Review Reports - Electrochemical Characterization of Biodiesel from Sunflower Oil Produced by Homogeneous Catalysis and Ultrasound

Round 1

Reviewer 1 Report

The abstract should be more specific and result oriented

2. Sunflower oil is already used as biofuel. What is the novelty of the present work

3. There is no mechanism stabilised for a given process; it is based on random experiments that explain the mechanism in the methodology

4. Explain HPLC with a diagram

5. where is UV results

6. why not authors compare results with the current work? Please compare and provide comparative results

7. Why choose 304 stainless Steel

8. conclusion is not clear.

9. some references are not related to the current topic I suggest some articles, read and cite

https://doi.org/10.1007/s12155-021-10353-6

https://doi.org/10.1016/j.matpr.2021.08.248

Author Response

Response to Reviewer 1 Comments

1.- The abstract should be more specific and result oriented

Thanks for the suggestions, The abstract is restructured. The changes have been made see lines 23-36

Sunflower oil is already used as biofuel. What is the novelty of the present work

Thanks for the suggestions.

The novelty consists of applying the electrochemical techniques of open circuit potential, linear scanning voltammetry and electrochemical impedance spectroscopy to characterize biodiesel (lines 109-115), together, these measurements could be used as an alternative method of evaluation (lines 239-308). Additionally, the transesterification reaction was carried out with a conversion to biodiesel of 99.79% (this data was not found in the literature using ultrasound as an energy source) at a transesterification temperature of 50 °C for 60 minutes with a methanol/oil molar ratio of 6:1 (lines 225-226) which could be considered as a contribution.

There is no mechanism stabilised for a given process; it is based on random experiments that explain the mechanism in the methodology

Thanks for the suggestions. We have carefully reviewed the methodology and added recommended bibliographic citations and appended below are the general paragraphs describing the methodology for the Electrochemical characterization of Biodiesel from Sunflower oil produced by homogeneous catalysis and Ultrasound.

The methodology employed was as follows: in section 2.1 concerning materials and reagents, the composition of the vegetable oil is presented as well as the description of the reagents used (lines 117-123) [42], In section 2. 2 concerning biodiesel production the amounts of potassium hydroxide, methyl alcohol and sunflower oil for biodiesel production are presented [37], mentioning the operation data of the ultrasonic device used as energy source for the transesterification reaction including exposure times and temperature of each sample, The obtained biodiesel is centrifuged and rinsed (lines 124-147) , in section 2.3 the acid number, viscosity and density of the biodiesel were determined following the International Organization for Standardization (ISO) standards 660, 3104 and 3675 [43] and the results were compared under the American Society for Testing and Materials (ASTM) international standard; The acid number was determined by titration. The percentage conversion of abiodiesel triglycerides was determined by reversed-phase high performance liquid chromatography (HPLC) with an ultraviolet (UV) detector (lines 148-168). The data were then statistically processed in Excel using Microsoft 365 software, obtaining the arithmetic mean and standard deviation.

For the electrochemical tests in section 2.4, samples obtained at 50 °C were selected to evaluate the stability [44,45]. Using open circuit potential, linear sweep voltammetry and electrochemical impedance spectroscopy. A commercial fossil diesel (PEMEX brand) obtained from a gas station in Querétaro, Mexico was used as a reference and comparison point. All samples were stabilized at room temperature for 45 minutes prior to measurement. No additional preparation procedure was used; all experiments were performed at room temperature in a glass electrochemical cell configured with two electrodes and a capacity of 12 mL with a compartment constant of 0.012 cm-1. The electrodes used were constructed of 304 stainless steel sheets. The experiments were performed with a potentiostat-galvanostat and the electrochemical techniques are described in section 2.4.1 (Lines 169-196) [33].

Explain HPLC with a diagram

Thanks for the suggestions (see supplementary material)

Where is UV results

Thank you for your comments, the changes have been made

The HPLC used in all the biodiesel samples has a UV-visible light detector (190-700 nm) in line with up to five simultaneous wavelengths and where what we are looking for with this analysis is to verify that the triglycerides have really been converted into biodiesel.

The chromatograms corresponding to the different tests carried out to verify the conversion of vegetable oil into biodiesel by the transesterification process are attached in complementary information, which is confirmed by the results obtained in the different tests carried out with the HPLC (See complementary information).

Why not authors compare results with the current work? Please compare and provide comparative results

Thank you for your comments, the changes have been made. in addition to the comparisons already included in the results section, comparisons with current work are attached.

See lines 218-221

Although the percentage of biodiesel indicated by the red line varies, it is always within acceptable parameters according to ES 14214. The highest biodiesel quality obtained by weight was 93.4 wt.% which represents 6.6 wt.% glycerol which is slightly lower than the data reported by Chilakamarry et.al [17].

See lines 222-226

The concentration of methyl ester (conversion to biodiesel) and the relative amount of methyl ester concerning oil in biodiesel (yield) during homogeneous transesterification of sunflower oil catalyzed with KOH at 65 °C by Gemma Vicente was 99.76 ± 0.05, and 91.67 ± 0.27, respectively [37,47]. These results are similar to ultrasound results at 50 °C, with a 99.79 % conversion and 93.40 % yield, as shown in Table 2

See Lines 233 to 238

Homogeneous catalysis studies have been carried out recently [37], using different raw materials. Such is the case of Andreo et al [1] who used pigfat and methyl alcohol (MeOH) as solvent obtaining a conversion to biodiesel of 99%, on the other hand Juliana et al [49] obtained a conversion of 98.9% using ethyl alcohol (EtOH) and leather tranning waste as raw material; these results are slightly lower than those obtained in this study using ultrasound.

Why choose 304 stainless Steel

Thank you for your comments, the changes have been made

Answer: 304 stainless steel was selected because no electrochemical reactions are expected in these kind of systems, besides, it is easy to obtain and manipulate, and contribute to have a non-expensive system. In order to clarify the selection of the material, we have add a sentence in 2.4 section. See lines 177-178.

The title was modified see lines 4-5.

Electrochemical characterization of Biodiesel from Sunflower oil produced by homogeneous catalysis and Ultrasound

Conclusion is not clear.

Thanks for the suggestions, improvements were made to the conclusions. See lines 309-323

Some references are not related to the current topic I suggest some articles, read and cite

https://doi.org/10.1007/s12155-021-10353-6

https://doi.org/10.1016/j.matpr.2021.08.248

Thanks for the suggestions, the recommended articles are read and related.

See Lines 40-41

Energy has always been the key driving force facilitating human and societal development; fossil fuels have been humanity's primary energy source in recent decades [1,2]

See lines 43-45

As alternatives to gasoline and diesel, biodiesel and bioethanol are attracting increasing attention due to their advantages as renewable ecological energy sources [11-17].

See lines 218-221

Author Response File: Author Response.pdf

Reviewer 2 Report

title of paper is interesting but lack of presenting the resemblance of topic with the text provides.

author should revise whole manuscripit the results provided are not sufficient to the worth of the journal.

overall manuscript need revision in the form of results.

results are too generic need more parameters to be discussed

author should provide novelty there are many researcher work in this field

Comments for author File: Comments.docx

Author Response

Title of paper is interesting but lack of presenting the resemblance of topic with the text provides

Thank you very much for the suggestion, the title has been modified

see lines 4-5

Electrochemical characterization of Biodiesel from Sunflower oil produced by homogeneous catalysis and Ultrasound

Author should revise whole manuscripit the results provided are not sufficient to the worth of the journal.

Thank you very much for the suggestion, improvements have been made: Comparisons with other articles in addition to those already existing in the results section are attached with current works as suggested by the referee

See lines 218-221

See lines 222-226

See Lines 233 to 238

3.-Overall manuscript need revision in the form of results

Thank you for your comment, the changes have been made, it is restructured:

Title see lines 4-5
Abstract see lines 23-36
New references are added: Chilakamarry et.al [2 and 17] (see lines 41,45,221) Salaheldeen al. [37] (see lines 88,127,224,225,229, and 234), Andreo et.al [1] (lines 41) and Yuliana et.al [49] (see line 236)
The conclusions are modified see lines 309-323

4.-Results are too generic need more parameters to be discussed

Thank you for your comment, the changes have been made.

The comparisons for response two are appended in addition to those already contained in the results section of the manuscript section 3.1 see lines 199-238 corresponding to the characterization and production of biodiesel from sunflower oil and assisted by ultrasound. The proposed electrochemical characterization of biodiesel is described in section 3.2.1 Open circuit potential (lines 240-262), 3.2.2 Linear sweep voltammetry (lines 264-278) and 3.2.3 Electrochemical impedance spectroscopy (lines 279-308). There is very little information on the above electrochemical techniques applied to characterize biodiesel.

5.-Author should provide novelty there are many researcher work in this field

Thank you for your comment, the changes have been made.

The novelty consists of applying the electrochemical techniques of open circuit potential, linear scanning voltammetry and electrochemical impedance spectroscopy to characterize biodiesel (lines 109-115), together, these measurements could be used as an alternative method of evaluation (lines 239-308).
Additionally, the transesterification reaction was carried out with a conversion to biodiesel of 99.79% (this data was not found in the literature using ultrasound as an energy source) at a transesterification temperature of 50 °C for 60 minutes with a methanol/oil molar ratio of 6:1 (lines 225-226) which could be considered as a contribution.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The introduction was sufficiently edited with the background with relevant references, methodology and conclusion. The quality of the manuscript is improved.