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Nanoscale electrokinetic phenomena
Published in Zhigang Li, Nanofluidics, 2018
In the past decade, electrokinetic flows in CNTs have been extensively studied. Ion transport in CNTs has wide applications in biology, medicine, and engineering, including molecular detection and manipulation, drug delivery, flow sensing, energy conversion, and harvesting. Carbon nanotube-based nanofluidic platforms are quite diverse, from CNT membranes to novel devices containing single CNTs. In addition to stochastic current fluctuations introduced in the previous section, many other unique transport phenomena have been revealed, which will be discussed in this section.
Electrochemical behaviour of graphene and alumina whisker co-reinforced copper matrix composites
Published in Corrosion Engineering, Science and Technology, 2023
Zhenyi Shao, Xubo Li, Yanhong Wei, Jianrun Chen, Qing Qin, Yong Xian, Yichao Ding
Figure 6 shows SEM images and corresponding EDS spectra of Gr/Cu-0.25 composite after electrochemical corrosion in an alkaline environment. As shown in the figure, granular corrosion products are observed on the surface, identified as copper oxides according to the EDS result of spot 2. Some black fibrous materials can also be observed on the surface of the composite, identified as graphene according to the EDS result of spot 3. The large granular material at spot 1 is the Al2O3 whisker. The electrochemical behaviour of Al2O3 whisker and graphene in an alkaline environment is consistent with that in a neutral environment. No apparent corrosion products are produced on the surface of graphene and Al2O3 whisker, indicating the exchange barrier effect of the graphene and Al2O3 whisker between electrochemical particles; in addition, the ion transport path of electrochemical redox is significantly isolated.
Utilization of vetiver grass containing metals as lignocellulosic raw materials for bioethanol production
Published in Biofuels, 2021
Elvi Restiawaty, Arinta Dewi, Yogi Wibisono Budhi
Figure 4 shows that the addition of Al(iii) can increase glucose production. Similarly, Wang et al. [11] found that the activity of cellulase enzyme increased with a concentration of Al(iii) below 1 mM, while the enzyme activity decreased sharply when Al(iii) concentration was varied from 1 to 10 mM. Under these conditions the Al ion acted as a noncompetitive inhibitor for cellulase, in which the inhibitor bound to enzymes at a site other than the active site [24]. Al(iii) can increase cellulase activity by changing the enzyme’s dimensional structure at concentrations below 1 mM. When the changes reach a certain limit, the activity of enzymes decreases substantially and results in threshold effect of Al(iii). On the other hand, a higher concentration of Al(iii) can decrease enzyme activity for bioethanol production (see Figure 5). Possible mechanisms of aluminum toxicity in microorganisms include acidification of the medium, binding to membrane components, binding to enzymes or substrates, substitution for magnesium, inhibition of ion transport, deoxyribonucleic acid (DNA) binding, adenosine triphosphate (ATP) binding, or inhibition of ATP synthesis [25].
The multi-functional system of electrochemical desalination, RhB degradation and Cr (VI) removal
Published in Environmental Technology, 2022
Yuchao Zhu, Qiang Wei, Qinyu He, Deyang Chen, Than Zaw Oo, Su Htike Aung, Fuming Chen
Figure 3 displays the electrochemical desalination, rhodamine B and dichromate removal at current densities of 0.5, 1.0, 1.5 and 2.0 mA·cm−2. With raised current density, the voltage plateau increases due to the polarisation influence. The right axis of the graph displays the conductivity change in the salt stream. The conductivity slope increases with the raised current density. The high current density can drive a fast ion movement across the membrane within the system, resulting in a quick salt removal rate. The slope can be restored close to the initial value when 1 mA·cm−2 was applied after the 2 mA·cm−2 operations. In addition, the degradation performance of RhB and dichromate removal are shown in Figure 3(b). The slope of the curve represents the degradation rate of RhB and the removal rate of dichromium ions. As the increase of the current density, the degradation rate of RhB and the removal rate of dichromium ions are enhanced. Hence, a fast treatment process can be obtained in the high current density. The S@rGO electrode can raise the outstanding electro-oxidation performance, which promotes the occurrence of a redox reaction, electron transportation and accelerates the degradation and removal of pollutants. [44] The results with the highly concentrated salt feed using the current system are demonstrated in Figure S6. The concentration of the salt feed can affect the desalination performance. The potential varies for different salt feeds in Figure S6(a). During the charge-desalination process, the salt concentration decreases continuously due to the rapid capture of chloride and sodium ions. At the same time, the rhodamine B and chromium ion concentrations were decreasing, as shown in Figure S6(b) and Figure S6(c), respectively. It is also observed that the degradation rates of rhodamine B and chromium ions were significantly accelerated at high salt feed concentrations. This may be due to the low polarisation of the charge voltage through the membrane between the electrodes, which accelerates ion transport and enhances the redox reaction. [45,46]