Processing of Sulfide Copper-Nickel Ores from the Deposits in Murmansk Region by Heap Leaching

Round 1

Reviewer 1 Report

16: Fe3+, Fe2+, Ni, and Cu ions (the connecting word 'and was missing'). Is it possible to be specific on the types of Ni (Ni2+?) and Cu (Cu2+?) because you have already specified the ones for Fe

35: Changes are observed in the hydrochemistry of surface water, the chemical composition of bottom sediments and soils, along with the structural and functional organization of biotic communities

40: To minimize such negative environmental impacts, a technology needs to be developed to efficiently process low-grade ores and industrial waste  ('This' in my view addresses a noun)

42: Additional info; think of starting with the sentence below before giving advantages of bioleaching;

 

Bioleaching involving the use of microorganisms in leaching minerals is an evolving technology with important potentials to add value to the mining industries with the capacity to offer economic, social, and attractive environmental benefits to all the associates.

Reference:

Pradhan, N., Nathsarma, K. C., Rao, K. S., Sukla, L. B., & Mishra, B. K. (2008). Heap bioleaching of chalcopyrite: a review. Minerals Engineering, 21(5), 355-365.

 

43: That method is …

 

47: The process has been successfully

49: Basically, in heap leaching, the application of the metal extracting agents on the dumps is conducted to allow the dissolution of the minerals from the ore

(Thenepalli, T., Chilakala, R., Habte, L., Tuan, L. Q., & Kim, C. S. (2019). A brief note on the heap leaching technologies for the recovery of valuable metals. Sustainability, 11(12), 3347.

)

54: run year-round,

60: Sulfide copper-nickel ores from the Allarechensk technogenic deposit (hereinafter TD) and the Nud II deposit were used in this study.

 

In the sentence above the deposits appears to be two so we need to add and  as a connecting word

 

61 & 65: If possible TD and AD can be written in full to help the reader understand the different

67: The bulk of the ore in the Allarechensk TD is found in the size fraction  of 150+10 mm.

my question is:

Is it 150±10 mm or -150 to 10 mm? if that is the case then we can use the word ''range'' in place of fraction because if we say size of fraction of 150 +10 mm, then it is appropriate to just write 160 mm. Alternatively if it is -150 mm then the connecting word ''OF'' can be placed just before the value

68: There is need to have a consistent way of representing the elements in the overall article for instance choices can be made between nickel, copper, and cobalt  or Ni, Cu, Co formats

70: 'and' and % before and after Co-0.21 are  missing not unless 0.021 is not %. In my view it should appear as shown below

 

The average grades found in the rock dump were Ni – 1.57 %, Cu – 1.34 % and Со – 0.021 %, respectively.

77 & 78: The word both  appears to be misplaced because it does not address the previous/preceding sentence. May be we can state the deposits being referred to make the reader understand for instance,

 

Allarechensk TD  and Nud II deposits are characterized by the fact that both high-grade and run-of-mine ores support conventional concentration methods.

 

86: The values are not clear in my opinion. Is it (-5 +2 mm=-3 mm?) confirm if (-) is a negative sign in this context or hyphen which if it is the case then there is need to remove it to bring a more clear meaning.

86: We can write it as below:

The weight of the ore sample from the Allarechensk TD was 800 grams, while the one from the Nud II de- posit was 200 grams

94: Fe3+, Fe2+, Ni, and Cu ions. Also there is need to specify the types of the ions monitored for Ni and Cu.

95: Fe3+, and Fe2+. The items are two therefore use the connecting word and

99: Consider the use of examine or assess or analyze in place of ''judge''

101: use that in place of this. In my view the word this is suitable when referring to a noun in the previous sentence but in this case we just want to refer to an explanation in the preceding sentence.

108: powder X-ray diffraction technique/method.

we add the word technique to make it more specific though it does not bring any big difference but it might be good.

108: we can write this part us

 using DRON-2.0 instrument with Cu-Kα radiation source.

Corrected sentence:

The mineral composition of the primary and experimental samples was measured by powder X-ray diffraction technique using the DRON-2.0 instrument with Cu-Kα radiation source.

115 Consider writing as shown below to bring out a nice comparison

 

A higher content of chalcopyrite was observed in Nud II ore  compared to the Allarechensk TD ore

121: Magnetite is often found in combination with these as shown in figure 1a.

128: recorded (figure 2b). That

131: This part does not come out well. Do you mean?;

Visually, the ore particles are sintered, covered with a crust, probably of iron hydroxides, when they begin to peel off and crumble.

134: (a) (b). I think opening brackets are missing

137: replace the word from with and because it appears that Ni was recovered from Cu which is not the case in my view.

 

In the course of bioleaching experiments on the Allarechensk TD ore, 16.5% of nickel and 7.5% of copper was recovered after 80 days.

138: The maximum concentration of nickel in the solution was noted on the 22nd day of the experiment which amounted to 1557 mg/L, while the average concentration was  680 mg/L.

143: Lets specify the Ni and Cu ions (Ni 2+ and Cu 2+?)

145: the word to conclude does not modify well the subject matter.

consider to consider or to think? to focus?

150: (a) and (b) there is need to be consistent in numbering format

152: The pH value of the pregnant liquors varied during the experiment from 1.9 to 2.2,while the redox potential ranged from 471 to 582 mV

153: We can stick to Fe3+ for ferric ion and Fe2+ for ferrous ion because the two words are close and confusing to majority  of the readers

163: ...on 40th day which was equivalent to 1140 mg/L..

167: replace with was because we are addressing a past tense

168: replace by with at; consider the sentence below;

The leaching kinetics of non-ferrous metals from the Nud II ore is characterized by a decrease in recoveries at the middle of the experiment, followed by an increase in the concentrations.

175: Consider consistency we can stick to (to) instead of (-) while expressing the range;

 

The pH value of the pregnant liquors varied from 1.8 to 2.3, while the redox potential ranged from 488 to 608 mV.

 

178: Consider replacing it with the sentence below

The sulfur content in the solid phase decreased by 34.6%, which is three times higher than in the Allarechensk TD ore

 

185: Use “That” instead “This”

190: The main reason for the inhibition of the ore leaching process in the experiment can be attributed to particle sintering and clogging.

191: I think something is missing here because mixing has to be between two or more materials.

Do you mean?

Such problem can be solved by mixing the ore layers in order to improve its permeability.

 

Lets make it plural then?

193: The use of the heap leaching method makes it possible to process mineral feeds, for which no market demand exists currently. The recovery of such minerals allows acquisition of additional economic benefits with reduction of their negative impacts on the environment.

Author Response

Good afternoon. We are grateful to you for the detail study of our article and valuable corrections. This will definitely improve the quality of the article. In the file we send our responses to the comments made (please see the attachment). 

Best regards, authors. 

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors present a laboratory study of column bioleaching using tailings material from Cu-Ni-Co sulfide deposits.

The temperature of the experiment was not specified.  This is very important since the intention is to assess the viability of bioleaching in a cold environment.

A mass balance should be done.  It is not sufficient to only report the elemental composition of the ore before and after, as there are clearly mass changes to the ore, e.g. the content of SiO2 increased from 32.3 to 40.0% for the Nud II ore.  The authors report Ni and Cu recovery, but do not specify how it was calculated.

No comments were made on the flow rate through the column over time, despite mention of clogging, only the irrigation rate was specified.

Reporting the average concentration of Cu and Ni is not meaningful, since it would be expected to be high at the start of the test and decrease throughout the test as the ore particles are progressively leached.

It would be of interest to examine the ore by microscopy after the bioleaching test, to evaluate whether the leaching was inhibited due to passivation of the particles, which is a common issue in leaching of sulfide minerals, especially chalcopyrite.

The authors do not suggest any process for recovery of Cu, Ni and Co from the pregnant solution.  What are the available options, given the composition of the PLS (low pH, high Fe3+, low Cu and Ni).

Lines 114, 116, 128 - should the word "reflexes" be "reflections", in reference to X-ray reflections?

Author Response

Good afternoon. We are grateful to you for the detail study of our article and valuable corrections. This will definitely improve the quality of the article. In the file we send our responses to the comments made (please see the attachment). 

Best regards, authors. 

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Thank you for addressing the points raised in my review, particularly in the calculation of the metal recovery.  Please add charts to Figure 3 showing the recovery of Ni and Cu over time for each of the two ores.  This will allow readers to see if the recovery was still increasing or whether it had plateaued, as is common in heap leaching operations for sulfides.

Author Response

Fixed. We have added a charts showing the recovery of metals during the experiment.

Best regards, authors.