Single-chamber microbial electrosynthesis reactor for nitrate reduction from waters with a low-electron donors’ concentration : from design and set-up to the optimal operating potential

Funding Information: This research was supported by the Estonian Research Council (grant numbers PSG631, PSG714, PRG352) and by the European Union (EU) through the European Regional Development Fund: Centre of Excellence EcolChange, TK 141 Advanced materials and high-technology devices for energy recuperation systems (grant number 2014-2020.4.01.15-0011), the University of Tartu Feasibility Fund (grant number PLTOMARENG51), and the European Structural and Investment Funds.Peer reviewedPublisher PD

Characterisation of Electrochemical Sensor-Array for Utilisation in Construction of BOD Bioelectronic Tongue

There is need to rapidly measure biochemical oxygen demand (BOD) to estimate organic pollution in wastewater. Biosensors are able to estimate BOD values within 5–30 minutes, but they have some limitations that can be overcome with biosensor-array. This work used sensor-array, which consists of 8 × 3 electrodes. The working electrode was inner Pt circle electrode, counter electrode was a Pt band electrode and the reference electrode was a silver wire. The potentiostat was used to record cyclic voltammetry and chronoamperometry. The pumping speed was set at 1.5 cm3 min−1 or higher, to avoid the interference. Next, sensor-array was tested to measure different oxygen amounts and calibrated accordingly. Lastly, Pseudomonas putida membranes were calibrated and used to estimate BOD value. The calibration gave linear range up to 85 mg L−1 of BOD and sensitivity from 0.0018 to 0.0068. Real industrial wastewater, from lignocellulosic bioethanol production, was used to test the biosensor-array. It underestimated BOD values from 8 to 37 %. This biosensor-array allows to measure BOD value in less than 15 minutes

Influence of Chromium Carbide-Derived Carbon Support and Ceria Nanocrystals on Pt–CeO2/C Catalysts for Fuel Cell Applications

The influence of different synthesis parameters on CeO _2 and Pt nanoparticle (NP) deposition on Ketjenblack carbon (C(KB)) was examined. The Pt NP diameter (3.1–4.1 nm) was not influenced by CeO _2 synthesis parameters. The CeO _2 NPs synthesized using ultrasound sonication contribute to a better durability of the Pt–CeO _2 /C against CO poisoning. In contrast, CeO _2 synthesized using the microwave heating method contributes to better methanol oxidation reaction (MOR) activity at low electrode potential. Synthesis parameters of CeO _2 and Pt NPs developed for the C(KB)-based catalysts were applied for C(Cr _3 C _2 )-based catalysts. The Pt NP diameter of C(Cr _3 C _2 )-based catalysts was slightly higher (7.2 nm) as some Pt NPs were agglomerated. The C(Cr _3 C _2 ) support facilitates the MOR and CO stripping, especially in the case of the Pt/C on C(Cr _3 C _2 ) support. The MOR activity at 0.85 V of Pt NPs on the C(Cr _3 C _2 ) support is as good as the MOR activity for the best Pt–CeO _2 on the C(KB) support. The C(Cr _3 C _2 ) support also improves the CO removal from the Pt surface. All the synthesized catalysts had better MOR activity than the commercial Pt/C(Vulcan) catalyst. The oxygen reduction reaction activity of Pt–CeO _2 /C catalysts with higher CeO _2 content synthesized with the microwave heating method was very good

Enhanced and copper concentration dependent virucidal effect against SARS-CoV-2 of electrospun poly(vinylidene difluoride) filter materials

Summary: Virucidal filter materials were prepared by electrospinning a solution of 28 wt % poly(vinylidene difluoride) in N,N-dimethylacetamide without and with the addition of 0.25 wt %, 0.75 wt %, 2.0 wt %, or 3.5 wt % Cu(NO3)2 · 2.5H2O as virucidal agent. The fabricated materials had a uniform and defect free fibrous structure and even distribution of copper nanoclusters. X-ray diffraction analysis showed that during the electrospinning process, Cu(NO3)2 · 2.5H2O changed into Cu2(NO3)(OH)3. Electrospun filter materials obtained by electrospinning were essentially macroporous. Smaller pores of copper nanoclusters containing materials resulted in higher particle filtration than those without copper nanoclusters. Electrospun filter material fabricated with the addition of 2.0 wt % and 3.5 wt % of Cu(NO3)2 · 2.5H2O in a spinning solution showed significant virucidal activity, and there was 2.5 ± 0.35 and 3.2 ± 0.30 logarithmic reduction in the concentration of infectious SARS-CoV-2 within 12 h, respectively. The electrospun filter materials were stable as they retained virucidal activity for three months

Symmetric Potentiometric Cells for the Measurement of Unified pH Values

A unified pH scale of absolute values (pHabs scale) enables the comparison of acidities in different solvents. To date, very few different experimental setups have been used for the measurement of values on this scale. The article describes the design and performance of the different symmetric cells used for unified pH measurement by several institutions. Well-established and reliable standard aqueous buffer solutions are the first step of method validation necessary to achieve a robust metrological level for more complex media. The pH of aqueous standard buffers was measured by differential potentiometry, where the potential between two glass electrodes is measured directly. All the tested electrochemical cells prove to be suitable for unified pH measurements. This validation highlights that the method is, to a large extent, independent of the used equipment, including the cell geometry. The inherent symmetry of the cell design helps to reduce the experimental workload and improve the accuracy of obtained results