The discharge of organic pollutants by the textile and dyeing industries presents an escalating threat to aquatic environments, necessitating the development of effective remediation strategies. This study introduces the utilization of graphite-like structured activated carbon (AC), derived from highland barley straw-a biomass unique to the Plateau regions of China, including Tibet, Qinghai, and Gansu-as a support material for the TiO₂ catalyst. TiO₂/AC composites with different TiO₂ loadings were synthesized by ultrasonic impregnation. The TiO₂/AC composites were found to be polycrystalline materials composed of anatase and rutile phases. The TiO₂ nanoparticles are well-dispersed over the surface of the AC. The photocatalytic activity of these composites was evaluated through their capacity to degrade a methylene blue (MB) solution upon irradiation. It was observed that the inclusion of TiO₂ increases the number of adsorption sites and active sites for methylene blue, with the photocatalytic activity being notably higher at a 3-wt% TiO₂ loading, achieving a remarkable 99.6 % degradation efficiency for 100 mg/L MB within 100 min. The experimental kinetic data for the photocatalytic process follow the pseudo-first-order kinetic model. Furthermore, TiO₂/AC retains high photocatalytic activity after five reaction cycles. This research provides valuable insights into the application of biomass-derived materials for the purification of water, offering a sustainable solution to both pollution and agricultural waste challenges in Plateau areas of China.

There has been increasing concern over water pollution, which poses a threat to human life and health. Absorption by low-cost absorbents is considered to be a cost-effective and efficient route. However, the non-reusability of absorbents greatly limits their applications. In this study, a novel vermiculite/TiO₂ composite combining the inexpensive absorbent with the commonly used photocatalyst was firstly synthesized via the sol-gel method. On the one hand, the organic pollutants are absorbed by vermiculite and then decomposed through the photocatalysis process, enabling the next round of absorption and creating an absorption–decomposition reusable cycle. On the other hand, the modulation effect of optical and electronic structure on the prepared TiO₂ photocatalyst by the vermiculite incorporation could significantly improve the photocatalytic activity and eventually enhance the aforementioned cyclic degradation capacity. The layer-structured vermiculite (Vt) supports a uniform coverage of TiO₂ at an optimized ratio, providing an optimal adsorption environment and contact area between the photocatalyst and methylene blue (MB) molecules. Vt/TiO₂ heterojunction is formed with Si-O-Ti bonding, at which electrons transfer from Vt to TiO₂, enriching electron density in TiO₂ and favoring its photocatalytic activity. Furthermore, the incorporation of Vt increases the light absorption of TiO₂ in the visible range by narrowing the optical band gap to 1.98 eV, which could promote the generation of photo-excited carriers. In addition, PL measurements revealed that the carrier recombination is substantially suppressed, and the charge separation and migration are greatly enhanced by a factor of 3. As a result, the decomposition rate of MB is substantially increased 5.3-fold, which is ascribed to the synergistic effects of the elevated photocatalysis and the large absorption capacity governed by the chemisorption mechanism of the intra-particle diffusion. These results pave the way for composite design towards efficient, economical, and pragmatic water pollution treatment.

We reported anchoring mesoporous silica onto the microporous metal–organic frameworks (MOF) (UiO-66-NH₂) to obtain a hierarchical porous framework (UiO-66-NH₂@SiO₂). This strategy maintains the high specific surface area (SA) of the MOF and addresses the mass transfer issue frequently encountered in microporous materials, providing more possibilities for subsequent modified structural frameworks. The structural characteristics of UiO-66-NH₂@SiO₂ were evaluated by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, surface analysis and X-ray photoelectron spectroscopy. In this work, the specific SA of the composite material was 196.667 m²/g, which decreased due to the occupation of some pores by anchored silica. Adsorption experiments showed that the composite material had a better adsorption effect (Congo red, 393.83 mg/g; bromophenol blue, 446.46 mg/g) than UiO-66-NH₂, with electrostatic interaction and hydrogen bonding being the main driving forces. Therefore, this is a material that has a positive impact on dye adsorption. The strategy proposed in this work has potential applications not only in the construction of new materials but also in the exploration of dye adsorbents.