The interaction between pine oil and marmatite without collectors and activators was investigated by flotation,scanning electron microscope and energy-dispersive spectrometer (SEM-EDS),infrared (IR) spectroscopy,Zeta potential,and first-principle theory calculations.The flotation results show that marmatite exhibits considerable floatability with the addition of pine oil.SEM-EDS results show that carbon atomic ratios on the surface are significantly high,which suggests that the flotation of marmatite is caused by the adsorption of pine oil.Further evidence of the adsorption mechanism was given by IR,and Zeta potential examining pine oil depends on the physical adsorption on the surface independently.The first-principle theory calculations indicate that pine oil molecule adsorbs on Zn and Fe atom surfaces by ionic bond and covalent bond of adsorption energies of-1.23 and-1.51 eV,respectively.P orbital of O atom,s orbital of Zn atom,and d orbital of Fe are the major participants.