Application of Ultrasound in Inorganic Synthesis

Enomoto, Naoya; Okitsu, Kenji

doi:10.1016/b978-0-12-801530-8.00008-6

Cited by 4 publications

(3 citation statements)

References 39 publications

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“…In this case, the CuO US sample has a smaller crystal size compared to the CuO CH sample. This is due to the formation of a large number of nuclei at the beginning of the crystallization stage and can be attributed to the cavitation effect [32]. The material with combined treatment (Cu MW-US) has a crystal size closer to that obtained for the CuO US.…”

Section: Copper Oxidementioning

confidence: 79%

Synthesis of CuO for Microwave-Assisted Pyrolysis of Biomass

et al. 2019

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In this study, CuO was synthesized as a microwave absorber in the pyrolysis of a biomass model (sugarcane bagasse). CuO was synthesized for 5 min of irradiation using the following techniques: microwave (MW), ultrasound (US), combined mode (MW-US), and conduction heating (CH) as a reference material. The use of these treatments promotes changes in the morphology, as MW and US generate leaves and monolithic faceted morphologies, respectively. Changes were also generated in some textural characteristics such as crystal size, surface area, and volume-pore size. They were produced as a consequence of changes in the conditions during the crystallization stage produced by the different irradiation types. The microwave-assisted pyrolysis was performed aiming for the maximum liquid fraction (bio-oil) in the products. The reaction time, the size of the biomass, and the CuO synthesis method were also analyzed. The following particle size (ps) intervals were studied: ps < 0.5 mm, 0.5 mm < ps < 1.7 mm, 1.7 mm < ps < 3.5 mm. The best conditions at 1160 Watts in the microwave were: 4 min of reaction, particle size lower than 0.5 mm, and CuO synthesized by US. The use of CuO in the pyrolysis almost triples the amount of the obtained liquid fraction, when compared with the pyrolysis without the use of a microwave absorbent. The CuO was reduced to Cu2O and Cu after the pyrolysis. In this work, a reduction in the reaction times from hours to minutes was achieved during the synthesis of CuO and the pyrolysis biomass. The liquid fraction (bio-oil) can be raw material to obtain value-added chemical products or biofuels.

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Section: Copper Oxidementioning

confidence: 79%

Synthesis of CuO for Microwave-Assisted Pyrolysis of Biomass

et al. 2019

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“…On the other hand, the sonochemical reduction of metal ions to produce metal nanoparticles has been experimentally reported [ 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 ]. In most of the experiments, an organic material such as alcohol (

, where

or alkyl group), ascorbic acid, formic acid, etc., was added to the aqueous solution to produce a reducing agent by the chemical reaction with

radicals generated from cavitation bubbles as follows for alcohol [ 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 65 , 66 , 68 , 71 , 72 , 73 ].

where

is a reducing agent (radical) and reduces metal ions as follows [ 57 , 61 , 68 ].…”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, the sonochemical reduction of metal ions to produce metal nanoparticles has been experimentally reported [54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73]. In most of the experiments, an organic material such as alcohol (RCH 2 OH, where R = H or alkyl group), ascorbic acid, formic acid, etc., was added to the aqueous solution to produce a reducing agent by the chemical reaction with OH radicals generated from cavitation bubbles as follows for alcohol [54][55][56][57][58][59][60][61]65,66,68,[71][72][73].…”

Section: Introductionmentioning

confidence: 99%

The Reducing Agents in Sonochemical Reactions without Any Additives

Yasui

2023

Molecules

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It has been experimentally reported that not only oxidation reactions but also reduction reactions occur in aqueous solutions under ultrasound without any additives. According to the numerical simulations of chemical reactions inside an air or argon bubble in water without any additives under ultrasound, reducing agents produced from the bubbles are H, H2, HO2 (which becomes superoxide anion (O2−) in liquid water), NO, and HNO2 (which becomes NO2− in liquid water). In addition, H2O2 sometimes works as a reducing agent. As the reduction potentials of H and H2 (in strongly alkaline solutions for H2) are higher than those of RCHOH radicals, which are usually used to reduce metal ions, H and H2 generated from cavitation bubbles are expected to reduce metal ions to produce metal nanoparticles (in strongly alkaline solutions for H2 to work). It is possible that the superoxide anion (O2−) also plays some role in the sonochemical reduction of some solutes. In strongly alkaline solutions, hydrated electrons (e−aq) formed from H atoms in liquid water may play an important role in the sonochemical reduction of solutes because the reduction potential is extremely high. The influence of ultrasonic frequency on the amount of H atoms produced from a cavitation bubble is also discussed.

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