Recovery of Metals from Printed Circuit Boards by Gold-REC 1 Hydrometallurgical Process

Round 1

Reviewer 1 Report

See attached file

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Manuscript sustainability-2304989 is devoted to recovery of valuable metals from printed circuit boards. Scheme of Gold-REC 1 technology is cited and presented. The main aim of submitted paper is to present profitability analysis. Despite interesting subject, there are some questions that need to be addressed during revision stage.

Generally, not all costs presented in the paper are clearly justified. As each scientific research should be reproduceable, source for each price should be identifiable. Additional more detailed data may be provided as supplementary material.

Line 259 – Table 2 Additional table listing each individual piece of equipment and its price would give better background for the total cost of main equipment. What is the source of percentages in the table? If they are parameters according to e.g. [33] it should be highlighted in the table.

Line 273 - Share of each chemical in raw materials cost should be indicated. Total cost for raw materials does not provide whole view of the costs.

Line 279 - How many days a year is plant operating? Which value was selected for estimation of OPEX costs?

Line 282 – What is the source of annual labor cost?

Line 288 - For which year was evaluation done? Assumption of 3% in 2023 seems quite optimistic.

Line 290 – The source or basis for estimation of for each cost should be provided. Complex costs should be split into induvial costs, e.g., as a supplementary material.

Line 316 – Table 5 - What is the source of each item in the table as not everything is provided in the text, e.g., which unit prices for each product/metal were assumed. Which level of market price was assumed? Is the whole technological scheme including refining stage?

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Dear Author,

Thank you for submitting your paper to MDPI Sustainability Journal and contributing your work and knowledge in the advancement of the field. The paper is well written in terms of English style and grammar, few minor notations related to chemical formula superscript/subscript and units needs to be fixed (they are highlighted in the attached file). The hydrometallurgical process and results presented are in a systematic manner and well explained. The conclusion section needs to be slightly improved by adding a little more of hydrometallurgical findings as that is the overall theme of paper and economics is a secondary aspect to it.

More comments/suggestion/questions related to the table:

·         Table 1 shows the average composition of the metals from PCB material. It would be good to include a variability column showing how much variance is in the grade (composition) of metals as it can have a major impact on entire economic model.

·         Figure 1 Leaching stage 1: Solid residue yield to 2^nd stage leaching is not mentioned in paper. It is important as it relates on how much solid is being handled by second stage.

·         Section 2.2.2 – After line 119: mass of feed or feed rate of PCB should be provided.

·         There is very little information on how contaminants are impacting the separation performance. Iron, zinc, and aluminum are in range of 4~5%. Iron specifically is detrimental to Cu electroplating which drastically impacts the performance. 

·         Don’t know why references are numbered twice.

·         Reference #24, complete word recycling at the end of reference.

·         Reference #32 unable to find, link is broken.

Thank you

Comments for author File: Comments.pdf

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Most of the remarks addressed during the first review are included in revised version. Therefore, I recommed to accept the manuscript.

Author Response

Many thanks for your contribution aimed at increasing the quality of the paper.

Author Response File: Author Response.docx