RESUMO
The ubiquity and impact of pharmaceuticals and pesticides, as well as their residues in environmental compartments, particularly in water, have raised human and environmental health concerns. This emphasizes the need of developing sustainable methods for their removal. Solar-driven photocatalytic degradation has emerged as a promising approach for the chemical decontamination of water, sparking intensive scientific research in this field. Advancements in photocatalytic materials have driven the need for solar reactors that efficiently integrate photocatalysts for real-world water treatment. This study reports preliminary results from the development and evaluation of a solar system for TiO2-based photocatalytic degradation of intermittently flowing water contaminated with doxycycline (DXC), sulfamethoxazole (SMX), dexamethasone (DXM), and carbendazim (CBZ). The system consisted of a Fresnel-type UV solar concentrator that focused on the opening and focal point of a parabolic trough concentrator, within which tubular quartz glass reactors were fixed. Concentric springs coated with TiO2, arranged one inside the other, were fixed inside the quartz reactors. The reactors are connected to a raw water tank at the inlet and a check valve at the outlet. Rotating wheels at the collector base enable solar tracking in two axes. The substances (SMX, DXC, and CBZ) were dissolved in dechlorinated tap water at a concentration of 1.0 mg/L, except DXM (0.8 mg/L). The water underwent sequential batch (~ 3 L each, without recirculation) processing with retention times of 15, 30, 60, 90, and 120 min. After 15 min, the degradation rates were as follows: DXC 87%, SMX 35.5%, DXM 32%, and CBZ 31.8%. The system processed 101 L of water daily, simultaneously removing 870, 355, 256, and 318 µg/L of DXC, SMX, DXM, and CBZ, respectively, showcasing its potential for real-world chemical water decontamination application. Further enhancements that enable continuous-flow operation and integrate highly effective adsorbents and photocatalytic materials can significantly enhance system performance.
Assuntos
Fotoquímica , Energia Solar , Poluentes Químicos da Água , Purificação da Água , Água , Catálise/efeitos da radiação , Água/química , Purificação da Água/instrumentação , Purificação da Água/métodos , Humanos , Poluentes Químicos da Água/química , Poluentes Químicos da Água/isolamento & purificação , Doxiciclina/química , Doxiciclina/isolamento & purificação , Sulfametoxazol/química , Sulfametoxazol/isolamento & purificação , Dexametasona/química , Dexametasona/isolamento & purificação , Quartzo , Cromatografia , Temperatura , Fatores de Tempo , Animais , Abastecimento de ÁguaRESUMO
A bench-scale tubular photo-reactor was built to evaluate the solar-driven TiO2-based photocatalytic degradation of synthetic polluted water samples. The reactor was designed as a compound-parabolic-collector and operated in batch mode using TiO2 P25 immobilized on a bed of pumice. The immobilization of TiO2 on pumice was carried out using a facile dip impregnation method followed by heat treatment. The obtained material was characterized by SEM, EDS, XRD, and nitrogen adsorption. It was possible to impregnate up to 68.5 mg of TiO2 per gram of pumice stones of 8-14 mm. Conversions of up to 35-40 and 62-69%, after 4 h of treatment and UV doses of 20.8 ± 3.5 kJ L-1, were achieved when the catalyst was used immobilized on pumice stone and in the form of a suspension, respectively. The stability and reusability of the catalyst-coated support was tested through a series of consecutive photocatalytic experiments. After four consecutive runs, the immobilized catalyst showed a decrease in its photoactivity leading to removal levels of 23%.
Assuntos
Titânio , Poluentes Químicos da Água , Catálise , Silicatos , ÁguaRESUMO
Advanced oxidation processes based on ozonation, UV solar radiation, hydrogen peroxide, and persulfate were tested for the complete treatment of a specific landfill leachate. As a post-treatment of the advanced oxidation process, an additional adsorption process was carried out using a natural zeolite. Application of the UVsolar/O3/H2O2 process required 140â¯min of irradiation and the consumption of 0.67â¯g/L H2O2 to eliminate 56% and 17% of colour and chemical oxygen demand (COD), respectively. When adding persulfate to the system (UVsolar/O3/H2O2/S2O8-2), colour and COD were reduced by 29% and 77%, respectively, with a 0.2â¯g/L concentration of S2O8-2 requiring 250â¯min of irradiation time. In an experimental run with landfill leachate, adsorption post-treatment with a natural zeolite resulted in 36%, 99%, and 18% total reductions in COD, ammonium, and chloride, respectively. In another experimental run, adsorption with a zeolite was used as a pre-treatment for the advanced oxidation process (UVsolar/O3/H2O2 and UVsolar/O3/H2O2/S2O8-2). The results were similar to those for adsorption post-treatment, with 30%, 90%, and 20% total reductions in COD, ammonium, and chloride, respectively. Despite improvements, some measured parameters of treated landfill leachate still exceeded Chilean regulations for water quality. Furthermore, Lactuca sativa seeds did not germinate after irrigation with 100% treated landfill leachate or dilutions above 3%. Finally, EC50 values were enhanced during treatment, going from 0.002% for raw landfill leachate to 1.179% after the adsorption process.