Ultrasound assisted catalytic wet peroxide oxidation of phenol: kinetics and intraparticle diffusion effects

Sonocatalytic treatment of phosphonate containing industrial wastewater intensified using combined oxidation approaches

Treatment of actual industrial wastewater is a challenging task and has not been investigated using the cavitation-based approaches significantly. In the present work, sonocatalytic degradation (catalysts as CuO and TiO₂) of phosphonate based industrial wastewater, procured from a local company, has been studied in terms of COD reduction under optimized conditions (established using initial studies involving only ultrasound) of pH as 3.2, the temperature of 32 ± 2 °C and 120 min as treatment time. The combination of ultrasound with H₂O₂ and ozone in different approaches has been investigated for maximizing the COD reduction. The optimum set of operating conditions for the sonocatalytic degradation were established as power dissipation of 90 W and catalyst loading as 0.75 g/L for CuO and 0.5 g/L for TiO₂. Use of only ultrasound resulted in COD reduction of 37.2% whereas the combination of US with different approaches resulted in higher extents of COD reduction. The combined operation of US + H₂O₂ + O₃, US + O₃ + H₂O₂ + CuO, and US + O₃ + H₂O₂ + TiO₂ resulted in the extent of COD reduction as 91.5%, 93.8%, and 95.8% respectively. Overall, it has been clearly established that maximum COD reduction is obtained for the combined operation of sonocatalysis (catalyst as TiO₂) with ozone and H₂O₂.

Recyclable ferromagnetic chitosan nanozyme for decomposing phenol

Decomposing phenol and phenolic compounds to purify the environment is a focus of social attention. The use of ferromagnetic nanoparticles (MNP) to degrade phenol and phenolic compounds possesses many advantages and has received extensive attention. However, the unsatisfied catalyst activity and stability of MNP hamper its industrial applications. To improve MNP's properties, a ferromagnetic chitosan nanozyme (MNP@CTS) was synthesized via an improved hydrothermal method and molecular self-assembly technology. Its particle size was 11.76 nm, polydispersity index (PDI) was 0.073, surface zeta potential was 40.34 mV, saturation magnetization value was 35.28 emu g^-1 and coercivity value was 17.56 Oe. The catalytic condition was extensively optimized among a range of pH and temperature, as well as initial concentrations of the substrate and H₂O₂, and MNP@CTS removed over 95% phenol from an aqueous solution within 5 h under the optimum conditions. Moreover, MNP@CTS was stable and could be regenerated for reuse for at least ten rounds. Thus, our findings open up a wide spectrum and lay a foundation of environmental friendly applications of MNP@CTS, showing several attractive features, such as easy preparation, low cost, excellent catalytic activity, good stability and reusability.

Synthesis and application of pillared clay heterogeneous catalysts for wastewater treatment: a review

The use of pillared interlayered clays (PILCs) as heterogenous catalysts in wastewater treatment technologies, particularly advanced oxidation processes (AOPs), is gaining popularity for the treatment of refractory wastewater effluents.

Rapid degradation of phenol by ultrasound-dispersed nano-metallic particles (NMPs) in the presence of hydrogen peroxide: A possible mechanism for phenol degradation in water

The present study was carried out to investigate the degradation of phenol by ultrasonically dispersed nano-metallic particles (NMPs) in an aqueous solution of phenol. Leaching liquor from automobile shredder residue (ASR) was used to obtain the NMPs. The prepared NMPs were analyzed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and by X-ray diffraction (XRD). The SEM images show that the diameters of the NMPs were less than 50 nm. An SEM-EDX elemental analysis reveals that Fe was the most commonly found element (weight %) in the NMPs. The FTIR and XRD peaks indicate the presence of metals oxides on the surfaces of the NMPs. The results of the XPS analysis indicate that various elements (e.g., C, O, Zn, Cu, Mn, Fe) are present on the surfaces of the NMPs. The effects of the NMP dose, the initial solution pH, and of different concentrations of phenol and H2O2 on the phenol degradation characteristics were evaluated. The results of this study demonstrate that phenol degradation can be improved by increasing the amount of NMPs, whereas it is reduced with an increase in the phenol concentration. The degradation of phenol by ultrasonically dispersed NMPs followed the pseudo-first-order kinetics. The probable mechanism of phenol degradation by ultrasonically dispersed NMPs was the oxidation of phenol caused by the hydroxyl radicals produced during the reaction between H2O2 and the NMPs during the ultrasonication process.

Ultrasound promoted catalytic liquid-phase dehydrogenation of isopropanol for Isopropanol-Acetone-Hydrogen chemical heat pump

The apparent kinetic of the ultrasound assisted liquid-phase dehydrogenation of isopropanol over Raney nickel catalyst was determined in the temperature range of 346-353 K. Comparison of the effects of ultrasound and mechanical agitation on the isopropanol dehydrogenation was investigated. The ultrasound assisted dehydrogenation rate was significantly improved when relatively high power density was used. Moreover, the Isopropanol-Acetone-Hydrogen chemical heat pump (IAH-CHP) with ultrasound irradiation, in which the endothermic reaction is exposure to ultrasound, was proposed. A mathematical model was established to evaluate its energy performance in term of the coefficient of performance (COP) and the exergy efficiency, into which the apparent kinetic obtained in this work was incorporated. The operating performances between IAH-CHP with ultrasound and mechanical agitation were compared. The results indicated that the superiority of the IAH-CHP system with ultrasound was present even if more than 50% of the power of the ultrasound equipment was lost.

Comparative kinetic analysis of silent and ultrasound-assisted catalytic wet peroxide oxidation of phenol

The kinetic study of silent and ultrasound-assisted catalytic wet peroxide oxidation of phenol in water was performed to qualitatively assess the effect of ultrasound on the process kinetics. Various kinetic parameters such as the apparent kinetic rate constants, the surface utilization coefficient and activation energy of phenol oxidation over RuI(3) catalyst were investigated. Comparative analysis revealed that the use of ultrasound irradiation reduced the energy barrier of the reaction but had no impact on the reaction pathway. The activation energy for the oxidation of phenol over RuI(3) catalyst in the presence of ultrasound was found to be 13kJmol(-1), which was four times smaller in comparison to the silent oxidation process (57kJmol(-1)). Finally, 'figures-of-merit' was utilized to assess different experimental strategies such as sonolysis alone, H(2)O(2)-enhanced sonolysis and sono-catalytic oxidation of phenol in order to estimate the electric energy consumption based on the kinetic rate constants of the oxidation process.

P-chlorophenol wastewater treatment by microwave-enhanced catalytic wet peroxide oxidation

A microwave-enhanced catalytic wet peroxide oxidation (MW-CWPO) technology was investigated to treat a high concentration of p-chlorophenol wastewater under a mild condition. The MW-CWPO experiments were carried out in a microwave autoclave using copper(II) oxide (CuO)-loaded active carbon as a catalyst. The p-chlorophenol was directly ring-opened within 5 minutes at 343 K and 0.3 MPa and then mineralized to carbon dioxide and water. More than 90% of the total organic carbon was removed within 15 minutes. The reaction activation energy (Ea) of hydrogen peroxide (H2O2) decomposition was decreased from 47.7 to 43.1 kJ/mol under microwave irradiation. The H2O2 catalytic decomposition was fitted to a second-order reaction under microwave irradiation, while it followed a first-order reaction without microwave irradiation. The experimental results indicate that the MW-CWPO method has significant potential applications for a high concentration of p-chlorophenol wastewater.

Degradation of C.I. Acid Orange 7 by ultrasound enhanced heterogeneous Fenton-like process

The effect of ultrasonic power density, goethite addition, hydrogen peroxide concentration, initial pH, hydroxyl radical scavenger, and initial dye concentration on the decolorization of C.I. Acid Orange 7 by ultrasound/goethite/H(2)O(2) process was investigated. The results showed that the decolorization rate increased with power density, goethite addition, and hydrogen peroxide concentration, but decreased with the increase of initial dye concentration. The ultrasonic power density, goethite addition, and initial dye concentration have little effect on decolorization efficiency after 30 min reaction, while the increase of hydrogen peroxide concentration results in the increase of decolorization efficiency. There existed an optimal initial pH to achieve the highest decololrization rate and decolorization efficiency. The presence of hydroxyl radical scavenger would inhibit the decolorization reaction. Only less than half of total organic carbon (TOC) was removed after 90 min reaction, indicating more aggressive conditions are required to achieve the complete mineralization than those employed to simply break the chromophore group.

Integrated heterogeneous sono-photo Fenton processes for the degradation of phenolic aqueous solutions

The removal of organic compounds from aqueous solutions has been tackled by a novel integrated heterogeneous system. The efficacy of the different systems has been assessed using Fenton-like processes (H2O2/Fe2O3-SBA-15) and phenol as model pollutant. Sono- and photo-Fenton processes separately applied as well as combined systems were studied in order to evaluate of possible beneficial effects on the use of coupled systems. The sequential system evidences an enhancement in terms of phenol and TOC conversions compared to the ultrasound or UV-light irradiation processes. A total phenol degradation and ca. 90% TOC reduction are achieved by sequentially ultrasound followed by UV-visible light irradiation. These effects are ascribed cavitation effect of ultrasound producing a reduction of particle size that provides a higher amount of available active sites due to an increased surface area for the subsequent photo-Fenton system. These encouraging results open new paths for the existing oxidation technologies for potable water and wastewater treatment.

Decomposing phenol by the hidden talent of ferromagnetic nanoparticles

Researches on modified Fenton reactions applied in phenol degradation have been focused on reducing secondary pollution and enhancing catalytic efficiency. Newly developed methods utilizing carriers, such as Resin and Nafion, to immobilize Fe(2+) could avoid iron ion leakage. However, the requirement of high temperature and the limited reaction efficiency still restrained them from broad application. Based on a recently discovered "hidden talent" of ferromagnetic nanoparticles (MNPs), we established a MNP-catalyzed phenol removal assay, which could overcome these limitations. Our results showed that the MNPs removed over 85% phenol from aqueous solution within 3h even at 16 °C. The catalytic condition was extensively optimized among a range of pH, temperature as well as initial concentration of phenol and H(2)O(2). TOC and GC/MS analysis revealed that about 30% phenol was mineralized while the rest became small molecular organic acids. Moreover the MNPs were thermo-stable and could be regenerated for at least five rounds. Thus, our findings open up a wide spectrum of environmental friendly applications of MNPs showing several attractive features, such as easy preparation, low cost, thermo-stability and reusability.