Utilization of Sodium Hexametaphosphate for Separating Scheelite from Calcite and Fluorite Using an Anionic–Nonionic Collector
Round 1
Reviewer 1 Report
The manuscript presents results of flotation tests to study the effect of sodium hexametaphosphate (SHMP) as a depressant of calcite and fluorite in the process of flotation of scheelite with an anionic-nonionic assembled collector (sodium oleate and oleamide with a mole ratio of 2:1). The reviewer thinks the paper has to be rejected based on the following comments:
General comments:
-The discussion on the mechanisms is poor. In lines 145-146 the authors mention that “The significant differences of flotation performance manifest that SHMP exerts a preeminent ability to depress calcite and fluorite, while has no effect on scheelite.” However, no proper explanation is found in the manuscript. In Lines 153-154 the authors say “The results testify that SHMP can effectively enhance the enrichment of scheelite in the flotation of mixed minerals with an appropriate dose.” However, pure scheelite has a grade of around 80% WO3, but Fig 5 shows that in the mixed mineral system the grade reaches at maximum of 32%. Is this a good way of concentrating this type of minerals?No explanation is given related to this. There are also no results at 0 mol/L of SHMP, how are the recovery and grade at this condition?
- The results shown in Figure 5 indicate that recovery drops very quick above 3x10-6 mol/L of SHMP, however, the authors do not say anything about what is happening with calcite and fluorite, do they float?
-The authors indicate that “The FTIR analysis results prove that SHMP is likely to be adsorbed on the surfaces of scheelite, calcite, and fluorite via electrostatic force, while the assembled collector is adsorbed on these minerals surfaces by chemical adsorption.” It is hard to conclude this only from the FTIR data. No analysis of the surface charges of the three mineral species is given in the manuscript.
-The authors indicate that “In contrast, SHMP is more likely to be adsorbed on the surfaces of calcite and fluorite through electrostatic force, thus occupying the active sites and impeding the further adsorption of assembled collector.” It is not easy to get to this conclusion without zeta potential measurements. The iep of calcite and fluorite should be close to pH 9-10, the pH at which the flotation tests were done. So, it is hard to argue any electrostatic interaction between the SHMP type species and the surfaces of calcite and fluorite. More work is needed on this subject.
Specific comments:
Intro and conclusions are too long
Line 31: change “It is supplied in China” by “It is supplied by China”
English grammar must be improved; examples of this are in Lines 31-33, 129-132, 140, and 177-178.
Line 54: it says “sueface” should be “surface”
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This is an interesting paper on using the combination of reagents to facilitate flotation of scheelite from the ore containing calcite and fluorite. This papers shown how one can navigate using different technologies to confirm the underlying processes in adsorption of collectors and depressants. The main concern is the English in this paper. The paper needs to be edited by technical English writer or editor. There are a lot of grammatical mistakes and some of the words used in the manuscript are not well suited. There are also words that need to be rephrased as they do not make sense.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Reviewer comments:
The paper reports a set of laboratory experiments for the study of “Utilisation of sodium hexametaphosphate for the separation of scheelite from calcite and fluorite using anionic-nonionic collector”
This paper has interesting and new information, and could be accepted with major changes.
I have listed some comments below, which should be addressed.
Line 54
scheelite sueface must be scheelite surface
Line 66
excellent perfoamence must be excellent performance
Line 7
perfoamance of must be performance of
2.2. Experimental procedures
The volume of flotation cell is 40 mL.
How much mineral was used in flotation tests? (10 g of mineral?) (Single mineral flotation tests)
In ore flotation tests (mixed mineral flotation tests), what is the percentage of scheelite, calcite and fluorite in the ore?
Particle size has a great influence on the performance of the flotation process, so you could show the particle size of the material used.
Line 105
Did you use hydrochloric acid solution? Did you analyse the effect of pH =?
Line 140
doses., must be doses.
When the three minerals are individually floated (Fig. 4), scheelite recovery is not affected by the variation in SHMP concentration, with recoveries of around 85%. However, in the artificial mixed minerals tests (Fig. 5), it was found that scheelite recovery decreased dramatically with increasing SHMP concentration. Wat are the reasons for such a different behavior?
Why do not you show in Fig 5 the recovery of calcite and fluorite?
You have found that the content of WO3 decreased with increasing SHMP. This means that the increase in SHMP concentration caused a greater decrease in scheelite flotation than in calcite and fluorite flotation. According to Fig. 5, for SHMP concentrations greater than 4.8*10-6 mol/L, the recovery of scheelite in the floated is less than that of the other two minerals (grade of WO3 in the floated is lower than 26.9% - mixed minerals grade). Does this mean that the floatability of scheelite is lower than that of the other two minerals?
Line 273
the roughing grade dramatically increase to 1.65%,
must be
the roughing grade increase to 1.65%,
The reference style is not consistent.
Example:
[1] Shemi, A.; Magumise, A.; Ndlovu, S.; Sacks, N. Recycling of tungsten carbide scrap metal: A review of recycling methods and future prospects. Minerals Engineering 2018, 122, 195-205.
Must be
[1] Shemi, A.; Magumise, A.; Ndlovu, S.; Sacks, N. Recycling of tungsten carbide scrap metal: A review of recycling methods and future prospects. Miner. Eng. 2018, 122, 195-205.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
After reading the new version of the manuscript I can say that the authors addressed all the comments made by this reviewer thus I recommend publication of the paper in its present form.
