Sustainable Production and Physicochemical Characteristics of Calcium Sulfate Dihydrate Prepared from Waste Eggshells
, Chaowared Seangarun 2, Banjong Boonchom 2,3,4,*, Nongnuch Laohavisuti 5,*, Wimonmat Boonmee 6, Pesak Rungrojchaipon 4 and Phairat Phimsirikul 1
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsSustainable production and physicochemical characteristics of calcium sulfate dihydrate prepared from waste eggshells have been reviewed and the following observations were made:
1. What is the significance of these kinds of studies?
2. The Intensity scale is missing in XRD (Refer to Figure 6).
3. % Transmittance scale is missing in FTIR (Please refer to Figure 2).
4. Authors are suggested to check the thermal stability of sulfate dehydrated prepared from eggshell waste by performing TGA analysis.
5. What will be the applications of sulfate dehydrated prepared from eggshell waste?
6. It is advised to perform TEM and BET analysis.
7. More characterization can be performed such as AFM, ssNMR, etc.
8. The abstract and conclusion should be improved.
9. Kindly remove the typographical errors present in the manuscript.
10. Please cite more relevant research papers dated 2022-2024.
Comments on the Quality of English Language
Moderate editing of English language is required.
Author Response
Reply to Reviewer 1st
Comments and Suggestions for Authors
Sustainable production and physicochemical characteristics of calcium sulfate dihydrate prepared from waste eggshells have been reviewed and the following observations were made:
- What is the significance of these kinds of studies?
Answer: The synthesis of value-added compounds from renewable natural resources is the driving force for environmental sustainability. The significance of this work is to use these bio-waste eggshells as raw materials (a Ca2+ source) to prepare valuable products (CaSO4·2H2O) for environmental sustainability, which can be used as soil amendments and fertilizers.
- The Intensity scale is missing in XRD (Refer to Figure 6).
Answer: The intensity scale is Intensity (a.u.) ; (arbitrary unit) that correct unit.
- % Transmittance scale is missing in FTIR (Please refer to Figure 2).
Answer: % Transmittance scale is Transmittance (a.u.) ; (arbitrary unit) that correct unit.
- Authors are suggested to check the thermal stability of sulfate dehydrated prepared from eggshell waste by performing TGA analysis.
Answer: The TGA instrument of our Institute is worn out and uses a long-time process for repairing.
- What will be the applications of sulfate dehydrated prepared from eggshell waste?
Answer: The calcium sulfate products obtained from this work will be used for soil amendment and fertilizer
- It is advised to perform TEM and BET analysis.
Answer: Thank you for the good suggestion but we cannot perform TEM and BET analysis due to have not these instruments in our faculty.
- More characterization can be performed such as AFM, ssNMR, etc.
Answer: Thank you for the good suggestion but we cannot perform AFM and NMR analysis due to have not these instruments in our faculty. In our opinion, it is confident that the reporting results of the investigation of the physical and chemical properties of calcium sulfate compounds prepared by this process are sufficient.
- The abstract and conclusion should be improved.
Answer: the abstract and conclusion were rewritten.
- Kindly remove the typographical errors present in the manuscript.
Answer: the revised manuscript was rechecked to correctly.
- Please cite more relevant research papers dated 2022-2024.
Answer: the Refs. dated 2022-2024 were added in the revised manuscript.
Reviewer 2 Report
Comments and Suggestions for Authors1. Would you kindly consider revising the abstract?
2. In the introduction section, the author should briefly compare 4 to 5 recent reports on the preparation and properties of calcium sulfate dihydrate.
3. The author should include references to previous reports in the experimental section.
4. The reason why CuO is not present in hen eggshells should be added in the elemental composition analysis section.
5. The author should add a reference for the production yields formula.
6. The author should compare the reaction times (s) and production yields (%) with those in previous reports.
7. The author should add references for each absorption position in Tables 3 and 4.
Author Response
Reviewer 2nd
Comments and Suggestions for Authors
- Would you kindly consider revising the abstract?
Answer: the abstract was rewritten.
- In the introduction section, the author should briefly compare 4 to 5 recent reports on the preparation and properties of calcium sulfate dihydrate.
Answer: Gypsum are obtained from two sources; natural and synthetic gypsums. Synthetic gypsum is produced as a waste product or by-product in a range of industrial processes. Recently, some researchs reposted on the synthesis of gypsum from reaction between bassanite, eggshells, and Pila globosa shells with sulfuric acid by diference of process and condition of acid concetration and time consuption [23-24, 26-29].
- The author should include references to previous reports in the experimental section.
Answer: Eq. (1) demonstrated the chemical reaction between H2SO4 solution and eggshell CaCO3 powder, which is the same reaction with previous researches [23,24, 26-29] but process and condition of acid concentration and time consumption are different.
- The reason why CuO is not present in hen eggshells should be added in the elemental composition analysis section.
Answer: The CuO is not present in hen eggshells, but is present in duck eggshells, which may be due to different diets and minerals used in animal husbandry.
- The author should add a reference for the production yields formula.
Answer: As shown in Eqs. (1) and (2), the production yields (Yp/%) of CaSO4·nH2O products prepared from eggshell CaCO3 raw materials were computed by using Eq. (3) [29]:
x 100% (3)
where wtocs and wttcs (g) are the weights of the CaSO4·nH2O from observation and theoretical, respectively.
- The author should compare the reaction times (s) and production yields (%) with those in previous reports.
Answer: The production yields reported in this work are higher than that reported in previous work (<80%) [29].
The reaction time of the gypsum products synthesized from two kinds of eggshell wastes in this work are shorter than those of reported in previous researches (24 h) [23,24].
- The author should add references for each absorption position in Tables 3 and 4.
Answer: The authors disagree with adding references for each adsorption site in Tables 3 and 4, as only references [23 and 24] are included in the text.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe goal of this work was to use these bio-waste eggshells as raw materials for the preparation of valuable products (CaSO4·2H2O) for environmental sustainability. The experimental results confirmed that hen and duck eggshell wastes are the potential secondary materials for applying as the Ca source in order to prepare the value-added material. The experimental diffraction patterns confirmed that the value-added products from the eggshell waste powders are CaSO4·2H2O (gypsum). When gypsum is thermally treated, it can completely dehydrate to form anhydrite, (β polymorph). The diffraction patterns also indicated that the sample phase will change from a monoclinic (gypsum) to an orthorhombic (anhydrite) crystal structure. The morphological characteristic of CaCO3 shows the irregular shape with different agglomeration particle sizes, whereas plate-like particles were observed for gypsum. The crystallite sizes calculated from the diffraction peak with the highest intensity of CaCO3, CaO, CaSO4·2H2O, and CaSO4 are presented, respectively.
This is valuable work. It should be published after minor revisions as below.
General Remarks
1. The purpose of this work is to use these bio-waste eggshells as raw materials (a Ca2+ source) for the preparation of valuable products.
In Table 2. is mentioned that production yield of CaSO4·nH2O derived from hen or duck eggshell powders was estimated to be 84.7%. In my opinion real production yields (Yp/%) of Ca products prepared from eggshell are ~100%.
The value defined in eq. 3 is not process yield but only proportion of used substrate amounts. This should be corrected and clarified.
2. Conclusions, last sentence. “…Sustainability, easy, low-cost, economic, and environmental techniques were obtained in this work for the preparation of CaSO4·2H2O compound”…. There’s nod data in the work evaluated these values. I propose to remove it.
Author Response
Reviewer 3rd
Comments and Suggestions for Authors
The goal of this work was to use these bio-waste eggshells as raw materials for the preparation of valuable products (CaSO4·2H2O) for environmental sustainability. The experimental results confirmed that hen and duck eggshell wastes are the potential secondary materials for applying as the Ca source in order to prepare the value-added material. The experimental diffraction patterns confirmed that the value-added products from the eggshell waste powders are CaSO4·2H2O (gypsum). When gypsum is thermally treated, it can completely dehydrate to form anhydrite, (β polymorph). The diffraction patterns also indicated that the sample phase will change from a monoclinic (gypsum) to an orthorhombic (anhydrite) crystal structure. The morphological characteristic of CaCO3 shows the irregular shape with different agglomeration particle sizes, whereas plate-like particles were observed for gypsum. The crystallite sizes calculated from the diffraction peak with the highest intensity of CaCO3, CaO, CaSO4·2H2O, and CaSO4 are presented, respectively.
This is valuable work. It should be published after minor revisions as below.
General Remarks
- The purpose of this work is to use these bio-waste eggshells as raw materials (a Ca2+ source) for the preparation of valuable products.
Answer: Therefore, this work aims to use these bio-waste eggshells as raw materials (a Ca2+ source) for the preparation of valuable products (CaSO4·2H2O) for environmental sustainability which can be used as soil amendments and fertilizers.
In Table 2. is mentioned that production yield of CaSO4·nH2O derived from hen or duck eggshell powders was estimated to be 84.7%. In my opinion real production yields (Yp/%) of Ca products prepared from eggshell are ~100%.
The value defined in eq. 3 is not process yield but only proportion of used substrate amounts. This should be corrected and clarified.
Answer: Thank you for a good suggestion. The eq. 3 was edited following as:
Y_P=〖wt〗_ocs/〖wt〗_tcs x 100% (3)
where wtocs and wttcs (g) are the weights of the CaSO4·nH2O from observation and theoretical, respectively. The data in Table 2 is correct.
- Conclusions, last sentence. “…Sustainability, easy, low-cost, economic, and environmental techniques were obtained in this work for the preparation of CaSO4·2H2O compound”…. There’s nod data in the work evaluated these values. I propose to remove it.
Answer: the authors agree with this comment.
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors have responded positively and significantly enhanced the manuscript as suggested. I believe the study is now suitable for publication.
