Search

Globular NiFe2O4 nanoparticles have been synthesized by a simple sol–gel method. The structural, morphological, and optical properties of the material have been thoroughly characterized by means of X-ray diffraction, scanning electron microscopy, Fourier transformed infrared and diffuse reflectance spectroscopy, specific surface area, and porosity analysis. Finally, NiFe2O4 has been tested for the photocatalytic degradation of naproxen, a non-steroidal anti-inflammatory drug widely present in water effluents, under natural solar light irradiation and under several experimental conditions. In particular, the beneficial effect of small H2O2 amounts added to the photocatalytic suspension has been highlighted. The kinetic model reveals that under solar irradiation, 85% of naproxen could be degraded in 60 min upon the addition of H2O2, while 65% degradation could be achieved in its absence. Results highlight that NiFe2O4 could be an efficient and promising material for photocatalytic water remediation. [ABSTRACT FROM AUTHOR]

Adsorption and photocatalytic decolourisation of AR14 in aqueous solution was investigated using α-Fe2O3, α-Fe2O3/S and α-Fe2O3/CdS in dark and under UV irradiation, respectively. The synthesis of alpha iron oxide nanoparticles and combining heteroatoms in its matrix were performed by a simple co-precipitation method. Samples were characterised by XRD, Raman and pHPZC. The dye adsorption on the catalysts' surfaces showed a strong dependence on the pH, and the adsorption played the main role in the photocatalytic reaction in acidic medium. The pseudo first order kinetic model was found to be the best fit for the adsorption of AR14 by the three catalysts (R2 > 0.99) and is in good agreement with a chemisorption mechanism. The plot of intra-particle diffusion model showed a three-stage adsorption process which suggests that more than one process affects the AR14 adsorption. α-Fe2O3/S and α-Fe2O3/CdS nanoparticles had significant enhancement on the decolourisation of AR14 compared to the bulk material. A rate removal of 78%, 94% and 98% of the AR14 was recorded at pH = 3 under UV irradiation for α-Fe2O3, α-Fe2O3/S and α-Fe2O3/CdS respectively. The decolourisation was strongly enhanced in the presence of H2O2 leading to Fenton-like process. Added H2O2 competes with AR14 for the powder surface sites and reduces its adsorption on the catalysts' surfaces. The addition of propanol-2 as a radical scavenger confirms that •OH radicals are the main species responsible for the decolourisation of AR14 inα-Fe2O3/H2O2 system. Fenton-like process provides more selective oxidation for AR14 that have a higher affinity for the iron oxide surface and also for the modified iron oxide surface. [ABSTRACT FROM AUTHOR]

In this study, several photocatalytic degradation systems were investigated using 2,6-dimethylphenol (2,6-DMP) as a model compound. Highly reactive species are formed in four systems, Fe(III), TiO2, TiO2/H2O2 and TiO2/Fe(III) where complete degradation of 2,6-DMP was achieved under UV radiation. Photodegradation of the 2,6-DMP has been described by pseudo-first order kinetic model in the presence of TiO2. In UV/TiO2–H2O2 system, the addition of H2O2 in the TiO2 suspension improves the degradation rate of 2,6-DMP from 70% to 100% for a H2O2 concentration of 10−2 M in 3 h. In homogeneous system, HO• and Fe2+ can be generated by the irradiation of Fe(III) solution. The speciation of Fe(III) obtained from Visual MINTEQ soft showed the formation of several species and Fe(OH)2+ were the most predominant and active species in a pH range of 2.5–3.5. At a low concentration of TiO2 (30 mg L−1), an important positive effect due to the iron addition has been shown in TiO2/Fe(III) system, the entrance of metallic ions at different concentrations enhanced the photocatalytic activity of TiO2. A degradation percentage of 90% was achieved in the UV/TiO2–Fe(III) system under optimal conditions against 57% in UV/TiO2 system. Strong synergistic effect was observed in the UV/TiO2–H2O2 binary system. On the basis of literature, a pathway for 2,6-DMP degradation was proposed. The mechanism of degradation of the 2,6-DMP did not involve only HO• radicals, an interaction of Fe(III) in the excited state with 2,6-DMP occurred giving rise to the formation of 2,6-dimethylphenoxyl radical. [ABSTRACT FROM AUTHOR]

In this study, we have applied Fe(III)-bi-carboxylic acid solutions containing citrate and oxalate ligands to degrade 3-méthylphénol (3MP) in aqueous solutions both under UV and sunlight. Under irradiation at 365 nm, the photodegradation of 3MP is markedly better in the presence of the Fe(III)Ox complex than in the Fe(III)Cit complex this fact is explained by an excess of H2O2 and Fe(II) generated by Fe(III)Ox photolysis creating the Fenton process. We mixtures were realized by varying the composition of the Fe(III)Cit and Fe(III)Ox in order to see the additives of the degradation efficiency of the pollutant. The results show that the addition of Fe(III)Ox to the Fe(III)Cit system evidently augmented the photodegradation rate at pH = 5.5. The Fe(III)Ox/Fe(III)Cit ratio is optimized at [Fe(III)Ox] (0.15/0.15)/[Fe(III)Cit] (0.15/0.6). Synergistic effect in the Fe(III)Ox/Fe(III)Cit binary system was confirmed. The addition of tertiobutanol (T-buOH) noticeably inhibited the photodegradation, indicating the involvement of •OH in the process. To verify the feasibility of photochemical processes in the environment, tests on the photodegradation of 3MP were performed under natural irradiation. The degradation was improved under excitation by sunlight in the presence of Fe(III)-bi-carboxylic acid solutions containing citrate and oxalate ligands. These results are very encouraging for the application of this system for the treatment of organic pollutants in aqueous solution. [ABSTRACT FROM AUTHOR]

This study aims to find a green method for the degradation of organic pollutants in water treatment. We found that chemical oxidation is an effective process in the treatment of an aqueous solution contaminated by ibuprofen (IBP). To demonstrate the application of the modified Fenton-like process under neutral pH conditions, gallic acid (GA) was used as a complexing agent to solubilize iron in a neutral aqueous solution. Our results show that 90.9% complexation was obtained by FeIII:GA ratio of 1:2 and stability constant of logß = 11.66 at pH 7. The catalytic activation of the FeIII-GA complex was initiated by the addition of 5 mM of hydrogen peroxide (H2O2) to the neutral medium. The reduction of FeIII was instantaneous and consequently, the degradation of IBP was achieved by the formation of the hydroxyl radicals (•OH) generated during the Fentonlike reaction. All experiments were performed at natural conditions of temperature with an initial IBP concentration of 0.05 and 0.1 mM of FeIII-GA complex at pH 7. The effect of solution pH, temperature, dosage of H2O2, dosage of IBP, and dosage of FeIII-GA complex on the degradation efficiency was also studied. An important degradation was obtained by choosing the initial doses of 5 mM H2O2 and 0.1 mM of the FeIII-GA complex. IBP oxidation rates are found to be directly proportional to the increase of environmental temperature. The total organic carbon experiments showed mineralization of 88.81% of the organic carbon of IBP after 24 h of treatment in the presence of FeIII-GA complex. This work enriches academic knowledge on the feasibility of degrading IBP based on the organic iron complex as a possible green technolog y. [ABSTRACT FROM AUTHOR]

Zinc oxide ZnO nanoparticles synthesized by sol-gel method and commercial titanium dioxide TiO2 were studied in the present work. The structural properties of the ZnO and TiO2 nanoparticles were determined by Fourier transform infrared (FTIR), X-ray diffraction (XRD) and Raman spectra techniques (RS). The average crystallite sizes were calculated by using the powder X-ray and were found to be 48 nm and 20 nm and the specific surface areas were about 1047 m² g-1 and 381 m² g-1 for ZnO and TiO2, respectively. The FTIR and Raman spectroscopy results have shown high purity of the ZnO and TiO2 samples and they are consistent with the one obtained from XRD. The ZnO and TiO2 nanoparticles were used as catalysts for the elimination of an azo dye, Mordant Violet 5 (MV5), in aqueous solution, by an advanced oxidation process which is heterogeneous photocatalysis. Synthesized ZnO was more efficient than commercial TiO2 to degrade MV5 under UV irradiation. The adsorption of MV5 on TiO2 and ZnO was found favorable by the Langmuir approach. The MV5 adsorption constant on TiO2 was higher than that obtained in the case of ZnO. The photocatalytic reaction of MV5 in presence of each catalyst was investigated at different concentration of the dye and at different conditions of pH. The solar radiation of MV5 in the presence of each catalyst was also tested. [ABSTRACT FROM AUTHOR]

In this study we demonstrate the efficiency of a natural mineral as a photocalyst. This natural mineral was provided from the iron ore deposit from Chaabet-El-Ballout which is located in North-East of Algeria. The characterization analysis of the mineral by the Energy-dispersive X-ray spectroscopy (EDX) revealed that the natural powder has a mixed elemental composition and consist mainly of iron oxide with 50 % of iron. In order to determine the crystal phase composition of the natural iron oxide (NIO), X-ray diffraction (DRX) measurement and infrared absorption spectroscopy (FTIR) were carried out. The results showed that the NIO has a mixed crystal structure composed mainly of hematite and lesser extent of goethite. The specific surface area and the total pore volume of the NIO were 79.015 m2g−1 and 0.0892 cm3g−1 respectively, measured by the Brunauer Emmett–Teller method (BET). The Raman spectrum of the NIO confirmed that the sample has seven characteristic peaks attributable to hematite. The optical properties of soil powder were examined by UV-vis diffuse reflectance spectroscopy (DRS). The pH of point of zero charge (pHpzc) of the adsorbent was determined, a value of 8.3 was found. The photocatalytic activity of the NIO particles was tested by the decomposition of aqueous solution of different class of compounds; phenolic compounds, pesticides and dyes due to their presence in many types of wastewaters. The sorption on the surface of the NIO with photocatalytic oxidation using oxalic acid and hydrogen peroxide would be an effective oxidation process for the removal of contaminants under UV and solar irradiation. High percentages of degradation of 1- Naphtol (1-NP) and Linuron were found about, 94.6 %, 97.2 % respectively, in presence of NIO and H2O2 under UV irradiation. The presence of oxalic acid with NIO enhanced the photodegradation of 2,6-dimethylphenol (2,6-DMP), 2-chlorophenol (2-CP) and Methylene blue (MB) with 72 %, 92 % and 100 % percentages of degradation respectively. [ABSTRACT FROM AUTHOR]

This work was carried out in the field of water treatment using advanced oxidation processes (AOPs), especially photolysis of carboxylic acid that leads to the formation in situ of hydroxyl radical (·OH). Cresol red (CR) degradation induced by organic acids/UV system was investigated in aqueous solution. The preliminary study of CR-organic acid mixture in the dark and at room temperature allowed confirming the absence of interaction under our experimental conditions. However, upon irradiation at 365 nm, the proportion of elimination of CR was 89% after 5 h of irradiation. Indeed, the CR degradation efficiency depends on the acid concentration and the pH of the medium. The concentration of acid is optimized to the 5 × 10−3 M. pH 2.39 was the optimal one when C2HO−4 was the most important species at this pH. The use of i-PrOH as ·OH confirmed the involvement of ·OH in photodegradation of CR induced by Ox. The addition of metal ions including Zn2+ and Cu2+ to the CR-organic acid mixture slowed the CR degradation unlike Fe2+, hence an improvement of its disappearance was observed. The results showed a faster degradation of the pollutant under excitation by sunlight. This environmentally friendly method appears to be very effective in the treatment of wastewater. [ABSTRACT FROM AUTHOR]

The photocatalytic degradation of 1-naphthol (1-NP) using natural iron oxide (NIO) as a heterogeneous catalyst in the presence of oxalic acid was investigated under UV irradiation. The characterization of this catalyst revealed that NIOhas a mixed elemental composition and consists mainly of iron oxide (α-Fe2O3). This powder contains hematite as iron source and its dissolution provides Fe3+cations for the photo-Fenton-like reaction in solution. The degradation rate was strongly influenced by oxygen, initial concentration of oxalic acid (Cox) and 1-NP. The optimal Coxwas 1mM. The first-order kinetic constant for the degradation of 1-NP decreased with the increase in the initial concentration of 1-NP. Furthermore, the variation of pH and the concentration of Fe2+ during the photoreaction were also strongly dependent on the Cox. The use of 1% of tertiobutanol as a scavenger confirmed the intervention of hydroxyl radicals in the photodegradation of 1-NP. Since both oxalic acid and iron oxides are common constituents of natural waters, this investigation will give a new insight to understanding the 1-NP photodegradation in natural environment. [ABSTRACT FROM AUTHOR]