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In this study, we attempt for the first time to couple sonication and photo-Fenton for bacterial inactivation of secondary treated effluent. Synthetic wastewater was subjected to sequential high-frequency/low power sonication, followed by mild photo-Fenton treatment, under a solar simulator. It was followed by the assessment of the contribution of each component of the process (Fenton, US, hv) towards the removal rate and the long-term survival; sunlight greatly improved the treatment efficiency, with the coupled process being the only one to yield total inactivation within the 4-h period of treatment. The short-term beneficial disinfecting action of US and its detrimental effect on bacterial survival in long term, as well as the impact of light addition were also revealed. Finally, an investigation on the operational parameters of the process was performed, to investigate possible improvement and/or limitations of the coupled treatment; 3 levels of each parameter involved (hydraulic, environmental, US and Fenton) were tested. Only H2O2 increased improved the process significantly, but the action mode of the joint process indicated potential cost-effective solutions towards the implementation of this method., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Sonochemical degradation of phenol (Ph), 4-isopropylphenol (4-IPP) and Rhodamine B (RhB) in aqueous solutions was investigated for a large range of initial concentrations in order to analyze the reaction kinetics. The initial rates of substrate degradation and H(2)O(2) formation as a function of initial concentrations were determined. The obtained results show that the degradation rate increases with increasing initial substrate concentration up to a plateau and that the sonolytic destruction occurs mainly through reactions with hydroxyl radicals in the interfacial region of cavitation bubbles. The rate of H(2)O(2) formation decreases with increasing substrate concentration and reaches a minimum, followed by almost constant production rate for higher substrate concentrations. Sonolytic degradation data were analyzed by the models of Okitsu et al. [K. Okitsu, K. Iwasaki, Y. Yobiko, H. Bandow, R. Nishimura, Y. Maeda, Sonochemical degradation of azo dyes in aqueous solution: a new heterogeneous kinetics model taking into account the local concentration OH radicals and azo dyes, Ultrason. Sonochem. 12 (2005) 255-262.] and Seprone et al. [N. Serpone, R. Terzian, H. Hidaka, E. Pelizzetti, Ultrasonic induced dehalogenation and oxidation of 2-, 3-, and 4-chlorophenol in air-equilibrated aqueous media. Similarities with irradiated semiconductor particulates, J. Phys. Chem. 98 (1994) 2634-2640.] developed on the basis of a Langmuir-type mechanism. The five linearized forms of the Okitsu et al.'s equation as well as the non-linear curve fitting analysis method were discussed. Results show that it is not appropriate to use the coefficient of determination of the linear regression method for comparing the best-fitting. Among the five linear expressions of the Okitsu et al.'s kinetic model, form-2 expression very well represent the degradation data for Ph and 4-IPP. Non-linear curve fitting analysis method was found to be the more appropriate method to determine the model parameters. An excellent representation of the experimental results of sonolytic destruction of RhB was obtained using the Serpone et al.'s model. The Serpone et al.'s model gives a worse fit for the sonolytic degradation data of Ph and 4-IPP. These results indicate that Ph and 4-IPP undergo degradation predominantly at the bubble/solution interface, whereas RhB undergoes degradation at both bubble/solution interface and in the bulk solution., ((c) 2010 Elsevier B.V. All rights reserved.)

Sonolysis, enzyme treatment, and a combination of the two processes were tested for the degradation of phenol in aqueous medium. With sonolysis alone, 423 kHz ultrasound eliminated phenol molecules through hydroxyl radical reactions. In the presence of hydrogen peroxide, the enzyme horseradish peroxidase (HRP) catalyzed the oxidation of phenol to insoluble polymers which could be separated easily from the solution. In the combined system (HRP, H2O2, US-423 kHz) the degradation rate was accelerated, and the color of the solution changed to dark brown without any precipitate formation. The enhancement was more significant in the presence of additives such as polyethylene glycol (PEG). The higher rate induced through the use of ultrasound leads to the reduction of HRP dose requirements, which is of importance for the economic feasibility of this method. The enzyme solution alone did not show any inactivation up to 45 min sonication at 423 kHz. Investigation of phenol removal efficiency was mainly focused on enzyme, phenol and PEG concentrations, as well as the sequence and method of addition of reagents. [Copyright &y& Elsevier]

• Ultrasonic frequency and power effects on peroxynitrite formation by sonolysis were examined. • Energy required for ultrasound-induced peroxynitrite formation increases with frequency. • Peroxynitrite formation decreases with frequency and increases with power. • High dependence of peroxynitrite production by sonolysis on ultrasonic power. • Peroxynitrite produced by sonolysis can be used as a dosimeter in sonochemistry. There is a lack of literature on peroxynitrite formation due to sonolysis of aerated water. In this work, the impact of sonication parameters, frequency and power, on ultrasonic peroxynitrite production in aerated alkaline water was investigated. Peroxynitrite formation was clearly established with undeniable evidence at all the tested frequencies in the range of 516–1140 kHz with a typical G-value (energy-specific yield) of 0.777 × 10−10, 0.627 × 10−10, 0.425 × 10−10 and 0.194 × 10−10 mol/J at 516, 558, 860 and 1140 kHz, respectively. The ultrasonication frequency has a direct impact on the sonochemical peroxynitrite production. Increasing the ultrasonication frequency in the interval 321–1140 kHz reduces peroxynitrite formation. The most practical sonochemistry dosimetries, including hydrogen peroxide production, triiodide dosimetry, Fricke dosimetry, and 4-nitrocatechol formation, were compared with the sonochemical efficiency of the reactors used to produce peroxynitrite. The G-value, energy specific yield, for the tested dosimetries was higher than that for peroxynitrite formation, regardless of frequency. For all chemical dosimetries investigated, the same trend of frequency dependence was found as for peroxynitrite generation. The influence of ultrasonication power on peroxynitrite formation by sonication at diverse frequencies in the interval 585–1140 kHz was studied. No peroxynitrite was formed at lower acoustic power levels, regardless of frequency. As the frequency increases, more power is required for peroxynitrite formation. The production of peroxynitrite increased as the acoustic power increased, despite the frequency of ultrasonic waves. Ultrasonic power is a key factor in the production of peroxynitrite by sonolysis. Since peroxynitrite is uniformly distributed in the bulk solution, peroxynitrite-sensitive solutes can be transformed both in the bulk of the solution and in the surfacial region (shell) of the cavitation bubble. The formation of peroxynitrite should be taken into account in sonochemistry, especially at higher pH values. Ultrasonic peroxynitrite formation in alkaline solution (pH 12) can be considered as a kind of chemical dosimetry in sonochemistry. [ABSTRACT FROM AUTHOR]

Abstract: In this study, removal of malachite green (MG), a cationic triphenylmethane dye, by 300kHz ultrasound was investigated. The effects of operating parameters such as initial dye concentration, ultrasound power and initial pH on the sonochemical degradation were studied. The initial rate of MG degradation and hydrogen peroxide formation as a function of initial concentration were determined. The obtained results show that the degradation rate increases with increasing initial dye concentration up to a plateau. The rate of hydrogen peroxide formation decreases with increasing substrate concentration and reaches a minimum, followed by almost constant production rate for higher MG concentrations. The dominant degradation mechanism is the reaction of substrate with ls both at the gas bubble–liquid interface and in the bulk solution. Sonochemical degradation of MG occurs via two competitive processes: N-demethylation and destruction of the conjugated structure. The degradation rate increased proportionally with increasing ultrasonic power, but decreased with the increase of initial pH value from 2 to 7. In the presence of 10mg/L Fe(II), the initial degradation rate of MG became 2 times larger for initial dye concentration of 5mg/L and 1.5 times larger for initial substrate concentration of 10mg/L, respectively. [Copyright &y& Elsevier]

Abstract: The Molybdate-catalyzed bromination of various aromatic compounds in the presence of KBr/H2O2 in an aqueous/chloroform biphasic system occurred under ultrasonic irradiation, whereas the reaction did not take place under conventional mechanical stirring (1400rpm). The sonochemical activation was found to be of secondary effect, attributed to lowering pH by sonolysis of CHCl3–H2O solvents mixture. [Copyright &y& Elsevier]

Abstract: This paper explores the degradation of a model pollutant, bisphenol A, by an advanced oxidation process that combines sonolysis, Fe2+, and TiO2 in a photoassisted process. Experiments were done under saturated oxygen conditions. The effect of different Fe2+ (0.56 and 5.6 mg/L) and TiO2 (10 and 50 mg/L) concentrations was investigated on both the elimination and mineralization of the pollutant. A pronounced synergistic effect that led to the complete and rapid elimination of dissolved organic carbon (DOC) was observed even at low catalyst loadings. In this system, almost a complete removal of DOC (93%) was observed after 4 h using 10 and 5.6 mg/L of TiO2 and Fe2+, respectively, whereas at the same time, only 5, 6, and 22% of DOC was removed by an individual process alone (TiO2 photocatalysis, ultrasound, and photo-Fenton, respectively). In this system, ultrasound has the principal role of eliminating the initial substrate and providing hydrogen peroxide for the photocatalytic systems, while photo-Fenton and TiO2 photocatalysis are mainly responsible for the transformation of the intermediates in CO2 and H2O. The role of H2O2 generated from the sonochemical process is also discussed. [Copyright &y& Elsevier]