High adsorption capacity of two Zn-based metal–organic frameworks by ultrasound assisted synthesis

Micro- and nano-rods and plates of two 3D, porous Zn(II)-based metal–organic frameworks [Zn(oba)(4-bpdh)_0.5]_n·(DMF)_1.5 (TMU-5) and [Zn(oba)(4-bpmb)_0.5]_n (DMF)_1.5 (TMU-6) were prepared by sonochemical process and characterized by scanning electron microscopy, X-ray powder diffraction and IR spectroscopy. These MOFs were synthesized using a non-linear dicarboxylate (H₂oba = 4,4-oxybisbenzoic acid) and two linear N-donor (4-bpdh = 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene and 4-bpmb = N¹,N⁴-bis((pyridin-4-yl)methylene)benzene-1,4-diamine) ligands by ultrasonic irradiation. Sonication time and concentration of initial reagents influencing size and morphology of nano-structured MOFs, were also studied. Calcination of TMU-5 and TMU-6 at 550 °C under air atmosphere yields ZnO nanoparticles. TMU-5 and TMU-6 exhibited maximum percent adsorption of 96.2% and 92.8% of 100 ppm rhodamine B dye, respectively, which obeys first order reaction kinetics.     

Catalytic dechlorination of 2,4-dichlorophenol by Ni/Fe nanoparticles prepared in the presence of ultrasonic irradiation

In this study, nickle/iron (Ni/Fe) nanoparticles were synthesized by liquid phase reductive method in the presence of 20 kHz ultrasonic irradiation to improve nanoparticles’ disparity and avoid agglomeration. The characterized results showed that this method has obviously modified most of the particles in term of sizes and specific surface areas. Meanwhile, the improved nanoscale Ni/Fe particles were employed for the reductive dechlorination of 2,4-dichlorophenol (2,4-DCP) as a function of some influential factors (Ni content, Ni/Fe nanoparticles dosage, reaction temperature and initial pH values) and degradation path. Experimental results showed that 2,4-DCP was first adsorbed by Ni/Fe nanoparticles, then quickly reduced to o-chlorophenol (o-CP), p-chlorophenol (p-CP), and finally to phenol (P). The application of ultrasonic irradiation for Ni/Fe nanoparticles synthesis was found to significantly enhance the removal efficiency of 2,4-DCP. Consequently, the phenol production rates increased from 68% (in the absence of ultrasonic irradiation) to 87% (in the presence of ultrasonic irradiation) within 180 min. Nearly 96% of 2,4-DCP was removed after 300 min reaction with these optimized conditions: Ni content over Fe⁰ 3 wt%, initial 2,4-DCP concentration 20 mg L⁻¹, Ni/Fe dosage 3 g L⁻¹, initial pH value 3.0, and reaction temperature 25 °C. The degradation of 2,4-DCP followed pseudo-first-order kinetics reaction and the apparent pseudo-first-order kinetics constant was 0.0737 min⁻¹. This study suggested that the presence of ultrasonic irradiation in the synthesis of nanoscale Ni/Fe particles could be a promising technique to enhance nanoparticle’s disparity and avoid agglomeration.     

Sonochemical water splitting in the presence of powdered metal oxides

Kinetics of hydrogen formation was explored as a new chemical dosimeter allowing probing the sonochemical activity of argon-saturated water in the presence of micro- and nano-sized metal oxide particles exhibiting catalytic properties (ThO₂, ZrO₂, and TiO₂). It was shown that the conventional sonochemical dosimeter based on H₂O₂ formation is hardly applicable in such systems due to catalytic degradation of H₂O₂ at oxide surface. The study of H₂ generation revealed that at low-frequency ultrasound (20 kHz) the sonochemical water splitting is greatly improved for all studied metal oxides. The highest efficiency is observed for relatively large micrometric particles of ThO₂ which is assigned to ultrasonically-driven particle fragmentation accompanied by mechanochemical water molecule splitting. The nanosized metal oxides do not exhibit particle size reduction under ultrasonic treatment but nevertheless yield higher quantities of H₂. The enhancement of sonochemical water splitting in this case is most probably resulting from better bubble nucleation in heterogeneous systems. At high-frequency ultrasound (362 kHz), the effect of metal oxide particles results in a combination of nucleation and ultrasound attenuation. In contrast to 20 kHz, micrometric particles slowdown the sonolysis of water at 362 kHz due to stronger attenuation of ultrasonic waves while smaller particles show a relatively weak and various directional effects.     

Superiority of sonochemical processing method for the synthesis of barium titanate nanocrystals in contrast to the mechanochemical approach

The results indicated that the ultrasonic sonochemistry which brings into play the acoustic cavitation phenomenon is more powerful and feasible in synthesizing the mixed oxides in contrast to the conventional solid-state approaches. The obtained results demonstrated that the sonochemical approach is able to obtain highly pure powder product at a much lower processing temperature of about 323 K (50 °C) in contrast to 1173 K (900 °C) which is essential for the synthesis by the mechanochemical approach. Sonochemical synthesis benefits from homogenous ordering the reactant ions (which have been dissolved in the solution mixture) into perovskite structure using ultrasonication. This indicates that the acoustic cavitation phenomenon is much more powerful and cost-effective than high energy ball milling in synthesizing nanopowders of the mixed oxide materials. Moreover, the sonochemical processing method is able to prepare the final powder products in a much shorter time by a one-step synthesis approach without the need for the successive calcination in contrast to the solid-state approach.     

Ultrasonic assisted synthesis of Bikitaite zeolite: A potential material for hydrogen storage application

Li containing Bikitaite zeolite has been synthesized by an ultrasound-assisted method and used as a potential material for hydrogen storage application. The Sonication energy was varied from 150 W to 250 W and irradiation time from 3 h to 6 h. The Bikitaite nanoparticles were characterized by X-ray diffraction (XRD), infrared (IR) spectral analysis, and field-emission scanning electron microscopy (FESEM) thermo-gravimetrical analysis and differential thermal analysis (TGA, DTA). XRD and IR results showed that phase pure, nano crystalline Bikitaite zeolites were started forming after 3 h irradiation and 72 h of aging with a sonication energy of 150 W and nano crystalline Bikitaite zeolite with prominent peaks were obtained after 6 h irradiation of 250 W sonic energy. The Brunauer–Emmett–Teller (BET) surface area of the powder by N₂ adsorption–desorption measurements was found to be 209 m²/g. The TEM micrograph and elemental analysis showed that desired atomic ratio of the zeolite was obtained after 6 h irradiation. For comparison, sonochemical method, followed by the hydrothermal method, with same initial sol composition was studied. The effect of ultrasonic energy and irradiation time showed that with increasing sonication energy, and sonication time phase formation was almost completed. The FESEM images revealed that 50 nm zeolite crystals were formed at room temperature. However, agglomerated particles having woollen ball like structure was obtained by sonochemical method followed by hydrothermal treatment at 100 °C for 24 h. The hydrogen adsorption capacity of Bikitaite zeolite with different Li content, has been investigated. Experimental results indicated that the hydrogen adsorption capacities were dominantly related to their surface areas as well as total pore volume of the zeolite. The hydrogen adsorption capacity of 143.2 c.c/g was obtained at 77 K and ambient pressure of (0.11 MPa) for the Bikitaite zeolite with 100% Li, which was higher than the reported values for other zeolites. To the best of our knowledge, there is no report on the synthesis of a Bikitaite zeolite by sonochemical method for H₂ storage.     

Ultrasonic assisted synthesis,characterization and influence factors of monodispersed dumbbell-like YF3 nanostructures

In the present paper, we reported the successful synthesis of dumbbell-like YF₃ nanostructures with a high yield in a mixed system of water/N,N-dimethylformamide (DMF) under the assistance of ultrasound waves of 40 kHz with the ultrasonic power of 100% (200 W) at 65 °C for 2 h, employing Y₂O₃ (99.99%) and NH₄F as the starting reactants. The product was characterized by means of powder X-ray diffraction (XRD), energy dispersive spectrometry (EDS), transmission electron microscopy (TEM), selected area electron diffraction (SAED) pattern and field-emission scanning electron microscopy (SEM). Some factors influencing the morphology of YF₃ nanostructures, including the ultrasonic time and power, the amount of NH₄F, and the ratio of water/DMF, were systematically investigated. Research showed that the morphology of YF₃ could be tuned by the volume ratio of water/DMF. The roles of DMF and the ultrasonic wave in the formation of YF₃ nanostructures were discussed.     

Sonochemical fabrication of Fe3O4 nanoparticles on reduced graphene oxide for biosensors

This study synthesized Fe₃O₄ nanoparticles of 30–40 nm by a sonochemical method, and these particles were uniformly dispersed on the reduced graphene oxide sheets (Fe₃O₄/RGO). The superparamagnetic property of Fe₃O₄/RGO was evidenced from a saturated magnetization of 30 emu/g tested by a sample-vibrating magnetometer. Based on the testing results, we proposed a mechanism of ultrasonic waves to explain the formation and dispersion of Fe₃O₄ nanoparticles on RGO. A biosensor was fabricated by modifying a glassy carbon electrode with the combination of Fe₃O₄/RGO and hemoglobin. The biosensor showed an excellent electrocatalytic reduction toward H₂O₂ at a wide, linear range from 4 × 10^?6 to 1 × 10^?3 M (R² = 0.994) as examined by amperometry, and with a detection limit of 2 × 10^?6 M. The high performance of H₂O₂ detection is attributed to the synergistic effect of the combination of Fe₃O₄ nanoparticles and RGO, promoting the electron transfer between the peroxide and electrode surface.     

Sonochemical synthesis,structural, magnetic and grain size dependent electrical properties of NdVO4 nanoparticles

NdVO₄ nanoparticles are successfully synthesized by efficient sonochemical method using two different structural directing agents like CTAB and P123. The phase formation and functional group analysis are carried out using X-ray diffraction (XRD) and fourier transform infra red (FT-IR) spectra, respectively. Using Scherrer equation the calculated grain sizes are 27 nm, 24 nm and 20 nm corresponding to NdVO₄ synthesized by without surfactant, with CTAB and P123, respectively. The TEM images revealed that the shape of NdVO₄ particles is rice-like and rod shaped particles while using CTAB and P123 as surfactants. The growth mechanism of NdVO₄ nanoparticles is elucidated with the aid of TEM analysis. From electrical analysis, the conductivity of NdVO₄ nanoparticles synthesized without surfactant showed a higher conductivity of 5.5703 × 10⁻⁶ S cm⁻¹. The conductivity of the material depends on grain size and increased with increase in grain size due to the grain size effect. The magnetic measurements indicated the paramagnetic behavior of NdVO₄ nanoparticles.     

Ultrasonic degradation of acetaminophen in water: Effect of sonochemical parameters and water matrix

This paper deals about the sonochemical water treatment of acetaminophen (ACP, N-acetyl-p-aminophenol or paracetamol), one of the most popular pharmaceutical compounds found in natural and drinking waters. Effect of ultrasonic power (20–60 W), initial ACP concentration (33–1323 μmol L⁻¹) and pH (3–12) were evaluated. High ultrasonic powers and, low and natural acidic pH values favored the efficiency of the treatment. Effect of initial substrate concentration showed that the Langmuir-type kinetic model fit well the ACP sonochemical degradation. The influence of organic compounds in the water matrix, at concentrations 10-fold higher than ACP, was also evaluated. The results indicated that only organic compounds having a higher value of the Henry’s law constant than the substrate decrease the efficiency of the treatment. On the other hand, ACP degradation in mineral natural water showed to be strongly dependent of the initial substrate concentration. A positive matrix effect was observed at low ACP concentrations (1.65 μmol L⁻¹), which was attributed to the presence of bicarbonate ion in solution. However, at relative high ACP concentrations a detrimental effect of matrix components was noticed. Finally, the results indicated that ultrasonic action is able to transform ACP in aliphatic organic compounds that could be subsequently eliminated in a biological system.     

Multibubble sonoluminescence as a tool to study the mechanism of formic acid sonolysis

Sonoluminescence spectra collected from 0.1 to 3.0 M aqueous solutions of formic acid sparged with argon show the OH(A²Σ⁺−X²Π_i) and C₂(d³Π_g → a³Π_u) emission bands and a broad continuum typical for multibubble sonoluminescence. The overall intensity of sonoluminescence and the sonochemical yield of HCOOH degradation vary in opposite directions: the sonoluminescence is quenched while the sonochemical yield increases with HCOOH concentration. By contrast, the concentration of formic acid has a relatively small effect on the intensity of C₂ Swan band. It is concluded that C₂ emission originates from CO produced by HCOOH degradation rather than from direct sonochemical degradation of HCOOH. The intensity of C₂ band is much stronger at high ultrasonic frequency compared to 20 kHz ultrasound which is in line with higher yields of CO at high frequency. Another product of HCOOH sonolysis, carbon dioxide, strongly quenches sonoluminescence, most probably via collisional non-radiative mechanism.     

CuFe2O4 magnetic heterogeneous nanocatalyst: Low power sonochemical-coprecipitation preparation and applications in synthesis of 4H-chromene-3-carbonitrile scaffolds

The paper presents the synthesis and catalytic activity of CuFe₂O₄ nanoparticles. The CuFe₂O₄ nanoparticles have been prepared by sonochemical route under low power ultrasonic irradiation (UI) and using silent stirring at room temperature only (ST) along with co-precipitation method, without using any additive/capping agent. The synthesized magnetic nanoparticles were successfully used and compared for the synthesis of 4H-chromene-3-carbonitrile derivatives. The CuFe₂O₄ nanoparticles obtained by sonochemical route exhibit higher catalytic activity because of small size (0.5–5 nm), high surface area (214.55 m²/g), high thermal stability up to 700 °C, recyclability and reusability due to its magnetic characteristics than CuFe₂O₄ nanoparticles obtained by room temperature silent stirring. The synthesized CuFe₂O₄ nanoparticles were characterized by FT-IR, SEM–EDX, HR-TEM, XRD, TGA/DTA/DTG, BET, VSM techniques. The present method is of great interest due to its salient features such as environmentally compatible, efficient, short reaction time, chemoselectivity, high yield, cheap, moisture insensitive, green and recyclable catalyst which make it sustainable protocol.     

High yield synthesis of Ni-BTC metal–organic framework with ultrasonic irradiation: Role of polar aprotic DMF solvent

Nickel based porous solid was synthesized with 20 kHz ultrasonic irradiation. The reaction of Ni(II) nitrate hexahydrate with 1,3,5-benzene tricarboxylic acid in N,N-Dimethylformamide (DMF) as the sole solvent under ultrasonic radiation produced porous Ni-BTC MOF. Choice of correct solvent for the ultrasonic treatment was proven important. The effect of varying ultrasonic powers (40%, 60% and 80% of 750 W) along with different temperature conditions (50 °C, 60 °C, 70 °C and 80 °C) influenced the respective yield. A very high yield of 88% Ni-BTC MOF was obtained from 80% ultrasonic power at 60 °C. BET surface areas of the MOF crystals measured by N₂ gas adsorption isotherms were in the range of 960–1000 m²/g.     

Anatase TiO2 nanocrystals prepared by mechanochemical synthesis and their photochemical activity studied by EPR spectroscopy

Anatase TiO₂ has been prepared by mechanochemical synthesis using TiOSO₄·xH₂O and Na₂CO₃ as starting reactants. The reaction was performed in high-energy ball mill using steel and corundum jars, respectively. The final products were obtained by annealing the milled powder in the temperature range of 300–700 °C and subsequently by washing out the water-soluble byproduct Na₂SO₄·xH₂O. When steel jars were used, the annealing in the range of 300–600 °C led to anatase. For products milled in corundum, the stability of anatase increased up to 700 °C. Transition electron microscopy (TEM) showed that crystallites with a size in the range of 20–50 nm with equiaxed morphology were obtained after milling in corundum and annealing at 600 and 700 °C. The process of photoinduced reactive hydroxyl radical generation in aerated aqueous titania suspensions was studied by EPR spectroscopy using spin trapping technique. The presence of iron impurities in the samples milled in steel substantially decreases the radical formation. The rate of radical formation is substantially affected by particle size development of TiO₂ nanopowders. The product milled in corundum and annealed at 700 °C outperforms more than twice the photochemical activity of TiO₂ Degussa P25 standard.     

Preparation for exchange-coupled permanent magnetic composite between α-Fe (soft) and Nd2Fe14B (hard)

Soft magnetic α-Fe nanoparticles were prepared by a coprecipitation route and hard magnetic Nd₁₅Fe₇₇B₈ nanoparticles were prepared by ball milling for 20 h by using a shaker mill. A mechanical ball-mill technique was applied to build up exchange-coupled nanoparticles. A mixture of Nd₂Fe₁₄B and α-Fe nanoparticles in a stainless steel boat was milled for 2 h and annealed in a vacuum furnace under vacuum (∼10⁻⁵ Torr) at 650 °C for 30 min. The crystal structure of the nanoparticles was confirmed by using X-ray powder diffraction (XRD). The surface morphology was identified by FE-SEM. The magnetization curve was measured with a vibrating-sample magnetometer (VSM). Thermogravimetry using a microbalance with magnetic field gradient positioned below the sample was used for the measurement of a thermomagnetic analysis (TMA) curve showing the downward magnetic force versus temperature.     

Sonochemical synthesis of Dy2(CO3)3 nanoparticles,Dy(OH)3 nanotubes and their conversion to Dy2O3 nanoparticles

Dysprosium carbonates nanoparticles were synthesized by the reaction of dysprosium acetate and NaHCO₃ by a sonochemical method. Dysprosium oxide nanoparticles with average size about 17 nm were prepared from calcination of Dy₂(CO₃)₃·1.7H₂O nanoparticles. Dy(OH)₃ nanotubes were synthesized by sonication of Dy(OAC)₃·6H₂O and N₂H₄. The as-synthesized nanostructures were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR). Photoluminescence measurement shows that the nanoparticles have two emission peaks around 17,540 cm^?1 and 20,700 cm^?1, which should come from the electron transition from ⁴F_9/2 → ⁶H_15/2 levels and ⁴F_9/2 → ⁶H_13/2 levels, respectively. The effect of calcination temperature and sonication time was investigated on the morphology and particle size of the products. The sizes could be controlled by the feeding rate of the precipitating agent (NaHCO₃ and N₂H₄) and slower feeding rate lead to smaller nanoparticles.     

Ultrasonic-assisted degradation of phenazopyridine with a combination of Sm-doped ZnO nanoparticles and inorganic oxidants

Pure and samarium doped ZnO nanoparticles were synthesized by a sonochemical method and characterized by TEM, SEM, EDX, XRD, Pl, and DRS techniques. The average crystallite size of pure and Sm-doped ZnO nanoparticles was about 20 nm. The sonocatalytic activity of pure and Sm-doped ZnO nanoparticles was considered toward degradation of phenazopyridine as a model organic contaminant. The Sm-doped ZnO nanoparticles with Sm concentration of 0.4 mol% indicated a higher sonocatalytic activity (59%) than the pure ZnO (51%) and other Sm-doped ZnO nanoparticles. It was believed that Sm³⁺ ion with optimal concentration (0.4 mol%) can act as superficial trapping for electrons in the conduction band of ZnO and delayed the recombination of charge carriers. The influence of the nature and concentration of various oxidants, including periodate, hydrogen peroxide, peroxymonosulfate, and peroxydisulfate on the sonocatalytic activity of Sm-doped ZnO nanoparticles was studied. The influence of the oxidants concentration (0.2–1.4 g L⁻¹) on the degradation rate was established by the 3D response surface and the 2D contour plots. The results demonstrated that the utilizing of oxidants in combination with Sm-doped ZnO resulting in rapid removal of contaminant, which can be referable to a dual role of oxidants; (i) scavenging the generated electrons in the conduction band of ZnO and (ii) creating highly reactive radical species under ultrasonic irradiation. It was found that the Sm-doped ZnO and periodate combination is the most efficient catalytic system under ultrasonic irradiation.     

Densities and volumetric properties of 2-chloroethanol with N,N-dimethylformamide and water at different temperatures

Densities of binary mixtures of 2-chloroethanol with N,N-dimethylformamide (DMF) and water have been measured over the full range of compositions at various temperatures. From these results, excess molar volumes, V^E and excess partial molar volumes at infinite dilution, V¯_i^E,0 have been calculated. V^E for (DMF + 2-chloroethanol) mixture are positive over the whole mole fraction range and negative values are obtained for (water + 2-chloroethanol) mixture.     

Syntheses and characterization of Mg(OH)2 and MgO nanostructures by ultrasonic method

Magnesium hydroxide nanostructures have been synthesized by the reaction of magnesium acetate with sodium hydroxide via sonochemical method. Reaction conditions such as the Mg²⁺ concentration, aging time and the ultrasonic device power show important roles in the size, morphology and growth process of the final products. The magnesium oxide nanoparticles have been prepared by calcination of magnesium hydroxide nanostructures at 400 °C. The magnesium hydroxide and magnesium oxide nanostructures were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), thermal gravimetric (TG) and differential thermal analyses (DTA).     

Intensification of ultrasound-assisted process for the preparation of spindle-shape sodium zinc molybdate nanoparticles

In the present work, sodium zinc molybdate (SZM) nanoparticles were prepared using conventional and an innovative ultrasound assisted co-precipitation of sodium molybdate, zinc oxide and HNO₃ at different temperatures. Prepared product was characterized by XRD, TEM, FT-IR, particle size distribution (PSD), TGA and DTA techniques. TEM analysis shows the spindle-shaped morphology of the formed SZM nanoparticles. The average particle size of SZM nanoparticles is found to be lower in case of sonochemical method (78.3 nm) compared to conventional method (340.2 nm) which is attributed to faster solute transfer rate due to ultrasonic irradiation leading to rapid nucleation and restricted growth of SZM nanoparticles. Further, the kinetics of synthesis of SZM nanoparticles are studied using the sonochemical method at different operating temperature and conventional method at 80 °C. It is shown that the rate of reaction is significantly faster at 40 °C compared to other temperatures and also conventional method. This can be attributed to intense cavity collapse at lower temperature (low vapour pressure) compared to higher temperature (high vapour pressure) of the reaction mixture.     

Heterogeneous sono-Fenton-like process using martite nanocatalyst prepared by high energy planetary ball milling for treatment of a textile dye

High energy planetary ball milling was applied to prepare sono-Fenton nanocatalyst from natural martite (NM). The NM samples were milled for 2–6 h at the speed of 320 rpm for production of various ball milled martite (BMM) samples. The catalytic performance of the BMMs was greater than the NM for treatment of Acid Blue 92 (AB92) in heterogeneous sono-Fenton-like process. The NM and the BMM samples were characterized by XRD, FT-IR, SEM, EDX and BET analyses. The particle size distribution of the 6 h-milled martite (BMM₃) was in the range of 10–90 nm, which had the highest surface area compared to the other samples. Then, the impact of main operational parameters was investigated on the process. Complete removal of the dye was obtained at the desired conditions including initial pH 7, 2.5 g/L BMM₃ dosage, 10 mg/L AB92 concentration, and 150 W ultrasonic power after 30 min of treatment. The treatment process followed pseudo-first order kinetic. Environmentally-friendly modification of the NM, low leached iron amount and repeated application at milder pH were the significant benefits of the BMM₃. The GC–MS was successfully used to identify the generated intermediates. Eventually, an artificial neural network (ANN) was applied to predict the AB92 removal efficiency based upon the experimental data with a proper correlation coefficient (R² = 0.9836).