Enhancement effects of ultrasound on secondary wastewater effluent disinfection by sodium hypochlorite and disinfection by-products analysis

Since fecal coliforms was introduced as a standard indicator of pollutants in effluents of municipal wastewater treatment plants in China in 2003, chlorine had been widely used in many wastewater treatment plants. However, concerns about the disinfection by-products (DBPs) of chlorine have been increasing. One of the effective way to reduce the production of DBPs is to reduce the effective chlorine dosage by improving the utilization rate of disinfectant. Ultrasound (US) is proved to be effective in wastewater treatment for its multiple chemical and physical effects produced by cavitation, which could favor the disinfection process accordingly. For the purpose of improving disinfection efficiency with the help of US, following points are addressed in the current study: (1) investigate the enhancement effects of US on the disinfection efficiency of sodium hypochlorite (NaClO) for real secondary effluents of municipal wastewater treatment plants; (2) evaluate the possibility of using US specific energy consumption (kJ/L) as an parameter for disinfection efficiency evaluation; and (3) quantify the reduction in chlorine-DBPs through US application. Results demonstrated that sonication could reduce two-thirds (US pretreatment) or one-third (simultaneous US and NaClO disinfection) of the required concentrations of NaClO (available chlorine) for 4 log reduction of fecal coliforms, which could meet the Class 1A (fecal coliforms less than 1000 CFU/L) discharge standard of China. In addition, US pretreatment with NaClO disinfection performed better enhancement in disinfection efficiency compared with simultaneous US and NaClO disinfection. Furthermore, analysis on DBPs showed that US application as pretreatment could obviously reduce the contents of trichloromethane (TCM) and trichloroacetic acid (TCAA) by more than 85% and 50%, respectively, compared with NaClO disinfection alone for the same disinfection efficiency. Meanwhile, the experimental results also showed that the disinfection efficiency and DBPs concentration were only slightly affected under a constant US specific energy consumption, although input power density and irradiation time changed, indicating that specific energy consumption (kJ/L) could be considered as a better control parameter for disinfection efficiency evaluation.     

Synergistic effect of ultrasonic pre-treatment combined with UV irradiation for secondary effluent disinfection

The ultraviolet (UV) disinfection efficiency is often affected by suspended solids (SS). Given their high concentration or large particle size, SS can scatter UV light and provide shielding for bacteria. Thus, ultrasound is often employed as a pre-treatment process to improve UV disinfection. This work investigated the synergistic effect of ultrasound combined with UV for secondary effluent disinfection. Bench-scale experiments were conducted in using samples obtained from secondary sedimentation tanks. These tanks belonged to three wastewater treatment plants in Beijing that use different kinds of biological treatment methods. Several parameters may contribute to the changes in the efficiency of ultrasound and UV disinfection. Thus, the frequency and energy density of ultrasound, as well as the SS, were investigated. Results demonstrated that samples which have relatively higher SS concentrations or higher percentages of larger particles have less disinfection efficiency using UV disinfection alone. However, the presence of ultrasound could improve the disinfection efficiency because it has synergistic effect. Changes in the particle size distribution and SS concentration notably affected the efficiency of UV disinfection. The efficiency of Escherichia coli elimination can be decreased by 1.2 log units as the SS concentration increases from 16.9 mg/l to 25.4 mg/l at a UV energy density of 40 mJ/cm². UV disinfection alone reduced the E. coli population by 3.4 log units. However, the synergistic disinfection of ultrasound and UV could reach 5.4 log units during the reduction of E. coli at a 40 kHz frequency and an energy density of 2.64 kJ/l. The additional synergistic effect is 1.1 log units.     

Effects of ultrasound pretreatment with different frequencies and working modes on the enzymolysis and the structure characterization of rice protein

The effects of ultrasound pretreatment with different frequencies and working modes, including mono-frequency ultrasound (MFU), dual-frequency ultrasound (DFU) and tri-frequency ultrasound (TFU), on the degree of hydrolysis (DH) of rice protein (RP) and angiotensin-I-converting enzyme (ACE) inhibitory activity of RP hydrolysate were investigated. Ultraviolet–visible (UV) spectroscopy, fourier transform infrared (FTIR) spectroscopy, surface hydrophobicity and scanning electron microscopy (SEM) of RP pretreated with ultrasound were measured. The results showed that ultrasound pretreatment did not increase DH of RP significantly (p > 0.05). However, all the ultrasound pretreatment increased the ACE inhibitory activity of RP hydrolysate significantly (p < 0.05). The MFU of 20 kHz showed higher ACE inhibitory activity compared to that of other MFU. The ACE inhibitory activity of sequential DFU was higher than that of simultaneous with the same frequency combination. Sequential TFU of 20/35/50 kHz produced the highest increase in ACE inhibitory activity in contrast with other ultrasound frequencies and working modes. All the results under ultrasound pretreatment showed that ultrasound frequencies and working modes were of great effect on the ACE inhibitory activity of RP. The changes in UV–Vis spectra and surface hydrophobicity indicated the unfolding of protein and exposure of hydrophobic groups by ultrasound. The FTIR analysis showed that all the ultrasound pretreatment with different frequencies and working modes decreased α-helix, β-turn content and increased β-sheet, random coil content of RP. The SEM results indicated that ultrasound pretreatment resulted in the deformation of RP. In conclusion, the frequency selection of ultrasound pretreatment of RP is essential for the preparation of ACE inhibitory peptide.     

Dual frequency cavitation event sensor with iodide dosimeter

The inertial cavitation activity depends on the sonication parameters. The purpose of this work is development of dual frequency inertial cavitation meter for therapeutic applications of ultrasound waves. In this study, the chemical effects of sonication parameters in dual frequency sonication (40 kHz and 1 MHz) were investigated in the progressive wave mode using iodide dosimetry. For this purpose, efficacy of different exposure parameters such as intensity, sonication duration, sonication mode, duty factor and net ultrasound energy on the inertial cavitation activity have been studied. To quantify cavitational effects, the KI dosimeter solution was sonicated and its absorbance at a wavelength of 350 nm was measured. The absorbance values in continuous sonication mode was significantly higher than the absorbance corresponding to the pulsed mode having duty factors of 20–80% (p < 0.05). Among different combination modes (1 MHz_100% + 40 kHz_100%, 1 MHz_100% + 40 kHz_80%, 1 MHz_80% + 40 kHz_100%, 1 MHz_80% + 40 kHz_80%), the continuous mode for dual frequency sonication is more effective than other combinations (p < 0.05). The absorbance for this combined dual frequency mode was about 1.8 times higher than that obtained from the algebraic summation of single frequency sonications. It is believed that the optimization of dual frequency sonication parameters at low-level intensity (<3 W/cm²) by optically assisted cavitation event sensor can be useful for ultrasonic treatments.     

Influence of ultrasound enhancement on chlorine dioxide consumption and disinfection by-products formation for secondary effluents disinfection

Chlorine dioxide (ClO₂) has been promoted as an alternative disinfectant because of its high disinfection efficiency and less formation of organic disinfection by-products (DBPs). However, particle-associated microorganisms could be protected during the disinfection process, which decreases the disinfection efficiency or increases the required dosage. Besides, the formation of inorganic disinfection by-products is a significant concern in environment health. Ultrasound (US)-combined disinfection methods are becoming increasingly attractive because they are efficient and environmentally friendly. In this study, US was introduced as an enhancement method to identify its influence on ClO₂ demand reduction and to minimize the production of potential DBPs for secondary effluents disinfection. Fecal coliform was used as an indicator, and DBPs, including trichloromethane (TCM), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), chlorite (ClO₂⁻), and chlorate (ClO₃⁻), were analyzed to observe the potential DBPs formation. Results show that US pretreatment could reduce half of ClO₂ dosage compared with ClO₂ disinfection alone for the same disinfection efficiency, and that an input power density of 2.64 kJ/L pretreatment with the 1.5 mg/L ClO₂ was enough to meet the discharge requirement in China (i.e., fecal coliform below 1000 CFU/L for Class 1A) for secondary effluent disinfection, and the ClO₂⁻ concentration in the disinfection effluent was only 1.37 mg/L at the same time. Furthermore, the different effects of US on the two processes (US as pretreatment and simultaneous US/ClO₂ disinfection) were also analyzed, including deagglomerating, cell damage, and synergistic disinfection as well as degasing/sonolysis. It was proved that the production of TCM, DCAA, and TCAA was insignificantly influenced with the introduction of US, but US pretreatment did reduce the production of ClO₂⁻ and ClO₃⁻ effectually. In general, US pretreatment could be a better option for disinfection enhancement methods combined with ClO₂ in terms of both disinfection efficiency and disinfection by-product formation.     

Synthesis of sub-micronic and nanometric PMMA particles via emulsion polymerization assisted by ultrasound: Process flow sheet and characterization

PMMA particle synthesis was performed from MMA (methyl methacrylate) and water mixtures, exposed to different ultrasonic systems and frequencies. The sonication sequence was 20 kHz → 580 kHz → 858 kHz → 1138 kHz, and the solution was sampled after each irradiation step for polymerization. Effects of sonication parameters (time, power), polymerization method (thermo-initiated or photo-initiated), use of small amounts of surfactant (Triton X-100™ or Tween® 20) and initial MMA quantity were investigated on particle size and synthesis yields. Particle size and size distribution were measured by DLS (Dynamic Light Scattering), and confirmed via SEM (Scanning Electron Microscopy) images. Synthesis yield was calculated using the dry weight method. Particle composition was estimated using FTIR (Fourier Transform Infra-Red) spectroscopy. PMMA (polymethylmethacrylate) monodispersed particles were successfully synthesized, with a possibility of control in the 78–310 nm size range. These sized-controlled particles were synthesized with a 7.5–85% synthesis yield (corresponding to 7.5–40 g/L particle solid content), depending on operational parameters. Furthermore, a trade-off between particle size and synthesis yield can be proposed: 20 kHz → 10 min waiting time → 580 kHz → 858 kHz leading to 90 nm particles diameter with 72% yield in less than 40 min for the whole sequence. Thus, the synthesis under ultrasound can be found easy to implement and time efficient, ensuring the success of the scale-up approach and opening up industrial applications for this type of polymeric particles.     

Sonocatalytic removal of ibuprofen and sulfamethoxazole in the presence of different fly ash sources

We examined the feasibility of using two types of fly ash (an industrial waste from thermal power plants) as a low-cost catalyst to enhance the ultrasonic (US) degradation of ibuprofen (IBP) and sulfamethoxazole (SMX). Two fly ashes, Belews Creek fly ash (BFA), from a power station in North Carolina, and Wateree Station fly ash (WFA), from a power station in South Carolina, were used. The results showed that >99% removal of IBP and SMX was achieved within 30 and 60 min of sonication, respectively, at 580 kHz and pH 3.5. Furthermore, the removal of IBP and SMX achieved, in terms of frequency, was in the order 580 kHz > 1000 kHz > 28 kHz, and in terms of pH, was in the order of pH 3.5 > pH 7 > pH 9.5. WFA showed significant enhancement in the removal of IBP and SMX, which reached >99% removal within 20 and 50 min, respectively, at 580 kHz and pH 3.5. This was presumably because WFA contains more silicon dioxide than BFA, which can enhance the formation of OH radicals during sonication. Additionally, WFA has finer particles than BFA, which can increase the adsorption capacity in removing IBP and SMX. The sonocatalytic degradation of IBP and SMX fitted pseudo first-order rate kinetics and the synergistic indices of all the reactions were determined to compare the efficiency of the fly ashes. Overall, the findings have showed that WFA combined with US has potential for treating organic pollutants, such as IBP and SMX, in water and wastewater.     

Impact of ultrasound treatment on lipid oxidation of Cheddar cheese whey

Ultrasound (US) has been suggested for many whey processing applications. This study examined the effects of ultrasound treatment on the oxidation of lipids in Cheddar cheese whey. Freshly pasteurized whey (0.86 L) was ultrasonicated in a contained environment at the same range of frequencies and energies for 10 and 30 min at 37 °C. The US reactor used was characterized by measuring the generation of free radicals in deionized water at different frequencies (20–2000 kHz) and specific energies (8.0–390 kJ/kg). Polar lipid (PL), free and bound fatty acids and lipid oxidation derived compounds were identified and quantified before and after US processing using high performance liquid chromatography equipped with an evaporative light scattering detector (HPLC–ELSD), methylation followed by gas chromatography flame ionized detector (GC-FID) and solid phase micro-extraction gas chromatography mass spectrometry (SPME-GCMS), respectively. The highest concentration of hydroxyl radical formation in the sonicated whey was found between 400 and 1000 kHz. There were no changes in phospholipid composition after US processing at 20, 400, 1000 and 2000 kHz compared to non-sonicated samples. Lipid oxidation volatile compounds were detected in both non-sonicated and sonicated whey. Lipid oxidation was not promoted at any tested frequency or specific energy. Free fatty acid concentration was not affected by US treatment per se. Results revealed that US can be utilized in whey processing applications with no negative impact on whey lipid chemistry.     

Ultrasound stimulated release of mimosa medicine from cellulose hydrogel matrix

Ultrasound (US) drug release system using cellulose based hydrogel films was developed as triggered to mimosa. Here, the mimosa, a fascinating drug to cure injured skin, was employed as the loading drug in cellulose hydrogel films prepared with phase inversion method. The mimosa hydrogels were fabricated from dimethylacetamide (DMAc)/LiCl solution in the presence of mimosa, when the solution was exposed to ethanol vapor. The US triggered release of the mimosa from the hydrogel matrix was carried out under following conditions of US powers (0–30 W) and frequencies (23, 43 and 96 kHz) for different mimosa hydrogel matrix from 0.5 wt% to 2 wt% cellulose solution. To release the drug by US trigger from the matrix, the better medicine release was observed in the matrix prepared from the 0.5 wt% cellulose solution when the 43 kHz US was exposed to the aqueous solution with the hydrogel matrix. The release efficiency increased with the increase of the US power from 5 to 30 W at 43 kHz. Viscoelasticity of the hydrogel matrix showed that the hydrogel became somewhat rigid after the US exposure. FT-IR analysis of the mimosa hydrogel matrixes showed that during the US exposure, hydrogen bonds in the structure of mimosa–water and mimosa–cellulose were broken. This suggested that the enhancement of the mimosa release was caused by the US exposure.     

Single,simultaneous and sequential applications of ultrasonic frequencies for the elimination of ibuprofen in water

The study is about the assessment of single and multi-frequency operations for the overall degradation of a widely consumed analgesic pharmaceutical-ibuprofen (IBP). The selected frequencies were in the range of 20–1130 kHz emissions coming from probes, baths and piezo-electric transducers attached to plate-type devices. Multi-frequency operations were applied either simultaneously as “duals”, or sequentially at fixed time intervals; and the total reaction time in all operations was 30-min. The work also covers evaluation of the effect of zero-valent iron (ZVI) on the efficiency of the degradation process and the performance of the reaction systems. It was found that low-frequency probe type devices especially at 20 kHz were ineffective when applied singly and without ZVI, and relatively more effective in combined-frequency operations in the presence of ZVI. The power efficiencies of the reactors and/or reaction systems showed that 20-kHz probe was considerably more energy intensive than all others, and was therefore not used in multi-frequency operations. The most efficient reactor in terms of power consumption was the bath (200 kHz), which however provided insufficient mineralization of the test chemical. The highest percentage of TOC decay (37%) was obtained in a dual-frequency operation (40/572 kHz) with ZVI, in which the energy consumption was neither low nor exceptionally too high. A sequential operation (40 + 200 kHz) in that respect was more efficient, because it required much less energy for a similar TOC decay performance (30%). In general, the degradation of IBP increased with increased power consumption, which in turn reduced the sonochemical yield. The study also showed that advanced Fenton reactions with ZVI were faster in the presence of ultrasound, and the metal was very effective in improving the performance of low-frequency operations.     

Aggregation kinetics of single walled carbon nanotubes influenced by the frequency of ultrasound irradiation in the aquatic environment

The colloidal stability of single-walled carbon nanotubes (SWNTs) sonicated at three different ultrasonication (US) frequencies (28, 580, and 1000 kHz) were investigated under environmentally relevant conditions. In particular, correlations between surface chemistry, electrokinetic potential, interaction energy, and the aggregation kinetics of the aqueous SWNTs were studied. We observed that H₂O₂ production is negatively correlated with the yield of hydroxylation and carboxylation of SWNTs, which was dependent on the generation of ultrasonic energy by cavity collapse during US process. The SWNTs sonicated at relatively high US frequencies (580 and 1000 kHz) aggregated rapidly in synthetic surface water, whereas alkalinity affected the stability of SWNTs insignificantly. This was because the SWNTs became less negatively charged under such conditions and were captured in deep primary energy wells, according to the Derjaguin-Landau-Verwey-Overbeek theory. Critical coagulation concentration values for the ultrasonicated SWNTs were determined to be 102 mM NaCl for 28 kHz, 22 mM NaCl for 580 kHz, and 43 mM NaCl for 1000 kHz. Suwannee River humic acid decreased the aggregation rate of SWNTs due to the steric hindrance, because of adsorbed macromolecules. Our findings show that the aggregate stability of SWNTs is controlled largely by a complex interplay between the evolution of surface functional groups on the SWNTs during US and solution chemistry.     

Synergism between ultrasonic pretreatment and white rot fungal enzymes on biodegradation of wheat chaff

Lignocellulosic biomass samples (wheat chaff) were pretreated by ultrasound (US) (40 kHz/0.5 W cm⁻²/10 min and 400 kHz/0.5 W cm⁻²/10 min applied sequentially) prior to digestion by enzyme extracts obtained from fermentation of the biomass with white rot fungi (Phanerochaete chrysosporium or Trametes sp.). The accessibility of the cellulosic components in wheat chaff was increased, as demonstrated by the increased concentration of sugars produced by exposure to the ultrasound treatment prior to enzyme addition. Pretreatment with ultrasound increased the concentration of lignin degradation products (guaiacol and syringol) obtained from wheat chaff after enzyme addition. In vitro digestibility of wheat chaff was also enhanced by the ultrasonics pretreatment in combination with treatment with enzyme extracts. Degradation was enhanced with the use of a mixture of the enzyme extracts compared to that for a single enzyme extract.     

Conductive diamond sono-electrochemical disinfection (CDSED) for municipal wastewater reclamation

In the present work, the disinfection of actual effluents from a municipal wastewater treatment plant (WWTP) by a conductive diamond sono-electrochemical process was assessed. First, efficiency of single electrodisinfection process with diamond anodes (without the contribution of ultrasounds) was studied, finding that the total disinfection can be attained at current charges applied below 0.02 kA h m⁻³. It was also found that the main disinfection mechanism is the attack of Escherichia coli (E. coli) by the disinfectants produced in the electrochemical cell and that the production of chlorates is avoided when working at current densities not higher than 1.27 A m⁻². Next, a marked synergistic effect was found when coupling ultrasound (US) irradiation to the electrochemical system (sono-electrochemical disinfection). This increase in the disinfection rate was found to be related to the suppression of the agglomeration of E. coli cells and the enhancement in the production of disinfectant species.     

Disinfection effect of a continuous-flow ultrasound/ultraviolet baffled reactor at a pilot scale

An ultrasound/ultraviolet (US/UV) baffled reactor was developed to fill the gap in ultraviolet (UV) disinfection associated with disinfection efficiency. According to the previously selected operational condition, a continuous-flow US/UV baffled reactor was continuously operated in a wastewater treatment plant at a pilot scale for nearly three months, and the disinfection influent and effluent were analyzed, including fecal coliforms, Escherichia coli, and fecal streptococci. The US/UV baffled reactor could guarantee a high effluent disinfection performance in terms of fecal coliforms removal even with the fluctuation of the secondary effluent. All the disinfected effluents satisfied the requirement of the “Pollutants Discharge Standard of Municipal Wastewater Treatment Plant in China” (fecal coliforms below 1000 CFU/L for class 1A), and 87% of the tested fecal coliforms concentration in the disinfected effluent was below 100 CFU/L, nearly eliminating all fecal coliforms. Further analysis of the E. coli and fecal streptococci showed the broad disinfection ability and high disinfection efficiency of the US/UV baffled reactor. The flexibility of the specific energy consumption for the disinfection system depends on the water quality.     

Optimization of hydrostatic pressure at varied sonication conditions – power density,intensity, very low frequency – for isothermal ultrasonic sludge treatment

This work aims at investigating for the first time the key sonication (US) parameters: power density (D_US), intensity (I_US), and frequency (F_S) – down to audible range, under varied hydrostatic pressure (P_h) and low temperature isothermal conditions (to avoid any thermal effect).The selected application was activated sludge disintegration, a major industrial US process. For a rational approach all comparisons were made at same specific energy input (ES, US energy per solid weight) which is also the relevant economic criterion.The decoupling of power density and intensity was obtained by either changing the sludge volume or most often by changing probe diameter, all other characteristics being unchanged. Comprehensive results were obtained by varying the hydrostatic pressure at given power density and intensity. In all cases marked maxima of sludge disintegration appeared at optimum pressures, which values increased at increasing power intensity and density. Such optimum was expected due to opposite effects of increasing hydrostatic pressure: higher cavitation threshold then smaller and fewer bubbles, but higher temperature and pressure at the end of collapse.In addition the first attempt to lower US frequency down to audible range was very successful: at any operation condition (D_US, I_US, P_h, sludge concentration and type) higher sludge disintegration was obtained at 12 kHz than at 20 kHz. The same values of optimum pressure were observed at 12 and 20 kHz.At same energy consumption the best conditions – obtained at 12 kHz, maximum power density 720 W/L and 3.25 bar – provided about 100% improvement with respect to usual conditions (1 bar, 20 kHz). Important energy savings and equipment size reduction may then be expected.     

Ultrasonic preparation of cationic cotton and its application in ultrasonic natural dyeing

Cationization of cotton fabric was conferred by the sonicator reaction of cellulose with bromoacetyl bromide, followed by substitution of the terminal bromo groups by triethylamine. Experiments showed that the optimal volume of bromoacetyl bromide necessary to succeed the first stage was 0.4 mL. The order of weight gain for various processes indicates, ultrasound, 25 kHz > ultrasound, 40 kHz > mechanical stirring. Also, for the second stage the order of nitrogen contents indicates ultrasound, 25 kHz > ultrasound, 40 kHz > mechanical stirring. The structures of both untreated and cationic fibres were investigated by FTIR spectroscopy. Modified cotton fabric was subsequently dyed in both conventional and ultrasonic techniques with isosalipurposide dye isolated from Acacia cyanophylla yellow flowers. The effect of dye bath pH, ultrasonic power and frequency, dyeing time and temperature were studied and the order of K/S values indicates ultrasound, 25 kHz > ultrasound, 40 kHz > CH. ultrasound was also found to enhance the dye uptake and the overall fastness properties. Analysis of the sorption isotherms of isosalipurposide dye on cationic cotton fabric shows that the Languimir isotherm equation is best able to correlate the data.     

Investigation of acoustic cavitation energy in a large-scale sonoreactor

Acoustic cavitation energy distributions were investigated for various frequencies such as 35, 72, 110 and 170 kHz in a large-scale sonoreactor. The energy analyses were conducted in three-dimensions and the highest and most stable cavitation energy distribution was obtained not in 35 kHz but in 72 kHz. However, the half-cavitation-energy distance was larger in the case of 35 kHz ultrasound than in the case of 72 kHz, demonstrating that cavitation energy for one cycle was higher for a lower frequency. This discrepancy was due to the large surface area of the cavitation-energy-meter probe. In addition, 110 and 170 kHz ultrasound showed a very low and poor cavitation energy distribution. Therefore larger input power was required to optimize the use of higher frequency ultrasound in the sonoreactor with long-irradiation distance. The relationship between cavitation energy and sonochemical efficiency using potassium iodide (KI) dosimetry was best fitted quadratically. From 7.77 × 10^?10 to 4.42 × 10^?9 mol/J of sonochemical efficiency was evaluated for the cavitation energy from 31.76 to 103. 67 W. In addition, the cavitation energy attenuation was estimated under the assumption that cavitation energy measured in this study would be equivalent to sound intensity, resulting in 0.10, 0.18 and 2.44 m^?1 of the attenuation coefficient (α) for 35, 72 and 110 kHz, respectively. Furthermore, α/(frequency)² was not constant, as some previous studies have suggested.     

Dielectric relaxation of CsHSeO4 above room temperature

Dielectric measurements of CsHSeO₄ show a distinct relaxation at low frequencies at several isotherms (T < 363 K). For example, the relaxation frequency is around 4 kHz at 323 K and increases to higher frequencies (~ 100 kHz) as the temperature increases. The relaxation has an activation energy of 0.8 eV, which is in close agreement with that associated with transport of charge carriers. We suggest that the observed dielectric relaxation could be produced by the H⁺ jump and SeO₄^? 2 reorientation that cause distortion and change the local lattice polarizability, inducing dipoles like HSeO₄^?.     

Coumarin fluorometry to quantitatively detectable OH radicals in ultrasound aqueous medium

When ultrasound (US) was exposed to aqueous coumarin solution in air atmosphere, the UV–visible and fluorescence spectra of the probe were measured at different US exposure times. The US exposure was carried out at 43 kHz and 500 kHz with different out-put power. It was found that the 500 kHz US produced umbelliferone fluorescence, while the 43 kHz US had no fluorescence. In addition, the coumarin absorbance at 270 nm maximum was decreased with in cases of the US exposure time. In contrary, the fluorescent intensity of umbelliferone at 460 nm increased with increasing of US exposure time. This exhibited that the coumarin probe was converted to umbelliferone by the US exposure, when the 500 kHz US was operated. This was facted that the coumarin framework was caused with addition of OH groups which was generated by the 500 kHz US. Therefore, the umbelliferone fluorescent became a probe to estimate OH radical in US medium. Furthermore, the chemo-fluorometry showed that the emission maximum of the formed umbelliferone could probe the bulk pHs in the US aqueous medium.     

Enhanced OH radical generation by dual-frequency ultrasound with TiO2 nanoparticles: Its application to targeted sonodynamic therapy

The present study demonstrated the enhanced hydroxyl (OH) radical generation by combined use of dual-frequency (0.5 MHz and 1 MHz) ultrasound (US) and titanium dioxide (TiO₂) nanoparticles (NPs) as sonocatalyst. The OH radical generation became the maximum, when 0.5 MHz US was irradiated at an intensity of 0.8 W/cm² and 1 MHz US was irradiated at intensities at 0.4 W/cm² in the presence of TiO₂ NPs under the examined conditions. After incorporation of TiO₂ NPs modified with targeting protein pre-S1/S2, HepG2 cancer cells were subjected to the dual-frequency US at optimum irradiation intensities (“targeted-TiO₂/dual-US treatment”). Growth of the HepG2 cells was reduced by 46% compared with the control condition after irradiation of dual-frequency US for 60 s with TiO₂ NPs incorporation. In contrast, HepG2 cell growth was almost the same as that in the control condition when cells were irradiated with either 0.5 MHz or 1 MHz ultrasound alone without TiO₂ NP incorporation.