A Mini Review on Liquid Phase Catalytic Exchange for Hydrogen Isotope Separation: Current Status and Future Potential
, Nur Najwa Abdul Talib 1 and Liew Chin Seng 1
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors
Liquid Phase Catalytic Exchange (LPCE) is an emerging technology for the separation of hydrogen isotopes, particularly for extracting tritium from nuclear effluents. This paper offers an overview of the latest developments in hydrophobic catalysts used in the LPCE process, covering LPCE fundamentals, factors affecting its efficiency, and future research directions. There has been shown that the notable progress in the development of hydrophobic catalysts, especially those involving platinum with a secondary metal or modified support. These catalysts have demonstrated enhanced activity and stability, resulting in greater separation efficiencies within the LPCE process. The paper concludes by identifying potential research areas and challenges for advancing the sustainability of LPCE in hydrogen isotope separation, including optimization of modified catalyst materials, scalability, techno-economic analysis, and life cycle assessment.
In my view, the paper is well-written. The review describes the topic completely. I confidently recommend its acceptance in the journal "Sustainability".
Author Response
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Reviewer 2 Report
Comments and Suggestions for AuthorsThe mini-review summarizes the recent research on liquid phase catalytic exchange as a highly promising technology for separation of hydrogen isotopes. This approach has been demonstrated to be less energy-intensive and characterized by a high separation factor. This paper provides an overview of the current development of hydrophobic catalysts used in the liquid phase catalytic exchange process, including the fundamentals of the process, factors affecting the efficiency, and the future outlook. The role of the active metal in catalysts, catalyst supports, and operating conditions on the overall efficiency has been discussed. The following comments should be taken into account in the revision of the manuscript.
1. The role of the porosity of the support on the performance in LPCE should be discussed.
2. LPCE in some cases is spelled as LCPE.
3. The G/L parameter (presumably, gas-to-liquid) should be disclosed in the abstract, some people read only abstract and everything in the abstract should be clearly stated.
Comments on the Quality of English LanguageThe quality of English language is satisfactory
Author Response
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Reviewer 3 Report
Comments and Suggestions for AuthorsIn this work, the authors provided an overview of the current development of hydrophobic catalysts used in the Liquid phase catalytic exchange (LCPE) process, including the LPCE fundamentals, factors influencing its effectiveness, and proposals for future research areas. The authors also highlighted the potential research areas and challenges for future advancements in the sustainability of LCPE for hydrogen isotope separation. Overall, this manuscript is well prepared, thus can be published after revision.
1. What is the meaning of the label “exist” in Figure 2?
2. A more detailed illustration of the hydrogen isotope separation using LPCE technology can be provided in Figure 3.
3. The English should be improved, for example, in the abstract “It specifically reviews the active metal catalysts, catalyst supports, operating temperature, and G/L ratio”.
4. Some recent studies can be cited: Angew. Chem. Int. Ed. 2024,63, e202316208; 10.1021/acscatal.2c03842; 10.1016/j.xcrp.2022.100949.
5. Table 2 contains only bimetallic catalysts for LCPE. The authors should also include other types of catalysts into Table 2.
Comments on the Quality of English LanguageMinor editing of English language required.
Author Response
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Reviewer 4 Report
Comments and Suggestions for Authors
Sustainability 2024, 16, x. https://doi.org/10.3390/xxxxx April may 2024
A Mini Review on Liquid Phase Catalytic Exchange for Hydrogen Isotope Separation….
Siti Munirah Mhd Yusof, Serene Lock Sow Mun and Nur Najwa Abd Talib
This mini review is treating an interesting subject, well written but with some defects such as i/ too repetitive (concision is needed in many sentences and many §§), and
ii/ lacking for some important information.
Starting with this second point, reviewer thinks that the caption of the Figures 3, 4, 5 must be seen again to better explain what was shown: in Figure 3 for example, some parts of the schema do not have names; in Figure 4, a hydrophilic packing is presented but the reader does not now its composition, as no data are present in the Figure and no explanation appeared in the text; the same is true in Figure 5.
In the description of catalysts section, it was said that a problem exists due to the price of Platinum, to justify the study of bimetallic samples: but add Iridium or Ruthenium in place of Platinum will not decrease the price of the catalyst as these elements are not less expensive than Pt; furthermore, the regeneration or recycling of these bimetallic samples will be much more complicated and then more expensive. The use of non-noble metals is therefore more important.
In Tables 2 and 3, a column is dedicated to particle size values, but how these values were calculated is not detailed in the Tables and are not commented in the text. The measure of active metal particle size is not trivial and depending on the measurement technique different results can be obtained: TEM observations are based on contrast and verification of the nature of the metal particle (case of bimetallic catalysts) is not easy; chemisorption too is not very useful to identify each species, SAXRS is scarcely used, CO adsorption through FTIR detection is also complicated. Then the way the particle size was measured is necessary, as seems necessary the toral surface area of the different catalysts supports mentioned in both Tables.
In Table 2, some catalysts names are difficult to understand cf “Pt3Fe-MI-H is highest “
In Table 3, are we dealing with LPCE or LCPE? See Figure caption and the corresponding text. In the same Table, an idea of the specific surface area of the supports could be useful.
On line 250 and following, abbreviations are not detailed: see SDB, PVDF,
Line 280, 281: “Most experiments investigating hydrogen isotope separation through LPCE methods have examined temperatures ranging from room temperature to 90 °C.”: it is difficult to understand how an “experiment” can “examine” a fact.
On point i/, reviewer thinks that many sentences can be shortened and that a new reading by the authors would be useful to suppress or limit redundancy. See for example:
a/ “Hence, the use of packing in a packed column is known to have a good impact on the gas-liquid mass transfer process in various gas-liquid mass transfer process applications because it increases the interfacial area”: such a sentence needs a new writing.
b/ “The catalyst plays a big role in the isotopic exchange process as the exchange does not take place in the absence of the catalyst [32]. One of the key factors in the LPCE process is the choice of catalysts [43]. The catalyst consists of the active metal, support and hydrophobic coating. The active metal plays a crucial role in the catalytic exchange reaction. It facilitates the exchange of hydrogen isotopes with water vapor to form deuterium oxide (D2O) or heavy water”: Such §§ can be summarized.
c/ “Another study by Hu et al. (2010) investigated the addition of Ru and RuO2 into Pt/C/PTFE catalyst and found that the Ru modification significantly improved the catalytic activity due to the presence of Ru either in alloy or hydrous oxide form [44]. This finding is supported by Ye et al. (2014) who reported the addition of various second metals on the Pt/C/PTFE catalyst and found that the Pt3M catalysts (where M represents the second metal) exhibited higher catalytic performance compared to pure Pt due to the dissociation of water molecules on the doped metal and their oxides [45]”: a study cannot find something, it can show; the end of this statement is not obvious and needs a more scientific approach/description/basement.
Many other comments need a new reading and simplification of the expressions.
Comments on the Quality of English Languagesee what was reported before
Author Response
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Round 2
Reviewer 3 Report
Comments and Suggestions for AuthorsThe manuscript can be accepted.
