Characterization of Magnetic and Mineralogical Properties of Slag Particles from WEEE Processing

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Abstract:

The abstract is really well written, and the author addresses the research objective and methodology well.  

1. Introduction:

            The manuscript in this study was very well written, and especially the author wrote a clear direction of how this study is going to do. However, the author should briefly give the reader an overview about processing method. For example, there are 3 methods (mechanical, pyrometallurgy, and hydrometallurgy) that were and are being used, and it would be better to have brief explanation on that each process about how it works before making a mention on metallurgy in line 48. In line71, the author should provide on how the magnetic process can separate particles different sizes because it confused to the reader (isn’t particle size separated by sieve or it can be separated by magnetic process also by applied different magnetic field intensity). In line 81-83, a diagram or figure of basic gravitational force should be provided to enhance reader comprehension.

2. Materials and Methods

The materials and methods are well written. But there are some parts you need to approve. Firstly, even though the workflow is clear, line 146 (these size classes) is a bit confusion because it is not sure if these size classes are the size after or before milling. For example, please just add after size classification (size classes after size classification). Secondly, full words should be provided in descriptive sentences for better comprehension to the reader in line 173 and 175 (F_g:  Gravity force, F_m: magnetic force). Thirdly in line 203, please check the cross reference to figure again (figure 2-B or Figure 3-B which between these figures are u referring to?). Fourth in line 203 and 206, the numbers (1), (2) and (3) should be followed by figure 3 to let the reader know that you are talking about figure 3. Fifth in line 228, M.H curve should be provided in full form or explain what it means. Lastly, Why Ring-type magnetic separator weren’t included in the workflow? As subsection 2.2.2. Ring-type magnetic separator were described after subsection 2.2.1. Frantz isodynamic. Based on your result, it is quite confusing to the reader again if Ring-type magnetic separator was conducted before Frantz isodynamic separator or the author conducted these two methods and made a comparison between these two methods as in subsection 3.4. Magnetic Separation. 

In addition, Figure 1 is not clearly present. Because the authors use more color to represent the magnetic susceptibility, it is better for the reader if the author provides the legend of color meaning in Figure1.

3. Results and Discussion

            The manuscript in this section was not very well written and explanation. Firstly in line 266-267, why the result in Figure 4-A are the calibration curves of the Frantz isodynamic separator at 10° and 15° respectively meanwhile you mentioned the sideward slope angle was kept at 15° for all measurements in line 187-188 (it is quit confuse for the reader because the reader will make assumption based on materials and methods even though it is from literature, so please mention 10° and 15° of the sideward slope angle were conducted to subsection 2.2.1. Frantz isodynamic in materials and methods). In contrast, if the 10° and 15° were referring to calibration curves, please make it clear with the sideward slope angle. Secondly in line 290, full form of X_g should be provided (X_g: distribution of susceptibility classes or measured magnetic susceptibility?) This will enhance reader comprehension to the result in as only symbol not full form are in X and Y-axis. In line 384 figure 7, it is almost impossible to distinguish between colors in the graph from Amp0.5 to Amp1.6.

4. Conclusions

            The manuscript in this section was well written, and it covered all the main objects in this study.

Other Concerns

·       Please replace all word of "Susceptibility" with "Magnetic susceptibility"

·       Line 153: it would be much better if the author just adds the word pre-treatment to Frantz   isodynamic separator to the workflow. For example (Pre-treatment: Frantz isodynamic separator)   

·       Line 169: Citation [25] should be sited at the end of the sentence.

·       In line 198 figure 2: (A) and (B) should be not provided at the end of its caption and please check figure 4 too. It should be changed to: Figure 2. (A)The working principle of Frantz Iso-dynamic separator; (B) workflow to create susceptibility classes using a Frantz isodynamic separator. Please change on other figures too

·       In line 221: Figure 3 should be in central alignment to the text. Please check and change the other figures too.

·       Below the line 240 equation 6: (Ferro?  

·       In line 295-296: Figure 4 should be in alignment to the text, and its caption should align to the figure.   

·       In line 317, 0.7? it should be 0.7 A.

 

·       In line 505-516: Number 2 and 3 must be aligned with number 1. 

Author Response

Dear Reviewer,

Thank you very much for your valuable feedback and suggestions, it helped to improve the manuscript. The attached Word file contains detailed point-by-point responses to each comment/suggestion. 

Kind regards,

Asim Siddique on behalf of all authors

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The submitted manuscript describe studies on relations between magnetic properties and mineralogical composition of different fractions of slag produced during WEEE processing.  Authors carried out a multi-step separation of ground slag into grain size fractions, and then the fractions were splitted using magnetic separation. For magnetic separation Frantz isodynamic  separator and ring-type magnetic separator were used.

The WEEE is a secondary raw material in production of copper, silver and other metals of strategic importance. Current technologies of WEEE processing base on pyrometallurgical processing. As the recovery ratio for copper and silver is usually very high, the slags are relatively poor in this metals.  However, growing market demand for non-ferrous metals results in  searching for methods of recovering metals even from poor raw materials. It is reasonable and obvious to start their processing with separation techniques, allow for production of enriched fractions. The article is an approach to definition of basic rules and relations in such separation techniques in mineralogical approach. Moreover, the studies are continuation of assessment of recyclability possibilities for the slag carried out by prof. Friedrich group in 2020, where the slag was produced. The introduction section is complete, and generally all used techniques are described in details. The idea of studies and their realization are proper and  in agreement with high standards.

Thus, in my opinion it’s an interesting way for more effective recovery of metals from WEEE and the studies will be interesting for journal readers and meets the requirements of the Minerals.  I recommend publication, however I hope that some short feedback and comments help to improve the high quality of paper (minor revision).

1.       WEEE slag is a type of abbreviation or colloquialism – it’s the slag from WEEE pyrometallurgical treatment. Maybe the “slag from WEEE processing” is more suitable terminology.

2.       As the slag is a main object of the paper, it should be clearly defined. Type of WEEE should be noted (printed circuit boards, wires, motors? In what ratio?) as well as the slag elemental composition. This information is important for readers.

3.       Abstract: in line 18 the “Waste Electrical and Electronic Equipment” occurs. Please add an abbreviation and use it in line 21.

4.       Line 170 – please remove the “Frantz isodynamic magnetic” – “the separator” is sufficient, as the full name is in line 169.

5.       Figure 2b and 3b are in general the same. Maybe one workflow for both will be sufficient.

6.       Fractions elemental composition is also important for assessment of possibilities of further recovery of metals. It should be noted in the paper or in supplementary data.

 

Author Response

Dear Reviewer,

Thank you very much for your valuable feedback and suggestions, it helped to improve the manuscript. The attached Word file contains detailed point-by-point responses to each comment/suggestion.  

Kind regards,

Asim Siddique on behalf of all authors

Author Response File: Author Response.pdf