Ultrasonic irradiation was found to accelerate the rate of hydrolysis of omethoate in aqueous solution over the pH range of 2—12 Process parameters studied include pH, steady state temperature, concentration, and ...Ultrasonic irradiation was found to accelerate the rate of hydrolysis of omethoate in aqueous solution over the pH range of 2—12 Process parameters studied include pH, steady state temperature, concentration, and the type of gases. Greater than 96% hydrolysis was observed in 30 minutes through this process and the rate of destruction increased with the help of more soluble and low thermal inert gas. So with Krypton, omethoate was found to undergo rapid destruction as compared with Argon. In the presence of ultrasound, the observed first order rate of hydrolysis of omethoate is found to be independent of pH. The formation of transient supercritical water(SCW) appears to be an important factor in the acceleration of chemical reactions in the presence of ultrasound. A detailed chemical reaction mechanism for omethoate destruction in water was formulated. Experimental results and theoretical kinetic mechanism demonstrated that the most of the omethoate undergo destruction inside the cavitating holes. A very less effect of temperature on the degradation of omethoate within a temperature range of 20—70℃ proves that a small quantity of omethoate undergoes secondary destruction in the bulk liquid.展开更多
Synergetic effects for p-nitrophenol degradation were observed in the ozonation with ultrasonic enhancement. The enhancements of removal rate for p-nitrophenol and TOC were around 116% and 294% respectively in compari...Synergetic effects for p-nitrophenol degradation were observed in the ozonation with ultrasonic enhancement. The enhancements of removal rate for p-nitrophenol and TOC were around 116% and 294% respectively in comparison with the individual ultrasound and ozonation systems. The synergetic phenomenon is attributed to two physicochemical mechanisms: (1) Ultrasound decomposes ozone causing augmentation of the activity of free radicals; (2) Ultrasonic wave increased the concen- tration of O3 in solution because of ultrasonic dispersion.展开更多
Fe3O4 magnetic nanoparticles(MNPs) were synthesised, characterised, and used as a peroxidase mimetic to accelerate levofloxacin sono-degradation in an ultrasound(US)/H2O2 system. The Fe3O4 MNPs were in nanometre scale...Fe3O4 magnetic nanoparticles(MNPs) were synthesised, characterised, and used as a peroxidase mimetic to accelerate levofloxacin sono-degradation in an ultrasound(US)/H2O2 system. The Fe3O4 MNPs were in nanometre scale with an average diameter of approximately 12 to 18 nm. The introduction of Fe3O4 MNPs increased levofloxacin sono-degradation in the US/H2O2 system. Experimental parameters, such as Fe3O4 MNP dose, initial solution p H, and H2O2 concentration, were investigated by a one-factor-at-a-time approach. The results showed that Fe3O4 MNPs enhanced levofloxacin removal in the p H range from 4.0 to 9.0. Levofloxacin removal ratio increased with Fe3O4 MNP dose up to 1.0 g·L-1and with H2O2 concentration until reaching the maximum. Moreover, three main intermediate compounds were identified by HPLC with electrospray ionisation tandem mass spectrometry, and a possible degradation pathway was proposed. This study suggests that combination of H2O2, Fe3O4 MNPs and US is a good way to improve the degradation efficiency of antibiotics.展开更多
The sonolysis of azide solutions was investigated. The main product isnitrogen, which is formed in the reaction of N_3^- with OH radicals in the millimolar concentrationrange. At higher azide concentration, additional...The sonolysis of azide solutions was investigated. The main product isnitrogen, which is formed in the reaction of N_3^- with OH radicals in the millimolar concentrationrange. At higher azide concentration, additional nitrogen is formed as hydrogen atoms are scavenged.Ammonia and hydrazine are minor products of the N_3^- sonolysis. Solutions of iodide and bromideare also irradiated under pH conditions where reactions of the products, i.e., hydrogen per oxideand iodide (or bromide) do not occur. The total yield of the products as well as the hydrogen yieldis independent of the solute concentration. The results are understood in terms of the competitionof the OH + OH and the OH + solute reactions. A local concentration of 4 X 10^(-3) mol/L of the OHradicals in an interfacial region between the cavitation bubbles and the liquid is derived from thedata obtained.展开更多
The physicochemical degradation of Indigo Carmine (IC) dye in aqueous solution was performed using single and combined Advanced Oxidation Processes (AOP’s). Photocatalysis (TiO<sub>2</sub>-UV), Ozonation ...The physicochemical degradation of Indigo Carmine (IC) dye in aqueous solution was performed using single and combined Advanced Oxidation Processes (AOP’s). Photocatalysis (TiO<sub>2</sub>-UV), Ozonation (O<sub>3</sub>) and Sonolysis (SN) were tested either in a standalone methodology or by combination of two simultaneous AOP’s. The dye conversion was followed by both measurements: 1) color removal determined by UV-VIS spectrometry and 2) organic and inorganic load determined by the chemical oxygen demand (COD). A complete and quick color disappearance of model water waste has been obtained by using combination of non-irradiated AOP’s, namely, O3</sub>/SN, which contrasts to the combination of irradiated photocatalysis with O3</sub> or sonolysis. Color removal with simultaneous TiO2</sub>-UV/SN reached 77% while TiO2</sub>-UV/O3</sub> reached 96% at similar reaction time. On the other hand, the standalone O3</sub> yielded the highest color removal (94.4%) in 32 minutes whereas SN reached only 39.2% in 4 hours. The standalone light irradiated TiO2</sub>-UV reached 93.3% color re-moval in one hour of reaction time. These results indicated that non-irradiated (SN and O3</sub>) enhance synergistic effects that provoke structural changes in dye molecule without reaching total degradation. This is evidenced from FTIR of residuals from reaction mixture in which it has been observed the presence of organic molecules such as aromatics, sulfonic and amines refractory compounds that are mechanisti-cally possible to be found during IC degradation. Also, toxicity tests (MicroTox<sup>?</sup> Technique) were performed using commercially available bacteria culture before and after IC degradation for each AOP and their combination. Reduction of aqueous dye concentration decreased the level of toxicity of the treated water which is the main target of the AOP’s but the presence of the remaining recalcitrant compounds have also toxic effect.展开更多
In contrast to the well-known methods for the generation of radical cations, such as radiolysis, electrolysis and single electron transfer reactions, the formation of radical cations by ultrasound is little known. It ...In contrast to the well-known methods for the generation of radical cations, such as radiolysis, electrolysis and single electron transfer reactions, the formation of radical cations by ultrasound is little known. It has been demonstrated that free radicals produced by sonolysis of carbon tetrachloride can be trapped by 2-methyl-2-nitrosopropane and identified by ESR. Recently, unambiguous evidence for the formation of hydroxyl radicals and hydrogen atoms during sonolysis of water by using DMPO(5,5-dimethyl-1-pyrroline-1-oxide)展开更多
文摘Ultrasonic irradiation was found to accelerate the rate of hydrolysis of omethoate in aqueous solution over the pH range of 2—12 Process parameters studied include pH, steady state temperature, concentration, and the type of gases. Greater than 96% hydrolysis was observed in 30 minutes through this process and the rate of destruction increased with the help of more soluble and low thermal inert gas. So with Krypton, omethoate was found to undergo rapid destruction as compared with Argon. In the presence of ultrasound, the observed first order rate of hydrolysis of omethoate is found to be independent of pH. The formation of transient supercritical water(SCW) appears to be an important factor in the acceleration of chemical reactions in the presence of ultrasound. A detailed chemical reaction mechanism for omethoate destruction in water was formulated. Experimental results and theoretical kinetic mechanism demonstrated that the most of the omethoate undergo destruction inside the cavitating holes. A very less effect of temperature on the degradation of omethoate within a temperature range of 20—70℃ proves that a small quantity of omethoate undergoes secondary destruction in the bulk liquid.
文摘Synergetic effects for p-nitrophenol degradation were observed in the ozonation with ultrasonic enhancement. The enhancements of removal rate for p-nitrophenol and TOC were around 116% and 294% respectively in comparison with the individual ultrasound and ozonation systems. The synergetic phenomenon is attributed to two physicochemical mechanisms: (1) Ultrasound decomposes ozone causing augmentation of the activity of free radicals; (2) Ultrasonic wave increased the concen- tration of O3 in solution because of ultrasonic dispersion.
基金Supported by the National Natural Science Foundation of China(51009115)Shaanxi Provincial Department of Education Key Laboratory Project(13JS067)+2 种基金the Hall of Shaanxi Province Science and Technology(2013JK0881)the Research Plan Project of Water Resources Department of Shaanxi Province(2013slkj-07)the Innovation of Science and Technology Fund of Xi'an University of Technology(211302)
文摘Fe3O4 magnetic nanoparticles(MNPs) were synthesised, characterised, and used as a peroxidase mimetic to accelerate levofloxacin sono-degradation in an ultrasound(US)/H2O2 system. The Fe3O4 MNPs were in nanometre scale with an average diameter of approximately 12 to 18 nm. The introduction of Fe3O4 MNPs increased levofloxacin sono-degradation in the US/H2O2 system. Experimental parameters, such as Fe3O4 MNP dose, initial solution p H, and H2O2 concentration, were investigated by a one-factor-at-a-time approach. The results showed that Fe3O4 MNPs enhanced levofloxacin removal in the p H range from 4.0 to 9.0. Levofloxacin removal ratio increased with Fe3O4 MNP dose up to 1.0 g·L-1and with H2O2 concentration until reaching the maximum. Moreover, three main intermediate compounds were identified by HPLC with electrospray ionisation tandem mass spectrometry, and a possible degradation pathway was proposed. This study suggests that combination of H2O2, Fe3O4 MNPs and US is a good way to improve the degradation efficiency of antibiotics.
文摘The sonolysis of azide solutions was investigated. The main product isnitrogen, which is formed in the reaction of N_3^- with OH radicals in the millimolar concentrationrange. At higher azide concentration, additional nitrogen is formed as hydrogen atoms are scavenged.Ammonia and hydrazine are minor products of the N_3^- sonolysis. Solutions of iodide and bromideare also irradiated under pH conditions where reactions of the products, i.e., hydrogen per oxideand iodide (or bromide) do not occur. The total yield of the products as well as the hydrogen yieldis independent of the solute concentration. The results are understood in terms of the competitionof the OH + OH and the OH + solute reactions. A local concentration of 4 X 10^(-3) mol/L of the OHradicals in an interfacial region between the cavitation bubbles and the liquid is derived from thedata obtained.
文摘The physicochemical degradation of Indigo Carmine (IC) dye in aqueous solution was performed using single and combined Advanced Oxidation Processes (AOP’s). Photocatalysis (TiO<sub>2</sub>-UV), Ozonation (O<sub>3</sub>) and Sonolysis (SN) were tested either in a standalone methodology or by combination of two simultaneous AOP’s. The dye conversion was followed by both measurements: 1) color removal determined by UV-VIS spectrometry and 2) organic and inorganic load determined by the chemical oxygen demand (COD). A complete and quick color disappearance of model water waste has been obtained by using combination of non-irradiated AOP’s, namely, O3</sub>/SN, which contrasts to the combination of irradiated photocatalysis with O3</sub> or sonolysis. Color removal with simultaneous TiO2</sub>-UV/SN reached 77% while TiO2</sub>-UV/O3</sub> reached 96% at similar reaction time. On the other hand, the standalone O3</sub> yielded the highest color removal (94.4%) in 32 minutes whereas SN reached only 39.2% in 4 hours. The standalone light irradiated TiO2</sub>-UV reached 93.3% color re-moval in one hour of reaction time. These results indicated that non-irradiated (SN and O3</sub>) enhance synergistic effects that provoke structural changes in dye molecule without reaching total degradation. This is evidenced from FTIR of residuals from reaction mixture in which it has been observed the presence of organic molecules such as aromatics, sulfonic and amines refractory compounds that are mechanisti-cally possible to be found during IC degradation. Also, toxicity tests (MicroTox<sup>?</sup> Technique) were performed using commercially available bacteria culture before and after IC degradation for each AOP and their combination. Reduction of aqueous dye concentration decreased the level of toxicity of the treated water which is the main target of the AOP’s but the presence of the remaining recalcitrant compounds have also toxic effect.
文摘In contrast to the well-known methods for the generation of radical cations, such as radiolysis, electrolysis and single electron transfer reactions, the formation of radical cations by ultrasound is little known. It has been demonstrated that free radicals produced by sonolysis of carbon tetrachloride can be trapped by 2-methyl-2-nitrosopropane and identified by ESR. Recently, unambiguous evidence for the formation of hydroxyl radicals and hydrogen atoms during sonolysis of water by using DMPO(5,5-dimethyl-1-pyrroline-1-oxide)
