Effects of Processing Conditions on the Properties of Porous Diatomite Granules Prepared by Sodium Alginate Gelation

Round 1

Reviewer 1 Report

Comments for author File: Comments.pdf

Author Response

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Reviewer 2 Report

The paper described the manufacturing of porous ceramic granules derived from an inexpensive silica source and a biopolymer cross-linked by ion exchange, specially, the effects of heat-treatment conditions on the pore and mechanical characteristics of these granules was demonstrated. These results and the obtained conclusions may contribute to the preparation and optimization of millimeter-sized spherical porous diatomite supports. It can be published after addressing following comments.

Q1. Lines 214-216: The pre-treatment conditions for determining N₂ adsorption/desorption isotherms of samples at 77 K should be described.

Q2. Lines 262-264: Authors described the bimodal particle size distribution with a secondary peak at around 0.31-0.54 μm, corresponding to the D10 value of the distribution (∼0.26 μm), what’s mean of the “bimodal”?

Q2. Lines 303-310: Authors proposed that at low shear rates, suspended SiO₂ particles are subject to repulsive inter-particle electrostatic forces, why is there the repulsive inter-particle electrostatic forces among the suspended SiO₂ particles?

Q3. Lines 330-334: Authors elucidated that “this was facilitated by the rapid gelation kinetics in the ion exchange process between Na⁺ ions interacting with the COO^- units of sodium alginate and Ca²⁺ ions in the gelling bath”. How do authors consider the ion exchange process between Na⁺ and Ca²⁺ be an equilibrium exchange?

Q4. In Figure 11, the adsorbed capacity values in left Y-axis and the offset values of the isotherms should be provided.

Author Response

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Reviewer 3 Report

This manuscript is quite interesting and well-organized.  It is suitable to be accepted in Applied Sciences after minor revision.   Comments are given as follows:

1. Please draw a scheme to illustrate the detailed procedure of ball-milled conditions for the diatomite.

2. What is the average particle size of the distinctive diatomites before and after the ball-milled process ?

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Reviewer 4 Report

This manuscript is very well written and explained.  The properties of the obtained products show potential applicability of these granules as support materials for catalytic as well as use for adsorption. However, I’d like to point out two things:

1. What is the temperature of the calcined diatomite powder? This answer should be address in section 3.2. and corelated with the current interpretation of the xrpd diagram. The "stability" of the material is mainly to two factors: the purity of the diatomaceous earth and the fact that the starting material (diatomaceous earth) is not in natural state (meaning the materials is calcined). 

2. SEM shows excellent images of changes occurring during the elevation of the sintering temperature (especially at 1200 C). Annihilation of the pores (Figrue 8, E) sintered, as well as emergence of large-sized pores (Figure 9. C) both at 1200 C.  Perhaps the images should mention the size of the pores and how can these two occurrences merge with the pore size distribution. 

Author Response

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