Degradation Of Phenol In Solution Research Articles

Flow effects on phenol degradation and sonoluminescence at different ultrasonic frequencies.

Current literature shows a direct correlation between the sonochemical (SC) process of iodide oxidation and the degradation of phenol solution. This implies phenol degradation occurs primarily via oxidisation at the bubble surface. There is no work at present which considers the effect of fluid flow on the degradation process. In this work, parametric analysis of the degradation of 0.1mM phenol solution and iodide dosimetry under flow conditions was undertaken to determine the effect of flow. Frequencies of 44, 300 and 1000kHz and flow rates of 0, 24, 228 and 626mL/min were applied with variation of power input, air concentration, and surface stabilisation. Phenol degradation was analysed using the 4-aminoantipyrine (4-AAP) method, and sonoluminescence (SL) images were evaluated for 0.1, 20 and 60mM phenol solutions. Flow, at all frequencies under certain conditions, could augment phenol degradation. At 300kHz there was excellent correlation between phenol degradation and dosimetry indicating a SC process, here flow acted to increase bubble transience, fragmentation and radical transfer to solution. At 300kHz, although oxidation is the primary phenol degradation mechanism, it is limited, attributed to degradation intermediates which reduce OH radical availability and bubble collapse intensity. For 44 and 1000kHz there was poor correlation between the two SC processes. At 44kHz (0.01mM), there was little to suggest high levels of intermediate production, therefore it was theorised that under more transient bubble conditions additional pyrolytic degradation occurs inside the bubbles via diffusion/nanodroplet injection mechanisms. At 1000kHz, phenol degradation was maximised above all other systems attributed to increased numbers of active bubbles combined with the nature of the ultrasonic field. SL quenching, by phenol, was reduced in flow systems for the 20 and 60mM phenol solutions. Here, where the standing wave field was reinforced, and bubble localisation increased, flow and the intrinsic properties of phenol acted to reduce coalescence/clustering. Further, at these higher concentrations, and in flow conditions, the accumulation of volatile phenol degradation products inside the bubbles are likely reduced leading to an increase SL.

Persulfate/electrochemical/FeCl2 system for the degradation of phenol adsorbed on granular activated carbon and adsorbent regeneration

A novel method was developed for phenol degradation and the regeneration of phenol-saturated granular activated carbon (GAC) in bench-scale tests. The degree of phenol degradation in solutions was as high as 75.3% when using persulfate/electrochemical/FeCl2 (PS/Electro/Fe) system under optimal conditions (1000 mg/L Na2S2O8 and 500 mg/L FeCl2 at 15 V). Based on these results, the regeneration of phenol-saturated GAC was then examined by the PS/Electro/Fe method. The highest regeneration efficiency of 58.2% was obtained when 30 g phenol-saturated GAC was treated in 1000 mg/L FeCl2 and 2000 mg/L PS at an applied voltage of 22.5 V. The effects of electric voltage and initial PS concentrations on the regeneration efficiency were examined in detail for the PS/Electro/Fe system. Considering the practical application of this method, multiple regenerations and reuse cycles of the phenol-saturated GAC were conducted, affording a regeneration efficiency of more than 40% after 3 cycles in practice.

Iron-doped Alfa-Alumina Applied in the Degradation of Phenol Solutions

Neste trabalho buscou-se avaliar a atividade catalitica de alumina dopada com ferro na degradacao do fenol, pelo processo Fenton heterogeneo, que foi quantificado por dois metodos diferentes, Folin-Ciocalteu e cromatografia liquida de alta eficiencia. A alumina foi caracterizada por difracao de raios-X, espectroscopia de infravermelho, fluorescencia de raios-X e area superficial pelo metodo de BET. Apos os testes cataliticos, foi observado que houve degradacao de 94% do fenol com duas horas de reacao, chegando ao maximo de 99,2% com quatro horas. Esta alumina foi reutilizada por tres vezes para o mesmo processo catalitico, mantendo o percentual de degradacao apos quatro horas de reacao. A estabilidade quimica do material foi avaliada e observou-se que nao ha lixiviacao do ferro.

Photocatalytic degradation of phenol over novel rod shaped Graphene@BiPO4 nanocomposite

Graphene@BiPO4 nanocomposite with unique rod shape morphology of BiPO4 has been successfully fabricated by the simple microwave assisted hydrothermal method. The crucial role of graphene oxide in the growth of rod shaped BiPO4 crystals has been attempted to explain in this article. Graphene oxide acts as a structure-directing and morphology-controlling agent in the nucleation and growth of nanocrystals. The as prepared organic–inorganic hybrid Graphene@BiPO4 nanocomposite photocatalyst was characterized by various techniques i.e. X-ray diffraction, scanning electron microscopy, UV–vis diffuse reflectance spectroscopy, Raman spectroscopy and photoluminescence (PL) spectroscopy. The results were promising and shown enhanced photocatalytic activity than pure BiPO4 for phenol degradation. The effect of graphene loading on the rates of photocatalytic degradation of phenol in solution is investigated. The result shows that the optimum photocatalytic activity of Graphene@BiPO4 composite at 5wt% of graphene under visible light is almost three times higher than pure BiPO4.

Nitrogen-doped graphene for generation and evolution of reactive radicals by metal-free catalysis.

N-Doped graphene (NG) nanomaterials were synthesized by directly annealing graphene oxide (GO) with a novel nitrogen precursor of melamine. A high N-doping level, 8-11 at. %, was achieved at a moderate temperature. The sample of NG-700, obtained at a calcination temperature of 700 °C, showed the highest efficiency in degradation of phenol solutions by metal-free catalytic activation of peroxymonosulfate (PMS). The catalytic activity of the N-doped rGO (NG-700) was about 80 times higher than that of undoped rGO in phenol degradation. Moreover, the activity of NG-700 was 18.5 times higher than that of the most popular metal-based catalyst of nanocrystalline Co3O4 in PMS activation. Theoretical calculations using spin-unrestricted density functional theory (DFT) were carried out to probe the active sites for PMS activation on N-doped graphene. In addition, experimental detection of generated radicals using electron paramagnetic resonance (EPR) and competitive radical reactions was performed to reveal the PMS activation processes and pathways of phenol degradation on nanocarbons. It was observed that both (•)OH and SO4(•-) existed in the oxidation processes and played critical roles for phenol oxidation.

Facile synthesis of Fe-containing metal–organic frameworks as highly efficient catalysts for degradation of phenol at neutral pH and ambient temperature

In this work, MIL-53(Fe) was synthesized using a solvothermal method under static conditions. However, it was interesting to find that another MIL-53 type material, Fe(BDC)(DMF,F), was obtained when stirring conditions were used while keeping the other conditions fixed. The Fe-containing metal–organic frameworks (MOFs) were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), 57Fe Mossbauer spectrometry and thermogravimetric analysis (TGA). By simply increasing the crystallization time under agitation, the morphology of the Fe(BDC)(DMF,F) crystals went through a striking transition from a bulky irregular shape to a rod-like morphology. The catalytic performance of the Fe-MOFs was evaluated in the degradation of phenol solution at near neutral pH at 35 °C. A significantly better catalytic activity was achieved for Fe(BDC)(DMF,F) than for MIL-53(Fe) and NH2-MIL-53(Fe) due to the existence of Fe(II) in its framework. Phenol was almost completely decomposed in 3 hours, and the conversions of hydrogen peroxide and chemical oxygen demand (COD) were 74.1% and 78.7%, respectively.

Macrokinetics and Mechanism of Phenol Solution Degradated by Fe<sup>3+</sup>/Ce<sup>4+</sup> Doped TiO<sub>2</sub> Particles

Fe3+/Ce4+ doped TiO2 particles was prepared and used for degradation of phenol solution, the macrokinetics and mechanism of degradation process was proposed by GC-MS, and Fe3+/Ce4+-doped TiO2 particles before and after treated phenol was also compared by TEM. The experimental results showed that COD degradation reactions in static and dynamic cycle process are in accordance with first-order kinetics from the macro effects, phenol can be oxidized to intermediates, such as isobutyric acid, malonic acid, para-benzoquinone, butenic acid, ethanedioic acid, maleic acid, butanedioic acid, o-dihydroxybenzene, paradioxybenzene and dioxybenzene, indicating that Fe3+/Ce4+-doped TiO2 particles are beneficial to some oxidation formation. Moreover, the shapes of Fe3+/Ce4+-doped TiO2 particles after treated phenol displays aggregated.

Phenol Degradation by UV-Enhanced Catalytic Wet Peroxide Oxidation Process

AbstractIn this study, degradation of phenol solution by the ultraviolet-enhanced catalytic wet peroxide oxidation process (UV-CWPO) were evaluated via COD removal. Six kinds of homogeneous catalysts (Fe

Enhanced photocatalytic activity of ZnO/La2O3 composite modified by potassium for phenol degradation

K-doped ZnO/La2O3 composite photocatalyst was synthesized via facile sol–gel route using glucose as a complexing agent. The concentrations of K and La2O3 were varied, it was found that the formation of ZnO/La2O3 composite mainly lay in the promotional effect of potassium and 10mol% content of K-doping was optimum to obtain ZnO/La2O3 composite. The results showed that, in contrast to pure ZnO and undoped ZnO/La2O3, K-doping greatly changed the microstructure, morphology, optical property and photocatalytic performance of ZnO/La2O3 composite. The photocatalytic activity of K-doped ZnO/La2O3 composite yielded 98.5% degradation of phenol solution after 2.5h visible light irradiation, which was explained by the synergetic effect generated by the introduction of both K and La2O3.

Phenol degradation under visible light irradiation in the continuous system of photocatalysis and sonolysis

The combination of photocatalysis under visible light irradiation and sonolysis in the continuous system has been used to degrade an aqueous solution of phenol. ZnFe2O4/TiO2–GAC was employed as the photocatalysts which were obtained by sol–gel process and characterized by spectroscopic X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray microanalyses (SEM–EDX) and Brunauer–Emmett–Teller sorptometer (BET). It was observed that the rates of phenol degradation were affected by the initial pH value of phenol solution, salt addition, gas supplying and the recycling times of the recovered photocatalyst. The kinetic law for the phenol degradation can be apparently expressed as the first-order with respect to the concentration of phenol. Degradation of phenol solution in the continuous system, i.e., photocatalysis and sonolysis has synergistic effect in comparison with the photocatalytic reaction and sonolysis, respectively.

Estudio de la oxidación fotocatalítica de soluciones fenólicas, aplicando un proceso avanzado de oxidación (H2O2 / UV)

En este trabajo se estudió la degradación de soluciones fenólicas a escala planta piloto, mediante el uso de H2O2/UV (luz solar), utilizando un Colector Parabólico Compuesto (CPC). Se analizó el efecto de variables como pH, concentración de fenol y de peróxido de hidrógeno, tiempo de irradiación, sobre los parámetros ambientales DBO, DQO, COT, y remoción de fenol. Se optimizaron algunas variables para obtener la mayor remoción de fenol, el pH fue de 3.5, relación optima entre agente oxidante y el fenol 130 P/F, el tiempo de degradación del fenol 50 minutos, mientras que para alcanzar la mineralización completa 7 horas. Se obtuvieron remociones de fenol mayores al 96%, remociones en DQO y DBO de 41% y 83.6% respectivamente, la mineralización en términos del porcentaje de remoción de COT fue del 86%. Los resultados obtenidos permiten plantear este estudio como una potencial técnica de tratamiento de residuos orgánicos de laboratorios químicos, por su bajo costo, fácil puesta en marcha y alta degradación de compuestos persistentes.

Effect of Ultrasonic Intensity on the Degradation of Phenol Solution

Effect of ultrasonic intensity on the degradation of phenol solution is investigated by changing the nominal ultrasonic power, ultrasonic frequency and the position of reactor. The actual ultrasonic intensity (I) that reaches reactor is measured by ultrasonic power measuring meter. It can be found that the ultrasonic intensity varies with ultrasonic parameters. With the nominal power input improving from 60 W to 150 W, the ultrasonic intensity rises from 0.21 W•cm-2 to 1.06 W•cm-2 and the degradation rate of phenol solution (η) increases from 21.7% to 43.7%. However, when I reaches the highest value of 1.71 W•cm-2 at the frequency of 100 kHz, η decreases to the lowest value of 21.5%. The ultrasonic intensity distribution is uneven in the ultrasonic bath and η increases with an increase of I in the vertical direction. The ultrasonic degradation of phenol solution is affected by ultrasonic intensity, but η doesn’t definitely increase with an increase of ultrasonic intensity.

Highly Active Heterogeneous Fenton-Like Systems Based on Fe<sub>3</sub>O<sub>4</sub> Nanoparticles

In this work, magnetic nanoscale Fe3O4 particles were synthesized through coprecipitation of Fe(II) and Fe(III) in alkaline media. The structure, composition and properties of the nanoparticles prepared were characterized by transmission electron microscope (TEM), X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS) and vibrating sample magnetometer (VSM). Catalytic efficiency of the Fe3O4 nanoparticles was tested in degradation of phenol solution. At pH 7, the chemical oxygen demand (COD) removal rate reached 70% in 3 hours. The heterogeneous catalyst exhibited efficient catalytic activity close to that of iron homogeneous catalyst but with less than 3% leaching of irons cation. Further, it performed well under much wider pH range (pH 3~7) compared to classic Fenton reagent, providing potential alternative as a novel heterogeneous Fenton catalyst for environmental remediation.

Photocatalytic Degradation of Phenol using Fe-TiO2 by Different Illumination Sources

A Fe-doped titanium dioxide (Fe-TiO2) was prepared using hydrothermal method and used for degradation of phenol from aqueous solution. The samples were characterized by X-ray diffraction (XRD) and showed a presence of both TiO2 and Fe2O3 peaks. The photocatalytic activity of Fe-TiO2 catalyst was evaluated for oxidation of phenol in aqueous solution using different illumination sources. Visible light irradiation from sun, UV light sources with 190 and 390 nm, fluorescence and dark environment were used and found that the degradation of phenol was in the order of 7.8%, 12%, 7.5%, 6.8% and 5% obtained after 24 h, respectively. It was found that the increase in exposure time to UV, the increase in solution temperature and pH have increased the rate of phenol degradation in solution. This rate was best fitted using first order kinetic model with reaction constant of .

Photocatalytic activity enhancing for TiO 2 photocatalyst by doping with La

La doped nanocrystalline TiO 2 photocatalyst was developed by sol-gel method. The prepared La-TiO 2 photocatalysts with anatase phases were characterized by X-ray diffractometry (XRD), UV-Vis absorption spectroscopy, and photoluminescence spectra (PL). The photocatalytic activity was evaluated by the photocatalytic degradation of phenol in solution under sunlight irradiation. The results show that the crystallinity of anatase is improved by La doping. Moreover, La not only suppresses phase transition from anatase to rutile but also exhibits an absorption in the λ≥400 nm range. The photocatalytic activity of La-doped TiO 2 photocatalysts exceeds that of pure TiO 2 photocatalyst prepared by the same method when the molar ratio of La to Ti is kept at 0.3%.

Plasma chemical degradation of phenol in solution by gas–liquid gliding arc discharge

A gas–liquid gliding arc (glidarc) discharge reactor is used to degrade high concentration phenol solution. Phenol solution with 1878 mg L−1 initial chemical oxygen demand (COD) is treated by spraying directly into the plasma zone formed between two electrodes through a gas–liquid two phase atomizing nozzle. A number of parameters such as voltage waveform, solution concentration, electrode material, nature of the carrier gases and the gas–liquid ratio are examined. It is found that the voltage waveform of gas–liquid gliding arc discharge is more irregular than that of gas gliding arc discharge, and the breakdown voltage of gas–liquid gliding arc discharge is lower than that of gas gliding arc discharge. The COD abatement of phenol solution with stainless steel as the electrode material is higher than that with brass and aluminium. The increasing electrode thickness and the increasing gas–liquid ratio and carrier gas such as oxygen can increase the degradation of phenol. The final COD of the solution is 173 mg L−1; either air or oxygen is used as the carrier gas, and the solution treated is acidic. The variation of pH and conductivity and the formation of hydrogen peroxide and ozone are measured. The occurrence of CO2 is detected during the plasma treatment: the maximum concentration is 18 000 ppm. While H2 and NOx are also detected during the plasma phase, p-nitrosophenol (C6H5NO2) and p-nitrophenol (C6H5NO3) are detected in the solution treated.

Use of microporous hollow fibers for improved biodegradation of high-strength phenol solutions

A microporous polypropylene hollow fiber module, which was pre-wetted with ethanol, was fabricated for the degradation of phenol in solution by Pseudomonas putida CCRC14365. Phenol solution was passed through the lumen side of the module and cell medium was flowed across the shell side. The effects of medium pH (6.0–7.8), phenol level (100–2800 mg/L), and added amount of tetrasodium pyrophosphate (TSP) (0–4 g/L), a dispersive agent, on phenol degradation and cell growth were examined. The best degradation efficiency was obtained at pH 7.0. It was shown from SEM images that the biofilm formed on the surface of the fibers became thinner by adding TSP. However, the lag phase was shortened and the degradation was more efficient in the presence of TSP (<1 g/L) at medium phenol level. The degradation ability of high-strength phenol (>1000 mg/L) by Pseudomonas putida in the present hollow fiber module was enhanced in comparison with those using freely suspended and Ca-alginate bead-immobilized cells, where substrate inhibition started to occur at relatively low phenol levels (<800 mg/L). A thicker biofilm formed on the outer surface of the fibers played a positive and remarkable role on improved degradation of high-strength phenol solutions.