Influence of hydrophobic carbon chain length on flotation performance of amine surfactants

Firstly, four surfactants with different hydrophobic carbon chain lengths, namely, decylamine(DA), dodecylamine(DDA), tetradecylamine(TDA) and hexadecylamine(HDA), were selected to investigate as study object. Secondly, the effect of hydrophobic carbon chain length on the flotation performance of the agents with quartz and hematite as the target minerals was studied by using the single mineral flotation test. Finally, the effect mechanisms of carbon chain length on the critical micelle concentration, foaming ability, foam stability and adsorption and hydrophobicity with minerals were analyzed by surface tension, contact angle and foam performance tests. The results show that with the increase of hydrophobic carbon chain length, the collecting ability of agents shows a tendency of increasing and then decreasing. The collecting ability of DDA and TDA is stronger for quartz and hematite. At the same time, the growth of hydrophobic carbon chains reduces the solubility of the pharmaceuticals, which leads to a gradual decrease in their optimal flotation pH. The critical micelle concentration and surface tension of the agent gradually decrease as the hydrophobic carbon chain length increases, but the decrease is gradual, and so an appropriate increase in hydrophobic carbon chain length is beneficial for mineral particle adhesion to air bubbles. Following interacting with agents, the free energy of the mineral surface decreases, the contact angle increases to varying degrees, and the hydrophobicity of the mineral surface increases, the latter of which changes significantly in the DDA and TDA systems. The addition of quartz particles and the increase in the length of the hydrophobic carbon chain improve foaming performance and foam stability of the agent. When the hydrophobic carbon chain lengths are 12 and 14, the pharmaceutical exhibits appropriate solubility, hydrophobicity, foaming performance, and foam stability, making it acceptable for flotation separation of valuable minerals. © 2024 Central South University. All rights reserved.