Preconcentration of Silver from Real Mine Wastes Using Deep Eutectic Solvent-Assisted Solidified Floating Organic Drop Microextraction and Determination by Flame Atomic Absorption Spectrometry

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1. I would suggest avoiding the use of words from the article title in the keywords.
2. The discussion is very short. It should be more extensive, with deeper insights.
3. In Figure 2, I would recommend including a curve, as this would make it easier to visualize the dynamics of the changes.
4. I could not find a section on the statistical analysis performed.
5. The conclusions should be made more specific. Including and citing sources in the conclusions is unacceptable.

Comments for author File: Comments.pdf

Author Response

1. I would suggest avoiding the use of words from the article title in the keywords.

We sincerely thank the reviewer for this valuable suggestion regarding the keywords. After careful consideration, we decided to retain a limited overlap with the title to ensure that the manuscript is easily discoverable in scientific databases and search engines. These specific terms are crucial for proper indexing and for reaching the intended audience.

2. The discussion is very short. It should be more extensive, with deeper insights.

We sincerely thank the reviewer for this valuable suggestion. The discussion has been revised and slightly expanded to provide clearer emphasis on the advantages of DES-assisted SFODME, including its green chemistry aspects, operational simplicity, and potential for routine application. This revision offers a more comprehensive interpretation while keeping the section concise and focused.

3. In Figure 2, I would recommend including a curve, as this would make it easier to visualize the dynamics of the changes.

In the revised manuscript, Figure 2 has been updated to include a smooth curve connecting the data points, which improves the visualization of the observed trends and makes the changes easier to interpret.

4. I could not find a section on the statistical analysis performed.

In studies focusing on analytical method development and validation, result reliability is typically demonstrated through replicate measurements, with data reported as mean ± standard deviation. This approach is widely accepted in analytical chemistry practice (e.g., ICH and AOAC guidelines) as sufficient for demonstrating precision and reproducibility. Calibration curves with correlation coefficient values, linear ranges and enhancement factor calculations were done. Moreover, the relevant statistical calculations, including LOD, LOQ, linearity, and precision metrics like relative standard deviation, are summarized and discussed in Section 3.9 (“Analytical Performance of the Proposed Method”) to provide a clear overview of the method’s validation results.

5. The conclusions should be made more specific. Including and citing sources in the conclusions is unacceptable.

We sincerely thank the reviewer for this important comment. The conclusion section has been revised to focus exclusively on the key findings of this study, presented in a more specific and concise manner. All literature citations have been removed, and the revised text highlights the analytical performance, applicability, and potential industrial relevance of the developed method.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This work presented a novel, environmentally friendly analytical method for the preconcentration and determination of silver in mining waste using DES in combination with SFODME and FAAS. Having carefully gone through this paper, I suggest a major revision based on the following comments. 

1. Abstract:

(1) Lines 14-17, the authors are recommended to delete “Silver, a critical element ……of traditional mining”, or move it at the beginning of abstract.

(2) Lines 17-18, please delete the sentence “The proposed method…..under optimized conditions”.

(3) Keywords: Please use the abbreviation of “Solidified floating organic drop microextraction” and “deep eutectic solvent”, and change “atom absorption spectroscopy” to “FAAS”.

2. Line 90, the authors already mentioned the abbreviation of Solidified floating organic drop microextraction at line 84, why not use the abbreviation directly? The authors also have to format the usage of abbreviations through the whole manuscript. Other examples: line 92, the same problem.
3. Line 104, the chemical form of choline chloride and urea should be formatted since the numbers are subscripts. The same problem can be found through the whole manuscript.
4. Figures: (1) Why all the figures don’t have tick marks? Figure captions don’t well describe the contents, e.g., Figure 2, “Optimization of pH", it is better to revise it as “Results of pH optimization”. (2) Figure 4, why use absorbance and what does the absorbance come from? It is better to use the recovery of Ag. Also, why the absorbance is only 0.1? What is the unit of the absorbance?
5. Lines 308-317, if the authors add NaCl, I don’t think you can measure Ag in your sample since there will be precipitation of AgCl. The same problems for addition of KCl and HgCl₂.
6. Lines 317-326, how did you construct the calibration equations? Were all the standard solutions producing the first linear equation treated by SFODME before the calibration graph establishment? Why there is an enhancement factor?
7. Line 317 and line 3333 why the subtitles are the same?
8. Line 336, why the recovery only reached 93%? Such a recovery range of 80%–93% surely demonstrates that the extraction efficiency of Ag by this proposed method is not optimal. The authors are recommended to check the whole procedures or give a reasonable explanation of this low recovery range.
9. Table 4, why not use LOD for limit of detection since the authors already presented it in the text? The authors used FAAS for Ag measurement, I don’t think it is necessary to compare the proposed method to ETAAS and GFAAS since they mainly focused on the preconcentration method. It is highly suggested to compare the preconcentration methods based on FAAS analysis.
10. Line 384, it is wired that references are cited in the section of Conclusion. The authors are highly suggested to discuss why the proposed method falls into green-chemistry in the section of “Discussion”.

Author Response

This work presented a novel, environmentally friendly analytical method for the preconcentration and determination of silver in mining waste using DES in combination with SFODME and FAAS. Having carefully gone through this paper, I suggest a major revision based on the following comments. 

1. Abstract:

(1) Lines 14-17, the authors are recommended to delete “Silver, a critical element ……of traditional mining”, or move it at the beginning of abstract.

(2) Lines 17-18, please delete the sentence “The proposed method…..under optimized conditions”.

(3) Keywords: Please use the abbreviation of “Solidified floating organic drop microextraction” and “deep eutectic solvent”, and change “atom absorption spectroscopy” to “FAAS”.

We sincerely thank the reviewer for the valuable comments on the abstract and keywords. In line with these suggestions, the sentence “Silver, a critical element … of traditional mining” has been moved to beginning of abstract, and the sentence “The proposed method … under optimized conditions” has also been deleted. In addition, the keywords have been revised to use the abbreviations “SFODME” and “DES,” and “atom absorption spectroscopy” has been replaced with “FAAS,” as recommended.

1. Line 90, the authors already mentioned the abbreviation of Solidified floating organic drop microextraction at line 84, why not use the abbreviation directly? The authors also have to format the usage of abbreviations through the whole manuscript. Other examples: line 92, the same problem.

The manuscript has been carefully revised to ensure consistent use of abbreviations throughout the text. “Solidified floating organic drop microextraction” has been replaced with “SFODME” after its first mention at line 84, and similar corrections have been made at line 92 and other relevant locations to maintain uniform formatting.

1. Line 104, the chemical form of choline chloride and urea should be formatted since the numbers are subscripts. The same problem can be found through the whole manuscript.

The chemical formulas of choline chloride and urea have been corrected, and all numerical subscripts have been properly formatted throughout the manuscript.

1. Figures: (1) Why all the figures don’t have tick marks? Figure captions don’t well describe the contents, e.g., Figure 2, “Optimization of pH", it is better to revise it as “Results of pH optimization”. (2) Figure 4, why use absorbance and what does the absorbance come from? It is better to use the recovery of Ag. Also, why the absorbance is only 0.1? What is the unit of the absorbance?

We sincerely thank the reviewer for these detailed observations regarding the figures. We agree with the comment on the figure captions, and all figure captions have been revised to better describe the contents, following the suggested style (e.g., Figure 2 has been changed to “Results of pH optimization”).

 

We would like to clarify that absorbance is routinely used for optimization studies in preconcentration studies. Absorbance is a direct output of the FAAS instrument and, according to Beer-Lambert Law absorbance has no unit.

 

After completing the experimental optimization of all parameters, the analytical results were obtained using a flame AAS instrument. Calibration of the instrument is an essential first step before any measurements can be performed. In accordance with common academic practice, AAS instruments are calibrated using absorbance values. Calibration curves constructed from absorbance data are then used to evaluate the absorbance values of the solutions collected during the experimental studies, ensuring consistency and reliability of the measurements. Recovery experiments were indeed conducted, but they were performed after the optimizations and are already reported in the manuscript. For this reason, absorbance rather than recovery was used to present the optimization results, in line with the established methodology in this field.

1. Lines 308-317, if the authors add NaCl, I don’t think you can measure Ag in your sample since there will be precipitation of AgCl. The same problems for addition of KCl and HgCl₂.

We sincerely thank the reviewer for this important observation. We agree that Ag⁺ readily precipitates as AgCl in the presence of chloride at moderate concentrations. In our interference studies the concentrations of NaCl, KCl, and HgCl₂ were quite high and at higher chloride levels silver forms soluble chloro-complexes such as AgCl₂⁻, which increase its solubility and can prevent complete precipitation (Seward, 1976, Geochim. Cosmochim. Acta, 40, 865–875). In addition, mechanistically, the ChCl–Urea DES enhances extraction of Silver through chlo-ride-driven speciation, ion-pairing, and interfacial microenvironment effects. At pH ≈ 3, chloride from choline chloride shifts Ag(I) toward extractable chloroargentate species (e.g., [AgCl₂]⁻/[AgCl₃]²⁻), which form tight ion pairs with the permanently charged choline cation, yielding neutral or less-polar aggregates that preferentially partition into the floating 1-dodecanol drop.

1. Lines 317-326, how did you construct the calibration equations? Were all the standard solutions producing the first linear equation treated by SFODME before the calibration graph establishment? Why there is an enhancement factor?

We sincerely thank the reviewer for this question and the opportunity to clarify our procedure. Two calibration curves were constructed: (1) a direct calibration curve prepared using aqueous standard solutions measured by FAAS without preconcentration, and (2) a calibration curve obtained after applying the SFODME procedure to the same set of standards under optimized conditions. All standards used for the second curve were treated by SFODME before measurement to ensure accurate representation of the preconcentration step. The enhancement factor was calculated as the ratio of the slopes of these two calibration curves, which quantifies the analytical signal improvement achieved by the proposed method.

 

 

 

 

Enhancement Factor = Slope of calibration curve with preconcentration / Slope of calibration curve without preconcentration

Enhancement Factor = 1.7912/0.0642 = 27.9

 

1. Line 317 and line 3333 why the subtitles are the same?

We sincerely thank the reviewer for this critical observation. The subtitle at line 333 has been corrected from “Analytical Performance of the Proposed Method” to “Analysis of Certified Reference Materials” to avoid duplication and to more accurately reflect the content of the section.

1. Line 336, why the recovery only reached 93%? Such a recovery range of 80%–93% surely demonstrates that the extraction efficiency of Ag by this proposed method is not optimal. The authors are recommended to check the whole procedures or give a reasonable explanation of this low recovery range.

Silver is well known to be challenging to recover quantitatively due to its strong tendency to form stable complexes and precipitates, especially in real waste matrices. The optimization experiments were performed using sterile, synthetic samples. Once the optimal conditions were established, the proposed method was applied to real and complex samples to determine recovery values. This approach is consistent with the methodology reported in the literature, where similar studies are typically designed in the same way. The recovery values presented in the relevant table correspond to certified reference materials and real mining samples. It is well recognized that such real samples possess highly complex matrix compositions and challenging chemical forms. When compared with values reported in the literature, the recoveries achieved by the proposed method are considered highly satisfactory for practical applications.

In this study, our primary objective was to design a greener and safer preconcentration method rather than to maximize recovery at all costs. The use of choline chloride–urea DES and very low volumes of 1-dodecanol minimizes environmental impact and solvent toxicity, aligning with green chemistry principles. The observed recovery values are still sufficiently high for reliable quantification, as supported by the good precision, linearity, and low LOD achieved. Future optimization could focus on exploring alternative DES compositions to further enhance recovery while maintaining the method’s environmental benefits.

1. Table 4, why not use LOD for limit of detection since the authors already presented it in the text? The authors used FAAS for Ag measurement, I don’t think it is necessary to compare the proposed method to ETAAS and GFAAS since they mainly focused on the preconcentration method. It is highly suggested to compare the preconcentration methods based on FAAS analysis.

In the revised manuscript, the abbreviation “LOD” has been used consistently in Table 4 to match its presentation in the text. Regarding the second suggestion, we respectfully chose not to limit the comparison solely to FAAS-based preconcentration studies, as such studies are relatively scarce and a broader comparison allows for a more comprehensive evaluation of the analytical performance of the proposed method. Including results from ETAAS- and GFAAS-based approaches provides readers with a wider perspective on how the method compares to other commonly used techniques for silver determination.

1. Line 384, it is wired that references are cited in the section of Conclusion. The authors are highly suggested to discuss why the proposed method falls into green-chemistry in the section of “Discussion”.

Thank you for pointing this out. We agree with this comment. Therefore,  all references have been removed from the Conclusion section in the revised manuscript as recommended. In addition, the Discussion section has been expanded to clearly explain why the proposed method aligns with the principles of green chemistry, emphasizing the use of low-toxicity deep eutectic solvents, minimal organic solvent consumption, and the elimination of centrifugation, which together reduce environmental impact and enhance the method’s sustainability.

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript tackles an important analytical challenge: preconcentrating trace Ag(I) from complex mine-waste matrices using a DES-assisted SFODME procedure coupled to FAAS. The topic is timely from both a green-chemistry and circular-economy perspective, and the authors present a straightforward workflow with potentially low cost and good lab accessibility. The optimization study is comprehensive (pH, DES dose, extractant volume, mixing, temperature, time, final volume), and the application to real tailings/wastes is useful for practitioners. With that said, several substantial issues regarding novelty claims, validation depth, data consistency, and reporting clarity must be resolved before the paper can be considered further. Here are my some advices and suggestions.

1. What is specifically new vs prior DES-based and SFODME Ag methods? Add a short literature map clarifying the gap your work fills.
2. How does your method compare against an orthogonal technique (e.g., ICP-MS/ICP-OES or GFAAS)? Provide method-comparison statistics and plots.
3. Do standard-additions or matrix-matched calibration change the slope vs external calibration? Show recoveries in at least two real samples.
4. Are LOD/LOQ, linear range, and enhancement factor calculated with consistent units? Add raw calibration data, blank details (n≥10), and uncertainty.
5. Under what exact conditions (ionic strength, counter-ions, DES dose) were tolerances measured? Include error bars and a brief speciation/controls set to support the extraction mechanism.
6. What are day-to-day precision/ruggedness results, approximate throughput, and quantitative greenness metrics (e.g., AGREE/GAPI)? Clarify data availability.

Author Response

This manuscript tackles an important analytical challenge: preconcentrating trace Ag(I) from complex mine-waste matrices using a DES-assisted SFODME procedure coupled to FAAS. The topic is timely from both a green-chemistry and circular-economy perspective, and the authors present a straightforward workflow with potentially low cost and good lab accessibility. The optimization study is comprehensive (pH, DES dose, extractant volume, mixing, temperature, time, final volume), and the application to real tailings/wastes is useful for practitioners. With that said, several substantial issues regarding novelty claims, validation depth, data consistency, and reporting clarity must be resolved before the paper can be considered further. Here are my some advices and suggestions.

1. What is specifically new vs prior DES-based and SFODME Ag methods? Add a short literature map clarifying the gap your work fills.

This work addresses the preconcentration of Ag(I) from complex mine-waste matrices using DES-assisted SFODME coupled to FAAS. Prior studies predominantly relied on DLLME/CPE or SFODME without DES, were limited to model solutions, or required chelators/centrifugation, which increases solvent use and operational complexity. Here, a chloride-rich ChCl:urea DES is integrated as a benign phase-modifier to enhance transfer without toxic chelating agents, using only [200 µL] 1-dodecanol and a solidification step that obviates centrifugation. Unlike earlier reports, we validate on certified materials and real tailings from Au–Ag operations, demonstrating matrix tolerance and routine-lab compatibility. The method delivers low LOD, high precision and a notable enhancement factor with small solvent volumes under mild conditions. Collectively, these features fill a gap between green preconcentration and real-sample applicability in FAAS workflows. This information has been included at the end of the Introduction to clarify the literature gap with our work.

1. How does your method compare against an orthogonal technique (e.g., ICP-MS/ICP-OES or GFAAS)? Provide method-comparison statistics and plots.

The analysis technique employed in this study is flame atomic absorption spectrometry (FAAS). FAAS is an economical and widely available instrument that can be found in nearly every analytical laboratory. The techniques mentioned by the reviewer, such as GFAAS, ICP-OES, or ICP-MS, indeed offer significantly lower detection limits and higher sensitivity compared with conventional FAAS. However, in our approach, the preconcentration step enabled the quantification of silver ions at concentrations that would otherwise be below the direct detection capability of a standard FAAS instrument. This effectively brings the analytical performance closer to the detection limits typically achievable with the more sensitive techniques referenced by the reviewer. While FAAS typically allows detection at the ppm level, the proposed preconcentration procedure enables the determination of silver ions even at the ppb level using a conventional FAAS instrument rather than ICP-MS/ICP-OES or GFAAS.

1. Do standard-additions or matrix-matched calibration change the slope vs external calibration? Show recoveries in at least two real samples.

While standard-additions or matrix-matched calibration can be informative, the present work focuses on developing the DES-SFODME preconcentration step for FAAS. We therefore adopted external calibration with reagent-matched standards and assessed potential matrix effects through tolerance tests and the recoveries/CRM agreement already reported, which indicated only minor matrix influence under the optimized conditions. To keep the study’s scope concise and avoid duplicating calibration schemes, we did not perform additional experiments. This rationale has been clarified in the manuscript, and we note as a limitation that an expanded SA/MM comparison across more mine-waste types would be a valuable direction for future work.

1. Are LOD/LOQ, linear range, and enhancement factor calculated with consistent units? Add raw calibration data, blank details (n≥10), and uncertainty.

We appreciate the reviewer’s detailed note. Unit consistency is maintained throughout (concentration in mg L⁻¹; absorbance unitless). LOD and LOQ were calculated as 3 σ and 10 σ, respectively, where σ is the standard deviation of n = 10 blank measurements. To quantify the enhancement, we constructed two calibration curves under identical conditions: (1) a direct FAAS calibration without preconcentration and (2) a calibration after DES-SFODME; the enhancement factor (EF) was computed as the ratio of these slopes. For brevity, we report the resulting metrics in the manuscript, and the underlying raw calibration pairs and blank readings are available upon request.

 

 

 

 

Enhancement Factor = Slope of calibration curve with preconcentration / Slope of calibration curve without preconcentration

Enhancement Factor = 1.7912/0.0642 = 27.9

1. Under what exact conditions (ionic strength, counter-ions, DES dose) were tolerances measured? Include error bars and a brief speciation/controls set to support the extraction mechanism.

We thank the reviewer for these constructive suggestions. The tolerance experiments were carried out under the same optimized conditions as the main procedure described in the Experimental section (identical pH, DES dose, extractant volume, mixing, temperature, extraction time, and final volume), ensuring a consistent ionic environment across tests; under these conditions no visible AgCl precipitation was observed. Each tolerance point was measured in triplicate and the figure values represent the means; precision for these experiments is already summarized in the manuscript’s analytical-performance metrics, so we did overplot error bars. The tested trends are consistent with qualitative Ag(I) speciation at the working pH and controlled ionic strength used in this study, which were chosen to avoid conditions that would favor AgCl(s) formation. The role of the DES-assisted step is reflected by the increased analytical signal relative to direct FAAS under otherwise identical matrices (captured by the reported enhancement factor).

1. What are day-to-day precision/ruggedness results, approximate throughput, and quantitative greenness metrics (e.g., AGREE/GAPI)? Clarify data availability.

We would like to extend our special thanks to the reviewer for this insightful comment, which significantly improved the comprehensiveness and academic quality of our manuscript. In the revised manuscript, a greenness assessment was added using the AGREE tool, which highlights the method’s low solvent consumption, low hazard, and energy-efficient operation.

Instrument calibration was performed at the start of each analytical day and repeated as necessary during the day to maintain measurement accuracy. In addition, as a routine laboratory habit the application of control charts was performed. The upper control limit (UCL) and the lower control limit (LCL) routinily checked and if the data appear normal then experimental studies performed.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Comments for the revision:

(1) Lines 316-318, why the authors choose these interferences, is there any possibility that there will be SCN- for this process? Also, it's better to use interferent/Ag than Ag/interferent. Another question, when you add NaCl, how do you consider the dual interferences from Na and Cl on Ag measurement? Will the formed AgCl₂⁻ influence the measurement accuracy of Ag?

(2) Table 3, the author should also use spiked-recovery method to check the real sample analysis.

(3) The Green chemistry evaluation should be given in Discussion, not Conclusion, and NO reference in section of Conclusion.

(4) All the figures, why they don't have tick marks? There should be tick marks for the corresponding labels. This must be revised, and the lines of the x-axis/y-axis should be bolder than plots. 

Author Response

Comments for the revision:

(1) Lines 316-318, why the authors choose these interferences, is there any possibility that there will be SCN- for this process? Also, it's better to use interferent/Ag than Ag/interferent. Another question, when you add NaCl, how do you consider the dual interferences from Na and Cl on Ag measurement? Will the formed AgCl₂⁻ influence the measurement accuracy of Ag?

Interferents were chosen based on ions typically present in mine-waste matrices (alkali, alkaline earth, and transition metals, as well as anions such as chloride, sulfate, phosphate).

Thiocyanate (SCN⁻) can indeed be present in gold and silver mining wastes, particularly when cyanidation processes are employed for metal extraction. During cyanide leaching, silver and gold are dissolved using cyanide salts (NaCN/KCN). Under oxidizing conditions and in the presence of transition metals such as Fe³⁺, cyanide undergoes degradation, forming thiocyanate as a major by-product. As a result, SCN⁻ is frequently detected in tailings and effluents from gold–silver operations. Previous studies have highlighted the occurrence of thiocyanate in mining wastewaters and its environmental relevance (Logsdon et al., 1999; Akcil, 2003; Akcil & Koldas, 2006).

References:

• Logsdon, M. J., Hagelstein, K., & Mudder, T. I. (1999). The Management of Cyanide in Gold Extraction. International Council on Metals and the Environment, Ottawa, Canada.
• Akcil, A. (2003). Destruction of cyanide in gold mill effluents: biological versus chemical treatments. Biotechnology Advances, 21(6), 501–511.
• Akcil, A., & Koldas, S. (2006). Acid Mine Drainage (AMD): causes, treatment and case studies. Journal of Cleaner Production, 14(12–13), 1139–1145.

 

Table 1. Tolerance limits (error < 5%) of interfering ions on the determination of 50 μg/L Ag(I) by the proposed method.

Ion	Added as	[Interferent] / [Ag]	Ion	Added as	[Interferent] / [Ag]
K+	KCl	> 500	Al3+	Al(NO3)3	> 1500
Na+	NaCl	> 1500	Fe3+	Fe(NO3)3	1000
Zn2+	Zn(NO3)2	200	Cr3+	Cr(NO3)3	> 150
Cd2+	Cd(NO3)2	200	As3+	As2O3	1200
Hg2+	HgCl2	> 150	SCN-	NH4SCN	1200
Mn2+	Mn(NO3)2	> 1500	NO3-	KNO3	500
Ni2+	Ni(NO3)2	400	Cl-	NaCl	> 750
Mg2+	MgSO4	300	CO32-	Na2(CO3)	400
Cu2+	Cu(NO3)2	> 200	SO42-	MgSO4	500

Based on the reviewer’s feedback, the table containing the interference studies has been redesigned. The new version has been added to the manuscript and is presented below for your information.

In interference studies, by the very nature of such experiments, the target ion (interfering ion) must be introduced in the form of a chemical compound, meaning that its counter-ion is inevitably present as well. Therefore, any observed change in absorbance essentially reflects the combined or dual effect of both species. This is the conventional and widely accepted practice for interference testing, and our experiments were carried out accordingly.

With respect to chloride, we fully acknowledge that Ag⁺ easily forms a precipitate of AgCl when chloride is present at moderate levels. However, when the chloride concentration becomes higher, silver begins to form soluble chloro-complexes such as AgCl₂⁻, which redissolve the precipitate and increase solubility (Seward, 1976, Geochimica et Cosmochimica Acta, 40, 865–875). Thus, depending on chloride concentration, both precipitation and redissolution phenomena can occur, and under our experimental conditions, no complete loss of analyte was observed.

In a situation where chlorine, and DES solutions are in competition for silver, the silver is first captured by the DES solutions and taken to the extraction steps. No precipitation problems were encountered during the experimental studies.

(2) Table 3, the author should also use spiked-recovery method to check the real sample analysis.

Through the comment of reviewer, the proper spike experiments have just performed and results were summarized in the new version of Table 3. Considering the established linear range of the method, the silver concentrations in the Mining Waste-1 and Mining Waste-2 samples were already relatively high. To avoid exceeding the validated linear range, spike-recovery experiments were not performed for these particular samples.

Table 3. Proposed method applied on real samples.

Mining Waste - 1*		Mining Waste - 2*		Mining Waste - 3		Tailings Sample
Added (mg/L)	Found (mg/L)	Added (mg/L)	Found (mg/L)	Added (mg/L)	Found (mg/L)	Added (mg/L)	Found (mg/L)
0	0.201 ± 0.003	0	0.174 ± 0.002	0	0.087 ± 0.001	0	0.049 ± 0.001
50	-	50	-	50	0.130 ± 0.001	50	0.094 ± 0.001
100	-	100	-	100	0.178 ± 0.002	100	0.152 ± 0.002

*Considering the linear range in which the method operates, it was observed that the silver concentration values ​​for Mining Waste-1 and Mining Waste-2 samples were high, and spike experiments were not applied to these samples in order not to exceed the linear range.

 

(3) The Green chemistry evaluation should be given in Discussion, not Conclusion, and NO reference in section of Conclusion.

We thank the reviewer for this valuable comment. In the revised manuscript, the green chemistry evaluation has been moved from the Conclusion to the Discussion section as suggested, and all references have been removed from the Conclusion section.

(4) All the figures, why they don't have tick marks? There should be tick marks for the corresponding labels. This must be revised, and the lines of the x-axis/y-axis should be bolder than plots. 

We carefully considered the reviewer’s observation. Tick marks have now been added to all figures, and the axes were redrawn with thicker lines so that they appear clearer than the plotted data. We believe these modifications improve both the accuracy and the visual clarity of the figures.

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have addressed all concerns. I have no further questions. The manuscript can be published.

Author Response

Thanks to the referee's critical and valuable comments, our manuscript has become more academic and easier to understand. We would like to express our sincere gratitude to the referee for his/her efforts and critical comments.