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Photocatalytic activity has been demonstrated for ZrSnO4 by controlling the bandgap and the bottom of the conduction band of ZrO2 and SnO2. A single-phase with the metastable ZrSnO4 solid was successfully obtained, and ZrSnO4 exhibited photocatalytic activity for hydrogen and oxygen production from water under UV irradiation. [ABSTRACT FROM AUTHOR]

Algal-bacterial symbiotic system, with biological synergism of physiological functions of both algae and bacteria, has been proposed for cultivation of microalgae in municipal wastewater for biomass production and wastewater treatment. The algal-bacterial symbiotic system can enhance dissolved oxygen production which enhances bacterial growth and catabolism of pollutants in wastewater. Therefore, the oxygen production efficiency of microalgae in algal-bacterial systems is considered as the key factor influencing the wastewater treatment efficiency. In the present study, we have proposed a novel approach which uses static magnetic field to enhance algal growth and oxygen production rate with low operational cost and non-toxic secondary pollution. The performance of oxygen production with the magnetic field was evaluated using Scenedesmus obliquus grown in municipal wastewater and was calculated based on the change in dissolved oxygen concentration. Results indicated that magnetic treatment stimulates both algal growth and oxygen production. Application of 1000 GS of magnetic field once at logarithmic growth phase for 0.5 h increased the chlorophyll- a content by 11.5% over the control after 6 days of growth. In addition, magnetization enhanced the oxygen production rate by 24.6% over the control. Results of the study confirmed that application of a proper magnetic field could reduce the energy consumption required for aeration during the degradation of organic matter in municipal wastewater in algal-bacterial symbiotic systems. [ABSTRACT FROM AUTHOR]

Porous nickel electrodes for alkaline water electrolysis were made in simple manner by sintering nickel powder that was first compressed into nickel foam. The pores inside the sintered body show asymmetrical distribution in size, small pores (∼5 μm) existing near one surface and open structure (pore size: 100–200 μm) at the other surface. Such asymmetric body performs the dual role such that one surface has the electro-catalytic layer for the electrochemical reactions and the other surface has the escaping route of gas/electrolyte mixture. A nickel electrode stack was assembled by incorporating the sintered bodies, polymer separators and multi-functional light-weight gaskets. Two nickel electrodes with a separator between them were enclosed to make a unit cell in the gasket frame which plays the multi-role of electrolyte supply, exit of produced gas and sealing agent. By applying 1.8 V per unit cell, an electrolyzer made of such stacks with electrodes of 200 cm 2 surface area displays current of over 80 A at 80 °C over 400 h. [ABSTRACT FROM AUTHOR]

Toxic metal pollution is a major environmental problem that has received wide attention. Platanus acerifolia (London plane tree) is an important greening tree species that can adapt to environmental pollution. The genetic basis and molecular mechanisms associated with the ability of P. acerifolia to respond lead (Pb) stress have not been reported so far. In this study, 16,246 unigenes differentially expressed unigenes that were obtained from P. acerifolia under Pb stress using next-generation sequencing. Essential pathways such as photosynthesis, and gibberellins and glutathione metabolism were enriched among the differentially expressed unigenes. Furthermore, many important unigenes, including antioxidant enzymes, plants chelate compounds, and metal transporters involved in defense and detoxification mechanisms, were differentially expressed in response to Pb stress. The unigenes encoding the oxygen-evolving enhancer Psb and OEE protein families were downregulated in Pb-stressed plants, implying that oxygen production might decrease in plants under Pb stress. The relationship between gibberellin and P. acerifolia flowering is also discussed. The information and new insights obtained in this study will contribute to further investigations into the molecular regulation mechanisms of Pb accumulation and tolerance in greening tree species. [ABSTRACT FROM AUTHOR]

SrTiO 3 single crystals enclosed with high-indexed {0 2 3} facets and {0 0 1} facets were facilely synthesized via a one-pot solvothermal method. The ratio of {0 2 3} to {0 0 1} facets could be simply adjusted by tuning the NaOH and EA concentrations during the solvothermal growth process. It was demonstrated that the photocatalytic activities of the variously shaped SrTiO 3 should be closely related to the morphology of SrTiO 3 , i.e. , the ratio of {0 2 3} to {0 0 1} facet. The highest photocatalytic activities are achieved for SrTiO 3 single crystals with the ratio of {0 2 3} to {0 0 1} facet tuned to 35:65, with hydrogen and oxygen evolution rates reaching 71.1 and 30.0 μmol/h, respectively, which are about 9.5 and 3.0 times higher than those of the irregular SrTiO 3 particles. Facet selective photo-deposition of metal ions reveals that the high-indexed {0 2 3} facets provided active sites for photo-oxidation reaction, while the {0 0 1} facets offered active sites for photo-reduction reaction. Such spatially separated photoactive reduction and oxidation sites should benefit charge separation in a SrTiO 3 single crystal, leading to higher photocatalytic activity related to the irregular SrTiO 3 particles. [ABSTRACT FROM AUTHOR]

Two new RuIII complexes with anionic N, O donor pyridine dicarboxylate (pdc2−) ligand along with neutral bipyridine moieties have been found to effectively catalyze the water oxidation both chemically using Cerric ammonium nitrate (CAN) and electrochemically. Spectro-chemical and electrochemical study and theoretical evidences by means of DFT calculation support the I2M mechanism to be followed by the molecules to peruse the water oxidation reaction in the current study. [Display omitted] Herein we report two new mononuclear heteroleptic Ruthenium complexes, 1 and 2 with anionic N, O donor pyridine dicarboxylate (pdc2-) ligand along with neutral bipyridine moieties. The general formula of the complexes are [RuIII(pdc2-)(L 1)Cl] (1) , [RuIII(pdc2-)(L 2)Cl] (2) (Where L 1 = bipyridine, L 2 = 4,4′-dimethylbipyridine). Synthesis, characterization and water oxidation catalytic properties of both complexes were investigated. A combined theoretical (DFT) and experimental study were carried out to investigate the catalytic (in presence of CAN) and electrocatalytic activity of 1 and 2 for water oxidation in aqueous solution at pH ∼ 1. During electrocatalysis, the catalytic activity wave has been detected in acetonitrile/water 1:9 (v/v) solution in the range 1.39–1.41 V vs SCE. pH based electrochemistry reveals that, water oxidation (at pH = 1) takes place via sequential proton-electron transfer process to form a RuV = O moiety, which oxidises water through I2M pathway. For water oxidation by CAN, both the molecules show appreciably high TOF values 3.47971 x10-4 s−1 and 1.183 × 10–3 s−1 for 1 and 2 respectively in comparison to similar molecules [1,2]. [ABSTRACT FROM AUTHOR]

[Display omitted] • Experimental setup for evolved oxigen monitoring was constructed. • Bray-Liebhafsky reaction was investigated at 2 mixing rates in 5 replicates. • Lower mixing rate preserve higher content of dissolved gas. • Lower stirring facilitate oscillatory evolution. • Heterogeneous effects assist in triggering iodine oxidation. Upgraded design of the experimental setup for monitoring Bray-Liebhafsky (BL) oscillatory reaction dynamics allowed simultaneous recording of platinum electrode potential and gaseous pressure changes over time. Experiments were performed at two stirring rates (600 rpm and 1200 rpm) in five replicates. Evolved gas at two mixing rates is correlated with reaction induction period, number of oscillations, period between oscillations, oscillation amplitude and number of produced oxygen moles per oscillation. Obtained trends indicate that the amount of formed gas facilitates initiation of iodine oxidation. Results are in agreement with previous findings which point to the importance of heterogeneous effects in reaction of iodine oxidation. [ABSTRACT FROM AUTHOR]

This work evaluates the thermodynamic performances of two oxygen separation technologies, Pressure Driven Electrolytic Membranes (PDEM) and Solid Electrolyte Oxygen Pumps (SEOP), focusing on the application to small scale oxygen production. We show that PDEM systems operated with a specific flux of 5 liters of oxygen per minute per square meter of active membrane surface (5 L O2 /min-m 2 ) can reach an energy consumption as low as 0.39 kWh/kg O2 . In the same conditions with a SEOP, the optimized energy consumptions are 0.52 and 0.49 kWh/kg O2 respectively for atmospheric and pressurized configurations. [ABSTRACT FROM AUTHOR]

Perovskite-type oxide has been considered to be an effective oxygen carrier for producing oxygen-enriched gas stream for oxy-fuel combustion application. However, the main problem with those researched perovskite-type oxides as oxygen carriers is their relatively low oxygen production amount. This has limited oxygen concentration and the productivity of the separation process. This paper reports on characteristics and oxygen production performance of improved perovskite materials of Ba-Sr-Co-Fe oxides synthesized by a new microwave-assisted EDTA method (MWA-EDTA). The effect of microwave operating times on the oxygen production properties of perovskite-type Ba1-xSrxCo0.8Fe0.2O3-δ (x = 0, 0.5, 1) as well as the cyclic performance of improved BaCo0.8Fe0.2O3-δ (BCF) powders are investigated in details. All obtained samples are characterized using X-ray diffraction (XRD), specific surface area measurements (BET) and environmental scanning electron microscopy (ESEM). The results indicate that the samples with smaller crystallite size and higher porosity obtained by the MWA-EDTA showed better oxygen production properties than those prepared by conventional EDTA method. And the optimal microwave irradiation time for BCF is 30 min operating times. Furthermore, cyclic tests show that BCF synthesized by the optimal conditions has excellent reactivity and regeneration capacity after 21 cycles. [ABSTRACT FROM AUTHOR]

The first complete action spectrum of oxygen evolution and chlorophyll a fluorescence was measured for the biofuel candidate alga Nannochloropsis oculata . A novel analytical procedure was used to generate a representative and reproducible action spectrum for microalgal cultures. The action spectrum was measured at 14 discrete wavelengths across the visible spectrum, at an equivalent photon flux density of 60 μmol photons m −2 s −1 . Blue light (∼414 nm) was absorbed more efficiently and directed to photosystem II more effectively than red light (∼679 nm) at light intensities below the photosaturation limit. Conversion of absorbed photons into photosynthetic oxygen evolution was maximised at 625 nm; however, this maximum is unstable since neighbouring wavelengths (646 nm) resulted in the lowest photosystem II operating efficiency. Identifying the wavelength-dependence of photosynthesis has clear implications to optimising growth efficiency and hence important economic implications to the algal biofuels and bioproducts industries. [ABSTRACT FROM AUTHOR]

Abstract: This work presents the effects of processing on the shape stability of different ceramic-polymer compounds (feedstocks) to obtain, by extrusion, thin tubular Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) perovskite membranes with a diameter of 10mm and wall thickness of <300μm. The influence on the polymer degradation during compounding and the processability to achieve geometrically stable thin wall tubes after debinding were analyzed. The ceramic-polymer composite was evaluated with a torque rheometer and capillary rheometer using Arrhenius plots (temperature–viscosity relationship) to investigate the activation energy of viscous flow (E f ). The shape stability, e.g. roundness and straightness, of the extruded tubes before and after the debinding step was investigated for the different binder systems. The feedstock based on 52vol% BSCF powder and a polymeric mixture of 80wt% polystyrene (PS) and 20wt% polyethylene glycol (PEG) demonstrated reproducible processing behavior and sufficient shape stability after debinding. The tubes fabricated with this feedstock showed good longitudinal shrinkage (2.86%) and roundness (ΔD max−min /D max <1.62%), absence of defects, suitable straightness and a homogeneous microstructure. [Copyright &y& Elsevier]

Highlights: [•] Visible light responsive and pure phase Bi20TiO32 has been successfully synthesized. [•] Chelating agent and precursors have an effect on the material properties. [•] The grain size of Bi20TiO32 depends on the ratio of citric acid to metal ions. [•] Photocatalytic activity of Bi20TiO32 for O2 evolution can be enhanced by co-catalysts. [•] The as-prepared Bi20TiO32 sample shows excellent stability during oxygen evolution. [ABSTRACT FROM AUTHOR]

Highlights: [•] Membrane compete to cryogeny only if selectivity is over 20. [•] Air drying has a strong impact on membrane energy efficiency. [•] Attractive performances with selective membranes for 30–70% oxygen. [•] Improved cryogenic processes could offer decisive advantages over membranes. [Copyright &y& Elsevier]

Nitric oxide (NO) and nitrous oxide (N2O) are among Nature’s most powerful electron acceptors. In recent years it became clear that microorganisms can take advantage of the oxidizing power of these compounds to degrade recalcitrant aliphatic and aromatic hydrocarbons. For two unrelated bacterial species, the ‘NC10’ phylum bacterium ‘Candidatus Methylomirabilis oxyfera’ and the γ-proteobacterial strain HdN1 it has been suggested that under anoxic conditions with nitrate and/or nitrite, monooxygenases are used for methane and hexadecane oxidation, respectively. No degradation was observed with nitrous oxide only. Similarly, aerobic pathways for hydrocarbon degradation are employed by (per)chlorate-reducing bacteria, which are known to produce oxygen from chlorite (ClO2-). In the anaerobic methanotroph M. oxyfera, which lacks identifiable enzymes for nitrogen formation, substrate activation in the presence of nitrite was directly associated with both oxygen and nitrogen formation. These findings strongly argue for the role of NO, or an oxygen species derived from it, in the activation reaction of methane. Although oxygen generation elegantly explains the utilization of ‘aerobic’ pathways under anoxic conditions, the underlying mechanism is still elusive. In this perspective we review the current knowledge about intra-aerobic pathways, their potential presence in other organisms and identify candidate enzymes related to quinol-dependent NO reductases (qNORs) that might be involved in the formation of oxygen.

Abstract: CO2 reduction from fossil-fired power plants can be achieved by carbon dioxide capture and storage (CCS). Among different CO2 capture technologies for power plants the oxyfuel power plant concept is a promising option. High temperature ceramic membranes for oxygen production have the potential to reduce the associated efficiency losses significantly compared to conventional air separation using cryogenic techniques. Focus of this paper is the environmental performance of membrane-based oxygen production for oxyfuel power plant technology. Included into the analysis are the production of the perovskite membrane (BSCF=Ba0.5Sr0.5Co0.8Fe0.2O3−δ ), the incorporation into a steel module, and the integration of several modules into an oxyfuel power plant. The membrane-based oxygen production is compared to the conventional cryogenic air separation in oxyfuel power plants in an ecological way. The evaluation is performed using life cycle assessment (LCA) methodology from “cradle to grave”. The share in the overall environmental impacts of respective life cycle elements like membrane and module production but also coal supply processes as well as the operation of the oxyfuel power plant are identified. Sensitivity analyses referring to life-time, permeability and housing conditions of the membranes set benchmarks for further membrane development. [Copyright &y& Elsevier]

The performances of two types of zeolite 5A and zeolite 13X in oxygen separation from air with a two-bed six-step pressure swing adsorption (PSA) system were investigated using mathematical modeling. The effects of feed flow rate, adsorption step pressure, adsorption step time and purge to feed ratio on oxygen purity and recovery are studied. Comparison of two types of zeolites shows that the PSA process performance (in terms of purity and recovery) was better with zeolite 13X than the zeolite 5A. Furthermore, Results of simulation indicated a very good agreement with some current literature experimentally work. [ABSTRACT FROM AUTHOR]

Abstract: Oxygen is commonly produced at industrial scales by air separation using cryogenic air separation units (CASU). Despite being the most matured technology, CASU is highly energy intensive. Approximately, 3–4% energy penalty is expected to be arising for oxygen production using CASU in the oxy-fuel process. As an alternative to CASU, this paper demonstrates the integrated chemical looping air separation (ICLAS) process for oxy-fuel thermal power plant which is expected to offset the energy penalty associated with CASU. In our recent comprehensive thermodynamic study, three metal oxide systems (Mn, Co and Cu) were found most suitable for chemical looping air separation (CLAS). The objective of this work is to find out the possible integration modes of the CLAS process with oxy-fuel coal-fired power plants. Thermodynamic process simulations were carried out for ICLAS in oxy-fuel using Fact-sage 6.1 database for all selected oxygen carriers and process kinetics have not been considered. The effect of several process parameters such as operating temperature, heat recovery, actual partial pressure in the reactors and chemical conversion of the oxygen carriers on the operating cost of the ICLAS process were investigated in detail. The results indicate that for acceptable process kinetics ICLAS can potentially run at much lower operating costs compared to an advanced CASU based system by 2020. [Copyright &y& Elsevier]

The cyanobacterium Microcystis aeruginosa forms blooms that can consist of colonies. We have investigated how M. aeruginosa acclimatizes to changing light conditions such as can occur during blooms. Three different strains were exposed to two irradiance levels: lower ( LL) and higher ( HL) than the irradiance-onset saturation parameter. We measured the photosynthetic pigment concentrations, PSII photochemical efficiency, electron transport rate ( ETR), irradiance-saturated ETR and ETR efficiency. The relationship between ETR and photosynthetic oxygen production and the excess in PSII capacity were also studied for one strain. Higher values of chlorophyll a and phycocyanin and lower values of total carotenoids were found under LL conditions in the three strains. The strains showed clear differences in the irradiance-saturated ETR and in ETR efficiency under both LL and HL treatments. No differences were found in the linear relationship between ETR and photosynthetic oxygen production under both irradiance treatments. LL-acclimated cells showed higher PSII excess capacity than HL ones, possibly because their higher pigment content could result in a higher light stress than HL cells when forming surface blooms. The fact that the genetically different strains show different photosynthetic physiologies suggests that the very dynamic light climate observed in lakes may allow their coexistence. [ABSTRACT FROM AUTHOR]

Abstract: The present article summarises the various methods that have been, and still are, explored for the production of oxygen from lunar materials. These include the classical concepts based on chemical reduction with hydrogen or methane, vapour phase pyrolysis, sulphuric acid treatment, and molten oxide electrolysis. Our main focus in this paper is on a novel approach developed at the University of Cambridge that employs molten salt electrochemistry to achieve the combined winning of oxygen and metal from solid lunar materials of varying composition. This makes the Cambridge process attractive because it will work equally well in mare as in highland regions. We also discuss the implications of the recent apparent discovery of water ice at the poles of the Moon and conclude that, even if this discovery is confirmed, it will nevertheless be desirable to provide oxygen at non-polar localities, and the Cambridge process is a strong candidate for achieving this. [Copyright &y& Elsevier]

This research examined the use of a single facultative pond for treatment of an intermittent discharge from a UK campsite. The system was monitored over an 11-month period to determine the optimum time for discharge in terms of quality standards. The results showed that based on organic strength, discharge was possible in winter between November and March but February was the optimum to meet nutrient and suspended solids requirements. The pond showed rapid acclimatisation to the influent wastewater, with biochemical oxygen demand removal rates during the filling period of around 60 kg ha-1 day-1 and removal efficiencies of ∼95% after maturation. The system proved simple to operate. A major design factor is the requirement for storage of net incoming precipitation, which may provide dilution of residual pollutants but requires additional system capacity. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a finite difference one-dimensional (1D) model of a single unit SOFC–SOEC stack, a novel technology based on the integration of a solid oxide fuel cell (SOFC) and solid oxide electrolyzer (SOEC), and a promising candidate for the high efficiency production of oxygen and/or hydrogen, especially for small scale applications. The model is applied to determine the performance of a SOFC–SOEC integrated system for oxygen production which has been previously analysed by means of a simplified zero-dimensional or lumped volume approach. The improved 1D model is used to explore the impact of different system configurations and operating conditions. It is shown that the simplified approach previously used overestimates the performance of the system by up to 60%. Despite this, the results presented here show an electricity consumption in optimized conditions in the range of 0.35–0.5kWh/kgO2, still significantly lower than that of state of the art technology for small scale oxygen production systems. [Copyright &y& Elsevier]

In this paper the results of the thermodynamic analysis of the oxy-combustion type pulverized bed boiler integrated with a hybrid, membrane- cryogenic oxygen separation installation are presented. For the calculations a 600 MW boiler with live steam parameters at 31.1 MPa /654.9 °C and reheated steam at 6.15 MPa/672.4 °C was chosen. In this paper the hybrid membrane-cryogenic technology as oxygen production unit for pulverized bed boiler was proposed. Such an installation consists of a membrane module and two cryogenic distillation columns. Models of these installations were built in the Aspen software. The energy intensity of the oxygen production process in the hybrid system was compared with the cryogenic technology. The analysis of the influence of membrane surface area on the energy intensity of the process of air separation as well as the influence of oxygen concentration at the inlet to the cryogenic installation on the energy intensity of a hybrid unit was performed. [ABSTRACT FROM AUTHOR]

Abstract: In this work, module containing La0.6Sr0.4Ti0.3Fe0.7O3−δ coated Ba0.5Sr0.5Co0.8Fe0.2O3−δ tubular membranes was successfully prepared and evaluated for oxygen production. The oxygen permeability of a single-La0.6Sr0.4Ti0.3Fe0.7O3−δ coated Ba0.5Sr0.5Co0.8Fe0.2O3−δ tubular membrane was studied in the same condition for comparison. The oxygen permeation flux was measured at temperature, air pressure, and retentate flow rate range of 850–950°C, 3–9atm, and 200–5000mL/min, respectively. Oxygen permeation flux increased with increasing retentate flow rate, temperature and air pressure, while oxygen recovery decreased with increasing retentate flow rate at the same condition. Oxygen production rate and recovery of module containing three-La0.6Sr0.4Ti0.3Fe0.7O3−δ coated Ba0.5Sr0.5Co0.8Fe0.2O3−δ tubular membranes (length=22.5cm, total effective surface area=75.06cm2 (25.02cm2 ×3), thickness=0.8mm) were 463mL/min and 40% at 900°C under 9atm and 5000mL/min retentate flow, respectively. Moreover, long-term operation test results indicate that the oxygen production rate was quite stable during the oxygen production operation. [Copyright &y& Elsevier]

Abstract: Iron oxide was electrochemically split into iron and oxygen gas in molten Na2CO3–K2CO3 at 750°C using a solid iron oxide cathode and a Ni10Cu11Fe alloy inert anode. Fe2O3 was electrochemically reduced to Fe on the cathode, releasing oxygen anions into the electrolyte and which were oxidized on the anode to generate O2. The cathodic current efficiency was as high as 95% and the energy consumption for producing 1kg iron was 2.87kWh, only half of the current industrial energy consumption of blast-furnace steel production. Due to the cost-affordable inert anode and the high energy efficiency, the method demonstrated in this work shows promise as a practical “green” iron production process. [Copyright &y& Elsevier]

Abstract: La0.6Sr0.4Co0.2Fe0.8O3−α (LSCF) hollow fibre membranes prepared by a phase-inversion/sintering technique were assembled into a membrane system to produce oxygen of high purity (>99%) from air at elevated temperatures. The separation performances, stability, scaling-up effect and the energy consumption of the membrane system were investigated both theoretically and experimentally. The membrane system containing 889 hollow fibres could yield maximum 3.1L(STP)min−1 oxygen with the purity of 99.9% at 1070°C and 98.5kPa vacuum degree, but the temperature higher than 1070°C would lead to the system failure. It showed the potential of much higher production rates only if the high-temperature sealing problem could be solved. When operated at around 960°C, the system exhibited more than 1167h longevity with the oxygen production rate of 0.84L(STP)min−1 and oxygen purity of 99.4%. The energy consumption of the system increased with operating temperature but the energy consumption per unit oxygen product decreased with increasing the operating temperature and the effective membrane areas. In order to reduce the oxygen cost to commercial level, heat exchangers have to be integrated in the membrane system to recover the heat energy in both the exhaust gas and the oxygen product. The oxygen recovery should be limited within 20–40% for the sake of both energy and membrane area savings. [Copyright &y& Elsevier]

Abstract: The study aimed to estimate the total oxygen flow through the shallow littoral of the Gulf of Gdańsk (southern Baltic Sea). Daily primary production and daily oxygen consumption by meso- and macroplankton and meio- and macrobenthos were measured, as well as the remaining (abiotic/microbial) oxygen consumption of the water column and bottom sediment. The daily gross primary production was 5.0l of oxygenm−2, oxygen consumption was 9.2lm−2, of which 16% were used by the water column and 84% by the bottom sediment. Abiotic oxygen consumption in water column contributed to less than 5% of the total oxygen consumption, and in the bottom sediment to 67%. Mesoplankton in the water column and meiobenthos in the bottom sediments were the major oxygen consumers in the littoral (67% and 26%, respectively). [Copyright &y& Elsevier]

Abstract: Microcystis aeruginosa is well known for its ability to produce the group of hepatotoxic microcystins (MCYST) but the mechanisms that control their synthesis are not clearly understood. Possible effect of light and nutrients on MCYST content was already proposed, but contradictory results were reported. In this study, we have grown M. aeruginosa (UTCC299) under a wide range of light conditions (24–820μmolphotons(PAR)m−2 s−1) and showed that MCYST content decreased (106fg (SE±7) to 47fg (SE±3) MCYSTcell−1) with increasing photon irradiance. Our data showed that MCYST content was positively linked to Chl a content and inversely correlated to cell specific division rate. Chlorophyll fluorescence kinetics was used to assess photosynthetic activity and the relative electron transport rate (ETR). The latter was negatively correlated with MCYST content and was the best predictor of MCYST content compared to light and growth. Moreover, the redox state of the photosynthetic apparatus estimated by the unquenched fluorescence parameter (UQF(REL)) was also negatively correlated to MCYST content per cell. Therefore, our data demonstrated that photosynthetic light reactions, through electron transport rate (ETR) and PSII redox state, modulate MCYST content at the cellular level. Knowing that environmental conditions affect photosynthetic light reactions, our results indicated that future work should also pay closer attention to the involvement of photosynthesis in the modulation of MCYST. [Copyright &y& Elsevier]

Abstract: Oxygen permeation through Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCFO) perovskite tubular membranes was investigated under vacuum and elevated pressures conditions. This paper is focused on dependence of oxygen permeation flux on oxygen recovery, temperature and feed pressure. Oxygen flux decreases with the raise of oxygen recovery, more quickly when the recovery is larger than about 60%. Elevating the feed pressure speeds up the decrease of oxygen fluxes against oxygen recovery. Oxygen permeation flux increases with the feed pressure of air, however, the increment decreases gradually. Oxygen permeation flux and recovery increase with temperature gradually at a constant airflow rate and pressure. The permeation flux reached 9.5cm3/cm2 min at an oxygen recovery of 48% under the condition of 925°C and vacuum pressure of ∼100Pa for permeation side and 7atm for feed side. Long-term operation under vacuum and elevated pressure shows that oxygen purity larger than 99.4% can be obtained when silver was used as sealant. [Copyright &y& Elsevier]

Abstract-A kinetic model for Martian atmospheric entry plasma (MAEP) is presented. The model was calculated based on data from Viking, Pathfinder, and the Mars Exploration Rovers Opportunity and Spirit. Calculations of the density, temperature, and electron density across the shock front were made. We employed steady-state and nonsteady-state kinetic models to describe the rate of dissociation of CO2 in the Martian atmosphere as well as the production of O2. Water vapor was included in the models since it represents 0.03% of the surface atmospheric composition. With the addition of small amounts of water vapor, we found a decrease in the dissociation of CO2 in the Martian air as well as an increase in the production of O2. This paper is to report an analysis of MAEP and its interactions with the shock front which forms in the front of the Martian Landers. [ABSTRACT FROM AUTHOR]

A method for estimating the mass and fission surface power requirements of a lunar oxygen production facility is introduced. The individual modeling components involve the chemical processing and cryogenic storage subsystems needed to process a beneficiated regolith stream into liquid oxygen via ilmenite reduction. The power can be supplied from one of six different fission reactor-converter systems. A baseline system analysis, capable of producing 15 tonnes/yr of oxygen, is presented. The influence of reactor-converter choice was seen to have a small but measurable impact on the system configuration and performance. Finally, the mission concept of operations can have a substantial impact upon individual component size and power requirements. [ABSTRACT FROM AUTHOR]

Large quantities of detritus can accumulate on the bottom sediments of eutrophic lakes, leading to depletion of dissolved oxygen (DO) in the hypolimnion. Decreased redox potential associated with low hypolimnetic DO concentrations can accelerate the remobilization of ammonia and phosphorus from the sediments back into the water column. As maintenance of aerobic conditions in the hypolimnion is an important consideration for successful lake management, this research focused on the use of periphyton production of DO to control hypolimnetic DO levels. To augment periphyton photosynthesis, light was irradiated to the bottom sediments via glass fibres, in order to examine the effects of light irradiation on DO restoration on bottom sediments in test chambers. Dissolved oxygen restoration by periphytic photosynthesis was confirmed in these experiments, with both temperature and light intensity having positive effects on the areal net oxygen production rate. The Q10 temperature coefficient for net oxygen production was estimated to be 2.24. In typical temperate-zone lakes, the hypolimnetic water temperature is <15 °C, resulting in an expected areal net oxygen production rate ranging from 100 to 200 mg O2 m−2 day−1 at a light irradiation of 50 μE m−2 s−1. Based on these experimental results, the condenser area required to achieve DO restoration under hypolimnetic light irradiation alone was estimated to be 3.2–4.1% of the hypolimnetic area. Thus, hypolimnetic light irradiation combined with hypolimnetic aeration can reduce energy consumption required for hypolimnetic aeration in DO restoration efforts. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a novel system for production of pure oxygen based on the integration of a solid oxide fuel cell (SOFC) and a solid oxide electrolyzer (SOEC). In the proposed arrangement, the SOFC provides electricity, heat and H2O in vapour phase to the SOEC which carries out the inverse reactions of the SOFC, that is the separation of H2O into H2 (used as a fuel for the SOFC) and O2 (representing the yield of the system). Simulations carried out in different operating conditions show that when the integrated SOFC–SOEC device runs at low current densities (less than 1000Am−2), pure oxygen can be generated with an electric consumption comparable to mid-size cryogenic air separation units, and significantly lower than small scale systems based on the PSA technology. [Copyright &y& Elsevier]

Iron minerals, such as iron oxides and iron oxyhydroxides, are the main influential soil components in catalyzed hydrogen peroxide propagation (CHP). Due to their dual effects on H 2 O 2 activation to produce reactive oxygen species (ROS) and invalid consumption to produce oxygen, the intrinsic reactivity of iron minerals toward H 2 O 2 decomposition requires comprehensive investigations. Herein, six iron minerals (hematite, magnetite, maghemite, goethite, feroxyhyte, and ferrihydrite) for H 2 O 2 decomposition were investigated by a combination of normalized kinetic rate constants of H 2 O 2 decomposition (Nk H2O2), O 2 production (Nk O2), benzoic acid degradation (Nk BA), and hexachloroethane degradation (Nk HCA) over the surface area of each mineral. The results indicate H 2 O 2 decomposition over iron minerals is a surface-related heterogeneous process. Hematite and goethite are the most promising minerals for environmental cleanup in terms of ROS production, because their H 2 O 2 utilization efficiency for benzoic acid (BA) degradation (0.138 and 0.024 mol BA/mol H 2 O 2 for hematite and goethite, respectively) are highest among the six iron minerals. Magnetite and maghemite are highly active for both H 2 O 2 decomposition and O 2 production at neutral and basic pHs. The presence of organic compounds suppresses O 2 production by more than 60%, which favors H 2 O 2 utilization. Ferrihydrite and feroxyhyte are considered as the problematic mineral for CHP due to that the two minerals acquire a high O 2 production and negligible ROS generation at all pHs. The results of this study provide new insights to increase the understandings of H 2 O 2 -iron mineral systems and guide the application of iron minerals in chemical oxidation technologies. [Display omitted] • H 2 O 2 conversion pathways in the six H 2 O 2 -iron mineral systems were investigated. • Kinetics of H 2 O 2 reduction, O 2 production and organic degradation were compared. • Hematite and goethite are promising for use due to high H 2 O 2 utilization efficiency. • Magnetite and maghemite are less attractive for H 2 O 2 activation. • Ferrihydrite and feroxyhyte are problematic minerals due to invalid H 2 O 2 consumption. [ABSTRACT FROM AUTHOR]

Abstract: In the copper–chlorine (Cu–Cl) thermochemical cycle water is decomposed into its constituents (oxygen and hydrogen) by a series of chemical reactions. The cycle involves five steps in which three thermally driven chemical reactions and one electrochemical reaction take place. Oxygen is produced during one of the main chemical reactions. In the present study, the O2 production step is described with its operational and environmental conditions, and energy and exergy analyses are performed. The cycle is assumed driven using nuclear energy. Various parametric studies are carried out on energetic and exergetic aspects of the step, considering variable reaction and reference-environment temperatures. At a constant reference-environment temperature of 25°C, the exergy destruction of the O2 production step varies between 4500 and 23,000kJ/kmolH2 when the reaction temperature increases from 450 to 1000°C. At a 500°C reaction temperature and a 25°C reference-environment temperature, the exergy destruction for this step is found to be 5300kJ/kmolH2. At a reaction temperature of 500°C and a reference-environment temperature of 25°C, the exergy efficiency of the step is determined to be 96% and to decrease with increasing reaction temperature and/or reference-environment temperature. [Copyright &y& Elsevier]

Now, it is time to set up reliable water electrolysis stacks with active and robust electrocatalysts to produce green hydrogen. Compared with catalytic kinetics, much less attention has been paid to catalyst stability, and the weak understanding of the catalyst deactivation mechanism restricts the design of robust electrocatalysts. Herein, we discuss the issues of catalysts' stability evaluation and characterization, and the degradation mechanism. The systematic understanding of the degradation mechanism would help us to formulate principles for the design of stable catalysts. Particularly, we found that the dissolution rate for different 3d transition metals differed greatly: Fe dissolves 114 and 84 times faster than Co and Ni. Based on this trend, we designed Fe@Ni and FeNi@Ni core-shell structures to achieve excellent stability in a 1 A cm−2 current density, as well as good catalytic activity at the same time. [ABSTRACT FROM AUTHOR]