Recently, Pt-loaded graphic carbon nitride (g-C₃N₄) materials have attracted great attention as a photocatalyst for hydrogen evolution from water. The simple surface modification of g-C₃N₄ by hydrothermal methods improves photocatalytic performance. In this study, ethanol is used as a solvothermal solvent to modify the surface properties of g-C₃N₄ for the first time. The g-C₃N₄ is thermally treated in ethanol at different temperatures (T = 140 °C, 160 °C, 180 °C, and 220 °C), and the Pt co-catalyst is subsequently deposited on the g-C₃N₄ via a photodeposition method. Elemental analysis and XPS O 1s data confirm that the ethanol solvothermal treatment increased the contents of the oxygen-containing functional groups on the g-C₃N₄ and were proportional to the treatment temperatures. However, the XPS Pt 4f data show that the Pt²⁺/Pt⁰ value for the Pt/g-C₃N₄ treated at ethanol solvothermal temperature of 160 °C (Pt/CN-160) is the highest at 7.03, implying the highest hydrogen production rate of Pt/CN-160 is at 492.3 μmol g⁻¹ h⁻¹ because the PtO phase is favorable for the water adsorption and hydrogen desorption in the hydrogen evolution process. In addition, the electrochemical impedance spectroscopy data and the photoluminescence spectra emission peak intensify reflect that the Pt/CN-160 had a more efficient charge separation process that also enhanced the photocatalytic activity.

Co-doped NiTiO₃/g-C₃N₄ composite photocatalysts were prepared by a modified Pechini method to improve their photocatalytic activity toward methylene blue photodegradation under visible light irradiation. The combination of Co-doped NiTiO₃ and g-C₃N₄ and Co-doping into the NiTiO₃ lattice synergistically enhanced the photocatalytic performance of the composite photocatalysts. X-ray photoelectron spectroscopy results for the Co-doped NiTiO₃/g-C₃N₄ composite photocatalysts confirmed Ti-N linkages between the Co-doped NiTiO₃ and g-C₃N₄. In addition, characteristic X-ray diffraction peaks for the NiTiO₃ lattice structure clearly indicated substitution of Co into the NiTiO₃ lattice structure. The composite structure and Co-doping of the C-x composite photocatalysts (x wt % Co-doped NiTiO₃/g-C₃N₄) not only decreased the emission intensity of the photoluminescence spectra but also the semicircle radius of the Nyquist plot in electrochemical impedance spectroscopy, giving the highest k_app value (7.15 × 10⁻³ min⁻¹) for the C-1 composite photocatalyst.

In this study, we synthesized Pt/g-C₃N₄ photocatalysts modified by a solvent etching process where ethanol (Pt/CN0), water (Pt/CN100), and a 50:50 mixture (Pt/CN50) were used as a solvent, and investigated the optimal properties of g-C₃N₄ to prepare the best Pt/g-C₃N₄ for photocatalytic hydrogen evolution. From diverse characterizations, water was proven to be a stronger solvent agent, resulting in not only the introduction of more O-functional groups onto the g-C₃N₄ surface, but also the degradation of a regular array of tri-s-triazine units in the g-C₃N₄ structure. While the addition of O-functional groups positively influenced the oxidation state of the Pt cocatalyst and the hydrogen production rate, the changes to g-C₃N₄ structure retarded charge transfer on its surface, inducing negative effects such as fast recombination and less oxidized Pt species. Pt/CN50 that was synthesized with the 50:50 solvent mixture exhibited the highest hydrogen production rate of 590.9 µmol g⁻¹h⁻¹, while the hydrogen production rates of Pt/CN0 (with pure ethanol solvent) and Pt/CN100 (with pure water solvent) were 462.7, and 367.3 µmol g⁻¹h⁻¹, respectively.

Mineral liberation for flotation is inherently a three-dimensional (3D) surface property, yet it is conventionally quantified using sectional measurements from SEM (X-ray back-scattering, inherently 2D) based Mineral Liberation Analysis (MLA). This dimensional mismatch has rarely been critically examined. Here, we explicitly contrast the volumetric resolving capability of X-ray computed tomography (XCT) with the intrinsic 2D nature of SEM backscattered imaging to reassess liberation in flotation of coarse and composite sulphides. A bornite-rich ore was separated into two coarse fractions (–300+212 µm and –212+150 µm) and floated in a Hallimond tube. Feed and products were characterised by both MLA and XCT. While MLA quantified 2D areal sulphide fractions from polished sections, XCT reconstructed full particle volumes and directly measured exposed sulphide surface area, which is the physically relevant attribute controlling bubble–particle attachment. MLA systematically overestimated high-grade classes due to stereological bias, misclassifying composite particles with limited external exposure as liberated. In contrast, XCT revealed a threshold-controlled flotation response: particles with 65% behaved as effectively liberated. Flotation rate constants correlated strongly with 3D surface exposure but were dispersed when expressed as 2D sectional grades. These results demonstrate that liberation is fundamentally a 3D surface accessibility problem and that XCT-derived surface exposure provides a physically consistent descriptor of coarse composite particle flotation, exposing the inherent dimensional limitation of traditional 2D MLA metrics.

Mineral liberation for flotation is inherently a three-dimensional (3D) surface property, yet it is conventionally quantified using sectional measurements from SEM (X-ray back-scattering, inherently 2D) based Mineral Liberation Analysis (MLA). This dimensional mismatch has rarely been critically examined. Here, we explicitly contrast the volumetric resolving capability of X-ray computed tomography (XCT) with the intrinsic 2D nature of SEM backscattered imaging to reassess liberation in flotation of coarse and composite sulphides. A bornite-rich ore was separated into two coarse fractions (–300+212 µm and –212+150 µm) and floated in a Hallimond tube. Feed and products were characterised by both MLA and XCT. While MLA quantified 2D areal sulphide fractions from polished sections, XCT reconstructed full particle volumes and directly measured exposed sulphide surface area, which is the physically relevant attribute controlling bubble–particle attachment. MLA systematically overestimated high-grade classes due to stereological bias, misclassifying composite particles with limited external exposure as liberated. In contrast, XCT revealed a threshold-controlled flotation response: particles with 65% behaved as effectively liberated. Flotation rate constants correlated strongly with 3D surface exposure but were dispersed when expressed as 2D sectional grades. These results demonstrate that liberation is fundamentally a 3D surface accessibility problem and that XCT-derived surface exposure provides a physically consistent descriptor of coarse composite particle flotation, exposing the inherent dimensional limitation of traditional 2D MLA metrics.