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1.
Water Res ; 203: 117498, 2021 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-34371229

RESUMO

A novel design for a flow-electrode capacitive deionization (FCDI) system consisting of tubular electrodes in a shell and tube heat exchanger configuration is proposed. Each electrode consists of a metallic mesh current collector along the inner circumference of a tubular ion-exchange membrane. This tubular FCDI design is suitable for scale-up as it consists of easily manufactured components which can be assembled in an array. An apparatus with 4 tubular electrodes with a large effective area (202.3 cm2) was constructed and shown to provide a high net salt (NaCl) removal rate (0.15 mg s-1 at 1.2 V applied voltage and ∼2000 mg L-1 influent total dissolved solids concentration). A computational fluid dynamics (CFD) model incorporating ion migration and transport mechanisms was developed to simulate the ion concentration and electrical potential profiles in the water channel. The results of CFD modelling highlighted the need to maximize regions of both high potential gradient and high hydraulic flow in order to achieve optimal salt removal. In brief, this study presents a new design approach for FCDI scale-up and provides a computational tool for optimization of this design and future innovative FCDI designs.


Assuntos
Purificação da Água , Adsorção , Eletricidade , Eletrodos , Troca Iônica , Cloreto de Sódio
2.
Water Res ; 203: 117547, 2021 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-34412015

RESUMO

In flow anode systems, surface-bound hydroxyl radicals (*OH) are generated at the solid-liquid interface of suspended particulate charge carriers at potentials well below that required for oxygen evolution as a result of water splitting. While these surface-bound radicals are powerful indiscriminant oxidants that often lead to complete mineralization of organic pollutants, the more selective process of direct electron transfer (DET) may also occur at the particle electrode interfaces and play a critical role in the degradation of some contaminants. In this study, we investigated DET processes in a flow anode system in which carbon black was utilized as the flow anode material and Pt, Ti, IrRu and IrTa meshes were used as the current collectors. The results indicate that the use of a carbon black flow anode enhanced the DET rate by 20 times at 1.0 V vs Ag/AgCl compared to the control experiment with no carbon black particles present. Low solution conductivity had a more obvious negative effect on the DET process (compared to *OH mediated oxidation) due to the high potential drop and inhibition of mass transfer processes at the solid-liquid interfaces of the anode particles. The DET rates were dependent on the particular anode current collector used (i.e., Ti, IrRu, IrTa or Pt mesh) with differences in rates ascribed to the electron transfer resistance of the current collectors in the flow anode system. Detailed investigation of the degradation of phenol in a flow anode system revealed that this widely studied contaminant could be degraded with an energy consumption of 3.08 kWh m-3, a value substantially lower than that required with other techniques. Results of this study provide a better understanding of the DET mechanism at the solid-solid and solid-liquid interfaces with these insights expected to benefit the design of flow anode materials and current collectors and lead to the improvement in performance of flow anode systems.


Assuntos
Fenol , Poluentes Químicos da Água , Eletrodos , Elétrons , Oxirredução , Fenóis , Poluentes Químicos da Água/análise
3.
Environ Sci Technol ; 55(10): 7015-7024, 2021 05 18.
Artigo em Inglês | MEDLINE | ID: mdl-33905246

RESUMO

This work proposed an innovative and energy-efficient Donnan Dialysis (DD) and Osmotic Distillation (OD) hybrid process for alkali-driven ammonium recovery from wastewater. The efficiency and feasibility of ammonium removal and recovery from synthetic and real wastewater using NaOH and waste alkali were investigated. Ammonium in the feed first transported across the cation exchange membrane and accumulated in the receiver chamber. It is then deprotonated as ammonia, passing through the gas permeable membrane and finally is fixed as ammonium salt in the acid chamber. Our results indicated that employing waste alkali (red mud leachate) as driving solution led to excellent ammonium recovery performances (recovery efficiency of >80%), comparable to those of NaOH solution. When the initial ammonium concentration was 5 and 50 mM, the waste alkali driven DD-OD process achieved acceptable NH4+-N flux density of 16.8 and 169 g N m-2 d-1, at energy cost as low as 8.38 and 2.06 kWh kg-1 N, respectively. Since this alkali driven DD-OD hybrid process is based on solute concentration (or partial pressure) gradient, it could be an energy-effective technology capable of treating wastewaters containing ammonium using waste alkali to realize nutrients recovery in a sustainable manner.


Assuntos
Compostos de Amônio , Destilação , Álcalis , Membranas Artificiais , Osmose , Diálise Renal , Águas Residuárias
4.
Environ Sci Technol ; 55(8): 4243-4267, 2021 04 20.
Artigo em Inglês | MEDLINE | ID: mdl-33724803

RESUMO

With the increasing severity of global water scarcity, a myriad of scientific activities is directed toward advancing brackish water desalination and wastewater remediation technologies. Flow-electrode capacitive deionization (FCDI), a newly developed electrochemically driven ion removal approach combining ion-exchange membranes and flowable particle electrodes, has been actively explored over the past seven years, driven by the possibility of energy-efficient, sustainable, and fully continuous production of high-quality fresh water, as well as flexible management of the particle electrodes and concentrate stream. Here, we provide a comprehensive overview of current advances of this interesting technology with particular attention given to FCDI principles, designs (including cell architecture and electrode and separator options), operational modes (including approaches to management of the flowable electrodes), characterizations and modeling, and environmental applications (including water desalination, resource recovery, and contaminant abatement). Furthermore, we introduce the definitions and performance metrics that should be used so that fair assessments and comparisons can be made between different systems and separation conditions. We then highlight the most pressing challenges (i.e., operation and capital cost, scale-up, and commercialization) in the full-scale application of this technology. We conclude this state-of-the-art review by considering the overall outlook of the technology and discussing areas requiring particular attention in the future.


Assuntos
Purificação da Água , Adsorção , Eletrodos , Troca Iônica , Cloreto de Sódio
5.
Water Res ; 194: 116939, 2021 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-33640752

RESUMO

It is critical to both effectively remove and recover phosphate (P) from wastewater given the wide-ranging environmental (i.e., preventing eutrophication and restoring water quality) and economic (i.e., overcoming P resource scarcity) benefits. More recently, considerable academic effort has been devoted towards harvesting P as vivianite, which can be used as a potential slow-release fertilizer and possible reagent for the manufacture of lithium iron phosphate (LiFePO4), the precursor in fabricating Li-ion secondary batteries. In this study, we propose an innovative P recovery process, in which P is first preconcentrated via a flow-electrode capacitive deionization (FCDI) device followed by immobilization as vivianite crystals in a fluidized bed crystallization (FBC) column. The effects of different operational parameters on FCDI P preconcentration performance and energy consumption are investigated. Results show that 63% of P can be removed and concentrated in the flow-electrode chamber with a reasonable energy requirement under optimal operating conditions. The FBC system resulted in immobilization of ~80% of P as triangular or quadrangular pellets, which were verified to be high-purity vivianite crystals by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) and extended X-ray absorption fine structure (EXAFS) spectroscopy. This study provides a pathway for efficient recovery of P as a value-added product (i.e., vivianite) from P-rich wastewaters.


Assuntos
Purificação da Água , Cristalização , Eletrodos , Compostos Ferrosos , Fosfatos
6.
Water Res ; 189: 116653, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-33232816

RESUMO

The recovery of phosphorus (P) from wastewaters is a worthy goal considering the potential environmental and economic benefits. Flow-electrode capacitive deionization (FCDI), which employs flowable carbon electrodes instead of the static electrodes used in conventional CDI, has been demonstrated to be a promising P recovery technology. FCDI outperforms CDI and other competitive technologies in a number of aspects including (i) large salt adsorption capacity and (ii) extremely high water recovery rate. In this study, magnetic (Fe3O4 impregnated) activated carbon particles were prepared and applied as FCDI electrodes. The magnetic carbon electrodes were found to have a strong affinity towards P, facilitating the selective adsorption of P to the magnetic particles through a ligand exhange mechanism. Continuous operation of the FCDI system could be achieved with only three minutes required to separate the electrode particles from the brine stream on application of an external magnetic field. A P-rich stream was produced on regeneration of the exhausted magnetic electrodes using alkali solution. We envision that the use of magnetic carbon enhanced flow-electrodes will pave the way for efficient operation of FCDI as well as the preferential recovery of P.


Assuntos
Fosfatos , Purificação da Água , Adsorção , Eletrodos , Compostos Férricos , Fenômenos Magnéticos
7.
Environ Sci Technol ; 54(19): 12539-12549, 2020 10 06.
Artigo em Inglês | MEDLINE | ID: mdl-32897064

RESUMO

The formation of vivianite (Fe3(PO4)2·8H2O) in iron (Fe)-dosed wastewater treatment facilities has the potential to develop into an economically feasible method of phosphorus (P) recovery. In this work, a long-term steady FeIII-dosed University of Cape Town process-membrane bioreactor (UCT-MBR) system was investigated to evaluate the role of Fe transformations in immobilizing P via vivianite crystallization. The highest fraction of FeII, to total Fe (Fetot), was observed in the anaerobic chamber, revealing that a redox condition suitable for FeIII reduction was established by improving operational and configurational conditions. The supersaturation index for vivianite in the anaerobic chamber varied but averaged ∼4, which is within the metastable zone and appropriate for its crystallization. Vivianite accounted for over 50% of the Fetot in the anaerobic chamber, and its oxidation as it passed through the aerobic chambers was slow, even in the presence of high dissolved oxygen concentrations at circumneutral pH. This study has shown that the high stability and growth of vivianite crystals in oxygenated activated sludge can allow for the subsequent separation of vivianite as a P recovery product.


Assuntos
Ferro , Fósforo , Compostos Ferrosos , Fosfatos , Esgotos , Eliminação de Resíduos Líquidos
8.
Int J Clin Exp Pathol ; 13(6): 1287-1299, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32661465

RESUMO

Oligoasthenospermia is one of the main causes of infertility in reproductive-age men. This study aimed to explore the feasibility of exogenous testosterone supplemental therapy (TST) for adult male rats with oligoasthenospermia model. The rats (n=40) were randomized equally into 4 groups: control group, model group, low-dose and high-dose groups (n=10, respectively). After establishment of an oligoasthenospermia model that was treated with glucosides of tripterygium wilfordii (GTWs), the low-dose and high-dose groups were treated with 2 testosterone undecanoate (TU) injections at doses of 7.5 mg and 15 mg for 8-week period (4-week intervals). Body weights, serum reproductive hormone levels, sperm measurements in the epididymis, and testis histology were monitored. The TU injections increased serum testosterone levels steadily. The epididymis sperm concentration and motility increased slowly in high dose group at 4-weeks whereas sperm measurements increased significantly in the TST groups at 8 weeks. In addition, exogenous TST increased the intra-testicular testosterone concentration somewhat and alleviated the testicular oxidative stress markers of Malondialdehyde (MDA) and level of GSH-PX (Glutathione Peroxidase) after 8 weeks treatment. The improvement of sperm and testicular function acted mainly by curbing mitochondrial apoptosis in the testis by modulation of Bcl-2, Bax, Caspase-3, and Caspase-9 expression. However, the results of immunohistochemistry and western blotting in the low-dose group were still lower than control values. TST at an appropriate dose within a period of 8 weeks was effective to stimulate spermatogenesis and alleviate inflammation, oxidative stress, and apoptosis through suppression of testis damage in this rat model of oligoasthenospermia.

9.
Water Res ; 181: 115917, 2020 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-32505888

RESUMO

Flow electrode capacitive deionization (FCDI) is a promising configuration for capacitive deionization due to its capability of continuous operation and achieving a relatively large salinity reduction. Due to the complexity of the multi-phase flow involved in FCDI, modeling FCDI system performance has been a challenge with no predictive FCDI model thus far developed. In this study, we developed an equivalent film-electrode (EFE) model for FCDI in which the flow electrodes are approximated as moving film electrodes that behave in a manner similar to conveyor belts. The EFE-FCDI model is validated using results from a series of FCDI experiments and then applied to elucidate the spatial variations of the key properties of the FCDI system and to resolve the contributions of different aspects of the system to energy consumption. The impact of activated carbon loading in the flow electrode and the feed and effluent target concentrations on the overall FCDI performance are also discussed based on model simulation. In summary, the EFE-FCDI model enhances our understanding of the system-level behavior of FCDI systems and can be employed for optimizing FCDI design and operation.


Assuntos
Cloreto de Sódio , Purificação da Água , Adsorção , Eletrodos , Salinidade
10.
Environ Sci Technol ; 54(8): 5227-5236, 2020 04 21.
Artigo em Inglês | MEDLINE | ID: mdl-32202775

RESUMO

Magnéli phase titanium suboxide, Ti4O7, has attracted increasing attention as a potential electrode material in anodic oxidation as a result of its high efficiency and (electro)chemical stability. Although carbon materials have been amended to Ti4O7 electrodes to enhance the electrochemical performance or are present as an unwanted residual during the electrode fabrication, there has been no comprehensive investigation of how these carbon materials affect the electrochemical performance of the resultant Ti4O7 electrodes. As such, we investigated the electrochemical properties of Ti4O7 electrodes impregnated with carbon materials at different contents (and chemical states). Results of this study showed that while pure Ti4O7 electrodes exhibited an extremely low rate of interfacial electron transfer, the introduction of minor amounts of carbon materials (at values as low as 0.1 wt %) significantly facilitated the electron transfer process and decreased the oxygen evolution reaction potential. The oxygen-containing functional groups have been shown to play an important role in interfacial electron transfer with moderate oxidation of the carbon groups aiding electron uptake at the electrode surface (and consequently organic oxidation) while the generation of carboxyl groups-a process that is likely to occur in long-term operation-increased the interfacial resistance and thus retarded the oxidation process. Results of this study provide a better understanding of the relationship between the nature of the electrode surface and anodic oxidation performance with these insights likely to facilitate improved electrode design and optimization of operation of anodic oxidation reactors.


Assuntos
Titânio , Poluentes Químicos da Água , Carbono , Eletrodos , Oxirredução
11.
Water Res ; 173: 115580, 2020 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-32065937

RESUMO

While flow-electrode capacitive deionization (FCDI), one of the most popular CDI variants, possesses a number of advantages over conventional fixed-electrode CDI (e.g., large salt adsorption capacity, high flow efficiency and convenient management of the electrodes), challenges remain in constructing and operating an FCDI system such that it can operate continuously. Here we achieve effective continuous removal of salt from a brackish feed stream using flowing carbon electrodes which are regenerated in a closed-loop manner by using our previously introduced integrated FCDI/MF strategy. The performance of the FCDI/MF system is characterized over a two week period of operation with key factors influencing the desalination performance identified. Results show that the FCDI/MF system is capable of continuously desalinating brackish water (∼2 g L-1) to portable levels (<0.5 g L-1) whilst sustaining an extraordinary water recovery rate (∼92%) and relatively low energy consumption (∼0.5 kWh m-3). No obvious deterioration in performance or membrane fouling was observed during the 14-day operation. While the carbon particles used in the flow electrode exhibited only a minor increase in oxygen-containing groups over the 14 days of operation, a significant reduction in particle size was observed, likely as a consequence of the high-frequency collisions and associated friction between particles that occurred in the FCDI/MF system. Further studies regarding flowable electrode optimization, cell configuration design and process modelling are needed in order to realize the scale-up and practical implementation of this emerging technology.


Assuntos
Purificação da Água , Adsorção , Eletrodos , Águas Salinas , Cloreto de Sódio
12.
Water Res ; 171: 115370, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31864131

RESUMO

This study investigated the fouling and scaling behaviors in a capacitive deionization (CDI) system in the presence of iron and natural organic matter (NOM). It was found that the salt adsorption capacity (SAC) significantly decreased when treating Fe-containing brackish water, with higher Fe concentrations leading to severer SAC reduction. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analysis demonstrated that Fe2O3 appeared to be the predominant foulant attached on the electrode surface, which was difficult to be removed via backwashing, indicating the irreversible property of the foulant. Further characterizations (e.g., N2 sorption-desorption isotherms, electrochemical impedance spectroscopy and cyclic voltammetry) revealed that the CDI electrodes suffered from obvious deterioration such as specific surface area loss, resistance increase and capacitance decline with the occurrence of Fe scaling. While the presence of NOM alleviated the Fe scaling through NOM-Fe complexing effects, NOM itself was found to have negative impacts on CDI desalination performance due to their strong interactions with the carbon electrodes.


Assuntos
Ferro , Purificação da Água , Adsorção , Capacitância Elétrica , Eletrodos
13.
Environ Sci Technol ; 54(2): 1177-1185, 2020 01 21.
Artigo em Inglês | MEDLINE | ID: mdl-31829572

RESUMO

Flow-electrode electrochemical desalination (FEED) processes (e.g., flow-electrode capacitive deionization), which use flowable carbon particles as the electrodes, have attracted increasing attention, holding the promise for continuous desalination and high desalting efficiency. While it is generally believed that carbon particles with abundant microporous and large specific capacitances (e.g., activated carbon, AC) should be ideal candidates for FEED electrodes, we provide evidence to the contrary, showing that highly conductive electrodes with low specific surface area can outperform microporous AC-based electrodes. This study revealed that FEED using solely high surface area AC particles (∼2000 m2 g-1, specific capacitance of ∼44 F g-1, average salt adsorption rate of ∼0.15 µmol cm-2 min-1) was vastly outperformed by electrodes based solely on low-surface area carbon black (CB, ∼70 m2 g-1, ∼0.5 F g-1, ∼0.75 µmol cm-2 min-1). Electrochemical impedance spectroscopy results suggest that the electrode formed by CB particles led to more effective electronic charge percolation, likely contributing to the improved desalination performance. In addition, we propose and demonstrate a novel operation mode, termed single cycle (SC), which greatly simplified the FEED cell configuration and enabled simultaneous charging and discharging. Using SC mode with CB flow electrodes delivered an increased average salt removal rate relative to the more traditional short-circuited closed cycle (SCC) mode, achieving up to 1.13 µmol cm-2 min-1. Further investigations demonstrate that up to 50% of energy input would be avoided when using CB flow electrodes operated under SC mode as compared to that of AC flow electrodes operated under SCC mode. In summary, the FEED process presented in this study provided an innovative and promising approach toward high-efficient and low-cost brackish water desalination.


Assuntos
Fuligem , Purificação da Água , Adsorção , Eletrodos , Águas Salinas
14.
Water Res ; 168: 115186, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31655437

RESUMO

Flow-electrode capacitive deionization (FCDI) is an attractive variant of CDI with distinct advantages over fixed electrode CDI including the capability for seawater desalination, high flow efficiency and easy management of the electrodes. Challenges exist however in increasing treatment capacity with this attempted here through use of a membrane stack configuration. By comparison of standardised metrics (in particular, average salt removal rate (ASRR), energy normalized removed salt (ENRS) and productivity), results show that that an FCDI system with two pairs of ion exchange membranes had the highest efficiency in desalting a brackish influent (1000 mg L-1) to potable levels (∼150 mg L-1) at higher ASRR and ENRS. Further increase in the number of membrane pairs resulted in a decrease in current efficiency, likely as a result of the dominance of electrodialysis. Results of this study provide proof of concept that (semi-)continuous desalination can be achieved in FCDI at high energy efficiency (13.8%-20.2%) and productivity (> 100 L m-2 h-1) and, importantly, provide insight into possible approaches to scaling up FCDI such that energy-efficient water desalination can be achieved.


Assuntos
Purificação da Água , Adsorção , Eletrodos , Troca Iônica , Cloreto de Sódio
15.
Environ Sci Technol ; 53(23): 13859-13867, 2019 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-31687806

RESUMO

While flow-electrode CDI is a promising desalination technology that has major advantages when the electrodes are operated in the short-circuited closed-cycle (SCC) mode, little attention has been paid to the water recovery rate, which, in the SCC mode, is determined by the need for partial replacement of the saline electrolyte of the flow electrodes. Results of this study show that an extremely high water recovery rate of ∼95% can be achieved when desalting a 1000 mg NaCl L-1 brackish influent to a potable level of 150 mg L-1. The improved performance with regard to the electrical cost is related, at least in part, to the alleviated concentration polarization at the membrane/electrolyte interface during electrosorption. In effect, the current efficiency decreases with an increase in the water recovery rate. This finding is ascribed to inevitable co-ion leakage since the flow electrodes reject ions with the same charge. In addition, water transport across the ion exchange membranes also influences the water recovery rate. The effect of partial replacement of the saline electrolyte during (semi-)continuous operation requires particular consideration because the associated dilution of the carbon content in the flow electrodes results in a decrease in process performance.


Assuntos
Purificação da Água , Água , Adsorção , Eletrodos , Troca Iônica
16.
Environ Sci Technol ; 53(22): 13364-13373, 2019 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-31657549

RESUMO

Flow-electrode capacitive deionization (FCDI) is an emerging electrochemically driven technology for brackish and/or sea water desalination with merits of large salt adsorption capacity, high flow efficiency, and easy electrode management. While FCDI holds promise for continuous operation, there are very few investigations with regard to the regeneration/reuse of flowable electrodes and the separation of brine from electrodes with these operation prerequisites for real nonintermittent water desalination. In this study, we propose a novel module design to achieve these critical steps involving integration of an FCDI cell and a ceramic microfiltration (MF) contactor. Our investigations reveal that the brine discharge rate is the dominant factor for stable and efficient operation of the integrated module. Results obtained show that the integrated FCDI/MF system can be used to successfully separate brackish water (of salinities 1, 2 and 5 g L-1) into both a potable stream (<0.5 g L-1) and a brine stream (concentrated by 2-20 times) in a continuous manner with extremely high water recovery rates (up to 97%) and reasonable energy consumption. Another notable characteristic of the integrated system is the high thermodynamic energy efficiency (∼30%) with such efficiencies 4-5 times larger than those of conventional capacitive deionization units and comparable to reverse osmosis and electrodialysis systems achieving similar separation efficiencies. In brief, the results of studies described here indicate that continuous and efficient operation of FCDI is a real possibility and pave the way for scale-up of this emerging technology.


Assuntos
Purificação da Água , Adsorção , Eletrodos , Águas Salinas , Cloreto de Sódio
17.
Front Chem ; 7: 146, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30968014

RESUMO

While flow-electrode capacitive deionization (FCDI) operated in short-circuited closed cycle (SCC) mode appears to hold promise for removal of salt from brackish source waters, there has been limited investigation on the removal of other water constituents such as nitrate, fluoride or bromide in combination with salt removal. Of particular concern is the effectiveness of FCDI when ions, such as nitrate, are recognized to non-electrostatically adsorb strongly to activated carbon particles thereby potentially rendering it difficult to regenerate these particles. In this study, SCC FCDI was used to desalt source waters containing nitrate at different concentrations. Results indicate that nitrate can be removed from source waters using FCDI to concentrations <1 mg NO3-N L-1 though a lower quality target such as 10 mg L-1 would be more cost-effective, particularly where the influent nitrate concentration is high (50 mg NO3-N L-1). Although studies of the fate of nitrate in the FCDI system show that physico-chemical adsorption of nitrate to the carbon initially plays a vital role in nitrate removal, the ongoing process of nitrate removal is not significantly affected by this phenomenon with this lack of effect most likely due to the continued formation of electrical double layers enabling capacitive nitrate removal. In contrast to conventional CDI systems, constant voltage mode is shown to be more favorable in maintaining stable effluent quality in SCC FCDI because the decrease in electrical potential that occurs in constant current operation leads to a reduction in the extent of salt removal from the brackish source waters. Through periodic replacement of the electrolyte at a water recovery of 91.4%, we show that the FCDI system can achieve a continuous desalting performance with the effluent NO3-N concentration below 1 mg NO3-N L-1 at low energy consumption (~0.5 kWh m-3) but high productivity.

18.
J Air Waste Manag Assoc ; 69(1): 71-88, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30204538

RESUMO

Novel aerial methane (CH4) detection technologies were used in this study to identify anomalously high-emitting oil and gas (O&G) facilities and to guide ground-based "leak detection and repair" (LDAR) teams. This approach has the potential to enable a rapid and effective inspection of O&G facilities under voluntary or regulatory LDAR programs to identify and mitigate anomalously large CH4 emissions from a disproportionately small number of facilities. This is the first study of which the authors are aware to deploy, evaluate, and compare the CH4 detection volumes and cost-effectiveness of aerially guided and purely ground-based LDAR techniques. Two aerial methods, the Kairos Aerospace infrared CH4 column imaging and the Scientific Aviation in situ aircraft CH4 mole fraction measurements, were tested during a 2-week period in the Fayetteville Shale region contemporaneously with conventional ground-based LDAR. We show that aerially guided LDAR can be at least as cost-effective as ground-based LDAR, but several variable parameters were identified that strongly affect cost-effectiveness and which require field research and improvements beyond this pilot study. These parameters include (i) CH4 minimum dectectable limit of aerial technologies, (ii) emission rate size distributions of sources, (iii) remote distinction of fixable versus nonfixable CH4 sources ("leaks" vs. CH4 emissions occurring by design), and (iv) the fraction of fixable sources to total CH4 emissions. Suggestions for future study design are provided. Implications: Mitigation of methane leaks from existing oil and gas operations currently relies on on-site inspections of all applicable facilities at a prescribed frequency. This approach is labor- and cost-intensive, especially because a majority of oil and gas-related methane emissions originate from a disproportionately small number of facilities and components. We show for the first time in real-world conditions how aerial methane measurements can identify anomalously high-emitting facilities to enable a rapid, focused, and directed ground inspection of these facilities. The aerially guided approach can be more cost-effective than current practices, especially when implementing the aircraft deployment improvements discussed here.


Assuntos
Poluentes Atmosféricos/análise , Exposição Ambiental/prevenção & controle , Monitoramento Ambiental , Poluição Ambiental , Metano/análise , Indústria de Petróleo e Gás/normas , Ar/análise , Ar/normas , Aeronaves , Análise Custo-Benefício , Saúde Ambiental/métodos , Saúde Ambiental/normas , Monitoramento Ambiental/economia , Monitoramento Ambiental/métodos , Poluição Ambiental/análise , Poluição Ambiental/prevenção & controle , Recuperação e Remediação Ambiental/métodos , Humanos , Projetos Piloto
20.
Bioelectrochemistry ; 126: 72-78, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30529692

RESUMO

Electron transfer efficiency in electroactive biofilm is the limiting factor for bioelectricity output of bioelectrochemical system. Here, carbon felt (CF) is coated with manganese dioxide (MnO2) which acts as electron mediator in electroactive biofilm. A wrapping layer of conducting Poly 3,4-ethylenedioxythiophene is developed to protect the MnO2 and enhance electron transfer efficiency of MnO2 mediator. The hybrid bioanode (PEDOT/MnO2/CF bioanode) delivered the highest electron transfer efficiency (6.3 × 10-9 mol cm-2 s-1/2) and the highest capacitance of 4.78 F, much higher than bare CF bioanode (1.50 ±â€¯0.04 × 10-9 mol cm-2 s-1/2 and 0.42 F). As a result, microbial fuel cells could produce a maximum power density of 1534 ±â€¯13 mW m-2, approximately 57.7% higher than that with the bare carbon felt anode (972 ±â€¯21 mW m-2). Possible mechanisms are proposed to help understanding the different function of the PEDOT and MnO2 on the anodic layer. This study introduces an effective method for the fabrication of high performance anode.


Assuntos
Fontes de Energia Bioelétrica/microbiologia , Compostos Bicíclicos Heterocíclicos com Pontes/química , Eletricidade , Compostos de Manganês/química , Óxidos/química , Polimerização , Polímeros/química , Eletrodos , Transporte de Elétrons , Elétrons
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