Recent Advances in Platinum and Palladium Solvent Extraction from Real Leaching Solutions of Spent Catalysts
Round 1
Reviewer 1 Report
The work can be published after minor corrections. The most important chemical reactions for the extractants listed in Table 2 should be given, in particular for the extraction of Pd and Pt with oximes, thiacalixarenes. Z. Kolarik's work on the extraction of platinum metals from spent nuclear fuel should be quoted.
Author Response
Please read the attached file.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The work focuses on the review of recent advances on Pt and Pd solvent extraction from real leaching solutions of spent catalysts. Platinum and palladium are one of the most desirable metals in the world, therefore PGM recycling is very important. Moreover, hydrometallurgy can be a good alternative to pyrometallurgy. Comments and suggestions which an author may find useful in upgrading manuscript are the following:
1. Figure 1: figures should be captioned (a) and (b), e. g. “(a) platinum” and “(b) palladium”.
2. Line 51: Why PGM are difficult to replace? It should be explained. Why are they so unique? The physical and chemical properties of PGM should be added into the manuscript.
3. Line 54: A comparison of PGM content in natural and secondary resources should also be presented. Naturally, recycling is required, but is it also profitable?
4. Table 2 and line 380: “(unknown concentrations)” in the manuscript [59 - Rzelewska-Piekut, M.; Paukszta, D.; Regel-Rosocka, M. Hydrometallurgical recovery of platinum group metals from spent automotive converters. Physicochem. Probl. Miner. Process. 2021, 57, 83−94] there is an information about the volume ratio of HCl:H2SO4:H2O2; 40 cm3 of 36% HCl to 2.5 of 98% H2SO4 to 2.5 cm3 of 30% H2O2. The concentrations can be easily calculated.
5. Other comments:
- line 215, equation (3): is “. 2 TBP (org)” bur it should be “· 2 TBP (org)”,
- Table 2: please expand the abbreviation of "SCS",
- Line 357: Cyphos IL 104 is a commercial name of the ionic liquid. Please give the systematic name of the compound Cyphos IL 104.
6. Line 395: publication [61]: Extraction of PGMs from real solutions is difficult, because non-precious metal ions are coextracted with PGM. Separation of impurities using extraction from PGMs is problematic. It should be taken into account: should the impurities be removed? It depends on the further application of the solutions. In publication [M. Rzelewska-Piekut, Z. Wolańczyk, M. Nowicki, M. Regel-Rosocka, Precipitation of Pt, Pd, Rh, and Ru Nanoparticles with Non-Precious Metals from Model and Real Multicomponent Solutions, Molecules 2023, 28(13), 5188; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules28135188], the authors precipitated PGMs from real solutions containing impurities, e.g. Fe(III). The conclusions are promising: the precipitate (catalyst) containing Pt, Pd and Fe nanoparticles obtained from the real solution had a satisfactory catalytic activity, which was confirmed by the 4-nitrophenol conversion of 86% after 30 min at pH 11 with the use of 3 mg of the catalyst. Thus, this shows that there is no need to purify real leach solutions from ions of non-precious metals before the precipitation of PGM nanoparticles.
Author Response
Please read the attached file.
Author Response File: Author Response.pdf
Reviewer 3 Report
This manuscript provides an overview of the recent advancements in solvent extraction of platinum and palladium from real leaching solutions of spent catalysts. To inform the readers about the nature of this review, it is important to specify the type of review article, such as systematic review, rapid review, scoping review, critically appraised topic, or narrative review. Additionally, including methodological details will help readers gain a better understanding of the approach employed in this review.
Abstract: Due to this manuscript is a review, the period of review should be declared to let the reader know about timing period.
Introduction: The introduction lacks organization and coherence. The paragraphs within the introduction do not have a clear relationship with each other. It is crucial for the author to restructure this section. Moreover, to ensure a clear understanding for the reader, additional information should be included regarding the problem of solvent extraction from real leaching solutions of spent catalysts. Additionally, recent techniques employed to address this problem should be introduced.
- Figure 1: To enhance the visibility of the two pie charts, the author should consider revising the colors of the legends to be the same for each category. For example, the color "green" could be used for both dental and biomedical, while "dark blue" could be used for pollution control.
Hydrometallurgy: In this section, numerous extractants are discussed. It is crucial for the authors to address the advantages and disadvantages of these extractants and try to categorize them based on their mechanisms. This categorization will enhance the novelty of this review and provide a comprehensive understanding of the different approaches employed.
Conclusions and future perspectives: The conclusion was not well managed, the main content of some paragraphs is duplicate (e.g., line: 555–578 is duplicated with line 514–554). In addition, the discussion on the pros and cons between hydrometallurgy and solvemetallurgy should be stated in this conclusion.
Author Response
Please read the attached file.
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
The authors answered all comments and revised the manuscript as per reviewers' suggestion. The manuscript is good enough to be published.
