An Investigation of Lanthanum Recovery from an Aqueous Solution by Adsorption (Ion Exchange)

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1. The behavior of all elements, including lanthanum and other REEs, on the studied sorbents has been known since the middle of the last century. It is necessary to justify the scientific novelty of the study, as well as to compare the obtained data with the literature, which is currently missing completely in the results section.

2. Commercial sorbents were used in the work. It remains unknown, for what purpose their study was carried out on TEM, if these data in the work are not compared with the results of experiments. The particle size distribution is provided by the manufacturer.

3. The conclusion is too extensive in volume, it is necessary to shorten it and to mention the most important achievements.

4. References [16-24] are not properly discussed in the Introduction.

Author Response

Hello,

Thank you for your time to review and give feedbacks on our manuscript. Please see the attached file for our detailed responses to the comments.

Regards,

H. Doan

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The manuscript presented an investigation about the adsorption of La(III) using various adsorbents which apparently are cationic exchange resins.

-If the investigation was done using these type of compounds, strictly La(III) was not adsorbed onto the resin but exchanged with the counter-cation present in the resin: the title must be changed.

-Then, presumably protons are released into the aqueous solution as a consequence of La(III) loading onto the resin. Did the authors not any change in the initial pH along the experiments?. If so, How did they resolved this issue?.

-Also, egs.(3-4) and (5-6) do not corresponded to a first and second order, but to the pseudo-first and pseudo-second order, respectively.

-The most important: the elution (desorption) step was not investigated here, thus, we only have knowledge of just half the process. These elution data are as necessary to know as the metal uptake onto the resin ones. Als,o it will be welcomed a comment (or full data) about what to do with the La-eluted solution. Then the title: "an investigation of lanthanum recovery from an aqueous solution by adsorption (ion exchange)", will represent what is described in the manuscript.  

In the present form, the investigation was not complete, and I must reject the manuscript.  

   

Author Response

Hello,

Thank you for your time to review and give feedbacks on our manuscript. Please see the attached file for our detailed responses to the comments.

Regards,

H. Doan

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have done a good job of correcting the article, taking into account the questions and comments sent. This version of the article can be recommended for publication

Author Response

Please see the attached file for details.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors, unfortunaltely some of the explanations given by yours are not enough to accept the manuscript in the present form. Two main questions still are unresolved. 

1-Section 2.4. Th explanation given in the section about the influence of the pH on La(III) uptake onto the resin is unconvincent. Moreover, and according with the results presented in Fig. 6d, a shift of the pH towards more acidic values (as expected) is swon, and thus, in the influence of the pH on La upload (Fig. 6a) you must put in the x-axe, the pH values "at the equilibrium, if not, your results and discussion are under question. Your explanation about the device use in the experimentation must not be considered, if you need to measure the pH please use alternative devices. The presence of Na(I) ions in the solution must have a minor influence on La(III) uptake, since the order of uptake must be La(III)>>>Na(I). 

-Accordingly with it was written above, in all the figures, explantion of results, etc., authors must consider to relate their results to the equilibrium pH. Also, an equation showing the La(III)  upload equilibrium onto the resin must be given.

-Section 2.5. In this acidic eluted solutions and with these low La(III) concentrations in these solutions, how do you pretend recover La(III) as end product?. Do you think that on your solutiona any of the techniques (lines 645-647) are applicable?

-I think that Section 2.5. is not the most appropriate location to discuss Table 3 and the associate comments.  

Author Response

Please see the attached file for details.

Author Response File: Author Response.pdf

Round 3

Reviewer 2 Report

Comments and Suggestions for Authors

Authors responded in a proper manner to the queries, however, the chemical equilibrium equation explaining the metal upload onto the resin is still absent in the manuscript (eq.(14) does not represent that chemical reaction), please included it..

Author Response

Hello,

Please see the attached file for details.

Regards,

Huu Doan

Author Response File: Author Response.pdf

Round 4

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors, in line (596) the equation must be numbered, also in this equation a number 3 (coefficient) must appear before RH in the left side of the equilibrium to fulfil stochiometries.