In this paper, the effects of CaO on the phase evolution mechanism of vanadium slag during slagging, direct roasting, and (NH₄)₂CO₃ leaching processes are investigated. Results indicate that with the increase in CaO content, vanadium is always concentrated as (Fe, Mn, Mg)V₂O₄ in spinels, part of titanium is concentrated and transformed into CaTiO₃, and phosphorus is concentrated in 3CaO·P₂O₅ (C₃P) and transformed into n·2CaO·SiO₂-3CaO·P₂O₅ (nC₂S-C₃P). During the direct roasting process, a part of the vanadium-containing spinel phase oxidizes and reacts with Ca₂SiO₄ to produce calcium vanadate (Ca₃V₂O₈, Ca₁₀V₆O₂₅, and Ca₂V₂O₇), which is soluble in (NH₄)₂CO₃ aqueous solution. However, a part of the vanadium-containing spinel phase is oxidized and decomposed to vanadium oxides (V₂O₅ and V₆O₁₃), which are insoluble in (NH₄)₂CO₃ aqueous solution. This is not beneficial for vanadium extraction using (NH₄)₂CO₃ aqueous solution. In addition, (NH₄)₂CO₃ aqueous solution can restrain the leaching of C₃P from the nC₂S-C₃P solid solution in the directly roasted vanadium slag with high CaO content.

The use of a layered Li₂SnO₃ material as an efficient photocatalyst for the degradation of environmental pollutants (Rhodamine B and tetracycline) was investigated. The structure and morphology of the material were characterized using powder X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy. Optical measurements demonstrated that Li₂SnO₃ was a UV-light-responsive material with a band gap of 3.71 eV. The maximum kinetic rate constants of photocatalytic degradation of Rhodamine B and tetracycline solutions were 0.0155 min⁻¹ and 0.0406 min⁻¹ $·$ L/mg, respectively, when exposed to UV-light irradiation within 120 min. Trapping experiments demonstrated that holes $(h^{+})$ , hydroxyl radical $\left(·OH\right)$ and superoxide radical $\left(·{\mathit{O}}_{\mathbf{2}}^{-}\right)$ were the dominant active species during the degradation of Rhodamine B and tetracycline. Theoretical band structure calculations revealed that Li₂SnO₃ was a direct gap semiconductor with a large ${\mathit{m}}_{\mathit{h}}^{*}/{\mathit{m}}_{\mathit{e}}^{*}$ value (4.7) near the band edge. Partial charge density near the top of the valence band indicated that the photocatalytic oxidation reaction occurred largely on the O-2p states. The excellent photocatalytic performance was attributed to the synergistic effect of the layered crystal structure and large ${\mathit{m}}_{\mathit{h}}^{*}/{\mathit{m}}_{\mathit{e}}^{*}$ . This work represents an important contribution to the design and optimization of efficient oxide photocatalysts with layered crystal structures for environmental remediation.

The Chengdu–Chongqing Economic Circle (CCEC) represents a key regional development initiative in China. University research collaboration plays a vital role in advancing its innovation ecosystem and supporting sustainable growth. This study examines inter-university collaboration among 47 public universities in the CCEC based on 53,968 co-authored publications from 2005 to 2024. Using bibliometric and visualization techniques in CiteSpace 6.4.R2, it explores the structure and evolution of collaboration from institutional, thematic, and author perspectives. The results reveal a steady expansion of collaborative activities driven by national innovation strategies. Leading institutions such as Sichuan University, UESTC, and Chongqing University act as central hubs connecting diverse research communities. Collaboration has diversified from traditional fields toward interdisciplinary areas including materials, environmental science, and applied mathematics. Author networks are becoming more cohesive, reflecting stronger knowledge integration across universities. The study highlights how policy-driven collaboration fosters regional innovation capacity and provides evidence-based insights for strengthening university networks and advancing the CCEC’s role as a science and technology innovation hub in western China.