Reuse of Acid Bioleachate in Bacterial Oxidation of a Refractory Gold Sulfide Concentrate

Round 1

Reviewer 1 Report

1. minor spell check required. Eg. Line 17 "our results showed." Line 19,"bioleachate had a positive" Line 106 "subsequent step"

 

2.Material and methods.

 

(1) line 90。 The period of pre-oxidation? Also， how long for bioleaching 1 and bioleaching2 treat sulfide?

 

(2) In the whole work, several pH were illustrated in different part. The initial pH is 1.6  in Line 94,  line 117, pH is 1.7, Line 174, " you mean the initial pH is 1.6. decrease to 1.7?" Line 227,"in Table 2, a decrease in the pH value in Bioleachate 2 and Bioleachate 3 was also noticed," From 1.6 to 1.7 or 1.6 to 1.67, the changes is not obvious. The description is little confusing. Also, In line 190, the different pH on iron removal, this test process need to be added in 2.4.

 

(3) In conclusion part,  Line 372, "Nitrogen and phosphorus are the only two nutrients", However, in the material and method part, the adding nutrition are not demonstrated. Also in Fig.1, partial nutrition but not all the chemical reagents are added in Bioleaching treatment.

 

(4) Line 127. The pore size of a Whatman G6 fiberglass?

 

3.Results and Discussion

（1）Line 223， “The addition of 5% bacterial inoculation at each reuse may increase the quantity of 223 microorganisms present in the bioleach" Any proof to support this conclusion? It seems that, the possible reason explained in present work is the bacterial inoculation increased for all metal solutions. The proof is insufficient.

 (2) In Fig.4, Pay attention to the legend of bioleaching 3. is long dash but not solid line.

4. Conclusion

(1) Line 337. What kinds of chemical reagent are saved?

(4) Have you analyzed the total cost by reusing bioleaching solution. Only save partial chemical reagent ,but need using NaOH to precipitate metals. Furthermore, how to treat the Metal precipitate?

 

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

This paper discussed the reuse of biooxidation processing solution to reduce water demand and chemical reagent consumption in the refractory gold biooxidation. It is an interesting study in the field of biohydrometallurgy. However, there are some questions to be addressed.

1.      The term bioleaching vs. biooxidation: bioleaching refers to biohydrometallurgy of base metals, whereas biooxidation is the pretreatment for refractory gold ores. Please choose the proper term in the text as well as in Figure 1.

2.      Page 5, line 167-168: please indicate the exact percentage of each mineral from XRD analysis. Is there any evidence to support that this gold ore is refractory?

3.      Page 6, Table 2: Please indicate ORP with respect to the Ag/AgCl reference electrode or SHE. Is the bacterial activity affected during precipitation? Any method to recover base metals like copper and zinc from the solution? The economic value of base metal recovery is higher than simply recycling recycle the solution. 

 

4.      Page 8, Figure 3: How is the zinc recovery calculated? Based on Figure 1, new sulfide concentrate was used in bioleaching 2 and 3, please recalculate the mass balance.

5.      Page 10, section 3.5: Is there any analysis on the precipitate to confirm it is mainly jarosite?

6.      Page 10, Table 3: Adding analytical methods of NH4-N and PO4-P is recommended.  

7.      Page 11, Figure 5: How is gold recovery by direct cyanidation without bacterial oxidation?

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

After revision， the logic and illustration of the whole manuscript are improved. Minor revision needs to be made before acceptance.

1. Line 91, change "30 °C ± 2 °C" to "30± 2 °C";

2.Line 177, change to" 2.6. Sample analysis"

3.Add the facility model used in the present work.Eg, XRD, ICP-AES

4.Line 202-203.  XRD results not show here. Advise adding (data not shown here).

Author Response

See the attached file.

Author Response File: Author Response.docx

Reviewer 2 Report

 

1.      The order of Figures 1 and 2 is confusing. I would recommend using Figure 1 as the flowsheet and Figure 2 as iron precipitation. The part should be better organized and double checked. In Page 4, line 137: Figure 2 or 1? In Page 3, line 98: Figure 1 or 2?

2.      Page 10, Figure 3: Metal solubilization calculation is still not addressed. Or a discussion on metal concentration instead of solubilization is recommended.

3.      How is Figure 4 revised? It is not clear from the revision.

4.      There is no reason to change the title of cited articles in references.

 

Author Response

See the attached file.

Author Response File: Author Response.docx