Bismuth oxyhalides for NOx degradation under visible light: the role of the chloride precursor

ABSTRACT: Photocatalysis is a green technology for tackling water and air contamination. A valid alternative to the most exploited photocatalytic material, TiO2, is bismuth oxyhalides, which feature a wider bandgap energy range and use visible radiation to attain photoexcitation. Moreover, their layered structure favors the separation of photogenerated electron–hole pairs, with an enhancement in photocatalytic activity. Controlled doping of bismuth oxyhalides with metallic bismuth nanoparticles allows for further boosting of the performance of the material. In the present work, we synthesized Y%Bi-doped BiO(Cl0.875Br0.125) (Y = 0.85, 1, 2, 10) photocatalysts, using cetyltrimethylammonium bromide as the bromide source and varying the chloride source to assess the impact that both length and branching of the hydrocarbon chain might have on the framing and layering of the material. A change in the amount of the reducing agent NaBH4 allowed tuning of the percentage of metallic bismuth. After a thorough characterization (XRPD, SEM, TEM, UV-DRS, XPS), the photocatalytic activity of the catalysts was tested in the degradation of NOx under visible light, reaching a remarkable 53% conversion after 3 h of illumination for the material prepared using cetylpyridinium chloride

Sonocatalytic Biodiesel Transesterification to Produce a Lubricant

The growth of the machinery and automotive industry drives interest toward the production of biolubricants due to their better lubricating properties and their low carbon footprint compared to petroleum-based lubricants. However, their traditional synthesis is long and energy-intensive. We intensified the production of biolubricants from canola oil methyl esters using ultrasound. NaOH catalyzed the transesterification of two polyalcohols (propylene and trimethylene glycols). We varied the ultrasound power, temperature, type of alcohol, and alcohol/biodiesel molar ratio. Trimethylene glycol produced 90 ± 1.9% of biolubricant at 80 °C and 62 W with a molar ratio of 0.25. Calcium oxide supported on silica (CaO/SiO2) also catalyzed the reaction under optimal conditions. The yield of the CaO/SiO2-catalyzed reaction was two times lower than that obtained with NaOH. We surveyed the loading of CaO over SiO2, the catalyst loading in the reactor, and its leaching and reusability. A mass percentage of 50% CaO to SiO2 yielded 46 ± 3.2% lubricants at 3% by weight of the reactants’ total mass. After three reaction cycles, the ultrasound did not alter the particle size (e.g., mean diameters of fresh and used catalysts were 31 and 32 μm, respectively), but it leached the active sites, which reduced the activity of the catalyst for successive uses

Influence of frequency and amplitude on the mucus viscoelasticity of the novel mechano-acoustic Frequencer (TM)

Background: Cystic fibrosis affects 1/3200 Caucasians. This genetic disease disturbs the ion and water home-ostasis across epithelia, thus rendering mucus more viscous and harder to expel. Conventional treatments rely on the clapping method coupled with postural drainage. Despite the effectiveness of these procedures, they are invasive and enervating. Methods: Here we study a new mechano-acoustic treatment device to help patients expectorate excess mucus, the Frequencer (TM). We test both normal and pathological synthetic mucin solutions (1 % and 4 % by weight) in vitro. We varied the frequency applied (from 20 Hz to 60 Hz) as well as the amplitude (from 50 % to 100 % intensity). Moreover, we assessed the effect of NaCl on mucus rehydration. Results: A frequency of 40 Hz coupled with a 0.5 gL(-1) NaCl solution provokes partial mucus rehydration, regardless of the amplitude selected, as the work of adhesion measurements evidenced. Conclusions: Mechanical solicitation is fundamental to help patients affected by cystic fibrosis expectorate mucus. With an operating frequency of 20 Hz to 65 Hz, the Frequencer (TM) provides a gentler therapy than traditional methods (conventional chest physiotherapy). The Frequencer (TM) proved to be effective in the homogenization of synthetic mucin solutions in vitro in 20 min and elicited improved effectiveness in a mucin-rich environment

Characterization of the acoustic cavitation in ionic liquids in a horn-type ultrasound reactor.

Most ultrasound-based processes root in empirical approaches. Because nearly all advances have been conducted in aqueous systems, there exists a paucity of information on sonoprocessing in other solvents, particularly ionic liquids (ILs). In this work, we modelled an ultrasonic horn-type sonoreactor and investigated the effects of ultrasound power, sonotrode immersion depth, and solvents thermodynamic properties on acoustic cavitation in nine imidazolium-based and three pyrrolidinium-based ILs. The model accounts for bubbles, acoustic impedance mismatch at interfaces, and treats the ILs as incompressible, Newtonian, and saturated with argon. Following a statistical analysis of the simulation results, we determined that viscosity and ultrasound input power are the most significant variables affecting the intensity of the acoustic pressure field (P), the volume of cavitation zones (V), and the magnitude of the maximum acoustic streaming surface velocity (u). V and u increase with the increase of ultrasound input power and the decrease in viscosity, whereas the magnitude of negative P decreases as ultrasound power and viscosity increase. Probe immersion depth positively correlates with V, but its impact on P and u is insignificant. 1-alkyl-3-methylimidazolium-based ILs yielded the largest V and the fastest acoustic jets - 0.77 cm3 and 24.4 m s-1 for 1-ethyl-3-methylimidazolium chloride at 60 W. 1-methyl-3-(3-sulfopropyl)-imidazolium-based ILs generated the smallest V and lowest u - 0.17 cm3 and 1.7 m s-1 for 1-methyl-3-(3-sulfopropyl)-imidazolium p-toluene sulfonate at 20 W. Sonochemiluminescence experiments validated the model

Bismuth Oxyhalides for NOx Degradation under Visible Light: The Role of the Chloride Precursor

Photocatalysis is a green technology for tackling water and air contamination. A valid alternative to the most exploited photocatalytic material, TiO2, is bismuth oxyhalides, which feature a wider bandgap energy range and use visible radiation to attain photoexcitation. Moreover, their layered structure favors the separation of photogenerated electron–hole pairs, with an enhancement in photocatalytic activity. Controlled doping of bismuth oxyhalides with metallic bismuth nanoparticles allows for further boosting of the performance of the material. In the present work, we synthesized Y%Bi-doped BiO(Cl0.875Br0.125) (Y = 0.85, 1, 2, 10) photocatalysts, using cetyltrimethylammonium bromide as the bromide source and varying the chloride source to assess the impact that both length and branching of the hydrocarbon chain might have on the framing and layering of the material. A change in the amount of the reducing agent NaBH4 allowed tuning of the percentage of metallic bismuth. After a thorough characterization (XRPD, SEM, TEM, UV-DRS, XPS), the photocatalytic activity of the catalysts was tested in the degradation of NOx under visible light, reaching a remarkable 53% conversion after 3 h of illumination for the material prepared using cetylpyridinium chloride

Characterization of the acoustic cavitation in ionic liquids in a horn-type ultrasound reactor

Most ultrasound-based processes root in empirical approaches. Because nearly all advances have been conducted in aqueous systems, there exists a paucity of information on sonoprocessing in other solvents, particularly ionic liquids (ILs). In this work, we modelled an ultrasonic horn-type sonoreactor and investigated the effects of ultrasound power, sonotrode immersion depth, and solvent’s thermodynamic properties on acoustic cavitation in nine imidazolium-based and three pyrrolidinium-based ILs. The model accounts for bubbles, acoustic impedance mismatch at interfaces, and treats the ILs as incompressible, Newtonian, and saturated with argon. Following a statistical analysis of the simulation results, we determined that viscosity and ultrasound input power are the most significant variables affecting the intensity of the acoustic pressure field (P), the volume of cavitation zones (V), and the magnitude of the maximum acoustic streaming surface velocity (u). V and u increase with the increase of ultrasound input power and the decrease in viscosity, whereas the magnitude of negative P decreases as ultrasound power and viscosity increase. Probe immersion depth positively correlates with V, but its impact on P and u is insignificant. 1-alkyl-3-methylimidazolium-based ILs yielded the largest V and the fastest acoustic jets – 0.77 cm3 and 24.4 m s−1 for 1-ethyl-3-methylimidazolium chloride at 60 W. 1-methyl-3-(3-sulfopropyl)-imidazolium-based ILs generated the smallest V and lowest u – 0.17 cm3 and 1.7 m s−1 for 1-methyl-3-(3-sulfopropyl)-imidazolium p-toluene sulfonate at 20 W. Sonochemiluminescence experiments validated the model