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To effectively separate the valuable minerals in ludwigite, this study investigated the mineralogy of ore, particle-size distribution and mineral liberation characteristics. Most of the magnetite was intergrown with ascharite and serpentine. Nearly half of the serpentine existed in a dense, massive body. Most of the ascharite was encased in magnetite, and a small amount was embedded in the serpentine phase. After the microwave radiation, some intergranular and through cracks were formed to improve mineral liberation during the grinding process. The mass fractions for the +75 μm range decreased from 43.16 wt% for untreated samples to 24.31 wt% for treated samples with a microwave power of 3 kW for 40 s. By contrast, the mass fractions of particles in the −75 μm range increased from 56.84 wt% for untreated samples to 75.69 wt% for treated samples. D50 decreased from 53.54 µm for the untreated sample to 21.58 µm for the treated sample. The liberation degrees after the treated samples clearly improved and increased by 26.64% for magnetite, 18.92% for ascharite and 14.10% for serpentine. [ABSTRACT FROM AUTHOR]

To effectively separate and recover the valuable elements iron and boron from ludwigite, this study investigated the magnetic properties and the magnetic separation efficiency. And the reactivity of boron component in the B-bearing tailing was studied. The results indicated that the saturation magnetization of ore samples was increased with the increase of microwave power and heating time. Under condition of 40 s with 4 kW, the saturation magnetization of ore samples increased from 12.73 emu/g for the raw ore to 24.70 emu/g for the treated ore, an increased of 94.03%. After magnetic separation, the grade and recovery rate of iron in the iron concentrate and the boron grade in the tailing for the treated sample with 4 kW for 40 s were increased by 19.74%, 31.46% and 86.46% in comparison with those of the untreated ore. The sample was heated to 600 °C at 4 kW and held for 20 min, the reactivity of boron component in the B-bearing tailing reached 86.68 wt%, which increased by 34.01% compared with that of the raw ore and 4.43% compared with that of the optimal traditional roasting value at 700 °C for 2 h, indicating that the roasting temperature and time were obviously decreased and the reactivity was significantly improved by the microwave radiation. [ABSTRACT FROM AUTHOR]

To effectively separate the valuable minerals in ludwigite, this study investigated the grinding fineness behaviour and liberation characteristics. The results indicated that the particle yield of −75 μm with a microwave power of 4 kW for 40 s was increased by 18.22% in comparison to that of raw ore. The D(50) and D(90) raw-ore grinding products reached 53.52 and 215.16 μm, both of which were larger than microwave-treated samples. The particle-size distribution of the grinding products for treated ore was more uniform, and the amount of coarse and over-ground particles decreased significantly. The specific surface area, pore volume and pore diameter of the large particles were effectively increased after microwave heating, which improved the crushing and grinding characteristics of the grinding products by lowering the relevant mechanical properties. The monomer liberations of magnetite, ascharite and serpentine of microwave-treated ore samples were 55.33%, 35.48% and 74.98%, respectively, which represented an increase of 12.06%, 9.37% and 6.22% in comparison to untreated ore samples. The bonding characteristics among different minerals were altered through microwave treatment to weaken the bonding force and reduce the proportion of interlocked minerals, which allows these complex minerals to easily liberate after secondary grinding. [ABSTRACT FROM AUTHOR]

To liberate magnetite from ludwigite, the dielectric properties of ludwigite are investigated by cavity perturbation method at 2.45 GHz from 20 to 800 °C. The results show dielectric properties of ludwigite with temperature can be divided into three stages: at the first stage (20–200 °C), the dielectric constant (ε′), dielectric loss factor (ε″) and loss tangent (tan δ) increase approximately by 4.55, 47.31 and 38.89%, respectively, at the second stage (200–500 °C), ε′ increases slowly by 5.19%, while ε″ and tan δ gradually decrease, at the third stage (500–800 °C), ε′ first increases rapidly by 6.21% at 500–700 °C and then increases slowly beyond 700 °C, ε″ and tan δ fluctuate slightly. Meanwhile, the penetration depth (Dp) decreases significantly at 20–200 °C and decreases slightly at 200–500 °C, but decreases substantially again at 500–700 °C, and finally is closed to the constant value beyond 700 °C. The heating rate of magnetite is faster than those of ascharite and serpentine, which results in the formation of intergranular fractures to promote the liberation of magnetite from ludwigite by microwave heating. [ABSTRACT FROM AUTHOR]

To improve magnetic separation and recovery for Ludwigite, the influences of microwave radiation on the heating characteristics, microstructure, magnetic properties and the magnetic separation of Ludwigite are investigated. The magnetizations of untreated and microwave-treated samples with various microwave powers are analyzed using vibrating sample magnetometer. It is found that magnetite is an active material, while ascharite and serpentine are inactive materials. The heating rate of magnetite is faster than those of ascharite and serpentine, resulting in temperature gradient and internal stress among different components in Ludwigite. The effect of microwave power on the internal stress for mineral phases is positive. The internal stress significantly induces intergranular fractures and facilitates mineral liberation. After microwave treatment from 0 to 4 kW exposed for 40 s, serpentine is dissociated and the crystallinity of magnetite is increased, which leads to the saturation magnetization of samples increasing from 12.39 to 24.51 emu/g. Compared with untreated ore, the energy demand for microwave-treated Ludwigite is only about 0.44 kWh/kg, the grade of iron concentrate of microwave-treated Ludwigite increases from 48.56% to 58.06% and iron recovery increases from 69.44% to 96.35%, respectively. It can be concluded that microwave radiation has a positive effect on magnetic properties of Ludwigite and is conducive to magnetic separation from non-magnetic minerals with low energy consumption, thereby obtaining high iron recovery. [ABSTRACT FROM AUTHOR]