Hydrometallurgical Process for Zinc Recovery from C.Z.O. Generated by the Steelmaking Industry with Ammonia–Ammonium Chloride Solution
Round 1
Reviewer 1 Report
The study is an interesting “technical” proof-of-concept application of a simple flowsheet for the recovery of high purity zinc from a steelmaking dust. While the study contains well known steps, the authors demonstrate they have thought about the important factors that enable EW quality zinc to be obtained. The topic that is not discussed, although highlighted to be a problem for conventional zinc sulfate EW, is the presence of chloride in the lixivium (liquor) that is used for electrowinning. While it is not important that this matter is solved by the current study, any information on this topic that may be useful for other researchers on the behaviour of the chloride would be useful.
The authors are provided with a marked up Word version of their manuscript with suggested wording changes and a range of other minor queries to address in revising this submission.
Comments for author File: 
Comments.pdf
Author Response
Thank you very much for your valuable advice.
The response of the comments is in the attach.
Author Response File: Author Response.pdf
Reviewer 2 Report
Line 2: Zinc
Graphical abstract: Waelz Process
Line 10: NH3-NH4Cl-H2O The numbers in subscript
Line 15-16: from the C.Z.O particles was very rapid This part of the sentence is repeated
Line 25:reference 2 is not adequate
Line 45: Zn2+ 2+ in superscript
Line 46: RX Wang. Etc would not be Wang et al.?
Line 47 The numbers in subscript
Line 47 SH Yang etc. would not be Wang et al.?
Line 52 bearing dust?
Equation (1) Is it wrong? On the left there is 16 Cl-, however on the right only 2 Cl-,
Equations 1,2,3,4 the superscripts and subscripts are not set
Fig 1. Waelz Process
Lines 60-65:
It is not explained how the chemical analysis was performed or what equipment has been used for DRX and SEM.
Lines 64-65：
Sentence "After leaching, the residue was .......... At 60ºC. " does not belong to 2.1. Material. It should be in 2.2
Line 75：500 mL of lixivium were heated
Would not it be better leachate?
Line 76-77：
It does not specify the materials, nor dimensions of the electrolytic cell. Neither is it referred to the electrodes, nor to the conditions in which electrolysis is performed.
Line 91-92：
The mineralogicaldata obtained from chemical phase analyses were presented in table 2.
This sentence can not be in this section, it should be in 3.3.
Table 2: TZinc instead of TZnic
I do not understand, the percentage of Zn extracted the authors say is 81% Zn. If before the leaching there is a total 49.22% Zn and after the leaching is 20.19% total Zn, the percentage of extraction does not reach 60%.
Fig 3. Figures are not clear.
Line 136-137: ……solution concentration and temperature were varied……..?
Figure 4: Y axis 0.75 until 0.87. ? would be 75 entil 97 is in%
In Figure 5 the same thing happens.
I do not understand:
In line 126, the authors say: The wrapping phenomenon was not happened.
However on line 140, the authors say: little of wrapping phenomenon and performance of reaction on the surface and inside (SEM)
Line 144 says
Figure 4. displays the effect of temperature on zinc extraction kinnetic. The mase of solid, volumenof solution and total ammonia concentration was kept constant at 20g, 1000mL and 7.5 mol/L.
In figure 5 line 162 it is said that the tests were carried out at 40 ° C , then the line corresponding to 40 ° C in figure 4 should be the same as the 7.5 mol/L of figure 5 and this is not the case in the work.
There are no references or justifications to the data obtained.
What is the reason to choose 40ºC if with higher temperatures higher extractions are obtained
What reason is there to choose 30 minutes of leaching if the equilibrium has not yet been reached?
Line 165: mol/L ml/g
liters sometimes go in capital letters and sometimes in lowercase letters
In the kinetic tests 1000 mL and 20 g are used, the ratio L / S = 50 (Figures 4 and 5).
however, much lower ratios of 4 -8 mL / g in batch experiment trials are used. I suppose, that high concentration of Zn in solution is needed to do to do electrolysis.
The L/ S effect is not justified
In figure 6. as the L/S ratio increases, the extraction increases. However in figure 5, the extraction after 30 min. at 40 ° C with an ammonium concentration of 7.5 mol/L and an L/S = 50 ratio is a little more than 80%, it does not reach 81%, however in Figure 6 under the same conditions but with an L/ S = 8 the extraction percentage is 82% more or less.
It is not justified why a L/ S = 6 ratio was chosen to study the effect of temperature, concentration and time, figures 7, 8 and 9.
It is not justified why the extraction increases with increasing ammonium concentration in solution and why it decreases from 7.5 mol/ L.
lines 185-186 It is said:
When the concentration of ammonium chloride was more than 5 mol/L crystals is easily formatted.
What composition do the crystals have? Does the amount of these crystals positively or negatively influence?
If figure 5 is compared with figure 7, it does not seem to agree with the values obtained from percentage of extraction of Zn for ammonium concentrations of 3 mol/L (fig.5> 76% Zn) and concentration close to 4 mol/L (fig 7<60% Zn).
In the kinetic tests figures 4 and 5, the percentage of extraction of Zn increases as time increases, although it does so more slowly after 30 min. However, in the study of time (figure 9) it seems that it reaches equilibrium after 30 minutes. The only difference in the experimental conditions in these tests is the L/ S ratio. How this behavior is justified.
Line 194: lixivium leachate?
In tables 3 and 4 The Zn concentration is expressed in mg/L?
It is too low a concentration to electrolysis.
3.5.2 Removal od Cu, Cd and Pb
C.Z.O. It has a small amount of Ni. It has not been determined if something dissolves during the leaching stage.
It seems that the purification tests of Cu, Cd and Pb as well as the electrolysis were carried out in triplicate. However, it is not specified if they were also made in triplicate or not in the leaching tests.
References
Line 240: separar world steel
Line 276: la referencia 19 el título del artículo está mal.
R.X. Wang, M.T. Tang, W. Liu. NH3-NH4Cl-H2O system for production o f electrolytic sinc. J. the chinese journal of process enggineering, 8,2008, 219-222.
Leaching of Low Grade Zinc Oxide Ore in NH3-NH4Cl-H2O System for Production of Electrolytic Zinc
WANG Rui-xiang;TANG Mo-tang;LIU Wei;YANG Sheng-hai;ZHAGN Wen-hai. The Chinese Journal of Process Engineering year 2008, Issue z1, Page 219-222
Author Response
Thank you very much for your valuable comments.
The response of comments is in the attach.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
There are many changes of form: English, iSubscriptss and superscripts, liters in capital letters, changes in Y axes, etc. Line 182 increasing missing the i.
However, there are no changes in the background, it is not explained why things happen, some results of the kinetic tests do not agree with the batch tests, there are not enough references, etc. Therefore, I confirm in rejecting this article for Metals. However, if you consider that is good enough for your Journal, I do not have any problem in publishing it.
Author Response
First of all, thank you very much for your comments.
Because I am not sure if I uploaded the wrong response report notes file. I uploaded another one. If my response is not what you said, please let me know. Thank you very much.
1: There are no changes in the background, there are not enough references.
Response 1: I am not quite sure which aspect you are referring to. If you are referring to point 1 and point 2 in the response report notes. The errors have been already explained in the response report notes and improved in the manuscript.
2: Some results of the kinetic tests do not agree with the batch tests
Response 2: I am not quite sure which figure or table you specifically refer to. If you are referring to point 9 , point 10 ,point 11 and point 12 in the response report notes. The errors have been already explained in the response report notes and improved in the manuscript.
3: It is not explained why things happen.
Response 3: I am not quite sure which aspect you are referring to. If you are referring to point 13, point 14 and point 15 in the response report notes.The errors have been already explained in the response report notes and improved in the manuscript.
