Study on the influence of low-temperature hydrogen plasma reconstruction on the surface properties and floatability of hematite

Low-temperature plasma technology, a novel and environmentally friendly surface modification technique, has garnered significant attention for its simple operation, high safety, fast reaction speed, and low energy consumption. While widely used in the treatment of coal and sulfide ores, its use on oxide ores remains largely unexplored. Plasma technology also shows potential for flotation reagent pretreatment but is still in the laboratory stage in mineral processing engineering. Its application is mainly focused on mechanism research, hindered by the limited scale of equipment, which makes large-scale ore treatment unfeasible. This study investigates the surface modification of hematite using low-temperature hydrogen plasma pretreatment to enhance its separation efficiency from quartz by minimizing the use of the inhibitor corn starch. Experiments were conducted to determine the optimal conditions for mineral flotation with particles sized −0.074 mm to +0.038 mm, as well as for low-temperature hydrogen plasma pretreatment. The low-temperature hydrogen plasma pretreatment method involved placing the ore powder in a TS-VPR05 type plasma generator, with parameters such as gas flow, treatment time, and power adjusted accordingly. To ensure uniformity, the ore was spread evenly in a thin layer, and a consistent amount was treated each time. For mixed ore tests, individual minerals were treated separately before being combined to maintain consistent proportions. Flotation tests were carried out immediately after treatment to avoid sample degradation. Comparative analyses of recovery rates between treated and untreated samples were performed using single mineral flotation and artificially mixed ore flotation. Surface changes were assessed using atomic force microscopy, scanning electron microscopy-energy dispersive spectrometer, X-ray photoelectron spectrometer, and ultraviolet spectroscopy. The single mineral flotation experiments revealed that under optimal conditions of 240 W power, 400 mL·min−1 gas flow, and 20 min of treatment, the inhibitory effect of corn starch on hematite was significantly improved. For artificially mixed ore, the selectivity index improved by 3.3784 when combined with a starch concentration of 4 mg·L−1. Atomic force microscopy and scanning electron microscopy analyses showed that low-temperature hydrogen plasma etched the surface of hematite, while X-ray photoelectron spectroscopy and energy dispersive spectroscopy results indicated reduced oxygen content on the hematite surface. The ultraviolet spectrophotometer confirmed increased starch adsorption after low-temperature hydrogen plasma treatment. The treatment had a small effect on the structure and properties of quartz. The study concludes that low-temperature hydrogen plasma treatment modifies the active sites on the mineral surface, thereby affecting the adsorption and action of the mineral surface agents.