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Flotation waste of copper slag (FWCS) was used as a raw material for the preparation of a micro-electrolysis material (MEM) through a carbothermal reduction process. The performance of MEM was evaluated for the degradation of organic contaminants in water. The effects of preparation conditions on the performance of MEM were investigated. Results showed that the MEM prepared under the conditions of calcination temperature of 1100 °C, calcination time of 60 min, and coal dosage of 25% presented the best performance for degrading methyl orange (MO). The decolorization process was enhanced by increasing the MEM dosage, decreasing the initial pH of the solution, and raising the solution temperature. Moreover, the MEM presented good capability for the degradation of methylene blue, eosin Y, and acid fuchsin. X-ray diffraction (XRD) analysis showed that increasing the roasting temperature was beneficial to the formation of zero-valent iron (ZVI). Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) showed that micro-sized ZVI particles were formed in the MEM, and they contained a small amount of copper element. Meanwhile, the mechanism analysis showed that a redox reaction of the MEM and MO occurred, the azo bond of MO was destroyed, and sulfanilic acid was generated.

A microbial bio-based collector was isolated from iron mine soil using a combination of flotation and culturing techniques. Four microbial strains with greater than 75% recovery of pure hematite were separated using the technique. Classification and identification of the 4 strains by 16S rDNA sequences were conducted. Among them only 1 strain, termed F3, can act as a collector for hematite, as it is not pathogenic to humans. The morphology and hematite adsorption (by scanning electron microscopy; SEM), composition, zeta potential and hydrophobicity of strain F3 were further evaluated. Based on the changes in the zeta potential and hydrophobicity of a hematite surface before and after adsorption with F3, its adsorption mechanism was also analysed. The results revealed that the combination technique of flotation and bacterial culturing is a highly effective technique for isolating bio-collectors from iron mine soil. Two flotation stages were required to isolate strain F3, which belongs to the genus Stenotrophomonas . This rod-shaped bacterium had CH 2 , CH 3 and phosphate groups on its cell wall that imparted strong hydrophobicity and negative charge. Adsorption of strain F3 reduced the zeta potential of a hematite surface and enhanced its hydrophobicity. The adsorption of F3 to hematite is presumed to be through chemical adsorption. Therefore, strain F3 can be used as a bio-collector for hematite flotation.

A novel process for preparing direct reduction iron (DRI) and titanium nitride (TiN) from Panzhihua titanomagnetite concentrate is proposed. This process involves pelletizing, direct reduction roasting and magnetic separation. The effects of reduction temperature, coal dosage and reduction time on the phase transformation of composite pellets were investigated by X-ray diffraction. Results show that TiN formation proceeds less easily than metallic iron formation. Increasing the reduction temperature, reduction time and coal dosage can promote the transformation of titanium to TiN. Titanium was almost completely transformed into TiN under the conditions of 1300 °C reduction temperature, 26 wt % coal dosage and 90 min reduction time. The scanning electron microscopy (SEM) analysis showed that near-spherical metallic iron particles with diameters from dozens of microns to about 300 μm were formed in the reduced pellets, whereas the TiN particles generally measured less than 10 μm. The energy dispersive spectroscopy (EDS) results revealed that the TiN phase contains a certain amount of vanadium and carbon, and traces of other impurities. The reduced composite pellets under the optimum conditions were processed by grinding and subsequent magnetic separation. As a result, a DRI with 92.88 wt % Fe, 1.00 wt % Ti, and 0.13 wt % V was obtained, and the recoveries of Fe, Ti, and V were 92.85 wt %, 9.00 wt %, and 19.40 wt %, respectively. 91.00 wt % Ti and 80.60 wt % V were concentrated in the rough TiN concentrate.