Efficient Removal of Heavy Metals from Aqueous Solutions Using a Bionanocomposite of Eggshell/Ag-Fe
, Oscar F. Olea-Mejía 2, María G. González-Pedroza 1 and Raúl A. Morales-Luckie 2,*Round 1
Reviewer 1 Report
Dear Authors,
this is an interesting work, which has great importance for the improvement the ecological situation, in particular the removal of heavy metals from the water. The advantage of this work is the application of cheap and affordable food waste material – eggshell. This method has great prospects.
Despite the undoubted merits of the work, the manuscript in its present form cannot be accepted for publication in Catalysts. The manuscript needs major revision.
My comments are in attached pdf-file. I duplicate my main comments here:
1) There is no uniform labeling of the samples through the text (for example, “composite”, “nanocomposite”, “EGGSHELL/Ag-Fe”)
2) Line 105: “A sieving process allowed to obtained particles of 149 µm”. How could you isolate by sieving the particles of only one size. Usually the fraction is isolated by sieving.
3) Line 108: “5 ml of AgNO3 and FeSO4 (10-2 M) for 1 h”. Define, that it is the water solution.
4) Line 109: “The mixture was exposed to microwave radiation”. Add information about the power.
5) Lines 109-110: Add phrase about evaporation of solvent.
6) Lines 115-116: “Surface area and pore size distribution was determined on a ISRI RIG-100 multitasking equipment, using the single point method”. How could you determine pore size distribution by single point method?
7) Lines 116-117: “which employs the static volumetric method; the volume adsorbed is calculated by the measured pressure of the test tube caused by changes in pressure”. It is general method, which used in low temperature nitrogen adsorption analyzers. You can just provide the reference to the paper, book or standard test method.
8) Line 142: “were in contact and stirring at 200rpm”. Add information about the temperature.
9) Lines 145-147: Most likely, this equation characterizes the adsorption capacity of the material, not the concentration of the remaining ions.
10) Line 148: “Ce (mg/L) represent the equilibrium analyte concentrations”. What does it mean?
11) Lines 150-151: Check the numeration of equations.
12) Line 167: “α (mg/g h) and β (g/mg) are the initial adsorption rate, and the activation energy”. The description of this parameter does not coincide with that in the given reference. The representation of activation energy in [g/mg] is an error!
13) Lines 172-174: The sentence is disordered. Probably you can divide it.
14) Line 184: Provide original reference for Langmuir model and equation.
15) Subsection 2.3.6 Sorption isotherms: Which program was used for the model fitting?
16) Line 199 and eq. 7: The variable “n” should be marked by other symbol, because "n" you already used.
17) Line 211: “It shows a pronounced hysteresis at higher P/Po”. The hysteresis at higher P/P0 is absent.
18) Line 212: “type II isotherm characteristic of porous media containing macropores and mesopores”. Firstly, there is type III isotherm, because the there is no convex section at the initial stage of the isotherm. Secondly, it cannot be stated about the meso- and macropores, because there is no pore size distribution.
19) Line 219: “surface area of 1.54 m2/g”. What is the accuracy of the surface areaa determination? How correct is it to give hundredths?
20) Line 220: “by the desorption method proposed by BJH it was found that the material has an average pore diameter of 24.15 nm”. Incorrect sentence. The average pore diameter is calculated by equation: d=4V/S.
21) Lines 221-223: Probably, it can also be due to the accuracy of the BJH method.
22) Figure 1: Provide uniform representation of the axis, as well as the same maximum value. Provide uniform representation of isotherm in the Fig. 1a (as in the Fig. 1b), with markers. Give the labelling of the samples in the title.
23) Line 233-234: “This result suggests that the presence of the NPs on the surface of the material may block partially the pores, lowering thus the pore size diameter”. In this case you can compare the pore size distributions of both samples.
24) Lines 239-240: “The elemental analysis performed by EDS”. description of this method is absent the "Materials and methods" section.
25) Line 243: What about EDS of nanocomposite?
26) Figure 2: It seems that the magnifications of images (a) and (b) are different.
27) Line 249: “in most cases excessive borohydride is needed to accelerate the reaction”.What reaction? The description of this method is absent in "Materials and methods" section.
28) Lines 260-261: “However, the immobilization of the nanoparticles in a solid matrix can increase the resistance to diffusion”. The sentence is not clear.
29) Line 273: Give the reference.
30) Figure 3, title: “X-ray diffraction spectra(!!!) of CaCO3 in eggshell (JCPDS-PDF 05-0586)”. Actually, it is an “X-ray diffractogram of the EGGSHELL”.
31) Line 307: “are 5.18, 6.18 and 5.73, the highest values correspond to As and Hg adsorption, which reach an equilibrium time faster than the other systems.”. Firstly, give units. Secondly, just bring into lines the rates and the metals
32) Line 309: “the value of the parameter α is higher than the β in all systems”. What does this mean? Please, explain.
33) Lines 312-313: “chemisorption can be considered as the dominant mechanism in both cases”. On the basis of which experimental data you made this conclusion. Please, explain.
34) Line 314: “at the concentration of 10 mg/L”. What about other concentrations?
35) Lines 314-315: “adsorption capacity was established by the isotherms below”. Not clear. Did you use different relative pressures, to state this?
36) Lines 317-318, title: What process?
37) Table 1: Experimental sorption data are absent.
38) Lines 335-336: “Based on this model, the adsorption capacity of EGGSHELL is greater for As than for Pb and Hg”. Isn't this the experimental data?
39) Lines 340-344: What is the physical meaning of the RL parameter? Give couple sentences.
40) Table 2: Give this table earlier, after its first mentioning.
41) Lines 365-393: Comparison can be shortened.
42) Line 369: “EGGSHELL has a low adsorption capacity compared to other materials, like eggshell”. is this the same?
43) Lines 384-385: “Other materials ... MIL-53(Fe) or MOF-808”. Give the references.
44) Line 406: “chemical adsorption process”. There is no evidence of this statement.
45) Line 409: “silver and iron nanoparticles”. In the other text it was bimetallic nanoparticles
46) Manuscript contains unclear and incorrect sentences. For example:
Line 21: “adsorption experimental data” (instead “experimental adsorption data”)
Line 29: “major concern”
Line 30-31: “lead, arsenic and mercury falls into this category”
Line 35: “may contain high as 0.5% Pb” (instead “may contain up to 0.5% Pb”)
Line 41: “atmospheric fall out”
Line 51: “CaCO3 (like calcite) occurs naturally” (instead “CaCO3 (like calcite) exists naturally”)
Line 53: “CaCO3–H2O, CaCO3–6H2O”
Line 73: “may improve” (instead “can be improved”)
Line 75: “The structure of these systems be:...”
Line 105: “allowed to obtained”
Line 151: “First propose by”
Line 156: “qt (mg/g) is the amount”
Line 177: “Langmuir model contemplates a chemical adsorption phenomenon”
Lines 186-187: “where concentration .. increases as the adsorbate concentration does”.
Line 188: “the strength of the link”
Line 205: “whose value”
Line 209: “Fig. 1a shows”
Line 210: “eggshell shows”
Line 211: “is in the after level”
Lines 217-218: “cycle formed in the desorption of the gas”
Line 219: “by the desorption method proposed by BJH it was found”
Lines 220-221: “24.15 nm ... 22.89 nm”
Figure 1: “Quantity adsorbed” (instead “Volume adsorbed”).
Figure 1, title: “Adsorption /desorption isotherms of eggshell”
Line 227: “The nitrogen adsorption isotherm of the composite is about 10.4 cm3/g for a relative pressure of 0.995”
Line 228: “behavior of the isotherm”
Line 230: “when reinforced with silver-iron NPs”.
Line 231: “Analyzing the desorption method proposed by BJH”.
Line 243: “may be attached on the surface” (“grafted” is better).
Lines 251-252: “pollutants to the environment”
Line 253: “any of the crystalline phases”
Line 255: “thermodynamically more stable”
Line 256: “very reactive”.
Lines 270-271: “peak” (instead “reflection”).
Line 294: “with the initial concentration of 10 mg/L” (instead “from the solution with the initial metal concentration of 10 mg/L”.
Line 310: “the same model described the process”.
Line 311: “can best describe”
Line 329: “Tables 2”
Line 347: “2.63E-2”
Lines 384-385: The sentence is disordered.
Line 403: “proposal”
Line 407: “The selectively sequence”
Lines 409-410: “the removal of each heavy metal can be enhanced in the order”
Comments for author File: 
Comments.pdf
Author Response
First of all, authors would like to thank both, editor and reviewers, for their valuable comments made to the manuscript, undoubtedly, their observations are improving significantly the quality of this revised manuscript version.
Due to the current situation, it is not possible to access the equipment to obtain original data or images, so we did everything possible to attend most of your valuable comments.
Dear Authors,
this is an interesting work, which has great importance for the improvement the ecological situation, in particular the removal of heavy metals from the water. The advantage of this work is the application of cheap and affordable food waste material – eggshell. This method has great prospects.
Despite the undoubted merits of the work, the manuscript in its present form cannot be accepted for publication in Catalysts. The manuscript needs major revision.
My comments are in attached pdf-file. I duplicate my main comments here:
1) There is no uniform labeling of the samples through the text (for example, “composite”, “nanocomposite”, “EGGSHELL/Ag-Fe”)
2) Line 105: “A sieving process allowed to obtained particles of 149 µm”. How could you isolate by sieving the particles of only one size. Usually the fraction is isolated by sieving.
(Mesh 39 particles around 0.14 mm).
3) Line 108: “5 ml of AgNO3 and FeSO4 (10-2 M) for 1 h”. Define, that it is the water solution.
4) Line 109: “The mixture was exposed to microwave radiation”. Add information about the power. RESPONSE AT A POWER OF 90%
5) Lines 109-110: Add phrase about evaporation of solvent.
6) Lines 115-116: “Surface area and pore size distribution was determined on a ISRI RIG-100 multitasking equipment, using the single point method”. How could you determine pore size distribution by single point method? RESPONSE: The surface area and pore size distribution were determined using the BET method in a multitasking equipment (ISRI RIG-100)
7) Lines 116-117: “which employs the static volumetric method; the volume adsorbed is calculated by the measured pressure of the test tube caused by changes in pressure”. It is general method, which used in low temperature nitrogen adsorption analyzers. You can just provide the reference to the paper, book or standard test method. Thank you for your observation, we provide the reference and deleted this sentence.
8) Line 142: “were in contact and stirring at 200rpm”. Add information about the temperature. Response: at room temperature
9) Lines 145-147: Most likely, this equation characterizes the adsorption capacity of the material, not the concentration of the remaining ions. That’s correct. We change the sentence for “The concentration of metal ions remaining in the solution was used to calculate the adsorption capacity of the material”.
10) Line 148: “Ce (mg/L) represent the equilibrium analyte concentrations”. What does it mean? We change that for “Ce (mg/L) is the concentration after a specific time of contact”
11) Lines 150-151: Check the numeration of equations. OK
12) Line 167: “α (mg/g h) and β (g/mg) are the initial adsorption rate, and the activation energy”. The description of this parameter does not coincide with that in the given reference. The representation of activation energy in [g/mg] is an error!
According to Largitte (2016) in page 503 before the conclusions. α is the initial sorption rate, which changes from 3.3E− 02 to 3.5E– 02 mg g−1 s−1 and the constant related to the extent of surface coverage and activation energy for chemisorption, β , from 0.133 to 0.134 g mg−1. We only used hours instead of seconds.
13) Lines 172-174: The sentence is disordered. Probably you can divide it. Ok
14) Line 184: Provide original reference for Langmuir model and equation. Ok
15) Subsection 2.3.6 Sorption isotherms: Which program was used for the model fitting?
16) Line 199 and eq. 7: The variable “n” should be marked by other symbol, because "n" you already used.
17) Line 211: “It shows a pronounced hysteresis at higher P/Po”. The hysteresis at higher P/P0 is absent. Thanks for the observation. We deleted this statement.
18) Line 212: “type II isotherm characteristic of porous media containing macropores and mesopores”. Firstly, there is type III isotherm, because the there is no convex section at the initial stage of the isotherm. Secondly, it cannot be stated about the meso- and macropores, because there is no pore size distribution. Thank you for the observation. We change that for “It shows a type III isotherm, which can be associated with a low interaction adsorbate-adsorbent. The adsorbate has almost the same affinity for itself as for the absorbent. When one molecule has been absorbed it also acts as a site for another to be attracted leading to uneven coating.”
19) Line 219: “surface area of 1.54 m2/g”. What is the accuracy of the surface areaa determination? How correct is it to give hundredths? Reponse: 1.5 m2/g. Corrected
20) Line 220: “by the desorption method proposed by BJH it was found that the material has an average pore diameter of 24.15 nm”. Incorrect sentence. The average pore diameter is calculated by equation: d=4V/S. Corrected
21) Lines 221-223: Probably, it can also be due to the accuracy of the BJH method.
22) Figure 1: Provide uniform representation of the axis, as well as the same maximum value. Provide uniform representation of isotherm in the Fig. 1a (as in the Fig. 1b), with markers. Give the labelling of the samples in the title.
23) Line 233-234: “This result suggests that the presence of the NPs on the surface of the material may block partially the pores, lowering thus the pore size diameter”. In this case you can compare the pore size distributions of both samples.
24) Lines 239-240: “The elemental analysis performed by EDS”. description of this method is absent the "Materials and methods" section.
25) Line 243: What about EDS of nanocomposite?
26) Figure 2: It seems that the magnifications of images (a) and (b) are different.
27) Line 249: “in most cases excessive borohydride is needed to accelerate the reaction”.What reaction? The description of this method is absent in "Materials and methods" section.
28) Lines 260-261: “However, the immobilization of the nanoparticles in a solid matrix can increase the resistance to diffusion”. The sentence is not clear.
29) Line 273: Give the reference.
30) Figure 3, title: “X-ray diffraction spectra(!!!) of CaCO3 in eggshell (JCPDS-PDF 05-0586)”. Actually, it is an “X-ray diffractogram of the EGGSHELL”.
31) Line 307: “are 5.18, 6.18 and 5.73, the highest values correspond to As and Hg adsorption, which reach an equilibrium time faster than the other systems.”. Firstly, give units. Secondly, just bring into lines the rates and the metals
32) Line 309: “the value of the parameter α is higher than the β in all systems”. What does this mean? Please, explain. We made a new comparison of these two parameters. “Where the value of the parameter α is higher for Pb and β for As. This means that for As molecules the available adsorption surface is greater and that for Pb the initial absorption rate is higher”.
33) Lines 312-313: “chemisorption can be considered as the dominant mechanism in both cases”. On the basis of which experimental data you made this conclusion. Please, explain. We made this conclusion based on the best fitted model from the kinetic models.
34) Line 314: “at the concentration of 10 mg/L”. What about other concentrations? The initial concentration for the kinetic study was 10 mg/L while for the isotherms we used between 1 to 5 mg/L. We try to established why we used a lower range of concentration for the isotherms, however we change the sentence for “The maximum adsorption capacity was established by the isotherms below.”
35) Lines 314-315: “adsorption capacity was established by the isotherms below”. Not clear. Did you use different relative pressures, to state this? We used the help of the mathematical models for this purpose. We cleared that in the sentence by adding this information
36) Lines 317-318, title: What process? We clarify the sentence adding the word “Adsorption process”
37) Table 1: Experimental sorption data are absent. Experimental sorption data were used for the kinetic and isotherms graphics. We incorporate the isotherm and models in figure 5.
38) Lines 335-336: “Based on this model, the adsorption capacity of EGGSHELL is greater for As than for Pb and Hg”. Isn't this the experimental data? The mathematical model was applied to the experimental data, therefore the result of the adsorption capacity is taken from the Langmuir model.
39) Lines 340-344: What is the physical meaning of the RL parameter? Give couple sentences. The RL parameter is named the separation factor and it described a favorable or unfavorable adsorption process since it defines the affinity of the adsorbate for the adsorbent. This is described in line 355.
40) Table 2: Give this table earlier, after its first mentioning.
41) Lines 365-393: Comparison can be shortened.
42) Line 369: “EGGSHELL has a low adsorption capacity compared to other materials, like eggshell”. is this the same?
43) Lines 384-385: “Other materials ... MIL-53(Fe) or MOF-808”. Give the references.
44) Line 406: “chemical adsorption process”. There is no evidence of this statement. The mathematical model is an evidence of this statement however it is true that more characterization is needed to confirm this.
45) Line 409: “silver and iron nanoparticles”. In the other text it was bimetallic nanoparticles
46) Manuscript contains unclear and incorrect sentences. For example:
Line 21: “adsorption experimental data” (instead “experimental adsorption data”)
Line 29: “major concern”
Line 30-31: “lead, arsenic and mercury falls into this category”
Line 35: “may contain high as 0.5% Pb” (instead “may contain up to 0.5% Pb”)
Line 41: “atmospheric fall out”
Line 51: “CaCO3 (like calcite) occurs naturally” (instead “CaCO3 (like calcite) exists naturally”)
Line 53: “CaCO3–H2O, CaCO3–6H2O” Ok
Line 73: “may improve” (instead “can be improved”)
Line 75: “The structure of these systems be:...”
Line 105: “allowed to obtained”
Line 151: “First propose by”
Line 156: “qt (mg/g) is the amount”
Line 177: “Langmuir model contemplates a chemical adsorption phenomenon”
Lines 186-187: “where concentration .. increases as the adsorbate concentration does”. Thank you for the observation. We change the description of the model for “Freundlich's model assumes that the process takes place in multiple layers on a heterogeneous surface and analyzed the exponential distribution of active sites and their energies”
Line 188: “the strength of the link”
Line 205: “whose value”
Line 209: “Fig. 1a shows”
Line 210: “eggshell shows”
Line 211: “is in the after level”
Lines 217-218: “cycle formed in the desorption of the gas”
Line 219: “by the desorption method proposed by BJH it was found”
Lines 220-221: “24.15 nm ... 22.89 nm”
Figure 1: “Quantity adsorbed” (instead “Volume adsorbed”).
Figure 1, title: “Adsorption /desorption isotherms of eggshell”
Line 227: “The nitrogen adsorption isotherm of the composite is about 10.4 cm3/g for a relative pressure of 0.995”
Line 228: “behavior of the isotherm”
Line 230: “when reinforced with silver-iron NPs”.
Line 231: “Analyzing the desorption method proposed by BJH”.
Line 243: “may be attached on the surface” (“grafted” is better).
Lines 251-252: “pollutants to the environment”
Line 253: “any of the crystalline phases”
Line 255: “thermodynamically more stable”
Line 256: “very reactive”.
Lines 270-271: “peak” (instead “reflection”).
Line 294: “with the initial concentration of 10 mg/L” (instead “from the solution with the initial metal concentration of 10 mg/L”.
Line 310: “the same model described the process”.
Line 311: “can best describe”
Line 329: “Tables 2”
Line 347: “2.63E-2”
Lines 384-385: The sentence is disordered.
Line 403: “proposal”
Line 407: “The selectively sequence”
Lines 409-410: “the removal of each heavy metal can be enhanced in the order”
First of all, authors would like to thank both, editor and reviewers, for their valuable comments that made of the revised manuscript an improved version of the original one, their comments significantly improved the quality of this manuscript.
Due to the current situation, it is not possible to access the equipment to obtain original data or images, so we did everything possible to attend to most of your valuable comments.
Dear Authors,
this is an interesting work, which has great importance for the improvement the ecological situation, in particular the removal of heavy metals from the water. The advantage of this work is the application of cheap and affordable food waste material – eggshell. This method has great prospects.
Despite the undoubted merits of the work, the manuscript in its present form cannot be accepted for publication in Catalysts. The manuscript needs major revision.
My comments are in attached pdf-file. I duplicate my main comments here:
1) There is no uniform labeling of the samples through the text (for example, “composite”, “nanocomposite”, “EGGSHELL/Ag-Fe”)
2) Line 105: “A sieving process allowed to obtained particles of 149 µm”. How could you isolate by sieving the particles of only one size. Usually the fraction is isolated by sieving.
(Mesh 39 particles around 0.14 mm).
3) Line 108: “5 ml of AgNO3 and FeSO4 (10-2 M) for 1 h”. Define, that it is the water solution.
4) Line 109: “The mixture was exposed to microwave radiation”. Add information about the power. RESPONSE AT A POWER OF 90%
5) Lines 109-110: Add phrase about evaporation of solvent.
6) Lines 115-116: “Surface area and pore size distribution was determined on a ISRI RIG-100 multitasking equipment, using the single point method”. How could you determine pore size distribution by single point method? RESPONSE: The surface area and pore size distribution were determined using the BET method in a multitasking equipment (ISRI RIG-100)
7) Lines 116-117: “which employs the static volumetric method; the volume adsorbed is calculated by the measured pressure of the test tube caused by changes in pressure”. It is general method, which used in low temperature nitrogen adsorption analyzers. You can just provide the reference to the paper, book or standard test method. Thank you for your observation, we provide the reference and deleted this sentence.
8) Line 142: “were in contact and stirring at 200rpm”. Add information about the temperature. Response: at room temperature
9) Lines 145-147: Most likely, this equation characterizes the adsorption capacity of the material, not the concentration of the remaining ions. That’s correct. We change the sentence for “The concentration of metal ions remaining in the solution was used to calculate the adsorption capacity of the material”.
10) Line 148: “Ce (mg/L) represent the equilibrium analyte concentrations”. What does it mean? We change that for “Ce (mg/L) is the concentration after a specific time of contact”
11) Lines 150-151: Check the numeration of equations. OK
12) Line 167: “α (mg/g h) and β (g/mg) are the initial adsorption rate, and the activation energy”. The description of this parameter does not coincide with that in the given reference. The representation of activation energy in [g/mg] is an error!
According to Largitte (2016) in page 503 before the conclusions. α is the initial sorption rate, which changes from 3.3E− 02 to 3.5E– 02 mg g−1 s−1 and the constant related to the extent of surface coverage and activation energy for chemisorption, β , from 0.133 to 0.134 g mg−1. We only used hours instead of seconds.
13) Lines 172-174: The sentence is disordered. Probably you can divide it. Ok
14) Line 184: Provide original reference for Langmuir model and equation. Ok
15) Subsection 2.3.6 Sorption isotherms: Which program was used for the model fitting?
16) Line 199 and eq. 7: The variable “n” should be marked by other symbol, because "n" you already used.
17) Line 211: “It shows a pronounced hysteresis at higher P/Po”. The hysteresis at higher P/P0 is absent. Thanks for the observation. We deleted this statement.
18) Line 212: “type II isotherm characteristic of porous media containing macropores and mesopores”. Firstly, there is type III isotherm, because the there is no convex section at the initial stage of the isotherm. Secondly, it cannot be stated about the meso- and macropores, because there is no pore size distribution. Thank you for the observation. We change that for “It shows a type III isotherm, which can be associated with a low interaction adsorbate-adsorbent. The adsorbate has almost the same affinity for itself as for the absorbent. When one molecule has been absorbed it also acts as a site for another to be attracted leading to uneven coating.”
19) Line 219: “surface area of 1.54 m2/g”. What is the accuracy of the surface areaa determination? How correct is it to give hundredths? Reponse: 1.5 m2/g. Corrected
20) Line 220: “by the desorption method proposed by BJH it was found that the material has an average pore diameter of 24.15 nm”. Incorrect sentence. The average pore diameter is calculated by equation: d=4V/S. Corrected
21) Lines 221-223: Probably, it can also be due to the accuracy of the BJH method.
22) Figure 1: Provide uniform representation of the axis, as well as the same maximum value. Provide uniform representation of isotherm in the Fig. 1a (as in the Fig. 1b), with markers. Give the labelling of the samples in the title.
23) Line 233-234: “This result suggests that the presence of the NPs on the surface of the material may block partially the pores, lowering thus the pore size diameter”. In this case you can compare the pore size distributions of both samples.
24) Lines 239-240: “The elemental analysis performed by EDS”. description of this method is absent the "Materials and methods" section.
25) Line 243: What about EDS of nanocomposite?
26) Figure 2: It seems that the magnifications of images (a) and (b) are different.
27) Line 249: “in most cases excessive borohydride is needed to accelerate the reaction”.What reaction? The description of this method is absent in "Materials and methods" section.
28) Lines 260-261: “However, the immobilization of the nanoparticles in a solid matrix can increase the resistance to diffusion”. The sentence is not clear.
29) Line 273: Give the reference.
30) Figure 3, title: “X-ray diffraction spectra(!!!) of CaCO3 in eggshell (JCPDS-PDF 05-0586)”. Actually, it is an “X-ray diffractogram of the EGGSHELL”.
31) Line 307: “are 5.18, 6.18 and 5.73, the highest values correspond to As and Hg adsorption, which reach an equilibrium time faster than the other systems.”. Firstly, give units. Secondly, just bring into lines the rates and the metals
32) Line 309: “the value of the parameter α is higher than the β in all systems”. What does this mean? Please, explain. We made a new comparison of these two parameters. “Where the value of the parameter α is higher for Pb and β for As. This means that for As molecules the available adsorption surface is greater and that for Pb the initial absorption rate is higher”.
33) Lines 312-313: “chemisorption can be considered as the dominant mechanism in both cases”. On the basis of which experimental data you made this conclusion. Please, explain. We made this conclusion based on the best fitted model from the kinetic models.
34) Line 314: “at the concentration of 10 mg/L”. What about other concentrations? The initial concentration for the kinetic study was 10 mg/L while for the isotherms we used between 1 to 5 mg/L. We try to established why we used a lower range of concentration for the isotherms, however we change the sentence for “The maximum adsorption capacity was established by the isotherms below.”
35) Lines 314-315: “adsorption capacity was established by the isotherms below”. Not clear. Did you use different relative pressures, to state this? We used the help of the mathematical models for this purpose. We cleared that in the sentence by adding this information
36) Lines 317-318, title: What process? We clarify the sentence adding the word “Adsorption process”
37) Table 1: Experimental sorption data are absent. Experimental sorption data were used for the kinetic and isotherms graphics. We incorporate the isotherm and models in figure 5.
38) Lines 335-336: “Based on this model, the adsorption capacity of EGGSHELL is greater for As than for Pb and Hg”. Isn't this the experimental data? The mathematical model was applied to the experimental data, therefore the result of the adsorption capacity is taken from the Langmuir model.
39) Lines 340-344: What is the physical meaning of the RL parameter? Give couple sentences. The RL parameter is named the separation factor and it described a favorable or unfavorable adsorption process since it defines the affinity of the adsorbate for the adsorbent. This is described in line 355.
40) Table 2: Give this table earlier, after its first mentioning.
41) Lines 365-393: Comparison can be shortened.
42) Line 369: “EGGSHELL has a low adsorption capacity compared to other materials, like eggshell”. is this the same?
43) Lines 384-385: “Other materials ... MIL-53(Fe) or MOF-808”. Give the references.
44) Line 406: “chemical adsorption process”. There is no evidence of this statement. The mathematical model is an evidence of this statement however it is true that more characterization is needed to confirm this.
45) Line 409: “silver and iron nanoparticles”. In the other text it was bimetallic nanoparticles
46) Manuscript contains unclear and incorrect sentences. For example:
Line 21: “adsorption experimental data” (instead “experimental adsorption data”)
Line 29: “major concern”
Line 30-31: “lead, arsenic and mercury falls into this category”
Line 35: “may contain high as 0.5% Pb” (instead “may contain up to 0.5% Pb”)
Line 41: “atmospheric fall out”
Line 51: “CaCO3 (like calcite) occurs naturally” (instead “CaCO3 (like calcite) exists naturally”)
Line 53: “CaCO3–H2O, CaCO3–6H2O” Ok
Line 73: “may improve” (instead “can be improved”)
Line 75: “The structure of these systems be:...”
Line 105: “allowed to obtained”
Line 151: “First propose by”
Line 156: “qt (mg/g) is the amount”
Line 177: “Langmuir model contemplates a chemical adsorption phenomenon”
Lines 186-187: “where concentration .. increases as the adsorbate concentration does”. Thank you for the observation. We change the description of the model for “Freundlich's model assumes that the process takes place in multiple layers on a heterogeneous surface and analyzed the exponential distribution of active sites and their energies”
Line 188: “the strength of the link”
Line 205: “whose value”
Line 209: “Fig. 1a shows”
Line 210: “eggshell shows”
Line 211: “is in the after level”
Lines 217-218: “cycle formed in the desorption of the gas”
Line 219: “by the desorption method proposed by BJH it was found”
Lines 220-221: “24.15 nm ... 22.89 nm”
Figure 1: “Quantity adsorbed” (instead “Volume adsorbed”).
Figure 1, title: “Adsorption /desorption isotherms of eggshell”
Line 227: “The nitrogen adsorption isotherm of the composite is about 10.4 cm3/g for a relative pressure of 0.995”
Line 228: “behavior of the isotherm”
Line 230: “when reinforced with silver-iron NPs”.
Line 231: “Analyzing the desorption method proposed by BJH”.
Line 243: “may be attached on the surface” (“grafted” is better).
Lines 251-252: “pollutants to the environment”
Line 253: “any of the crystalline phases”
Line 255: “thermodynamically more stable”
Line 256: “very reactive”.
Lines 270-271: “peak” (instead “reflection”).
Line 294: “with the initial concentration of 10 mg/L” (instead “from the solution with the initial metal concentration of 10 mg/L”.
Line 310: “the same model described the process”.
Line 311: “can best describe”
Line 329: “Tables 2”
Line 347: “2.63E-2”
Lines 384-385: The sentence is disordered.
Line 403: “proposal”
Line 407: “The selectively sequence”
Lines 409-410: “the removal of each heavy metal can be enhanced in the order”
Author Response File: Author Response.pdf
Reviewer 2 Report
The paper presents the possibility to use eggshell for the removal of heavy metals from an aqueous matrix. The results can be interesting for the scientific community, nevertheless, I suggest some modifications before its publication.
Line 93: correct Egg with egg
Line 102 and following lines: please specify the supplier of all reagents used and their purity
Line 110: please specify the power of microwaves radiation
Line 150: check the equation number. They should shift plus one (2,3,4)
Line 151: correct First with first
Line 157: please correct subscript
Line 172-173: I advise to rewrite this sentence because it is not so clear
Line 185: Correct "that the process take place" with "that the process takes place"
Figure 1: please the two figures are not homogeneous with different formats.
Figure 2a: please check the SEM info bar on the figure. Check also the position of the letter a) in the figure (also in Figure 2b)
Line 248: correct has showed with has shown
Figure 4: please insert the reference a) and b) for the two figures
Line 388: remove the dot after [43]
References: check the references. Not all have the same format (e.g. Year bold)
General observations: could be interested to evaluate the effects of some feature of aqueous solution (such as pH, presence of other ionic specie) to have an evaluation of removal performance in conditions closer to the real one.
Author Response
First of all, authors would like to thank both, editor and reviewers, for their valuable comments made to the manuscript, undoubtedly, their observations are improving significantly the quality of this revised manuscript version.
Due to the current situation, it is not possible to access the equipment to obtain original data or images, so we did everything possible to attend most of your valuable comments.
The paper presents the possibility to use eggshell for the removal of heavy metals from an aqueous matrix. The results can be interesting for the scientific community, nevertheless, I suggest some modifications before its publication.
Line 93: correct Egg with egg
Line 102 and following lines: please specify the supplier of all reagents used and their purity. We specified the supplier in lines 112 and 113
Line 110: please specify the power of microwaves radiation: 90%
Line 150: check the equation number. They should shift plus one (2,3,4)
Line 151: correct First with first
Line 157: please correct subscript
Line 172-173: I advise to rewrite this sentence because it is not so clear
Line 185: Correct "that the process take place" with "that the process takes place"
Figure 1: please the two figures are not homogeneous with different formats.
Figure 2a: please check the SEM info bar on the figure. Check also the position of the letter a) in the figure (also in Figure 2b)
Line 248: correct has showed with has shown
Figure 4: please insert the reference a) and b) for the two figures
Line 388: remove the dot after [43]
References: check the references. Not all have the same format (e.g. Year bold)
General observations: could be interested to evaluate the effects of some feature of aqueous solution (such as pH, presence of other ionic specie) to have an evaluation of removal performance in conditions closer to the real one.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Compared to the original version, the manuscript has not undergone significant changes for the better. Some of my previous key comments have not been taken into account. English was also not improved. Therefore, I have to conclude that this manuscript must be carefully revised or not accepted for publication in Catalysts. You can find my additional comments in the attached pdf-file. I strongly recommend you to carefully study all my comments, current and previous (in the doc- and pdf-files), in order to avoid further rejection of your manuscript.
The abstract does not match the text of the manuscript. For example, there is no information in the text (in the "Results and Discussion" section) concerning the dimensions and the shape of nanoparticles on the surface of the eggshell.
The catalyst is poorly characterized, for example, there is no content of the Ag and Fe. Also, it is not clear which particles are formed on the surface of the eggshell – bimetallic Ag-Fe-nanoparticles or composition of Ag and Fe2O3-nanoparticles. The size of the catalyst particles is also unclear.
There is no explanation of the increase in the surface area as a result of grafting of Ag/Fe nanoparticles.
The effect of microwave treatment on the characteristics of the nanocomposite is not emphasized in the main text of the manuscript (“Results and Discussion” section).
Explain in the text of the manuscript, on the basis of what results it was concluded that the formation of Ag-Fe nanoparticles takes place.
Add some description of information which you received on the basis of the determination of the best fitting models.
The presentation of two SEM images, which cannot be compared with each other does not bring any benefit to the manuscript. Probably, with the same magnification, valuable information can be obtained, concerning MW treatment and Ag-Fe2O3-deposition. Therefore, I recommend you to wait until the laboratory opens, when you can introduce the corresponding SEM images to the manuscript.
The article is too large. I recommend reducing its volume by deleting less important information (for example, comparison of pore size in an eggshell in the work of other authors, which is not of great importance) and focusing on the main points of your work.
Comments for author File: Comments.pdf
Author Response
- There is no information in the text (in the "Results and Discussion" section) concerning the dimensions and the shape of nanoparticles on the surface of the eggshell.
We deleted that information and replace with the correct one in line 19.
- In some cases you state the metal uptake, in some cases it is the metal ion uptake. Check this.
We checked this throughout the document, and we homogenize the term using: metal ion uptake. 3. Where is the values?The values of each adsorption capacity for every metal ion are described in line 22 and 23. 4. Observation in line 29 was changed. 5. Observation in line 52 was changed. 6. Observation in line 74 was changed 7. “atom economy” was erased.8. Observation in line 81 was changed. 9. Observation in line 89 was changed.10. What are the minimum and maximum particle sizes in a fraction? This is determined by the top and bottom sieve used.We used sieves from 20 to 59 mesh, but we only used the fraction from the sieved 39 mesh. We described this in line 103 y 104. 11. Observation in line 111 was corrected.12. Pore size distribution cannot be determined by the BET-method.Because the equipment where we determined the surface area is not available at this time, we take the decision to remove this characterization from the manuscript.13. Add the brand name and the manufacturer of the equipment for the EDS-analysisAt the moment we do not have access to the SEM equipment to correct the observations, so we decided to exclude this characterization. 14. Observation in line 124 was corrected. 15. Why you used particular temperature?Thanks for the observation, there was a mistake but we changed it in line 130.16. Only arsenic solution?We generalize this information to each of the studied ions. 17. This sentence can be omitted.The sentence was omitted.18. The observation in line 142 was corrected. 19. Observation in line 150 was corrected. 20. The sentence in line 152 was changed. 21. The observation about the parameter n was amended line 183-185.22. Observation in line 191 was corrected. 23. inappropriate phraseWe changed the inappropriate phrase in line 203-204.24. What is the evidence of the formation of Ag/Fe-nanoparticles?The evidence of the presence of Ag is the diffraction pattern while the presence of Fe (iron oxides) is confirmed by the high resolution micrograph. Both of them compared with the tables of DRX related to silver and iron oxide, respectively. 25. The sentence is not clear.We change this sentence to clarify it.26. In this case you need provide also the diffraction pattern of the initial support.We don´t have this information but there are some other papers were we used as a guide since the support is eggshell. We consider that the results of diffraction pattern of this material is almost the same in each case. 27. Provide the percentage of the Ag and Fe in the resulting bionanocomposite.To establish the percentage of Ag and Fe we need IPC or Atomic absorption spectroscopy. Unfortunately, we don’t have access to these techniques at this moment.28. The observation in line 216 was corrected. 29. The mistake in Figure 2 label was corrected. 30. The observation in line 257 was corrected.31. How is this related to model fitting?This sentence was needless we decide to erase it. 32. Not Elovich model, as it stated in the lines 322-324?The best fitted model, in this case, is Elovich. In line 322 and 324 we made only a comparison of the results of this model for each metal ion uptake. However, we change the sentence to clarify this point. 33. The observation in line 266 was corrected. 34. Experimental sorption data are absent.We consider that the best is to show the experimental data as supplementary information. Therefore, we send a document with this information.35. Observation in line 273 was corrected.36. Observation in line 275 was corrected.37. Observation in line 279 was corrected.38. The label in Table 2 was changed. 39. The mistake in education 9 was corrected.40. The observation in 297 was corrected. 41. The R-P model was change for Redlich Peterson model.42. The parameter KR was corrected. 43. indicate in the both figures, how the experimental results and the calculated values are shown44. Observation in line 328 was corrected.45. Observation in line 330 was corrected.46. Observation in line 331 was corrected.47. Observation in line 340 was corrected. 48. We change Sulphate for sufate. 49. Incorrect sentenceThe sentence was corrected. 50. Provide valuesThe values of the adsorption capacities were provided in this section. 51. Give the main adsorption parametersWe give the main adsorption parameters in this section.
Author Response File: 
Author Response.docx
Round 3
Reviewer 1 Report
The authors have modified the manuscript according to the reviewer’s remark and now this manuscript looks acceptable for publication in Catalysts. However, some polishing of the English in the text is still necessary.
Author Response
First of all, authors would like to thank both, editor and reviewers, for their valuable comments made to the manuscript, undoubtedly, their observations are improving significantly the quality of this revised manuscript version.
THE ENGLISH LANGUAGE HAS BEEN REVIEWED CAREFULLY
