Synthesis of a Novel Adsorbent Based on Chitosan Magnetite Nanoparticles for the High Sorption of Cr (VI) Ions: A Study of Photocatalysis and Recovery on Tannery Effluents
, Gehan El-Habibi 4, Adel A.-H. Abdel-Rahman 4,*, Hamed I. Mira 3, Yuezhou Wei 2,5,*, Saad H. Alotaibi 6, Hamada H. Amer 6, Adel E.-S. Goda 7 and Nora A. Hamad 4Round 1
Reviewer 1 Report
The manuscript by Zahra et al. deals with the synthesis of functionalized chitosan nanoparticles and their use in the adsorption of Cr(VI) ions from water solution. The modification with magnetite, already reported in previous works by the same authors, is coupled here with grafting of TDPD. The sorption data show good performances and an extended modeling is presented. Nonetheless, the insufficient discussion of the results and some important issues make the publication on Catalysts not recommendable.
1. Sorption experiments are performed under visible and UV light, showing that UV irradiation enhances Cr(VI) uptake compared to visible light. However, there is no explanation on the role of light on these performances, i.e. by which mechanism light favors the adsorption. Although it is known that deposition or sorption of metal ions can be influenced by light, some discussion about this aspect is necessary as motivation of the approach and interpretation of the results. Moreover, there are no control experiments in the dark, which prevents any conclusion on the possible effect of visible light.
2. The title mentions “photocatalysis”, however no evidence of reduction of Cr(VI) to Cr(III) or other species is given, as the concentration decay is related only with sorption. Since adsorption/desorption processes are concerned rather catalytic processes, the manuscript might be more suitable for a different journal.
Additional considerations:
3. Introduction: an explanation of the aim and novelty of this work in the context of the literature is missing.
4. Page, 3, line 123-125: “As Cr(VI) sorbed, most of these peaks are shifted and decreasing their intensities specially for NH, C=O, OH, C=S and SH (with expected tautomerization)”. The expected interaction between Cr(VI) ions and the functionalized biopolymer should be better described, since it is the core mechanism of the work.
5. Page 5, lines 154-156: pore volumes of 6.8 and 8.2 cm3/g are reported. These values are very high compared to those usually found for chitosan and other porous polymers. If these values are correct, the origin and type of the high porosity should be commented. In any case, nitrogen adsorption/desorption isotherm should be shown.
6. Experimental, sorption studies: for processes carried out under illumination more details about the experimental setup are needed, such as source of UV and visible light, intensity, distance from the reactor, and so on.
7. 94 references seem an excessive number for this manuscript and could be decreased.
8. Careful language editing is needed.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
1. When an abbreviation appeared for the first time in the text, the full name should be indicated, that is, the meaning of the abbreviation. E.g., TDPD and MC-TDPD in Line 105, MCH in Line 145. Or could advance the Materials and methods in Line 315 to the front of the manuscript as part 2.
2. The four figures in Figure 1 should be numbered separately and clearly written in the legend. Line 151-152.
3. There are two Figure 1 in this manuscript (Line 152 and Line 201), and maybe Table 3 in Line 227 should be Table 2. So, the numbering needs to be adjusted in turn. Please check the numbering of the full manuscript.
4. Table 3 in Line 228, the parameter of Visible light, maybe should be 1 2 3, and you have labeled as 1 2 1, please check and correct.
5. It's suggested that the mechanism of Metal desorption (2.2.4) be discussed in depth. The literature below was referred for further analysis and discussion.
Facile Synthesis of Magnetic Biochar Derived from Burley Tobacco Stems towards Enhanced Cr (VI) Removal: Performance and Mechanism.
6. Whether considered the removal of the material after application, i.e., how to prevent secondary pollution when applied for the tannery wastewater?
7. The logic in the manuscript was a bit confusing and the writing was not clear enough, and further revisions and adjustments to the manuscript are suggested.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
accept
