This study describes the use of bentonite in suspension for the caffeine adsorption (pollutant of emerging concern) by taking different conditions of the pH, adsorbent mass, adsorbent calcination temperature and interferents into account. The results were compared with those obtained using bentonite immobilized in alginate beads. The acid medium has a greater efficiency for the caffeine adsorption and the adsorbent calcination temperature exerts, due to structural changes. Caffeine removal higher than 90% was obtained at optimized conditions. The Langmuir model indicated a better fit of the data and the adsorption capacity of caffeine onto bentonite. The bentonite immobilized led to a slower adsorption process in relation to the suspended.

In the present work, the performance of Ag/ZnO/CoFe2O4 magnetic photocatalysts in the photocatalytic degradation of ibuprofen (IBP) was evaluated. This study considered the use of pure Ag/ZnO (5% Ag) and also the use of the Ag/ZnO/CoFe2O4 magnetic catalysts containing different amounts (5, 10 and 15% wt) of cobalt ferrite (CoFe2O4). The catalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoacoustic spectroscopy. To carry out the photocatalytic degradation reaction, different concentrations of the ibuprofen contaminant solution (10, 20 and 30 ppm) and different concentrations of photocatalyst were tested (0.3 g L−1, 0.5 g L−1 and 1.0 g L−1). The reaction parameters studied were: IBP concentration, catalyst concentration, adsorption and photolysis, influence of the matrix, radiation source (solar and artificial) and the effect of organic additive. At the end of the photocatalytic tests, the best operating conditions were defined. Considering the obtained results of degradation efficiency and magnetic separation, the optimal parameters selected to proceed with the other tests of the study were: ibuprofen solution concentration 10 ppm, Ag/ZnO/CoFe2O4 (5%) catalyst at a concentration of 0.3 g L−1 and pH 4.5 of the reaction medium. The results indicated the feasibility of magnetic separation of the synthesized catalysts. A long duration test indicated that the catalyst exhibits stability throughout the degradation reaction, as more than 80% of IBP was degraded after 300 minutes. The photocatalytic activity was directly affected by the ferrite load. The higher the nominal load of ferrite, the lower the performance in IBP degradation. It was also observed that the smallest amount of ferrite studied was enough for the catalyst to be recovered and reused. The adsorption and photolysis tests did not show significant results in the IBP degradation. In addition, it was possible to verify that the aqueous matrix, the use of solar radiation and the addition of additive (acid formic) were interfered directly in the process. The catalyst reuse tests indicated that it can be recovered and reused at least three times without considerable catalytic activity loss.

In the present work, rock dust was evaluated as an adsorbent and heterogeneous photocatalyst in the discoloration of Basazol Yellow 46 L dye, which is widely used in the dyeing of molded pulp packages. Although rock dust is produced in large quantities in quarries as a byproduct of rock exploration, little is known about its application as a photocatalyst. Rock dust was characterized by XRD, SEM/EDS, photoacoustic spectroscopy, and N₂ physisorption and had its photocatalytic activity assessed through phenol and salicylic acid degradation tests. The characterization results showed that the rock dust is mainly composed of silica and alumina in a triclinic structure, has a bandgap energy of 2.36 eV, and has a specific area of 1.5 m²/g. Rock dust was proven to be photocatalytically active in phenol and salicylic acid degradation tests and also presented the adsorptive and photocatalytic capacity for the discoloration of effluent containing Basazol Yellow 46 L dye.

Postharvest deterioration caused by ethylene (C₂H₄) is a major challenge for global food security, leading to significant losses of perishable products like bananas. In this study, we present the synthesis and optimization of a multicomponent photocatalyst based on montmorillonite (MMT), titanium dioxide (TiO₂), and silver (Ag), designed for efficient ethylene remediation. The catalysts were prepared via wet impregnation and characterized using FE-SEM, EDS, and UV–vis reflectance spectroscopy, which confirmed the successful integration of components and a homogeneous elemental distribution. The bandgap energies were determined to be in the range of 3.02 to 4.10 eV, with MMT-rich samples showing values around 3.12 eV. Through a 2³ factorial design, the performance was evaluated under three distinct scenarios: adsorption, artificial UV photocatalysis, and natural sunlight-driven photocatalysis. Sample Amt 09 (1.5% TiO₂ and 1% Ag) achieved an ethylene removal of over 92% in the artificial UV photocatalysis scenario. Sample Amt 10 (5% MMT, 1.5% TiO₂, and 1% Ag) stood out with high performance across all scenarios, suggesting synergistic effects between adsorption and catalytic degradation. Furthermore, an optimized formulation (5% MMT and 2.73% TiO₂) achieved 65% ethylene removal under UV light and 47% under natural sunlight. These findings highlight the potential of MMT/TiO₂/Ag composites as sustainable, light-driven solutions for postharvest management, offering a scalable platform to extend the shelf life of fresh produce and reduce global food waste.