Mechanism Study of Xanthate Adsorption on Sphalerite/Marmatite Surfaces by ToF-SIMS Analysis and Flotation
, Guixia Fan 1, Hongxiang Xu 3, Wenxiang Chen 4, Shimei Li 2,* and Lingyun Huang 2Round 1
Reviewer 1 Report
The paper is well written and easy to follow. The paper presents thorough research into the xanthate adsorption on low and high Fe sphalerite samples. Well done.
Author Response
Response to Reviewer 1 Comments
Point 1: The paper is well written and easy to follow. The paper presents thorough research into the xanthate adsorption on low and high Fe sphalerite samples. Well done.
Response 1: Thank you for your positive comments on our study.
Reviewer 2 Report
Identification of active sites and species in xanthate adsorption on sphalerite/marmatite surfaces
It is desirable to clarify the title of the article.
May be need write?
“Study mechanism of xanthate adsorption on sphalerite/marmatite surfaces by ToF-SIMS analysis
and floatability”
The article contains the results of studies of 2 samples of sphalerite with different iron content. The results have practical value.
Comments and recommendations
1) It is necessary to use only two terms throughout the text - sphalerite (sample has 63,73% Zn and 0,6% Fe) and marmatite (48,26%Zn and 14,7% Fe)
2) It is desirable to change from the term “batch flotation” to terms: “batch flotation of a single mineral” (15), batch flotation of the single minerals (79, 116, 303 and other).
3) Delete the term " pure " (37) as described below unpure sphalerite.
4) It need to change the term " extracted” to “adsorption” or “accepting” (55)
5) May be needed to use the term “Pb-Zn ore” and does’t use “Sn-Zn ore” (83, 84). Sn-Zn ore isn't typical.
6) You have 2 samples of sphalerite from 2 different deposits. They have different genesis, chemical composition, so they must also have different specific surfaces. Comparing the amount of adsorption on sphalerite and marmatite without taking into account the specific surface area is not correct. Without taking into account the specific surface, it is advisable to compare the results of mineral processing conditions separately for sphalerite and marmatite separately (red results and black results). Look and change the fig. 1,2,4,5,7.
7) May be mistake 6% Fe, may be 0,6% Fe (152)?
8) Need to clearly write to figure title that these results are for sphalerite (290)
Comments for author File: 
Comments.pdf
Author Response
Response to Reviewer 2 Comments
Point 1: The manuscript provides some explanation of how the xanthates work on Fe-rich sphalerite. The manuscript is well written with only minor corrections needed:
Response 1: Thank you for your valuable suggestions; we have tried our best to revise this manuscript according to your comments.
Point 2: 107: “C” is used in the Equation (1) as a concentration of the xanthate after adsorption, not “A”.
Response 2: ‘A’ has been replaced by ‘C’ in the revise version.
Point 3: 131: cm, not cm3
Response 3: Thank you, ‘cm3’ has been changed to ‘cm’.
Point 4: 141: µm not µm2
Response 4: Sure, ‘µm2’ has been changed to ‘µm’.
Point 5: 181: Figure (2), Y axis “Rcovery”
Response 5: The Figure (2) has been updated, in which the error has been corrected.
Point 6: However, I would like to ask authors whether the results of the TOF-SIMS technique are reproducible also with another sample so that effects of uneven distribution of Fe and surface roughness can be ruled out.
Response 6: Thank you for this excellent comment and discussion. The results of ToF-SIMS can be reproducible with another sample. The reason is that the results of Fig. 5 and Fig. 6 in this study are obtained by statistical analysis. The ToF-SIMS spectra were collected from four separate 500 × 500 μm areas on each sample surface, and then acquired the statistical results of secondary ions. It can be seen from the error bar that the results have good reproducibility. Besides, before statistical analysis, each peak intensity was normalized by total ion intensity statistics, this method can minimize variations in the secondary ion signal due to differences in topography, sample charging, or instrumental conditions.
Reviewer 3 Report
I have read this paper and found it interesting, but I question its value.
Firstly, the authors appear to think that ore bodies seem to consist of a mono-distribution of sphalerite. That is, ore body A contains sphalerite with x percent iron in its lattice, and ore body B has sphalerite with y percent contained iron. Nature is not that generous! Generally speaking there is a distribution of iron from zero to the maximum value. For example, the Broken Hill lodes contain marmatite from quite low iron contents (2 to 6 percent) up to high iron contents (over 15 percent, with 0.5 percent manganese). Dugald River is similar with low and high lattice iron and manganese levels. Century is a low iron sphalerite, but does have patches of higher iron content. The point is Broken Hill reports zinc recoveries of greater than 90 percent, as does Dugald RIver, but Century only managed zinc recoveries in the low 80's. In a real ore there are other more powerful factors at play that prevent higher recoveries.
In reality this topic, unless it can be turned to some form of economic advantage is only an academic curiosity.
Turning to the paper, the following comments are warranted:
* Firstly. pure sphalerite containd 67.1 percent zinc and 32.9 percent sulphur. Your samples did not achieve this. What else did they contain? A full chemical analysis would be good.
* The particle size fraction examined is -74/+37 microns . . . drop the 0.4 it is not relevant.
* The ultrasonic treatment will remove adhering fines and loosely bound oxidation products, but some oxidation products remain on the surface. How many cycles (rinsing/ultrasonic) did you employ? More explanation is required? Did you do any surface analysis to show that this actually works?
* What precautions have you taken against oxidation? How do you know the results that you have achieved are not an artifact of the process used to prepare the sample?
* In the xanthate adsorption measurement section the equation says C, but the description of the parameters says A. This needs to be clarified/changed.
* The ToF-SIMS sample preparation is questionable. By polishing the mineral sample are you sure you have not introduced mechanical changes to the surfaces that may effect the adsorption characteristics? In Boulton's work the surface analysis would have been completed on minerals taken directly from the slurry. By polishing the sample then conditioning the polished block in the the various solutions you may actually introduce significant errors/artifacts that are not real.
* The labelling of the sphalerite samples is terrible. Is there a difference between SPH5 and SPH2? It would be better if you state at the beginning of the paper that you examples Sphalerite 1 (SPH1), which contained 0.6 percent iron as the low iron sphalerite,and sphaleirte 5 (SPH5), with 14.7 percent iron as the high iron sphalerite. Then through the text and figures all you have to do is say SPH1 or SPH5 . . . much less confusing.
* 40 ml of xanthate appears to be very high for 2 grams of pure mineral . . . further in most operating plants the copper sulphate addition is normally 5 to 10 times the dosage rate . . . not the same.
* Is ToF-SIMS the correct surface analysis technique? Yes, it is surface sensitive, but it is not quantitative and is destructive, blasting fragments from the surface which are then interpreted as bits of collector . . . I think this needs to be backed up with some XPS analysis which is quantitative and does provides chemical data.
* Figure 3 is very interesting, but also confusing. Also, why is only the high iron sphalerite data shown? Wouldn't it be relevant to show both sets of data?
* Figures 6 and 7 potentially don't show very much . . .
Author Response
Response to Reviewer 3 Comments
Point 1: I have read this paper and found it interesting, but I question its value. Firstly, the authors appear to think that ore bodies seem to consist of a mono-distribution of sphalerite. That is, ore body A contains sphalerite with x percent iron in its lattice, and ore body B has sphalerite with y percent contained iron. Nature is not that generous! Generally speaking there is a distribution of iron from zero to the maximum value. For example, the Broken Hill lodes contain marmatite from quite low iron contents (2 to 6 percent) up to high iron contents (over 15 percent, with 0.5 percent manganese). Dugald River is similar with low and high lattice iron and manganese levels. Century is a low iron sphalerite, but does have patches of higher iron content. The point is Broken Hill reports zinc recoveries of greater than 90 percent, as does Dugald RIver, but Century only managed zinc recoveries in the low 80's. In a real ore there are other more powerful factors at play that prevent higher recoveries.
In reality this topic, unless it can be turned to some form of economic advantage is only an academic curiosity.
Response 1: Thank you for your positive comments on our study and your valuable suggestions. Although sphalerite with different iron content exists in the same deposit, the average iron content of sphalerite in separate deposits may be different. Generally, sphalerite in high-temperature hydrothermal deposit has the highest iron content, followed by medium temperature hydrothermal deposit, and low-temperature hydrothermal deposit has the lowest iron content [H.-R. Wenk, A.G. Bulakh (Eds.), Minerals: their constitution and origin, Cambridge University Press, Cambridge; New York (2004)] [J.D. Dana, C.S. Hurlbut, C. Klein (Eds.), Manual of mineralogy (after James D. Dana) (19th ed.), Wiley, New York (1977)]. The iron content of sphalerite has been seen to influence the activation, and subsequent flotation behavior of sphalerite during fundamental studies, however, contradictory results have been reported [A review of the fundamental studies of the copper activation mechanisms for selective flotation of the sulfide minerals, sphalerite and pyrite], thus an understanding of the effect that iron in sphalerite has on the adsorption of xanthate and copper ions of this mineral may allow us to maximize sphalerite recovery.
Point 2: Turning to the paper, the following comments are warranted:
Firstly. pure sphalerite containd 67.1 percent zinc and 32.9 percent sulphur. Your samples did not achieve this. What else did they contain? A full chemical analysis would be good.
Response 2: We have conducted a chemical analysis of the samples. Specifically, the sphalerite (SPH1) contained 63.73 wt% Zn, 0.6 wt% Fe, 1.16 wt% Pb and 0.15 wt% Cu, representing a purity of 95.87% sphalerite, and the marmatite (SPH5) contained 48.26 wt% Zn and 14.7 wt% Fe, 0.09 wt% Pb and 0.17 wt% Cu, indicating a purity of 93.83% marmatite. We have supplemented the chemical analysis data of Pb and Cu in the revised manuscript. For bulk samples used in ToF-SIMS analysis, sphalerite/marmatite was selected as the analysis area by an optical lens of the ToF-SIMS instrument.
Point 3: The particle size fraction examined is -74/+37 microns . . drop the 0.4 it is not relevant.
Response 3: Thank you. ‘0.4’ has been deleted in the revised manuscript.
Point 4: The ultrasonic treatment will remove adhering fines and loosely bound oxidation products, but some oxidation products remain on the surface. How many cycles (rinsing/ultrasonic) did you employ? More explanation is required? Did you do any surface analysis to show that this actually works?
Response 4:
A: We cleaned the samples three times and with 3 min for each time.
B: In the revised manuscript, more detailed descriptions have been added as follows: ‘Before adding the reagent, the sample was ultrasonically cleaned in deionized water three times (3 min for each time) to remove surface oxidizing materials’.
C: We haven't done other surface analysis. In this study, the sample was ground using a three-head grinder with an agate mortar and pestle and was dry screened; after that, the sample was immediately used for the adsorption capacity measurements. Therefore, we think that the oxidation degree of the sample surface may not be high.
Point 5: What precautions have you taken against oxidation? How do you know the results that you have achieved are not an artifact of the process used to prepare the sample?
Response 5: We did not take precautions against oxidation. For each experiment, the samples were freshly prepared and immediately used for analysis. Besides, we tried to avoid contamination during sample preparation, for example, samples for ToF-SIMS analysis were prepared in a class-100 clean room at 22℃, the samples were immediately transferred to the vacuum chamber of TOF-SIMS instrument after dried by high purity nitrogen (this process takes about 20 min).
Point 6: In the xanthate adsorption measurement section the equation says C, but the description of the parameters says A. This needs to be clarified/changed.
Response 6: Thank you! ‘A’ has been replaced by ‘C’ in the revise version.
Point 7: The ToF-SIMS sample preparation is questionable. By polishing the mineral sample are you sure you have not introduced mechanical changes to the surfaces that may effect the adsorption characteristics? In Boulton's work the surface analysis would have been completed on minerals taken directly from the slurry. By polishing the sample then conditioning the polished block in the the various solutions you may actually introduce significant errors/artifacts that are not real.
Response 7:
Thank you for your valuable comments.
A. Polishing may introduce mechanical changes to the surfaces. However, we would like to talk about why the samples need to be polished. ToF-SIMS is a highly surface sensitive technology. It is almost impossible to obtain mass spectra with high mass resolution on rough sample surfaces, such as powder samples surfaces. Because of the need for high mass resolution spectra in this study, sample polishing is necessary.
B. With regard to polishing procedures, we have provided a more detailed description in the revised manuscript as follows: ‘The preparation of bulk Sphalerite/marmatite samples follow the following steps: (1) The samples were cut into rectangular shaped pieces approximately 1.5 × 1 × 0.5 cm in length, width and depth, using a fine slow diamond saw. (2) Cut samples were polished with wet silicon carbide paper in the sequence of 600, 800, 1200, 2000 and 4000 meshes, and then polished with 5 and 1 μm alumina powder suspensions, respectively. (3) The freshly polished samples were ultrasonically cleaned for 5 min each in deionized water, absolute ethanol, and deionized water. (4) The cleaned samples were dried by using high-purity nitrogen.’ Similar polishing procedures have been described in the following references: [Understanding Copper Activation and Xanthate Adsorption on Sphalerite by Time-of-Flight Secondary Ion Mass Spectrometry, X-ray Photoelectron Spectroscopy, and in Situ Scanning Electrochemical Microscopy] and [The effect of bulk iron concentration and heterogeneities on the copper activation of sphalerite].
Point 9: The labelling of the sphalerite samples is terrible. Is there a difference between SPH5 and SPH2? It would be better if you state at the beginning of the paper that you examples Sphalerite 1 (SPH1), which contained 0.6 percent iron as the low iron sphalerite,and sphaleirte 5 (SPH5), with 14.7 percent iron as the high iron sphalerite. Then through the text and figures all you have to do is say SPH1 or SPH5 . . . much less confusing.
Response 9: Sorry, this is an error. Figure 1 has been updated, in which ‘SPH2’ has been changed into ‘SPH5’. Thank you for your suggestion. We have stated at the ‘2.1 Materials’ section of the manuscript.
Point 10: 40 ml of xanthate appears to be very high for 2 grams of pure mineral . . . further in most operating plants the copper sulphate addition is normally 5 to 10 times the dosage rate . . . not the same.
Response 10: Since in practice there are other minerals such as pyrite in the ore, these minerals also consume copper sulfate, so this may lead to the dosage of copper sulfate is greater than xanthate. For this study, we studied the adsorption products of xanthate on the surface of sphalerite with or without copper-activated; therefore, we want to avoid the influence of residual copper ions in solution on xanthate adsorption.
Point 11: Is ToF-SIMS the correct surface analysis technique? Yes, it is surface sensitive, but it is not quantitative and is destructive, blasting fragments from the surface which are then interpreted as bits of collector . . . I think this needs to be backed up with some XPS analysis which is quantitative and does provides chemical data.
Response 11: ToF-SIMS is not a quantitative technique due to the matrix effect. But in some cases, semi-quantitative analysis can be carried out, for example, samples with similar surface properties. We performed a semi-quantitative analysis on sphalerites with different iron content, as shown in the figure below. The results show that the chemical analysis results are in good agreement with the ToF-SIMS results. It is a good suggestion to further evaluate the results through XPS. In the future, we will conduct XPS to study this topic further.
Fig. 1 Correlation analysis of Fe and Zn contents obtained by ToF-SIMS: (a) Fe; (b) Zn
Point 12: Figure 3 is very interesting, but also confusing. Also, why is only the high iron sphalerite data shown? Wouldn't it be relevant to show both sets of data?
Response 12: The reason why we only show marmatite data is that sphalerite data are similar to marmatite data, and marmatite has higher intensity peaks of iron xanthate (CSFe+, OCSFe−, and OCS2Fe−) and dixanthogen (C2S2−). Therefore, the adsorption products of xanthate can be explained more clearly by the data of marmatite. In addition, we compare the difference of xanthate adsorption products between sphalerite and marmatite surface by Fig. 4 and Fig. 5, according to these results, the xanthate adsorption product on the surface of the sphalerite can be reflected.
Point 13: Figures 6 and 7 potentially don't show very much . . .
Response 13: Figures 6 and 7 mainly compare the difference of different secondary ions distribution on marmatite surface to infer the correlation among zinc xanthate, iron xanthate, copper xanthate, and dixanthogen.
Author Response File: Author Response.pdf
Reviewer 4 Report
The manuscript provides some explanation of how the xanthates work on Fe-rich sphalerite. The manuscript is well written with only minor corrections needed:
107: „C“ i sused in the Equation (1) as a concentration of the xanthate after adsorption, not „A“.
131: cm, not cm3
141: µm not µm2
181: Figure (2), Y axis „Rcovery“
However, I would like to ask authors whether the results of the TOF-SIMS technique are reproducible also with another sample so that effects of uneven distribution of Fe and surface roughness can be ruled out.
Author Response
Response to Reviewer 3 Comments
Point 1: Pre-review
Identification of active sites and species in xanthate adsorption on sphalerite/marmatite surfaces
It is desirable to clarify the title of the article.
May be?
“Study mechanism of xanthate adsorption on sphalerite/marmatite surfaces by ToF-SIMS analysis and floatability”
Response 1: Thank you for your valuable suggestions; the title you suggested is better. In the revised manuscript, the title has been changed to “Mechanism study of xanthate adsorption on sphalerite/marmatite surfaces by ToF-SIMS analysis and flotation”.
Point 2: The article contains the results of studies of 2 samples of sphalerite with different iron content. The results are of practical value.
Response 2: Thank you for your positive comments.
Point 3: It is necessary to use only two terms throughout the text - sphalerite (sample has 63,73% Zn and 0,6% Fe) and marmatite (48,26%Zn and 14,7% Fe).
Response 3: Thank you for your good suggestion. We have unified the expressions of sphalerite and marmatite throughout the revised manuscript.
Point 4: It is desirable to change from the term “batch flotation” to terms: “batch flotation of a single mineral” (15), batch flotation of the single minerals (79, 116, 303 and other).
Response 4: We have made one-to-one modifications in accordance with your suggestions in the revised manuscript.
Point 5: Delete the term "pure" (37) as described below unpure sphalerite.
Response 5: "pure" has been deleted in the revised manuscript.
Point 6: It need to change the term "extracted” to “adsorption” or “accepting” (55)
Response 6: We have revised it in accordance to your suggestion. “extracted” has been changed into “adsorption” in the revised manuscript.
Point 7: May be needed to use the term “Pb-Zn ore” and don’t use “Sn-Zn ore” (83, 84). Sn-Zn ore isn't typical.
Response 7: Thank you. “Sn-Zn ore” has been changed into “Pb-Zn ore” in the revised manuscript.
Point 8: You have 2 samples of sphalerite from 2 different deposits. They have different genesis, chemical composition, so they must also have different specific surfaces. Comparing the amount of adsorption on sphalerite and marmatite without taking into account the specific surface area is not correct. Without taking into account the specific surface, it is advisable to compare the results of mineral processing conditions separately for sphalerite and marmatite (separately red and black). Look and change the fig. 1,2,4,5,7.
Response 8: Thank you for your comments. Even if the samples come from the same deposit, the iron content will affect their crystal bulk and surface properties. Therefore, as the reviewer said, the surface properties of sphalerite with different iron contents in different deposits are indeed entirely different. The purpose of this study is to study the surface differences of these two kinds of raw minerals, especially the differences after adding copper ions and xanthate, to illustrate the positive or negative effects of iron ions on the flotation of sphalerite. Of course, throughout the experiment, the samples were processed in the same procedures, such as polishing, ToF-SIMS, and flotation, etc.
Point 9: May be it mistake 6% Fe, may be 0.6% Fe (152)?
Response 9: Sorry, this is a error, we have corrected it.
Point 10: Need to clarify to figure title that these results are for sphalerite (290)
Response 10: Thank you for your excellent suggestion. This part needs clarification. Figures 6 and 7 show the ToF-SIMS negative-ion images of marmatite surface and Cu-activated marmatite surface after interaction with BX at pH 6.5, respectively. We have changed the titles of the figures in the revised manuscript as follows:
“Figure 6. ToF-SIMS negative-ion images of xanthate absorbed marmatite surface at pH 6.5”
“Figure 7. ToF-SIMS negative-ion images of Cu-activated marmatite surface after interaction with xanthate at pH 6.5”
Corrections have also been made to the corresponding parts of the text.
Point 11: The authors give the results of studies for 2 samples - sphalerite (sample has 63,73% Zn and 0,6% Fe) and marmatite (48,26%Zn and 0,6% Fe), but the text of the article uses different terms, for example:
“sphalerite with a low Fe content is higher than that on sphalerite with a high Fe content”
“mechanisms of xanthate adsorption on Fe-bearing sphalerite surfaces.
Response 11: Thank you for your correction. We have unified the expressions of sphalerite and marmatite throughout the revised manuscript, for example:
“sphalerite is higher than that on marmatite.”
“mechanisms of xanthate adsorption on sphalerite/marmatite surfaces.”
Round 2
Reviewer 3 Report
It would be wise to add a sulphur assay as well, and they to show that the composition of the two sphaleirtes adds up to 100 percent.
I still struggle with the surface analysis (ToF-SIMS) and the preparation of the minerals as it is not the same as grinding prior to flotation.
I am not convinced that ToF-SIMS is the right analytical technique, and think the analysis should be backup with some XPS.
Author Response
Response to Reviewer 3 Comments (Round 2)
Point 1: It would be wise to add a sulphur assay as well, and they to show that the composition of the two sphaleirtes adds up to 100 percent.
Response 1: Thank you for your valuable suggestion. It is well known that the results of the chemical analysis are relatively accurate compared with other spectral analyses (see attached Table S1). Therefore the chemical analysis of common elements in sphalerite and marmatite, such as Zn, Fe, S, Pb, and Cu was conducted. Chemical assays showed that the sphalerite (SPH1) contains 63.73 wt% Zn, 0.60 wt% Fe, 31.80 wt% S, 1.16 wt% Pb and 0.15 wt% Cu, and the marmatite (SPH5) contained 48.26 wt% Zn, 14.70 wt% Fe, 33.10 wt% S, 0.09 wt% Pb and 0.17 wt% Cu. The results of the above chemical analysis indicated that the purity of sphalerite and marmatite were both high and could be used as suitable research objects. The chemical analysis data of S, Pb and Cu were added in the revised manuscript. The total contents of Fe, Zn, S, Pb, and Cu in the two samples are more than 96%, which is close to 100 percent. The reason why the total is less than 100% is that there are some other trace elements that have not been tested.
Table S1. Chemical analysis results of common elements in sphalerite and marmatite.
Point 2: I still struggle with the surface analysis (ToF-SIMS) and the preparation of the minerals as it is not the same as grinding prior to flotation.
Response 2: Thank you for your comments. Indeed, it is difficult to carry out in situ analysis in the flotation process with the test technology like ToF SIMS at present, so the samples in this study and the situation they are in are not entirely the same as the samples and environment in the flotation. However, the study can explain the adsorption mechanism of xanthate on mineral samples to some extent.
Point 3: I am not convinced that ToF-SIMS is the right analytical technique, and think the analysis should be backup with some XPS.
Response 3:
ToF-SIMS provides an incredibly versatile analytical method capable of detecting and analysing individual elements, molecular species, as well as gaining insight into structure, binding phenomena and molecular orientations. [refs. ‘Surface analysis for compositional, chemical and structural imaging in pharmaceutics with mass spectrometry: A ToF-SIMS perspective’; ‘Static secondary ion mass spectrometry (S‐SIMS) Part 1: methodology and structural interpretation’, and ‘Low energy ion scattering (LEIS). A practical introduction to its theory, instrumentation, and applications’]. ToF-SIMS can rapidly, statistically analyse the detailed differences of minerals surface chemistry, reveal elemental and molecular information from the surface of different minerals during flotation (eg, oxidation products, reagent adsorption, and surface layer formation) [refs. ‘The development of statistical ToF‐SIMS applied to minerals recovery by froth flotation’ and ‘TOF-SIMS studies of surface chemistry of minerals subjected to flotation separation – A review’.]
For example, Liu et al. studied the adsorption mechanism of HATT on chalcopyrite surface by ToF-SIMS. The results of ToF-SIMS are shown in attached Fig. S1. Based on Fig. S1, they draw the conclusions: ToF-SIMS demonstrated that on the self-assembly layers, HATT bound overwhelmingly with copper atoms on chalcopyrite surface by formation of Cu-S and Cu-N bonds. Their XPS results supported the conclusions of ToF-SIMS. [ref. ‘In situ probing the self-assembly of 3-hexyl-4-amino-1,2,4-triazole-5-thione on chalcopyrite surfaces’.]. They also did other similar researches through ToF-SIMS. [refs. ‘Study of N-isopropoxypropyl-N-ethoxycarbonyl thiourea adsorption on chalcopyrite using in situ SECM, ToF-SIMS and XPS’ and ‘Cu(I)/Cu(II) mixed-valence surface complexes of S-[(2-hydroxyamino)-2-oxoethyl]-N,N-dibutyldithiocarbamate: Hydrophobic mechanism to malachite flotation’.]
Therefore, previous studies have shown that ToF SIMS is a good analytical technique in flotation field.
Majid Ejtemaeid et al. found by Cryo-XPS that the dixanthogen is the main interfacial product of the BX interaction with Cu-activated sphalerite; The interaction of unactivated sphalerite with BX produced much less than a monolayer of chemisorbed xanthate; only minor quantities of Zn and Cu xanthates at the sphalerite surface with or without activated. [ref. ‘Interaction of sphalerite with potassium n-butyl xanthate and copper sulfate solutions studied by XPS of fast-frozen samples and zeta-potential measurement’.]
Wang et al. suggested dixanthogen is involved in the adsorbed AX species on sphalerite surface by Cryo-XPS study.
Majid Ejtemaeid et al. also found that Cu-xanthate complex on the Cu-activated sphalerite and dixanthogen on the Cu-activated pyrite were the dominant surface components after treating with AX. [ref. ‘Kinetic studies of amyl xanthate adsorption and bubble attachment to Cu-activated sphalerite and pyrite surfaces’.]
Larsson et al. suggested the presence of chemisorbed xanthate and dixanthogen on sphalerite surface by FTIR-ATR spectroscopy. [ref. ‘Xanthate adsorbed on ZnS studied by polarized FTIR-ATR spectroscopy.’]
The REFLEXAFS analysis of the S K-edge data from unactivated ZnS reacted with xanthate at pH 5 indicates that both zinc xanthate and dixanthogen form during this process. [ref. ‘Copper activation of sphalerite and its reaction with xanthate in relation to flotation: an X-ray absorption spectroscopy (reflection extended X-ray absorption fine structure investigation’.]
After receiving the reviewer's suggestion, we conducted an urgent XPS test within these five days. But, the spectroscopic signals of xanthate-related adsorbates were very weak, which can not be parsed. In this study, ToF SIMS provided some useful and interesting information, because ToF SIMS technology is more sensitive compared with XPS. As Majid Ejtemaeid pointed out：there are surprisingly few XPS studies on sphalerite treated with xanthates or other collectors, with no spectroscopic signals of xanthate-related adsorbates in fact revealed and analyzed.
For these above reasons, we do not add the results of XPS. We think that our current research can provide readers some references of xanthate adsorption on sphalerite/marmatite surfaces.
Fig. S1 ToF-SIMS spectra of chalcopyrite surfaces after HATT adsorption in the operational mode of surface spectroscopy: (a) negative ions and (b) positive ions. (From Liu et al.’ studies.)
Author Response File: 
Author Response.docx
