Flotation behavior of four C18 hydroxamic acids as collectors of rhodochrosite

• The different degrees of unsaturation are important for flotation of rhodochrosite.
• LHA owns high selectivity because it has the proper number of double bonds.
• The adsorption occurred on rhodochrosite surface would be chemisorption.
• The formation of five-membered chelate ring is proposed.
• The adsorption of LHA onto rhodochrosite leads to the formation of agglomerates.

The number of double bonds effects on the flotation of low-grade poor manganese ores using hydroxamic acid was studied. Four types of hydroxamic acids, namely stearic hydroxamic acid (SHA), oleic hydroxamic acid (OHA), linoleate hydroxamic acid (LHA) and α-Linolenic hydroxamic acid (αLHA) were synthesized and tested to float manganese ores containing 10.7% Mn. In all of the collectors screened, the study showed that LHA is a particularly good collector and has an excellent selectivity in rhodochrosite flotation. The surface tension experiment indicates that the values of surface tension cannot always function as a reliable indicator of the effectiveness of flotation collectors. The results of zeta potential and Fourier transform infrared spectroscopy (FTIR) demonstrate that chemisorption accounts for the flotation mechanism. Besides, the formation of five-membered chelate ring of rhodochrosite with LHA was proposed. The scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) data indicate that the flotation separation using LHA is significantly efficient, and the adsorption of LHA onto rhodochrosite leads to the formation of hydrophobic agglomerates of rhodochrosite particles which enhance the floatability of rhodochrosite.

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