Urban biowaste-derived sensitizing materials for caffeine photodegradation

Abstract

Caffeine-photosensitized degradation has been studied in the presence of bio-based materials derived from urban biowaste after aerobic aging. A peculiar fraction (namely bio-based substances (BBSs)), soluble in all the pH range, has been used as photosensitizing agent. Several caffeine photodegradation tests have been performed, and positive results have been obtained in the presence of BBSs and HO, without and with additional Fe(II) (photo-Fenton-like process). Moreover, hybrid magnetite-BBS nanoparticles have been synthesized and characterized, in order to improve the sensitizer recovery and reuse after the caffeine degradation. In the presence of such nanoparticles and HO and Fe(II), the complete caffeine degradation has been attained in very short time. Both homogeneous and heterogeneous processes were run at pH = 5, milder condition compared to the classic photo-Fenton process.

New Insights on the Photodegradation of Caffeine in the Presence of Bio-Based Substances-Magnetic Iron Oxide Hybrid Nanomaterials

“…The X-ray diffraction ( Figure 1 C) patterns for all HMNPs confirmed the crystalline reflections at 2θ = 30.1° (220), 35.4° (311), 43.0° (400), 53.9° (422), 57.2° (511), and 62.6° (440), consistent with the signals of the reference magnetite/maghemite M0 (card numbers 00-019-0629 and 00-039-1346, ICCD Database) [ 13 , 35 ]. The two phases (namely, magnetite and maghemite) cannot be distinguished by means of XRD, since both phases have the same identical XRD pattern.…”

“…430 °C due to the pyrolysis of BBS-C humic-like fraction, before forming a carbonaceous residue (BBS-C residue at 800 °C is ca. 40 wt.%) [ 35 ]. Once the pyrolysis temperature became higher than 700 °C, a weak weight variation was also registered for both the reference M0 and the HMNPs due to the iron oxide reduction to wustite (FeO) and elemental iron (Fe), in accordance with our previous studies [ 26 , 31 ].…”

“…The iron oxide magnetic nanoparticles were produced following a modified procedure based on a consolidated co-precipitation process reported in our previous studies [ 16 , 26 , 35 , 36 , 39 ]. In detail, 6.16 g FeCl 3 ·6H 2 O (purity = 98%, CAS 10025-77-1, Sigma-Aldrich, Saint Louis, MO, USA) and 4.2 g FeSO 4 ·7H 2 O (purity > 99.0%, CAS 7782-63-0, Sigma-Aldrich) were dissolved into 100 mL of deionized water.…”

“…Nevertheless, these oxides undergo oxidation in natural atmosphere, yielding non-magnetic hematite, and the addition of organic coatings during the magnetite synthesis could also act as stabilizing barrier against iron (II) oxidation [ 13 , 33 ]. The addition of BBS was demonstrated to stabilize magnetite/maghemite nanoparticles [ 34 ], and in the presence of this kind of materials, encouraging preliminary results have been obtained in the photodegradation of caffeine [ 35 , 36 ]. Indeed, the hybrid BBS-coated magnetic nanoparticles (HMNPs) enhanced the caffeine photodegradation in the presence of added hydrogen peroxide.…”

Isolation, Characterization, and Environmental Application of Bio-Based Materials as Auxiliaries in Photocatalytic Processes

“…The presence of both hydrophilic and hydrophobic functionalities forming the chemical structure of such BBS confers to these substances amphiphilic properties, as testified by the literature on analogous substrates [36][37][38]. As reported in our previous study [39], these BBS can be used in several industrial applications (as emulsifiers, foaming agents, in detergent formulations or as textiles auxiliaries, for the production of nanostructured materials, in animal husbandry, as fertilizers, or for the production of biofuels and bioplastics). Among the potential applications of such BBS, the most striking one is the "waste for cleaning waste" [40].…”