Effect of annealing in O2 or N2 on the aging of Fe0.5Mn1.84Ni0.66O4 NTC-ceramics

Fe0.5Mn1.84Ni0.66O4 NTC ceramic thermistors were annealed in nitrogen or oxygen atmosphere at 600 °C. The change of the electrical properties of the thermistors with time was reduced sharply by annealing in N2, whereas it was enhanced upon annealing in O2. N2-annealed samples exhibited a less degree of redistribution of cations in the lattice as compared with O2-annealed samples. The aging of the electrical properties is believed to result from the cation redistribution which in turn is favoured by the presence of cation vacancies. And the improved aging behaviour of the N2-annealed thermistor is explained by the reduction of the concentration of the cation vacancy upon annealing under lower oxygen partial pressure and the suppression of cation redistribution

Weak electricity stimulates biological nitrate removal of wastewater: Hypothesis and first evidences

International audienceNitrate pollution in water is a worldwide health and environmental concern. Biological nitrate removal of wastewater is widely used countering eutrophication of water bodies; however it could be troublesome and expensive when influent carbon source is insufficient. Here we present a novel process, the microbial fuel cell (MFC)-resistance-type electrical stimulation denitrification process (RtESD) using microbial weak electricity originated from the wastewater, to enhance nitrate removal. Results show that the optimal nitrate dependent denitrification rate (0.027 mg N/L·h) and nitrate removal efficiency (98.1%) can be achieved; partial autotrophic denitrification was enhanced in RtESD under stimulation of 0.2 V of microbial weak electricity (MWE). Aromatic proteins also increased in the presence of 0.2 V MWE stimulation according to three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy profiles, indicating that electron transfer could be improved in the case of MWE stimulation. Furthermore, the microbial community structure and diversity analysis results demonstrated that MWE stimulation inhibited the heterotrophic denitrifying bacteria and activated the autotrophic denitrifying bacteria in RtESD. Two hypotheses, enhancement of electron transfer and improvement of microorganism activity, were proposed regarding to the MWE stimulated pathways. This study provided a promising method utilizing MWE derived from wastewater to improve the denitrification rate and removal efficiency of nitrate-containing wastewater treatment processes

Efficient recovery of phosphate from simulated urine by Mg/Fe bimetallic oxide modified biochar as a potential resource

International audienceThe massive use of phosphate fertilizers in agriculture is costly and induces water pollution, calling for more sustainable phosphate sources in the context of the circular economy. Here we prepared a new adsorbent based on waste straw biochar modified with the Mg/Fe bimetallic oxide, namely the Mg/Fe biochar, to recover phosphate from the simulated urine as an possible phosphate fertilizer. About 90% phosphate was recovered from the simulated urine with a wide pH range of 3.0–9.0 and a maximum adsorption capacity of 206.2 mg/g, using 1 g/L of Mg/Fe modified biochar. A pseudo second-order kinetics and Sips model were proposed to fit the experimental data well, suggesting that the adsorption was controlled by physical and chemical processes, which is driven by electrostatic attraction, intra-particle diffusion, ion exchange and surface ligand exchange. Overall, theMg/Fe biochar is renewable and can recover more than 70% of phosphate in the simulated urine after 5 cycles of reuse, which appears as a safe and efficient adsorbent to recycle phosphate from urine

Vehicle speed guidance strategy at signalized intersection based on cooperative vehicle infrastructure system

In order to reduce stopping time of vehicle at a signalized intersection, aiming at the difficulty, even the impossibility to obtain real-time queue length of intersection in third and fourth-tier cities in China sometimes, a speed guidance strategy based on cooperative vehicle infrastructure system is put forward and studied. For validating the strategy, the traffic signal timing data of the intersection at Hengshan Road and North Fengming Lake Road in Wuhu is collected by a vehicular traffic signal reminder system which is designed. The simulation experiments using the acquired data are done by software VISSIM. The simulation results demonstrate that the strategy under high and low traffic flow can effectively decrease the link travel-time, reducing average ratio is 9.2 % and 13.0 %, respectively, and the effect under low traffic flow is better than that under high traffic flow. The strategy improves efficiency of traffic at a signalized intersection and provides an idea for the application of vehicle speed guidance based on cooperative vehicle infrastructure system

Self-provided microbial electricity enhanced wastewater treatment using carbon felt anode coated with amino-functionalized Fe3O4

International audienceBioelectricity can be produced from wastewater using microbial fuel cells (MFCs) that produce electricity during electrochemical and biochemical reactions, yet actual applications of wastewater MFCs are limited; a selfprovided microbial electricity enhanced wastewater treatment method is proposed producing microbial power and enhanced pollutants removal simultaneously. A carbon felt coated with amino-functionalized Fe3O4 particles was synthesized; power generation, removal of chemical oxygen demand (COD) and NH4+-N were evaluated with cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), cell voltage and treatment efficiency. Results showed that the amino-Fe3O4 coated anode led to higher NH4+-N removal efficiency of 97.7 % than the Fe3O4 coated anode of 48.9 %. Moreover, the maximum power density of the amino-Fe3O4 anode is 208.67 mW/ m 2 , 35.1 % higher than that of the Fe3O4 anode. This finding was explained by the presence of protonated amino groups NH4+ that favored the attachment of negatively charged bacteria. Amino-functionalization of the anode promotes a promising, novel technology to treat wastewater while producing electricity

Towards synergistic combination of biochar/ultrasonic persulfate enhancing removal of natural humic acids from water

International audienceRemoval of natural organic matter (NOMs) from actual water is a major challenge in the context of worldwide pollution of natural water resources. The removal of humic acids in a system combining biochar adsorption and ultrasonic persulfate oxidation was studied in this paper. The effects of biochar addition, persulfate concentration and initial pH were investigated. A high removal rate of humic acids up to 92.5% was achieved for the combined biochar/ultrasonic/persulfate system, versus 84.0% for combined biochar/persulfate, 52.0% for sole biochar, 50.0% for combined biochar/ultrasonic, 10.0% for combined persulfate/ultrasonic, 4.0% for sole ultrasonic and 1.0% for sole persulfate systems. Ultrasonic treatment increased the removal efficiency of humic acids to 90.0% within 60 min. Mechanisms towards synergistic combination of the biochar/ultrasonic/persulfate system were investigated by gel permeation chromatography, electron paramagnetic resonance and quenching experiments together with the characterization of biochar. Hydroxyl radical and the adsorption of biochar were the major contributors to the proposed synergistic adsorption-oxidation removal mechanism, followed by the sulfate radical SO 4-⋅. The results of three-dimensional fluorescence diagram, fluorescence regional integration and TOC analysis indicated that the system presented promising application prospects to remove NOM pollutants from real water