•Combined treatment strategies based on hydrodynamic cavitation are effective for DNP removal.•Combination of hydrodynamic cavitation with activated persulfate process.•Complete degradation of DNP is ...obtained using combined HC/Fenton process.•Homogeneous Fenton process is better as compared to Fenton like processes.
In the present work, degradation of 2,4-dinitrophenol (DNP), a persistent organic contaminant with high toxicity and very low biodegradability has been investigated using combination of hydrodynamic cavitation (HC) and chemical/advanced oxidation. The cavitating conditions have been generated using orifice plate as a cavitating device. Initially, the optimization of basic operating parameters have been done by performing experiments over varying inlet pressure (over the range of 3–6bar), temperature (30°C, 35°C and 40°C) and solution pH (over the range of 3–11). Subsequently, combined treatment strategies have been investigated for process intensification of the degradation process. The effect of HC combined with chemical oxidation processes such as hydrogen peroxide (HC/H2O2), ferrous activated persulfate (HC/Na2S2O8/FeSO4) and HC coupled with advanced oxidation processes such as conventional Fenton (HC/FeSO4/H2O2), advanced Fenton (HC/Fe/H2O2) and Fenton-like process (HC/CuO/H2O2) on the extent of degradation of DNP have also been investigated at optimized conditions of pH 4, temperature of 35°C and inlet pressure of 4bar. Kinetic study revealed that degradation of DNP fitted first order kinetics for all the approaches under investigation. Complete degradation with maximum rate of DNP degradation has been observed for the combined HC/Fenton process. The energy consumption analysis for hydrodynamic cavitation based process has been done on the basis of cavitational yield. Degradation intermediates have also been identified and quantified in the current work. The synergistic index calculated for all the combined processes indicates HC/Fenton process is more feasible than the combination of HC with other Fenton like processes.
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•CETP effluent treatment using coupled cavitation, H2O2 and catalytic ozonation.•Numerical estimation of incipient cavitation number and flow rate.•MgO was observed to be more ...efficient than MnO2.•Influence of ̇OH radical scavengers was investigated.•HC coupled with catalytic ozonation offers promise for large scale treatment.
In the current work, chemical oxygen demand (COD) reduction of Common Effluent Treatment Plant (CETP) effluent was investigated using acoustic (AC) or hydrodynamic cavitation (HC) coupled with ozone, O3/H2O2, O3/MnO2 and O3/MgO. AC was based on a dual-stepped ultrasonic horn whereas HC was based on an orifice applied as cavitating device. Maximum COD reduction of 88.66% was obtained for the approach of AC/O3/MgO followed by 85.13%, 67.12%, 56.28% and 52.23% for AC/O3/MnO2, AC/O3/H2O2, AC/O3 and only ozone respectively within 60 min at natural pH of 9. For HC, maximum COD reduction of 88.36% was achieved for HC/O3/MgO followed by 83.11%, 64.77%, 54.61% and 51.12% for HC/O3/MnO2, HC/O3/H2O2, HC/O3 and ozone operated in recirculation mode without HC respectively. The influence of ̇OH radical scavengers as Cl¯, CO32¯ and HCO3¯, and ozone scavenger as S2O32¯ on the efficacy of different approaches has also been demonstrated to establish the controlling mechanisms. The experimental data was fitted to the Generalized Kinetic Model (GKM) considering the formation of intermediates along with the determination of volumetric mass transfer coefficients on the basis of dissolved ozone concentration. The cost estimation for various approaches have also been performed. Overall it has been clearly demonstrated that HC based catalytic ozonation offers promise for treatment of effluents in the CETP.
The study highlights effectiveness of hydrodynamic cavitation (HC) in the degradation of effluents polluted by Brilliant Cresyl Blue (BCB) dye. Optimal process parameters were cavitation number 0.27, ...inlet pressure 1.70 bar, temperature 20 °C and pH 7. The efficiency of HC was investigated in combination with other advanced oxidation processes, including the addition of external oxidants (hydrogen peroxide, ozone, and sodium persulfate) and photooxidation. A detailed investigation of reactive radical species present in the system is also presented. Hybrid processes based on HC revealed the highest synergism. Finally, ultrafast degradation of target oxazine dye (decolorization efficiency of 100%) within the short treatment time of 1 min was developed. The most effective process was a combination of hydrodynamic cavitation and ozonation with a synergistic coefficient of 1.84 and electrical energy per order EEO of 0.03 kWh m−3 order−1. The presented solution is ready to be implemented as technology for industrial practice.
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•Hydrodynamic cavitation aided by ozone (HC/O3) led to ultra-fast degradation of BCB dye.•Superoxide radicals (O2.•-) were the main oxidizing species in the system.•Hydroxyl radicals participated in degradation mechanism.•High synergism between ozonation and cavitation phenomenon.•Ideal, low cost, method for implementation in real industrial practice.
In this study, soy protein isolate (SPI) dispersions (3%, w/v) were treated with hydrodynamic cavitation (HC) with a venturi tube (treatment volume: 2 L) and ultrasonic cavitation (UC) (treatment ...volume: 200 mL and 2 L) under the power of 550 W for 5, 10, 20, and 30 min. The effects of HC and UC treatment on the physicochemical and functional properties of SPI were investigated, and the results were compared to better evaluate the HC effects on food proteins. The results showed that the electrophoretic profile and pH were not affected by UC or HC treatment. The particle size and viscosity of SPI were reduced after UC or HC treatment. Both UC and HC treatment significantly (P < 0.05) increased the surface hydrophobicity. UC treatment at the volume of 2 L did not alter the exposed or total sulfhydryl content; however, UC treatment at the volume of 200 mL and HC treatment altered the exposed sulfhydryl content and decreased the total sulfhydryl content. Moreover, the solubility, emulsifying activity index, emulsion stability index, and foaming capacity were also significantly (P < 0.05) improved; however, foam stability was reduced after UC and HC treatment. Under the conditions investigated in this study, the effect of HC treatment on the physicochemical and functional properties of SPI was more pronounced than that of UC treatment at the volume of 2 L, and was similar to that of UC treatment at the volume of 200 mL. These results suggest that HC could be an effective method to improve the functional properties of food proteins.
•The effects of hydrodynamic and ultrasonic cavitation on soy protein isolate were compared.•The particle size and viscosity were reduced after treatment.•The surface hydrophobicity and solubility were increased after treatment.•Some functional properties were improved after treatment.•The effect of hydrodynamic cavitation was more pronounced than that of ultrasonic cavitation at large volume.
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•Analysis of geometric and operating conditions in terms of evaluation matrices.•Increased biodegradability and COD reduction are observed for wastewater.•Waste sludge pre-treatment ...yields higher methane/energy in anaerobic digestion.•The system is observed to be cost effective and energy positive.
Long treatment times, large quantity of sludge generation, inhibition of micro-organisms and inability to degrade refractory pollutants are common disadvantages of biological treatment processes. Cavitation-based pre-treatment processes can enhance the treatment efficiency of biological treatment including aerobic oxidation and anaerobic digestion. This work presents a critical review on cavitation-based pre-treatment for subsequent biological oxidation process as well as for the treatment and modification of waste sludge for subsequent anaerobic digestion. For wastewater pre-treatment, important metrics to be assessed are COD reduction, and biodegradability index enhancement. In several studies, a BI improvement up to 50–60 % has been observed with cavitation. For sludge pre-treatment, particle size reduction, soluble COD and degree of disintegration (DDCOD) increase, and enhancement of biomethane production potential as the performance metrics have been reviewed. The effect of several process parameters like ultrasound power, hydrodynamic cavitation pressure and geometry, time, and pH are critically reviewed and compared for various studies. Improvements in treatment times, higher enzymatic digestibility, removal of refractory pollutants, and lower inhibition in the biological processes were observed as the key advantages due to the use of cavitation. Optimum cavitation numbers for efficient pre-treatment using hydrodynamic cavitatio lie between 0.05 and 0.15. It is observed that low hydrodynamic pressures are the most advantageous for sludge disintegration and also the process is highly time dependent. Cavitation, especially the hydrodynamic mode, is demonstrated as an economically feasible advanced oxidation-pretreatment for sludge modification and biological oxidation processes leading ultimately to an ‘energy-positive system’. Future studies in this context should mainly focus on the development of continuous flow-pilot scale systems that can be subsequently considered applicable commercially.
The flotation of fine particles less than 50 μm is challenging for the mining industry. By using hydrodynamic cavitation, a significant improvement on the recovery of fine particles has been found. ...This study aims to investigate the effect of hydrodynamic cavitation on the selective flotation of fine particles from detailed mechanism. Our single-bubble flotation results indicated that the bubble-particle collection efficiencies of fine silica particles (D50 = 6 μm and D50 = 16 μm) improved after hydrodynamic cavitation, especially for hydrophobized silica particles. The improved flotation performance of fine particles was investigated from three perspectives: (1) By zeta potential distribution measurements, bubble-frosting on hydrophobic particles was demonstrated after hydrodynamic cavitation. (2) The formation of large aggregates of hydrophobic fine particles after cavitation was revealed by slurry turbidity and particle size measurements, potentially contributing to the improved collision efficiency of the fine particles due to the bridging effect provided by microbubbles. (3) The attachment efficiency between a solid surface and flotation bubbles was enhanced if the surface was covered with hydrodynamic cavitation-generated microbubbles. Compared to the hydrophilic particles, the hydrophobic particles benefited from the hydrodynamic cavitation from the perspectives of bubble frosting, particle-bubble collision efficiency and attachment efficiency. Based on this study, it is expected that the separation efficiency for fine hydrophilic and hydrophobic particles can be improved by hydrodynamic cavitation.
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•HC microbubbles improves the collection efficiency of hydrophobic particles.•Hydrodynamic cavitation covers the hydrophobic particle surfaces with microbubbles.•Cavitation microbubbles help the formation of aggregates with hydrophobic particles.•Surface microbubbles reduce the induction time in bubble-solid attachment.
•Highly effective (100%) and rapid (15 min) degradation of sulfide ions.•Promising treatment technology for effluents from bitumen production.•Synergistic effect of cavitation phenomena with AOPs ...(3-times shortening of treatment).•Pre-treatment method for coupling with other AOPs.
The paper presents the results of investigations on the effectiveness and reaction rate constants of the oxidation of sulfide ions and organic sulfides in real industrial effluents from the production of bitumens (2000 mg S2− L−1) using hydrodynamic and acoustic cavitation. The content of the effluents was analysed in terms carbon disulfide, dimethyl sulfide, and di-tert-butyl disulfide concentration. A possibility of complete oxidation of sulfides by cavitation alone as well as by its combination with external oxidants such as hydrogen peroxide, ozone or peroxone was demonstrated. The oxidation time for the most effective processes is as little as 15 min. Due to the presence of sulfide ions, the effluents from the production of bitumens were oxidized at a strongly alkaline pH. The results of this study reveal the advantage of performing advanced oxidation processes (AOPs) at a basic pH. The effective degradation of sulfide ions enables performance of further degradation of organic contaminants at an acidic pH, ensuring high efficiency of treatment based, for example, on the Fenton reaction without the risk of release of hydrogen sulfide to the atmosphere. The results of this research are applicable to all kinds of caustic effluents for which the lack of possibility of pH adjustment limits their efficient treatment.
•Hydrodynamic cavitation of nematic liquid crystal 5CB in the Stokes flow regime.•The critical Reynolds number of cavitation inception from 2695 to 6596.•Using the Strouhal number to describe the ...unsteady oscillating cavitation flow.•Dynamics characteristics of cavitation are analyzed.
The impact of hydrodynamic cavitation is one of the key factors in the fabrication and application of metal materials. The hydrodynamic cavitation in anisotropic fluids can be much different from common fluids due to the unique fluid dynamics characteristics related to the director field. In this paper, the hydrodynamic cavitation of nematic liquid crystal 5CB flowing around a cylindrical pillar in a microchannel in the Stokes flow regime is studied at various Reynolds numbers and blockage ratios by experiments. Once the Reynolds number rises over a threshold value, the hydrodynamic cavitation of nematic liquid crystal is generated in the stokes flow in the microchannel, which is the unique phenomenon for anisotropic fluids. The critical Reynolds number of cavitation inception decreases with the increase of the blockage ratio. The Strouhal number is induced to describe this unsteady oscillating cavitation flow, while the Strouhal number increases and decreases with the increase of the blockage ratio and Reynolds number, respectively. Dynamics characteristics of the cavitation including cavity volume, oscillation frequency, and pressure difference are analyzed at different Reynolds numbers and blockage ratios by image binarization treatment and Fast Fourier Transformation analysis. The results of this study are useful for the application of microfluidic chips based on nematic liquid crystals and protection of devices in the environment of similar anisotropic fluids.
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•Hydrodynamic cavitation can be promoted with the addition of sodium chloride.•Sodium chloride decreases air solubility in water, increases gas saturation level.•Hydrodynamic cavitation is promoted ...as gas saturation level increases.•Cavitation inception reversibly controlled by changing pH of carbonated water.
Hydrodynamic cavitation is a common natural phenomenon that has positive and negative implications in several fields. In one hand, it is a major cause of corrosion and noise radiation in the marine industry. On the other hand, it is used as an innovative process for enhancing mineral flotation and water disinfection. Therefore, understanding the promotion and prevention mechanisms of hydrodynamic cavitation inception is essential for industrial applications. In this study, a Venturi tube was used as the hydrodynamic cavitation device, and the cavitation inceptions were measured using the sound-detection method. NaCl was shown to promote cavitation inception of water. However, no obvious change was observed for air-saturated NaCl solutions. These results are explained by the increase in air saturation level when salt is added into water. Based on this idea, the cavitation inception can be controlled by modifying the CO2 solubility through changing the pH of carbonated water, a process that was shown to be reversible. These findings are applicable to industrial operations that try to avoid cavitation or those where the generation of bubbles is required.
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