Flash-Calcined Sediments for Zinc Adsorption

Round 1

Reviewer 1 Report

The article is very interesting. However, it needs some corrections and improvements to be more clear. The comments I presented below.

 1.       There is no map with the location of the sampling site.

2.       In the Chapter 2.1. Authors said that ”Raw sediments were collected from the fluvial depot of Noyelles-Sous-Lens (NSL) in the Hauts-de-France region (Northern France)”. But in the chapter 2.2.1. They said that ”The tests were performed in 8 vials (100 mL) for which the S/L ratios were respec-tively 0.01, 0.013, 0.02, 0.04, 0.1, 0.2, 0.25 and 0.5.” So that it is probable that the first sediment samples were mineralized so that they could be subjected to further research. However, the Authors do not mention mineralization.

3.       In the 3.1. Chapter Author write that ”From 50 to 800°C, the DTG evolutions of the raw sediment and FCS750 were synchronous, with diferrences only in terms of magnitude. The variations of FCS750 were of lesser extent due to a lower occurence of heat-sentsitive components. At 850°C, a significant DTG loss oberved on only the data of FCS750 was assigned to the thermogravametric behavior of neo formed phases.”  However, according to the caption to figure 2, this drawing is for the raw sediment only not for FCS750. Therefore how it have been observed  that ”From 50 to 800°C, the DTG evolutions of the raw sediment and FCS750 were synchronous, with diferrences only in terms of magnitude.” and that ”The variations of FCS750 were of lesser extent due to a lower occurence of heat-sentsitive components. At 850°C, a significant DTG loss oberved on only the data of FCS750 was assigned to the thermogravametric behavior of neo formed phases.” I should have been explained.

I think that the manuscript needs some corrections to make it clear. Authors should specify some information.

 

Comments for author File: Comments.pdf

Author Response

1.There is no map with the location of the sampling site.

=> All the sediments used in this study (NSL, La Deule, Aa, La-Lys) were collected from the sites located in the Haut-de-France region, France.

 

2.In the Chapter 2.1. Authors said that ”Raw sediments were collected from the fluvial depot of Noyelles-Sous-Lens (NSL) in the Hauts-de-France region (Northern France)”. But in the chapter 2.2.1. They said that ”The tests were performed in 8 vials (100 mL) for which the S/L ratios were respec-tively 0.01, 0.013, 0.02, 0.04, 0.1, 0.2, 0.25 and 0.5.” So that it is probable that the first sediment samples were mineralized so that they could be subjected to further research. However, the Authors do not mention mineralization.

=> No, this sediment (NSL sediment) was not mineralized before the batch experiment. In fact, the principal aim of this analysis was to determine the optimal adsorbent/adsorbate or solid/Liquid ratios used for the further experiments to prevent the influences of solid/liquid ratio on the result. The result indicated that a Solid/Liquid ratio of 0.1 was optimal ratio for batch experiments.

 

3.In the 3.1. Chapter Author write that ”From 50 to 800°C, the DTG evolutions of the raw sediment and FCS750 were synchronous, with differences only in terms of magnitude. The variations of FCS750 were of lesser extent due to a lower occurence of heat-sentsitive components. At 850°C, a significant DTG loss observed on only the data of FCS750 was assigned to the thermogravametric behavior of neo formed phases.” However, according to the caption to figure 2, this drawing is for the raw sediment only not for FCS750. Therefore how it have been observed that ”From 50 to 800°C, the DTG evolutions of the raw sediment and FCS750 were synchronous, with diferrences only in terms of magnitude.” and that ” The variations of FCS750 were of lesser extent due to a lower occurence of heat-sentsitive components. At 850°C, a significant DTG loss oberved on only the data of FCS750 was assigned to the thermogravametric behavior of neo formed phases.” I should have been explained.

=> In this study, the thermo-gravimetric analysis (TGA), and derivative thermogravimetric analysis (DTG) were used to study the thermal behavior of sediment before and after calcination corresponding to raw sediment and FCS750 respectively as presented in Figure 2. In Figure 2, the TGA and DTG results of raw sediment (before calcination) and FCS750 (after calcination) were shown to observe the effect of thermal treatment on the sediment.

Reviewer 2 Report

Comments for Editor and Authors

In the present study the authors have prepared an adsorbent via calcination of sediments at 750 °C for Zn(II) ions adsorption. They have evaluated some of the kinetic (Pseudo First Order, Pseudo Second Order and Bangham equations) and isotherm models (Langmuir, Freundlich and Temkin) for the developed process.

Unfortunately, the handling of the manuscript is quite inadequate. The aim of the study, the experimental procedures and the interpretation of the obtained results are quite complex. The following comments must be taken into account for the re-evaluation of the paper:

1.       The importance of the Zn(II) ions removal should be mentioned both in Abstract and in Introduction parts.

2.       In Abstract in line 7 “……with higher specific area and lower anthropogenic content”. How was the sediment content determined to be of anthropogenic origin? Couldn't there also be naturally contaminated metal content?

3.       Some important issues in section In 2.2.1. Aqueous Zn / calcined sediments: batch experiments,  are as follows;

·         Batch experiments is described quite complex. What is meant by Solid/Liquid? Is it Adsorbent/adsorbate? If so, use this suggested expression for clarity. Also, the expression this way seems very complex. When you say S/L ratio, what is the ratio based on? Volume or concentration? How many g of adsorbent was used instead of examining the adsorbent/adsorbate ratio? What was the sample volume studied? What was the concentration of Zn(II) ions? It would be more appropriate to express the experimental procedure in this way.

·         Batch experiments the authors wrote “The whole experiments were replicated.” But how many repetitions were performed? Please indicate.

·         In 2.2. Zinc removal experiments, in line 17-18, the sentence started with “The characterization of FCS750 / Zn interactions…..” is not clear enough. What do the given concentrations mean? It should be expressed more clearly and understandably. Also, in line 18, “isotherm” should be deleted at this point.

·         In 2.2. Zinc removal experiments, in line 20 “powdery” should be deleted.

·         In 2.2. Zinc removal experiments, in line 21, “Salinity and pH were adjusted using powdery NaCl (analytical grade) dissolved in deionized water and analytical grade HCl (0.1 M).” This sentence should be phrased better. Moreover the authors carried out the experiments at two different pH values, pH 2.0 and 7.0. pH 2.0 is adjusted with HCl but which reagent was used for pH 7.0?

4.       In Spiking experiments, in line 8, What is meant by Zn evolution? It should be more appropriately expressed.

5.       2.3.1. Kinetic and reliability, the authors used the title Kinetic and reliability. However, there is no correlation between kinetics and reliability. This title is not appropriate. It should be revised.

6.       According to Equation 2, the unit of k₂ should also be given.

7.       The title “2.3.2. Sorption models” should be changed as “2.3.2. Adsorption isotherm models”

8.       In page 5, in line 20 “1/n is between 0.1 and 1,” it should be changed as “1/n is between 0 and 1”.

9.       According to Table 1, an increase in the amount of oxides was expected after calcination, but no difference was observed. This result should be interpreted in detail. The LOI abbreviation should be explained below Table1.

10.   The element and anions concentrations given in Table 2 were determined by which method? How were the samples prepared before analysis? On the other hand according to Table 2, after calcination while the amount of some elements increased, some decreased. The reason for this increase and decrease should be explained.

11.   There are some spelling and grammatical errors in the manuscript. For example in page 9 in line 8 “oberved” should be corrected as “observed”. The whole manuscript should be thoroughly revised in this sense.

12.   While deciding on the suitability of any kinetic model, besides the size of the correlation coefficient, the experimentally obtained qe and the qe values obtained from the model should be close to each other. The R² value obtained from the PSO is high enough, but the experimentally calculated q_e and the q_e obtained from the model are very different from each other. The results need to be revised.

13.   According to page 3, Kinetics assessments were performed in the time range of 0.5 min-1440 min. I did not see the results obtained from these experiments in the manuscript. The experiments were carried out during the shaking period of 24 hours. What were the results for other contact times?

14.   The q_max value given in the abstract (82 mg/g) and the values given in Table 4 (88.3 and 89.6 mg/g for pH 7.0 and pH 2.0, respectively) are different from each other. In fact, these values are different from those given on page 13, lines 7-8 (For the experiments conducted at pH=2, the maximum adsorption deducted from Langmuir was 0.77 mmol g-1 (86.13 mg g^-1), while a maximum capacity of 0.72 mmol g^-1 (85.97 mg g^-1), was obtained at pH=7.) This expression is calculated incorrectly. 0.72x65.41=47.1 mg/g not 85.97 mg g-1 and 0.77x65.41=50.4 mg/g not 86.13 mg/g. Please check the results.

15.   In Conclusions in line 3 “…..to explore alternative ways to recycle waterway waste.” It is not correct to draw this conclusion as the recovery/desorption of Zn(II) ions was not studied in the current study.

Comments for author File: Comments.docx

Author Response

1. The importance of the Zn(II) ions removal should be mentioned both in Abstract and in Introduction parts.

• The importance of the zinc removal was introduced in Abstract and in Introduction parts. Please see the lines 1-2 in Abstract and lines 7-10 in Introduction parts.

 

 

2. In Abstract in line 7 “……with higher specific area and lower anthropogenic content”. How was the sediment content determined to be of anthropogenic origin? Couldn't there also be naturally contaminated metal content?

• It’s a mistake in this sentence. It was also corrected. In fact, the flash calcination method significantly reduced the organic matter content of the raw sediment. In this study, the organic matter content of materials was obtained by measuring the loss of mass of materials calcined at 550 °C for 2 hours.

 

 

3. Some important issues in section In 2.2.1. Aqueous Zn / calcined sediments: batch experiments, are as follows;

• Batch experiments is described quite complex. What is meant by Solid/Liquid? Is it Adsorbent/adsorbate? If so, use this suggested expression for clarity. Also, the expression this way seems very complex. When you say S/L ratio, what is the ratio based on? Volume or concentration? How many g of adsorbent was used instead of examining the adsorbent/adsorbate ratio? What was the sample volume studied? What was the concentration of Zn(II) ions? It would be more appropriate to express the experimental procedure in this way.

=>  Yes, in this study, the Solid/Liquid ratio was used as Adsorbent/Adsorbate ratio by mass. For example, 100 g of adsorbent was added to 1000 ml of adsorbate. The adsorbate used in this study has an initial Zn²⁺concentration of 15 mmol l^-1.

 

• Batch experiments the authors wrote “The whole experiments were replicated.” But how many repetitions were performed? Please indicate.
• Because the FCS₇₅₀ quantity produced in this study was relatively limited, only the analysis for the optimal solid/Liquid ratio was replicated two times.
• In 2.2. Zinc removal experiments, in line 17-18, the sentence started with “The characterization of FCS750 / Zn interactions…..” is not clear enough. What do the given concentrations mean? It should be expressed more clearly and understandably. Also, in line 18, “isotherm” should be deleted at this point.
• Yes, it was modified in the manuscript. Please see the lines 21-27 in 2.2 Zinc removal experiments.

 

• In 2.2. Zinc removal experiments, in line 20 “powdery” should be deleted.

=> Yes, it was deleted in the manuscript.

 

• In 2.2. Zinc removal experiments, in line 21, “Salinity and pH were adjusted using powdery NaCl (analytical grade) dissolved in deionized water and analytical grade HCl (0.1 M).” This sentence should be phrased better. Moreover the authors carried out the experiments at two different pH values, pH 2.0 and 7.0. pH 2.0 is adjusted with HCl but which reagent was used for pH 7.0?
• In this study, the pH was adjusted using HCl for Ph 2.0 and NaOH for pH 7.0. Please see in the manuscript the lines 21-27.

 

4. In Spiking experiments, in line 8, What is meant by Zn evolution? It should be more appropriately expressed.

• In this analysis, the Zn²⁺ concentration was measured to determine the Zn²⁺ amount absorbed by the three different types of sediments such as La Deule, Aa, and La-Lys.

 

5. 3.1. Kinetic and reliability, the authors used the title Kinetic and reliability. However, there is no correlation between kinetics and reliability. This title is not appropriate. It should be revised.

• After the revision of result (change of curve fitting for PFO model), the experimental result was similar to these obtained from the kinetic models. Please see in Table 3 and Figure 4.

6. According to Equation 2, the unit of k₂ should also be given.

Yes, the unit of k2 was added in the manuscript.

 

7. The title “2.3.2. Sorption models” should be changed as “2.3.2. Adsorption isotherm models”

• Yes, it was modified in the manuscript.

 

8. In page 5, in line 20 “1/n is between 0.1 and 1,” it should be changed as “1/n is between 0 and 1”.

• Yes, it was modified in the manuscript.

 

 

9. According to Table 1, an increase in the amount of oxides was expected after calcination, but no difference was observed. This result should be interpreted in detail. The LOI abbreviation should be explained below Table1.

LoI abbreviation: Loss on ignition, was added in the manuscript.

The chemical composition of sediments before and after the flash calcination was measured by XRF analysis. The result given in Table 1 was standardized because it did not count the LoI value including the organic matter content, and CO₂ released from the decarbonation of calcite. In addition, in the flash calcination process, a part of ultrafine of flash calcined materials lost during the process, thus, this led to an increase in the amount of oxides. The following table presents the chemical composition of sediments before and after calcination before standardization.

Chemical composition	Raw sediment	FCS750
CaO	10,57	11,25
SiO2	39,62	49,89
Al2O3	9,64	12,05
Fe2O3	5,12	5,35
SO3	0,22	0,18
Na2O	0,69	0,74
K2O	1,84	2,26
MgO	0,88	1,12
ZnO	0,27	0,31
P2O5	2,10	2,27
LOI (950°C)	27,63	13,70
Total	98,57	99,12

 

 

10. The element and anions concentrations given in Table 2 were determined by which method? How were the samples prepared before analysis? On the other hand according to Table 2, after calcination while the amount of some elements increased, some decreased. The reason for this increase and decrease should be explained.

• The element and anions concentrations given in Table 2 was determined using the leaching method according to the standard EN 1257-2. For more details, please see in the manuscript, “Sediment leaching” part. The decrease in the amount of elements could be explained by the decomposition under the thermal effect and the loss of ultrafine parts during the calcination process.

 

 

11. There are some spelling and grammatical errors in the manuscript. For example in page 9 in line 8 “oberved” should be corrected as “observed”. The whole manuscript should be thoroughly revised in this sense.

• Yes, it was corrected in the manuscript.

 

 

12. While deciding on the suitability of any kinetic model, besides the size of the correlation coefficient, the experimentally obtained qe and the qe values obtained from the model should be close to each other. The R² value obtained from the PSO is high enough, but the experimentally calculated q_e and the q_e obtained from the model are very different from each other. The results need to be revised.

• After the revision, the experimental result was similar to these obtained from the kinetic models. In this manuscript, the function non-linear was used to fit the data for PFO model. Please see the result given in Table 3 and Figure 4.

 

13. According to page 3, Kinetics assessments were performed in the time range of 0.5 min-1440 min. I did not see the results obtained from these experiments in the manuscript. The experiments were carried out during the shaking period of 24 hours. What were the results for other contact times?

• It was a mistake in the manuscript, in the kinetic experiment, the analysis was performed for 480 minutes. However, it can be seen in Figure 4 that after 240 minutes, the adsorption kinetics slow down significantly, thus, we decided to performed the analysis until 480 minutes.

 

 

14. The q_max value given in the abstract (82 mg/g) and the values given in Table 4 (88.3 and 89.6 mg/g for pH 7.0 and pH 2.0, respectively) are different from each other. In fact, these values are different from those given on page 13, lines 7-8 (For the experiments conducted at pH=2, the maximum adsorption deducted from Langmuir was 0.77 mmol g-1 (86.13 mg g^-1), while a maximum capacity of 0.72 mmol g^-1 (85.97 mg g^-1), was obtained at pH=7.) This expression is calculated incorrectly. 0.72x65.41=47.1 mg/g not 85.97 mg g-1 and 0.77x65.41=50.4 mg/g not 86.13 mg/g. Please check the results.

• Yes, the result was revised and corrected in the manuscript. Please see the result given in Adsorption capacity part.

 

15. In Conclusions in line 3 “…..to explore alternative ways to recycle waterway waste.” It is not correct to draw this conclusion as the recovery/desorption of Zn(II) ions was not studied in the current study.

• Yes, it was modified in the manuscript. Please see in the Conclusion part.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Dear Editor,

I have reviewed the manuscript entitled “Flash-calcined sediments for zinc adsorption” once more. The authors have made an effort in responding adequately my comments, and also they made all of the changes necessary. I recommend that this paper can be published in Sustainability in its present form.