Effects of Silicic Acid on Leaching Behavior of Arsenic from Spent Calcium-Based Adsorbents with Arsenite
Round 1
Reviewer 1 Report
Manuscript Title: Effects of Silicic Acid on Leaching Behavior of Arsenic from Spent Calcium-based Adsorbents with Arsenite.
Manuscript Number: sustainability-1439278
In this work, As-leaching was investigated for spent Ca-based adsorbents (loaded with arsenite) in the presence of silicic acid. Different factors have been studied, including the aqueous forms of silicic acid, formation and role of calcium silicate species within the leaching process, and the stochiometric considerations on Ca-adsorbents. The manuscript is well organized, the writing is well-tailored, and results interpretation is often reasonable. However, the manuscript could be recommended for publication after a major revision following these next comments:
Comment #1: Abstract should be supported with more qualitative and quantitative findings.
Comment #2: Introduction section should be enhanced in terms of several aspects:
- More justification should be provided on the use of Mg-based/Ca-based adsorbents for As removal from contaminated water (i.e., is it only because of the low-cost and easy-operating features !!?).
- Page 2, lines 63-66, the sentences should be rephrased in a less confusing way.
- The main aim and novelty aspects of this study should be highlighted. This study has high similarity level to the author’s previous work, so it should be clarified what shall this study contribute to this aspect (shouldn’t be narrowed down to just considering As(III) instead of As(V)).
Comment #3: It is not clear whether the Ca-based adsorbents were experimentally synthesized or commercially purchased.
Comment #4: ‘’ion-exchanged water !!’’, does it mean deionized water?
Comment #5: Page 3, line 98, maybe ‘’synthetic’’ is better than ‘’artificial’’.
Comment #6: The used synthetic As-contaminated water had As(III) concentration of 20 mg/L? or As(V) 20 mg/L? It is no clear, still it is so important to be clarified because of the As(V)/As(III) aqueous transformations. Were As(III) and As(V) experiments conducted separately?
Comment #7: Page 3, lines 139-141, if this is the case here, then maybe it would be better to name it ‘’Si-normalized concentration’’ and unify it in the whole manuscript to avoid the confusion.
Comment #8: The As-leaching experiments were conducted for 24 hrs. Is there any time-corresponding data? It would be vital to observe the kinetics trend of the leaching process.
Comment #9: All equations in the manuscript should be supported with appropriate references whenever possible.
Comment #10: Page 7, lines 234-238, is there any reasonable attribution?
Comment #11: As-leaching rate should be related to the adsorption mechanism of As(V)/As(III) on Ca-based adsorbents (physical or chemical sorption), which thereby will govern the desorption trend. Such hypothesis should be considered in the discussion.
Comment #12: Simple characterization (e.g., XPS or XAFS) of the spent Ca-adsorbents before and after As-leaching could greatly help in understanding the leaching mechanism.
Comment #13: Conclusions should be supported with more quantitative results.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Effects of Silicic Acid on Leaching Behavior of Arsenic from Spent Calcium-based Adsorbents with Arsenite The paper is well presented, including research methodology and result discussion. This theme is quite important to be investigated as the groundwater pollution widely influences human activities and health conditions. Nevertheless, I write several comments to be followed up to increase the readability of this work. 1. It was mentioned that "There are numerous reports on groundwater contamination with As, which is a global problem. In recent years, it has become a major challenge in regions across Asia (such as Bangladesh [1-5], Pakistan [6,7], Iran [8], India [9-11], Sri Lanka [12], Vietnam [13,14], Cambodia [15], and China [16-18]), Latin America (such as Argentina [19,20], Uruguay [21], and Mexico [22,23]) and West and South Africa [24,25]. ". Make a chart or table to provide statistical data based on references in this statement. 2. Introduction was supposed to be concise in terms of references number (I spotted around 40 references just in Introduction. Authors are recommended to compose a "Literature Review" to accommodate a large number of references so that description and explanation of these references can be more clearer. 3. Characteristic of Spent Ca-based adsorbents needs to be reclarified in this work even though it was put in your team publication. 4. Make sure all components/compounds to be clarified. Where is it bought? Company name, city, country have to be clarified. If applicable, the purity of components/compounds may be presented as well. 5. Graph style may be reconsidered. If the legend of a graph is put outside the graph (see Figure 8 for example), then other graphs should follow this style. 6. Recheck reference format. Why was reference no.5 given DOI number, and the others were not? The page number can be replaced by article number, for example, 110318 for article no. 5.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The authors have exerted great effort revising the manuscript, which enhanced its overall quality. Hence, I recommend this manuscript to be accepted in the present form.
Author Response
Dear Reviewer 1
Thank you for reading the revised manuscript and accepting it.
In response to a suggestion from the editor, I submitted the final version of the manuscript, which was proofread in English again.
Sincerely, Hajime Sugita
Author Response File: Author Response.pdf
