The Effect of Macroscopic Particle Features on Mineral Dissolution

Round 1

Reviewer 1 Report

Review of the article „The effect of macroscopic particle features on mineral dissolution“ by Chandra Widyanda Winardhi et al.

The paper is about dissolution kinetics of minerals, an important subject which has been conceptually advanced in the past few years. In recent years, it has been worked out that the concept of "reactive surface" is dysfunctional and that instead the rate contributions of the solid surface provide mechanistic, quantitative, and prognostic explanations. In contrast to the so-called rate spectra, the "reactive surface" is therefore in the recent literature referred to as the "fudge factor" to fit kinetic data. Unfortunately, the current approach is not clearly reflected in this manuscript. Instead, it gets conceptually muddled and "reactive surface" (including poorly-defined surface area normalization of rates) and rate distributions are used in a confusing way. A second major weakness is that this manuscript does not make clear that the surface distribution of reaction rates on minerals based on three-dimensional CT data has been studied quantitatively and mechanistically in the past. This creates a wrong impression that does not correctly reflect the current state of the scientific community.

In addition to these two main points of criticism, there are a number of weaknesses, which I will specify below:

Line 8: „dissolution is thus not represented by a spectrum…“ Clear misrepresentation of the current state. The authors show multiple rate spectra in their manuscript, no?

Line 9: „Such dissolution rate spectra are usually obtained…“ There are CT data on this in the literature, which are suppressed here.

Lines 39-42: Incomprehensible sentence fragment, which is supposed to give the main motivation of the study in terms of content?!

Lines 48-50: This statement is contrary to the interpretation of the cited article, cf. the TOC figure, which gives a clear mechanistic explanation. This is not only wrong but misleading!

Lines 51-52: „Therefore, the observation…“ With the previous incorrect use of literature, this statement is no longer contextually justified.

Line 53: „This knowledge can be used to upscale…“ How is this supposed to work? There is no process of upscaling mentioned. These are just buzzwords, but no motivation in terms of content.

Line 57: „macroscopic particle features“: Dissolution reactions involve the breaking of chemical bonds. What exactly is to be investigated here macroscopically and quantitatively?

Line 61: „in order to localize the dissolution rate spectra“ What is meant by this? There are rate maps and rate spectra in the literature that clearly show monocrystalline and polycrystalline materials and the localization of the rate spectra, including corners, edges, faces, grain boundaries, different orientations, etc.

Line 67: „a locality in China“ That sounds a little sloppy. China is quite big.

Line 103: How was this area measured? What is the error? Here the error calculation is missing to quantify the uncertainty of the area normalization.

Line 109: „reactivity should be proportional…“ Sounds vague. Why „should“ this be the case? How is this justified?

Line 117: „Pseudo edges“ not defined

Line 124 ff: Here, the dissolution of a single crystal is analyzed. This crystal has crystallographically defined material properties. How is this taken into account in the calculation? This geometric description ignores the specific crystal physics.

Line 137: „Moreover, in order to understand better the influence of the distance from surface features,…“ There is no physical or chemical justification for this. Why should there be a macroscopic reactivity gradient at all? What mechanistic „influence“??

Line 184 and Table 1: Although the precision of the retreat height is justified by the pixel size, this does not allow us to say anything about the error of the dissolution rates in Table 1. The difference in the number and configuration of the voxels used for each area calculation would have to be quantified to give a reliable error calculation for the area used for normalization.

Chapter 3.2: The whole chapter remains cryptic because a macroscopic distance is conjured up as a parameter. Because no physical or chemical explanation is given, this parameter appears arbitrary. For this reason, it does not help for mechanistic explanations of the rate differences. As a user, I see only confusion here, but no potential for any application to other materials.

Lines 251ff: „…highlight the obvious fact…“ The given quantitative data rather suggest that the assumption for the calculation of the distances produces an artifact due to the disregard of crystal symmetry. Without giving a physical and chemical explanation and without having any information about the defect distribution of the crystal lattice, such an „obvious“ interpretation is unsubstantiated and adventurous.

Line 258: „The reactivity model…“ Which model? Equation 4 is not a model. The conceptual interpretation to surface reactivity in this manuscript is neither chemically nor physically justified. Without such an explanation, everything remains speculative.

In summary, in such a case, I would recommend rejection of the manuscript. However, this topic deserves a precise treatment, so I suggest a comprehensive revision here. I hope that the authors will be able to correct the weaknesses mentioned above and, more importantly, that they will be able to fundamentally improve the presentation of their study conceptually.

 

 

Author Response

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Reviewer 2 Report

Manuscript ID: minerals-2172946

Title: The effect of macroscopic particle features on mineral dissolution

Authors: Chandra Widyananda Winardhi et al.

Line 66. Authors should add more information about galena sample: deposite, XRD, etc.

Section 2.1. What caused the choice of “deep eutectic solvents” for the analysis of the dissolution process of a galena particle? Why wasn't acid used?

Section 2.1. Authors should separate this section to “Materials” and “Dissolution method”.

Section 2.1. I think the authors need to show a scheme or image of the experimental set for galena dissolution. This information will help other researchers who want to develop this direction.

Line 296-298. What are the authors' practical recommendations for galena dissolution?

Basically, when analysing the kinetics of minerals dissolution, the shrinking core model (SCM) is used, it assumes that the ore particle will be spherical. The authors studied a square particle. Can the results of the analysis of the dissolution process obtained by the authors be applied to the dissolution of spherical particles?

The references formed not in Minerals style, please use this link: https://www.mdpi.com/journal/minerals/instructions

Author Response

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Round 2

Reviewer 1 Report

The authors have definitely improved their manuscript. However, I see a logical inconsistency in the abstract. First the authors say that rate spectra do not work for large particles (why?), but then rate spectra are meaningfully used. Maybe the authors improve their first statement and state as motivation that they want to test the use of rate spectra on macroscopic objects.

Author Response

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