have been recorded for the microbial electrolysis to be 68% and 64.7%, respectively.


Assuntos
Hidrogênio , Águas Residuárias , Eletrólise , Fermentação , Reprodutibilidade dos Testes
2.
Sci Total Environ ; 757: 143746, 2021 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-33229085

RESUMO

This study reveals the efficient treatment of high strength food waste under varying hydraulic retention times (48 h, 36 h and 24 h) in a continuous stirred tank reactor (CSTR) integrated with microbial electrolysis cell (MEC) to become a continuous stirred microbial electrolysis cell (CSMEC). COD removal efficiency in the CSMEC surpassed 92% with OLR ranging from 0.4 to 21.31 kg COD/m3·d compared to that of the CSTR. The maximum current density (based on the cathode surface area) was 1125.35 ± 81 mA/m2 in the CSMEC. Biogas yield and methane production rates increased by 16.5% and 19.3% in the CSMEC respectively compared to the CSTR. CSMEC was 1.52 times better in performance compared to the CSTR. Firmicutes, Synergistetes, Bacteroidetes, Thermotogae, Chloroflexi and Proteobacteria were the dominant phyla associated with both CSMEC and CSTR. Archaeal microbial community analysis showed Methanosaeta, Methanobacterium, Methanosarcina and Methanocorpusculum as the dominant populations associated with the CSMEC.


Assuntos
Reatores Biológicos , Eliminação de Resíduos , Anaerobiose , Eletrólise , Características da Família , Alimentos , Metano
3.
Bioresour Technol ; 321: 124447, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33302007

RESUMO

In the current research, a novel bioreactor composed of porous polymer carriers and iron-carbon (PPC@FeC) was established through bacterial immobilized technology. The influence of key factors was studied on the nitrate removal performance of the PPC@FeC bioreactor. The experimental results showed that the highest removal rate of nitrate (7.33 mg L-1 h-1) can be obtained with short hydraulic retention times (HRT = 2.0 h) and low carbon-to-nitrogen ratio (C/N = 2.0). The results of high-throughput sequencing revealed that Zoogloea sp. L2 was the dominant strain in bioreactor responsible for nitrate removal. Moreover, the SEM and XRD analyses elucidated that Fe2O3 was the final product produced by the interaction of FeC and strain L2. These findings showed that the PPC@FeC bioreactor successfully combined micro-electrolysis and biological denitrification, which exhibited great potential in removing nitrate effectively from wastewater under low C/N ratio and short HRT conditions.


Assuntos
Nitratos , Águas Residuárias , Reatores Biológicos , Carbono , Desnitrificação , Eletrólise , Ferro , Nitrogênio , Polímeros , Porosidade
4.
Water Environ Res ; 93(1): 148-158, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32516457

RESUMO

Electrolysis of blackwater for disinfection and nutrient removal is a portable and scalable technology that can lessen the need for cities to construct large-scale wastewater treatment infrastructure and enable the safe onsite reuse of blackwater. Several systems for treating wastewater from single toilets are described in the literature, but there are few examples of systems designed to use electrolysis to treat blackwater from nearby toilets, which is a situation more common in densely packed urban living environments. In order to scale a single toilet electrolysis system to one that could service multiple toilets, computational fluid dynamic analysis was used to optimize the electrochemical reactor design, and laboratory and field-testing were used to confirm results. Design efforts included optimization of the reactor shape and mixing to improve treatment efficiency, as well as automated cleaning and salt injection to reduce maintenance and service requirements. PRACTITIONER POINTS: Design of a reverse polarity mechanism to enable in situ electrode cleaning and improve long-term electrode performance. Optimization of a hopper design and drainpipe location to collect and remove flaking precipitates and mitigate maintenance issues. Design of an automated salt injection system to guarantee sufficient chloride levels for producing adequate chlorine residuals for consistent disinfection.


Assuntos
Eliminação de Resíduos Líquidos , Águas Residuárias , Cidades , Desinfecção , Eletrólise
5.
J Environ Manage ; 279: 111597, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-33168294

RESUMO

This work aims to assess the influence of ultrasounds (US) application or ultraviolet (UV) light irradiation on the efficiency and sustainability of the treatment of wastes by conductive diamond electrochemical oxidation (CDEO). To do this, a life cycle assessment (LCA) is carried out in order to quantify the environmental impacts of the intensified CDEO processes. Inventories of three bench scale remediation plants (CDEO, Sono-CDEO and Photo-CDEO) in which the different technologies are implemented are performed by means of Ecoinvent 3.3 data base. AWARE, USEtox, IPPC and ReCiPe methodologies are used to quantify the environmental burden into 5 midpoint (water footprint, global warming 100a, ozone layer depletion, human toxicity, freshwater ecotoxicity) and 17 endpoint impact categories. Photo-CDEO attains the faster and more efficient removal in terms of energy consumed. All impact categories are lower in the case in which UV light irradiation is coupled to the CDEO treatment, particularly if the electrolyte does not contain chloride anions. From the point of view of toxicity and ecotoxicity, it is essential to achieve a complete mineralization, because of the intermediates generated into wastes containing chloride anions can become more hazardous than the initial pesticide. The operation of these technologies at large current densities shows positive results from the sustainability point of view, despite the huge environmental impact related to the energy production. Data notice that almost a 99.0% of the total global warming potential is mainly due to the electricity required during the electrochemical treatment, being higher by the sono and photo CDEO treatments because of the use of additional devices. Nevertheless, this issue can be overcome by means of using renewable energies as power sources of these remediation treatments. According to results, it can be claimed that the electrochemical technologies may successfully compete with other AOPs in terms of sustainability.


Assuntos
Eletrólise , Raios Ultravioleta , Diamante , Eletrólitos , Humanos , Oxirredução
6.
J Environ Manage ; 280: 111669, 2021 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-33234317

RESUMO

Electro-catalytic activities of carbonaceous cathodes including graphite plate, graphite felt, carbon felt, activated carbon felt (ACF) and carbon fiber felt (CFF) for degradation of Reactive Red X-3B (RRX-3B) in residual dyeing liquid were compared. The best electrochemical performance was obtained using dimensional stable anode (DSA) and CFF cathode due to the higher capacity for electro-generation of H2O2 by selective two-electron oxygen reduction. The CFF/DSA electrolysis system realized 78.2% COD removal and complete decolorization over a wide pH range. The efficacy of RRX-3B degradation was found to be dependent on the nature of carbonaceous materials. Electrochemical measurements showed that CFF possessed higher electrochemical surface area and hydrogen evolution reaction over-potential. Furthermore, the intrinsic graphitic N in CFF was proved to be catalytic active site by DFT calculations. Reactive Red X-3B degradation intermediates with benzene structures and carboxylic acids via hydroxylation in RRX-3B oxidation were identified by GC-MS. It was found that S/Cl/N-containing groups in RRX-3B molecule were mineralized to SO42-, NO3- and Cl- ions in the electrolysis.


Assuntos
Corantes , Poluentes Químicos da Água , Eletrodos , Eletrólise , Peróxido de Hidrogênio , Oxirredução , Poluentes Químicos da Água/análise
7.
Sci Total Environ ; 756: 144154, 2021 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-33310211

RESUMO

Inert gas is often used in the deoxygenation of microbial electrolysis cells (MECs) to maintain growth and viability of anaerobes. However, the effects of the gas atmosphere on hydrogen production and microbial community of MECs are often neglected. Here, the performances and biofilm microbiomes of MECs pre-sparged with different gases were compared. MECs pre-sparged with argon gas (Ar) yielded more hydrogen (3.73 ± 0.13 mol-H2/mol-acetate) and a higher hydrogen production rate (2.99 ± 0.17 L-H2/L-reactor-day) than MECs pre-sparged with N2 (3.41 ± 0.13 mol-H2/mol-acetate and 2.27 ± 0.28 L-H2/L-reactor-day, respectively). Microbiome analysis indicated that the relative abundance of Geobacter increased from 59.25% to 77.79% when the gas atmosphere in MECs shifted from N2 to Ar. Hydrogen production may have been catalyzed by nitrogenase from Geobacter and photosynthetic bacteria in MECs pre-sparged with Ar. These findings suggested that the gas atmosphere substantially influences the microbiome of anode biofilms and Ar sparging is most effective for enhancing hydrogen production in MECs.


Assuntos
Fontes de Energia Bioelétrica , Eletrólise , Atmosfera , Eletrodos , Gases , Hidrogênio
8.
Water Res ; 188: 116498, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-33080455

RESUMO

Complete biological denitrification is usually restricted in electron donor lacking waters. Hydrogenotrophic denitrification attracts attention for its clean and cost-efficiency advantages. Therein, the hydrogen could be effectively generated by microbial electrolysis cells (MECs) from organic wastes. In this study, a gas diffusion membrane (GDM) integrated MEC (MMEC) was constructed and provided a novel non-polluting approach for nitrate contaminated water remediation, in which the hydrogen was recovered from substrate degradation in anode and diffused across GDM as electron donor for denitrification. The high overall nitrogen removal of 91 ± 0.1%-95 ± 1.9% and 90 ± 1.6%-94 ± 2.2% were respectively achieved in Ti-MMEC and SS-MMEC with titanium and stainless-steel mesh as cathode at all applied voltages (0.4-0.8 V). Decreasing applied voltage from 0.8 to 0.4 V significantly improved the electron utilization efficiency for denitrification from 26 ± 3.6% to 73 ± 0.1% in Ti-MMEC. Integrating MEC with GDM greatly improved TN removal by 40% under applied voltage of 0.8 V. The hydrogenotrophic denitrifiers of Rhodocyclaceae, Paracoccus, and Dethiobacter, dominated in MMECs facilitating TN removal. Functional denitrification related genes including napAB, nirKS, norBC and nosZ predicted by PICRUSt2 based on 16S rRNA gene data demonstrated higher abundance in MMECs.


Assuntos
Desnitrificação , Nitratos , Biofilmes , Reatores Biológicos , Eletrólise , Membranas , Nitrogênio , RNA Ribossômico 16S
9.
Chemosphere ; 263: 127914, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32822940

RESUMO

The MSWI fly ash (FA) is classified as hazardous waste and electrolytic manganese residue (EMR) as the harmful industrial waste. FA, water-washed FA (WFA), EMR and coal fly ash (CFA) were co-recycled to form lightweight MFCE ceramisites. The effects of FA, WFA and mixed MSWI fly ash on ceramisites were discussed. The approach to mixing FA and WFA increased the recycling amount of MSWI fly ash. The optimal mixture of 34.5% EMR, 24.1% CFA, 20.7% FA and 20.7% WFA sintered at 1160 °C for 12 min with a procedural heating rate (10 °C/min) and belonged to Class 800 artificial lightweight aggregate (GB/T 17431.1-2010); the quantity of MSWI fly ash in ceramisite was as high as 41.4%. Volatilization rates of Cd, Pb, Cu, Zn, Mn and Cr for ceramisite were higher 75.0, 24.2, 62.7, 133, 343 and 764% than FA respectively, attributed to the co-existence of chlorides and sulfates. The remained Zn, Cu, Pb, Mn and Cr were exchanged with Mg2+/Ca2+/Al3+ of diopside and wollastonite to form residual fractions. Our findings provided a feasibility method of co-recycling MSWI fly ash and electrolytic manganese residue to produce green lightweight aggregates.


Assuntos
Cinza de Carvão/química , Incineração , Manganês/química , Carbono , Carvão Mineral , Eletrólise , Íons , Metais Pesados/análise , Material Particulado , Eliminação de Resíduos , Resíduos Sólidos , Volatilização
10.
Water Res ; 188: 116575, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-33152589

RESUMO

Two methods were examined to improve methane production efficiency in anaerobic digestion (AD) based on adding a large amount of surface area using a single electrically conductive carbon brush, or by adding electrodes as done in microbial electrolysis cells (MECs) to form a hybrid AD-MEC. To examine the impact of surface area relative to electrodes, AD reactors were fitted with a single large brush without electrodes (FB), half a large brush with two electrodes with an applied voltage (0.8 V) and operated in closed circuit (HB-CC) or open circuit (HB-OC) mode, or only two electrodes with a closed circuit and no large brush (NB-CC) (equivalent to an MEC). The three configurations with a half or full brush all had improved performance as shown by 57-82% higher methane generation rate parameters in the Gompertz model compared to NB-CC. The retained biomass was much higher in the reactors with large brush, which likely contributed to the rapid consumption of volatile fatty acids (VFAs) and therefore improved AD performance. A different microbial community structure was formed in the large-size brushes compared to the electrodes. Methanothrix was predominant in the biofilm of large-size carbon brush, while Geobacter (anode) and Methanobacterium (cathode) were highly abundant in the electrode biofilms. These results demonstrate that adding a high surface area carbon fiber brush will be a more effective method of improving AD performance than using MEC electrodes with an applied voltage.


Assuntos
Reatores Biológicos , Eletrólise , Anaerobiose , Fibra de Carbono , Eletrodos , Metano
11.
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
12.
Bioresour Technol ; 319: 124168, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32992275

RESUMO

Hydrogen production was evaluated in two-chamber microbial electrolysis cells (MEC), where the chambers of the cell were separated using a new economical and environmentally friendly membrane made of poly (vinyl) alcohol/chitosan (PVA/CS). The MEC performance was compared to that of Nafion. The obtained results indicated that the MEC performance for hydrogen production did not show significant differences between the PVA/CS and Nafion membranes. MEC with PVA/CS showed the hydrogen production rate and hydrogen yield of 1277 ± 46 mL H2Lcat-1d-1 and 974 ± 116 mL H2 gacetate-1, respectively. The PVA/CS membrane allowed acetate removal that was 7% higher than that of Nafion due to the lower pH gradient and a lower voltage drop that increased the ion transfer across the membrane.


Assuntos
Quitosana , Eletrólise , Hidrogênio , Álcool de Polivinil , Cloreto de Polivinila
13.
Bioresour Technol ; 319: 124109, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33035866

RESUMO

From the perspective of energy saving in the operation of microbial electrolysis cell assisted anaerobic digester (MEC-AD), this study focused on developing an intermittent power supply scheme. The applied potential was switched off for 12 and 6 hours/day during the operation of a laboratory-scale MEC-AD system fed with glucose. The results from the operation under continuous applied potential served as the control. The overall biomethane generation and net energy income from the process were unaffected when the applied potential turned off for 6 hours/day. Both quantitative and qualitative analyses of microbial communities suggested that a balanced microbiome could be maintained under short-term switching-off the applied potential. However, performance substantially deteriorated when the applied potential turned off for 12 hours/day. Overall, the results of this study suggest that MEC-AD operation does not need a continuous power supply, and higher energy efficiency can be effectively achieved by intermittently powering the reactor.


Assuntos
Reatores Biológicos , Metano , Anaerobiose , Fontes de Energia Elétrica , Eletrólise
14.
Bioresour Technol ; 319: 124182, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33038653

RESUMO

This work characterizes and comparatively assess two cation exchange membranes (PSEBS SU22 and CF22 R14) and one bipolar membrane (FBM) in microbial electrolysis cells (MEC), fed either by acetate or the mixture of volatile fatty acids as substrates. The PSEBS SU22 is a new, patent-pending material, while the CF22 R14 and FBM are developmental and commercialized products. Based on the various MEC performance measures, membranes were ranked by the EXPROM-2 method to reveal which of the polymeric membranes could be more beneficial from a complex, H2 production efficiency viewpoint. It turned out that the substrate-type influenced the application potential of the membranes. Still, in total, the PSEBS SU22 was found competitive with the other alternative materials. The evaluation of MEC was also supported by analyzing anodic biofilms following electroactive bacteria's development over time.


Assuntos
Fontes de Energia Bioelétrica , Eletrodos , Eletrólise , Ácidos Graxos Voláteis , Hidrogênio , Troca Iônica
15.
Bioresour Technol ; 319: 124056, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33038655

RESUMO

The related microbial metabolomics on biological recovery of manganese (Mn) from Electrolytic Manganese Slag (EMS) has not been studied. This study aimed at open the door to the metabolic characteristics of microorganisms in leaching Mn from EMS by using waste molasses (WM) as carbon source. Results show Microbacterium trichothecenolyticum Y1 (Y1) could effectively leach Mn from EMS in combination with using waste molasses as carbon and energy sources. For the first time, Y1 was identified to be capable of generating and then metabolizing several organic acids or other organic matter (e.g., fumaric acid, succinic acid, malic acid, glyoxylic acid, 3-hydroxybutyric acid, glutaric acid, L(+)-tartaric acid, citric acid, tetrahydrofolic acid, and L-methionine). The production of organic acids by Y1 bacteria was promoted by EMS with the carbon source. This study demonstrated for the first time that metabolic characteristics and carbon source metabolic pathways of Y1 in bioleaching of Mn from EMS.


Assuntos
Eletrólise , Manganês , Actinobacteria , Bactérias , Eletrólitos
16.
Bioresour Technol ; 320(Pt A): 124284, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33137640

RESUMO

Biohydrogen production in Microbial Electrolysis Cell (MEC) had inspired the researchers to overcome the challenges associated towards sustainability. Despite microbial community and various substrates, economical cathode catalyst development is most significant factor for enhancing hydrogen production in the MEC. Hence, in this study, the performance of MEC was investigated with a sugar industry effluent (COD 4200 ± 20 mg/L) with graphite anode and modified Nickel foam (NF) cathode. Nickel molybdate (NiMoO4) coated NF achieved a higher hydrogen production rate 0.12 ± 0.01 L.L-1D-1 as compared to control under favorable conditions. Electrochemical characterizations demonstrated that the improved catalytic activity of novel nanocatalyst with lower impedance favoring faster hydrogen evolution kinetics. The MEC with the novel catalyst performed with 58.2% coloumbic efficiency, 20.36% cathodic hydrogen recovery, 11.96% overall hydrogen recovery and 54.38% COD removal efficiency for a 250 mL substrate during 5 days' batch cycle. Hence, the potentiality of modified cathode was established with the real time industrial effluent highlighting the waste to wealth bio-electrochemical technology.


Assuntos
Fontes de Energia Bioelétrica , Níquel , Eletrodos , Eletrólise , Hidrogênio , Molibdênio , Açúcares
17.
Bioresour Technol ; 320(Pt A): 124314, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33147527

RESUMO

Hydrogen production from renewable resources via microbial electrolysis cells (MECs) is a promising approach for sustainable energy production. Yet high hydrogen yield from real feedstocks has not been demonstrated in up-scaled MECs. In this study, a 10-L single chamber MEC with a high electrode surface area to volume ratio (66 m2/m3) was constructed and electroactive cathodic biofilms were enriched for hydrogen evolution reaction. A high hydrogen yield of 91% was achieved using lignocellulosic hydrolysate with a hydrogen production rate of 0.71 L/L/D at an organic loading rate of 0.4 g/D. The anodic and cathodic microbial communities, with Enterococcus spp. as the known electroactive bacteria, were capable of achieving current densities of 13.7 A/m2 and 16.5 A/m2, respectively. A machine learning algorithm was used to investigate the correlation between community data and electrochemical performance, and the critical genera on determining current density were identified.


Assuntos
Fontes de Energia Bioelétrica , Eletrodos , Eletrólise , Hidrogênio , Lignina
18.
Bioresour Technol ; 320(Pt B): 124363, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33186801

RESUMO

Microbial electrolysis cell (MEC) technology is a promising bioelectrochemical hydrogen production technology that utilizes anodic bio-catalytic oxidation and cathodic reduction processes. MECs require a lower external energy input than water electrolysis; however, as they also require the application of external power sources, this inevitably renders MEC systems a less sustainable option. This issue is the main obstacle hindering the practical application of MECs. Therefore, this review aims to introduce a self-sustainable MEC technology by combining conventional MECs with advanced carbon-neutral technologies, such as solar-, microbial-, osmotic-, and thermoelectric-powers (and their combinations). Moreover, new approaches to overcome the thermodynamic barriers and attain self-sustaining MECs are discussed in detail, thereby providing a working principle, current challenges, and future perspective in the field. This review provides comprehensive insights into reliable hydrogen production as well as the latest trends towards self-sustainable MECs for practical application.


Assuntos
Fontes de Energia Bioelétrica , Carbono , Eletrodos , Eletrólise , Hidrogênio , Energia Renovável , Tecnologia
19.
Chemosphere ; 263: 128208, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33297167

RESUMO

The low concentration of nickel in electroplating wastewater is difficult to treat to meet the discharge standard. In this study, a commercial cation exchange membrane was used to combine the electrodialysis on a titanium plate anode sintered ruthenium-iridium and the electrodeposition on a stainless steel cathode to reduce the nickel concentration to less 0.1 mg L-1. The electrolytic properties of the electrodialysis combined with the electrodeposition were investigated at different cell voltages, electrolysis time, initial electrolyte pH, electrolyte flow rates and initial Ni2+ concentrations. The results indicated that the Ni2+ concentration in the anolyte and the catholyte could be reduced to 0.015 and 0.085 mg L-1, respectively, with the initial Ni2+ concentration of 1.0 mg L-1, which could meet the most strict Ni2+ discharge standard of 0.1 mg L-1. The electrodeposition of Ni2+ on the cathode enhanced the migration of the Ni2+ in the electrolytes, which was beneficial to decrease the energy consumption. Therefore, the combination of electrodialysis and electrodeposition was promising to reduce the low concentration of Ni2+ in the electroplating wastewater.


Assuntos
Galvanoplastia , Águas Residuárias , Eletrólise , Íons , Níquel/análise , Águas Residuárias/análise
20.
Environ Sci Technol ; 54(20): 13333-13343, 2020 10 20.
Artigo em Inglês | MEDLINE | ID: mdl-32931260

RESUMO

Electro-generated hydroxyl radicals (•OH) are of fundamental importance to the electrochemical advanced oxidation process (EAOP). Radical-specific electron spin resonance (ESR) evidence is still lacking in association with the direct electron transfer (DET) reaction of spin trap (e.g., 5,5-dimethyl-1-pyrroline-N-oxide; DMPO) and side reactions of the DMPO-OH adduct in the strongly oxidative environment offered by anodic polarization. Herein, we showed ESR identification of electro-generated •OH in EAOP based on the principle of kinetic selection. Excessive addition of a DMPO agent and fast spin trapping allowed suitable kinetic conditions to be set for effective spin trapping of electro-generated •OH and subsequent ESR identification. Otherwise, interferential triplet signals would emerge due to formation of paramagnetic dimer via dehydrogenation, DET oxidation, and dimerization reactions of the DMPO-OH adduct. The results demonstrate that •OH formation during spin-trapping on the titanium suboxide (TiSO) anode could be quantified as 47.84 ± 0.44 µM at current density of 10 mA cm-2. This value revealed a positive dependence on electrolysis time, current density, and anode potential. The effectiveness of ESR measurements was verified by the results obtained with the terephthalic acid probe. The ESR identification not only provides direct evidence for electro-generated •OH from a fundamental point of view, but also suggests a strategy to screen effective anode materials.


Assuntos
Óxidos N-Cíclicos , Radical Hidroxila , Eletrólise , Espectroscopia de Ressonância de Spin Eletrônica , Radicais Livres , Marcadores de Spin , Detecção de Spin
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