RESUMO
The limited access to fresh water and the increased presence of emergent pollutants (EPs) in wastewater has increased the interest in developing strategies for wastewater remediation, including photocatalysis. Graphitic carbon nitride (g-C3N4) is a 2D non-metal material with outstanding properties, such as a 2.7 eV bandgap and physicochemical stability, making it a promising photocatalyst. This work reports the process of obtaining high-surface-area (SA) g-C3N4 using the thermal-exfoliation process and the posterior effect of Ag-nanoparticle loading over the exfoliated g-C3N4 surface. The photocatalytic activity of samples was evaluated through methylene blue (MB) degradation under visible-light radiation and correlated to its physical properties obtained by XRD, TEM, BET, and UV-Vis analyses. Moreover, 74% MB degradation was achieved by exfoliated g-C3N4 compared to its bulk counterpart (55%) in 180 min. Moreover, better photocatalytic performances (94% MB remotion) were registered at low Ag loading, with 5 wt.% as the optimal value. Such an improvement is attributed to the synergetic effect produced by a higher SA and the role of Ag nanoparticles in preventing charge-recombination processes. Based on the results, this work provides a simple and efficient methodology to obtain Ag/g-C3N4 photocatalysts with enhanced photocatalytic performance that is adequate for water remediation under sunlight conditions.
RESUMO
Corn nixtamalization generates a waste byproduct that requires diverse environmental preservation measures depending on the country. Such measures could include catalytic and advanced oxidation processes. This study aims to exploit the hemicellulose within the nejayote (32.5%) to create added value chemicals such as furfural using photocatalytic hydrolysis. In the present work, titania (TiO2) nanoparticles (NPs) were greenly synthesized using Ricinus Communis (RC), Moringa Oleifera (MO) or Bougainvillea Spectabilis (BS) plant extracts. Obtained nanoparticles were characterized using XRD, SEM, EDS, BET, XPS and UV-vis techniques. Furthermore, the photocatalytic performance of the obtained samples was evaluated in the furfural production from nejayote. Furfural yield reached 44% in 30 min using the BS synthesized material, which is 1.6 × the yield obtained by the material synthesized with MO extract (26.4% at 45 min) and 6 × the yield obtained by the material obtained with RC (7.2% at 90 min). Such results have not been reported before in the literature and could be the groundwork for novel waste treatments in the tortilla-making industry.
RESUMO
The highly effective Au/Fe2O3-@Au/Fe2O3nanoreactors for the 4-nitrophenol (4-NP) reduction are successfully obtained by one-pot synthesis using the spray pyrolysis (SP) technique. The Au/Fe2O3-@Au/Fe2O3nanoreactors manifest superior catalytic activity in the reduction of 4-NP in the presence of sodium borohydride (NaBH4) compared to gold-iron oxide nanoreactors prepared via a colloidal approach. The negative effect of the reaction product accumulation, the 4-aminophenol (4-AP), on the catalytic reduction of 4-NP over Au/Fe2O3-@Au/Fe2O3is examined by a direct pre-injection of 4-AP to the reaction media. To the best of our knowledge, it is the first experimental evidence of gold active sites blocking by 4-AP. All obtained samples are characterized by the yolk-shell spherical hollow structure mainly consisted of two embedded hollow nanospheres. The reduction of iron oxide precursor concentration diminishes the diameter of final iron oxide nanospheres. According to STEM-EDS analysis and STEM, Au nano species are uniformly dispersed on both iron oxide nanospheres. The SP technique presently used to synthesize Au/Fe2O3-@Au/Fe2O3nanoreactors manifests high potential for the one-pot fabrication of a large variety of nanoreactors with various active materials applied as heterogeneous catalysts in numerous catalytic processes.