Innovative Synthetic Approaches for Sulphate-Promoted Catalysts for Biomass Valorisation

In the present research, we report on an innovative and quick procedure for the synthesis of metal oxides: a sol-gel procedure which is followed by two steps that are assisted by microwaves (MW) heating. First, MW heating promotes gel drying and successively permits the calcination of the xerogel in a few minutes, using a susceptor that rapidly reaches high temperatures. The procedure was employed for the synthesis of zirconium dioxide (ZrO2), and MW-assisted calcination enables the collection of tetragonal ZrO2, as confirmed by different experimental techniques (PXRD, HR-TEM and Raman spectroscopy). Using this MW-assisted sol-gel procedure, a promoted sulphated zirconia (SZ) has been obtained. Both the nature and strength of SZ surface acidity have been investigated with FTIR spectroscopy using CO and 2,6-dimethylpyridine (2,6-DMP) as probe molecules. The obtained materials were tested as catalysts in acid hydrolysis of glucose to give 5-(hydroxymethyl)furfural (5-HMF). One of the obtained catalysts exhibited a better selectivity towards 5-HMF with respect to SZ material prepared by a classical precipitation route, suggesting that this procedure could be employed to obtain a well-known catalyst with a less energy-consuming procedure. Catalytic results also suggest that good selectivity to 5-HMF can be achieved in aqueous media in the presence of weak Lewis and Brønsted sites

Biostimulants derived from organic urban wastes and biomasses: An innovative approach

We used humic and fulvic acids extracted from digestate to formulate nanohybrids with potential applications in agronomy. In order to obtain a synergic co-release of plant-beneficial agents, we functionalized with humic substances two inorganic matrixes: hydroxyapatite (Ca10(PO4)6(OH)2, HP) and silica (SiO2) nanoparticles (NPs). The former is a potential controlled-release fertilizer of P, and the latter has a beneficial effect on soil and plants. SiO2 NPs are obtained from rice husks by a reproducible and fast procedure, but their ability to absorb humic substances is very limited. HP NPs coated with fulvic acid are instead a very promising candidate, based on desorption and dilution studies. The different dissolutions observed for HP NPs coated with fulvic and humic acids could be related to the different interaction mechanisms, as suggested by the FT-IR study

Fast and efficient piezo-photocatalytic mineralization of ibuprofen by BiOBr nanosheets under solar light irradiation

ABSTRACT: In the present work, the piezoelectric-like behavior of BiOBr nanosheets was utilized to suppress the recombination of photoexcited charges. The piezo-photocatalytic properties of an easily synthesized photocatalyst were tested for the degradation of ibuprofen, a nonsteroidal anti-inflammatory drug. Under ultrasound and solar light irradiation, the reaction rate for ibuprofen mineralization was found to be higher in the BiOBr nanosheets compared with those from the individual photocatalysis and piezocatalysis approaches, respectively. A percentage of synergy higher than 60% was calculated, resulting in the achievement of complete mineralization in less than 30 min. Based on the results, a possible piezo-photocatalytic mechanism, based on the separation of photoinduced charges and the formation of highly active radicals, has been proposed. Furthermore, various scavengers were used to identify the active species by trapping holes and radicals generated during the piezo-photocatalytic degradation process. The main transformation products formed during both photo- and piezo-photodegradation processes were identified by ultraperformance liquid chromatography–mass spectrometry (UPLC/MS), and the ibuprofen degradation pathway was proposed. The very promising results offer an advantageous approach to drug mineralization without the need for costly materials or expensive processes