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1.
Hydrodynamic cavitation (HC) and Fe(II) are advanced oxidation processes, in which pentachlorophenol (PCP) is treated by the redox method of activating persulfate (PS). The kinetics and mechanism of the HC and Fe(II) activation of PS were examined in aqueous solution using an electron spin resonance (ESR) spin trapping technique and radical trapping with pure compounds. The optimum ratio of Fe(II)/PS was 1:2, and the hydroxyl radical (HO) and sulfate radical (SO4−) generation rate were 5.56 mM h−1 and 8.62 μM h−1, respectively. The generation rate and Rct of HO and SO4− at pH 3 and 50 °C in the Fe(II)/PS/HC system are 7584.6 μM h−1, 0.013 and 24.02 μM h−1, 3.95, respectively. The number of radicals was reduced as the pH increased, and it increased with increasing temperature. The PCP reaction rate constants was 4.39 × 10−2 min−1 at pH 3 and 50 °C. The activation energy was 10.68 kJ mol−1. In addition, the mechanism of PCP treatment in the Fe(II)/PS/HC system was a redox reaction, and the HO−/SO4− contribution was 81.1 and 18.9%, respectively. In this study, we first examined PCP oxidation through HO and SO4− quantification using only the Fe(II)/PS/HC process. Furthermore, the results provide the foundation for activation of PS by HC and Fe(II), but also provide a data basis for similar organic treatments other than PCP. 相似文献
2.
Acoustic cavitation and sonochemical reactions play a significant role in various applications of ultrasound. A number of dosimetry methods are in practice to quantify the amount of radicals generated by acoustic cavitation. In this study, hydroxyl radical (OH) yields measured by Weissler, Fricke and terephthalic acid dosimetry methods have been compared to evaluate the validities of these methods using a 490 kHz high frequency sonochemical reactor. The OH yields obtained after 5 min sonication at 490 kHz from Weissler and Fricke dosimetries were 200 µM and 289 µM, respectively. Whereas, the OH yield was found to be very low (8 µM) when terephthalic acid dosimetry was used under similar experimental conditions. While the results agree with those reported by Iida et al. (Microchem. J., 80 (2005) 159), further mechanistic details and interfering reactions have been discussed in this study. For example, the amount of OH determined by the Weissler and Fricke methods may have some uncertainty due to the formation of HO2 in the presence of oxygen. In order to account for the major discrepancy observed with the terephthalic acid dosimetry method, high performance liquid chromatography (HPLC) analysis was performed, where two additional products other than 2-hydroxy terephthalic acid were observed. Electrospray ionization mass spectrometry (ESI-MS) analysis showed the formation of 2,5-dihydroxyterephthalic acid as one of the by-products along with other unidentified by-products. Despite the formation of additional products consuming OH, the reason for a very low OH yield obtained by this dosimetry could not be justified, questioning the applicability of this method, which has been used to quantify OH yields generated not only by acoustic cavitation, but also by other processes such as γ-radiolysis. The authors are hoping that this Opinion Paper may initiate further discussion among researchers working in sonochemistry area that could help resolve the uncertainties around using these dosimetry methods. 相似文献
3.
Sonochemiluminescence (SCL) from aqueous solution of lucigenin (Luc2+) has been studied using aliphatic amines as coreactant. The SCL intensity are strongly dependent on the dissolved gases such as air, oxygen, nitrogen and argon. The most strong SCL signals are observed from oxygen saturated alkaline solution containing Luc2+ when small amount of trialkylamine, such as tripropylamine (TPrA) was added into the solution. In an ultrasonic field, TPrA can adsorb onto the cavitation bubble/solution interface where TPrA is oxidized by OH to form a radical cation TPrA+ and subsequently produce a highly reducing TPrA species through a deprotonation reaction of the TPrA+. TPrA is suggested to initiate the reduction reactions of Luc2+ and molecule oxygen to produce Luc+ and superoxide radical anion (O2−), respectively. The radical-radical coupling reaction between Luc+ and O2− is expected to initiate the light emission. The production of O2− is examined by spectrofluorometric method using 2-(2-pyridyl)benzothiazoline as a fluorescent probe. The results show that the production of O2− by ultrasound was more efficient in oxygen saturated solution in the presence of coreactants, consistent with the results with SCL measurements. 相似文献
4.
Zinc oxide NPs were synthesized solvothermally within sonochemical mediation and characterized by XRD, FTIR, SEM, EDX, elemental mapping, TEM and UV–vis. spectrophotometry. To evaluate the hydroxyl radicals (OH) scavenging activity of arils extract of Egyptian (EGY-PAM) and Yemeni Punica granatum (YEM-PAM), the developed zinc oxide nano particles (ZnO NPs) as a highly productive source of hydroxyl radicals (under Solar-illumination) was used. The yield of OH was trapped and probed via fluorimetric monitoring. This suits the first sensitive/selective photoluminescent avenue to evaluate the OH scavenging activity. The high percentage of DPPH radical scavenging reflected higher contents of phenolics, flavonoids, and anthocyanins that were found in EGY-PAM and YEM-PAM. Although, some secondary metabolites contents were significantly different in EGY-PAM and YEM-PAM, the traditional DPPH radical scavenging methodology revealed insignificant IC50. Unlike, the developed fluorimetric probing, sensitively discriminated the OH scavenging activity with IC50 (105.7 µg/mL) and lower rate of OH productivity (k = 0.031 min−1) in case of EGY-PAM in comparison to IC50 (153.4 µg/mL) and higher rate of OH productivity (k = 0.053 min−1) for YEM-PAM. Our findings are interestingly superior to the TBHQ that is synthetic antioxidant. Moreover, our developed methodology for fluorimetric probing of OH radicals scavenging, recommends EGY-PAM as OH radicals scavenger for diabetic patients while YEM-PAM exhibited a better OH radicals scavenging appropriate for high blood pressure patients. More interestingly, EGY-PAM and YEM-PAM exhibited high anticancer potentiality. The aforementioned OH and DPPH scavenging activities as well as the anticancer potentiality present EGY-PAM and YEM-PAM as promising sources of natural antioxidants, that may have crucial roles in some chronic diseases such as diabetics and hypertension in addition to cancer therapeutic protocols. 相似文献
5.
Numerical simulations have been performed on a range of ambient bubble radii, in order to reveal the effect of mass transport, heat exchange and chemical reactions heat on the chemical bubble yield of single acoustic bubble. The results of each of these energy mechanisms were compared to the normal model in which all these processes (mass transport, thermal conduction, and reactions heat) are taken into account. This theoretical work was carried out for various frequencies (f: 200, 355, 515 and 1000 kHz) and different acoustic amplitudes (PA: 1.5, 2 and 3 atm). The effect of thermal conduction was found to be of a great importance within the bubble internal energy balance, where the higher rates of production (for all acoustic amplitudes and wave frequencies) are observed for this model (without heat exchange). Similarly, the ignorance of the chemical reactions heat (model without reactions heat) shows the weight of this process into the bubble internal energy, where the yield of the main species (OH, H, O and H2) for this model was accelerated notably compared to the complete model for the acoustic amplitudes greater than 1.5 atm (for f = 500 kHz). However, the lowest production rates were registered for the model without mass transport compared to the normal model, for the acoustic amplitudes greater than 1.5 atm (f = 500 kHz). This is observed even when the temperature inside bubble for this model is greater than those retrieved for the other models. On the other hand, it has been shown that, at the acoustic amplitude of 1.5 atm, the maximal production rates of the main species (OH, H, O and H2) for all the adopted models appear at the same optimum ambient-bubble size (R0 ~ 3, 2.5 and 2 µm for, respectively, 355, 500 and 1000 kHz). For PA = 2 and 3 atm (f = 500 kHz), the range of the maximal yield of OH radicals is observed at the range of R0 where the production of OH, O and H2 is the lowest, which corresponds to the bubble temperature at around 5500 K. The maximal production rate of H, O and H2 is shifted toward the range of ambient bubble radii corresponding to the bubble temperatures greater than 5500 K. The ambient bubble radius of the maximal response (maximal production rate) is shifted toward the smaller bubble sizes when the acoustic amplitude (wave frequency is fixed) or the ultrasound frequency (acoustic power is fixed) is increased. In addition, it is observed that the increase of wave frequency or the acoustic amplitude decrease cause the range of active bubbles to be narrowed (scenario observation for the four investigated models). 相似文献
6.
As an advanced oxidation process with a wide range of applications, sonochemistry relies on acoustic cavitation to induce free radicals for degrading chemical contaminants. The complete process includes two critical steps: the radical production inside the cavitation bubble, and the ensuing dispersion of these radicals into the bulk solution. To grasp the physicochemical details in this process, we developed an integrated numerical scheme with the ability to quantitatively describe the radical production-dispersion behavior. It employs coupled simulations of bubble dynamics, intracavity chemical reactions, and diffusion–reaction-dominated mass transport in aqueous solutions. Applying this method to the typical case of argon and oxygen bubbles, the production mechanism for the main radicals is revealed. Moreover, the temporal-spatial distribution of the radicals in the liquid phase is presented. The results demonstrate that the enhanced radical production observed in oxygen bubbles can be traced to the initiation reaction O2 + H2O → OH+HO2, which requires relatively low activation energy. In the outside liquid region, the dispersion of radicals is limited by robust recombination reactions. The simulated penetration depth of OH is around 0.2 μm and agrees with reported experimental measurements. The proposed numerical approach can be employed to better capture the radical activity and is instrumental in optimizing the engineering application of sonochemistry. 相似文献
7.
Reactive electrochemical membrane (REM) allows electrochemical oxidation (EO) water purification under flow-through operation, which improves mass transfer on the anode surface significantly. However, O2 evolution reaction (OER) may cause oxygen bubbles to be trapped in small-sized confined flow channels, and thus degrade long-term filterability and treatability of REM. In this study, ultrasound (ultrasonic vibrator, 28 kHz, 180 W) was applied to EO system (i. e. sonoelectrochemistry) containing titanium suboxide-REM (TiSO-REM) anode for enhanced oxidation of 4-chlorophenol (4-CP) target pollutant. Both experimental and modeling results demonstrated that ultrasound could mitigate the retention of O2 bubbles in the porous structures by destructing large-size bubbles, thus not only increasing permeate flux but also promoting local mass transfer. Meanwhile, oxidation rate of 4-CP for EO with ultrasound (EO-US, 0.0932 min−1) was 216% higher than that for EO without ultrasound (0.0258 min−1), due to enhanced mass transfer and OH production under the cavitation effect of ultrasound. Density functional theory (DFT) calculations confirmed the most efficient pathway of 4-CP removal to be direct electron transfer of 4-CP to form [4-CP]+, followed by subsequent oxidation mediated by OH produced from anodic water oxidation on TiSO-REM anode. Last, the stability of TiSO-REM could be improved considerably by application of ultrasound, due to alleviation of electrode deactivation and fouling, indicated by cyclic test, scan electron microscopy (SEM) observation and Fourier transform infrared spectroscopy (FT-IR) characterization. This study provides a proof-of-concept demonstration of ultrasound for enhanced EO of recalcitrant organic pollutants by REM anode, making decentralized wastewater treatment more efficient and more reliable. 相似文献
8.
The effectiveness and synergistic mechanisms of combining ultrasonic process (US) with peroxymonosulfate (PMS) were investigated using Bisphenol A (BPA) and Dimethyl Phthalate (DMP) as the model pollutants. Synergy between US and PMS improved the degradation of target pollutants, and PMS was found to play a dual role. The optimum dosage of PMS and the extent of efficiency promotion were found to depend on not only the ultrasonic frequency but also on the hydrophobicity of target pollutants. The scavenger quenching experiments and electron paramagnetic resonance analysis indicated that OH was responsible for DMP degradation in both US and US/PMS processes. The chemical probe experiments also proved that activation of PMS could increase the production of OH while excess PMS consumed the available radicals. Furthermore, it was found for the first time that the constituent salts of KHSO4 and K2SO4 in the commercial Oxone also made considerable influence on US/PMS process. It was also found that the combination of US and PMS showed more pronounced synergistic effect for treating DMP at lower concentrations. Higher efficiency was achieved at more acidic condition and similar efficiencies were obtained at pH range of 5.1 ~ 8.12. DMP degradation pathways were found to be the OH addition to the aromatic ring and hydrogen absorption at the aliphatic chains with and without the presence of PMS, but much better mineralization capability was obtained in the presence of PMS than ultrasonic degradation alone. 相似文献
9.
In this work, after exploring the first report on the synergism of combining ultrasound (US: 600 kHz) and chlorine toward the degradation of Allura Red AC (ARAC) textile dye, as a contaminant model, the impact of various mineral water constituents (Cl−, SO42−, NO3−, HCO3− and NO2−) and natural organic matter, i.e., humic acid (HA), on the performance of the US/chlorine sono-hybrid process was assessed for the first time. Additionally, the process effectiveness was evaluated in a real natural mineral water (NMW) of a known composition. Firstly, it was found that the combination of ultrasound and chlorine (0.25 mM) at pH 5.5 in cylindrical standing wave ultrasonic reactor (f = 600 kHz and Pe = 120 W, equivalent to PA ∼ 2.3 atm) enhanced in a drastic manner the degradation rate of ARAC; the removal rate being 320% much higher than the arithmetic sum of the two separated processes. The source of the synergistic effect was attributed to the effective implication of reactive chlorine species (RCS: Cl, ClO and Cl2−) in the degradation process. Radical probe technique using nitrobenzene (NB) as a specific quencher of the acoustically generated hydroxyl radical confirmed the dominant implication of RCS in the overall degradation rate of ARAC by US/chlorine system. Overall, the presence of humic acid and mineral anions decreased the efficiency of the sono-hybrid process; however, the inhibition degrees depend on the type and the concentration of the selected additives. The reaction of these additives with the generated RCS is presumably the reason for the finding results. The inhibiting effect of Cl−, SO42−, NO3− and NO2− was more pronounced in US/chlorine process as compared to US alone, whereas the inverse scenario was remarked for the effect of HA. These outcomes were associated to the difference in the reactivity of HA and mineral anions toward RCS and OH oxidizing species, in addition to the more selective character of RCS than hydroxyl radical. The displacement of the reaction zone with increasing the additive concentration may also be another influencing factor that favors competition reactions, which subsequently reduce the available reactive species in the reacting medium. The NMW exerted reductions of 43% and 10% in the process efficiency at pH 5.5 and 8, respectively, thereby confirming the RCS-quenching mechanism by the water matrix constituents. Hence, this work provided a precise understanding of the overall mechanism of chlorine activation by ultrasound to promote organic compounds degradation in water. 相似文献
10.
Ozonation (OZ) is an important advanced oxidation process to purify water and wastewater. Because of the lower solubility and instability of ozone (O3), selective oxidation and dependence on pH value, the industrial applications of OZ have been hindered by the following disadvantages: incomplete removal of pollutants, lower mineralization efficiency and the formation of toxic by-products. Meanwhile, OZ seems to have higher processing costs than other technologies. To improve the treatment efficiency and O3 utilization, several combined processes, such as H2O2/O3, UV/O3, and Cavitation/O3, have been explored, while the combined method of ultrasonication (US) with OZ is a promising treatment technology with a complex physicochemical mechanism. In US alone, the sonolysis of water molecules can produce more powerful unselective oxidant hydroxyl radicals (OH), and directly cause the sonochemical pyrolysis of volatile pollutants. In US/OZ, US can promote the mass transfer of O3, and also drive the chemical conversion of O3 to enhance the formation of OH. Various layouts of US/OZ devices and the interactive effects of US/OZ (synergism or antagonism) on the degradation of various organics are illustrated in this review. The main factors, including US frequency, pH value, and radical scavengers, significantly affect the mass transfer and decomposition of O3, the formation of OH and H2O2, the degradation rates of organics and the removal efficiencies of COD and TOC (mineralization). As a result, US can significantly increase the yield of OH, thereby improving the degradation efficiency and mineralization of refractory organics. However, US also enhances the decomposition of ozone, thereby reducing the concentration of O3 in water and impairing the efficiency of selective oxidation with O3 molecules. 相似文献
11.
Coupling ultrasound with other remediation technologies has potential to result in synergistic degradation of contaminants. In this work, we evaluated synergisms from adding high-power ultrasound (20 kHz; 250 W) to activated persulfate over a range of bulk temperatures (20–60 °C). We studied the aqueous degradation kinetics of three polycyclic aromatic hydrocarbons (PAHs: naphthalene, phenanthrene, and fluoranthene) treated by ultrasound-alone, heat-activated persulfate, and combined ultrasonically-activated persulfate (US-PS). At 20 °C, observed US-PS rate constants strongly correlated with Wilke-Chang diffusion coefficients. This correlation indicates PAH molecules diffuse to the bubble-water interface prior to reaction with sulfate radicals (SO4−) generated at the interface. At higher temperatures, observed US-PS rate constants appear to be a more complicated function of temperature and diffusion coefficients. Synergy indexes for PAHs with fast diffusion coefficients were greatest at 20 °C. Fluoranthene, the largest and most hydrophobic PAH, had a maximum synergy index at 30 °C; it benefited from additional thermal persulfate activation in bulk solution. Fluoranthene synergy indexes, however, decreased above 30 °C and became antagonistic at 60 °C. Electron paramagnetic resonance (EPR) spin trapping was used to quantify hydroxyl radical (OH) produced from acoustic cavitation in the absence of persulfate. These data showed consistent OH production from 20 to 60 °C, indicating PAH antagonisms at 60 °C were not due to lower bubble collapse temperatures. Instead, the results suggest that PAH antagonisms are caused by increased radical–radical recombination as bulk temperature increases. In effort to develop an efficient, combined remediation technology, this work suggests bulk temperatures between 20 and 40 °C maximize US-PS synergisms. 相似文献
12.
Ultrasound-engineered synthesis of WS2@CeO2 heterostructure for sonocatalytic degradation of tylosin
The main aim of the present investigation was the intercalation of WS2 nanosheets in the structure of ceria (CeO2) to be used for the efficient catalytic destruction of tylosin (TYL) as a macrolide antibiotic in water. As-synthesized heterostructured catalyst was placed in a sono-reactor (40 kHz and 300 W) in order to degrade TYL through the sonocatalysis. 15 wt% WS2/CeO2 was chosen for performing the systematic experiments. Decreasing the concentration of TYL, along with increasing the WS2/CeO2 dosage led to reduced degradation efficiency. The water hardness was demonstrated to be a suppressive agent on the sonocatalysis of the target pollutant. As-generated holes, OH, and also O2− were responsible for the degradation of TYL. Increasing the ultrasound power and operating temperature enhanced the degradation efficiency. The degradation rate boosted up when the temperature was raised from 10 °C (0.0107 1/min) to 40 °C (0.0165 1/min). Moreover, the lowest activation energy (Ea) for sonocatalytic degradation was obtained as 10.81 kJ/mol. The sonocatalytic activity of WS2/CeO2 in the sono-reactor encountered insignificant change within five consecutive operational runs (~15% reduction). The mechanism and pathways of the sonocatalytic decomposition of TYL are also proposed. 相似文献
13.
Facet engineering of nanocomposite has been confirmed to be an efficient strategy to accelerate their catalytic performances, but to improve their piezoelectric catalytic activities by facet engineering has been seldom reported. Herein, we developed a series of SrTiO3 nanocrystals with exposed {0 0 1} facet, dominant {1 1 0} facet and co-exposed {0 0 1} and {1 1 0} facets, respectively, and firstly revealed its piezoelectric catalytic performance under ultrasonic vibration. Moreover, the relationship between piezoelectric-induced catalytic activity and facet-dependence of SrTiO3 nanocrystal was disclosed for the first time. The SrTiO3 nanocrystal with co-exposed {0 0 1} and {1 1 0} facets exhibited effectively enhanced piezoelectric catalytic activity by degrading Rhodamine B (RhB) under ultrasonic vibration, as compared to that of SrTiO3 nanocrystals with exposed {0 0 1} facet and dominant {1 1 0} facet, respectively. In addition, trapping experiments and active species quantitative experiments confirmed that the co-exposed {0 0 1} and {1 1 0} facets were beneficial to produce O2− and OH with the generation rates of 8.3 and 132.2 μmol g−1 h−1, respectively. The OH radical played a dominant role in piezoelectric catalytic process. Finally, the piezoelectric catalysis mechanism of SrTiO3 surface heterojunction was proposed based on a DFT study. This study presents an in-depth understanding of piezoelectric-induced catalytic of perovskite nanocrystals with exposed well-defined facets. 相似文献
14.
The electrochemiluminescence (ECL) of tris(2,2′-bipyridine)ruthenium(II) (Ru(bpy)32+) in the presence of lidocaine was investigated under ultrasound (US) irradiation. The sonoelectrochemical experiments are conducted by indirect irradiation of ultrasound with a piezoelectric transducer operating at 430 kHz. In a supporting electrolyte at pH 11, the Ru(bpy)32+/lidocaine system gave weak ECL peaks around +1.2 V and +1.45 V, respectively. The ECL signal at +1.2 V was attributed to redox reactions of the oxidative intermediates of Ru(bpy)32+ and lidocaine, while the signal at +1.45 V was assumed to be caused by an advanced oxidation process due to the generation of hydroxyl radicals (OH) at the electrode surface. In this study, the potential modulation approach is employed in the study of ECL process upon US irradiations because it can suppress the noise components from sonoluminescence effectly and improve the resolution of ECL-potential profiles. It is found ECL signals were greatly enhanced upon US irradiation at the output power of 30 W, however, the relative intensity of ECL signal at +1.2 V was larger than that obtained with a rotating disk electrode even though the mass transport effect is equilvalent. The experiment results suggest that the chemical effect (i.e., generation of OH) by 430 kHz US becomes remarkable in the electrochemical process. Detailed ECL reaction routes under US are proposed in this study. 相似文献
15.
Hydrodynamic cavitation experiments in microfluidic systems have been performed with an aqueous solution of luminol as the working fluid. In order to identify where and how much reactive radical species are formed by the violent bubble collapse, the resulting chemiluminescent oxidation reaction of luminol was scrutinized downstream of a constriction in the microchannel. An original method was developed in order to map the intensity of chemiluminescence emitted from the micro-flow, allowing us to localize the region where radicals are produced. Time averaged void fraction measurements performed by laser induced fluorescence experiments were also used to determine the cavitation cloud position. The combination void fraction and chemiluminescence two-dimensional mapping demonstrated that the maximum chemiluminescent intensity area was found just downstream of the cavitation clouds. Furthermore, the radical yield can be obtained with our single photon counting technique. The maximum radical production rates of 1.2*107 OH/s and radical production per processed liquid volume of 2.15*1010 HO/l were observed. The proposed technique allows for two-dimensional characterisation of radical production in the microfluidic flow and could be a quick, non-intrusive way to optimise hydrodynamic cavitation reactor design and operating parameters, leading to enhancements in wastewater treatments and other process intensifications. 相似文献
16.
Currently, the polluted wastewater discharged by industry accounts for the major part of polluted bodies of water. As one of the industrial wastewaters, dye wastewater is characterized by high toxicity, wide pollution, and difficulty in decolorization degradation. In this paper, a novel composite nanomaterial catalyst of silver was prepared by using Angelica sinensis polysaccharide (ASP) as a reducing and stabilizing agent. And the optimum reaction conditions explored are VAgNO3 = 5 mL (300 mM) and vASP = 7% (w/v) for 6 h at 90 °C. In addition, the ASP-Ag nanocatalyst was characterized by several techniques. The results demonstrated that ASP-Ag nanoparticles were successfully synthesized. Degradation rate, which provides a numerical visualization of the percentage reduction in pollutant concentration. With the wrapping of ASP, the ultrasonic catalytic degradation rates of different organic dyes including rhodamine B (RB), methylene blue (MB), and methyl orange (MO) were from 88.2%, 88.7%, and 85.2% to 96.1%, 95.2% and 93.5% at room temperature, respectively. After the experiments, when cdyes = 10 mg/L, the highest degradation rate can be observed under cAPS-AgNPs = 10 mg/L with the most powerful cavitation frequency f = 59 kHz. The effect of ultrasonic frequency on the acoustic pressure distribution in the reactor was investigated by using COMSOL Multiphysis@ software to propose the mechanism of ultrasonic degradation and the mechanism was confirmed by OH radical trapping experiments. It indicates that OH produced by the ultrasonic cavitation effect plays a determinant role in the degradation. And then, the intermediate products of the dye degradation process were analyzed by gas chromatography and mass spectrometry (GC–MS), and the possible degradation processes of dyes were proposed. The resulting products of degradation are SO42−, NH4+, NO3−, N2, CO2 and H2O. Finally, the recycling degradation experiments showed that catalyst maintains a high degradation rate within reusing 5 cycles. Thus, this catalyst is highly efficient and recyclable. 相似文献
17.
Promoting processing efficiency and taking advantage of agricultural by-products are two promising ways to achieve sustainable textile industry. This study presents a customized efficient ultrasonic-assisted bleaching strategy for yak hair – a widely existing but underexploited secondary dark shade fibre from yak. A melanin-targeted Fenton oxidation process is established which involves three phases, i.e., (I) incorporation of Fe2+ ions with melanin, (II) catalytic oxidative bleaching using hydrogen peroxide (H2O2), and (III) reductive cleansing. The bleaching efficacy, dyeing performance and tensile property of yak hair treated with and without ultrasound were explored and compared. Further, the ultrasonic bleaching mechanism in terms of the catalytic effect of Fe2+ ions, the promotion of H2O2 decomposition, removal of melanin granule from yak hair, were demonstrated. Finally, the main effects and interactions of parameters in phase II, and optimal condition were obtained through mathematical modelling based on a central composite design (CCD). Results reveal that ultrasonic bleaching dramatically enhances the whiteness index (WI) of yak hair from 11 to 45 which is 44.6% higher than those bleached without ultrasound, and also promotes the uptake of acid dyes. There is only 15% tensile strength loss and 14% elongation increment of yak hair after ultrasonic bleaching, rising from a slight damage of cuticle layer and cleavage of disulfide bonds, respectively. In the study of bleaching mechanism, Fe2+ ion is confirmed to improve the H2O2 decomposition rate by 20.9% which further runs up to 35.9% after introducing ultrasound. Ultrasound increases the concentration of hydroxyl radicals (HO) by 94% which are the main oxidative species participating in bleaching confirmed by HO scavenging experiment. The porous structure was observed on the cross section of yak hair stemming from the removal of melanin granules contributed by the cleaning action of ultrasound. A theoretical highest WI of 52.4 can be achieved under an optimal condition based on the CCD study. In general, the proposed melanin-targeted bleaching strategy for yak hair that integrates ultrasonic technology and Fenton reaction, is beneficial to the development of sustainable textile industry from material and processing perspectives. 相似文献
18.
The sonocatalytic degradation of EDTA (C0 = 5 10−3 M) in aqueous solutions was studied under 345 kHz (Pac = 0.25 W mL−1) ultrasound at 22–51 °C, Ar/20%O2, Ar or air, and in the presence of metallic titanium (Ti0) or core-shell Ti@TiO2 nanoparticles (NPs). Ti@TiO2 NPs have been obtained using simultaneous action of hydrothermal conditions (100–214 °C, autogenic pressure P = 1.0–19.0 bar) and 20 kHz ultrasound, called sonohydrothermal (SHT) treatment, on Ti0 NPs in pure water. Ti0 is composed of quasi-spherical particles (30–150 nm) of metallic titanium coated with a metastable titanium suboxide Ti3O. SHT treatment at 150–214 °C leads to the oxidation of Ti3O and partial oxidation of Ti0 and formation of nanocrystalline shell (10–20 nm) composed of TiO2 anatase. It was found that Ti0 NPs do not exhibit catalytic activity in the absence of ultrasound. Moreover, Ti0 NPs remain inactive under ultrasound in the absence of oxygen. However, significant acceleration of EDTA degradation was achieved during sonication in the presence of Ti0 NPs and Ar/20%O2 gas mixture. Coating of Ti0 with TiO2 nanocrystalline shell reduces sonocatalytic activity. Pristine TiO2 anatase nanoparticles do not show a sonocatalytic activity in studied system. Suggested mechanism of EDTA sonocatalytic degradation involves two reaction pathways: (i) sonochemical oxidation of EDTA by OH/HO2 radicals in solution and (ii) EDTA oxidation at the surface of Ti0 NPs in the presence of oxygen activated by cavitation event. Ultrasonic activation most probably occurs due to the local heating of Ti0/O2 species at cavitation bubble/solution interface. 相似文献
19.
Sonoluminescence (SL) is an interesting physical effect which can convert acoustic energy into light pulses. Up to now, the microscopic mechanism of the SL has not yet been fully clear. It is known that hydroxyl radicals play the important role for SL from water. In this work, we take advantage of carbon nano-dots (CNDs) as free radical captors to modulate the hydroxyl radicals (OH) in SL effect. Through studying the single bubble SL (SBSL) from CND aqueous solution (CNDAS) with trace amount of CNDs, we find that the color of SBSL is tuned dramatically from blue in water to green in CNDAS. Two different SL mechanisms can be identified from emission spectrum. One comes from blackbody-like radiation and another is attributed from the characteristic emission with identified peaks. The decrease in the yield of H2O2 in the presence of CNDs suggests the modulation effect on SL via OH interacting with CNDs. By comparison of the CNDs before and after sonication, it is found that hydroxyl radicals generated during SL can take part in the chain-like oxidation of the chemical groups attached to the CNDs to form larger amount of carboxyl groups. The blackbody temperature of blackbody-like radiation decreases from 15,600 K in water to 11,300 K in CNDAS. Moreover, the emission from hydroxyl radicals and two new luminescent centers related to carboxyl groups are introduced in SL from CNDAS. These important and interesting findings indicate that by adding trace amount of CNDs in water, the effect of SBSL can be significantly modulated, which can provide a macroscopic phenomenon for gaining an insight into the microscopic mechanism of the SL effect. 相似文献
20.
This study was designed to optimize the extraction rate of total polyphenols and ellagic acid from pomegranate flowers. Single factors were investigated for liquid-to-material ratio (5–25), ethanol concentration (20%–60%), sonication time (5–60 min), and sonication power (150–500 W). The level range of the Box-Bokhen design was determined with respect to the single-factor results. The components of each index were normalized using the entropy weighting method for obtaining the comprehensive evaluation value. Under the actual conditions, the final optimization results were 17 for liquid-to-material ratio, 43% for ethanol concentration, 10 min for ultrasonic time, and 300 W for ultrasonic power. The extracts obtained under optimal conditions were tested for the inhibition of Streptococcus mutans and its biofilm, and results showed that pomegranate flowers exerted some inhibitory effects on the bacterium. Phosphomolybdenum and FRAP assays were used, and DPPH, ABTS, and O2− radical scavenging tests were conducted, indicating that pomegranate flower extracts have good antioxidant capacity. 相似文献