This study employed TC4 rod as raw material to fabricate TC4 powders for laser 3D printing via electrode induction melting gas atomization (EIGA). The morphologies, phase compositions, particle size distributions, apparent densities and flowabilities of the powders were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), laser particle size analyzer (LPS) and Hall flowmeter, respectively. Moreover, the effects of gas atomization pressure and melting temperature on the yield of TC4 powders for laser 3D printing were studied. The results showed that TC4 powders morphology was nearly regular spherical. The particle size of TC4 powders showed a single peak normal distribution, mainly distributed in the range of 15−180 μm. The powder was α’−Ti of a single phase solid solution. The optimum parameters were gas atomization pressure of 5MPa, melting temperature of 1750°. Under the optimized condition, the average particle size D50 was 60.2 μm, the yield of printable TC4 powders was 35.6%, the flowability was 41.2 s/50g, the apparent density was 2.76 g/cm3 and oxygen content was 800 ppm, which was in line with the ASTM test standard and was conformed to the requirement for laser 3D printing.

Selective laser melting (SLM) currently uses the micro-fine spherical powder prepared by gas atomisation as a raw material. However, the spherical powder is expensive. In order to reduce the cost, this study first ball mills the pure titanium (CP-Ti) powder of hydrogenation-dehydrogenation (HDH). At a high speed and within a short period, the particle size distribution of the powder at a high rotation speed for 15 min is 12-45 μm with an angle of repose 34.3°. Then, the ball milling of titanium was mixed spherical powder with a wide grain size range up to 100 μm. This study presents the results of using SLM to produce CP-Ti parts starting from powder with mixed powder, in a different ratio between modified powder and spherical powder. The ultimate tensile strength (UTS) of SLM-parts of 8:2 ratio has been improved to 507 MPa, and the UTS of parts of 7:3 ratio has been improved to 522 MPa.

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In the present study, a process of separating high-quality TiO2 from an oxalic-acid leachate of vanadium slag was proposed. It consists of two steps; oxalic acid was firstly recovered from the leachate by the cooling-crystallization method, and subsequently TiO2 was separated from the oxalic-acid recovered leachate by the hydrothermal precipitation method. The experimental results indicate that oxalic acid can be recovered from the leachate by cooling crystallization at 5 °C, and after the recovery of oxalic acid, the purity of final TiO2 product can also be improved. For example, when the leachate was cooled directly at 5 °C for 5 h, about 7% of oxalic acid was recovered, and the purity of final TiO2 product improved from 95.7% to 96.6%. Furthermore, it was found that when some HCl solution was added to the leachate, both the recovery percentage of oxalic acid and the purity of TiO2 product increased. For instance, when 15 vol% of HCl solution relative to pregnant leachate was added, about 35% oxalic acid was recovered by cooling crystallization at 5 °C for 3 h, and the anatase TiO2 product with a purity of 99.2% was obtained by hydrothermal precipitation at 140 °C for 2.5 h.

Microbial fuel cells (MFC) have considerable potential in the field of energy production and pollutant treatment. However, a low power generation performance remains a significant bottleneck for MFCs. Biochar and anatase are anticipated to emerge as novel cathode catalytic materials due to their distinctive physicochemical properties and functional group architectures. In this study, biochar was utilized as a support for an anatase cathode to investigate the enhancement of the MFC power generation performance and its environmental impact. The results of the SEM and XPS experiments showed that the biochar-supported anatase composites were successfully prepared. Using the new cathode catalyst, the maximum current density and power density of the MFC reached 164 mA/m2 and 10.34 W/m2, respectively, which increased by 133% and 265% compared to a graphite cathode (70.51 mA/m2 and 2.83 W/m2). The degradation efficiency of Cr (VI) was 3.1 times higher in the biochar-supported anatase MFC than in the graphite cathode. The concentration and pH gradient experiments revealed that the degradation efficiency of Cr (VI) was 97.05% at an initial concentration of 10 mg/L, whereas a pH value of two resulted in a degradation efficiency of 94.275%. The biochar-supported anatase composites avoided anatase agglomeration and provided more active sites, thus accelerating the cathode electron transfer. In this study, natural anatase and biochar were ingeniously combined to fabricate a green and efficient electrode catalyst, offering a novel approach for the preparation of high-performance positive catalysts as well as a sustainable, economical, and environmentally friendly method for Cr (VI) removal in aqueous solutions.