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Globular NiFe2O4nanoparticles 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, NiFe2O4has 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 H2O2amounts 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 NiFe2O4could be an efficient and promising material for photocatalytic water remediation.

In the present study, we have investigated the photolysis of aliphatic and aromatic carboxylic organic acids (malic, oxalic, iminodiacetic, salicylic and benzoic) under both blacklight lamps and solar light. The ability of these acids to produce hydroxyl radicals under UVA radiation was also examined. Several experiments have been conducted to establish a relationship between the nature of the organic acid and the efficiency of the production of these radicals by the Fenton reaction. The results of this study suggest that the generation of hydrogen peroxide was influenced by the irradiation wavelength, the initial concentration of the carboxylic acid, the pH and the nature of the acid. Carbamazepine (CBZ) degradation induced by organic acids/UV system in aqueous solution was tested and confirmed that photocatalytic efficiency is optimal when oxalic acid is used. CBZ mineralization was followed by total organic carbon (TOC) analyzer, the mineralization efficiency reaches 80% of TOC removal after 14 h of irradiation (CBZ/oxalate/UVA system). Upon solar irradiation, a complete CBZ disappearance takes place after 1 h in system oxalic acid/CBZ.

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 logβ = 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 FeIIIwas instantaneous and consequently, the degradation of IBP was achieved by the formation of the hydroxyl radicals (•OH) generated during the Fenton-like 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 H2O2and 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 technology.

This study aims at providing a new method for effective decontamination of organic pollutants in the field of water treatment. This study shows that using advanced oxidation processes in particular the photocatalytic oxidation of L-ascorbic acid (H2A) by molecular oxygen in the presence of copper (Cu(lI)), hydroxyl radicals COH) are generated thus enabling the degradation of organic pollutants. The oxidation of H2A by oxygen with Cu(II) as catalyst to stimulate the degradation of orange G (OG) dye in aqueous solution was investigated in the absence (Cu(II)/H2A) and presence of artificial and natural light (Cu(II)/H2A/UV310 nmor sunlight, respectively). All the decolorization experiments were performed at room temperatUre (20°C) within 300 min and with initial OG concentration of 0.05 mM. The effect of different parameters such as dosages of H2A, dosage of Cu(II) and solution pH on the degradation efficiency of the processes were also investigated. The results show that the optimal degradation condition was selected at an initial pH of 4.5, H2A dosage of 5 mM and Cu(II) dosage of 1 mM. The use of a radical scavenger, tert-butanol, confirmed the involvement of •OH in OG degradation in both systems. Likewise, the addition of hydrogen peroxide (H2O2) in the previous systems leads to •OH radicals formation via the Fenton-like and photo-Fenton-like systems. The influence of solar light was also studied showing a significant enhancement in the photodegradation efficiency of OG. In the Cu(II)/H2A/sunlight system, OG degradation of 93.6% was achieved after 2 h of reaction time compared with 100% degradation when using the Cu(II)/H2A/H2O2/sunlight. These results show that the photo-oxidation of H2A with Cu(II) open a new pathway in the degradation of refractory pollutants by a natural processes.

The catalytic efficiency of a natural mineral to promote photocatalysis and Fenton-like reaction was examined by using a cationic dye, Cristal Violet (CV) as a model compound at pH 8.3. The adsorption of CV on natural iron oxide (NIO) surface was investigated from both equilibrium and kinetic point of view and the sorption isotherm was fitted using the Freundlich model. The NIO shows high photo- catalytic activity in the presence of ultraviolet and solar light with CV conversion higher than 64% and 96% after 300 min of reaction respectively. The presence of hydrogen peroxide in aqueous NIO slurry produces a beneficial enhancement of the reaction rate of CV removal, leading to a heterogeneous Fenton-like reaction at pH 8.3. The effects of different parameters such as initial concentration of H2O2, solution pH and UV light on the decolorization efficiency of the process were studied. The results indicated that in dark Fenton-like process, the reduction of initial pH from 8.3 to pH 3.0 increases CV removals from 66.8% and 78.5%. At pH 3, the reaction is essentially a combination of heterogeneous Fenton-like process associated with typical homogeneous Fenton reaction due to the dissolution of NIO. Photo-Fenton-like oxidation leads to higher removal rate than Fenton either at pH 3 or pH 8.3. After three runs of regeneration, the activity of the catalyst shows the same efficiency in Fenton-like process. Based on the results of this study NIO may be considered as a promising material for photo- catalytic water treatment.

The photocatalytic degradation of 2,4-dichlorophenol (2,4-DCP) has been studied using natural iron oxide (NIO) as a heterogeneous catalyst under various conditions. NIO was found to be inactive for 2,4-DCP degradation under UV irradiation (wavelength 365 nm); however, it was very effective under solar light. 2,4-DCP was nearly completely removed with solar light in about 6 h. This can be due to the higher absorptivity of NIO in the solar system. The dependence of 2,4-DCP photodegradation on carboxylic acids in NIO–carboxylate–UV systems was investigated. The presence of oxalic acid allows the highest photocatalytic oxidation rates than other carboxylic acids such as citric, tartaric, malic and malonic acid. The results demonstrated that the 2,4-DCP photodegradation using NIO in the presence of oxalic acid followed the first-order kinetic k = 3.270 × 10–2min–1. The optimal content of the NIO and oxalic acid concentration were found to be 1.0 g L–1and 5.0 mM, respectively. The use of 2.0% of isopropanol as a scavenger confirmed the intervention of hydroxyl radicals in the photodegradation of 2,4-DCP. The reaction intermediates were identified by an ultrahigh performance liquid chromatography coupled high-resolution mass spectrometry analysis and a reaction mechanism was proposed. Complete mineralization has been confirmed by chemical oxygen demand analysis. A series of experiments were also carried out with solar light in order to compare the results with those obtained with UV irradiation. The process NIO–carboxylate (oxalate, citrate, tartrate and malate) shows good efficiency under solar light, it is an economically viable method for pretreating wastewaters containing recalcitrant pollutants such as chlorophenolic compounds.

AbstractThe aim of this study is to test the ability of photochemical processes (photolysis, Acetone/UV and H2O2/UV at 254 nm) to eliminate the Methyl Green (MG, cationic structure) and Bromocresol Purple (BCP, anionic structure) in aqueous solution in mono and binary systems. The obtained results show that the rate of decolorization by UV photolysis at 254 nm in single system is weak for BCP (25%) and acceptable for MG (66%). In dark conditions, preliminary experiments show no decolorization of the two dyes in the presence of acetone and in the presence of H2O2for BCP. However, classical oxidation has been observed for MG in H2O2for concentrations superior to 5 × 10−4 M. In the presence of light, a real improvement in the decolorization rate of both dyes is obtained using H2O2/UV (acting via issued from photolysis of H2O2at 254 nm) and Acetone/UV (acting via energy transfer from the sensitizer which is Acetone to the dye). In the mixture systems, the Acetone/UV process is more effective than direct UV photolysis and H2O2/UV. In the three photochemical processes used, each dye decreases the removal efficiency of the other. The dyes removal kinetics follows the pseudo-first-order model in Acetone/UV and H2O2/UV systems for both dyes in single and binary systems.

The aim of this study is to test the ability of photochemical processes (photolysis, Acetone/UV and H2O2/UV at 254 nm) to eliminate the Methyl Green (MG, cationic structure) and Bromocresol Purple (BCP, anionic structure) in aqueous solution in mono and binary systems. The obtained results show that the rate of decolorization by UV photolysis at 254nm in single system is weak for BCP (25%) and acceptable for MG (66%). In dark conditions, preliminary experiments show no decolorization of the two dyes in the presence of acetone and in the presence of H2O2for BCP. However, classical oxidation has been observed for MG in H2O2for concentrations superior to 5 × 10−4 M. In the presence of light, a real improvement in the decolorization rate of both dyes is obtained using H2O2/UV (acting via ⋅OHissued from photolysis of H2O2at 254 nm) and Acetone/UV (acting via energy transfer from the sensitizer which is Acetone to the dye). In the mixture systems, the Acetone/UV process is more effective than direct UV photolysis and H2O2/UV. In the three photochemical processes used, each dye decreases the removal efficiency of the other. The dyes removal kinetics follows the pseudo-first-order model in Acetone/UV and H2O2/UV systems for both dyes in single and binary systems.

AbstractThe azo dyes are considered as one of the highest toxic compounds of water pollution. Decolorization of these compounds has been carried out via photochemical methods (direct UV photolysis and advanced oxidation processes abbreviated as AOPs) since they are highly resistant to conventional treatment. In this study, direct UV photolysis (under 254, 365, 310 nm, and solar), acetone/UV (254 nm and acetone as a sensitizer), H2O2/UV, /UV, /H2O2/UV and /heat (absence of light), have been investigated in lab-scale experiments for decolorization of Alizarin yellow (abbreviated as AY). From the experimental results, it has been found that color removal followed the increasing order: UV photolysis (negligible) < acetone/UV < /heat < /H2O2/UV < /UV < H2O2/UV. This improvement might be attributed strictly to radicals HOin the case of H2O2/UV, HOand in the case of /UV, and heat/in absence of light. The effects of parameters like concentrations of H2O2, and acetone, and temperature have been studied and the optimum operational conditions were found. In another part, the UV–Vis spectral changes of AY during UV/H2O2and UV/treatments, showed that it was easier to destroy the bonding linkage –N=N– and then the long chain C=C (bathochromic system). Decolorization kinetic followed the pseudo-first-order for all systems.

The azo dyes are considered as one of the highest toxic compounds of water pollution. Decolorization of these compounds has been carried out via photochemical methods (direct UV photolysis and advanced oxidation processes abbreviated as AOPs) since they are highly resistant to conventional treatment. In this study, direct UV photolysis (under 254, 365, 310 nm, and solar), acetone/UV (254 nm and acetone as a sensitizer), H2O2/UV, S2O82-/UV, S2O82-/H2O2/UV and S2O82-/heat (absence of light), have been investigated in lab-scale experiments for decolorization of Alizarin yellow (abbreviated as AY). From the experimental results, it has been found that color removal followed the increasing order: UV photolysis (negligible) < acetone/UV < S2O82-/heat < S2O82-/H2O2/UV < S2O82-/UV < H2O2/UV. This improvement might be attributed strictly to radicals HO⋅in the case of H2O2/UV, HO⋅and SO4⋅-in the case of S2O82-/UV, and heat/S2O82-in absence of light. The effects of parameters like concentrations of H2O2, S2O82-and acetone, and temperature have been studied and the optimum operational conditions were found. In another part, the UV–Vis spectral changes of AY during UV/H2O2and UV/S2O82-treatments, showed that it was easier to destroy the bonding linkage –N=N– and then the long chain C=C (bathochromic system). Decolorization kinetic followed the pseudo-first-order for all systems.

AbstractThe transformation of 1-Naphthol (1-NP) photoinduced by a natural iron oxide (NIO) in aqueous suspension and the influence of oxalic acid have been investigated under monochromatic irradiation (365 nm). The NIO was characterized by X-ray diffraction (XRD), X-ray fluorescence, and Brunauer–Emmett–Teller methods. The XRD result shows that the NIO consists of mixed crystalline hematite. A dark investigation of the system was performed before studying the photochemical behavior. The experiment shows that the NIO possesses a high adsorption capacity for 1-NP and its photodissolution was not observed. Also, the experiment shows that the UV light alone could play an important role in the degradation of 1-NP.After 3 h of irradiation at pH 9.4, 64.2% of 1-NP was degraded. The presence of the NIO was found to promote the photodegradation of 1-NP (72.1%) and the process follows pseudo-first-order reaction kinetics. The photodegradation of 1-NP has been studied at different pH (1.9–12) and catalyst loads (0.5–2.0 g L−1). The results demonstrated that the phototransformation of 1-NP is enhanced by increasing the pH and the optimal initial concentration of the catalyst was found to be 1 g L−1. The involvement of •OH radicals was ruled out because of the non-influence of tertiobutanol used as a scavenger. The effect of the oxalic acid on the photodegradation of 1-NP by NIO was also investigated. The result revealed that the oxalic acid promoted the photodegradation rate of 1-NP. This investigation will give a new insight to understand the 1-NP photodegradation in natural environment. Measuring chemical oxygen demand also monitors the toxicity of the degraded 1-NP solution and a significant decrease is observed, which implies that the photodegradation through NIO is a safer technique.

The transformation of 1-Naphthol (1-NP) photoinduced by a natural iron oxide (NIO) in aqueous suspension and the influence of oxalic acid have been investigated under monochromatic irradiation (365 nm). The NIO was characterized by X-ray diffraction (XRD), X-ray fluorescence, and Brunauer–Emmett–Teller methods. The XRD result shows that the NIO consists of mixed crystalline hematite. A dark investigation of the system was performed before studying the photochemical behavior. The experiment shows that the NIO possesses a high adsorption capacity for 1-NP and its photodissolution was not observed. Also, the experiment shows that the UV light alone could play an important role in the degradation of 1-NP.After 3 h of irradiation at pH 9.4, 64.2% of 1-NP was degraded. The presence of the NIO was found to promote the photodegradation of 1-NP (72.1%) and the process follows pseudo-first-order reaction kinetics. The photodegradation of 1-NP has been studied at different pH (1.9–12) and catalyst loads (0.5–2.0g L−1). The results demonstrated that the phototransformation of 1-NP is enhanced by increasing the pH and the optimal initial concentration of the catalyst was found to be 1 g L−1. The involvement of •OH radicals was ruled out because of the non-influence of tertiobutanol used as a scavenger. The effect of the oxalic acid on the photodegradation of 1-NP by NIO was also investigated. The result revealed that the oxalic acid promoted the photodegradation rate of 1-NP. This investigation will give a new insight to understand the 1-NP photodegradation in natural environment. Measuring chemical oxygen demand also monitors the toxicity of the degraded 1-NP solution and a significant decrease is observed, which implies that the photodegradation through NIO is a safer technique.

AbstractThe aim of this study is to test some advanced oxidation techniques (AOTs) in the absence of light (Fenton and Fenton-like) and in its presence (photo-Fenton and photo-Fenton-like) to obtain total decolorization of an anionic dye in aqueous solution: the bromocresol Green (CI Reactive Green 15 and abbreviated as BCG). Experiments were conducted on a laboratory-scale set up with all these processes. Best operatory conditions were found to be of pH 3, hydrogen peroxide to iron (II or III) molar ratio of 30:1, artificial (254 nm) and solar light. Besides, several parameters were investigated like pH, oxygen, dose of H2O2, light effect, and reaction time. The obtained results showed that color removal followed the increasing order: Fe(III)/H2O2 < Fe(II)/H2O2 < Fe(II)/H2O2/Solar < Fe(II)/H2O2/UV254nm < Fe(III)/H2O2/UV254nm. This improvement could be related to a better production of radicals . In another hand, decolorization kinetic followed pseudo-first-order type in all cases and no synergic effect was observed when Cu2+ion (10−4M) was added to the solution of the dye.

The aim of this study is to test some advanced oxidation techniques (AOTs) in the absence of light (Fenton and Fenton-like) and in its presence (photo-Fenton and photo-Fenton-like) to obtain total decolorization of an anionic dye in aqueous solution: the bromocresol Green (CI Reactive Green 15 and abbreviated as BCG). Experiments were conducted on a laboratory-scale set up with all these processes. Best operatory conditions were found to be of pH 3, hydrogen peroxide to iron (II or III) molar ratio of 30:1, artificial (254 nm) and solar light. Besides, several parameters were investigated like pH, oxygen, dose of H2O2, light effect, and reaction time. The obtained results showed that color removal followed the increasing order: Fe(III)/H2O2 < Fe(II)/H2O2 < Fe(II)/H2O2/Solar < Fe(II)/H2O2/UV254nm < Fe(III)/H2O2/UV254nm. This improvement could be related to a better production of radicals OH·. In another hand, decolorization kinetic followed pseudo-first-order type in all cases and no synergic effect was observed when Cu2+ion (10−4M) was added to the solution of the dye.

The photocatalytic oxidation of o-, m-, and p-, cresol (2-MP, 3-MP, 4-MP) was compared with ZnO (Vieille Montagne SA) and TiO2 (Societe Thann et Mulhouse). The same products were obtained with both photocatalysts. The main identified products are methylhydroquinone, 3-methylpyrocatechol and pyrocatechol with 2-MP; methylhydroquinone, 3-methylpyrocatechol and 4-methylpyrocatechol with 3-MP; 4-methylpyrocatechol and hydroquinone with 4-MP. They result from o- and p-hydroxylation with or without substitution of methyl group. The rate of photocatalytic transformation increases with increasing pH and with addition of small amounts of hydrogen peroxide. The limited inhibition by ethanol suggests that hydroxyl radicals are the main but not the only oxidizing species involved.