Sonochemistry: Application Notes

La sonochimica è l'effetto della cavitazione ultrasonica sui sistemi chimici. A causa delle condizioni estreme che si verificano nella cavitazione “hot spot”, power ultrasound is an very effective method to improve reaction outcome (higher yield, better quality), conversion and duration of a chemical reaction. Some chemical changes can be achieved under sonication only, such as the nano-sized tin-coating of titanium or aluminum.

Find below a selection of particles and liquids with related recommendations, how to treat the material in order to mill, disperse, deagglomerate or modify the particles using an ultrasonic homogenizer.

Find below some sonication protocols for successful sonochemical reactions!

In alphabetical order:

α-Epoxyketones – Ring-opening Reaction

Ultrasonic application:
The catalytic ring opening of α-epoxyketones was carried out using a combination of ultrasound and photochemical methods. 1-benzyl-2,4,6-triphenylpyridinium tetrafluoroborate (NBTPT) were used as photocatalyst. By the combination of sonication (sonochemistry) and photochemistry of these compounds in the presence of NBTPT, the opening of epoxide ring was achieved. It was demonstrated that the use of ultrasound increased the rate of the photo-induced reaction significantly. Ultrasound can seriously affect photocatalytic ring opening of α-epoxyketones predominantly because of the efficient mass transfer of the reactants and the excited state of NBTPT. Also the electron transfer between the active species in this homogeneous system using sonication occurs
faster than the system without sonication. The higher yields and shorter reaction times are advantages of this method.

Ultrasound-assisted photocatalytic ring opening of α-epoxyketones (study and graphic: ©Memarian et al 2007)

Sonication protocol:
α-Epoxyketones 1a-f and 1-benzyl-2,4,6-triphenylpyridinium tetrafluoroborate 2 were prepared according to the reported procedures. Methanol was purchased from Merck and distilled before use. The ultrasonic device used was an UP400S ultrasonic probe-device from Hielscher Ultrasonics GmbH. A S3 ultrasonic immersion horn (also known as probe or sonotrode) emitting 24 kHz ultrasound at intensity levels tunable up to maximum sonic power density of 460Wcm^-2 è stata utilizzata. La sonicazione è stata effettuata al 100% (ampiezza massima 210μm). Il sonotrodo S3 (profondità massima di immersione di 90 mm) è stato immerso direttamente nella miscela di reazione. Le irradiazioni UV sono state effettuate utilizzando una lampada a mercurio ad alta pressione da 400W di Narva con raffreddamento dei campioni in vetro Duran. Il ¹H NMR spectra of the mixture of photoproducts were measured in CDCl₃ solutions containing tetramethylsilane (TMS) as internal standard on a Bruker drx-500 (500 MHz). Preparative layer chromatography (PLC) was carried out on 20 × 20cm² plates coated with 1mm layer of Merck silica gel PF₂₅₄ prepared by applying the silica as a slurry and drying in air. All products are known and their spectral data have been reported earlier.
Device Recommendation:
UP400S with ultrasonic horn S3
Reference/ Research Paper:
Memarian, Hamid R.; Saffar-Teluri, A. (2007): Photosonochemical catalytic ring opening of α-epoxyketones. Beilstein Journal of Organic Chemistry 3/2, 2007.

Aluminum/Nickel catalyst: Nano-structuring of Al/Ni Alloy

Ultrasonic application:
Al/Ni particles can be sonochemically modified by the nano-structuring of initial Al/Ni alloy. Therbey, an effective catalyst for the hydrogenation of acetophenone is produced.
Ultrasonic preparation of Al/Ni catalyst:
5g of the commercial Al/Ni alloy were dispersed in purified water (50mL) and sonicated up to 50 min. with the ultrasound probe-type sonicator UIP1000hd (1kW, 20kHz) equipped with the ultrasonic horn BS2d22 (head area of 3.8 cm²) and the booster B2-1.8. The maximum intensity was calculated to be 140 Wcm⁻² at mechanical amplitude of 106μm. To avoid the temperature increase during sonication the experiment was performed in a thermostatic cell. After sonication, the sample was dried under vacuum with a heat gun.
Device Recommendation:
UIP1000hd with sonotrode BS2d22 and booster horn B2–1.2
Reference/ Research Paper:
Dulle, Jana; Nemeth, Silke; Skorb, Ekaterina V.; Irrgang, Torsten; Senker, Jürgen; Kempe, Rhett; Fery, Andreas; Andreeva, Daria V. (2012): Sonochemical Activation of Al/Ni Hydrogenation Catalyst. Advanced Functional Materials 2012. DOI: 10.1002/adfm.201200437

Biodiesel Transesterification using MgO Catalyst

Ultrasonic application:
La reazione di transesterificazione è stata studiata in condizioni di miscelazione ultrasonica costante con il sonicatore UP200S per diversi parametri come la quantità di catalizzatore, il rapporto molare tra metanolo e olio, la temperatura di reazione e la durata della reazione. Gli esperimenti in batch sono stati eseguiti in un reattore di vetro duro (300 ml, 7 cm di diametro interno) con coperchio a due colli smerigliato. Un collo è stato collegato al sonotrodo S7 in titanio (diametro della punta 7 mm) del processore a ultrasuoni UP200S (200W, 24kHz). L'ampiezza degli ultrasuoni è stata impostata al 50% con 1 ciclo al secondo. La miscela di reazione è stata sonicata per tutto il tempo di reazione. L'altro collo della camera del reattore è stato dotato di un condensatore in acciaio inossidabile, raffreddato ad acqua, per far rifluire il metanolo evaporato. L'intero apparato è stato posto in un bagno d'olio a temperatura costante, controllato da un termoregolatore proporzionale integrale derivato. La temperatura può essere aumentata fino a 65°C con una precisione di ±1°C. Come materiale per la transesterificazione del biodiesel sono stati utilizzati olio di scarto e metanolo puro al 99,9%. Come catalizzatore è stato utilizzato MgO (nastro di magnesio) di dimensioni nanometriche depositato a fumo.
Un ottimo risultato di conversione è stato ottenuto con 1,5 wt% di catalizzatore; rapporto molare metanolo-olio 5:1 a 55°C, con una conversione del 98,7% dopo 45 min.
Device Recommendation:
UP200S with ultrasonic sonotrode S7
Reference/ Research Paper:
Sivakumar, P.; Sankaranarayanan, S.; Renganathan, S.; Sivakumar, P.(): Studies on Sono-Chemical Biodiesel Production Using Smoke Deposited Nano MgO Catalyst. Bulletin of Chemical Reaction Engineering & Catalysis 8/ 2, 2013. 89 – 96.

Sintesi di nanocompositi di cadmio(II)-tioacetammide

Ultrasonic application:
I nanocompositi cadmio(II)-tioacetammide sono stati sintetizzati in presenza e in assenza di alcool polivinilico per via sonochemica. Per la sintesi stereochimica (sono-sintesi), 0,532 g di cadmio (II) acetato diidrato (Cd(CH3COO)2.2H2O), 0,148 g di tioacetamide (TAA, CH3CSNH2) e 0,664 g di ioduro di potassio (KI) sono stati disciolti in 20mL di acqua deionizzata bidistillata. Questa soluzione è stata sonicata con un ultrasuonatore a sonda ad alta potenza UP400S (24 kHz, 400W) a temperatura ambiente per 1 ora. Durante la sonicazione della miscela di reazione, la temperatura è aumentata fino a 70-80degC, come misurato da una termocoppia ferro-costantinica. Dopo un'ora si è formato un precipitato giallo brillante. È stato isolato per centrifugazione (4.000 rpm, 15 min), lavato con acqua bidistillata e poi con etanolo assoluto per rimuovere le impurità residue e infine essiccato all'aria (resa: 0,915 g, 68%). Dec. p.200°C. Per preparare il nanocomposito polimerico, 1,992 g di alcool polivinilico sono stati sciolti in 20 mL di acqua deionizzata bidistillata e poi aggiunti alla soluzione precedente. La miscela è stata irradiata a ultrasuoni con la sonda a ultrasuoni UP400S per 1 h, quando si è formato un prodotto di colore arancione brillante.
The SEM results demonstrated that in presence of PVA the sizes of the particles decreased from about 38 nm to 25 nm. Then we synthesized hexagonal CdS nanoparticles with spherical morphology from thermal decomposition of the polymeric nanocomposite, cadmium(II)-thioacetamide/PVA as precursor. The size of the CdS nanoparticles was measured both by XRD and SEM and the results were in very good agreement with each other.
Ranjbar et al. (2013) also found that the polymeric Cd(II) nanocomposite is a suitable precursor for the preparation of cadmium sulfide nanoparticles with interesting morphologies. All results revealed that ultrasonic synthesis can be employed successfully as a simple, efficient, low cost, environmentally friendly and very promising method for the synthesis of nanoscale materials without a need for special conditions, such as high temperature, long reaction times, and high pressure.
Device Recommendation:
UP400S
Reference/ Research Paper:
Ranjbar, M.; Mostafa Yousefi, M.; Nozari, R.; Sheshmani, S. (2013): Synthesis and Characterization of Cadmium-Thioacetamide Nanocomposites. Int. J. Nanosci. Nanotechnol. 9/4, 2013. 203-212.

CaCO3 – Ultrasonically Coated with Stearic Acid

Ultrasonic application:
Ultrasonic coating of nano-precipitated CaCO₃ (NPCC) with stearic acid to improve its dispersion in polymer and to reduce agglomeration. 2g of uncoated nano-precipitated CaCO₃ (NPCC) è stato sonicato con il sonicatore UP400S in 30 ml di etanolo. Il 9% in peso di acido stearico è stato sciolto in etanolo. L'etanolo con l'acido stearico è stato poi mescolato alla sospensione sonicata.
Device Recommendation:
UP400S with 22mm diameter sonotrode (H22D), and flow cell with cooling jacket
Reference/ Research Paper:
Kow, K. W.; Abdullah, E. C.; Aziz, A. R. (2009): Effects of ultrasound in coating nano-precipitated CaCO3 with stearic acid. Asia‐Pacific Journal of Chemical Engineering 4/5, 2009. 807-813.

Cerium Nitrate Doped Silane

Ultrasonic application:
Come substrati metallici sono stati utilizzati pannelli di acciaio al carbonio laminati a freddo (6,5 cm, 6,5 cm, 0,3 cm; puliti chimicamente e lucidati meccanicamente). Prima dell'applicazione del rivestimento, i pannelli sono stati puliti a ultrasuoni con acetone e poi puliti con una soluzione alcalina (soluzione di NaOH 0,3mol L1) a 60°C per 10 minuti. Per l'utilizzo come primer, prima del pretrattamento del substrato, una formulazione tipica comprendente 50 parti di γ-glicidrossipropiltrimetossisilano (γ-GPS) è stata diluita con circa 950 parti di metanolo, a pH 4,5 (regolato con acido acetico) e lasciata agire per l'idrolisi del silano. La procedura di preparazione del silano drogato con pigmenti di nitrato di cerio è stata la stessa, tranne per il fatto che 1, 2, 3 wt% di nitrato di cerio è stato aggiunto alla soluzione di metanolo prima dell'aggiunta di (γ-GPS), quindi questa soluzione è stata mescolata con un agitatore a elica a 1600 rpm per 30 minuti a temperatura ambiente. Successivamente, le dispersioni contenenti nitrato di cerio sono state sonicate per 30 minuti a 40°C con un bagno di raffreddamento esterno. Il processo di ultrasonicazione è stato eseguito con l'ultrasuonatore UIP1000hd (1000W, 20 kHz) con una potenza di ultrasuoni in ingresso di circa 1 W/mL. Il pretrattamento del substrato è stato eseguito risciacquando ogni pannello per 100 secondi con la soluzione di silano appropriata. Dopo il trattamento, i pannelli sono stati lasciati asciugare a temperatura ambiente per 24 ore, quindi i pannelli pretrattati sono stati rivestiti con una resina epossidica bicomponente a base di ammina. (Epon 828, Shell Co.) per ottenere uno spessore del film umido di 90μm. I pannelli rivestiti di epossidica sono stati lasciati polimerizzare per 1 ora a 115°C; dopo la polimerizzazione dei rivestimenti epossidici, lo spessore del film secco era di circa 60μm.
Device Recommendation:
UIP1000hd
Reference/ Research Paper:
Zaferani, S.H.; Peikari, M.; Zaarei, D.; Danaei, I. (2013): Electrochemical effects of silane pretreatments containing cerium nitrate on cathodic disbonding properties of epoxy coated steel. Journal of Adhesion Science and Technology 27/22, 2013. 2411–2420.

Copper-Aluminium Frameworks: Synthesis of porous Cu-Al frameworks

Ultrasonic application:
Porous copper–aluminium stabilized by metal oxide is a promising new alternative catalyst for propane dehydrogenation which is free of noble or hazardous metals. The structure of the oxidized porous Cu–Al alloy (metal sponge) is similar to Raney-type metals. High-power ultrasound is a green chemistry tool for the synthesis of porous copper–aluminum frameworks stabilized by metal oxide. They are inexpensive (production cost of approx. 3 EUR/liter) and the method can be easily scaled-up. These new porous materials (or “metal sponges”) have an alloy bulk and an oxidized surface, and can catalyze propane dehydrogenation at low temperatures.
Procedure for the ultrasonic catalyst preparation:
Five grams of the Al–Cu alloy powder were dispersed in ultrapure water (50mL) and sonicated for 60 min with the Hielscher probe-type sonicator UIP1000hd (20kHz, max. output power 1000W). The ultrasound probe-type device was equipped with a sonotrode BS2d22 (tip area 3.8cm²) and the booster horn B2–1.2. The maximum intensity was calculated to be 57 W/cm² at a mechanical amplitude of 81μm. During the treatment the sample was cooled in an ice bath. After the treatment, the sample was dried at 120°C for 24 h.
Device Recommendation:
UIP1000hd with sonotrode BS2d22 and booster horn B2–1.2
Reference/ Research Paper:
Schäferhans, Jana; Gómez-Quero, Santiago; Andreeva, Daria V.; Rothenberg, Gadi (2011): Novel and Effective Copper–Aluminum Propane Dehydrogenation Catalysts. Chem. Eur. J. 2011, 17, 12254-12256.

Copper Phathlocyanine Degradation

Ultrasonic application:
Decolorization and destruction of metallophthalocyanines
Copper phathlocyanine is sonicated with water and organic solvents at ambient temperature and atmospheric pressure in the presence of catalytic amount of oxidant using the 500W ultrasonicator UIP500hd with fold-trough chamber at a power level of 37–59 W/cm²: 5 mL di campione (100 mg/L), 50 D/D di acqua con coloformio e piridina al 60% dell'ampiezza degli ultrasuoni. Temperatura di reazione: 20°C.
Device Recommendation:
UIP500hd

Gold: Morphological modification of Gold Nanoparticles

Ultrasonic application:
Gold nano particles were morphologically modified under intense ultrasonic irradiation. To fuse gold nanoparticles into a dumbbell-like structure a ultrasonic treatment of 20 min. in pure water and in the presence of surfactants was found sufficient. After 60 min. of sonication, the gold nanoparticles acquire a worm-like or ring-like structure in water. Fused nanoparticles with spherical or oval shapes were ultrasonically formed in the presence of sodium dodecyl sulfate or dodecyl amine solutions.
Protocol of the ultrasonic treatment:
For the ultrasonic modification, the colloidal gold solution, consisting in preformed citrate-protected gold nanoparticles with an average diameter of 25nm (± 7nm), were sonicated in a closed reactor chamber (approx. 50mL volume). The colloidal gold solution (0.97 mmol·L^-1) was ultrasonically irradiated at high intensity (40 W/cm^-2) using a Hielscher UIP1000hdT ultrasonicator (20kHz, 1000W) equipped with a titanium alloy sonotrode BS2d18 (0.7 inch tip diameter), which was immersed about 2 cm below the surface of the sonicated solution. The colloidal gold was gassed with argon (O₂ < 2 ppmv, Air Liquid) 20 min. before and during sonication at a rate of 200 mL·min^-1 to eliminate the oxygen in the solution. A 35-mL portion of each surfactant solution without addition of trisodium citrate dihydrate was added by 15 mL of preformed colloidal gold, bubbled with an argon gas 20 min. before and during ultrasonic treatment.
Device Recommendation:
UIP1000hd with sonotrode BS2d18 and flow cell reactor
Reference/ Research Paper:
Radziuk, D.; Grigoriev,D.; Zhang, W.; Su, D.; Möhwald, H.; Shchukin, D. (2010): Ultrasound-Assisted Fusion of Preformed Gold Nanoparticles. Journal of Physical Chemistry C 114, 2010. 1835–1843.

Inorganic Fertilizer – Leaching of Cu, Cd, and Pb for Analysis

Ultrasonic application:
Extraction of Cu, Cd and Pb from inorganic fertilizers for analytical purpose:
Per l'estrazione a ultrasuoni di rame, piombo e cadmio, i campioni contenenti una miscela di fertilizzante e solvente sono stati sonicati con un dispositivo a ultrasuoni come il sonicatore VialTweeter per la sonicazione indiretta. I campioni di fertilizzante sono stati sonicati in presenza di 2mL di 50% (v/v) di HNO₃ in glass tubes for 3 minutes. The extracts of Cu, Cd and Pb can be determined by flame atomic absorption spectrometry (FAAS).
Device Recommendation:
VialTweeter
Reference/ Research Paper:
Lima, A. F.; Richter, E. M.; Muñoz, R. A. A. (2011): Alternative Analytical Method for Metal Determination in Inorganic Fertilizers Based on Ultrasound-Assisted Extraction. Journal of the Brazilian Chemical Society 22/ 8. 2011. 1519-1524.

Latex Synthesis

Ultrasonic application:
Preparation of P(St-BA) latex
Poly(styrene-r-butyl acrylate) P(St-BA) latex particles were synthesized by emulsion polymerization in the presence of surfactant DBSA. 1 g of DBSA was first dissolved in 100mL of water in a three-necked flask and the pH value of the solution was adjusted to 2.0. Mixed monomers of 2.80g St and 8.40g BA with the initiator AIBN (0.168g) were poured into the DBSA solution. The O/W emulsion was prepared via magnetic stirring for 1 h followed by sonication with the sonicator UIP1000hd equipped with ultrasonic horn (probe/ sonotrode) for another 30 min. in the ice bath. Finally, the polymerization was carried out at 90degC in an oil bath for 2h under a nitrogen atmosphere.
Device Recommendation:
UIP1000hd
Reference/ Research Paper:
Fabrication of flexible conductive films derived from poly(3,4-ethylenedioxythiophene)epoly(styrenesulfonic acid) (PEDOT:PSS) on the nonwoven fabrics substrate. Materials Chemistry and Physics 143, 2013. 143-148.
Click here to read more about the sono-synthesis of latex!

Lead Removal (Sono-Leaching)

Ultrasonic application:
Ultrasonic leaching of Lead from contaminated soil:
The ultrasound leaching experiments were performed with an ultrasonic homogenizer UP400S with a titanium sonic probe (diameter 14mm), which operates at a frequency of 20kHz. The ultrasonic probe (sonotrode) was calorimetrically calibrated with the ultrasonic intensity set to 51 ± 0.4 W cm^-2 for all the sono-leaching experiments. The sono-leaching experiments were thermostated using a flat bottom jacketed glass cell at 25 ± 1°C. Three systems were employed as soil leaching solutions (0.1L) under sonication: 6 mL of 0.3 mol L^-2 di soluzione di acido acetico (pH 3,24), soluzione di acido nitrico al 3% (v/v) (pH 0,17) e un tampone di acido acetico/acetato (pH 4,79) preparato mescolando 60mL 0di 0,3 mol L^-1 acetic acid with 19 mL 0.5 mol L^-1 NaOH. After the sono-leaching process, samples were filtered with filter paper to separate the leachate solution from soil followed by lead electrodeposition of the leachate solution and digestion of soil after the application of ultrasound.
Ultrasound has been proven to be a valuable tool in enhancing the leachate of lead from pollute soil. Ultrasound is also an effective method for the near total removal of leachable lead from soil resulting in a much less hazardous soil.
Device Recommendation:
UP400S with sonotrode H14
Reference/ Research Paper:
Sandoval-González, A.; Silva-Martínez, S.; Blass-Amador, G. (2007): Ultrasound Leaching and Electrochemical Treatment Combined for Lead Removal Soil. Journal of New Materials for Electrochemical Systems 10, 2007. 195-199.

PbS – Sintesi di nanoparticelle di solfuro di piombo

Ultrasonic application:
At room temperature, 0.151 g lead acetate (Pb(CH₃COO)2.3H₂O) and 0.03 g of TAA (CH₃CSNH₂) were added to 5mL of the ionic liquid, [EMIM] [EtSO₄], and 15mL of double distilled water in a 50mL beaker imposed to ultrasonic irradiation with the Hielscher sonicator UP200S for 7 min. The tip of the ultrasonic probe/ sonotrode S1 was immersed directly in the reaction solution. The formed dark brown color suspension was centrifuged to get the precipitate out and washed two times with double distilled water and ethanol respectively to remove the unreacted reagents. To investigate the effect of ultrasound on the properties of the products, one more comparative sample was prepared, keeping the reaction parameters constant except that the product is prepared at continuous stirring for 24 h without the aid of ultrasonic irradiation.
Ultrasonic-assisted synthesis in aqueous ionic liquid at room temperature was proposed for preparation of PbS nanoparticles. This room-temperature and environmentally benign green method is fast and template-free, which shortens synthesis time remarkably and avoids the complicated synthetic procedures. The as-prepared nanoclusters show an enormous blue shift of 3.86 eV that can be attributed to very small size of particles and quantum confinement effect.
Device Recommendation:
UP200S
Reference/ Research Paper:
Behboudnia, M.; Habibi-Yangjeh, A.; Jafari-Tarzanag, Y.; Khodayari, A. (2008): Facile and Room Temperature Preparation and Characterization of PbS Nanoparticles in Aqueous [EMIM][EtSO4] Ionic Liquid Using Ultrasonic Irradiation. Bulletin of Korean Chemical Society 29/ 1, 2008. 53-56.

Phenol Degradation

Ultrasonic application:
Rokhina et al. (2013) used the combination of peracetic acid (PAA) and heterogeneous catalyst (MnO₂) for the degradation of phenol in an aqueous solution under ultrasonic irradiation. Ultrasonication was carried out using a 400W probe-type ultrasonicator UP400S, which is capable to sonicate either continuously or in pulse mode (i.e. 4 sec. on and 2 sec. off) at a fixed frequency of 24 kHz. The calculated total power input, power density and power intensity dissipated to the system were 20 W, 9.5×10^-2 W/cm^-3, and 14.3 W/cm^-2rispettivamente. La potenza fissa è stata utilizzata per tutti gli esperimenti. Per controllare la temperatura all'interno del reattore è stato utilizzato un circolatore a immersione. Il tempo effettivo di sonicazione è stato di 4 ore, anche se il tempo reale di reazione è stato di 6 ore a causa del funzionamento in modalità pulsata. In un esperimento tipico, il reattore di vetro è stato riempito con 100 mL di soluzione di fenolo (1,05 mM) e dosi appropriate del catalizzatore MnO2 e della PAA (2%), comprese tra 0-2 g L^-1 and 0–150 ppm, respectively. All reactions were performed at circum neutral pH, atmospheric pressure and a room temperature (22 ± 1 °C).
By ultrasonication, the surface area of the catalyst was increased resulting in a 4-fold larger surface area with no change in the structural. The turnover frequencies (TOF) were increased from 7 x 10^-3 to 12.2 x 10^-3 min^-1rispetto al processo silenzioso. Inoltre, non è stata rilevata alcuna lisciviazione significativa del catalizzatore. L'ossidazione isotermica del fenolo a concentrazioni relativamente basse di reagenti ha dimostrato alti tassi di rimozione del fenolo (fino all'89%) a condizioni blande. In generale, gli ultrasuoni hanno accelerato il processo di ossidazione durante i primi 60 minuti (70% di rimozione del fenolo rispetto al 40% durante il trattamento silenzioso).
Device Recommendation:
UP400S
Reference/ Research Paper:
Rokhina, E. V.; Makarova, K.; Lahtinen, M.; Golovina, E. A.; Van As, H.; Virkutyte, J. (2013): Ultrasound-assisted MnO₂ catalyzed homolysis of peracetic acid for phenol degradation: The assessment of process chemistry and kinetics. Chemical Engineering Journal 221, 2013. 476–486.

Phenol: Oxidation of Phenol using RuI₃ as catalyst

Ultrasonic application:
Heterogeneous aqueous oxidation of phenol over RuI₃ with hydrogen peroxide (H₂O₂): The catalytic oxidation of phenol (100 ppm) over RuI₃ as a catalyst was studied in a 100 mL glass reactor equipped with a magnetic stirrer and a temperature controller. The reaction mixture was stirred at a speed of 800 rpm for 1–6 hours to provide a complete mixing for uniform distribution and full suspension of catalysts particles. No mechanical stirring of the solution was performed during sonication due to the disturbance caused by cavitation bubble oscillation and collapse, providing itself an extremely efficient mixing. Ultrasound irradiation of the solution was carried out with an ultrasonic transducer UP400S equipped with ultrasonic (so-called probe–type sonicator), capable of operating either continuously or in a pulse mode at a fixed frequency of 24 kHz and a maximum power output of 400W.
For the experiment, untreated RuI₃ as catalyst (0.5–2 gL^-1) è stato introdotto in sospensione nel mezzo di reazione con successiva aggiunta di H2O2 (30%, concentrazione nell'intervallo 200-1200 ppm).
Rokhina et al. found in their study that ultrasonic irradiation played a prominent role in the modification of catalyst’s textural properties, producing the microporous structure with higher surface area as a result of fragmentation of the catalyst particles. Moreover, it had a promotional effect, preventing agglomeration of the catalyst particles and improving the accessibility of phenol and hydrogen peroxide to the active sites of the catalyst.
The two–fold increase in ultrasound–assisted process efficiency in comparison to the silent oxidation process was attributed to the improved catalytic behaviour of the catalyst and generation of oxidizing species such as •OH, •HO2 and •I₂ via hydrogen bonds cleavage and recombination of radicals.
Device Recommendation:
UP400S
Reference/ Research Paper:
Rokhina, E. V.; Lahtinen, M.; Nolte, M. C. M.; Virkutyte, J. (2009): Ultrasound-Assisted Heterogeneous Ruthenium Catalyzed Wet Peroxide Oxidation of Phenol. Applied Catalysis B: Environmental 87, 2009. 162– 170.

PLA Coated Ag/ZnO Particles

Ultrasonic application:
Rivestimento in PLA di particelle di Ag/ZnO: Le micro e submicro-particelle di Ag/ZnO rivestite di PLA sono state preparate con la tecnica dell'emulsione olio-acqua per evaporazione con solvente. Il metodo è stato eseguito nel modo seguente. In primo luogo, 400 mg di polimero sono stati sciolti in 4 ml di cloroformio. La concentrazione risultante di polimero in cloroformio era di 100 mg/ml. In secondo luogo, la soluzione di polimero è stata emulsionata in una soluzione acquosa di vari sistemi tensioattivi (agente emulsionante, PVA 8-88) sotto agitazione continua con un omogeneizzatore alla velocità di 24.000 giri/min. La miscela è stata agitata per 5 minuti e durante questo periodo l'emulsione formatasi è stata raffreddata con ghiaccio. Il rapporto tra la soluzione acquosa di tensioattivo e la soluzione cloroformica di PLA è stato identico in tutti gli esperimenti (4:1). Successivamente, l'emulsione ottenuta è stata ultrasonata da un dispositivo a sonda ultrasonica UP400S (400W, 24kHz) per 5 min. a ciclo 0,5 e ampiezza 35%. Infine, l'emulsione preparata è stata trasferita in una beuta, agitata e il solvente organico è stato evaporato dall'emulsione a pressione ridotta, portando alla formazione di una sospensione di particelle. Dopo la rimozione del solvente, la sospensione è stata centrifugata tre volte per rimuovere l'emulsionante.
Device Recommendation:
UP400S
Reference/ Research Paper:
Kucharczyk, P.; Sedlarik, V.; Stloukal, P.; Bazant, P.; Koutny, M.; Gregorova, A.; Kreuh, D.; Kuritka, I. (2011): Poly (L-Lactic Acid) Coated Microwave Synthesized Hybrid Antibacterial Particles. Nanocon 2011.

Polyaniline Composite

Ultrasonic application:
Preparation of water-based self-doped nano polyaniline (SPAni) composite (Sc-WB)
To prepare the water-based SPAni composite, 0.3 gr SPAni, synthesized using in-situ polymerization in ScCO2 medium, was diluted with water and sonicated for 2 minutes by an 1000W ultrasonic homogenizer UIP1000hd. Then, the suspension product was homogenized by adding 125 gr water-based hardener matrix for 15 min. and the final sonication was carried out at ambient temperature for 5 min.
Device Recommendation:
UIP1000hd
Reference/ Research Paper:
Bagherzadeh, M.R.; Mousavinejad, T.; Akbarinezhad, E.; Ghanbarzadeh, A. (2013): Protective Performance of Water-Based Epoxy Coating Containing ScCO2 Synthesized Self-Doped Nanopolyaniline. 2013.

Polycyclic Aromatic Hydrocarbons: Sonochemical Degradation of Naphthalene, Acenaphthylene and Phenanthrene

Ultrasonic application:
For the sonochemical degradation of polycyclic aromatic hydrocarbons (PAHs) naphthalene, acenaphthylene and phenanthrene in water, sample mixtures were sonicated at 20◦C and 50 µg/l of each target PAH (150 µg/l of total initial concentration). Ultrasonication was applied by an UP400S horn-type ultrasonicator (400W, 24kHz), which is capable of operating either in continuous or in pulse mode. The sonicator UP400S was equipped with a titanium probe H7 with 7 mm diameter tip. The reactions were carried out in a 200 mL cylindrical glass reaction vessel with the titanium horn mounted on top of the reaction vessel and sealed using O-rings and a Teflon valve. The reaction vessel was placed in a water bath to control the process temperature. To avoid any photochemical reactions, the vessel was covered with aluminium foil.
The analysis results showed that the conversion of PAHs increases with increasing sonication duration.
Per il naftalene, la conversione assistita dagli ultrasuoni (potenza degli ultrasuoni impostata a 150W) è aumentata dal 77,6% ottenuto dopo 30 minuti di sonicazione all'84,4% dopo 60 minuti di sonicazione.
Per l'acenaftilene, la conversione assistita dagli ultrasuoni (potenza degli ultrasuoni impostata a 150W) è aumentata dal 77,6% ottenuto dopo 30 min. di sonicazione con potenza degli ultrasuoni di 150W all'84,4% dopo 60 min. di sonicazione con ultrasuoni di 150W, passando dall'80,7% ottenuto dopo 30 min. di sonicazione con potenza degli ultrasuoni di 150W al 96,6% dopo 60 min. di sonicazione.
Per il fenantrene, la conversione assistita dagli ultrasuoni (potenza degli ultrasuoni impostata a 150W) è aumentata dal 73,8% ottenuto dopo 30 minuti di sonicazione all'83,0% dopo 60 minuti di sonicazione.
To enhance degradation efficiency, hydrogen peroxide can be utilized more efficient when ferrous ion is added. The addition of ferrous ion has been shown to have synergetic effects simulating a Fenton-like reaction.
Device Recommendation:
UP400S with H7
Reference/ Research Paper:
Psillakis, E.; Goula, G.; Kalogerakis, N.; Mantzavinos, D. (2004): Degradation of polycyclic aromatic hydrocarbons in aqueous solutions by ultrasonic irradiation. Journal of Hazardous Materials B108, 2004. 95–102.

Oxide Layer Removal from Substrates

Ultrasonic application:
To prepare the substrate before growing CuO nanowires on Cu substrates, the intrinsic oxide layer on the Cu surface was removed by ultrasonicating the sample in 0.7 M hydrochloric acid for 2 min. with an Hielscher UP200S. The sample was ultrasonically cleaned in acetone for 5 min. to remove organic contaminants, thoroughly rinsed with deionized (DI) water, and dried in compressed air.
Device Recommendation:
UP200S o UP200St
Reference/ Research Paper:
Mashock, M.; Yu, K.; Cui, S.; Mao, S.; Lu, G.; Chen, J. (2012): Modulating Gas Sensing Properties of CuO Nanowires through Creation of Discrete Nanosized p−n Junctions on Their Surfaces. ACS Applied Materials & Interfaces 4, 2012. 4192−4199.

Voltammetry Experiments

Ultrasonic application:
For ultrasound-enhanced voltammetry experiments, a Hielscher 200 watts ultrasonicator UP200S equipped with glass horn (13-mm diameter tip) was employed. The ultrasound was applied with an intensity of 8 W/cm^–2.
Due to the slow rate of diffusion of nanoparticles in aqueous solutions and the high number of redox centres per nanoparticle, the direct solution-phase voltammetry of nanoparticles is dominated by adsorption effects. In order to detect nanoparticles without accumulation due to adsorption, an experimental approach has to be chosen with (i) a sufficiently high concentration of nanoparticles, (ii) small electrodes to improve the signal-to-back-ground ratio, or (iii) very fast mass transport.
Therefore, McKenzie et al. (2012) employed power ultrasound to drastically improve the rate of mass transport of nanoparticles toward the electrode surface. In their experimental setup, the electrode is directly exposed to high intensity ultrasound with 5 mm electrode-to-horn distance and 8 W/cm^–2 sonication intensity resulting in agitation and cavitational cleaning. A test redox system, the one-electron reduction of Ru(NH3)₆³⁺ in aqueous 0.1 M KCl, was employed to calibrate the rate of mass transport achieved under these conditions.
Device Recommendation:
UP200S o UP200St
Reference/ Research Paper:
McKenzie, K. J.; Marken, F. (2001): Direct electrochemistry of nanoparticulate Fe2O3 in aqueous solution and adsorbed onto tin-doped indium oxide. Pure Applied Chemistry, 73/ 12, 2001. 1885–1894.

Sonicators for Sonochemical Reactions from Lab to Industrial Scale

Hielscher offers the full range of ultrasonicators from the handheld lab homogenizer up to full industrial sonicators for high volume streams. All results achieved in small scale during testing, R&D and optimization of an ultrasonic process, can be >linearly scaled up to full commercial production. Hielscher sonicators are reliable, robust and built for 24/7 operation.
Ask us, how to evaluate, optimize and scale your process! We are glad to assist you during all stages – from first tests and process optimization to installation in your industrial production line!