The Structural Evolution of Recrystallized Asymmetric SiC Membranes for High-Performance Oily Wastewater Treatment

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript presents a well-structured study on the fabrication, characterization, and performance of asymmetric SiC membranes for oily wastewater treatment. The work is relevant to the field of ceramic membrane technology and oily wastewater treatment. However, several issues regarding novelty, data interpretation, experimental design, and mechanistic discussion should be addressed before the manuscript can be considered for publication:

1.The Introduction should include a more critical comparison with recent literature and clearly identify the scientific gap addressed by the present work.

2.The manuscript compares the fabricated asymmetric membranes with literature data for symmetric membranes. However, the compared membranes differ in: fabrication route, pore size, thickness, support structure, testing conditions. Therefore, the extracted parameters (k₁, k₂, and k₃) may not solely reflect the influence of membrane architecture. The authors should discuss the limitations of this comparison and justify the validity of comparing data obtained from different studies.

3.All filtration experiments were performed in dead-end mode. Industrial oily wastewater treatment is commonly conducted under crossflow conditions to minimize fouling. The authors should discuss how the obtained permeability, rejection, and fouling results may differ under crossflow operation and clarify the practical implications of their findings.

4.Hermia models were used to identify the dominant fouling mechanism. However: the R² values for cake filtration (0.9805) and intermediate blocking (0.9798) models are almost identical and the conclusion that cake filtration dominates should therefore be treated with caution. So, additional fouling characterization (SEM images of fouled membranes, pore analysis after filtration, etc.) would strengthen the conclusions.

5.The membrane was evaluated for only four filtration cycles. For practical applications, longer-term stability tests are necessary. The authors should discuss membrane durability over extended operation and provide justification for concluding that the membrane is suitable for long-term reuse.

6.Thermal regeneration at 600 °C successfully restored membrane permeability. However, thermal treatment at such temperatures may involve significant energy consumption. The authors should discuss the energy requirements, and compared this method with conventional chemical cleaning methods.

7.The membrane thickness decreases from approximately 15 μm to 12 μm at 2000 °C. A quantitative analysis of the contribution of thickness reduction to permeability enhancement would be valuable.

8.The average droplet size is reported as 356.2 nm. Please provide: droplet size distribution curve and the stability of the emulsion during filtration.

9.Several figures contain small labels and text that may be difficult to read after publication. Please improve the resolution and font size of all figures, particularly Figures 5–10.

 

Comments on the Quality of English Language

The manuscript is generally clear and understandable. Nevertheless,  it still contains several grammatical inaccuracies and poorly constructed sentences. Therefore, careful English language editing is recommended.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This study applied asymmetric SiC membranes for oily wastewater treatment. Membranes were carefully characterized, separation performance was evaluated and compared with reported membranes, water transport mechanism was investigated by fitting experimental data with models. This study is well prepared. It addresses an important topic and shows potential value, but several minor concerns must be resolved prior publication.

(1) The title of y axis in Fig. 10 is confusing, physical meaning of the y value should be clearly stated in figure caption.

(2) The title of y axis in Fig 12 might be wrong, the data in the figure is not flux recovery. The image resolution of Fig 12 seems low, is it possible to make it look better?

(3) To ensure statistical robustness, the author should mention in the manuscript that how many experiments are repeated to obtain error bar.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have provided a detailed and careful response to all the comments raised during the first review round. The revisions made to the manuscript (particularly the introduction, discussion of Hermia fouling models, comparison between symmetric and asymmetric membranes, and justifications regarding operating conditions) have significantly improved the clarity and scientific rigor of the paper. The manuscript is now more robust and transparent.

Minor issues to address before publication:

1. Figure 1 (droplet size distribution):  This figure was added in the response to reviewers but is missing from the revised manuscript. Please include it in Section 2.3.
2. Incomplete references: In the cover letter (page 2), some references (e.g., [2]) have truncated titles. Please ensure all references are complete in the final manuscript.
3. Equation numbering inconsistency:  Please correct the numbering or the equation;

 

Comments on the Quality of English Language

The manuscript is generally clear and understandable. Nevertheless,  it still contains several grammatical inaccuracies and poorly constructed sentences. Therefore, careful English language editing is recommended.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf