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Fe(II)-catalyzed ferrihydrite transformation under anoxic conditions has been intensively studied, while such mechanisms are insufficient to be applied in oxic environments with depleted Fe(II). Here, we investigated expanded pathways of sunlight-driven ferrihydrite transformation in the presence of dissolved oxygen, without initial addition of dissolved Fe(II). We found that sunlight significantly facilitated the transformation of ferrihydrite to goethite compared to that under dark conditions. Redox active species (hole-electron pairs, reactive radicals, and Fe(II)) were produced from the ferrihydrite interface via the photoinduced electron transfer processes. Experiments with systematically varied wet chemistry conditions probed the relative contributions of three pathways for the production of hydroxyl radicals: (1) oxidation of water (5.0%); (2) reduction of dissolved oxygen (40.9%); and (3) photolysis of Fe(III)-hydroxyl complexes (54.1%). Results also showed superoxide radicals as the main oxidant for Fe(II) reoxidation under acidic conditions, thus promoting the ferrihydrite transformation. The presence of inorganic ions (chloride, sulfate, and nitrate) did not only affect the hydrolysis and precipitation of Fe(III) but also the generation of radicals via photoinduced charge transfer reactions. The involvement of redox active species and the accompanying mineral transformations would exert a profound effect on the fate of multivalent elements and organic contaminants in aquatic environments.

Thermally regenerative batteries (TRBs) is an emerging platform for extracting electrical energy from low-grade waste heat (T < 130 °C). TRBs using an ammonia-copper redox couple can store waste-he...

Capacitive deionization (CDI) has emerged as a promising technique for brackish water desalination. Here, composites of polypyrrole grafted activated carbon (Ppy/AC) were prepared via in situ chemical oxidative polymerization of pyrrole on AC particles. The Ppy/AC cathode was then coupled with a MnO2 anode for desalination in a membrane-free CDI cell. Both the Ppy/AC and MnO2 electrodes exhibited pseudocapacitive behaviors, which can selectively and reversibly intercalate Cl- (Ppy/AC) and Na+ (MnO2) ions. Compared to AC electrodes, the specific capacitances of Ppy/AC electrodes increased concurrently with the pyrrole ratios from 0 to 10%, while the charge transfer and ionic diffusion resistances decreased. As a result, the 10%Ppy/AC-MnO2 cell showed a maximum salt removal capacity of 52.93 mg g-1 (total mass of active materials) and 34.15 mg g-1 (total mass of electrodes), which was higher than those of conventional, membrane, and hybrid CDI cells. More notably, the salt removal rate of the 10%Ppy/AC-MnO2 cell (max 0.46 mg g-1 s-1 to the total mass of active materials and 0.30 mg g-1 s-1 to the total mass of electrodes) was nearly 1 order of magnitude higher than those in most previous CDI studies, and this fast and efficient desalination performance was stabilized over 50 cycles.

Thermally regenerative ammonia batteries (TRABs) show viable potential for harvesting abundant low-grade waste heat as high-power electricity. However, the ammonia brings about a large pH difference between the catholyte and anolyte, leading to self-discharge and severe energy decay. Here, an electrolyte decoupling strategy is proposed for ammonia batteries to restrain the self-discharge and enhance energy density as well as power generation at high temperatures. The self-discharge by ion cross contamination is observed visually as a colour evolution of the interlayer solution, and a transition of the principal cathodic reactant from Cu2+ to Cu(NH3)42+ exists during discharging, which signals the beginning of performance degradation. The results demonstrate that decoupled Cu/Zn-TRABs with double and triple-membrane designs improve the energy density by 45–50%, mainly due to the delay of the transition region. The power density of the decoupled Cu/Zn-TRABs is reduced at high currents, but with concentration optimization or elevated temperatures, it is able to be promoted significantly. With an energy density of 1034 W h m−3 obtained by a decoupled Cu/Zn-TRAB with double-IEM (ion exchange membrane) design, a thermoelectric conversion efficiency of 1.86% (15.6% relative to the Carnot efficiency) is achieved at a condenser temperature of 16 °C.

Resources in urine-containing wastewater are useful if recovered as nutrients. In this study, a three-chamber resource recovery microbial fuel cell (RRMFC) is proposed to treat synthetic urine-containing wastewater with various organic pollutants and recover N, P, and S nutrients. In the treatment, urea hydrolysis was increased by microbial and electrical processes. Ions migration driven by the self-generated electric field was used to recover nutrients from the wastewater. Over one cycle (∼3 days), 99% of urea, 97% of COD, 99% of histidine, 91% of creatinine, 99% of sodium acetate, 98% of SO42−, and 99% of PO43− were removed from the wastewater, and at the same time, 42% of total nitrogen, 37% of PO43−, 59% of SO42−, and 33% of total salts were recovered in the middle chamber. This technology is very attractive for sustainable resource recovery from urine-containing wastewater.

Environmental pollution and energy are interlinked; thereby an integrated approach is needed based on intra- and cross-disciplinary solutions. Microbial electro-Fenton, an innovative form of microbial electrochemical technologies, is an essential approach in this regard, which couples waste bioremediation and pollutant removal simultaneously from anode and cathode chambers with bioelectricity production. This article reviews the application of microbial electro-Fenton systems for environmental remediation and clean energy generation. Recent advances in fabrication of electrode materials to increase anodic biocompatibility and cathodic oxygen reduction reaction, cell design/configuration, membranes/separators and iron species as Fenton catalysts are discussed in detail. In addition, contemporary developments in the application of microbial electro-Fenton systems to deal with real wastewaters, wide variety of industrial pollutants and various classes of emerging contaminants are elucidated. Furthermore, the limitations and future perspectives are pointed out in detail. We believe that this in-depth review may aid as a reference guide for environmental scientists working on microbial electro-Fenton system.

Converting low-grade waste heat into electrical energy helps alleviate the increasingly tense energy crisis. Here, we present a feasible approach for low-grade waste heat recovery, called bimetallic thermally-regenerative ammonia-based flow battery (B-TRAFB), realizing high-voltage discharge and low-voltage charge at the same temperature. The performance of a cost-effective and structure-compact copper/zinc bimetallic thermally-regenerative ammonia-based battery (Cu/Zn-TRAFB) is investigated comprehensively. A peak power density of ∼280 W m−2 is achieved by a single Cu/Zn-TRAFB cell, and with this case, the net energy density is about 1280 Wh manolyte −3 with a thermoelectric conversion efficiency of 0.34% (2.7% of the Carnot efficiency). The power density obtained herein is much higher than those previously reported for ammonia-based batteries and other liquid-based heat-to-electricity technologies. The cell voltages, currents and power densities can be boosted by adding stacked cells in series or parallel. The energy conversion efficiency can be promoted to 1.64% (27% of the Carnot efficiency) by optimizing the thermal regeneration process.

With the steady development of modern society and economy, the requirements for intellectual property management of relevant enterprises are getting higher and higher. According to the enterprise intellectual property management of our country put forward normative analysis shows that the state intellectual property office, state administration of market supervision and management, the national standardization management committee in the draft for examination and approval, will this standard as enterprise intellectual property management system and management methods of important basis, provide strong support for enterprise sustainable development. Therefore, on the basis of understanding the development status of artificial intelligence technology and according to the construction and application of enterprise intellectual property management standard system in recent years, this paper deeply discusses the opportunities and challenges faced by enterprise intellectual property management standard system based on artificial intelligence, so as to provide effective basis for future enterprise technology research and development and application.

Background The widespread application of Polymyxin B, an active agent against multidrug resistance and extensive drug resistance Gram-negative bacteria, is majorly impeded by nephrotoxicity. Studies on the safety of polymyxin B in Chinese patients have not been widely reported. Objective This study aimed to explore the risk factors for polymyxin B-associated nephrotoxicity and guide its optimal place in therapy. Setting A tertiary care hospital located in eastern China. Methods This being a retrospective cohort study, we evaluated adult patients who received ≥ 72 h of polymyxin B therapy from January 2018 to December 2019. However, patients who received polymyxin B therapy for less than 3 days or received renal replacement therapy at baseline were excluded. Pertinent information was retrieved from medical records. All statistical analysis was performed in SPSS version 22.0. Main outcome measure(s) The main outcome measures included the proportion of patients who developed nephrotoxicity when subjected to polymyxin B treatment and the independent risk factors for nephrotoxicity. Results A total of 119 patients received polymyxin and met the overall inclusion criterion. Of the 119, 46 patients (38.7%) developed nephrotoxicity. Through multiple logistic regression analysis, we found three variables as independent risk factors for nephrotoxicity, including co-morbidities of malignancy (OR 4.55; 95% CI 1.44–14.41; P = 0.010), co-infection with other microorganisms (OR 4.15; 95% CI 1.48–11.63; P = 0.007), and polymyxin B daily dose (OR 1.02; 95% CI 1.00–1.03; P = 0.026). Conclusion This retrospective cohort study identified three risk factors for polymyxin B-associated nephrotoxicity therapy in Chinese patients. These include malignancy, co-infection with other microorganisms, and polymyxin B daily dose.

High cost platinum (Pt) catalysts limit the application of microbial electrolysis cells (MECs) for hydrogen (H

Residues and distribution of neonicotinoid insecticides (NEOs) in soil-water-sediment systems of the urban and rural areas of Guangzhou, South China were investigated. A total of 104 soil samples from 7 different functional zones and 29 water/sediment samples from creeks were collected. The results showed that at least one neonicotinoid insecticide was detected in all samples. The summed levels of five target neonicotinoids (∑5neonics) were in the range of 0.003–229 ng/g dw for soil samples, 7.94–636 ng/L for water samples, and 0.017–31.3 ng/g dw for sediment samples, with a geometric mean of 0.59 ng/g dw, 153 ng/L and 1.11 ng/g dw, respectively. Soils from agricultural areas contained the highest residual NEOs, followed by commercial, traffic, residential, industrial, educational zones and parks. Among the seven different functional zones studied, imidacloprid was the most dominant NEO in the agricultural areas and commercial zones, whereas acetamiprid was dominant in the other five functional zones with different land-use types. Thiamethoxam and acetamiprid were the main NEOs in water and sediment samples collected from 29 creeks. The pollution of NEOs in soils, water and sediments from rural areas was higher than that in the counterparts from urban areas. Residual concentration of NEOs detected in soils, water and sediments showed significant correlations with each other. The distribution of NEOs in soil-water-sediment systems indicated that NEOs tended to concentrate in water, followed by sediments and soils, especially in urban areas. An evaluation of the exposure to the current level of the ∑5NEOs in Guangzhou suggests a significant risk for aquatic and soil organisms, particularly under chronic exposures. The results of the present study offer valuable data to better understand the contamination and ecological risks of neonicotinoid insecticides in the rapidly developing urbanized region of South China.

The globally extractable salinity gradient (SG) energy from the mixing of seawater and river water is estimated to be 3% of worldwide electricity consumption. Here we applied carbonized peat moss (CPM) electrodes to a capacitive concentration flow cell that is capable of harvesting SG energy based on the capacitive double layer expansion (CDLE) together with the Donnan potential. The electrodes were made from the visually inexhaustible peat moss by a facile and environmental benign pyrolysis process. With two identical CPM electrodes and a cation-exchange membrane, the cell produced a peak power density of 5.33 W m−2 and an average power density of 950 mW m−2, the highest ever reported for CDLE-based techniques, using synthetic seawater (30 g L−1 NaCl) and river water (1 g L−1 NaCl). The excellent performance was a result of the macroporous structure of the CPM electrodes, the assistance of Donnan potential, and the double-channel structure of the cell. This system was durable as it could extract energy from highly saline water (300 g L−1 NaCl) and it still worked well after 100 cycles. This study provides a new method to efficiently and continuously harvest SG energy based on the CDLE without an external charge.

Rechargeable zinc ion batteries (ZIBs) featuring high abundance, environmental benignity, cost effectiveness, and intrinsic safety are regarded as high-potential grid energy storage systems, but the developments of high-performance cathodes with large capacity, high energy density, and long-term cyclability remain a huge challenge, owing to sluggish Zn2+ intercalation kinetics with bivalent charges in the cathodes. Herein, we report novel NH4V3O8·1.9H2O nanobelts as advanced cathode materials in aqueous and quasi-solid-state (QSS) ZIBs. When examined in aqueous ZIBs, these cathode materials enable ultrafast Zn2+ diffusion and highly reversible processes, exhibiting superior electrochemical performances with a high discharge capacity of 463 mA h g−1 at 0.1 A g−1, excellent rate capability (183 mA h g−1 even at 10 A g−1), and impressive cycling stability with a capacity retention of 81% after 2000 cycles, retaining a decent discharge capacity of 166 mA h g−1 at 10 A g−1. Moreover, the NH4V3O8·1.9H2O electrode can deliver a high energy density of 332 W h kg−1 at a power density of 72 W kg−1 and retain an energy density of 101 W h kg−1 at a high power density of 5519 W kg−1. In addition, the QSS flexible Zn/NH4V3O8·1.9H2O battery is investigated, showing durable cycling performance and stable electrochemical properties under various bending states. This study shows that the NH4V3O8·1.9H2O nanobelt cathode with high energy density and long cycle life is a potential candidate for grid energy storage systems, and it sheds light on the rational design of novel cathodes for practical rechargeable ZIBs.

A novel electrochemical system with corroding electrode of iron (Fec) inserted between boron-doped diamond (BDD) anode and carbon felt (CF) cathode, named BDD-Fec-CF system, was initially constructed and investigated in the present study. In this system, p-nitrophenol (p-NP) degradation was significantly enhanced in a wide pH range of 3–11 compared with BDD anode with CF cathode system (BDD-CF) and BDD anode with stainless steel (SS) cathode system (BDD-SS), respectively. Especially under acidic conditions, COD removal efficiency in BDD-Fec-CF system was achieved 89.1%, which was only 35.2% in BDD-SS system under the same conditions. The excellent performance under acidic conditions was mainly attributed to Electro-Fenton reaction. Hydroxyl radicals were formed by reaction between Fe2+ released from Fec electrode and H2O2 generated by dissolved oxygen reduction at CF cathode. Under alkaline conditions, flocs were formed to remove p-NP by coagulation besides anode oxidation, electro-generated oxidants and Fe(VI) oxidation. The fate of Fe was examined whose releasing rate was influenced by strength of electronic field and pH of solution. Under acidic conditions, Fe2+ released from Fec was oxidized into Fe3+ and then was absorbed and reduced at CF cathode. Under alkaline conditions, flocs were formed by reaction between Fe2+ and hydroxyl which came from oxygen reduction.

Rechargeable aqueous zinc-ion batteries are emerging as new promising energy storage devices for potential grid-scale applications, owing to their high safety and low cost. However, the limited choice of cathode materials and lack of green and scalable synthesis strategies have largely hindered their practical applications. Herein, a universal synthesis approach is developed to produce a variety of nanostructured layered vanadates, i.e., nanobelts of NaV3O8·1.35H2O (NVO), Zn3V2O8·1.85H2O (ZnVO), and KV3O8·0.51H2O (KVO), at room temperature. When examined as new cathodes for the zinc-ion battery system with aqueous ZnSO4 as electrolyte, all three nanobelts exhibit excellent electrochemical performances, particularly the NVO and ZnVO electrodes, delivering high specific capacities of 366 and 328 mAh g–1 at 0.1 A g–1, respectively. In addition, at an ultrahigh current density of 10 A g–1, the NVO shows an initial capacity of 186 mAh g–1 with retained capacity of 200 mAh g–1 after 200 cycles, while ZnVO provi...

Salinity gradient (SG) is a natural and renewable energy source existing in estuaries, and can also be produced during various desalination and industrial processes. Here, a new method is proposed to efficiently recover SG energy based on chloride-ion (Cl–) extraction and insertion with metal chloride electrodes and the Donnan potential over a cation-exchange membrane in a concentration flow cell. Three different metal chloride electrodes (BiCl3, CoCl2, and VCl3) were investigated in the cell, and their properties after discharging in 30 g L–1 (seawater) and 1 g L–1 (river water) NaCl solutions were studied by cyclic voltammetry, electrochemical impedance spectroscopy, and X-ray photoelectron spectroscopy. The cell with BiCl3 electrodes yielded the largest power density (max. = 3.17 W m–2) compared to that of CoCl2 and VCl3 electrodes, which was higher than those of most previous technologies for SG energy recovery. Fast Cl– extraction and insertion processes were observed on BiCl3 electrodes due to small...

Whereas electrochemical oxidation is noted for its ability to degrade bio-refractory organics, it has also been incorrectly criticized for excessive energy consumption. The present paper rectifies this misunderstanding by demonstrating that the energy actually consumed in the degradation process is much less than that wasted in the side reaction of oxygen evolution. To minimize the side reaction, the possible highest instantaneous current efficiency (PHICE) for electrochemical oxidation of phenol at Boron-doped Diamond (BDD), Ti/SnO2-Sb/PbO2 (PbO2), and Ti/SnO2-Sb (SnO2) anodes has been investigated systematically, and found to reach almost 100% at the BDD anode compared with 23% at the PbO2 anode and 9% at the SnO2 anode. The significant discrepancy between PHICE values at the various anodes is interpreted in terms of different existing forms of hydroxyl radicals. For each anode system, the PHICEs are maintained experimentally using a computer-controlled exponential decay current mode throughout the electrolysis process. For applications, the minimized energy consumption is predicted by response surface methodology, and demonstrated for the BDD anode system. Consequently, almost 100% current efficiency is achieved (for a relatively meagre energy consumption of 17.2 kWh kgCOD−1) along with excellent COD degradation efficiency by optimizing the initial current density, flow rate, electrolysis time, and exponential decay constant. Compared with galvanostatic conditions, over 70% of the energy is saved in the present study, thus demonstrating the great potential of electrochemical oxidation for practical applications.

A stationary and a transient two-dimensional models, based on the universal conservation laws and coupled with electrochemical reactions, are firstly applied to describe a single thermally-regenerative ammonia-based flow battery (TR-AFB), and emphasis is placed on studying the effects of reactant concentrations, physical properties of the electrolyte, flow rates and geometric parameters of flow channels on the battery performance. The model includes several experimental parameters measured by cyclic voltammetry (CV), chronoamperometry (CA) and Tafel plot. The results indicate that increasing NH3 concentration has a decisive effect on the improvement of power production and is beneficial to use higher Cu2+ concentrations, but the endurance of membrane and self-discharge need to be considered at the same time. It is also suggested that appropriately reducing the initial Cu(NH3)42+ concentration can promote power and energy densities and mitigate cyclical fluctuation. The relation between the energy and power densities is given, and the models are validated by some experimental data.

Low-grade heat from geothermal sources and industrial plants is a significant source of sustainable power that has great potential to be converted to electricity. The two main approaches that have been extensively investigated for converting low-grade heat to electrical energy, organic Rankine cycles and solid-state thermoelectrics, have not produced high power densities or been cost-effective for such applications. Newer, alternative liquid-based technologies are being developed that can be categorized by how the heat is used. Thermoelectrochemical cells (TECs), thermo-osmotic energy conversion (TOEC) systems, and thermally regenerative electrochemical cycles (TRECs) all use low-grade heat directly in a device that generates electricity. Other systems use heat sources to prepare solutions that are used in separate devices to produce electrical power. For example, low-temperature distillation methods can be used to produce solutions with large salinity differences to generate power using membrane-based systems, such as pressure-retarded osmosis (PRO) or reverse electrodialysis (RED); or highly concentrated ammonia solutions can be prepared for use in thermally regenerative batteries (TRBs). Among all these technologies, TRECs, TOEC, and TRBs show the most promise for effectively converting low-grade heat into electrical power mainly due to their high power productions and energy conversion efficiencies.

An enormous source of clean energy, called salinity gradient (SG) energy, exists from mixing waters with different salinities. Harvesting SG energy has attracted lots of attentions to develop efficient technologies. However, the power output is still limited. In this study, a concentration flow cell (CFC) powered by a bioelectrochemical system, defined as a bio-CFC, was proposed to recover SG energy from synthetic seawater (30 g/L NaCl) and river water (1 g/L NaCl) efficiently. The maximum power density of the bio-CFC reached 42 ± 2 W/m2, which was three times higher than that of a single CFC (10.6 ± 0.1 W/m2). The significant improvement was attributed to the additionally developed capacitive potential, which was formed by the bioelectrochemical currents from degradation of the organics in wastewater. The capacitive potential enhanced the Na+ intercalation/deintercalation on the electrodes and accelerated the Cl− transfer across the anion exchange membrane. This new strategy provides a promising way to recover energy from seawater and wastewater.

The influencing factors and formation of chlorinated byproducts in electrochemical oxidation of bisphenol A (BPA) with the boron-doped diamond (BDD) were systematically investigated using response surface methodology (RSM). The initial BPA concentration, chloride concentration, pH, and current density were studied as independent variables and the degradation rate of BPA ( k ), current efficiency (CE) and amount of Cl consumed (ΔCl) were selected as responses. The results showed that current density was the most influential factor on both k and ΔCl, and there were strong interactions between the influencing factors for all three responses, attributable to their effects on active chlorine, hydroxyl radicals and the state of BPA in this system. Based on the criteria of achieving the effective degradation of estrogenic BPA with relatively higher current efficiency and less generation of chlorinated byproducts, a final solution with 0.06 mM BPA and 40 mM NaCl (pH 8) and a current density of 15 mA cm −2 optimized through RSM was proved to give a BPA degradation rate of 0.318 min −1 , a CE of 54.93% and ΔCl of 3.55 mM. This showed great advantages compared with Pt anodes under the optimized conditions. The specific orientation of different forms of chlorine was also analyzed under different operation condition. Active chlorine, chloroform, and perchlorate showed similar variation trends with the operating factors. The amount of chlorine consumed in 240 min was 5.03 mM for BDD anode (while only 0.30 mM for Pt under similar conditions), indicating more varieties and amounts of chlorinated byproducts in the BDD system compared to Pt system due to its stronger oxidizing ability. This was further demonstrated through identification of different forms of chlorine and gas chromatography–mass spectrometry analysis. Besides generation of more perchlorate, chlorinated intermediates such as 1,1,2,2-tetrachloro-ethane, 2,2-bis(chloromethyl)-1-propanol, 1,1,1-tris(chloromethyl)-ethane, 2,3,4,6-tetrachloro-phenol, and pentachloro-phenol were specifically detected in the BDD cell. Although the entire toxicity of the whole BPA solution decreased obviously, the formation of these byproducts should be cautiously concerned during the electrolysis. Hereby, electrochemical oxidation should be conducted under lower current density in weakly alkaline electrolyte for actual water treatment projects polluted with organics and inevitable chloride ions.

Electrochemical oxidation of phenolic compounds using boron-doped diamond (BDD) anodes has been shown as an effective approach to remove these contaminants from water. However, the understanding of the reaction mechanisms of substituted phenolic compounds at the BDD anode remains incomplete. In the present work, we investigated the electrochemical oxidation of 12 representative phenolic compounds (with varied substitution groups (e.g., −CH3, −OCH3, −NH2, −Cl, −OH, −COOH, −NO2, −CHO) and positions (-ortho, -meta, and -para)) at the BDD anode. Our analysis shows that unlike previous studies the two parameters, the Hammett constants of the substituents and the highest atomic charge on the aromatic ring, fail to adequately describe the reaction rate change when the chemical structures become complicated (i.e., with increased steric effects). Instead, a quantitative structure–property relationship (QSPR) was established with 26 molecular descriptors and using a partial least-squares regression approach. The QS...

The bimetallic thermally-regenerative ammonia flow battery (B-TRAFB) has exhibited good potential in harvesting low-grade waste heat as high-power electricity, mainly due to its feature of high-voltage discharge and low-voltage charge in room temperature. Here, a 2-D flow and electrochemical coupled model is firstly constructed for a Cu/Zn-TRAFB, and validated with experimental results. We mainly focus on analysis of the influence of different working conditions and reactant concentrations on power and energy densities and thermoelectric conversion efficiency, as well as how the concentration distribution affects the battery performance. The results show that at low power output (~13 W m−2), the highest efficiency of 12.8% (81% relative to Carnot efficiency) can be achieved with an energy density of 17 kW h m−3 and a reactant concentration of 0.3 M. When generating ~70% of the peak power (~175 W m−2), the efficiency drops to ~3% (~20% relative to Carnot efficiency) with an energy density of ~ 4–5 kW h m−3. The depletion of reactant concentration on the electrode surface is the direct cause of performance degradation. Overall, this model framework we presented here is universally applicable to all kinds of B-TRAFBs and the formulation principles of discharge-charge strategy are given.

Salinity gradient energy can be directly converted into electrical power by using reverse electrodialysis (RED) and other technologies, but reported power densities have been too low for practical applications. Herein, the RED stack performance was improved by using 2,6-dihydroxyanthraquinone and ferrocyanide as redox couples. These electrolytes were then used in a flow battery to produce an integrated RED stack and flow battery (RED-FB) system capable of capturing, storing, and discharging salinity gradient energy. Energy captured from the RED stack was discharged in the flow battery at a maximum power density of 3.0 kW m-2 -anode, which was similar to the flow batteries charged by electrical power and could be used for practical applications. Salinity gradient energy captured from the RED stack was recovered from the electrolytes as electricity with 30 % efficiency, and the maximum energy density of the system was 2.4 kWh m-3 -anolyte. The combined RED-FB system overcomes many limitations of previous approaches to capture, store, and use salinity gradient energy from natural or engineered sources.

A new three-electrode electrocoagulation reactor was investigated to increase the rate of removal of phosphate from domestic wastewater. Initially, two electrodes (graphite plate and air cathode) were connected with 0.5 V of voltage applied for a short charging time (∼10 s). The direction of the electric field was then reversed, by switching the power supply lead from the anode to the cathode, and connecting the other lead to a sacrificial aluminum mesh anode for removal of phosphate by electrocoagulation. The performance of this process, called a reverse-electric field, air cathode electrocoagulation (REAEC) reactor, was tested using domestic wastewater as a function of charging time and electrocoagulation time. REAEC wastewater treatment removed up to 98% of phosphate in 15 min (inert electrode working time of 10 s, current density of 1 mA/cm2, and 15 min total electrocoagulation time), which was 6% higher than that of the control (no inert electrode). The energy demand varied from 0.05 kWh/m3 for 85% r...

Large differences between the water and air pressure in microbial fuel cells (MFCs) can deform and damage cathodes. To avoid deformation, the cathode air pressure was controlled to balance pressure differences between the air and water. Raising the air pressures from 0 to 10 kPa at a set cathode potential of −0.3 V (versus Ag/AgCl) enhanced cathode performance by 17%, but pressures ≥25 kPa decreased current and resulted in air leakage into the solution. Matching the air pressure with the water pressure avoided cathode deformation and improved performance. The maximum power density increased by 15%, from 1070 ± 20 to 1230 ± 70 mW m−2, with balanced air and water pressures of 10–25 kPa. Oxygen partial pressures ≥12.5 kPa in the cathode compartment maintained the oxygen reduction rate to be within 92 ± 1% of that in ambient air. The use of pressurized air flow through the cathode compartments can enable closer spacing of the cathodes compared to passive gas transfer systems, which could make the reactor design more compact. The energy cost of pressurizing the cathodes was estimated to be smaller than the increase in power that resulted from the use of pressurized cathodes.

Electrocoagulation (EC) can be used to remove nutrients as well as suspended solids and organic carbon from wastewaters, but the high energy requirements (pumping air) and the use of precious metals in some processes has hindered widespread application of EC technologies. The use of a thermodynamically favorable activated carbon air cathode and a sacrificial aluminum anode was examined to reduce the energy needed for EC for nutrient removal. Performance of the air cathode electrocoagulation (ACEC) process was tested using raw wastewater, and a carbon-free synthetic solution (nitrogen:phosphorus ratio of 1:10 in deionized water) to simulate nutrient removal of a wastewater treated for organic matter removal. ACEC treatment of wastewater removed up to 99% of both ammonia and phosphorus, along with 72–81% COD and 78–89% TSS in 4 h (1.5 cm electrode spacing, current density of 8 A m −2 ). Nearly total removal of the nutrients required 1.8 kWh m −3 , which is lower than that previously reported for some EC processes for this application (0.4–22 kWh m −3 ). Nutrient removals using synthetic solutions (no organic matter) ranged from 74% to 93% for nitrogen (47–370 mg-N/L) and 44–76% for phosphorus. These results indicate that the ACEC can achieve good levels of nutrient removal with reduced energy demands compared to previous EC systems.

Bimetallic thermally-regenerative ammonia batteries (B-TRABs) exhibit great potential in converting low-grade waste heat into electricity due to their high power and energy densities. However, there are still key issues such as self-discharge, low anode coulombic efficiency (ACE), and side reactions in ammonia batteries, which are not well explained but have a significant impact on performance. Here, we focus on the electrode reaction mechanism and give a universal construction criterion for the bimetallic thermally-regenerative batteries. The influence of oxygen on the electrode reactions of each process is explored, and a flow Cu/Zn-TRAB is developed to verify the electrochemical analysis. The root cause for affecting the ACE and oxygen effect are examined. The generation of self-discharge and its different effects are investigated for each electrode process. In addition, the influence of initial catholyte pH and temperature are discussed thoroughly. It is proposed to use the transition potential and pH to predict the occurrence of self-discharge. The results mainly indicate that the power production can be increased by 10–20% by removing oxygen from electrolytes. The stable existence of low-valence ions (e.g., Cu(NH3)4+) and the self-corrosion of ammonia on anode metals are the two main reasons for the low ACE. The self-discharge phenomenon is more serious in the discharge process because the reduction peak potential of Cu2+ is close to that of Cu(NH3)42+. The catholyte has the strongest ability to inhibit self-discharge at 40 °C, and the self-discharge occurs when the catholyte pH rises to ≈7–8.

Tremendous amount of fossil fuel is consumed in the form of low-grade waste heat (< 130 °C) due to inefficient energy utilization, and harvesting this waste heat as useful electricity contributes to mitigating the increasing energy crisis and the global greenhouse effect. Recently, compared with the past technologies (e.g. solid-state thermoelectric generator (s-TEG) and organic Rankine cycle (ORC)), liquid-based thermo-electrochemical batteries or systems feature more efficient and low cost for heat-to-electricity conversion. Among them, bimetallic thermally regenerative ammonia batteries (B-TRABs) based on redox reactions and ammonia thermal distillation that output the highest power density. However, all the existing ammonia batteries exhibit a common phenomenon that their discharge voltage curve basically has no stable platform and gradually decreases after peaking early, which is mainly due to the large pH difference between catholyte and anolyte, leading to self-discharge and severe energy decay. Here, an electrolyte decoupled strategy is proposed for a Cu/Zn-TRAB to restrain the self-discharge and enhance energy density as well as power generation at high temperatures. The self-discharge by ions cross contamination is observed visually as a colour evolution of the interlayer solution, and a transition of principal cathodic reactant from Cu(NH3)4 2+ to Cu2+ exists during discharging, which signals the beginning of performance degradation. The results demonstrate that the decoupled Cu/Zn-TRABs with double and triple-membrane designs improve the energy density by 45-50%, mainly due to the delay of transition region. With an energy density of 1034 W h m-3 obtained by a decoupled Cu/Zn-TRAB with double-membrane design, a thermoelectric conversion efficiency of 1.86% (15.6% relative to the Carnot efficiency) is achieved at a condenser temperature of 16 °C.