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•High synergism between AOPs and hydrodynamic cavitation.•Significant lowering of treatment costs.•Hybrid technologies for water and wastewater treatment.•Effective activation of ...oxidants for radicals formation.•Sustainable solutions for environmental protection.
High-performance water treatment systems based on cavitational processes have received an increasing interest of scientific community in the past few decades. Numerous studies indicated the advantageous application of hydrodynamic cavitation as an alternative, reagent-free treatment method of various pollutants in water. Both approaches were proved as an effective method to achieve mineralization of many organic contaminants as well as a disinfection method, which is able to eliminate pathogenic microorganisms. This makes cavitation-based methods a promising candidate implemented in a post-treatment stage of water treatment facilities. Nowadays, hybrid methods based on combination of cavitation with advanced oxidation processes (AOPs), possessing enhanced oxidation capacity were proposed. Compared to the individual utilization of cavitation and AOPs (e.g., O3, H2O2, Fenton’s process), hybrid processes are capable to degrade even highly persistent contaminants and shorten the operation time reducing the overall consumption of energy and oxidants. The improved performance of hybrid methods is attributed to the synergistic effect occurring between integrated technologies, which is expressed by the synergistic index. In this paper, recent reports focusing on coupling of cavitation and AOPs were reviewed to reveal major principles and mechanisms governing the synergistic effect. The review discusses the effect of process parameters (oxidant type, pH, hydraulic and ultrasonic properties, Kow) on the oxidation effectiveness. Comparative analysis was provided in order to highlight the advantages and limits laying behind the discussed methods. The analysis of the economic feasibility was performed to assess the potential applicability of hybrid techniques in large-scale wastewater treatment.
The main aim of the present investigation was the treatment of ibuprofen (IBP)-polluted aquatic phase using a novel oxygen-permeable cathode (OPC)-equipped electrochemical process (ECP) integrated ...with ultrasound (US). According to kinetic modeling, the decomposition rate of IBP by the integrated process was 3.2 × 10−2 min−1 which was significant in comparison with the OPC-equipped ECP (1.4 × 10−2 min−1) and US alone (2.4 × 10−3 min−1). Increasing the current resulted in the enhanced generation of H2O2 and consequently, improved the degradation of IBP in the solution. Excessive concentrations of Na2SO4 as supporting electrolyte led to no significant enhancement in the reactor efficiency. At initial IBP concentration of 1 mg L−1, complete removal of IBP with reaction rate of 1.7 × 10−1 min−1 was happened within a short reaction time of 30 min. The pulse mode of US led to more than 10% increase in the removal efficiency compared with the normal mode. The presence of scavenging compound of methanol caused the highest drop in the efficiency of the integrated treatment process, indicating the substantial role of free hydroxyl radicals in the degradation of IBP. Intermediate byproducts generated in the solution during the decomposition were also identified and interpreted.
•A new integration of electrochemical process with ultrasound for degradation of ibuprofen.•Synthesis of a novel oxygen-permeable cathode for electro-synthesis of hydrogen peroxide.•Synergistic degradation of ibuprofen by the integrated process.
•Synthesis of ZnO and PrxZn1−xO samples by sonochemical method.•Sonocatalytic degradation of a textile dye by PrxZn1−O nanoparticles.•Characterization of the synthesised nanomaterials by XRD, FT-IR, ...SEM, TEM and XPS.
Undoped and Pr-doped ZnO nanoparticles were prepared using a simple sonochemical method, and their sonocatalytic activity was investigated toward degradation of Acid Red 17 (AR17) under ultrasonic (US) irradiation. Synthesized nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) techniques. The extent of sonocatalytic degradation was higher compared with sonolysis alone. The decolorization efficiency of sonolysis alone, sonocatalysis with undoped ZnO and 5% Pr-doped ZnO was 24%, 46% and 100% within reaction time of 70min, respectively. Sonocatalytic degradation of AR17 increased with increasing the amount of dopant and catalyst dosage and decreasing initial dye concentration. Natural pH was favored the sonocatalytic degradation of AR17. With the addition of chloride, carbonate and sulfate as radical scavengers, the decolorization efficiency was decreased from 100% to 65%, 71% and 89% at the reaction time of 70min, respectively, indicating that the controlling mechanism of sonochemical degradation of AR17 is the free radicals (not pyrolysis). The addition of peroxydisulfate and hydrogen peroxide as enhancer improved the degradation efficiency from 79% to 85% and 93% at the reaction time of 50min, respectively. The result showed good reusability of the synthesized sonocatalyst.
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In the present work, ultrasonically facilitated adsorption (UFA) of a cationic dye Basic Red 46 (BR46) was examined using cellulosic nanostructures obtained from broom and cooler ...straw. Although the exclusive application of the nanostructured broom resulted in the 43.51% adsorption of BR46, the UFA process gave rise to the substantial removal efficiency of about 93%. In the case of the nanostructured straw, the efficiency was increased from 36.9% to 55.7%. The UFA process for both adsorbents reached the equilibrium within 60 min which was shorter than the time for the only adsorption. According to the values of the mean free energy (E), the decolorization via the UFA process applying broom (15.81 kJ/mol) and straw (11.18 kJ/mol) nanostructures was occurred chemically. An insignificant loss in the adsorption capacity of both adsorbents was observed after three regeneration tests by means of 0.05 M hydrochloric acid, indicating the good reusability potential of the as-synthesized cellulosic nanostructures.
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•Tylosin (TYL) was degraded by low-frequency ultrasound irradiation.•The addition of WS2@CeO2 synergistically was enhanced degradation of TYL.•Intercalation of 15 wt% WS2 was ...possessed the highest sonocatalytic activity.•The degradation efficiency had reached 75.6% under the best experimental condition.
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.
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 the present investigation, the treatment of amoxicillin (AMX)-polluted water by the activated persulfate (PS) was considered. As a novel research, continuously electro-generated magnetite (Fe3O4) ...nanoparticles (CEMNPs) were utilized as the activator of PS in an electrochemical medium. The PS/CEMNPs displayed a remarkable enhancement in the decomposition of AMX molecules up to 72.6% compared with lonely PS (24.8%) and CEMNPs (13.4%). On the basis of pseudo-first order reaction rate constants, the synergy percent of about 70% was achieved due to the combination of PS with CEMNPs. The adverse influence of free radical-scavenging compounds on the efficiency of the PS/CEMNPs process was in the following order: carbonate < chloride < tert-butyl alcohol < ethanol. Overall, these results proved the main role of free radical species in degrading AMX. The implementation of ultrasound (US) enhanced the performance of the PS/CEMNPs process. Nevertheless, the highest degradation efficiency of about 94% was achieved when UV254 lamp was joined the PS/CEMNPs system. Under UV254 and US irradiation, the results showed significant potential of the PS/CEMNPs process for degrading AMX antibiotic and generating low toxic effluent based on the activated sludge inhibition test. However, more time is needed to achieve the acceptable mineralization.
•Continuously electro-generated magnetite nanoparticles were used for activating persulfate.•Activated persulfate was successfully utilized for treating amoxicillin-polluted water.•Both UV254 and ultrasound enhanced the activated persulfate in terms of amoxicillin decomposition.•Reduced toxicity of the treated solutions based on the activated sludge inhibition test results.
Nano-layered double hydroxide (NLDH) decorated with Fe and Cu was applied as a novel heterogeneous catalyst for catalytic degradation of gentamicin by the electro-Fenton (EF) process. The EF process ...was equipped with graphite plate under aeration to electrochemically generate hydrogen peroxide in the solution. The characterization analyses confirmed the suitable structure of as-synthesized Cu-Fe-NLDH to be acted as catalyst for treating the target pollutant. The comparative study showed the highest removal efficiency of 91.3% when the Cu-Fe-NLDH-equipped EF process was applied in comparison with the Fenton (50%) and the electro-oxidation alone (25.6%). The acidic pHs favored the degradation of gentamicin. Increasing the current resulted in the enhanced degradation of gentamicin, while the excessive electrolyte concentration (0.1 mol/L) and catalyst dosage (1.5 g/L) led to the tangible drop in the reactor performance. At a specified reaction time, the injection of O3 gas enhanced the efficiency of the Cu-Fe-NLDH-equipped EF process. The presence of ethanol led to more suppressing effect than benzoquinone, indicating the dominant role of OH radical in the degradation of gentamicin compared with other free radical species such as O2- radical. Only 10% drop in the degradation efficiency of gentamicin was observed within 10 operational runs. The mineralization efficiency of about 77% was achieved after 300 min in terms of chemical oxygen demand (COD) removal. The intermediate byproducts generated during the destructive removal of gentamicin were also identified.
Heterogeneous electro-Fenton process using Cu-Fe-NLDH for degradation of gentamicin. Display omitted
•Preparation of Cu-Fe-NLDH using facile hydrothermal method.•Degradation of Gentamicin through electro-Fenton process using Cu-Fe-NLDH catalyst.•Study of catalytic activity of Cu-Fe-NLDH under different operational conditions.•Reusability of Cu-Fe-NLDH catalyst over ten repeated runs.•In situ generation of H2O2 and its conversion to .•OH radicals over Cu-Fe-NLDH.
ZnO nanostructures were synthesized and immobilized on biosilica, a microscopic siliceous material with unique porous structure, in order to increase their catalytic activity and reusability ...potential for removing azo dye molecules from aqueous phase via sonocatalysis. The ZnO–biosilica nanocomposite was more efficient than that of pure ZnO to adsorb the light irradiation generated during the cavitation, producing the higher amounts of OH radicals for the degradation of azo dye molecules. Display omitted
•Synthesis and immobilization of ZnO nanostructures on the biosilica surface.•Characterization of the nanocomposite by FE-SEM, TEM and XRD analysis.•Application of ZnO–biosilica in sonocatalytic removal of an organic dye.•Enhanced sonocatalysis of the dye due to the application of biosilica as support.
In the present study, a porous clay-like support with unique characteristics was used for the synthesis and immobilization of ZnO nanostructures to be used as sonocatalyst for the sonocatalytic decolorization of methylene blue (MB) dye in the aqueous phase. As a result, the sonocatalytic activity of ZnO–biosilica nanocomposite (77.8%) was higher than that of pure ZnO nanostructures (53.6%). Increasing the initial pH from 3 to 10 led to increasing the color removal from 41.8% to 88.2%, respectively. Increasing the sonocatalyst dosage from 0.5 to 2.5g/L resulted in increasing the color removal, while further increase up to 3g/L caused an obvious drop in the color removal. The sonocatalysis of MB dye over ZnO–biosilica nanocomposite was temperature-dependent. The presence of methanol produced the most adverse effect on the sonocatalysis of MB dye. The addition of chloride and carbonate ions had a negligible effect on the sonocatalysis, while the addition of persulfate ion led to increasing the color removal from 77.8% to 99.4% during 90min. The reusability test exhibited a 15% drop in the color removal (%) within three consecutive experimental runs. A mineralization efficiency of 63.2% was obtained within 4h.
Treatment of a saline petrochemical wastewater with BOD5/COD ratio of less than 0.1 was investigated using a consortium consisted of three isolated salt-tolerant bacteria namely, Kocuria turfanesis, ...Halomonas alkaliphila and Pseudomonas balearica. Selected bacteria were isolated from petrochemical wastewater containing mineral salt mediums of 3% salinity. A lab-scale activated sludge bioreactor was used for startup in batch mode operation and after obtaining the MLSS concentration of about 3000 mg/L, the operation was changed to continuous flow mode to determine the biokinetic coefficients under different organic loading rates of 0.33–1.21 kg CODm−3 d−1. The COD removal efficiency of 78.7%–61.5% was observed for treatment of real saline wastewater with a decreasing trend along with increasing the organic loading rate. In addition, results of kinetic investigation demonstrated that the yield(Y), endogenous decay coefficient (kd), maximum reaction rate (Kmax), maximum specific growth rate (μmax) and saturation constant (Ks) were 0.54 mg VSS mg COD−1, 0.014 day−1, 1.23 day−1, 0.66 day−1, and 1315 mg L−1, respectively.
•A saline and recalcitrant petrochemical wastewater was fully characterized and subjected to biological treatment.•Three salt-tolerant bacteria including Kocuria turfanesis, Halomonas alkaliphila and Pseudomonas balearica were isolated.•The biokinetic coefficients were studied under steady state conditions.•COD Removal ranged between 61 and 78% for organic loading rates of 0.33–1.21 kg/COD/m3 d.
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