Surface roughness has an important influence on the wettability of particles. This paper is an innovative exploration to control the surface wettability of apatite and dolomite from the perspective of roughness in the background of phosphate flotation. Roughness characteristics of apatite and dolomite particles and its effects on wettability were investigated with surface roughness, contact angle measurements, and SEM analysis. The relationship between surface energy and wettability of different roughness surfaces was also discussed. The results indicated that the influence of roughness on apatite and dolomite particles showed the same regularity, and wettability increased with the increasing roughness for hydrophilic surfaces, while the wettability decreased for hydrophobic surfaces. The influence of roughness on wettability can be well explained by Wenzel and Cassie models, and the surface energy of different rough surfaces had a strong correlation with their wettability. When sodium oleate was added after acid treatment, the apatite was hydrophilic, while the dolomite was hydrophobic; the difference in wettability between them became greater as surface roughness increased. Thus, it can be predicted that the selective separation of dolomite and apatite under acid reverse flotation conditions can be strengthened by increasing the mineral surface roughness during comminution.

Structural and electronic properties of Si termination, O-middle termination, and O-rich terminations of a quartz (001) surface as well as water molecule adsorption on it were simulated by means of density functional theory (DFT). Calculated results show that the O-middle termination exposing a single oxygen atom on the surface is the most stable model of quartz (001) surface, with the lowest surface energy at 1.969 J·m⁻², followed by the O-rich termination and Si termination at 2.892 J·m⁻² and 2.896 J·m⁻², respectively. The surface properties of different terminations mainly depend on the surface-exposed silicon and oxygen atoms, as almost all the contributions to the Fermi level (E_F) in density of states (DOS) are offered by the surface-exposed atoms, especially the O2p state. In the molecular adsorption model, H₂O prefers to adsorb on the surface Si and O atoms, mainly via O₁–H₁ bond at 1.259 Å and Si₁–O_w at 1.970 Å by Van der Waals force and weak hydrogen bond with an adsorption energy of −57.89 kJ·mol⁻¹. In the dissociative adsorption model, the O-middle termination is hydroxylated after adsorption, generating two new Si–OH silanol groups on the surface and forming the O_wH₂···O₄ hydrogen bond at a length of 2.690 Å, along with a large adsorption energy of −99.37 kJ·mol⁻¹. These variations in the presence of H₂O may have a great influence on the subsequent interfacial reactions on the quartz surface.

The wide application of concrete prepared with coal gangue (CG) as an aggregate (CPCGA) is limited because of the low mechanical strength and strong water absorption capacity of CG. This paper used silica fume (SF) to improve the performance of the interfacial transition zone (ITZ) in CPCGA and revealed the enhancement mechanism. The results showed that the compressive strength of CPCGA prepared with cement replaced by a suitable amount of SF at the age of 28 days increased by more than 30%, and the flexural strength increased by over 20%. The SF could effectively reduce the porosity and micropore size in the ITZ of CPCGA, and the porosity of the ITZ in CPCGA added with 7.50% SF decreased by 44.22, 46.16, and 24.46% at distances from the aggregate surface of 10, 50, and 100 μm, respectively, compared with CPCGA without SF. Further research showed that Ca(OH)₂ (CH) generated in the cement hydration reaction reacted with a large amount of active SiO₂ in SF to restrain the formation of coarse CH in the ITZ of CPCGA, and the calcium silicate hydrate (C-S-H) gel generated filled the ITZ micropores to reduce the ITZ porosity further. Moreover, the reaction of SF and CH helped to promote the hydration reaction of cement to proceed thoroughly in CPCGA, thus improving CPCGA performance.