Pb(II) Removal from Aqueous Solutions by Adsorption on Stabilized Zero-Valent Iron Nanoparticles—A Green Approach

Round 1

Reviewer 1 Report

This manuscript falls within the scope of the subject, the present study describes a green approach to synthesizing stabilized nZVI, using biomass as a porous support material，the topic selection has important scientific significance and practical value. The results are well presented and the conclusion has useful implication for contributing to water treatment technology and method. Therefore, it is recommended to accept after minor revision.

1.     At the end of the abstract, it is suggested to add a sentence about the possible applications of the research results of this manuscript.

2.     The research progress is insufficient. It is recommended to read and cite the following literature.

[1] Liu, Z., Xu, Z., Xu, L. et al. Modified biochar: synthesis and mechanism for removal of environmental heavy metals. carbon res 1, 8 (2022). https://doi.org/10.1007/s44246-022-00007-3

[2]Wang, X., Liang, D., Wang, Y. et al. A critical review on the biological impact of natural organic matter on nanomaterials in the aquatic environment. carbon res 1, 13 (2022). https://doi.org/10.1007/s44246-022-00013-5

3. How to verify the correctness of removal efficiency?

4.The data should be tested and analyzed for difference, and the error line should be added in the figures

5.Conclusions need to be condensed, three to five points.

Author Response

Please see attached file. 

Reviewer 2 Report

The below comments are provided to improve the quality of this manuscript.

Lines 50 and 51, the authors used “emission” and “exposure” to describe Pb’s release and its impact in the gas phase. However, in line 52, the authors explained the Pb(II) removal from water. Please revise the phrase to be more logical.

Line 80, typo “graet?”

Line 218, Eq. 4, kl and Kl?

Line 231, Eq. 7 is wrong. The denominator’s qe shouldn’t be squared. Please recheck the equation and data.

Line 236, please recheck and correct the units of k1 and k2.

Line 237, first-order and second-order or Pseudo-first-order and Pseudo-second-order?

Lines 256 and 258, what is the relationship between kL in Eq. 12 and Kd in Eq. 13?

Lines 276 and 279, the formats of elemental contents in Table 1 and Table 2 should be consistent.

Lines 364 and 365, what is the accordance that the authors proposed the competition for active sites by H+ ions and Pb(II) ions? Does OH- not compete for the active site with Pb(II)? The pH effect is complicated; the authors must consider the impact of surface charge and Pb(II) species.

Line 387, the variations of repeated data in Figure 3a are enormous. How do the authors prove the reliability of the data?

Lines 421-423, pseudo-second-order cannot be used to directly prove the chemisorption. It assumes the relationship between the adsorbate and the adsorption sites. Please refer to the given article and revise the explanation. Hubbe, M. A., Azizian, S., and Douven, S. (2019). "Implications of apparent pseudo-second-order adsorption kinetics onto cellulosic materials: A review," BioRes. 14(3), 7582-7626.

Lines 454-456, what can we understand from the isotherm parameters? Please discuss the possible adsorption behavior according to the assumptions of isotherm equations in the main text.

Author Response

Please see attached file. 

Author Response File: Author Response.docx

Reviewer 3 Report

This manuscript focus on the Cd2+ removal property of rice straw derived activated carbon load with Fe nanoparticles, which is of interesting to broad readers. After carefully reading, it was found that this article needs major revisions because several issues and explanations are still need to be clarified. 

1.      “nano-bio-composite” in line 25 is suggested to be replaced by “nanocomposite” since either Fe or rice straw derived activated carbon could be related to “bio”.

2.      The abbreviation for Nano Zero Valent iron particles is suggested to be revised as “nZVFe”.

3.      “bioactivated carbon” is suggested to be replaced with “biomass derived activated carbon”.

4.      Activated carbon could be synthesized via various activation agents and are widely applied in waste water treatment, energy storage devices and other fields. More references are suggested to be cited in the introduction for broad readers, e.g. Journal of Bioresources and Bioproducts 2021, 6 (4), 292-322; Journal of Bioresources and Bioproducts 2022, 7 (2), 109-115; Biochar 2022, 4 (1), 50; Inorganic Chemistry Frontiers 2022, 9, 6108-6123.

5.      Please pay attention to the writing of units, e.g. “0.05o/s”, “mg/g”, “l/mg”, “kJ/mol”, “J mol−1 K−1” and “kJ mol−1” needed to be revised in the same format. Moreover, there should be a space between the number and the unit.

6.      Please check the writing of superscripts and subscripts. For example, “BH4-” in line 170 needs to be revised.

7.      Why the activation temperature is fixed at 500 oC? How about the activation temperature on the porosity of activated carbon?

8.      How about the content of iron nanoparticles in the composite on the absorption capacity of Cd2+?

9.      Specific surface area and pore size distribution are important for absorbents. Please add the porosity data if available.

10.   Could the composite be recycled and reused? How about the absorption capacity at different cycle?

Author Response

Please see attached file. 

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The present version of the manuscript has been revised correctly according to my comments, and it is recommended for publication now.

Reviewer 3 Report

The manuscript has been revised according to the comments and is acceptable.