Abstract:BackgroundBioelectrochemical systems (BESs) are capable of recovery of metals at a cathode through oxidation of organic substrate at an anode. Recently, also hydrogen gas was used as an electron donor for recovery of copper in BESs. Oxidation of hydrogen gas produced a current density of 0.8 A m‐2 and combined with Cu2+ reduction at the cathode, produced 0.25 W m‐2. The main factor limiting current production was the mass transfer of hydrogen to the biofilm due to the low solubility of hydrogen in the anolyte.… Show more
“…In electrochemical systems, usually inorganic substrates are oxidized, e.g., water can be oxidized to oxygen, protons, and electrons, or hydrogen can be oxidized to protons and electrons. In these electrochemical oxidation reactions, commonly, noble metal catalysts are used, although hydrogen oxidation can also be catalyzed by microorganisms (Ntagia et al 2016 ; Rodenas et al 2017 ). Fig.…”
Section: (Bio)electrochemical Systems For Tan Removalmentioning
confidence: 99%
“…Many industrial wastewaters as well as effluent streams from digesters have little to no biodegradable organic compounds present, where most of the biodegradable COD has already been converted into methane. In case too little biodegradable COD is available to recover all TAN, additional electron donor can be provided, for example by addition of extra biodegradable organic matter or through hydrogen gas recycling from the cathode to the bioanode (Ntagia et al 2016 ; Rodenas et al 2017 ; Kuntke et al 2017 ).…”
Section: Potential Wastewaters Streams For Ammonia Recovery In (B)esmentioning
In recent years, (bio)electrochemical systems (B)ES have emerged as an energy efficient alternative for the recovery of TAN (total ammonia nitrogen, including ammonia and ammonium) from wastewater. In these systems, TAN is removed or concentrated from the wastewater under the influence of an electrical current and transported to the cathode. Subsequently, it can be removed or recovered through stripping, chemisorption, or forward osmosis. A crucial parameter that determines the energy required to recover TAN is the load ratio: the ratio between TAN loading and applied current. For electrochemical TAN recovery, an energy input is required, while in bioelectrochemical recovery, electric energy can be recovered together with TAN. Bioelectrochemical recovery relies on the microbial oxidation of COD for the production of electrons, which drives TAN transport. Here, the state-of-the-art of (bio)electrochemical TAN recovery is described, the performance of (B)ES for TAN recovery is analyzed, the potential of different wastewaters for BES-based TAN recovery is evaluated, the microorganisms found on bioanodes that treat wastewater high in TAN are reported, and the toxic effect of the typical conditions in such systems (e.g., high pH, TAN, and salt concentrations) are described. For future application, toxicity effects for electrochemically active bacteria need better understanding, and the technologies need to be demonstrated on larger scale.
“…In electrochemical systems, usually inorganic substrates are oxidized, e.g., water can be oxidized to oxygen, protons, and electrons, or hydrogen can be oxidized to protons and electrons. In these electrochemical oxidation reactions, commonly, noble metal catalysts are used, although hydrogen oxidation can also be catalyzed by microorganisms (Ntagia et al 2016 ; Rodenas et al 2017 ). Fig.…”
Section: (Bio)electrochemical Systems For Tan Removalmentioning
confidence: 99%
“…Many industrial wastewaters as well as effluent streams from digesters have little to no biodegradable organic compounds present, where most of the biodegradable COD has already been converted into methane. In case too little biodegradable COD is available to recover all TAN, additional electron donor can be provided, for example by addition of extra biodegradable organic matter or through hydrogen gas recycling from the cathode to the bioanode (Ntagia et al 2016 ; Rodenas et al 2017 ; Kuntke et al 2017 ).…”
Section: Potential Wastewaters Streams For Ammonia Recovery In (B)esmentioning
In recent years, (bio)electrochemical systems (B)ES have emerged as an energy efficient alternative for the recovery of TAN (total ammonia nitrogen, including ammonia and ammonium) from wastewater. In these systems, TAN is removed or concentrated from the wastewater under the influence of an electrical current and transported to the cathode. Subsequently, it can be removed or recovered through stripping, chemisorption, or forward osmosis. A crucial parameter that determines the energy required to recover TAN is the load ratio: the ratio between TAN loading and applied current. For electrochemical TAN recovery, an energy input is required, while in bioelectrochemical recovery, electric energy can be recovered together with TAN. Bioelectrochemical recovery relies on the microbial oxidation of COD for the production of electrons, which drives TAN transport. Here, the state-of-the-art of (bio)electrochemical TAN recovery is described, the performance of (B)ES for TAN recovery is analyzed, the potential of different wastewaters for BES-based TAN recovery is evaluated, the microorganisms found on bioanodes that treat wastewater high in TAN are reported, and the toxic effect of the typical conditions in such systems (e.g., high pH, TAN, and salt concentrations) are described. For future application, toxicity effects for electrochemically active bacteria need better understanding, and the technologies need to be demonstrated on larger scale.
“…The balance between bubble breaking and coalescence is determined by the hydrodynamic force of impeller rotation in the presence of mixing aids, e.g., wall baffles, thus the designs of impeller and turbulence promoter 61 are critical in providing more uniform bubble size, and in turn the higher mass transfer rate, 62,63 e.g., mass transfer using either a dual impeller 64 or radial-axial impeller combination 65 was 15 to 35% higher in comparison to a single impeller. Mass transfer of a gas into a liquid has intensively been studied in STR, such as air in water, [66][67][68] H 2 in water, [69][70][71][72] O 2 in liquid hydrocarbons, 73 and in n-octacosane processes, 74 in fermentation vessels, 75 in gas-liquid-solid systems, [76][77][78] and in scale-up STRs. 79,80 Modeling of gas-liquid mass transfer 81 was performed using an Euler-Lagrange approach 82 and CFD.…”
Three-phase catalysis, for example, hydrogenation, is a special branch of chemical reactions involving a hydrogen reactant (gas) and a solvent (liquid) in the presence of a metal porous catalyst (solid) to produce a liquid product. Currently, many reactors are being used for three-phase catalysis from packed bed to slurry vessel; the uniqueness for this type of reaction in countless processes is the requirement of transferring gas into liquid, as yet there is not a unified system of quantifying and comparing reactor performances. This article reviews current methodologies in carrying out such heterogeneous catalysis in different reactors and focuses on how to enhance reactor performance from gas transfer perspectives. This article also suggests that the mass transfer rate over energy dissipation may represent a fairer method for comparison of reactor performance accounting for different types/designs of reactors and catalyst structures as well as operating conditions.
“…GDEs are already applied for different electrochemical reactions like the hydrogen oxidation reaction [5], nitrogen reduction reaction [6], oxygen reduction reaction (ORR) [7], and also the CO 2 RR [8]. Within a GDE, double-or triple-phase boundaries are formed (TPB) [9,10], where either all three phases are in direct contact with each other, or where extremely thin liquid layers (0.01-1 µm) [10] cover the catalyst material in the presence of the gaseous reactant [11].…”
Gas‐diffusion electrodes have been successfully employed in electrochemical chlorine production, and they also hold great potential in the field of electrochemical CO2 reduction. Herein, we demonstrate how sprayed Ag‐based gas‐diffusion electrodes, which show outstanding performance for the reduction of oxygen, need to be modified to produce CO from CO2. A computer‐controlled automated airbrush‐type spraying setup is used to systematically vary the core fabrication parameters of the process and investigate their effect on the electrochemical performance. Focused ion‐beam milling combined with scanning electron microscopy provides deeper insight into the structure of the electrodes and serves in combination with electrochemical data as the measure for the optimisation. Eventually, electrodes can be produced that suppress the evolution of H2 to the extent that an average Faradaic efficiency of 79% for CO can be maintained for at least 10 h at a current density of −100 mA∙cm−2.
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