The flotation performances of magnesite and quartz were investigated with dodecylamine (DDA), N-dodecyliso-propanolamine (DIPA, containing one iso-propanol substituent group), or N,N-dodecyl-diiso-propanolamine (DDIPA, containing two iso-propanol substituent groups). Different flotation behaviors of the three collectors were obtained and compared. Fourier transform infrared spectroscopy (FTIR) analysis shows that the electrostatic attraction and hydrogen bonding were of crucial importance in the adsorption of three cationic collectors on mineral surfaces. Effect behavior and mechanism of the introducing iso-propanol substituent on amine collectors were investigated by surface tension measurements, molecular dynamics simulation (MDS), and density functional theory. These results show that the introduction of iso-propanol substituents into DDA could weaken the electrical properties of polar groups and enhance the cross-sectional size of polar groups, which can weaken the electrostatic effect and enhance the spatial position barrier effect, thereby enhancing the selectivity of DIPA and DDIPA. Meanwhile, the increasing hydroxyl (O) active site number enhanced the performance of the collector by affecting the strength of hydrogen bonding. (C) 2019 Elsevier B.V. All rights reserved.