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Comment on the paper “Generation and reduction of bulk nanobubbles by ultrasonic irradiation” by Keiji Yasuda, Hodaka Matsushima, and Yoshiyuki Asakura, Chemical Engineering Science 195 (2019) 455–461
Chemical Engineering Science xxx (xxxx) xxx
Contents lists available at ScienceDirect
Chemical Engineering Science journal homepage: www.elsevier.com/locate/ces
Letter to the Editor
Comment on the paper ‘‘Generation and reduction of bulk nanobubbles by ultrasonic irradiation” by Keiji Yasuda, Hodaka Matsushima, and Yoshiyuki Asakura, Chemical Engineering Science 195 (2019) 455–461 Chang Peng Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC 27695, USA
a r t i c l e
i n f o
Article history: Received 5 May 2019 Accepted 25 May 2019 Available online xxxx
a b s t r a c t Comment is provided on some doubtful results included in the published paper, Yasuda et al. (2019).
Keywords: Nanobubble Ultrasonic power Number concentration Frequency
Comment In the last sentence of Results section in the published paper (corresponding to the first paragraph of page 458) (Yasuda et al., 2019), the authors made the following statement: ‘‘The number concentration of nanobubbles decreased with increasing ultrasonic power.”. This statement was made when the authors were talking about their experimental results in Figure 5 (Yasuda et al., 2019). However, the results in Figure 5 only showed the effect of ultrasonic frequency (22, 43, 129, 488, and 1000 kHz) on the change in number concentration of nanobubbles in nanobubble water. All the experimental results in Figure 5 were obtained at the fixed ultrasonic power, 15 Watt. It is pretty clear that the conclusion ‘‘The number concentration of nanobubbles decreased with increasing ultrasonic power.” cannot be derived from results showed in Figure 5, or any other results the authors showed in the paper. The authors made a statement in the published paper, but no result can prove it. Corresponding to the discussion of results in Figure 8 (last paragraph in page 459) (Yasuda et al., 2019), the authors investigated the effect of ultrasonic frequency on the equilibrium number concentration of nanobubbles in ultrapure and nanobubble water. The authors made the following statement: ‘‘The equilibrium number concentration of nanobubbles in ultrapure water are same as those in nanobubble water”. Apparently, the authors did not show the two measured result plots separately in Figure 8 for the ultrapure E-mail address: [email protected]
Ó 2019 Elsevier Ltd. All rights reserved.
and nanobubble water changing with ultrasonic frequency. Readers cannot take for granted that the single plot in Figure 8 stands for the experimental results for both ultrapure and nanobubble water. Thus, this statement can not be well proved by the results showed in Figure 8. Furthermore, the equilibrium number concentration of nanobubbles in ultrapure and nanobubble water actually can be obtained from Figure 4 and Figure 5 (Yasuda et al., 2019), respectively. For instance, for the ultrasonic frequency at 22 kHz, the equilibrium number concentration of nanobubbles in ultrapure water is 1.15 109/mL from Figure 4; however, the equilibrium number concentration of nanobubbles in nanobubble water is 1.8 109/mL from Figure 5. The equilibrium number concentrations of nanobubbles in ultrapure water are not the same as those in nanobubble water. The statement made by the authors here is not right. In addition, corresponding to the results in Figure 8 (last paragraph in page 459) (Yasuda et al., 2019), the authors made the statement: ‘‘The equilibrium number concentration was independent of ultrasonic power.”. Here the authors made a statement, but also no any other results in the published paper can prove it. Although from Eq. (3) readers may derive that the equilibrium number concentration was independent of ultrasonic power, the authors did not provide any experimental results in the published paper to prove this conclusion. The results in Figure 8 and Eq. (3) cannot make readers convinced of the statement. Taking into account of the above comments on the published paper, Yasuda et al. (2019), some results presented in the paper are doubtful.
https://doi.org/10.1016/j.ces.2019.05.053 0009-2509/Ó 2019 Elsevier Ltd. All rights reserved.
Please cite this article as: C. Peng, Comment on the paper ‘‘Generation and reduction of bulk nanobubbles by ultrasonic irradiation” by Keiji Yasuda, Hodaka Matsushima, and Yoshiyuki Asakura, Chemical Engineering Science 195 (2019) 455–461, Chemical Engineering Science, https://doi.org/ 10.1016/j.ces.2019.05.053
2
C. Peng / Chemical Engineering Science xxx (xxxx) xxx
Declaration of Competing Interest The authors whose names are listed immediately below certify that they have NO affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or
non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript. References Yasuda, K., Matsushima, H., Asakura, Y., 2019. Generation and reduction of bulk nanobubbles by ultrasonic irradiation. Chem. Eng. Sci. 195, 455–461.
Please cite this article as: C. Peng, Comment on the paper ‘‘Generation and reduction of bulk nanobubbles by ultrasonic irradiation” by Keiji Yasuda, Hodaka Matsushima, and Yoshiyuki Asakura, Chemical Engineering Science 195 (2019) 455–461, Chemical Engineering Science, https://doi.org/ 10.1016/j.ces.2019.05.053
Contents lists available at ScienceDirect
Chemical Engineering Science journal homepage: www.elsevier.com/locate/ces
Letter to the Editor
Comment on the paper ‘‘Generation and reduction of bulk nanobubbles by ultrasonic irradiation” by Keiji Yasuda, Hodaka Matsushima, and Yoshiyuki Asakura, Chemical Engineering Science 195 (2019) 455–461 Chang Peng Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, NC 27695, USA
a r t i c l e
i n f o
Article history: Received 5 May 2019 Accepted 25 May 2019 Available online xxxx
a b s t r a c t Comment is provided on some doubtful results included in the published paper, Yasuda et al. (2019).
Keywords: Nanobubble Ultrasonic power Number concentration Frequency
Comment In the last sentence of Results section in the published paper (corresponding to the first paragraph of page 458) (Yasuda et al., 2019), the authors made the following statement: ‘‘The number concentration of nanobubbles decreased with increasing ultrasonic power.”. This statement was made when the authors were talking about their experimental results in Figure 5 (Yasuda et al., 2019). However, the results in Figure 5 only showed the effect of ultrasonic frequency (22, 43, 129, 488, and 1000 kHz) on the change in number concentration of nanobubbles in nanobubble water. All the experimental results in Figure 5 were obtained at the fixed ultrasonic power, 15 Watt. It is pretty clear that the conclusion ‘‘The number concentration of nanobubbles decreased with increasing ultrasonic power.” cannot be derived from results showed in Figure 5, or any other results the authors showed in the paper. The authors made a statement in the published paper, but no result can prove it. Corresponding to the discussion of results in Figure 8 (last paragraph in page 459) (Yasuda et al., 2019), the authors investigated the effect of ultrasonic frequency on the equilibrium number concentration of nanobubbles in ultrapure and nanobubble water. The authors made the following statement: ‘‘The equilibrium number concentration of nanobubbles in ultrapure water are same as those in nanobubble water”. Apparently, the authors did not show the two measured result plots separately in Figure 8 for the ultrapure E-mail address: [email protected]
Ó 2019 Elsevier Ltd. All rights reserved.
and nanobubble water changing with ultrasonic frequency. Readers cannot take for granted that the single plot in Figure 8 stands for the experimental results for both ultrapure and nanobubble water. Thus, this statement can not be well proved by the results showed in Figure 8. Furthermore, the equilibrium number concentration of nanobubbles in ultrapure and nanobubble water actually can be obtained from Figure 4 and Figure 5 (Yasuda et al., 2019), respectively. For instance, for the ultrasonic frequency at 22 kHz, the equilibrium number concentration of nanobubbles in ultrapure water is 1.15 109/mL from Figure 4; however, the equilibrium number concentration of nanobubbles in nanobubble water is 1.8 109/mL from Figure 5. The equilibrium number concentrations of nanobubbles in ultrapure water are not the same as those in nanobubble water. The statement made by the authors here is not right. In addition, corresponding to the results in Figure 8 (last paragraph in page 459) (Yasuda et al., 2019), the authors made the statement: ‘‘The equilibrium number concentration was independent of ultrasonic power.”. Here the authors made a statement, but also no any other results in the published paper can prove it. Although from Eq. (3) readers may derive that the equilibrium number concentration was independent of ultrasonic power, the authors did not provide any experimental results in the published paper to prove this conclusion. The results in Figure 8 and Eq. (3) cannot make readers convinced of the statement. Taking into account of the above comments on the published paper, Yasuda et al. (2019), some results presented in the paper are doubtful.
https://doi.org/10.1016/j.ces.2019.05.053 0009-2509/Ó 2019 Elsevier Ltd. All rights reserved.
Please cite this article as: C. Peng, Comment on the paper ‘‘Generation and reduction of bulk nanobubbles by ultrasonic irradiation” by Keiji Yasuda, Hodaka Matsushima, and Yoshiyuki Asakura, Chemical Engineering Science 195 (2019) 455–461, Chemical Engineering Science, https://doi.org/ 10.1016/j.ces.2019.05.053
2
C. Peng / Chemical Engineering Science xxx (xxxx) xxx
Declaration of Competing Interest The authors whose names are listed immediately below certify that they have NO affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or
non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript. References Yasuda, K., Matsushima, H., Asakura, Y., 2019. Generation and reduction of bulk nanobubbles by ultrasonic irradiation. Chem. Eng. Sci. 195, 455–461.
Please cite this article as: C. Peng, Comment on the paper ‘‘Generation and reduction of bulk nanobubbles by ultrasonic irradiation” by Keiji Yasuda, Hodaka Matsushima, and Yoshiyuki Asakura, Chemical Engineering Science 195 (2019) 455–461, Chemical Engineering Science, https://doi.org/ 10.1016/j.ces.2019.05.053