Displaying publications 41 - 60 of 126 in total

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  1. Fujita M, Lévêque JM, Komatsu N, Kimura T
    Ultrason Sonochem, 2015 Nov;27:247-51.
    PMID: 26186842 DOI: 10.1016/j.ultsonch.2015.04.030
    A novel, mild "sono-halogenation" of various aromatic compounds with potassium halide was investigated under ultrasound in a biphasic carbon tetrachloride/water medium. The feasibility study was first undertaken with the potassium bromide and then extended to chloride and iodide analogues. This methodology could be considered as a new expansion of the ultrasonic advanced oxidation processes (UAOPs) into a synthetic aspect as the developed methodology is linked to the sonolytic disappearance of carbon tetrachloride. Advantages of the present method are not only that the manipulation of the bromination is simple and green, but also that the halogenating agents used are readily available, inexpensive, and easy-handling.
  2. Tiong TJ, Low LE, Teoh HJ, Chin JK, Manickam S
    Ultrason Sonochem, 2015 Nov;27:165-70.
    PMID: 26186833 DOI: 10.1016/j.ultsonch.2015.04.033
    Ultrasonic VialTweeter is used for the sonication of small volume samples. It contains a titanium block with 8 holes for vial insertion, to be used simultaneously for batch operation. In this investigation, the ultrasonic and sonochemical performance of ultrasonic VialTweeter has been evaluated at its different positions. Experimental results using calorimetry, ultrasonic capillary effect, sonochemiluminescence and degradation of Rhodamine B showed that the sonochemical activity differs greatly at different positions along the VialTweeter, with positions 3 and 4 showing the maximum efficiency whereas the positions 1 and 2 being the least effective positions. These results were further verified by acoustic pressure simulation, confirming that certain locations in the VialTweeter may not perform in the same way as others due to the variation in acoustic pressure at different locations.
  3. Yusof NS, Babgi B, Alghamdi Y, Aksu M, Madhavan J, Ashokkumar M
    Ultrason Sonochem, 2016 Mar;29:568-76.
    PMID: 26142078 DOI: 10.1016/j.ultsonch.2015.06.013
    Acoustic cavitation in a liquid medium generates several physical and chemical effects. The oscillation and collapse of cavitation bubbles, driven at low ultrasonic frequencies (e.g., 20 kHz), can generate strong shear forces, microjets, microstreaming and shockwaves. Such strong physical forces have been used in cleaning and flux improvement of ultrafiltration processes. These physical effects have also been shown to deactivate pathogens. The efficiency of deactivation of pathogens is not only dependent on ultrasonic experimental parameters, but also on the properties of the pathogens themselves. Bacteria with thick shell wall are found to be resistant to ultrasonic deactivation process. Some evidence does suggest that the chemical effects (radicals) of acoustic cavitation are also effective in deactivating pathogens. Another aspect of cleaning, namely, purification of water contaminated with organic and inorganic pollutants, has also been discussed in detail. Strong oxidising agents produced within acoustic cavitation bubbles could be used to degrade organic pollutants and convert toxic inorganic pollutants to less harmful substances. The effect of ultrasonic frequency and surface activity of solutes on the sonochemical degradation efficiency has also been discussed in this overview.
  4. Fayyazi E, Ghobadian B, Najafi G, Hosseinzadeh B, Mamat R, Hosseinzadeh J
    Ultrason Sonochem, 2015 Sep;26:312-20.
    PMID: 25870003 DOI: 10.1016/j.ultsonch.2015.03.007
    Biodiesel is a green (clean), renewable energy source and is an alternative for diesel fuel. Biodiesel can be produced from vegetable oil, animal fat and waste cooking oil or fat. Fats and oils react with alcohol to produce methyl ester, which is generally known as biodiesel. Because vegetable oil and animal fat wastes are cheaper, the tendency to produce biodiesel from these materials is increasing. In this research, the effect of some parameters such as the alcohol-to-oil molar ratio (4:1, 6:1, 8:1), the catalyst concentration (0.75%, 1% and 1.25% w/w) and the time for the transesterification reaction using ultrasonication on the rate of the fatty acids-to-methyl ester (biodiesel) conversion percentage have been studied (3, 6 and 9 min). In biodiesel production from chicken fat, when increasing the catalyst concentration up to 1%, the oil-to-biodiesel conversion percentage was first increased and then decreased. Upon increasing the molar ratio from 4:1 to 6:1 and then to 8:1, the oil-to-biodiesel conversion percentage increased by 21.9% and then 22.8%, respectively. The optimal point is determined by response surface methodology (RSM) and genetic algorithms (GAs). The biodiesel production from chicken fat by ultrasonic waves with a 1% w/w catalyst percentage, 7:1 alcohol-to-oil molar ratio and 9 min reaction time was equal to 94.8%. For biodiesel that was produced by ultrasonic waves under a similar conversion percentage condition compared to the conventional method, the reaction time was decreased by approximately 87.5%. The time reduction for the ultrasonic method compared to the conventional method makes the ultrasonic method superior.
  5. Masri AN, Abdul Mutalib MI, Yahya WZN, Aminuddin NF, Leveque JM
    Ultrason Sonochem, 2020 Jan;60:104732.
    PMID: 31499322 DOI: 10.1016/j.ultsonch.2019.104732
    Biodiesel production via esterification/transesterification reactions can be catalyzed by homogenous or heterogeneous catalysts. Development of heterogeneous catalysts for biodiesel production is highly advantageous due to the ease of product purification and of catalyst recyclability. In this current work, a novel acidic [DABCODBS][CF3SO3]2 dicationic ionic liquid (DIL) was used as heterogeneous catalyst to produce biodiesel using oleic acid as model oil. The esterification was conducted under ultrasonic irradiation (20 kHz) using a 14 mm ultrasonic horn transducer operated at various duty cycles. It was observed that the duty cycle, amplitude, methanol to oil molar ratio, catalyst amount and reaction temperature were the major factors that greatly impact the necessary reaction time to lead to a high yield of biodiesel. The reaction conditions were optimized with the aid of Response Surface Methodology (RSM) designed according to the Quadratic model of the Box Behnken method. The optimum conditions were found to be at catalyst amount of 0.64 mol%, methanol to oil ratio of 14.3:1, temperature of 59 °C, reaction time of 83 min and amplitude of 60% in continuous mode. The results showed that the oleic acid was successfully converted into esters with conversion value of 93.20% together with significant reduction of reaction time from 7 h (using mechanical stirring) to 83 min (using ultrasonication). The results also showed that the acidic DIL catalyst we designed purposely was efficient to catalyze the ultrasonic-assisted esterification yielding high conversion of oleic acid to methyl oleate on short times. The DIL was also recycled and reused for at least five times without significant reduction in performance. Overall, the procedureoffersadvantages including short reaction time, good yield, operational simplicity and environmentally benign characteristics.
  6. Bayrami A, Ghorbani E, Rahim Pouran S, Habibi-Yangjeh A, Khataee A, Bayrami M
    Ultrason Sonochem, 2019 Nov;58:104613.
    PMID: 31450359 DOI: 10.1016/j.ultsonch.2019.104613
    The leaf extract of a medicinally important plant, watercress (Nasturtium officinale), was obtained through an ultrasound-facilitated method and utilized for the preparation of ZnO nanoparticles via a joint ultrasound-microwave assisted procedure. The characteristics of the extract enriched nanoparticles (Ext/ZnO) were determined by SEM, TEM, XRD, EDX, BET, FTIR, TGA, and UV-Vis DRS analyses and compared to that of ZnO prepared in the absence of the extract (ZnO). The presence of carbon and carbonaceous bonds, changes in the morphology, size, band gap energy, and weight-decay percentage were a number of differences between ZnO and Ext/ZnO that confirmed the link of extract over nanoparticles. Ext/ZnO, watercress leaf extract, ZnO, and insulin therapies were administrated to treat alloxan-diabetic Wister rats and their healing effectiveness results were compared to one another. The serum levels of the main diabetic indices such as insulin, fasting blood glucose, and lipid profile (total triglyceride, total cholesterol, and high-density lipoprotein cholesterol) were estimated for healthy, diabetic, and the rats rehabilitated with the studied therapeutic agents. The watercress extract-enriched ZnO nanoparticles offered the best performance and suppressed the diabetic status of rats. Moreover, both ZnO samples satisfactory inhibited the activities of Staphylococcus aureus and Escherichia coli bacteria. Based on the results, the application of Nasturtium officinale leaf extract can strongly empower ZnO nanoparticles towards superior antidiabetic and enhanced antibacterial activities.
  7. Hwa KY, Karuppaiah P, Gowthaman NSK, Balakumar V, Shankar S, Lim HN
    Ultrason Sonochem, 2019 Nov;58:104649.
    PMID: 31450344 DOI: 10.1016/j.ultsonch.2019.104649
    Hydroquinone (HQ), a phenolic compound is expansively used in many industrial applications and due to the utilization of HQ, water pollution tragedies frequently found by the improper handling and accidental outflows. When HQ is adsorbed directly through the skin that create toxic effects to human by affecting kidney, liver, lungs, and urinary tract and hence, a highly selective and sensitive technique is required for its quantification. Herein, we have developed the ultrasonic synthesis of copper oxide nanoflakes (CuO-NFs) using ultrasonic bath (20 kHz, 100 W) and successfully employed for the sensitive detection of the environmental hazardous pollutant HQ. The formed CuO-NFs were confirmed by X-ray diffraction, field emission scanning electron microscopy (FE-SEM), FT-IR spectroscopy and UV-visible spectroscopy and fabricated with the screen-printed carbon electrode (SPCE). The SEM images exhibited the uniform CuO-NFs with an average width of 85 nm. The linker-free CuO-NFs fabricated electrode showed the appropriate wide range of concentrations from 0.1 to 1400 µM and the limit of detection was found to be 10.4 nM towards HQ. The fabricated sensor having long term stability and sensitivity was successfully applied for the environmental and commercial real sample analysis and exhibited good recovery percentage, implying that the SPCE/CuO-NFs is an economically viable and benign robust scaffold for the determination of HQ.
  8. Ong VZ, Wu TY, Lee CBTL, Cheong NWR, Shak KPY
    Ultrason Sonochem, 2019 Nov;58:104598.
    PMID: 31450331 DOI: 10.1016/j.ultsonch.2019.05.015
    This study demonstrated the effect of two-pot sequential pretreatment, comprising of ultrasound assisted deep eutectic solvent (DES) with the aim to investigate the effects of ultrasound amplitude and duration in enhancing delignification. Oil palm fronds (OPF) were ultrasonicated in a water medium, followed by a pretreatment using DES (choline chloride:urea). Fourier transform infra-red spectroscopy, X-ray diffraction, field emission scanning electron microscope, Brunauer-Emmet-Teller and solubilised lignin concentration were conducted to confirm the effectiveness of ultrasound assisted DES on the pretreatment of OPF. The recommended ultrasound conditions were determined to be 70% amplitude and duration of 30 min, where the sequential DES pretreatment was able to reduce lignin content of OPF to 14.01%, while improving xylose recovery by 58%.
  9. Iqbal MZ, Khan A, Numan A, Haider SS, Iqbal J
    Ultrason Sonochem, 2019 Dec;59:104736.
    PMID: 31473424 DOI: 10.1016/j.ultsonch.2019.104736
    An upsurge in sustainable energy demands has ultimately made supercapattery one of the important choice for energy storage, owing to highly advantageous energy density and long life span. In this work, novel strontium based mixed phased nanostructures were synthesized by using probe sonicator with sonication power 500 W at frequency of 20 kHz. The synthesized material was subsequently calcined at different temperature ranging from 200 to 800 °C. Structural and morphological analysis of the synthesized materials reveals the formation of mixed particle and rod like nanostructures with multiple crystal phases of strontium oxides and carbonates. Crystallinity, grain size and morphology of grown nanomaterials significantly improved with the increase of calcination temperature due to sufficient particle growth and low agglomeration. The electrochemical performance analysis confirms the redox activeness of the Sr-based electrode materials. Material calcined at 600 °C show high specific capacitance of 350 F g-1 and specific capacity of 175 C g-1 at current density of 0.3 A g-1 due to less particle agglomeration, good charge transfer and more contribution of electrochemical active sites for redox reactions. In addition, the developed supercapattery of Sr-based nanomaterials//activated carbon demonstrated high performance with maximum energy density of 21.8 Wh kg-1 and an excellent power density of 2400 W kg-1 for the lower and higher current densities. Furthermore, the supercapattery retain 87% of its capacity after continuous 3000 charge/discharge cycles. The device characteristics were further investigated by analyzing the capacitive and diffusion controlled contributions. The versatile strategy of developing mixed phased nanomaterials pave the way to synthesize other transition metal based nanomaterials with superior electrochemical performance for hybrid energy storage devices.
  10. Raviadaran R, Ng MH, Manickam S, Chandran D
    Ultrason Sonochem, 2019 Apr;52:353-363.
    PMID: 30555038 DOI: 10.1016/j.ultsonch.2018.12.012
    This study aimed to formulate a stable palm oil-based water-in-oil (W/O) nano-emulsion. Emphasis was placed on the effects of polyglycerol polyricinoleate (PGPR), medium chain triglyceride (MCT), lecithin and sodium chloride (NaCl) addition towards the stability of nano-emulsion. Among the performed analyses were mean droplet diameter (MDD), dispersity index (DI), critical micelle concentration (CMC), lipid peroxidation, viscosity, sedimentation index (SI) and surface morphology. The most stable optimized palm oil-based W/O nano-emulsion was produced using 61.25 wt% of palm oil, 26.25 wt% of MCT, 2.5 wt% of PGPR and 10 wt% of water (0.5 M of NaCl). The MDD and DI of the obtained W/O nano-emulsion were 143.1 ± 8.8 and 0.131 ± 0.094, respectively. After 2 weeks, no sedimentation was observed in W/O nano-emulsion with MDD and DI were 151.2 ± 6.5 nm and 0.156 ± 0.025 respectively. This study clearly found that polyricinoleate non-polar fatty acids of PGPR bound to non-polar fatty acids of palm oil through van der Waals intermolecular forces. While, polyglycerol polar head of PGPR interacts with water molecules through hydrogen bonding, as well as by the bound glyceride units of palm oil. The addition of NaCl further reduced MDD by 70 nm and improved the stability of nano-emulsion through electrostatic and steric repulsions attributed to the dissociation of Na+ and Cl- ions. This study aids to widen the knowledge and interest on the utilization of palm oil for the generation of W/O nano-emulsion, as well as to better understand the interaction between palm oil and PGPR/NaCl in producing nano-emulsion.
  11. Tahmasebi-Boldaji R, Hatamipour MS, Khanahmadi M, Sadeh P, Najafipour I
    Ultrason Sonochem, 2019 Oct;57:89-97.
    PMID: 31208622 DOI: 10.1016/j.ultsonch.2019.05.018
    This paper presents the successful application of ultrasound-assisted packed-bed (UAE-PB) method for the extraction of hypericin from the Hypericum perfuratum L. The Soxhlet system was utilized for the determination of suitable solvent from ethanol, methanol or from the mixture of different proportions of ethanol-methanol. The mixture of 50:50 v/v ethanol-methanol was obtained to be the most suitable solvent since it led to the highest extraction amount of hypericin. The extraction amount of hypericin increased by 13.6% and 21.4% when the solvent changed from pure methanol to the mixture of 50:50 v/v ethanol-methanol for the extraction time of 3 and 8 h, respectively. Subsequently, the extraction was conducted through the UAE-PB, and the effects of temperature, time, and the ratio of solvent to the dried plant were studied. The response surface method (RSM) was used to investigate the effect of parameters on the extraction in the UAE-PB system. At the temperature of 60 °C, extraction time of 105 min, and the solvent to plant ratio of 15.3, the maximum extraction yield of hypericin was achieved. In the optimal conditions, the amount of extraction was 0.112 mg hypericin/g dried plant, which was in accordance with the optimized predicted value (0.111 mg hypericin/g dried plant) from Design-Expert software.
  12. Manickam S, Sivakumar K, Pang CH
    Ultrason Sonochem, 2020 Dec;69:105258.
    PMID: 32702637 DOI: 10.1016/j.ultsonch.2020.105258
    O/W nanoemulsions are isotropic colloidal systems constituted of oil droplets dispersed in continuous aqueous media and stabilised by surfactant molecules. Nanoemulsions hold applications in more widespread technological domains, more crucially in the pharmaceutical industry. Innovative nanoemulsion-based drug delivery system has been suggested as a powerful alternative strategy through the useful means of encapsulating, protecting, and delivering the poorly water-soluble bioactive components. Consequently, there is a need to generate an emulsion with small and consistent droplets. Diverse studies acknowledged that ultrasonic cavitation is a feasible and energy-efficient method in making pharmaceutical-grade nanoemulsions. This method offers more notable improvements in terms of stability with a lower Ostwald ripening rate. Meanwhile, a microstructured reactor, for instance, microchannel, has further been realised as an innovative technology that facilitates combinatorial approaches with the acceleration of reaction, analysis, and measurement. The recent breakthrough that has been achieved is the controlled generation of fine and monodispersed multiple emulsions through microstructured reactors. The small inner dimensions of microchannel display properties such as short diffusion paths and high specific interfacial areas, which increase the mass and heat transfer rates. Hence, the combination of ultrasonic cavitation with microstructures (microchannel) provides process intensification of creating a smaller monodispersed nanoemulsion system. This investigation is vital as it will then facilitate the creation of new nanoemulsion based drug delivery system continuously. Following this, the fabrication of microchannel and setup of its combination with ultrasound was conducted in the generation of O/W nanoemulsion, as well as optimisation to analyse the effect of varied operating parameters on the mean droplet diameter and dispersity of the nanoemulsion generated, besides monitoring the stability of the nanoemulsion. Scanning transmission electron microscopy (STEM) images were also carried out for the droplet size measurements. In short, the outcomes of this study are encouraging, which necessitates further investigations to be carried out to advance a better understanding of coupling microchannel with ultrasound to produce pharmaceutical-grade nanoemulsions.
  13. Siva SP, Kow KW, Chan CH, Tang SY, Ho YK
    Ultrason Sonochem, 2019 Jul;55:348-358.
    PMID: 30871878 DOI: 10.1016/j.ultsonch.2018.12.040
    The dynamics of droplet breakup during emulsification is a complicated process due to the interplay between multiple physico-chemical and hydrodynamic factors, especially in an energy-intensive ultrasound-assisted emulsification process. In this work, by mapping the physical processing parameters of ultrasound emulsification into a reduced domain that is governed by the power density and the initial average droplet diameter, a dimensionless parameter that resembles the dynamic breakup potential (η) was established via dimensional analysis. In addition to shedding important insights into the emulsification process, η further facilitates the establishment of a transient scaling relationship that is a function of the characteristic value (a) of the emulsion system. Experimental case study on a cellulose nanocrystals (CNC)-based olein-in-water emulsion system prepared via ultrasound cavitation confirmed the validity of the scaling relationship and sub-universal self-similarity was observed. Using the proposed model, good predictions of the transient of droplet size evolution were attained where the value of η, i.e. the proportionality constant, can be conveniently computed using data from a single time point. Application on other emulsion systems further suggested that the value of a possibly indicates the relative minimum size limit of a particular fluids-emulsifier system. Our approach is general, which encourages widespread adoption for emulsification related studies.
  14. Mohammadi P, Karami N, Zinatizadeh AA, Falahi F, Aghamohammadi N, Almasi A
    Ultrason Sonochem, 2019 Jan 22.
    PMID: 30712854 DOI: 10.1016/j.ultsonch.2019.01.030
    In this study, high-frequency ultrasound wave (1.8 MHz) at low intensity was applied to improve activated sludge settleability at high MLSS concentration. The effect of irradiation intensity, sonication mode, MLSS concentration and sample volume on the physical characteristics of sludge in a pilot scale settling column were investigated for optimizing the conditions. The obtained results showed that high-frequency ultrasound decreased the height of sludge (44%) and effluent turbidity (82.2%) and increased sludge settling velocity about 3 times at high biomass concentration. Irradiation intensity of 0.4 w/cm2 and sonication mode with interval times of 10 s showed the best results on the performance of the system at MLSS concentration of 8000 mg/L with a sample volume of 3 L.
  15. Shi X, Karachi A, Hosseini M, Yazd MS, Kamyab H, Ebrahimi M, et al.
    Ultrason Sonochem, 2020 Nov;68:104460.
    PMID: 30712851 DOI: 10.1016/j.ultsonch.2019.01.018
    The aim of this study was ultrasound assisted removal of Ceftriaxone sodium (CS) based on CCD model. Using sonochemical synthesized Bi2WO6 implanted on graphitic carbon nitride/Multiwall carbon nanotube (g-C3N4/MWCNT/Bi2WO6). For this purpose g-C3N4/MWCNT/Bi2WO6 was synthesized and characterized using diverse approaches including XRD, FE-SEM, XPS, EDS, HRTEM, FT-IR. Then, the contribution of conventional variables including pH, CS concentration, adsorbent dosage and ultrasound contact time were studied by central composite design (CCD) under response surface methodology (RSM). ANOVA was employed to the variable factors, and the most desirable operational conditions mass provided. Drug adsorption yield of 98.85% obtained under these defined conditions. Through conducting five experiments, the proper prediction of the optimum point were examined. The respective results showed that RSD% was lower than 5% while the t-test confirmed the high quality of fitting. Langmuir isotherm equation fits the experimental data best and the removal followed pseudo-second order kinetics. The estimation of the experimentally obtained maximum adsorption capacities was 19.57 mg.g- of g-C3N4/MWCNT/Bi2WO6 for CS. Boundary layer diffusion explained the mechanism of removal via intraparticle diffusion.
  16. Krishnan S, Abd Ghani N, Aminuddin NF, Quraishi KS, Razafindramangarafara BL, Baup S, et al.
    Ultrason Sonochem, 2021 Jun;74:105576.
    PMID: 33975186 DOI: 10.1016/j.ultsonch.2021.105576
    This study investigates the potential of using small amounts of ionic liquids (IL) to enhance ultrasound-assisted extraction of lipids content from green microalgae. Three imidazolium-based ILs (butyl, octyl and dodecyl), each of them with two anions (bromide and acetate) were tested as additives. Viscosity and surface tension of the ILs aqueous mixtures were analyzed to determine the influence of ILs' anions and alkyl chain length, whereas KI dosimetry experiments were used as an indicator of radicals formation. A key finding suggests that the small addition of ILs improves the ultrasonication either by enhancing the viscosity and reducing the water surface tension, leading to a more powerful acoustic cavitation process or by increasing HO° production likely to oxidize the microalgae cells membranes, and consequently disrupting them on a more efficient manner. KI dosimetry also revealed that long ILs alkyl chain is detrimental. This experimental observation is confirmed thus strengthened as the yield of extracted lipids from green microalgae has shown an incremental trend when the IL concentration also increased. These hypotheses are currently under investigation to spot detailed impact of ILs on cavitation process.
  17. Wang H, Tao Y, Li Y, Wu S, Li D, Liu X, et al.
    Ultrason Sonochem, 2021 May;73:105486.
    PMID: 33639530 DOI: 10.1016/j.ultsonch.2021.105486
    In this work, low-intensity ultrasonication (58.3 and 93.6 W/L) was performed at lag, logarithmic and stationary growth phases of Lactobacillus plantarum in apple juice fermentation, separately. Microbial responses to sonication, including microbial growth, profiles of organic acids profile, amino acids, phenolics, and antioxidant capacity, were examined. The results revealed that obvious responses were made by Lactobacillus plantarum to ultrasonication at lag and logarithmic phases, whereas sonication at stationary phase had a negligible impact. Sonication at lag and logarithmic phases promoted microbial growth and intensified biotransformation of malic acid to lactic acid. For example, after sonication at lag phase for 0.5 h, microbial count and lactic acid content in the ultrasound-treated samples at 58.3 W/L reached 7.91 ± 0.01 Log CFU/mL and 133.70 ± 7.39 mg/L, which were significantly higher than that in the non-sonicated samples. However, the ultrasonic effect on microbial growth and metabolism of organic acids attenuated with fermentation. Moreover, ultrasonication at lag and logarithmic phases had complex influences on the metabolism of apple phenolics such as chlorogenic acid, caffeic acid, procyanidin B2, catechin and gallic acid. Ultrasound could positively affect the hydrolysis of chlorogenic acid to caffeic acid, the transformation of procyanidin B2 and decarboxylation of gallic acid. The metabolism of organic acids and free amino acids in the sonicated samples was statistically correlated with phenolic metabolism, implying that ultrasound may benefit phenolic derivation by improving the microbial metabolism of organic acids and amino acids.
  18. Lim MSW, Yang TC, Tiong TJ, Pan GT, Chong S, Yap YH
    Ultrason Sonochem, 2021 May;73:105490.
    PMID: 33609992 DOI: 10.1016/j.ultsonch.2021.105490
    Sequentially precipitated Mg-promoted nickel-silica catalysts with ageing performed under various ultrasonic intensities were employed to study the catalyst performance in the partial hydrogenation of sunflower oil. Results from various characterisation studies showed that increasing ultrasonic intensity caused a higher degree of hydroxycarbonate erosion and suppressed the formation of Ni silicates and silica support, which improved Ni dispersion, BET surface area and catalyst reducibility. Growth of silica clusters on the catalyst aggregates were observed in the absence of ultrasonication, which explained the higher silica and nickel silicate content on the outer surface of the catalyst particle. Application of ultrasound also altered the electron density of the Ni species, which led to higher activity and enhanced product selectivity for sonicated catalysts. The catalyst synthesised with ultrasonic intensity of 20.78 Wcm-2 achieved 22.6% increase in hydrogenation activity, along with 28.5% decrease in trans-C18:1 yield at IV = 70, thus supporting the feasibility of such technique.
  19. Tao Y, Li D, Siong Chai W, Show PL, Yang X, Manickam S, et al.
    Ultrason Sonochem, 2021 Apr;72:105410.
    PMID: 33341708 DOI: 10.1016/j.ultsonch.2020.105410
    This study aimed at investigating the performances of air drying of blackberries assisted by airborne ultrasound and contact ultrasound. The drying experiments were conducted in a self-designed dryer coupled with a 20-kHz ultrasound probe. A numerical model for unsteady heat and mass transfer considering temperature dependent diffusivity, shrinkage pattern and input ultrasonic energies were applied to explore the drying mechanism, while the energy consumption and quality were analyzed experimentally. Generally, both airborne ultrasound and contact ultrasound accelerated the drying process, reduced the energy consumption and enhanced the retentions of blackberry anthocyanins and organic acids in comparison to air drying alone. At the same input ultrasound intensity level, blackberries received more ultrasound energies under contact sonication (0.299 W) than airborne sonication (0.245 W), thus avoiding the attenuation of ultrasonic energies by air. The modeling results revealed that contact ultrasound was more capable than airborne ultrasound to intensify the inner moisture diffusion and heat conduction, as well as surface exchange of heat and moisture with air. During air drying, contact ultrasound treatment eliminated the gradients of temperature and moisture inside blackberry easier than airborne ultrasound, leading to more homogenous distributions. Moreover, the total energy consumption under air drying with contact ultrasound assistance was 27.0% lower than that with airborne ultrasound assistance. Besides, blackberries dehydrated by contact ultrasound contained more anthocyanins and organic acids than those dried by airborne ultrasound, implying a higher quality. Overall, direct contact sonication can well benefit blackberry drying in both energy and quality aspects.
  20. Vallejo-Domínguez D, Rubio-Rosas E, Aguila-Almanza E, Hernández-Cocoletzi H, Ramos-Cassellis ME, Luna-Guevara ML, et al.
    Ultrason Sonochem, 2021 Apr;72:105417.
    PMID: 33352467 DOI: 10.1016/j.ultsonch.2020.105417
    Recently, chitin and chitosan are widely investigated for food preservation and active packaging applications. Chemical, as well as biological methods, are usually adopted for the production of these biopolymers. In this study, modification to a chemical method of chitin synthesis from shrimp shells has been proposed through the application of high-frequency ultrasound. The impact of sonication time on the deproteinization step of chitin and chitosan preparation was examined. The chemical identities of chitin and chitosan were verified using infrared spectroscopy. The influence of ultrasound on the deacetylation degree, molecular weight and particle size of the biopolymer products was analysed. The microscopic characteristics, crystallinity and the colour characteristics of the as-obtained biopolymers were investigated. Application of ultrasound for the production of biopolymers reduced the protein content as well as the particle size of chitin. Chitosan of high deacetylation degree and medium molecular weight was produced through ultrasound assistance. Finally, the as-derived chitosan was applied for beef preservation. High values of luminosity, chromatid and chrome were noted for the beef samples preserved using chitosan films, which were obtained by employing biopolymer subjected to sonication for 15, 25 and 40 min. Notably; these characteristics were maintained even after ten days of packaging. The molecular weight of these samples are 73.61 KDa, 86.82 KDa and 55.66 KDa, while the deacetylation degree are 80.60%, 92.86% and 94.03%, respectively; in the same order, the particle size of chitosan are 35.70 μm, 25.51 μm and 20.10 μm.
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