Isothermal section of Ti-Nb-Sn at 1173 K was experimentally studied by back-scattered electron, electron probe microanalysis and X-ray diffraction analysis. Solid solution phase β(Ti, Nb), liquid Sn and eight intermetallic compounds Ti₃Sn, Ti₂Sn, Ti₅Sn₃, Ti₆Sn₅, Nb₆Sn₅, Nb₃Sn, Ti₃Nb₂Sn₂ and Ti₃NbSn coexisted. Four ternary phase regions Ti₃Sn + Ti₃NbSn + β(Ti, Nb), Ti₃NbSn + Ti₃Nb₃Sn₂ + Ti₃Sn, Ti₂Sn + Ti₃Sn + Ti₃Nb₃Sn₂ and Ti₆Sn₅ + Ti₃Nb₃Sn₂ + Nb₃Sn were experimented. In addition, the proper composition range of the single phase was suggested. All the detected Ti-Sn and Nb-Sn compounds have a remarkable solubility along the isoconcentration of Sn. β(Ti, Nb) has a relatively large solution while liquid Sn has a little in the isothermal section.

To solve the problem of methyl orange (MO) dye wastewater pollution, TiO ₂ –montmorillonite composite (TiO ₂ –MMT) and Bi ₂₀ TiO ₃₂ –montmorillonite composite (Bi ₂₀ TiO ₃₂ –MMT) were synthesised by the sol–gel method, and they were used for photocatalytic degradation of MO solution. The results showed that TiO ₂ in TiO ₂ –MMT existed as the anatase type, and Bi ₂₀ TiO ₃₂ in Bi ₂₀ TiO ₃₂ –MMT existed as the tetragonal crystal type. When the dosage of the composite was 0.50 g/l, the initial concentration of the MO solution was 20 mg/l, and the pH was 3, the decolourisation rate of MO solution using TiO ₂ –MMT treating was 87.11%, and it reached 98.50% after Bi ₂₀ TiO ₃₂ –MMT treating. When Bi ₂₀ TiO ₃₂ –MMT was reused four times, the decolourisation rate of the MO solution was only reduced by 3.5%. The photocatalytic degradation between MO solution and Bi ₂₀ TiO ₃₂ –MMT complied with the pseudo‐first‐order kinetic equation. Holes and superoxide radicals interacted directly with MO during photocatalytic degradation, which reduced the probability of hole–electron recombination, and improved the photocatalytic degradation property of Bi ₂₀ TiO ₃₂ –MMT. Bi ₂₀ TiO ₃₂ –MMT has excellent stability property, which makes it a good composite in the treatment of dye wastewater.

The comprehensive utilization of phosphogypsum, phosphorus tailings, and blast-furnace slag is of great significance to environmental protection, resource conservation, and economic development. This study utilized phosphogypsum-blast furnace slag cold-bonded aggregate (PBCA) as the aggregate; β-hemihydrate phosphogypsum (β-HPG), blast furnace slag (BS), and phosphate tailings (PT) as raw materials; along with polycarboxylate superplasticizer (PS) and vinyl acetate-ethylene copolymer re-dispersible latex powder (EVA) as admixtures to produce phosphogypsum-blast furnace slag-phosphorus tailings unburned bricks (PBPB). The mechanical properties of the unburned bricks were optimized through single-factor experiments. Ca(OH)₂ is formed from CaO and water in blast-furnace slag and cement, and Ca(OH)₂ reacts with silica-aluminum oxide to form calcium silicate, calcium aluminate, and calcium aluminosilicate, which strengthens the unburned bricks. The study found that with a ratio of β-HPG: BS = 8:2, a polycarboxylate superplasticizer content of 0.9 wt%, an EVA content of 1.5 wt%, and phosphate tailings and PBCA contents of 10 wt% and 80 wt%, respectively, the 28-day strength of unburned bricks reached 24.3 MPa. XRD and SEM analyses revealed that the hydration products primarily consisted of gypsum, ettringite, and hydrated calcium silicate (C-S-H gel), which increase the compactness of the blocks and thus improve the strength.