Sigma 500 scanning electron microscope

Cylindrical 3D printed Ti6Al4V porous scaffolds, which was 6 mm diameter and 8 mm height, with pre-designed pore sizes about 600 μm and porosity about 70 % were manufactured layer-by-layer by an EBM system (Arcam Q10, Sweden). Briefly, the 3D model date was designed and imported into the UG NX6.0 system (Unigraphics Solutions, US). Medical-graded Ti6Al4V powder with an average diameter of 45–105 μm were used as basic material. The maximum scanning speed of electron beam was 8000 m s^− 1 and the accuracy of printing is ± 0.4 mm. Finally, all samples were cleaned in Powder Recovery System and washed in acetone, ethanol, and distilled water with ultrasonic machine in turn for 30 min, respectively, before cell experiments and animal procedures [29 ].
To demonstrate whether the parameters of the prepared scaffolds, such as pore size and porosity, are the same as those of the pre-designed model, we performed characterization tests on the scaffolds. The porosity of prepared porous scaffolds was measured by a SkyScan 1076 scanner Microcomputed Tomography (Micro-CT, Bruker, Kontich, Belgium). In addition, in order to detect the average pore diameter of these Ti6Al4V scaffolds, the microstructure of samples was photographed by a SIGMA500 scanning electron microscope (SEM, ZEISS, Oberkochen, Germany), and pictures were quantitative analysis by Image J software (NIH, Bethesda, MD, USA).

Based on the electrode method (HJ 1147-2020), a PHS-3C pH meter was used to measure pH values. The oxidation-reduction potential (ORP) was measured with a CT-8022 ORP meter. Electrical conductivity (Ec) was measured with a pen-type Ec meter. The OD₆₀₀ value was measured with a V-1600PC visible spectrophotometer. Based on the barium chromate spectrophotometry (HJ/T 342-2007), the concentration of ${\text{SO}}_4^{2-}$ was determined by a V-1600PC visible spectrophotometer. Based on the atomic absorption spectrophotometry (GB 7475-87), the concentrations of Cu, Zn, Pb, and Cd were determined by a Z-2000 flame atomic spectrophotometer. The elements of Fe and Mn were determined by flame atomic absorption spectrophotometry (GB 11911-89). Cr was determined by flame atomic absorption spectrophotometry (HJ 757-2015).
Zeiss Sigma 500 scanning electron microscope was used to detect the tailings by SEM, and EDS scanning energy spectrometer was used to detect the chemical substances on the surface of the samples. The tailing sand samples were ground to 200 mesh, and XRD detection was conducted. The scanning step for XRD detection with Bruker D8 Advance X-ray diffractometer was 5–90°.