Search

Ultrasound-assisted extraction (UAE) and microwave-assisted extraction (MAE) techniques have been employed as complementary techniques to extract oils from vegetable sources, viz, soybean germ and a cultivated marine microalga rich in docosahexaenoic acid (DHA). Ultrasound (US) devices developed by ourselves, working at several frequencies (19, 25, 40 and 300 kHz), were used for US-based protocols, while a multimode microwave (MW) oven (operating with both open and closed vessels) was used for MAE. Combined treatments were also studied, such as simultaneous double sonication (at 19 and 25 kHz) and simultaneous US/MW irradiation, achieved by inserting a non-metallic horn in a MW oven. Extraction times and yields were compared with those resulting from conventional procedures. With soybean germ the best yield was obtained with a 'cavitating tube' prototype (19 kHz, 80 W), featuring a thin titanium cylinder instead of a conventional horn. Double sonication, carried out by inserting an immersion horn (25 kHz) in the same tube, improved the yield only slightly but halved the extraction time. Almost comparable yields were achieved by closed-vessel MAE and simultaneous US/MW irradiation. Compared with conventional methods, extraction times were reduced by up to 10-fold and yields increased by 50-500%. In the case of marine microalgae, UAE worked best, as the disruption by US of the tough algal cell wall considerably improved the extraction yield from 4.8% in soxhlet to 25.9%. Our results indicate that US and MW, either alone or combined, can greatly improve the extraction of bioactive substances, achieving higher efficiency and shorter reaction times at low or moderate costs, with minimal added toxicity.

This work investigates the effect of simultaneous ultrasound-microwave irradiation on palm oil transesterification and uncovers optimal operating conditions. Response surface methodology (RSM) has been used to analyze the influence of reaction conditions, including methanol/palm oil molar ratio, catalyst concentration, reaction temperature and irradiation time on biodiesel yield. RSM analyses indicate 136 s and 129 s as the optimal sonication and microwave irradiation times, respectively. Optimized parameters for full conversion (97.53%) are 1.09% catalyst concentration and a 7:3.1 methanol/oil molar ratio at 58.4°C. Simultaneous ultrasound-microwave irradiation dramatically accelerates the palm oil transesterification reaction. Pure biodiesel was obtained after only 2.2 min while the conventional method requires about 1 h.

BACKGROUND Microalgae are one of the most promising biofuel sources that the world has to offer; nevertheless the conversion process is hampered by technical and economic problems that are mainly related to de-watering and extraction. The efficiency of the process can be dramatically improved by means of non-conventional techniques such as ultrasound ( US) and microwaves ( MW). Scaling-up feasibility is strictly linked to reactor efficiency, energy consumption, environmental impact and overall cost. In the present work, the optimization of lipid extraction from Nannochloropsis gaditana microalga is investigated. RESULTS A series of selected solvent mixtures and procedures have been tested and compared. Conventional extraction procedures with chloroform/methanol mixtures and fast US- and MW-assisted extractions with methanol gave comparable fatty acid ( FA) w/w% from dried microalgae. The highest extraction yield and lowest energy consumption was found to occur under MW irradiation, especially at high temperatures and under pressure. CONCLUSION This study highlights the advantages of US- and MW-assisted lipid extraction from microalgae, both in terms of efficiency and operational costs. © 2013 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Kiwi seed oil has a nutritionally interesting fatty acid profile, but a rather low oxidative stability, which requires careful extraction procedures and adequate packaging and storage. For these reasons and with the aim to achieve process intensification with shorter extraction time, lower energy consumption and higher yields, four different non-conventional techniques were experimented. Kiwi seeds were extracted in hexane using classic Soxhlet as well as under power ultrasound (US), microwaves (MWs; closed vessel) and MW-integrated Soxhlet. Supercritical CO2 was also employed and compared to the other techniques in term of yield, extraction time, fatty acid profiles and organoleptic properties. All these non-conventional techniques are fast, effective and safe. A sensory evaluation test showed the presence of off-flavours in oil samples extracted by Soxhlet and US, an indicator of partial degradation. [ABSTRACT FROM AUTHOR]

This study deals with the removal of antibiotics from contaminated water and milk using pristine and modified activated carbons (ACs) from various biomass sources. Pristine ACs exhibited good removal efficiency (RE) for various antibiotics from aqueous solutions and milk. To further enhance adsorption performance, a wood powdered activated carbon (WPAC) was modified by oxidation with H 2 O 2 under shaking (SK), ultrasonication (US) and microwave (MW) heating, as well as MW calcination. As a result, US- and MW-assisted modifications lead to significantly higher adsorption performance for marbofloxacin (MAR) than pristine WPAC. An extended characterization was carried out on pristine and modified ACs to find structure-adsorption capability relationships and the results showed that the adsorption performance was promoted by the presence of newly formed/converted oxygen-containing functional groups upon modification. These groups rule the adsorption mechanism and the modifications allow adsorbent consumption and treatment costs to be greatly reduced, while providing similar adsorption performance. In particular, the removal of low concentration antibiotics from milk using ACs modified under MW-assisted calcination is efficient, economical and convenient, despite the presence of competition adsorption by impurities. In summary, adsorption using modified ACs is a highly promising technique for the decontamination of antibiotic-polluted water and milk. [Display omitted] • US-assisted activated carbon oxidation with H 2 O 2 promoted antibiotic adsorption. • MW-assisted activated carbon oxidation with H 2 O 2 promoted antibiotic adsorption. • MW calcination generates new functional groups enhancing antibiotic adsorption. • Oxygen containing surface groups improve active carbon adsorption capability. • Antibiotics were efficiently removed from water and milk by all modified activated carbons. [ABSTRACT FROM AUTHOR]

Abstract: Polyphenols, the well known naturally occurring antioxidants, are the most abundant secondary metabolites in grape wastes. Herein we investigate several non-conventional extraction methods vs classic solid–liquid extraction (SLE) to obtain phenolic compounds from grape seeds and skins. We compared SLE, ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE) and high pressure and temperature extraction (HPTE) in term of extraction yield and antioxidant power of the extract. Solvent of choice between methanol and ethanol was the former, both for skins and seeds. Quali-quantitative analyses were performed using colorimetric and HPLC methods. The highest content in total polyphenols, o-diphenols and flavonoids, both for seeds (108.3, 47.0mgGAE gDW −1, 47.2mgCE gDW −1) and skins (34.2, 10.1mgGAE gDW −1, 21.6mgCE gDW −1) was obtained with HPTE working in a Parr reactor. While the highest antiradical power was determined in seeds extracts from MAE (78.6μlextract μgDPPH −1). Prolonged extraction times (over 30min) further increased the amount of total polyphenols, while progressively decreased the amount of flavonoids and the antiradical power. [Copyright &y& Elsevier]

Highlights: [•] Fast dehalogenations of polychlorinated aromatics and PCBs. [•] Efficient metal activation and dispersion under ultrasound or high-speed mixing. [•] Dechlorination reactions under dielectric heating and acoustic cavitation. [•] Enabling technologies for chemical process intensification and safer protocols. [Copyright &y& Elsevier]

Abstract: Mitragyna speciosa, a tropical plant indigenous to Southeast Asia, is well known for its psychoactive properties. Its leaves are traditionally chewed by Thai and Malaysian farmers and manual labourers as it causes a numbing, stimulating effect. The present study aims to evaluate alkaloid yield and composition in the leaf extracts. For this purpose we have compared several non-conventional extraction techniques with classic procedures (room temperature or under heating). Dried M. speciosa leaves belonging to three batches of different origin (from Thailand, Malaysia and Indonesia) were extracted using ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE) and supercritical carbon dioxide extraction SFE-CO2, using methanol, ethanol, water and binary mixtures. The extracts were compared using an HPLC/ESI-MS analysis of mitragynine and four other related alkaloids which were present in the alkaloid fraction. The extraction technique influences both the raw product yield and the relative alkaloid content of M. speciosa leaves. Of the several methods tested, MAE in a closed vessel at 110°C (60W, methanol/water 1:1) gave the highest alkaloid fraction amount, while UAE with an immersion horn at 25°C (21.4kHz, 50W, methanol) showed the best yield for mitragynine. This work may prove to be a useful contribution to forensic, toxicological and pharmacognosy studies. Although the potential applications of M. speciosa alkaloids clearly need further investigation, these results may facilitate the scaling-up of their extraction. [Copyright &y& Elsevier]