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Electrolytic Treatment of Wastewater for Reuse Purposes
Published in Iqbal M. Mujtaba, Thokozani Majozi, Mutiu Kolade Amosa, Water Management, 2018
EC has a number of benefits [11]: compatibility, amenability to automation, cost effectiveness, energy efficiency, safety and versatility. Although EC received little scientific attention a decade ago, in the last couple of years this technology has been widely used for the treatment of dilute wastewaters contaminated by heavy metals [12], foodstuff [13,14], oil wastes [15,16], textile and dyes [17,18], fluorine [19], polymeric wastes [20], organic matter from landfill leachate [21], suspended particles [22,23], chemical and mechanical polishing wastes [24], aqueous suspension of ultrafine particles [25], nitrate [26], phenolic waste [27], arsenic [28] and refractory organic pollutants including lignin and EDTA [29]. EC is also applicable for drinking water treatment [30,31]. This process has the capability to overcome the disadvantages of other treatment techniques. Use of EC and EF techniques is advantageous because the plant is modular, the operation is continuous, it requires only electric power for operation, it does not require chemicals (except in a few cases in order to adjust pH), has a smaller footprint, does not create biological waste sludge, has an automated system, has no noise, has lower power consumption, the treatment is flexible and suitable for a wide range of contaminants at different levels, and the temperature and pressure required are low.
Energy-efficient electrical systems, controls and metering
Published in Paul Tymkow, Savvas Tassou, Maria Kolokotroni, Hussam Jouhara, Building Services Design for Energy-Efficient Buildings, 2020
Paul Tymkow, Savvas Tassou, Maria Kolokotroni, Hussam Jouhara
The factors that should be considered in the selection of an indoor climate control system are described in Chapter 7. While it may not be the preferred system in terms of energy performance, there is often a strong economic case to use a traditional fan coil unit (FCU) solution, particularly in commercial offices. Although FCUs may not be the favoured choice for energy efficiency in most circumstances, they can be made much more efficient by using fan motors that are electronically commutated (EC) instead of conventional single-phase motors. EC motors are also known as direct current (DC). In an EC/DC motor, power electronic devices create a rotating magnetic field in the stator winding. The motor contains a permanent magnet. For FCUs using this drive technology, carbon emissions can be reduced in the following ways (Blackwell 2010): they are more efficient than an equivalent single-phase alternating current (AC) motor; typically up to 90% efficiency, compared to in the order of 50%variable-speed operation can be achieved without any reduction in efficiency, allowing matching of the motor speed to the required air flow rate at the commissioning stagethe fan speed can be varied in response to different load conditions, using suitable controls based on demand to provide variable-volume operationthey do not incur the problem associated with heat transfer to the air from a less efficient motor as with a conventional FCU, which avoids the increase in load on the cooling coil, and hence reduces the cooling energy requirement. Therefore, EC/DC FCUs should be the preferred choice when a decision has been made to use them in areas with high cooling loads (Blackwell 2010), subject to the electrical design considerations described next.
Thermoelectric properties and thermal stability of ferromagnetic half metallic CoVTe alloy, first principles study
Published in Philosophical Magazine, 2022
T. Djaafri, A. Djaafri, A. Bendjedid, F. Saadaoui, K. Hamada, K. Korichi, K. Berriah
The cohesive energy Ec is also calculated using the formula (14), to study the structural stability of this compound [48]: where is the total energy of the considered compound, are the energies of isolated constituent atoms in CoVTe compound. The computed result of Ec is 3.402 (eV/atom). The positive value of the cohesive energy Ec reveals that CoVTe compound is expected to be structurally stable.
Defluoridization of drinking water by electrocoagulation (EC): process optimization and kinetic study
Published in Journal of Dispersion Science and Technology, 2019
As variation in current density results in changes in electron flow rate in EC, CD is considered an important operating parameter that significantly affected the EC process.[1, 17, 19] In order to evaluate the effect of CD on fluoride removal efficiency and to determine the economical one current density of 17.29 A/m2, 43.1 A/m2, 86.22 A/m2, 129.31 A/m2, 172.41 A/m2, 258.62 A/m2 were considered in this work and results are shown in Figure 3. It can be observed from the figure that at lower CD i.e. 17.29 A/m2, the concentration of fluoride ion decreases from 10 mg/L to 3.68 mg/L (63% removal efficiency) after 40 minutes of EC. For increased CD of 43.1, 86.22, 129.31, 172.41 and 258.62 A/m2, residual fluoride ion concentration decreases to 2.5, 1.24, 0.29, 0.19, and 0.10 mg/L, respectively. Corresponding removal efficiency are 74.00%, 87.60%, 97.12%, 98.10% and 99.00%. Decrease in fluoride ion concentration with increase in CD was due to higher production of Al+3 ion from the anode, which increases the fluoride ion removal. As per WHO guideline, maximum permissible level of fluoride concentration i.e. 1.5 mg/L can be obtained from 10 mg/L of fluoride solution after 20 minutes with CD of 172.41 A/m2 and after 25 minutes with CD of 129.310 A/m2. It may also be observed that increasing the CD after a certain value (172.41 A/m2) does not affect much in removal rate of fluoride ions. This may be explained by the reason that with increase in CD, the rate of production of Al+3 ion from anode increased. Due to polymerization reaction of excess Al ions, it creates insoluble Al flocs and separated from soluble fluoride ion rich water. Hence at initial stages, excess CD increases the fluoride ion removal but for the long term application, higher CD is not so much useful. Considering the above fact, lower CD of 129.31 A/m2 was considered in the further experiments. It is to be noted that, in EC process, CD determines rate of coagulant production, bubble production, size and growth of flocs which plays a vital role in removal efficiency of EC. For continuous process or water with different fluoride ions concentration, TDS, pH, etc., suitable variations in CD are necessary for treatment of water to keep the fluoride ion concentration and other quality parameters within desirable limit.
The interaction of carbon-centered radicals with copper(I) and copper(II) complexes*
Published in Journal of Coordination Chemistry, 2018
Thomas G. Ribelli, Krzysztof Matyjaszewski, Rinaldo Poli
A most interesting way to generate an organocopper(II) species, which is quite relevant to OMRP and CRT, was recently introduced by Zerk and Bernhardt [102] making use of an electrochemical ATRP activation strategy for radical generation. The typical ATRP initiators ethyl 2-bromoisobutyrate, bromoacetonitrile and chloroacetonitrile were used in this study. The active ATRP catalysts [L/CuI]+ (L = TPMA, Me6TREN) were generated in situ by electrochemical reduction of the corresponding [L/CuIIX]+ ions in cyclic voltammetric or spectroelectrochemical experiments with ultraviolet (UV)-visible and electron paramagnetic resonance (EPR) monitoring. More specifically, the investigated systems were [TPMA/CuIIBr]+ + RBr (R = CMe2(COOMe), CH2CN) and [Me6TREN/CuIIX]+ + XCH2CN (X = Cl, Br), using either DMSO or MeCN as solvents. In the cyclic voltammetry experiment, following the one-electron reduction of [L/CuIIX]+, a new reduction wave at more negative potential, which is visible only in the presence of RX, is attributed to the reduction of the [L/CuII−R]+ product formed by the sequence of reactions shown in Scheme 6. The starting [L/CuII−X]+ complex is first reduced, with loss of X–, at the potential E°X, process (a). The electron addition and rapid X– loss yield a single wave for a coupled EC process). This generates the ATRP activator complex [L/CuI]+in situ within the diffusion layer. In a second process (b), the latter species activates RX to generate the free radical R• by the typical ATRP activation process and reforms the deactivator complex [L/CuII−X]+. The electrochemically generated [L/CuI]+ complex, which is still the dominant species in the diffusion layer at E < E°X, traps the radical in the third step (equivalent to an OMRP deactivating process) to generate the organocopper(II) species [L/CuII−R]+ in process (c). The latter species, in a fourth step (d), is finally reduced to [L/CuI-R] at the potential E°R. Use of the tertiary radical generated from ethyl 2-bromoisobutyrate did not lead to sufficiently stable [L/CuII−CMe2(COOEt)]+ products (no appearance of the reduction wave at E°R), whereas a distinct reduction wave appears for the experiments carried out with the ATRP initiators chloro- and bromoacetonitrile, which generate [L/CuII−CH2CN]+ transients.