Experimental Study on the Recovery of Arsenic and Iron from Arsenic–Iron Precipitate by Carbon Thermal Magnetization Reduction
Round 1
Reviewer 1 Report
Comment
1. Title
It should be modified. It is not a slag but a precipitate. Also iron and arsenic were recovered not in metallic form but in the form of Fe3O4 and As2O3.
2. under the conditions of roasting temperature was 650℃, coke powder…
It should be modified
3. This method is to add ferric salt into arsenic-containing wastewater to generate iron salt precipitation of arsenic, namely arsenic-iron slag,
This is a precipitate/residue, not a slag. Slag is a by-product of smelting (pyrometallurgical) ores and used metals.
4. Glass solidification method is to mix and melt arsenic iron slag with glass, and the arsenic-iron slag is solidified in the glass matrix. This method has the disadvantages of complicated preparation process and high running cost, and it is difficult to apply industrially.
Why it is difficult to mix the precipitate with ground glass (most of time recycled) and to melt it at 1000 oC?
4. Wet metallurgy method is based on the characteristic that arsenic is easily soluble in acid and alkali
The term is not wet metallurgy. It is “Hydrometallurgy”
5. Because it contained a lot of water, the factory used the method of filter pressing and roasting to dry the slag.
The term is not roasting. It is “drying” Roasting is a process of heating an ore to a high temperature in the presence of air. It is a step in the processing of certain ores. More specifically, roasting is often a metallurgical process involving gas–solid reactions at elevated temperatures with the goal of purifying the metal component(s).
6. The raw material of this experiment was the roasting and dried arsenic-iron slag of this factory
Particle size distribution of the raw materials should be known.
7. The chemical composition analysis of arsenic-iron slag was shown in table 1
The chemical composition of the precipitate probably comes from SEM/EDS analysis. Detailed analysis from XRF, or AAS is required.
8. The roasting slag at different temperatures was analyzed by X- ray diffraction, and the results were shown in Figure 5-b
SEM analysis would be very helpful.
9. At 500℃, the volatilization rate of arsenic is 60.31%, and the content of arsenic in slag is 14.19%.
How the Authors determine the above percentages?
10. It can be seen from figure 5-b: 1) With the increase of reaction temperature, FeAsO4 was gradually decomposed,
A DTA analysis until 1000 oC would be very helpful.
Author Response
Response to the reviewer’s comment
Dear reviewer，
First of all, thank you very much for your hard work and very professional review comments. These comments are of great significance to this article. Here is my reply to the review comments:
- Title
It should be modified. It is not a slag but a precipitate. Also iron and arsenic were recovered not in metallic form but in the form of Fe3O4 and As2O3.
Reply: Modified.
It is not a slag, we changed slag to precipitate in the whole manuscript.
- under the conditions of roasting temperature was 650℃, coke powder…
It should be modified
Reply: Modified.
under the conditions of roasting temperature was 650℃, coke powder addition was 25 wt.%, roasting time was 180min, and argon flow rate was 10 L/min.
modified to
under the experimental conditions of roasting temperature of 650℃, coke powder addition of 25 wt.%, roasting time of 180min, and argon flow rate of 10L/min.
- This method is to add ferric salt into arsenic-containing wastewater to generate iron salt precipitation of arsenic, namely arsenic-iron slag,
This is a precipitate/residue, not a slag. Slag is a by-product of smelting (pyrometallurgical) ores and used metals.
Reply: Modified.
It is not a slag, we changed slag to precipitate in the whole manuscript.
- Glass solidification method is to mix and melt arsenic iron slag with glass, and the arsenic-iron slag is solidified in the glass matrix. This method has the disadvantages of complicated preparation process and high running cost, and it is difficult to apply industrially.
Why it is difficult to mix the precipitate with ground glass (most of time recycled) and to melt it at 1000℃?
Reply: Glass solidification is mainly a solid waste solution that mixes industrial arsenic-containing precipitate with the components of relevant glass, and then seals the arsenic-containing waste precipitate in the glass body after high temperature melting (850℃~1300℃) and cooling. When the industrial waste arsenic slag is treated with glass matrix, the waste precipitate particles will be coated by the surrounding vitrified components, thus forming a compact protective film to prevent the arsenic element from leaching out. The treatment must go through high temperature melting process, Because the arsenic-containing compounds are volatile, the glass solidification method is mainly used in the treatment of low-volatile or non-volatile arsenic-containing industrial waste residue. The reason above is why it is difficult to mix the precipitate with ground glass.
- Wet metallurgy method is based on the characteristic that arsenic is easily soluble in acid and alkali
The term is not wet metallurgy. It is “Hydrometallurgy”
Reply: Modified.
Wet metallurgy method modified to Hydrometallurgy method.
- Because it contained a lot of water, the factory used the method of filter pressing and roasting to dry the slag.
The term is not roasting. It is “drying” Roasting is a process of heating an ore to a high temperature in the presence of air. It is a step in the processing of certain ores. More specifically, roasting is often a metallurgical process involving gas–solid reactions at elevated temperatures with the goal of purifying the metal component(s).
Reply: Modified.
It is not roasting, we changed roasting to dry to dried.
- The raw material of this experiment was the roasting and dried arsenic-iron slag of this factory
Particle size distribution of the raw materials should be known.
Reply: In this manuscript, we milled the raw materials to ≤0.15mm completely. The particle size are as follows: 0.074-0.15mm 87.5wt%，0.074-0.00874mm 12.5wt%
- The chemical composition analysis of arsenic-iron slag was shown in table 1
The chemical composition of the precipitate probably comes from SEM/EDS analysis. Detailed analysis from XRF, or AAS is required.
Reply: When the arsenic content was ≥1%, EDTA volumetric method was used for determination; when the arsenic content was < 1%, ICP-AES was used for determination. Other elements were determined by ICP-AES.The analysis method was mentioned in “2.3. Analysis and detection methods”.
- The roasting slag at different temperatures was analyzed by X- ray diffraction, and the results were shown in Figure 5-b
SEM analysis would be very helpful.
Reply: SEM analysis was very hopeful to the experiments. In this part, we did not make SEM analysis, in order to analyze the microscopic process, we did EPMA in part “ 3.5. Mechanism analysis of arsenic volatilization and iron magnetization”. And made a detailed analysis.
- At 500℃, the volatilization rate of arsenic is 60.31%, and the content of arsenic in slag is 14.19%.
How the Authors determine the above percentages?
Reply: In the experimental process, the roasting slag was analyzed, the methods were as follows: When the arsenic content was ≥1%, EDTA volumetric method was used for determination; when the arsenic content was < 1%, ICP-AES was used for determination.
And the volatilization rate of arsenic was calculated by formula (1).
xi=(m0×x0 - m1×x1)×100%/ m0×x0 (1)
In formula (1): xi was the volatilization rate of arsenic, wt.%; m0 was the weight of added arsenic iron precipitate, kg; x0 was arsenic content in arsenic iron precipitate, wt.%; m1 was the weight of arsenic-iron precipitate after reaction, kg; x1 was the content of arsenic in precipitate after reaction, wt.%.
- 10. It can be seen from figure 5-b: 1) With the increase of reaction temperature, FeAsO4 was gradually decomposed,
A DTA analysis until 1000 oC would be very helpful
Reply: A DTA analysis will help us to real the decomposition process of FeAsO4, it is very helpful. Because the analysis and testing unit is on holiday and we just have 7days to revise the manuscript, we are so sorry that we can not finish the DTA analysis, we will do that in future research.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript aimed the recovery of arsenic and iron from slag by thermal magnetization reduction. Arsenic was obtained by volatilization. The manuscript present novel results, but several English and formatting errors must be solved before acceptance.
- In the abstract, what compound has 99.91% of purity?
- Introduction: The second paragraph presents no citation. Why? In the beginning of the paragraph, the authors cited references from 7 to 17 in two lines. There is no reason for that.
- Figure 1: the XRD has peaks with too low intensity. Why? I recommend the authors to do a long analysis
- Chapter 2.4: the equations need corrections
- Figure 6a and Figure 6b should be different figures, for instance Figure 6 and Figure 7.
Author Response
Response to the reviewer’s comment
Dear reviewer，
First of all, thank you very much for your hard work and very professional review comments. These comments are of great significance to this article. Here is my reply to the review comments:
- In the abstract, what compound has 99.91% of purity?
Reply: It is As2O3 with a purity of 99.91.
2.Introduction: The second paragraph presents no citation. Why? In the beginning of the paragraph, the authors cited references from 7 to 17 in two lines. There is no reason for that.
Reply: It is not appropriate, we have modified. References from 7 to 17 corresponding paragraph part.
- Figure 1: the XRD has peaks with too low intensity. Why? I recommend the authors to do a long analysis
Reply: We made many tests and found that the peak strength of the raw material's XRD peaks were indeed weak. The reason may be that the crystallinity of FeAsO4 was not high, resulting in weak XRD peak strength. The content of CaO was very low, so the peak strength was low.
4.Chapter 2.4: the equations need corrections
Reply: All the equations have been checked and corrected.
- Figure 6a and Figure 6b should be different figures, for instance Figure 6 and Figure 7.
Reply: Modified. All the figures have renumbered.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The Authors have addressed all comments
Author Response
Cover letter for minor revision
Dear reviewer and editors,
In the minor-revised manuscript, we have made the changes as follows,
1) In abstract, “Arsenic-iron precipitate mixed with coke powder was roasted in a low temperature, arsenic was recovered in the form of As2O3 product and iron was recovered in the form of Fe3O4.” was added.
2) In introduction, we add more information about glass solidification method, pyrometallurgical method, hydrometallurgy method and pyrometallurgical-hydrometallurgy combined method.
3) In “3.5. Mechanism analysis of arsenic volatilization and iron magnetization”, more analysis was provided.
4) All the changes was colored in blue.
Best wishes to you, and wish you everything goes well!
Xuepeng Li, 19885196366
Reviewer 2 Report
The manuscript may be accepted in the present form.
Author Response
Cover letter for minor revision
Dear reviewer and editors,
In the minor-revised manuscript, we have made the changes as follows,
1) In abstract, “Arsenic-iron precipitate mixed with coke powder was roasted in a low temperature, arsenic was recovered in the form of As2O3 product and iron was recovered in the form of Fe3O4.” was added.
2) In introduction, we add more information about glass solidification method, pyrometallurgical method, hydrometallurgy method and pyrometallurgical-hydrometallurgy combined method.
3) In “3.5. Mechanism analysis of arsenic volatilization and iron magnetization”, more analysis was provided.
4) All the changes was colored in blue.
Best wishes to you, and wish you everything goes well!
Xuepeng Li, 19885196366
Author Response File: Author Response.pdf
