One-Step Biodiesel Production from Waste Cooking Oil Using CaO Promoted Activated Carbon Catalyst from Prunus persica Seeds
Round 1
Reviewer 1 Report
In this work, Hameed et al. have investigated the conversion of waste cooking oil into biodiesel using a novel catalyst derived from peach shell and eggshell. The catalyst demonstrates high activity towards converting triglyceride into fatty acid methyl ester. This work is of interest to the audience of Catalysts. There are several minor concerns, though, that need to be addressed before acceptance.
Line 113-114: Rephrase the sentence “Waste chicken eggshells were collected from the NUST Islamabad student cafeteria and waste cooking oil (WCO).”
Line 198: “methanol oil to oil molar ratio” -> “methanol to oil molar ratio”. Both “methanol to oil” and “oil to methanol” terms are used in the manuscript. For instance, Line 24 reads “oil to methanol ratio 1:8”, while Line 407 reads “methanol to oil molar ratio 8:1”. Please keep this consistent.
Line 252: For the sake of completeness, the methods and materials used to determine the basic strength should be provided in the Materials and Methods section.
Line 423: How the error bar is determined in Figure 8? Why there are no error bars in Figure 7?
Line 433: The method part of session 3.4 Biodiesel Characterization should be moved to Materials and Methods section, following 2.5 Catalyst Characterization.
Line 455: Figure 12 caption, “Comp Name: Hexadecenoic acid” should be “Hexadecanoic acid”. Similarly, compound names in Table 4 also need to be fixed.
Line 499: 5 wt -> 5 wt%
Author Response
Comments # 1 In this work, Hameed et al. have investigated the conversion of waste cooking oil into biodiesel using a novel catalyst derived from peach shell and eggshell. The catalyst demonstrates high activity towards converting triglyceride into fatty acid methyl ester. This work is of interest to the audience of Catalysts. There are several minor concerns, though, that need to be addressed before acceptance.
Response: Thanks for your time and effort in reviewing this manuscript. All comments have been addressed.
Comments # 2 Line 113-114: Rephrase the sentence “Waste chicken eggshells were collected from the NUST Islamabad student cafeteria and waste cooking oil (WCO).”
Response: Waste chicken eggshells and waste cooking oil were collected from the student cafeteria of NUST H-12 Islamabad campus.
Comments # 3 Line 198: “methanol oil to oil molar ratio” -> “methanol to oil molar ratio”. Both “methanol to oil” and “oil to methanol” terms are used in the manuscript. For instance, Line 24 reads “oil to methanol ratio 1:8”, while Line 407 reads “methanol to oil molar ratio 8:1”. Please keep this consistent.
Response: Oil to methanol molar ratio 1:8 corrected in the whole manuscript
Comments # 4 Line 252: For the sake of completeness, the methods and materials used to determine the basic strength should be provided in the Materials and Methods section.
Response: Hammett indicator method was used to assess the strength of the base. Anhydrous methanol solution (0.02 M) titration with Hammett indicator-benzene carboxylic acid was used to determine the catalysts' overall basicity.
Comments # 5 Line 423: How the error bar is determined in Figure 8? Why there are no error bars in Figure 7?
Response: Error bar is determined using the standard deviation method. Error bars have been added to Fig 7 as well.
Comments # 6 Line 433: The method part of session 3.4 Biodiesel Characterization should be moved to the Materials and Methods section, following 2.5 Catalyst Characterization.
Response: 2.6 Biodiesel Characterization is added in the materials and method section
Comments # 7 Line 455: Figure 12 caption, “Comp Name: Hexadecenoic acid” should be “Hexadecanoic acid”. Similarly, compound names in Table 4 also need to be fixed.
Response: Hexadecanoic acid corrected in fig 12 and table 4
Comments # 8 Line 499: 5 wt -> 5 wt%
Response: 5 wt% corrected
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Please make careful corrections for the following:
Line 17: solid-based catalyst? I think it typo and will be solid base catalyst.
Line 88: The term “Agriculture’ repeated twice that should be corrected.
Line 97: More transesterification doesn’t reflect another transesterification reaction. Please rearrange the sentence.
The paragraph started from line 88 doesn’t relate with the final paragraph of the introduction. Why suddenly moved to peach biochar from eggshell. I would replace paragraph started with line 73 with the paragraph of line 88 for a smooth transition.
Line 113 & 114: Waste chicken eggshells were collected from the NUST Islama-bad student cafeteria and waste cooking oil (WCO)???—please make correction.
Line 128: in an N2 environment-correction required.
Line 134: neutral pH of filtrate? If yes please specify.
Question:
Regarding water wash: why DI water used for prunus shell washing but purified water used for eggshell washing?
Sieve size: why 0.250 mm sieve (line 126) size for egg shell and 0.071 mm for prunus? Why can not use same sieve to keep the process simple?
Line 155: wt% with respect to what? Author mentioned according to the standard method without providing reference.
Line 168: oC correction needed.
Line 170 to 172: Repeated use of Fourier infrared spectrometer (FTIR) in one sentence.
Line 195: Authors mentioned reaction at atmospheric pressure! This can not happen when closed reaction flask was used.
Line 198: 8: 1 methanol oil to oil molar ratio? Type I believe.
Line 201: How top layer separated with rotavap? Good to say, excess methanol was removed.
Line 208: Sentence correction required. It can not be initial successive run!
Line 309: biodiesel yield of several catalysts? Manuscript discusses one catalyst in fig 6.
Questions regarding reproducibility: No standard deviation or error bar for figure 7 results, that indicate every reaction was performed only one time. But for figure 8, there is error bar with visibly same value. Need proper explanation.
Biodiesel yield calculation: used equation 1. If you have unconverted triglyceride that is also dissolved with biodiesel mixture, then you have calculated different yield from different reaction using this formula?
In the materials section, author indicated KOH used to boost the catalytic efficiency. During water wash of the biodiesel, KOH should wash away. So after regeneration of the catalyst, have you used without KOH activation? Nothing found in the materials section.
Author Response
Comment # 1 Please make careful corrections for the following:
Response: All comments are addressed as per instructed.
Comment # 2 Line 17: solid-based catalyst? I think it typo and will be solid base catalyst.
Response: Thanks for the comment, and it has been corrected.
Comment # 3 Line 88: The term “Agriculture’ repeated twice that should be corrected.
Response: Thanks for the comment, and it has been corrected.
Comment # 4 Line 97: More transesterification doesn’t reflect another transesterification reaction. Please rearrange the sentence.
Response: CaO is an inexpensive, environmentally safe, non-corrosive, eco-friendly, highly active substance under mild conditions that can be regenerated for another transesterification process.
Comment # 5 The paragraph started from line 88 doesn’t relate with the final paragraph of the introduction. Why suddenly moved to peach biochar from eggshell. I would replace the paragraph started with line 73 with the paragraph of line 88 for a smooth transition.
Response: Correction made accordingly
Comment # 6 Line 113 & 114: Waste chicken eggshells were collected from the NUST Islama-bad student cafeteria and waste cooking oil (WCO)???—please make correction.
Response: Waste chicken eggshells and waste cooking oil were collected from the student cafeteria of NUST H-12 Islamabad campus.
Comment # 7 Line 128: in an N2 environment-correction required.
Response: Thanks for the comment, and it has been corrected.
Comment # 8 Line 134: neutral pH of filtrate? If yes please specify.
Response: The neutral pH of the filtrate is attained and updated in the manuscript.
Comment # 9 Regarding water wash: why DI water used for prunus shell washing but purified water used for eggshell washing?
Response: DI water is used throughout the process, and purified water refers to DI water. Term purified is also changed in the manuscript.
Comment # 10 Sieve size: why 0.250 mm sieve (line 126) size for egg shell and 0.071 mm for prunus? Why can not use same sieve to keep the process simple?
Response: Thanks for indicating the mistake. The same sieve of 0.250mm is used throughout the process.
Comment # 11 Line 155: wt% with respect to what? Author mentioned according to the standard method without providing reference.
Response: wt% of CaO with respect to activated carbon is already mentioned in the manuscript. Reference is also provided along with that.
Comment # 12 Line 168: oC correction needed.
Response: Comment addressed
Comment # 13 Line 170 to 172: Repeated use of Fourier infrared spectrometer (FTIR) in one sentence.
Response: Comment addressed
Comment # 14 Line 195: Authors mentioned reaction at atmospheric pressure! This can not happen when closed reaction flask was used.
Response: Atmospheric pressure was maintained by attaching the flask with a condenser.
Comment # 15 Line 198: 8: 1 methanol oil to oil molar ratio? Type I believe.
Response: oil to methanol molar ratio 1:8
Comment # 16 Line 201: How top layer separated with rotavap? Good to say, excess methanol was removed.
Response: Top layer referring to excess methanol correction is done as recommended.
Comment # 17 Line 208: Sentence correction required. It can not be initial successive run!
Response: Corrected as “After the transesterification reaction”
Comment # 18 Line 309: biodiesel yield of several catalysts? Manuscript discusses one catalyst in fig 6.
Response: Fig 6 discuss several catalysts with different calcium loadings and calcination temperature.
Comment # 19 Questions regarding reproducibility: No standard deviation or error bar for figure 7 results, that indicate every reaction was performed only one time. But for figure 8, there is error bar with visibly same value. Need proper explanation.
Response: Correction is made in both figures, and error bars are updated.
Comment # 20 Biodiesel yield calculation: used equation 1. If you have unconverted triglyceride that is also dissolved with biodiesel mixture, then you have calculated different yield from different reaction using this formula?
Response: Biodiesel yield is calculated using equation 1, and 96% yield was obtained. No unconverted triglycerides were found in the process.
Comment # 21 In the materials section, author indicated KOH used to boost the catalytic efficiency. During water wash of the biodiesel, KOH should wash away. So after regeneration of the catalyst, have you used without KOH activation? Nothing found in the materials section.
Response: KOH was used for the activation of biochar to obtain activated carbon. Afterward, activated carbon was loaded with CaO. For the sake of regeneration, KOH is not required becasue biochar is already activated, and just tetrahydrofuran is utilized in the regeneration process.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Line 461-462: "Because of the increased degree of unsaturation in FAME constituents, biodiesel has strong combustible properties and high-power output". Please provide reference for this statement or explain how an increase in unsaturation improves those properties.
Author Response
“Detailed Response to Reviewer’s_2”
Ms. Ref. No.: catalysts-1718607
Title: One-step biodiesel production from waste cooking oil using CaO promoted activated carbon catalyst from prunus persica seeds
The authors are grateful for the time and efforts taken by the editors and referees in reviewing the manuscript and giving constructive comments.
Reviewer #2:
Comment # 1 Line 461-462: "Because of the increased degree of unsaturation in FAME constituents, biodiesel has strong combustible properties and high-power output". Please provide reference for this statement or explain how an increase in unsaturation improves those properties.
Response: All comments are addressed as per instructed. Unsaturation degree influences the burning rate, energy density, and power output of biodiesel. This statement is also justified by Ibadurrohman et al., 2021. References are cited in the manuscript
- Ibadurrohman, I.A., Hamidi, N. and Yuliati, L., 2022. The role of the unsaturation degree on the droplet combustion characteristics of fatty acid methyl ester. Alexandria Engineering Journal, 61(3), pp.2046-2060.
- Roy, T., Ágarwal, A.K. and Sharma, Y.C., 2021. A cleaner route of biodiesel production from waste frying oil using novel potassium tin oxide catalyst: A smart liquid-waste management. Waste Management, 135, pp.243-255.
Author Response File: Author Response.pdf
