In Baotou rare earth tailings ore, the grade of rare earth is close to that of the raw ore nearly. The rare earths are discarded in tailings dam caused by a serious waste of resources. First of all, the decomposition products of bastnaesite- and monazite-mixed rare earth tailings in CaO in reducing atmosphere were studied by means of X-ray diffraction (XRD). The results show that the normal products are CeO2, Ce2O3, Ca5F(PO4)3, and Ce0.75Nd0.25O1.875, and there are no REPO4 and REFCO3. Secondly, the roasted product was extracted in HCl, and the relationship among roasting time, roasting temperature, CaO addition, and extraction temperature was studied by the quadratic regression-orthogonal analysis. Through analysis, the optimum process conditions of mixed rare earth tailings extracted are obtained as follows: roasting time of 60 min, roasting temperature of 800 °C, CaO addition of 30 %, extraction temperature of 80 °C, and extraction ratio of 99.18 %.

•(311) plane becomes more ordered with the increase of the magnetic field strength.•Magnetic treatment can change the light absorption performances.•The increase of the polarizability of Si-Onb bond is greater than that of Si–Ob–Si.The current study investigates the effect of strong magnetic field on the micro-structure of pure diopside and diopside doped with Fe3+ or Mn2+. The microstructure changes were characterized by X-ray diffraction (XRD), UV–vis, and Raman spectroscopy. The results of XRD show that the strong magnetic field can increase the peak height of (311) diffraction and the height ratio of (310)/(311) is proportional to the strength of the magnetic field. UV–vis results show that the magnetic treatment and the transition-metal ion doping have some influences on the light absorbance of the diopside samples. With a fixed doping concentration, the UV–Vis absorbance of Fe3+-doped samples decreased after magnetic treatments, however, same UV–Vis absorbance increased for the Mn2+-doped samples. Result from Raman spectra suggests that Raman shift of the maximum peak value changed from 671 cm−1 before the magnetic treatment to 1015 cm−1 after the magnetic treatment. Meanwhile, the Raman intensities at 330 cm−1 and 395 cm−1 become more obvious after the magnetic treatment. The results of this study indicate a minor change in the relative positions among the ions, which then leads to polarizability changes.

Magnetic separation of iron in rare-earth tailings was achieved by magnetizing roast process with coal as reductant. Effects of the temperature, carbon to oxygen ratio, and cooling type on magnetic susceptibility and composition of rare-earth tailings were investigated. The results show that roast conditions with the temperature of 650 °C, carbon to oxygen ratio of 3.85, and holding time of 2.5 h are in favor of reduction of Fe2O3 to Fe3O4 when the roasted rare-earth tailings is cooled along with furnace. Under these roast conditions, magnetic susceptibility of rare-earth tailings is 2.36 that is very close to theoretical value (2.33). However, magnetic separation results of iron in rare-earth tailings cooled along with furnace are not satisfactory. Through comparing magnetic separation results of iron in rare-earth tailings cooled by different ways, it is found that water cooling is more favored of magnetic separation of iron in the roasted rare-earth tailings than furnace cooling and air cooling. Grade and recovery of iron in concentrate from rare-earth tailings cooled by water are 45.00%-49.00% and 65.00%-77.50%, respectively.

•Boric acid and glycerol doped TiO2 on antibacterial activity is firstly investigated.•Doping glycerol, materials have the higher electron–hole separation.•Doping glycerol promote the creation of TiO2 (B) phase.In this study, highly effective boron acid and glycerol co-doped TiO2 nano-materials were directly synthesized via a sol–gel method. The resulting materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrum (FT-IR), UV–vis diffuse reflectance spectroscopy (DRS) and X-ray photoelectron (PL) spectroscopy. The results indicate that boron dopant is partially embedded into the interstitial TiO2 structure or incorporated into the TiO2 lattice through occupying the position of the oxygen atom, and others is present in the form of B2O3. Boron acid and glycerol co-doping TiO2 materials show obvious red shift in their absorption edges and efficient electron–hole separation because of the glycerol doping. The study on the antibacterial activities demonstrate that co-doped TiO2 nano-materials could effectively inactivate the bacteria under visible light irradiation. Co-doped TiO2 nano-materials exhibit more excellent antibacterial performance than B-doped TiO2 nano-materials.

The difference of physicochemical properties among minerals in Baotou rare earth tailings is not significant, which leads to a great difficulty in separation of minerals. In this article, the process of magnetizing roast and low-intensity magnetic separation was used to recover iron. Effect of calcination temperature, holding time and carbon/oxygen ratio on roasting efficiency was investigated. The parameters evaluating magnetizing roast efficiency and theoretical value were determined. X-ray diffraction (XRD) analysis was used to investigate the conversion of Fe phase after roasting. The results show that the best magnetizing roast conditions are calcination temperature of 650 °C, holding time of 2.5 h, and carbon/oxygen molar ratio of 3.85. The best magnetization rate is 2.36, which is close to the theoretical value of 2.33. Based on experiments of low-intensity magnetic separation under different intensities, the best current intensity is 2.0 A to obtain the best separation results. Under the best condition, the concentrate grade of iron is 45.45 % and the recovery of iron is 68.36 %. Most of rare earth, fluorine, and phosphorus are enriched in the magnetic separation tailings. The XRD analysis shows that Fe exists in Fe2O3 before roasting and exists in Fe3O4 after roasting.

We mainly studied the antibacterial properties of perovskite. Its structure was evaluated by X-ray diffractometer (XRD), scanning electron microscope (SEM), and ultraviolet-visible (UV-vis) absorption spectrometer etc. The antibacterial properties of perovskite to Candida albicans (ATCC10231), Escherichia coli (ATCC25922) and Staphylococcus aureus (ATCC6538) were investigated by the flask oscillation method. The results show that the perovskite has strong antibacterial ability, and continued antibacterial properties; its sterilization rates are 87.00%, 99.50%, 96.22% respectively to these three bacteria.