Study on the Influence of Alkane C Chain Length on Coal Slime Flotation Based on Interfacial Thermodynamic Analysis and Characterization

The reagent regime is a key means to regulate mineral flotation behavior, with collectors being particularly crucial for enhancing the flotation process. This paper systematically investigates the action mechanisms of hydrocarbon oil components such as n-Nonane, n-Dodecane, n-Tridecane, n-Tetradecane, and n-Pentadecane in coal slime flotation through a combined approach of molecular dynamics simulation and experimental verification. The simulation results show that as the alkane chain length increases, the absolute value of the adsorption energy between the alkane and coal gradually increases (the adsorption energy is negative, indicating that the adsorption process can occur spontaneously), with n-Pentadecane exhibiting the highest adsorption energy. Experimentally, the oil–water mixture achieved optimal dispersity after ultrasonic treatment and standing for 10 min. This dispersity is characterized by the average oil droplet diameter and the most uniform droplet size distribution under the test conditions. The wetting heat test further verified that pentadecane exhibits the strongest interaction with coal slime and the fastest adsorption rate. In flotation tests, n-Tetradecane demonstrated the best actual flotation performance, with a clean coal yield of 70.88%, a combustible recovery of 82.55%, and a flotation perfection index of 50.75%. This study reveals the influence mechanism of alkane chain length on coal slime flotation behavior, providing a theoretical basis for the screening and compounding of efficient collectors.