Photocatalytic Removal Of Phenol Research Articles

Modeling of petroleum wastewater treatment by Fe/Zn nanoparticles using the response surface methodology and enhancing the efficiency by scavenger

The petroleum wastewater caused to serious problems in the aqueous and soil environments, therefore treatment of petroleum wastewater has extremely been in the center of attention in recent years. Phenol is one of main petroleum compounds. The photocatalytic removal of phenol from the wastewater by the use of scavenger and nanoparticle is discussed in this research. In this research, Fe/Zn bimetal nanoparticle is synthesized and used by a new and simple method. Based on the results, this nanoparticle has solved the issue of its removal from the water (after the treatment) using its exclusive magnetic property. Using the Hydrogen peroxide as a scavenger has significantly increased the efficiency of the nanoparticle in photocatalytic treatment. The independent parameters studied in this research include the phenol initial concentration, light source power, retention time, pH and the nanocatalysts concentration. The Hydrogen peroxide was used with the constant concentration of 0.01 M. The experiment design was performed by response surface methodology. Based on the results, the removal efficiency was increased by increasing in nanocatalyst concentration, pH, UV source power and retention time. Also removal efficiency decreased by increasing in initial phenol concentration. According to the FESEM result, nanomaterial has dimensions less than 50 nm. The removal efficiency has been obtained as 89% in the optimum condition (pH equal to 5.23, light source power equal to 43.53 w, phenol concentration equal to 50 ppm, Nano concentration equal to 1.57 g/l and the time equal to 58.6 min).

PHOTOCATALYTIC REMOVAL OF PHENOL OVER MESOPOROUS ZnO/TiO2 COMPOSITES

A series of mesoporous ZnO/TiO2 composites were successfully synthesized using cetyltrimethylammonium bromide surfactant. The composites of different Zn:Ti molar ratios (0.5:1, 0.75:1, and 1:1) were prepared by impregnating ZnO onto mesoporous TiO2. XRD results verified co-existence of both anatase TiO2 and hexagonal wurtzite ZnO in the ZnO/TiO2 composites. Based on the Tauc plots, all the composites showed almost the same band gap energy of approximately 3.21 eV. The fourier transform infrared spectroscopy results successful covering of ZnO on the surface of the TiO2 as the hydrophilicity property of TiO2 decreased remarkably with the loading of ZnO in the composites. N2 adsorption-desorption isotherms of the samples exhibited type-IV isotherm with a hysteresis loop. The Barrett-Joyner-Halenda pore size distribution revealed that the average pore size of the composites was around 3.6 nm, indicating the formation of mesopores dominantly in the samples. The photocatalytic removal of phenol over the samples under UV light irradiation after 3 h decreased in the order: ZnO/TiO2 composites > anatase TiO2 (with surfactant) > anatase TiO2 (without surfactant) > ZnO. The composite with Zn:Ti molar ratio of 0.75:1 has achieved the highest photocatalytic activity of 36.5% in the removal of phenol under UV light irradiation for 3 h.

Photocatalytic removal of phenol by ferromagnetic N-TiO2/SiO2/Fe3O4 nanoparticles in presence of visible light irradiation

Photocatalytic removal of phenol by ferromagnetic N-TiO2/SiO2/Fe3O4 nanoparticles in presence of visible light irradiation

ENHANCED ACTIVITY OF C3N4 WITH ADDITION OF ZnO FOR PHOTOCATALYTIC REMOVAL OF PHENOL UNDER VISIBLE LIGHT

Phenol is a stable and hazardous compoundthat is commonly found as an industrial effluent 1. Phenol can be treated by photocatalysis using ZnO as a photocatalyst'' 3. Unfortunately, the use of zinc oxide (ZnO) in photocatalysis is limited due to the photocorrosion effect and poor response to the visible light, Various methods have been reported to improve the performance of ZnO,such as the use of carbon nitride (C3N4) to suppress the photocorrosion and improve the absorption in the visible light regions. It was reported that the ZnO-C3N4could be prepared by mixing the powder ZnO with C3N4that was dispersed in methanol, followed by drying process under nitrogen atmospheres. In the present study, a series of ZnO-C3N4was prepared bya simplermethod, which was impregnationof zinc oxide precursor on the C3N4, followed by calcination process. The effect of zinc to carbon ratio (Zn/C) on the properties and photocatalytic activity was examined.XRD patterns of the samples revealed that as the Zn/C ratio increased, the intensity of diffraction peaks for ZnO also increased but the intensity for C3N4 decreased. All the prepared composite materials have an extended absorption band in the visible light region due to the presence of C3N4, as supported by DR-UV Vis spectra. The prepared ZnO-C3N4 composites were further investigated in the photocatalytic removal of phenol under visible light irradiation for 5 hours. All ZnO-C3N4 samples showed higher activity than the bare ZnO (Figure 1). The ZnO-C3N4 with Zn/C ratio of 1 mol% showed the highest photocatalytic activity for removal of phenol among all the samples. The high activity observed on the ZnO-C3N4 would be due to the role of C3N4 to suppress electron-hole recombination and extend the absorption ofZnO in the visible light region.

Photocatalytic removal of phenol over titanium dioxide- reduced graphene oxide photocatalyst

Titanium dioxide (TiO2) has been one of the most investigated semiconductors due to its high activity for the removal of organic pollutants. In order to improve the efficiency of the TiO2, series of TiO2-reduced graphene oxide (rGO) composites with various loading amounts of graphene oxide (GO), which were 0.5, 1, 3 and 5 wt% were prepared by UV- assisted photocatalytic reduction method. The X-ray diffraction (XRD) patterns and Fourier transform infrared spectroscopy (FTIR) spectra confirmed that all the TiO2-rGO composites samples were successfully synthesized without disrupting the structure of the TiO2. Fluorescence spectroscopy revealed the role of the rGO to reduce the electron-hole recombination on the TiO2, while the transmission electron microscopy-energy dispersive X- ray spectroscopy (TEM-EDS) confirmed the morphology and the presence of both TiO2 and rGO. In the photocatalytic removal of phenol, all the TiO2-rGO composites showed better photocatalytic activities than the TiO2 under UV light irradiation. The activity of the TiO2 was enhanced by more than two times with the addition of the GO with the optimum amount (3 wt%). It was proposed that the good photocatalytic performance obtained on the composites were caused by the successful suppression of electron-hole recombination by the rGO on the TiO2.

Improved photocatalytic activity of anatase titanium dioxide by reduced graphene oxide

Reduced graphene oxide (rGO) has been one of the most investigated carbon based materials due to its great electronic conductivity that make it able to accept and transport electron easily. In order to study the effect of rGO, anatase titanium dioxide-reduced graphene oxide (TiO2-rGO) composite was prepared by UV-assisted photocatalytic reduction method using the anatase TiO2 as a photocatalyst and various different loadings of graphene oxide (GO). The characterizations of the prepared samples were investigated by X-ray diffractometer (XRD), Fourier transform infrared (FTIR), and fluorescence spectroscopies. The XRD patterns and FTIR spectra confirmed that all the TiO2-rGO composites samples were successfully synthesized without disrupting the structure of the anatase TiO2. Fluorescence spectroscopy revealed the role of the rGO to reduce the electron-hole recombination on the anatase TiO2. In the photocatalytic removal of phenol, all the TiO2-rGO composites showed better photocatalytic activities than the bare anatase TiO2 under UV light irradiation. The activity of the anatase TiO2 was enhanced by more than four times with the addition of the GO with the optimum amount (3 wt%). It was proposed that the good photocatalytic performance obtained on the composites were caused by the successful suppression of electron-hole recombination by the rGO on the TiO2.

Photocatalytic removal of phenol from refinery wastewater: Catalytic activity of Cu-doped titanium dioxide

A series of Cu-doped TiO2 catalysts were prepared by a sol–gel method and the effect of various synthesis parameters, including solvent type; solvent/catalyst amount; amount of water; catalyst type/amount; and acid type, on removal of phenol from refinery wastewater under UV-irradiation was investigated. Among the three solvents used, ethanol (En); isopropanol (Iso) and 2(2-Ethoxyethoxy) ethanol (Exy); undoped-TiO2 catalysts prepared with ethanol (En) solvent showed the highest phenol degradation rate even though the surface area of isopropanol is 6 times higher than ethanol. However, for Cu-doped TiO2 catalysts, isopropanol showed the highest photodegradation rate of phenol. Increasing the amount of water increased the surface area of the catalyst accordingly but no clear trend between phenol degradation rate and the amount of water used was observed. In contrast to NaOH, the addition of HCl improved the photodegradation rate of phenol while H2SO4 was twice as effective with respect to the phenol degradation.

Photocatalytic degradation of phenol in water solutions using zno nanoparticles immobilized on glass

Phenol and its derivatives are pollutant compounds that are present in the wastewater of many industries. The objective of this study was to investigate the photocatalytic degradation of phenol in water containing various concentrations of sodium chloride. A laboratory study was conducted to evaluate the performance of UV/ZnO process on the efficiency of phenol removal from saline water with ZnO nanoparticles fixed on glass using UVC radiation. The effects of pH, contact time, sodium chloride concentrations, and the initial concentration of phenol on the photocatalytic removal of phenol were studied. The photocatalytic degradation of phenol showed suitable efficiency under the absence of sodium chloride (100% phenol removal at a concentration of 5 mg/l and during 120 minutes). However, the removal efficiency decreased in the presence of a concentration of 30 g/l of sodium chloride (92.4%). Additionally, phenol photocatalytic degradation efficiency decreased as a result of an increase in the initial concentration of phenol and the efficiency increased as a result of a decrease in pH (pH = 3). The results obtained from this study indicated that ZnO nanoparticles or ultraviolet rays alone cannot remove phenol fully and have a much lower efficiency in comparison with the photocatalytic degradation of phenol. Thus, the photocatalytic degradation process (UV/ZnO) is an effective method of removing phenol from saline water solutions.

Photocatalytic removal of phenol using titanium dioxide deposited on different substrates: Effect of inorganic oxidants

Abstract Photocatalytic degradation of phenol has been investigated using a laboratory reactor and UV-A lamp (BLB) and different commercial catalysts: TiO 2 PC500 fixed on cellulose paper (Ahlstrom paper) and TiO 2 (Degussa P25) on stainless steel or conducting glass. Thin layers of TiO 2 on glass and stainless steel were prepared by electrophoretic deposition. Phenol and by-products were monitored by HPLC system equipped with a phenyl column and PDA detector. The effects of various operating parameters such as initial concentration of phenol (100–500 μmol L −1 ), initial pH (2.0–10.0) and addition of inorganic oxidants (H 2 O 2 , S 2 O 8 2 − ) were evaluated on Ahlstrom paper. The results revealed that the best conditions of phenol removal were 100 μmol L −1 of initial concentration, natural pH (5.0–6.0) and absence of inorganic oxidants when using Ahlstrom paper. Also, analysis of the by-products shows their dependence on initial pH. The comparison of phenol removal efficiency shows that thin layers of TiO 2 P25, deposited on glass, present the best photocatalytic activity. Several experiments performed with the same photocatalyst show that washing layers with pure water several times and drying at low temperature allow reactivation of the catalysts.

Photocatalytic removal of phenol and methylene-blue in aqueous media using TiO2@LDH clay nanocomposites

Herein, we report the formation of a series of nanocomposites composed of LDH structures and TiO2 with anatase crystal phase. The structure of the LDH clay was modulated by the insertion of different di-, tri- or tetravalent cations, such as Zn2+, Cu2+, Al3+, Fe3+ or Ti4+, within the brucite-like sheets. Afterwards, the anatase seeds were deposited onto the LDH clays, obtaining new nanocomposite systems with tailored photocatalytic activity. In this way, the photoresponsive properties of the final nanocomposites were shifted from the UV to the visible range of the solar spectrum. The obtained nanocomposites were tested for the degradation of different organic pollutants, like phenol and methylene blue, under UV and visible light in aqueous media with different pH. The kinetic study showed that the TiO2@LDH nanocomposites are efficient for the phenol (and its intermediary species catechol and hydroquinone) and methylene blue photocatalytic degradation under both UV and Vis light illumination.

Adsorptive and Photocatalytic Removal of Phenol by Layered Niobates Organically Modified Through Intercalation and Silylation

Layered hexaniobate K4Nb6O17 was modified with dodecylammonium ions and octadecyltrimethoxysilane molecules, which were held in the interlayer spaces by electrostatic interactions and covalent attachment to the layers, respectively. Interlayer spacing of the niobate was expanded by incorporation of the bulky organic species. Vapor adsorption isotherms of benzene and water indicated hydrophobic interlayer microenvironments of the organically modified niobates. Both of the modified niobates fairly adsorbed phenol dissolved in water. The photocatalytic activity of hexaniobate allowed the organically modified materials to photocatalytically decompose phenol upon UV irradiation. Decomposition time courses and quantitative analysis of phenol present in the system indicated that the phenol molecules adsorbed on the niobates were preferentially degraded. XRD and IR analyses of the modified niobates indicated that the silylated niobate was more durable than the ion-exchanged sample; the former kept the structure during the photocatalytic process while the latter was partly collapsed.

Palygorskite and SnO2–TiO2 for the photodegradation of phenol

The photocatalytic removal of phenol was studied using palygorskite-SnO2–TiO2 composites (abbreviated as Paly-SnO2–TiO2) under ultraviolet radiation. The photocatalysts were prepared by attachment of SnO2–TiO2 oxides onto the surface of the palygorskite by in situ sol–gel technique. The products were characterized by XRD, TEM and BET measurements. SnO2–TiO2 nanoparticles, with an average diameter of about 10nm, covered the surface of the palygorskite fibers without obvious aggregation. Compared with palygorskite-titania (Paly-TiO2), palygorskite-tin dioxide (Paly-SnO2), and Degussa P25, Paly-SnO2–TiO2 and SnO2–TiO2 exhibited much higher photocatalytic activity. The photodecomposition of phenol was as high as 99.8% within 1.5h. The apparent rate constants (kapp) for Paly-SnO2–TiO2, TiO2, and P25 were measured. Paly-SnO2–TiO2 showed the highest rate constant (0.03435min−1). The chemical oxygen demand (COD) of the phenol solution was reduced from 220.2mg/L to 0.21mg/L, indicating the almost complete decomposition of phenol. Reusability of the photocatalyst was proved.

Continuous flow photocatalytic treatment integrated with separation of titanium dioxide on the removal of phenol in tap water

We studied the continuous flow photocatalytic treatment integrated with separation/reuse of titanium dioxide on the removal of phenol (20 mg l −1) in electrolytes containing tap water. A circulative flow tubular photoreactor and a separation tank were used, where inflow of phenol continuously flowed into a mixing tank (for titanium dioxide suspension) and treated water overflowed from the separation tank. Black light and sunlight were used by turns as the light source on the photocatalytic treatment. Photocatalytic removal of phenol was maximum at the circulative flow rate of 600 ml min −1 and the transmittance of 0.3%. Integration of circulative photocatalytic treatment and titanium dioxide separation and continuous use of titanium dioxide could be performed effectively at low inflow of 10 ml min −1. The titanium dioxide slurry sedimented spontaneously by standing was continuously used for at least 72 h without decreasing the efficiency of the photocatalytic treatment. The used titanium dioxide can be replaced with a fresh one by draw and fill method without interrupting the treatment.

Photocatalytic Removal of Phenol Under UV Irradiation on WO x –TiO2 Prepared by Sol–Gel Method

New WOx–TiO2 photocatalysts were prepared via sol–gel method from tetraisopropyl orthotitanate and WO2. For comparison TiO2 was also prepared by the same method. These photocatalysts were tested for phenol degradation in an aqueous solution under UV irradiation. Experimentally measured OH radicals formation on WOx–TiO2 photocatalysts was quantitatively much higher than on TiO2, what increased their photocatalytic activity towards phenol decomposition. Band gap of the prepared photocatalysts was calculated from the obtained derivatives of UV–Vis/DR spectra and it was observed that Eg decreased with increasing calcination temperature in both, TiO2 and WOx–TiO2. This was caused by the improving crystallinity of anatase phase and formation of rutile, which had a lower value of Eg than anatase. In general the presence of WOx in TiO2 suppressed transformation of anatase to rutile.

Photocatalytic activity of polymer-modified ZnO under visible light irradiation

Photocatalytic removal of phenol, rhodamine B, and methyl orange was studied using the photocatalyst ZnO/poly-(fluorene- co-thiophene) (PFT) under visible light. After 2 h irradiation with three 1 W LED (light-emitting diode) lights, about 40% removal of both phenol and methyl orange was achieved; rhodamine B was completely degraded to rhodamine. Diffuse reflectance spectra showed that the absorbance range of PFT/ZnO was expanded from 387 nm (ZnO) to about 500 nm. Photoluminescent spectra and photoluminescent quantum efficiency indicated that electrons were transferred from PFT to the conduction band of ZnO. Electron spin resonance (ESR) signals of spin-trapped paramagnetic species with 5,5-dimethyl-1-pyrroline- N-oxide (DMPO) evidenced that the OH radicals were indeed formed in the PFT/ZnO system under visible light irradiation. A working mechanism involving excitation of PFT, followed by charge injection into the ZnO conduction band is proposed.

Recombination rate of photogenerated charges versus surface area: Opposing effects of TiO 2 sintering temperature on photocatalytic removal of phenol, anisole, and pyridine in water

The sintering temperature is an important parameter in many TiO 2 synthesis processes. Increasing this temperature (1) reduces the number of defect sites and, accordingly, the rate of electron–hole recombination, which improves photocatalytic rates and (2) decreases particle surface area, which a priori may be expected to reduce photocatalytic rates. We have studied the photocatalytic removal in water of the title probe molecules over a series of Millennium Chemicals TiO 2 prepared at increasing sintering temperatures in the order: PC500, PC105, PC50, and PC10. For phenol and anisole, reaction rates increase with increasing sintering temperature. For pyridine, the trend is opposite for PC500, PC105, and PC50, but PC10 outperforms all three. Therefore, the net effect of sintering temperature depends on the pollutant to be removed even for structurally closely related pollutants and is likely the result of an essentially surface-based reaction mechanism for pyridine versus a near-surface solution-phase mechanism for phenol and anisole. Hypotheses are presented regarding the higher activity of PC10 even for pyridine removal and the differences between phenol and anisole removal rates.