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Adsorption of quaternary ammonium salt hydrophobic modifiers on the α-quartz (001) surface : a density functional theory study

Liu Chunfu, Wang Weitao, Wang Han, Zhu Chenyu, Ren Bao

Physicochemical Problems of Mineral Processing

2023

Vol. 59, iss. 3

art. no. 170260

To investigate the adsorption mechanism of quaternary ammonium salt on the α-quartz (001) surface, the adsorption models of hydrophobic modifiers 1231, 1431, 1631 and 1831 were constructed and simulated using the density functional theory (DFT). Results indicate that the adsorption energy of quaternary ammonium salt increases with the increase of carbon chain length, and the adsorption energy reaches the maximum at 18 carbon atoms; however, the adsorption capacity of 1631 is weak owing to the carbon chain deflection. Based on the Mulliken bond population analysis, reagent 1831 has the strongest interaction with α-quartz (001) surface compared with 1231, 1431 and 1631; and during the adsorption process, charge transfer and electrostatic attraction occur between the reagent and α-quartz (001) surface with similar degrees of charge transfer observed. This study emphasizes that electrostatic attraction plays a key role in the adsorption process, while the week hydrogen bonding plays a secondary role.

Crack damage evolution in concrete coarse aggregates under microwave‑induced thermal stress

Yuan Yuan, Shao Zhushan, Qiao Rujia, Guo Xuan, Wang Weitao

Archives of Civil and Mechanical Engineering

2022

Vol. 22, no. 3

art. no. e108

Coarse aggregates of waste concrete can be efficiently separated from mortar under microwave irradiation. However, the microwave-induced damage in aggregates are restricting mechanical properties of the aggregates for replacing natural aggregates. Since damage evolution in rocks treated by microwave are influenced by mineralogy and microwave operating parameters, such as power and irradiation time, understanding the microwave weakening mechanism of rocks is necessary to assess and control the damage of aggregates for recovery of high-quality concrete coarse aggregates. This article develops an approach for evaluating crack damage evolution in aggregates exposed to microwave by combining theoretical analysis with experimental investigation. A theoretical heat source-matrix model based on electromagnetic and thermal properties of mineral components is established for microwave heated aggregates. Substituting microwave irradiating parameters and mineralogy of the aggregates into the model, corresponding temperature fields and thermal stress fields are solved. Cracks in aggregates after microwave exposure are observed using scanning electron microscopy (SEM) and quantified in terms of crack length, density and intensity. Crack damage varied with microwave energy is assessed by crack length and density. Crack propagation is further discussed by contrast of stress intensity factor (SIF) at the crack tip and fracture toughness of the aggregate. Cracking behavior analyzed by SIF of cracks is consistent with that obtained from quantitative analysis on SEM images. The results suggest that granite shows a stronger resistance to thermal stress damage compared with basalt under microwave exposure, and a multistage microwave treatment should be adopted for recovery of various aggregates.