Processing of Metal Waste—Sludge from the Galvanizing Plants
, Hana Rigoulet 1, Silvie Brožová 1, Jitka Malcharcziková 1, Šárka Langová 1, Jiřina Vontorová 1, Václav Nétek 2, Jaroslav Kubáč 3 and Dominik Janáček 4Round 1
Reviewer 1 Report
Comments for author File: 
Comments.pdf
Author Response
Reviewer: In the present study, the authors present the applicable hydrometallurgical processing of sludge from galvanizing plants. They revealed that the alkaline leaching much better than acid leaching in this case since the existence of Fe will affect the leaching efficiency. The authors have done many works, but the paper is not well-organized, the following issues need to be addressed.
In accordance with the legislation of the European Union the goal of the entire project was to find ways for a waste-free economy, a maximum use of secondary raw materials and, if possible, a closed cycle for the processing of galvanic sludge, which belongs to the category of hazardous waste. At the same time, a relatively high zinc content primarily gives a chance for obtaining from a "rich source".
- The authors have done a good job in the literature review. However, as a research article, the introduction part is too long. Please shorten it to highlight the key points. Most importantly, the introduction part has to present the innovation of research, but I cannot see any related statement in Introduction.
We do not consider the introductory part (Chapter 1) too extensive. Before the actual experiments, it was necessary to carry out extensive research regarding the given issue - zinc recycling from galvanic sludge. Most of these researches were related to the extraction of zinc and other metals (eg. Mn) from different types of wastes on a laboratory scale. The industrial implementation of the proposed technologies is missing for the time being. Our goal was to find as simple as possible separation procedures to obtain zinc of the highest possible purity, which we finally succeeded. The reason for this article is to inform readers about the associated problems. Galvanic sludge processing by leaching in a hydroxide environment is not used practically, which we consider an innovative element of our research. The achieved results testify to the fact that our path was the right one.
- The organization of content in this manuscript is too messy. Please check your submitted version.
Yes, we agree. During the conversion of our original document, some objects in the images were separated during editing, resulting in chaotic legends for units and text. Corrected in the revised manuscript.
- It is hard to understand the results of XRD pattern in Fig.3 since the line is too hard to tell.
Yes, we agree. Our X-ray diffractometer provides an output in the format shown. Figure 3 is replaced by an X-ray diffractogram of another sample.
- The whole paper is about processing experiments. The authors should do more tests to reveal the effects of Fe during the recovery of zinc from galvanizing sludge waste.
In our experiments, of course, tests were carried out to obtain Fe. The results were diverse, as Fe separation is sensitive to precipitation conditions and, at the same time, other metals are separated at the selected pH, which would lead to further refining processes and thus to an increase in the consumption of chemicals. Economic reasons prevent us from dealing with this issue. In the future, we are considering the use of leaching residues containing Fe and other compounds in the field of civil engineering.
Author Response File: Author Response.pdf
Reviewer 2 Report
Where do the points Ad 1, Ad 2, and Ad 3 come from?
Table 2. Average Mn 0,10?
Table 2. Table 6. Average. Does that make sense?
Table 3. Confusing table title
Figure 8. Are the signatures confused?
References [39, 40] Isn't that a self-promotion? I have my doubts
Author Response
Open Review
Comments and Suggestions for Authors
Where do the points Ad 1, Ad 2, and Ad 3 come from?
Details on points Ad 1, Ad 2 and Ad 3 are added in the text.
Table 2. Average Mn 0,10? Table 2. Table 6. Average. Doesthat make sense?
Table 2. The line marked "Average" has been removed due to the significant variance of some elements from individual suppliers, which relates to the technology they use.
Table 3. Confusing table title
The table name has been modified.
Figure 8. Are the signatures confused?
We apologize, the mistake occurred when exporting our original text in the editorial office. Legends have been edited and inserted directly into the images.
References [39, 40] isn't that a self-promotion? I have my doubts
In these two quotes [39, 40], we refer to our earlier experiments that were carried out in the 1st stage of the project (2021). In no case this is self-promotion. Other results presented in tables and figures are our own, authentic and original.
Author Response File: Author Response.pdf
Reviewer 3 Report
I have some remarks, respectively recommendations (according to consideration of the author):
In introduction:
In Reference “7” (Havlík, T. et all. : Hydrometallurgical treatment of used printed circuit boards after thermal treatment. ) is as a waste for leaching was used discarded printed circuit boards. It is completely different material and its behaviour during leaching is different as a sludge.
2. Materials and Methods
Table.2 Page 7: In text, In sentence ……..manganese content found out in one company, which relates to the manufacturing technology and this value was not included into the statistical calculation”. Average is not enough for statistic calculation!
Why did you decided to use for leaching these three kinds of acids: sulfuric acid, nitric acid and hydrochloric acid? I miss the bedground like thermodynamic study (use software HSC Chemistry , or make some chemical reactions, delta G , atc. )
Please answer the question? You used for leaching as and oxidative agent Hydrogen peroxide H2O2 or ozone O3 . What type of ozone equipment was used for experiment? What was the oxygen flow rate per minute? What was concentrate of H2O2 in experiment?
3. Results
Page 8: Figure 2. Description of figure 3 is better to put in the text. What sludge 1, 2, .. or D20, D21 ?
Page 9: Figure 3. What does it mean “Galvanicky kal” written in the picture
Page 15: Figure 6: Description on “photo documentation” is needed!
Page 17: Figure 7: Description on the picture Segregated zinc is needed!
Page 19: Figure 8: Description on “photo gallery” is needed!
Page 20: Figure 9: What does it mean ” čas odběru” written in the picture.
Page 22: Figure 10: It need to be description of a photo documentation of the electrolysis process.
There is no leaching theory in the manuscript and there is no background like a thermodynamic leaching study.
There is no scientific analysis of the product confirmation (solid residues, precipitate), such as SEM-EDX analysis or XRF analysis, in each part of an experiment, such as leaching, precipitation and electrolysis. There is only a visual photographic documentation.
Author Response
Comments and SuggestionsforAuthors
I have some remarks, respectively recommendations (according to consideration of the author):
In introduction:
In Reference “7” (Havlík, T. et all. : Hydrometallurgical treatment of used printed circuit boards after thermal treatment. ) is as a waste for leaching was used discarded printed circuit boards. It is completely different material and its behaviour during leaching is different as a sludge.
A change of literature No. 7, where the thermodynamics of hydrometallurgical processes is also addressed, among other things.
- Materials and Methods
Table.2 Page 7: In text, In sentence ……..manganese content found out in one company, which relates to the manufacturing technology and this value was not included into the statistical calculation”. Average is not enough for statistic calculation!
Given the variances in the concentration values of some elements in galvanic sludges, it is not appropriate to state average values. The corresponding line (Average) has been deleted.
Why did you decided to use for leaching these three kinds of acids: sulfuric acid, nitric acid and hydrochloric acid? I miss the bedground like thermodynamic study (use software HSC Chemistry, or make some chemical reactions, delta G , atc. )
The composition of galvanic sludges of individual producers is quite different. The proposed acid leaching procedures were based on the extensive literature research (see chapter 1. Introduction), where the final operation is electrolysis. The electrolysis of sulfate solutions with a high zinc content is usually used. Therefore, in the first stage we searched for the optimal leaching solution and conditions for the separation of zinc from the sludge. Due to the multi-component composition of the sludge (7 or more metals and other inorganic compounds determined by X-ray diffraction analysis), it was not possible to determine in advance which method of leaching would be suitable. Among others, Havlík [7], Formánek [24] and other authors dealt with the thermodynamics of hydrometallurgical processes of waste and ore processing. This information was accepted in our experiments.
Please answer the question? You used for leaching as and oxidative agent Hydrogen peroxide H2O2 or ozone O3 . What type of ozone equipment was used for experiment? What was the oxygen flow rate per minute? What was concentrate of H2O2 in experiment?
30% H2O2 was used as an oxidizing agent during leaching and precipitation. Ozone was produced in concentration 140 mg/l, and a volume of feed gas was 8 l/min (Korona L20 SPALAB generator). Added in the text.
- Results
Page 8: Figure 2. Description of figure 3 is better to put in the text. What sludge 1, 2, .. or D20, D21 ?
Agreed, corrected in the text. The designation for sludge: D is the supplier's designation, the number indicates the year of delivery of the sample, e.g. D20 indicates the year 2020.
Page 9: Figure 3. What does it mean “Galvanicky kal” written in the picture
Corrected.
Page 15: Figure 6: Description on “photo documentation” is needed!
We agree, corrected in the text and Fig. 6. In Fig. 6, the appearance of cathode zinc with dendritic formations after the electrolysis has been documented.
Page 17: Figure 7: Description on the picture Segregated zinc is needed!
Agreed, corrected in the text.
Page 19: Figure 8: Description on “photo gallery” is needed!
Agreed, corrected in Fig. 8.
Page 20: Figure 9: What does it mean ”časodběru” written in the picture.
Our mistake.Corrected in Fig. 9.
Page 22: Figure 10: It need to be description of a photo documentation of the electrolysis process.
The text under Fig. 10 has been edited and the information in the text has been supplemented.
There is no leaching theory in the manuscript and there is no background like a thermodynamic leaching study.
The theory of leaching from the point of view of thermodynamics is the subject of many works. In our case, information can be found in the cited literature [7, 24] and others. However, this was not the aim of the presented article. Due to the complicated system of sludge leaching with a variable content of many metal elements and their compounds, no theory is able to solve this problem objectively. Therefore, we consider an extensive experimental activity to be the only option in this case.
There is no scientific analysis of the product confirmation (solid residues, precipitate), such as SEM-EDX analysis or XRF analysis, in each part of an experiment, such as leaching, precipitation and electrolysis. There is only a visual photographic documentation.
All our analyzes were based on real samples and intermediates obtained during hydrometallurgical processing. Samples were taken from the input galvanic sludge, leaches, leaching residues, filtrates, electrolyte and cathode Zn, for which the AAS and ED-XRF analyzes used in our experiments are usually sufficient. Both the methods give representative results after individual operations. SEM/EDX type analysis is of course possible, but in this case we considered it unnecessary due to the need to obtain results operatively. In the final phase of the project, an analysis of the final cathode zinc is planned in terms of purity, size and morphology of the obtained product. The attached photos of individual products are of a documentation nature.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The authors should add response to reviewers' comment in their manuscript, ohterwise how can the reviewers understand which part has been revised?
Author Response
See attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Thank you for your approval of my suggestions intended to correct your manuscript. However, I still have comments.
The information in the pictures has not been marked and described. The description of the pictures under the photo is not sufficient.
The author insists that the results presented in the manuscript are operative, and that the scientific confirmation of the results will be given only after the project is completed. Confirmation of scientific research must be proven by appropriate quantitative and qualitative methods. In my opinion, only visual confirmation of the result with pictures is not enough for the manuscript to be published. Also, for this reason, I cannot agree to the publication of the manuscript in such a final form. The manuscript in such an informative form, as the authors themselves stated, can be published in Q4 journals.
Author Response
See attachment
Author Response File: Author Response.pdf
Round 3
Reviewer 1 Report
Here is the comment for this manuscript: Accept in present form.
Reviewer 3 Report
By adding supplementary information through quantitative analysis of the final product (cemented Zn), the quality of the manuscript was improved.
In Fig. 11 shows only the SEM analysis, but not the EDX analysis.
The results of the mentioned research can be beneficial from a practical point of view.
