Oxygen-induced concurrent ultrasonic degradation of volatile and non-volatile aromatic compounds

Abstract

Acoustic cavitation, induced by ultrasound, can be used to eliminate organic pollutants from water. This type of ultrasonic treatment of polluted water can be grouped with those generally referred to as advanced oxidative processes since it involves hydroxyl radicals. In this case these highly active species are generated from the dissociation of water and oxygen dissociation caused by cavitation bubble collapse. The cavitation induced degradation rates of organic compounds in water are mainly linked to their vapor pressure and solubility and here we will further explore these links by examining the degradation of a mixture of two materials with different physical properties, chlorobenzene and 4-chlorophenol. The results obtained when a dilute solution of a mixture of these compounds saturated with argon is subjected to sonication at 300 kHz, parallels previous observations achieved in an aerated aqueous medium at 500 kHz. The two compounds exhibit sequential degradation with the more volatile chlorobenzene entering the cavitation bubble and being destroyed first. The 4-chlorophenol degradation occurs subsequently only when the chlorobenzene has been completely destroyed. The two compounds exhibit different behavior when sonicated in water saturated with oxygen. Under these conditions the two compounds are degraded simultaneously, a remarkable result for which two explanations can be proposed, both of which are based on the formation of additional OH radical species: The ability to produce conditions for the simultaneous elimination of two organic compounds by the use of oxygen is of great importance in the developing field of ultrasonic water treatment.

Sonochemical degradation of endocrine disrupting chemicals 17β-estradiol and 17α-ethinylestradiol in water and wastewater

“…These findings are consistent with those of Méndez-Arriaga et al (2008) which showed that the introduction of air promoted the formation of hydroxyl radical, thus contributing to the degradation of ibruprofen. Moreover, previous studies by Pétrier et al (2007), Torres et al (2008) and Chiha et al (2011) have also noted the importance of gas saturation on the sonochemical treatment of pollutants in water. In this experiment, the reaction medium became slightly acidic as the pH changed from 6 ± 0.3 to 4 ± 0.3, resulting to the generation of nitrate, nitrite and hydroxyl radicals as shown in Eqs.…”

“…Sonochemical degradation of organic pollutants in aqueous solutions is affected by air or gas bubbling (Pétrier et al 2007;Chiha et al 2011). To investigate the effects of this on the sonochemical degradation of E2 and EE2, continuous injection of air at equivalent flow rates was monitored during the sonication process.…”

“…This suggests that the sonochemical degradation of EDCs is a complex reaction that can be described by both kinetic models at different stages of the reaction. Various authors have reported both first-and second-order kinetics for similar organic compounds (Koda et al 2003;Pétrier et al 2007;Hameed et al 2007;Torres et al 2008).…”

Application of Novel Processing Methods for Greater Retention of Functional Compounds in Fruit-Based Beverages

“…Conversely, when US treatment was applied in a fruit smoothie at different amplitude levels (24.4-61 µm) and processing times (3-10 min), it was observed that the total phenolic content decreased with the increase of amplitude levels [68]. These degradation trends during US processing may be related to the formation of free radicals that occur during sonication, resulting in a potential development of different oxidation pathways [77]. When Carbonell-Capella et al [72] compared the effects of HIPEF and US processing on phenolic compounds of a mango-papaya blended beverage, they reported that the concentration of these compounds after HIPEF processing was significantly higher than those of untreated samples.…”

Study of the Effect of Thermoultrasound on the Antioxidant Compounds and Fatty Acid Profile from Blackberry (<em>Rubus fruticosus spp</em>) Juice

“…The slight decrease in pasteurized juice could be due to the oxidation reactions of ascorbic acid caused by the temperature below boiling point (72°C pasteurization). While the loss of ascorbic acid during sonication process might be by oxidative processes in aerobic and anaerobic environments associated with the production and use of hydroxyl radicals [16,17].…”