High frequency ultrasound as a selective advanced oxidation process to remove penicillinic antibiotics and eliminate its antimicrobial activity from water

This work studies the sonochemical degradation of a penicillinic antibiotic (oxacillin) in simulated pharmaceutical wastewater. High frequency ultrasound was applied to water containing the antibiotic combined with mannitol or calcium carbonate. In the presence of additives, oxacillin was efficiently removed through sonochemical action. For comparative purposes, the photo-Fenton, TiO₂ photocatalysis and electrochemical oxidation processes were also tested. Therefore, the evolution of the antibiotic and its associated antimicrobial activity (AA) were monitored. A high inhibition was found for the other three oxidation processes in the elimination of the antimicrobial activity caused by the additives; while for the ultrasonic treatment, a negligible effect was observed. The sonochemical process was able to completely degrade the antibiotic, generating solutions without AA. In fact, the elimination of antimicrobial activity showed an excellent performance adjusted to exponential kinetic-type decay. The main sonogenerated organic by-products were determined by means of HPLC-MS. Four intermediaries were identified and they have modified the penicillinic structure, which is the moiety responsible for the antimicrobial activity. Additionally, the possible oxacillin sonodegradation mechanism was proposed based on the evolution of the by-products and their chemical structure. Furthermore, the high-frequency ultrasound action over 120 min readily removed oxacillin and eliminated its antimicrobial activity. However, the pollutant was not mineralized even after a long period of ultrasonic irradiation (360 min). Interestingly, the previously sonicated water containing oxacillin and both additives was completely mineralized using non-adapted microorganisms from a municipal wastewater treatment plant. These results show that the sonochemical treatment transformed the initial pollutant into substances that are biotreatable with a typical aerobic biological system.     

Sonochemie: Bildung von C3S2 neben Sx (x = 6, 7, 8) durch Einwirkung von Ultraschall auf CS2

Sonochemistry: C₃S₂ Originated by Ultrasounding Carbondisulfide Pure carbondisulfide was treated with ultrasound of a frequency of 20 kHz. Consequently small amounts of C₃S₂, S₆, S₇, and S₈ were obtained, which could be separated gas-chromatographically and detected by mass spectroscopy. The yields were approximately proportional to the period of influence.     

Ultrasonic assisted synthesis of a tetrazine functionalized MOF and its application in colorimetric detection of phenylhydrazine

TMU-34(-2H), [Zn(OBA)(DPT)_0.5].DMF, has been sonochemically synthesized by applying H₂OBA, (4,4′-oxybis(benzoic acid)), as the dicarboxylate linker, and DPT, (3,6-di(pyridin-4-yl)-1,2,4,5-tetrazine), as pillar spacer. Sonication time, concentration of initial reagents, sonication power and molar ratio of pyridine as modulator has been optimized to synthesize nano powder of TMU-34(-2H) including uniform plate morphology. Nano TMU-34(-2H), can detect phenylhydrazine (PH) by color changing from pink to deep purple. As a comparison, nano and crystal samples of TMU-34(-2H) were treated to detect PH. Experiments show that nano TMU-34(-2H) has better detection limit and response time.     

腐植酸溶液的声化学降解研究

采用频率为1.8MHz的超声波在固定式声化学反应器内研究了声化学降解腐植酸的自由基氧化历程。通过采用TA溶液作为OH自由基捕获剂,吡啶溶液作HO2自由基捕获剂,以及KI溶液的I2释放法分别确定出实验条件下反应溶液中OH自由基的浓度为10^-7M,HO2自由基浓度为10^-5M及H2O2浓度为10^-5M。在此基础上研究了均相与多相催化条件下声化学降解腐植酸溶液的TOC削减情况。发现CeO2和Cu2O催化作用下腐植酸的降解效率分别较均相条件下提高40％和20％。并就反应机理和反应动力学过程进行了描述。     

超声技术在纳米材料制备中的应用

对超声技术在纳米材料制备中的应用与研究进展作了比较全面的综述,着重介绍了与超声有关的纳米材料制备方法,包括雪声雾化－热分解法,金属有机物超声热分解法,化学沉淀法和声电化学法,并就这些方法中声化作用的机理,特点和影响因素进行了讨论。     

A phenomenological investigation into the opposing effects of fluid flow on sonochemical activity at different frequency and power settings. 1. Overhead stirring

The effect of flow in an ultrasonic reactor is an important consideration for practical applications and for the scale-up of ultrasonic processing. Previous literature on the influence of flow on sonochemical activity has reported conflicting results. Therefore, this work examined the effect of overhead stirring at four different frequencies, 40, 376, 995 and 1179 kHz, in two different reactor configurations. Comparable power settings were utilised to elucidate the underlying mechanisms of interactions between the flow and sonochemical activity. The sonochemical activity was determined by the yield of hydrogen peroxide, measured by iodide dosimetry, and the active region was visualised with sonochemiluminescence imaging. The overhead stirring in the low frequency reactor altered the yield of hydrogen peroxide so it produced the maximum yield out of the four frequencies. The increase in hydrogen peroxide yield was attributed to a reduction in coalescence at 40 kHz. However at the higher frequencies, coalescence was not found to be the main reason behind the observed reductions in sonochemical yield. Rather the prevention of wave propagation and the reduction of the standing wave portion of the field were considered.     

Surfactant-free coating of thiols on gold nanoparticles using sonochemistry: A study of competing processes

A method for the surfactant-free coating of gold nanoparticles with thiols using sonochemistry is presented. The gold nanoparticles were prepared by a modified Zsigmondy method, affording good control over the particle-size distribution, and the thiol coating was performed by the sonication of a biphasic system consisting of a nanoparticle suspension in water and thiols in toluene. The effects of two important reaction parameters on the particle morphology, viz. sonication time and thiol concentration, were investigated in detail using transmission electron microscopy. The effect of the thiol chain length was also studied. We show that the morphology of the coated particles is determined through a competition between two opposing effects: particle fusion, due to the sonication conditions, and digestive ripening, due to the action of the thiols. Additionally, we illustrate the utility of our technique for various applications, including surface-enhanced Raman scattering from bound molecules, and further functionalization using a thiol-exchange reaction. Our technique paves the way for an efficient synthesis of thiol-coated AuNPs of different shapes and sizes, suitable for a range of diverse applications.     

Investigation of sonochemical activities at a frequency of 334 kHz: The effect of geometric parameters of sonoreactor

In this study, the effect of the dimensions of the bottom plate and liquid height was investigated for high-frequency sonoreactors under a vertically irradiated system. The dimensions of the bottom plate did not significantly influence sonochemical activity considering power density. However, as the bottom plate was increased in size, the hydroxyl radical generation rate decreased because of a decrease in power density. It is therefore recommended that sonoreactors with bottom-plate dimensions close to those of the ultrasonic transducer module be used. Liquid height had a significant effect on sonochemical activity, but the trend of the activity considering power density changed as the initial pollutant concentration changed. In the case of low initial concentration of As(III) (1 mg/L), the maximum cavitation yield for As(III) oxidation was observed at liquid heights of 150 mm.     

An efficient and selective way to new highly functionalized coronands or spiro derivatives using ultrasonic irradiation

A new, selective, straightforward and general method for preparation of highly functionalized coronands or spiro derivatives bearing 1,2-dihydroxyacetophenone unit, under conventional conditions and ultrasonic irradiation, is reported. The reaction setup involves only one step, acylation of an α-chloro-3,4-dihydroxyacetophenone with phthaloyl dichloride derivatives. 1,3- and 1,4-Phthaloyl dichloride derivatives leads to coronands only, while 1,2-phthaloyl dichlorides lead either to coronands or to spiro derivatives. A feasible explanation for the different behavior between conventional and ultrasound methods could be the different reaction mechanism involved in the two procedures: tetrahedral nucleophilic substitution under conventional conditions and radical substitution under ultrasound. Ultrasound induces a remarkable acceleration of the reactions (from days to minutes) and, most significantly, the yields are twice as high. A feasible explanation for the efficiency of the reactions under ultrasonic irradiation is presented.     

Physical features of ultrasound-enhanced heterogeneous permanganate oxidation

This paper addresses the matter of mechanistic features of ultrasound-assisted permanganate oxidation of organic compounds in aqueous phase. This reaction system is essentially a liquid–liquid heterogeneous one, which is limited by the mass transfer characteristics. Previous research has established that ultrasound irradiation of reaction mixture enhances the kinetics and yield of permanganate oxidation. The principal physical effect of ultrasonic cavitation is formation of fine emulsion between immiscible phases that eliminates the mass transfer resistance, while principal chemical effect is production of radicals through transient collapse of cavitation bubbles, which accelerate the reaction. In this paper, we have tried to discriminate between these physical and chemical effects by coupling experiments with different conditions (which alter the nature of cavitation phenomena in the medium) to simulations of cavitation bubble dynamics. It is revealed that in absence of radical conserving agent, the enhancement effect is merely physical. Diffusion of radicals towards interface between phases, where the oxidation reaction occurs is the limiting factor in contribution of chemical effect of ultrasonic cavitation towards enhancement of oxidation. Enhancement of total radical production in the aqueous phase (by degassing of the medium) increases the overall oxidation yield, but only marginally. On the other hand, addition of a radical conserver such as FeSO₄·7H₂O results in marked enhancement in oxidation yield, as the conserver assists deeper penetration of radicals in the aqueous medium and diffusion towards interface.