To address the environmental pollution caused by nitrogen oxides, V₂O₅-WO₃/TiO₂ is widely used as a catalyst based on selective catalytic reduction (SCR) technology. However, spent SCR catalysts pose a potential hazard to the environment due to the presence of heavy metals. This problem continues to plague countries with predominantly thermal power generation, and landfills as the dominant disposal method wastes significant metal resources. Previous research into the recovery of these metal resources has received considerable attention. Here, we summarise the methods of recovery and find that research trends are beginning to move towards improving the added value of recovered products. One very promising application is photocatalysts; however, the atomic efficiency of current methods is not satisfactory. Therefore, this review first focuses on the regeneration of spent SCR catalysts and the processes used for elemental extraction to clarify what forms of V, W and Ti can be obtained from existing processes. This is followed by providing directions for the conversion of spent SCR catalysts into photocatalysts with improvements based on such processes. From a different perspective, this also provides a new resource for photocatalysts and is expected to significantly reduce the cost of photocatalyst production.

Due to the severe harmful impacts of industrial dyeing wastewater on ecosystems and human health, proper treatment is crucial. Herein, the use of modified graphite as an adsorbent for dyeing wastewater treatment was investigated in this study. The graphite was oxidized and intercalated using a phosphoric acid–nitric acid–potassium permanganate system and then thermally treated at high temperatures to optimize its structure. By adjusting the thermal treatment temperature, the graphite adsorbent with varying porosity was obtained. The optimized graphite demonstrated significant improvement in adsorption performance for dyes and organic compounds, achieving a removal rate of over 85% for methylene blue (MB) dye. The optimal adsorption performance is achieved with a 1.6 mg modified graphite adsorbent at 60 °C under alkaline conditions for adsorbing 10 ppm MB. Adsorption kinetics and isotherm models were applied to elucidate the adsorption mechanisms. The results fit the Langmuir model, suggesting that monolayer homogeneous adsorption is favorable. Importantly, the results demonstrate that high-temperature treatment can significantly enhance the adsorption properties of coal-based graphite, supporting its application in dyeing wastewater treatment.

Modified microspheres (SiO₂-M) were obtained by the hydrolytic modification of silicon dioxide (SiO₂) microspheres with Na₂SiO₃, and then, SiO₂-M was used as a carrier to prepare a composite photocatalyst (SiO₂-M/TiO₂) using the sol-gel method; i.e., nano-TiO₂ was loaded on the surface of SiO₂-M. The structure, morphology, and photocatalytic properties of SiO₂-M/TiO₂ were investigated. Besides, the mechanism of the effect of SiO₂-M was also explored. The results show that the hydrolytic modification of Na₂SiO₃ coated the surface of SiO₂ microspheres with an amorphous SiO₂ shell layer and increased the quantity of hydroxyl groups. The photocatalytic performance of the composite photocatalyst was slightly better than that of pure nano-TiO₂ and significantly better than that of the composite photocatalyst supported by unmodified SiO₂. Thus, increasing the loading capacity of nano-TiO₂, improving the dispersion of TiO_2, and increasing the active surface sites are essential factors for improving the functional efficiency of nano-TiO₂. This work provides a new concept for the design of composite photocatalysts by optimizing the performance of the carrier.

Superhydrophobic coatings with intelligent properties have attracted much attention because of their wide application in many fields. However, there is a limited amount of literature on superhydrophobic coatings whose wettability and adhesion can be adjusted by UV irradiation and calcination at the same time. In this study, amorphous SiO₂ microspheres (A-SiO₂) and nano-TiO₂ particles (N-TiO₂) were used to fabricate A-SiO₂/N-TiO₂ composites by wet grinding, and then, they were modified with polydimethylsiloxane (PDMS) and sprayed onto substrate surfaces to obtain a tunable adhesive superhydrophobic A-SiO₂/N-TiO₂@PDMS coating. It is worth noting that the wettability and adhesion of the coating to water droplets could be adjusted by UV irradiation and calcination. The mechanisms of the aforementioned phenomena were studied. Moreover, methyl orange solution could be degraded by the coating due to its photocatalysis. The as-prepared coating had good adaptation to different substrates and outdoor environments. Moreover, the surfaces of these coatings exhibited the same liquid repellency towards different droplets. This research provides an environmental strategy to prepare advanced self-cleaning coatings.