Adsorption mechanism and flotation behavior of ammonium salt of N-Nitroso-N-phenylhydroxyamine on malachite mineral

The adsorption mechanism between malachite and a specific organic ligand of the ammonium salt of N-Nitroso-N-phenylhydroxyamine (NBH) with the NH4+ group and nitrosamine polar group has been studied. The tapping mode atomic force microscopy (AFM) imaging illustrated that irregular protrusions were covered on malachite surface at the nanoscale when malachite was treated in NBH solutions under alkaline conditions at pH 9.5. It indicated that the NBH displayed an excellent affinity to malachite, and the adsorption density was correlated with the concentration of NBH. Based on copper ammine theory and the results of Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), the intermediate transition process of the interaction between malachite and NBH can be summarized as activation, diffusion and reduction, combination, and redeposition. The copper ions removed from the ammonia-activated malachite surface combined with the NBH resonating structures to form the bidentate and monodentate complexes. Eventually, those microscopic analyses are confirmed by the macroscopic flotation test. The flotation recovery illustrated the formation of ligand-Cu complex strengthened the hydrophobicity of malachite in a three-phase system. Therefore, it is feasible using NBH as collector to selectively separate malachite from gangue minerals in flotation experiments.