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Wastewater Treatment Approaches to Remove Microplastics
Published in Judith S. Weis, Francesca De Falco, Mariacristina Cocca, Polluting Textiles, 2022
Daniel Sol, Amanda Laca, Adriana Laca, Mario Díaz
A recent promising strategy to degrade polystyrene microbeads in water has been described by Kiendrebeogo et al. (2021). Specifically, microplastics can be degraded by anodic oxidation without generation of toxic byproducts. The effect of different parameters on the process has been analyzed, i.e., current intensity, type of oxygen-intensive anodes (Boron-doped diamond (BDD), mixed metal oxide (MMO) and iridium oxide (IrO2)), area of the anode surface and type and concentration of electrolyte (Na2SO4, NaCl, and NaNO3). Results showed that, employing the optimum conditions (BDD, an intensity of 9 A and a supporting electrolyte of 0.03M Na2SO4), after 2 hours of electrooxidation, a degradation of 89% of microplastics was achieved. Thus, the electrooxidation process could be a viable alternative to be applied in real wastewater treatment plants. However, more in-depth research on different aspects of the methodology, such as the pollution derived from the use of the anode, another type of MPs like fibres, as well as the potential interference that water contaminants may cause, should be carried out.
Metal Hydroxide and Oxide Nanocages
Published in Klaus D. Sattler, st Century Nanoscience – A Handbook, 2020
Some mixed metal oxide nanocages can also be used as electrode materials in pseudocapacitors or HSCs. Lou and co-workers [136] reported the designed synthesis of complex hollow Co3O4/NiCo2O4 DSNCs by manipulating the ZIF-67 polyhedron-engaged reactions. When evaluated as electrodes for pseudocapacitors, the Co3O4 /NiCo2O4 DSNCs show a large specific capacitance of 972 F/g at a current density of 5 A/g and remarkable stability with 92.5% capacitance retention after 12,000 cycles (Figure 24.25g,h). Guan et al. [14] have recently demonstrated an HSC device using NiCo2O4 seven-shelled hollow spheres as the battery-type electrode and graphene/multi-shelled mesoporous carbon spheres composites as the capacitive electrode (Figure 24.25i). The HSC device shows an excellent cycling stability with 91.3% of the initial capacitance retained after 10,000 cycles (Figure 24.25j) and a high energy density of 52.6 Wh/kg at a power density of 1,604 W/kg (Figure 24.25k).
How Cathodic Protection Works in Reinforced Concrete
Published in Paul M. Chess, Cathodic Protection for Reinforced Concrete Structures, 2019
For traditional CP systems protecting steel in water, it is considered that one of these two reactions occurs at the anode, depending on whether the water surrounding the primary anode is saline or not. If there is chloride, the chlorine reaction will be favoured. In freshwater, the oxygen production reaction is favoured. In concrete, the situation is likely to be more complex, as there are many compounds, which may react, and this has yet to be fully researched but some relevant testing to date is presented. The primary anode also has an influence, for example, certain components of mixed metal oxide (MMO) anodes favour different reactions. For example, RuO2 favours oxygen production, while IrO2 favours chlorine production. The ratio of the oxygen to chlorine reaction possibly depends on the relative concentrations of water to chloride and the potential difference at the anode to grout interface. Another factor controlling the generation of chlorine or oxygen is the magnitude of the current density applied at the anode surface. The MMO ribbon commonly used for CP in concrete is an IrO2/TaO2 mix, which favours chlorine production (Shrier, 1998).
Electrochemically activated persulfate and peroxymonosulfate for furfural removal: optimization using Box–Behnken design
Published in Environmental Technology, 2023
Emine Can-Güven, Fatih Ilhan, Kubra Ulucan-Altuntas, Senem Yazici Guvenc, Gamze Varank
Experimental studies were conducted in a laboratory-scale electrolytic reactor made of plexiglass material. The dimensions of the reactor were 6.5 cm width x 5 cm length and 9 cm height. Platinum coated Ti (Pt/Ti), ruthenium (IV) oxide coated Ti (RuO2/Ti), graphite, mixed metal oxide coated TiO2 (MMO/TiO2) electrodes as the anode, and titanium electrode as cathode was placed in of the reactor. The distance between the electrodes was 6 cm, and the dimensions of the electrodes were 6 cm width x 12 cm height and 0.1 cm thickness. Graphite anode was a plate electrode while other anodes were mesh electrodes. Potassium nitrate (40 mM) was added to the reactor as an electrolytic solution. 150 mL sample with 250 mg/L furfural concentration was used for each set of the experimental study. The concentration of persulfate and peroxymonosulfate to be added was determined in the preliminary trials. Experimental sets based on reaction time were carried out to select the most effective anode. Pt/Ti, RuO2/Ti, Graphite, MMO/TiO2 electrodes were used as the anode, and Ti was used as the cathode.
AC Corrosion behaviour of aluminium and zinc sacrificial anodes in seawater
Published in Corrosion Engineering, Science and Technology, 2022
Nianpei Tian, Yanxia Du, Yi Liang, Xun Yuan, Le Chen
The schematic diagram of experimental circuit in Figure 1 was used to conduct the weight loss tests. Al and Zn alloy specimens acted as the working electrode (WE) and saturated calomel electrode (SCE) as the reference electrode (RE). The counter electrode (CE) was a mixed metal oxide (MMO), which was based on pure titanium and covered with a ruthenium–iridium coating. Both Al and Zn alloy specimens were subjected to AC current densities of 0, 30, 50 and 100 A m−2 with the frequency of 50 Hz. AC current density was calculated by dividing the AC voltage (root-mean-square value) of the resistor R1 (10 Ω, 2 W) with its resistance and the working area of WE. A slide rheostat (10 kΩ, 2 W) was applied to adjust AC current density to the present value. A capacitor (50 V, 1000 μF) was used as a DC decoupler to cut off the DC circuit. A fuse was used to ensure the safety of circuit. Weight loss tests lasted for 4 days (d).
Accelerated corrosion of pipeline steel under dynamic DC stray current interference
Published in Corrosion Engineering, Science and Technology, 2020
Huimin Qin, Yanxia Du, Minxu Lu, Jie Liu, Xiangjian Zhu
The weight loss measurements were carried out using the experimental set-up depicted in Figure 2, where the working electrode (WE), i.e. pipeline steel was subjected to dynamic DC current corrosion. The mixed metal oxide (MMO) was used as a counter electrode (CE). As shown in the figure, the square wave-shaped current was applied with different current densities and different dynamic periods. Two DC power supplies were adopted to produce dynamic DC square wave current with the assistance of a conversion switch setting at different dynamic periods. A fixed value resistance (10 Ω) was series connected in the circuit to monitor the current flowing through the specimen. The prepared steel specimen was immersed in the quartz sand with solution for 72 h under various current densities, i.e. ±5 mA m−2 and ±10 mA m−2, as well as different dynamic periods, i.e. 10, 30, 60, 80, 100, 160 and 300 s. The tests were performed at ambient temperature (about 20°C) and exposed to air.