Recovery of Magnetic Ni Particles from Spent Catalyst Leachate by Direct Cementation

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Reviewer’s Comments:

 

The author addresses recovery of magnetic Ni particles from spent catalyst leachate by direct cementation. The work is attractive and can recommend for publication after addressing the following minor comments.

 

1. The authors addressed three methods of recover of the materials (Pyrometallurgy, Hydrometallurgy and Hybrid approach but did not explained the third one. Please explain the Hybrid approach and compare it with the selected method.

2. PLS method was used to analyze for metal concentration, need more explaination.

3. BBD and RSM was explained in materials and method section, better to add in Introduction part.

4. In Gibbs free energy, author used 0-100℃ temperature but did not mentioned the reason for this temperature. Why we can’t use more than 100℃ temperature?

 

5. The author has claimed that this technique is new, but we can recover 99.5% of nickel with sulfuric acid leaching from spent Ni/Al₂O₃, while in this paper, the author has recovered only 73.2% nickel Why is this method better than the previous one?

Comments for author File: Comments.docx

Author Response

See attached file 'Reply sustainability-3236333-Reviewer 1'.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

Journal: Sustainability – MDPI

Type: Article

Title: Recovery of magnetic Ni particles from spent catalyst leachate by direct cementation

Authors: Farhad Moosakazemi, Ali Entezari-Zarandi, Sina Ghassa and Faïçal Larachi

 

The work proposes the recovery of Ni as pure metal from a spent methane reforming catalyst by an electrochemical cementation process, using metallic ground aluminum from scraps as sacrificial compound. The process is an interesting way of valorizing residues containing valuable metals, which otherwise should be disposed of and mined for production. Hence, it is an excellent example of circular economy. I recommend publication of the work after assessing the following minor comments.

1) Aluminum is known to have passivation, which hinders its spontaneous dissolution in acidic media to produce hydrogen. Hence while using it from scrap as ground aluminum, is there any pretreatment required to initiate the reaction of Al oxidation to form metallic Ni? Is there any particular composition of the PLS that should be fulfilled?

2) The ANOVA indicates strong linear relation with all the variables with an optimum at the largest Al/Ni, pH and time. Although, I understand that economic reasons would indicate preference of reducing the Al/Ni ratio, would it be interesting to extend the range explored, so as to find the optimum within? It is also possible to look for a conditional optimum, by doing a multi-objective optimization if the costs are included as another dependent variable.

Author Response

See attached file 'Reply sustainability-3236333-Reviewer 2'.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

In this study, Farhad Moosakazemi reported using direct cementation to recover Ni from spent catalyst leachate, which can overcome the complexity of a traditional two-step process. In addition, several variables, such as pH, temperature, and process time have been optimized to achieve maximum Ni recovery and ensure the quality of the cemented Ni. Overall, the experiments are well designed, and the results are interesting that can be published after addressing the below concerns.

1.      In Fig. 1, G and H are not italicized in the figure picture but are represented in italicized format in the figure caption. Please maintain consistency throughout the whole paper.

2.       In Fig. 2, three pecks belong to Ni. Please mark the corresponding forms in this figure and explain these results briefly, making it easier for readers to understand.

3.       In Fig. 3, the quality of the right picture is not high, and some essential information cannot be received clearly. In addition, the format of this picture is not consistent with others shown in this manuscript.

4.       In Fig. 4, the first letter of every word was capitalized. However, only the first letter of the word is capitalized in Fig.5. The same situation also happened in Tables 1, 2, and 3.

 

5.       As the reviewer understands, the recovered Ni should be solid. How does the author use ICP-OES to evaluate nickel content?

Comments on the Quality of English Language

The English Language is fine.

Author Response

See attached file 'Reply sustainability-3236333-Reviewer 3'.

Author Response File: Author Response.docx

Reviewer 4 Report

Comments and Suggestions for Authors 1. Line 137 says “aluminum pulp concentrations ranging from 5 to 15 g/L” but in the table 1 - ranging from 3 to 15. Where are the correct concentrations? 2. The calculations carried out in point 3 are meaningless and cannot be used to predict the reaction in the system, since they do not take into account the kinetics of heterogeneous reactions. The reaction of dissolving aluminum in HCl is the most thermodynamically preferable in the system (fig. 1). It is not clear why it is necessary to study the change in Gibbs free energy as a function of temperature for the reaction between aluminum powder and nickel ions? 3. A more detailed explanation should be given of how the polynomial equation (5) was developed. 4. The recovery of Ni particles is highly dependent on the pH of the solution. Why are solutions with pH 4 or higher not considered? 5. Was all the aluminum really dissolved and pure nickel obtained? This needs to be clarified.

Author Response

See attached file 'Reply sustainability-3236333-Reviewer 4'.

Author Response File: Author Response.docx