Electrochemical Production of Hypochlorous Acid and Sodium Hydroxide Using Ion Exchange Membranes

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear authors;

 

This paper examines the electrolytic production of hypochlorous acid (HClO) and sodium hydroxide (NaOH) using a three-compartment laboratory set-up separated by ion-exchange membranes. The aim is to optimize operating conditions (electrical voltage, electrolysis time, sodium chloride concentration) by assessing their effect on active chlorine concentration, NaOH production, pH, electrical efficiency and energy consumption. Taguchi methodology is used for experimental planning and statistical analysis via ANOVA. The results show that electrical voltage is the most influential factor, with relatively high energy efficiency and optimum conditions achieved at 7 V, 90 minutes, and 30 g/L NaCl.

 

Overall, this work is interesting and well written. However, here are a few comments and questions to bear in mind:
- The use of a tripartite system with ion exchange membranes is appropriate to avoid mixing of anodic and cathodic products. However, the transposition to industrial or semi-industrial scale deserves to be discussed more widely, particularly in terms of membrane durability, costs and maintenance.

• Although the parameters chosen (voltage, time, concentration) are standard, the study would benefit from more rigorous justification of the ranges selected, based in particular on the technical literature on industrial chlor-alkali processes.
• The approach is methodologically rigorous. However, the interaction between factors (notably voltage × NaCl concentration) is not analyzed, which may mask important synergistic effects. A more robust method (e.g. full factorial design or RSM) could provide more refined information.
• The work does not sufficiently discuss the potential formation of harmful by-products such as chlorates (ClO₃-) or chlorites (ClO₂-). Given the environmental focus of the study, the lack of analysis of these contaminants is a critical shortcoming.
• Although the article briefly mentions the rapid degradation of HClO, no stability studies are presented, which limits the assessment of practical applicability (storage, transport, etc.).
• Energy consumption is presented in kWh/kgCl₂ or NaOH, but comparison with commercial or competing technologies is absent, limiting appreciation of overall system performance.

• What is the degradation profile of the HClO produced in this system? A kinetic study would be essential to assess its relevance in a real disinfection context.

   

• Have undesirable by-products (chlorates, chlorites) been formed? Their analysis would be crucial to validate the safety of electrolyzed water.

   

• What would be the effects of continuous (rather than batch) electrolysis? The switch to a continuous regime could alter chemical equilibria and energy consumption.

   

• What is the durability of membranes and electrodes after several cycles? A long-term aging or performance study would considerably enhance the study.

   

• Is the process economically competitive with existing disinfection and NaOH production technologies? A technico-economic assessment is expected in a sustainability study.

Author Response

Good morning.

I am writing to you as the author of the manuscript entitled.”
Electrolytic production of hypochlorous acid and sodium hydroxide: Effect of operating conditions in a   with ion exchange membranas”y.

I am grateful for the opportunity to submit our work for your consideration and in response to the valuable comments received, we submit the response to the observations made. We thank you for your comments and reiterate our commitment to the continuous improvement of our work.

Sincerely

Juan Medina Collana

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This study employed a lab-scale tri-compartmental electrolytes and the Taguchi method to explore how voltage, electrolysis duration and sodium chloride concentration affect electrolyzed water generation. The optimal conditions were found to be 7 V, 90 min electrolysis and 30 g/L NaCl, yielding high-performance electrolyzed water with notable available chlorine and NaOH concentrations. While the research offers a method and optimized conditions for making eco-friendly HClO disinfectant and is somewhat applicable in practice, it falls short in innovation, depth and real-world application alignment.

1. The first sentence of the abstract, "Hypochlorous acid (HClO), also known as electrolyzed water (EW)", is inaccurate as HClO isn't equivalent to electrolyzed water. On page 2, line 47, the statement "Electrolyzed water (EW) is widely accepted as an emerging disinfectant……" also misleadingly equates the electrolysis process with the disinfectant, which is not factual.
2. The abstract and introduction need more detailed elaboration on the advantages and design novelties of the experimental setup, along with comparative analysis with the latest research.
3. The chemical equation (6) Na⁺+2OH^-→NaOH(aq) is unbalanced.
4. The resolution of Figures 4, 5, 7 and 8 is too low to discern the axes, making it impossible to verify data rationality.
5. There is no comparison between this work and existing technological levels. It is recommended to include a comparative table.
6. Are there data on the electrolysis of seawater or other saline water? Experimental data on practical application scenarios should be added.

Author Response

Good morning.

I am writing to you as the author of the manuscript entitled.”
Electrolytic production of hypochlorous acid and sodium hydroxide: Effect of operating conditions in a   with ion exchange membranas”y.

I am grateful for the opportunity to submit our work for your consideration and in response to the valuable comments received, we submit the response to the observations made. We thank you for your comments and reiterate our commitment to the continuous improvement of our work.

Sincerely

Juan Medina Collana

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

In this study, a recently built laboratory-scale electrolyzed water generator with three compartments divided by cation and anion exchange membranes was used. The Taguchi methodology was used to examine the impact of process operating conditions on the resulting responses. The effect of electric potential levels (4.5, 6 and 7 V), electrolysis times (30, 60 16 and 90 min) and sodium chloride concentrations (5, 15 and 30 g/L) on physical and chemical characteristics (available chlorine concentration, sodium hydroxide and pH) and energy consumption were investigated. this research provides valuable information on the production of electrolyzed water, using an electrochemical system, which could have great potential for applications in the food industry, medicine and drinking water disinfection. Prior to acceptance, the authors are advised to address the following issues:

1. It is suggested that the author simplify the background narrative in the introduction section (such as a detailed explanation of the reaction mechanism) and focus on the research gaps directly related to this study. About 30% of the content in the current version (such as the detailed explanation of the reaction mechanism, the specific influence of factors such as PH on the reaction) can be appropriately deleted or moved to the supplementary material.
2. The vertical spacing before and after the secondary headings is different, specifically: 2. In Materials and Methods, the format of 2.1, 2.2 and 2.6 is different from other headings; At the same time, there are problems in the secondary and tertiary headings in 3. Results and Discussion. The secondary headings are similar to those in 2, while the tertiary headings not only have inconsistent paragraph spacing, but also have inconsistent font, such as 3.3.4.
3. Some images in this paper have insufficient resolution and proportional distortion, which is specifically manifested as obvious pixelation in Figs. 4, 5B, 7 and 8, and the aspect ratio of FIG. 8 is out of balance. It is suggested that the author make adjustments to improve the clarity of the picture.
4. The conclusion part is divided into 8 paragraphs at present, and there is a problem of content dispersion. It is suggested that the author integrate the conclusion part according to the principles of "integration of core findings and progressive strengthening of layers".
5. It is suggested that the authors review the full text to avoid details, such as :4. The "pH" in paragraph 4 of Conclusions is incorrectly written as "Ph".
6. The article uses a lot of space to describe the influence of pH, potential and electrolytic time on the production of HClO by electrolysis, but the conclusion part is finally implemented to " The production of HClO in situ and in real time makes this electrochemical method very advantageous to ensure disinfection in many industrial sectors.". It is suggested that the author find the research focus of the article and write the whole paper with this focus as the center.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

English can be improved to express research more clearly.

Author Response

Good morning.

I am writing to you as the author of the manuscript entitled.”
Electrolytic production of hypochlorous acid and sodium hydroxide: Effect of operating conditions in a   with ion exchange membranas”y.

I am grateful for the opportunity to submit our work for your consideration and in response to the valuable comments received, we submit the response to the observations made. We thank you for your comments and reiterate our commitment to the continuous improvement of our work.

Sincerely

Juan Medina Collana

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The content has been modified. The author mentioned Figure 9 in the answer, but should it correspond to Figure 8 in the text? More attention should be paid to details in the drawing, and the font of the coordinate axis numbers, names, etc. in the entire text should be consistent.

 

Author Response

Good morning, the manuscript has been modified according to your suggestion.
Best regards 

Juan Medina 

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Now, this manuscript can be accepted for publication.

Author Response

Good morning, the manuscript has been modified according to your suggestion.
Best regards 

Juan Medina 

Author Response File: Author Response.pdf