Sonochemistry: Science and Engineering

A control system for ultrasound devices utilized for inactivating E. coli in wastewater

Sonochemical processes applied to wastewater treatment have an influence on the behavior of ultrasonic systems. This is especially due to the load characteristic of the sonochemical process itself and the temperature increase caused by internal damping within the converter. Hence, a controlling device is needed to guarantee the operation in resonance and to keep the vibration amplitude constant. This paper presents a digital control system for the operation of weak to strong damped ultrasonic devices and its application for inactivating Escherichia coli in wastewater. In an experimental investigation, the electric data during a sonochemical process to inactivate E. coli in wastewater is taken into account to analyze the efficacy of the treatment process and the reaction of the vibration system to the process. Frequency response measurements depict that the resonance frequency changes with the sonicated medium and the vibration amplitude decreases with driving current. In addition to a common continuous operation of the system, different pulsed modes are investigated. The experiments prove the common dependencies between inactivation and power level or treatment time. Additionally, it is pointed out that the control of the sonochemical device is of utmost importance to guarantee an efficient treatment of water, because fast process changes, especially in pulsed operation modes, need to be controlled to a steady state as fast as possible. Although a water treatment efficiency increase using pulsed modes was not proved, it is shown, that the performance of the control unit is capable of using different driving modes in water treatment.

One-step synthesis and assembly of spindle-shaped akaganéite nanoparticles via sonochemistry

We demonstrate a green method based on sonochemistry for large-scale production of akaganéite nanoparticles and assemblies in low cost.

Controlled "golf ball shape" structuring of Mg surface under acoustic cavitation

This manuscript describes the original structuring of Mg materials under ultrasound irradiation in mild conditions. Golf ball like extended structures can be prepared in dilute oxalic solutions at 20°C under high frequency ultrasound (200kHz). An original approach carried out through iterative 3D reconstruction of sonicated surfaces is used to describe surface evolutions and characterize the formed microstructures. A combination of SEM, ICP-AES, contact-angle measurements, and 3D image analyses allows to characterize the roughness and mass loss evolutions, and investigate the mechanism of formation for such architectures. A screening of the sonication experiments clearly points out an ultrasound frequency dependency for the effects generated at the surface. 200kHz sonication in 0.01M oxalic acid provides an unprecedented manufacturing of Mg samples which result from a controlled and localized dissolution of the material and characterized by a strong wetting surface with a roughness of 170nm. The additional formation of newly formed secondary phases appearing with surface dissolution progress is also deciphered. More generally, the ultrasonic procedure used to prepare these engineered surfaces opens new alternatives for the nano- and micro-structuring of metallic materials which may exhibit advanced physical and chemical properties of potential interest for a large community.

Process intensification

Process intensification (PI) is a rapidly growing field of research and industrial development that has already created many innovations in chemical process industry. PI is directed toward substantially smaller, cleaner, more energy-efficient technology. Furthermore, PI aims at safer and sustainable technological developments. Its tools are reduction of the number of devices (integration of several functionalities in one apparatus), improving heat and mass transfer by advanced mixing technologies and shorter diffusion pathways, miniaturization, novel energy techniques, new separation approaches, integrated optimization and control strategies. This review discusses many of the recent developments in PI. Starting from fundamental definitions, microfluidic technology, mixing, modern distillation techniques, membrane separation, continuous chromatography, and application of gravitational, electric, and magnetic fields will be described.

Rational one-step synthesis of porous PtPdRu nanodendrites for ethanol oxidation reaction with a superior tolerance for CO-poisoning

Precise fabrication of porous ternary Pt-based nanodendrites is very important for electrochemical energy conversion owing to high surface area and great molecular accessibility of these nanodendrites. Herein, PtPdRu porous nanodendrites (PNDs) were prepared via a facile one-step ultrasonic irradiation approach at room temperature. Intriguingly, the ultrasonic irradiation drove the formation of PtPdRu PNDs with spatially interconnected porous structures, whereas magnetic stirring produced PtPdRu nanoflowers (NFs) with less porosity. The formation mechanism was ascribed to the acoustic cavitation effect and fast-reduction kinetics under sonication. The as-made PtPdRu PNDs displayed a superior catalytic performance towards ethanol oxidation reaction with a high tolerance for CO-poisoning as compared to PtPdRu NFs, PtPd NDs, and commercial Pt/C catalyst.

Sonochemical synthesis of hydrogenated amorphous silicon nanoparticles from liquid trisilane at ambient temperature and pressure

Silicon nanoparticles (Si-NPs) are increasing in relevance in diverse fields of scientific and nanotechnological inquiry, where currently some of the most important areas of research involve energy storage and biomedical applications. The present article is concerned with a curious and scalable method for the preparation of discrete, unoxidized, hydrogenated, and amorphous Si-NPs of tunable size in the range of 1.5-50nm. Using ultrasound generated with a conventional ultrasonic horn, the "fusion" of Si-NPs is demonstrated at ambient temperature and pressure by sonicating solutions containing readily available, semiconductor-grade purity trisilane (Si₃H₈). The only requirement for the synthesis is that it be carried out in an inert atmosphere such as that of a N₂-filled glove box. Various spectroscopic techniques and electron microscopy images are used to show that the size of the Si-NPs can be controlled by varying the amplitude of the ultrasonic waves or the concentration of trisilane in the solution. Moreover, sustained ultrasonic irradiation is found to yield highly porous Si-NP agglomerates that may find use in applications requiring non-crystalline nanoscopic high specific surface area morphologies.

Sonochemical green reduction to prepare Ag nanoparticles decorated graphene sheets for catalytic performance and antibacterial application

The emerging popularity and wide acceptance of green chemistry and environmentally benign/ecofriendly approaches have comprehensively considered for catalyst synthesis methods. Natural resource derived carbogenic quantum dots has been used in assistance with ultrasonic shock wave to graphene oxide (GO) aqueous dispersion in order to prepare reduced graphene oxide decorated with silver nanoparticles following the 'top-down' method. The total reduction process is done without using any toxic external reducing agents and any surfactants or stabilizers, thus it can be accepted as green method. Sonochemical destratification of the GO layers provides green attributes due to scalable, non-hazardous and relatively fast reduction to enhance surface area of the GO. Arresting the silver nanoparticles onto basal planes of graphene oxide can act as an efficient solid state support catalyst for fast reduction of toxic nitro aryls. Besides this work also reports bactericidal feature exhibited by the catalyst. Thus a dual functioning nanomaterial has been successfully developed which can be a suitable alternative for reductive forthcoming specialty/multifunctional membrane and other high-end medicinal or industrial applications.

Non-Noble Metal Oxide Catalysts for Methane Catalytic Combustion: Sonochemical Synthesis and Characterisation

The aim of this study was to obtain nanocrystalline mixed metal-oxide–ZrO₂ catalysts via a sonochemically-induced preparation method. The effect of a stabiliser’s addition on the catalyst parameters was investigated by several characterisation methods including X-ray Diffraction (XRD), nitrogen adsorption, X-ray fluorescence (XRF), scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrometer (EDS), transmission electron microscopy (TEM) and µRaman. The sonochemical preparation method allowed us to manufacture the catalysts with uniformly dispersed metal-oxide nanoparticles at the support surface. The catalytic activity was tested in a methane combustion reaction. The activity of the catalysts prepared by the sonochemical method was higher than that of the reference catalysts prepared by the incipient wetness method without ultrasonic irradiation. The cobalt and chromium mixed zirconia catalysts revealed their high activities, which are comparable with those presented in the literature.

Ultrasound assisted enzymatic hydrolysis of starch catalyzed by glucoamylase: Investigation on starch properties and degradation kinetics

The present work investigates the synergistic impact of glucoamylase and ultrasound on starch hydrolysis. The extent of starch hydrolysis at different reaction parameters (ultrasonic intensity, temperature, reaction time) was analyzed. The hydrolysis extent increased with the reaction time and reached a maximum value under ultrasonic intensity of 7.20W/mL at 10min. Ultrasound did not alter the optimum enzymatic temperature but speeded up the thermal inactivation of glucoamylase. The evaluation of enzymatic kinetics and starch degradation kinetics indicated a promotion of the reaction rate and enzyme-substrate affinity. According to the thermodynamic results, sonoenzymolysis reactions require less energy than enzymolysis reactions. The measurement of molecular weight, solubility, thermal properties, and structures of the substrates revealed that sonoenzymolysis reaction generated greater impacts on starch properties. The molecular weight and radii of gyration decreased by 80.19% and 90.05% respectively while the starch solubility improved by 136.50%.

Sonochemical synthesis and structural determination of novel the nano-card house Cu(II) metal-organic coordination system

A sonochemical method by using various time and concentrations of initial reagents and power of irradiation, was used to synthesize nano-card house of a new copper(II) metal-organic coordination system, {[Cu₂(p-2yeinh)₂Cl₂]·(H₂O)}_n (1), where p-2yeinh=pyridin-2-yl ethylidene-isonicotinohydrazide. The compound was characterized by scanning electron microscopy (SEM), elemental analysis, IR spectroscopy, X-ray powder diffraction (XPRD), and single crystal X-ray analysis. The X-ray structure revealed that the Cu(II) atom is coordinated by one oxygen and three nitrogen atoms from two p-2yeinh ligands and one chloride anion with a CuN₃OCl donor set with square pyramid geometry. This arrangement produces a large quadric nuclear square ring composed of four square pyramid Cu(II) moieties linked together by two p-2yeinh units (M4L4). The adjacent frameworks connected by strong hydrogen bonding interactions of methanol molecules that interact together and with the rings and π-π interactions of adjacent aromatic rings of p-2yeinh and other weak interactions. Consequently, the labile interactions also allow the discrete structure to form a 3D metal-organic coordination network. CuO nanoparticles were obtained by thermolysis of 1 at 180°C with oleic acid as a surfactant. The average diameter of the nanoparticles was estimated by XPRD to be 38nm. The morphology and size of the prepared CuO nanoparticles were further studied using SEM.

Ultrasonic-assisted Kabachnik-Fields reaction for rapid fabrication of AIE-active fluorescent organic nanoparticles

Aggregation-induced emission (AIE)-active fluorescent organic nanoparticles (FNPs) have been extensively explored for fluorescence "turn-on" bio-imaging applications with the unique advantages over conventional FNPs. Transformation of AIE-active molecules into FNPs can greatly expand their biomedical application potential. Here we reported a novel "one-pot" strategy for fabricating AIE-active FNPs through an ultrasonic-assisted, catalysts-free and solvent-free Kabachnik-Fields (KF) reaction for the first time. The KF reaction can be completed within 10min to generate AIE-active PTH-CHO-PEI-DEP FNPs through mixing polyethylenimine and aldehyde group containing AIE dyes and diethyl phosphate. These PTH-CHO-PEI-DEP FNPs were confirmed by proton nuclear magnetic resonance (¹H NMR) spectroscopy, transmission electron microscopy (TEM) and fluorescence spectroscopy etc. The cell uptake behavior as well as cell viability of PTH-CHO-PEI-DEP FNPs was examined to evaluate their potential for biomedical application. We demonstrated that the amphiphilic α-aminophosphonate polymers could self-assemble into PTH-CHO-PEI-DEP FNPs in aqueous solution and showed excellent water dispersibility. TEM image shows the size of PTH-CHO-PEI-DEP FNPs is 100-200nm. More importantly, the PTH-CHO-PEI-DEP FNPs emit strong green fluorescence and desirable biocompatibility, making them very suitable for biomedical applications. Finally, thus smart FNPs design together with their excellent performance will open a new avenue in the development of FNPs for following biological processes such as carcinogenesis.

Enhanced boron adsorption onto synthesized MgO nanosheets by ultrasonic method

MgO nanosheets with high adsorption performance were fabricated by an ultrasonic method. It was revealed that, nest-like MgO was formed from the magnesium salt solution precipitation and further calcination. Then the nest-like MgO was exfoliated by ultrasonic waves to obtain MgO nanosheets with approximately a lateral of 200-600nm and a thickness of 10nm. Adjusting the ultrasonic time and power, the specific surface areas of MgO nanosheets could be tuned in a range of 79-168m²/g. The synthesized MgO nanosheets were used as adsorbents to remove boron from aqueous solution, and the maximum boron adsorption capacity of these MgO nanosheets reached 87mgg^-1. The high uptake capability of the MgO nanosheets makes it potentially adsorbent for the removal of boron from wastewaters.

Sonochemical heating profile for solvents and ionic liquid doped solvents, and their application in the N-alkylation of pyrazoles

The heating profile for 25 solvents was determined in ultrasonic probe equipment at amplitudes of 20%, 25%, and 30%. Each solvent was heated in accordance with its boiling point. The effect of vapor pressure, surface tension, and viscosity of the solvents in dissipated ultrasonic power (Up) was evaluated. Multiple regression analysis of these solvent properties and dissipated Up reveals that solvent viscosity is the property that most strongly affected dissipated Up. Experimentation involving acetonitrile doped with [BMIM][BF4] indicated faster heating than MeCN. Aprotic polar solvents such as DMSO, DMF, and MeCN were tested in the N-alkylation of pyrazoles under ultrasonic conditions. After 5min at 90°C, the reactants had been totally converted into product in these solvents. Solvents, with low dissipated Up (e.g., toluene) were tested. Conversions were lower compared to those of aprotic polar solvents. When the reactions were done in hexane, no conversion to product was observed. To check the effect of doping in solvents with low Up, [BMIM][BF4], DMSO, and DMF were selected. The conversions for toluene doped with [BMIM][BF4], DMSO, and DMF were 100%, 59%, and 25%, respectively. These conversions were greater than when done in just toluene (46%). Thus, [BMIM][BF4] was the best polar doping solvent, followed by DMSO. DMF was not considered to be a satisfactory doping solvent. No conversion was observed for reactions in the absence of base performed in DMSO, DMF, and MeCN doped with [BMIM][BF4].

Depolymerization of microcrystalline cellulose by the combination of ultrasound and Fenton reagent

In this study, the combined use of Fenton reagent and ultrasound to the pretreatment of microcrystalline cellulose (MCC) for subsequent enzyme hydrolysis was investigated. The morphological analysis showed that the aspect ratio of MCC was greatly reduced after pretreatment. The X-ray diffraction (XRD) and degree of polymerization (DP) analyses showed that Fenton reagent was more efficient in decreasing the crystallinity of MCC while ultrasound was more efficient in decreasing the DP of MCC. The combination of Fenton reaction and ultrasound, which produced the lowest crystallinity (84.8 ± 0.2%) and DP (124.7 ± 0.6) of MCC and the highest yield of reducing sugar (22.9 ± 0.3 g/100 g), provides a promising pretreatment process for MCC depolymerization.