Pollutant degradation

Catalytic wet peroxide oxidation (CWPO) has been assessed at semi-batch lab scale for the removal of natural organic matter (NOM) from raw surface water currently employed as feedstock in a drinking water treatment's plant. The peroxide solution has been stepwise added and its catalytic activation carried out by Al/Fe-pillared clays prepared from concentrated or diluted both, metal precursor solutions and clay suspensions (aqueous or ethanolic). An improved hydrolysis ratio (OH/(Al + Fe)) of 1.6 was found by Ferron analyses for the preparation of the concentrated metal precursor ([Al + Fe] = 0.628 mol/dm 3 ), without significant metal loss by precipitation. Increased concentration of the pillaring precursor solution led to: (i) slightly decreased and (ii) more broadly distributed XRD-basal spacings, but also (iii) higher cationic compensation on the starting clay. Ethanol as suspension medium enabled the oligomer intercalation to be less susceptible against the clay concentration. It was achieved up to 96% of chemical oxygen demand (COD) removal in 4 h and total color removal in less than 45 min of reaction for a selected catalyst, under very mild conditions of room temperature and atmospheric pressure. The clay catalysts displayed high chemical stability against iron leaching. In addition, the solid prepared from the concentrated metal precursor in a 25% (w/v) ethanolic suspension successfully performed in a high demanding catalytic test, which involved very high humic substrate-to-catalyst ratio, prolonged time of reaction (24 h) and close to neutral pH of reaction (7.5), identical to that featured by the raw surface water.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Photocatalysis process is widely investigated for removal of various pollutants from water and wastewater. ZrO2 is a common metal oxide semiconductor with excellent optical properties, non-toxicity, stability in acidic and alkaline media, and high thermal stability. The appropriate potential levels of conduction and valence bands of this metal oxide are among its other desirable properties. Therefore, ZrO2 is a promising candidate for the photocatalysis process and the photocatalytic degradation of various pollutants in water treatment. However, the pure ZrO2 is not efficient enough due to its high recombination rate of electron-hole pairs and wide bandgap. The combination of ZrO2 with other semiconductors is an effective strategy to tackle these disadvantages. This not only delays the recombination of electron-hole pairs but also reduces the bandgap of the composite, improving light absorption in the visible region in many cases. In the photocatalysis process, noble metal-free materials have been gaining traction, as they are inexpensive and eco-friendly, and therefore applicable for large-scale industrial uses. This paper reports a review of the combination of noble metal-free materials with ZrO2 and its effects on optical properties, surface, and water treatment efficiency. This study also reviews several complex mechanisms of active species generation and pollution degradation through ZrO2-based photocatalysts. The photocatalytic activities of photocatalysts are then analyzed under different experimental conditions. Finally, a few suggestions are made for future research avenues, the systematic design of ZrO2-based photocatalysts, and the synthesis of photocatalysts activated in visible-light with high efficiency in the removal of pollutants from the water.

We evaluated three types of functionalized, graphene-based materials for activating persulfate (PS) and removing (i.e., sorption and oxidation) sulfamethoxazole (SMX) as a model emerging contaminant. Although advanced oxidative water treatment requires PS activation, activation requires energy or chemical inputs, and toxic substances are contained in many catalysts. Graphene-based materials were examined herein as an alternative to metal-based catalysts. Results show that nitrogen-doped graphene (N-GP) and aminated graphene (NH 2 -GP) can effectively activate PS. Overall, PS activation by graphene oxide was not observed in this study. N-GP (50 mg L À1 ) can rapidly activate PS (1 mM) to remove >99.9% SMX within 3 h, and NH 2 -GP (50 mg L À1 ) activated PS (1 mM) can also remove 50% SMX within 10 h. SMX sorption and total removal was greater for N-GP, which suggests oxidation was enhanced by increasing proximity to PS activation sites. Increasing pH enhanced the N-GP catalytic ability, and >99.9% SMX removal time decreased from 3 h to 1 h when pH increased from 3 to 9. However, the PS catalytic ability was inhibited at pH 9 for NH 2 -GP. Increases in ionic strength (100 mM NaCl or Na 2 SO 4 ) and addition of radical scavengers (500 mM ethanol) both had negligible impacts on SMX removal. With bicarbonate addition (100 mM), while the catalytic ability of N-GP remained unaltered, NH 2 -GP catalytic ability was inhibited completely. Humic acid (250 mg L À1 ) was partially effective in inhibiting SMX removal in both N-GP and NH 2 -GP systems. These results have implications for elucidating oxidant catalysis mechanisms, and they quantify the ability of functionalization of graphene with hetero-atom doping to effectively catalyze PS for water treatment of organic pollutants including emerging contaminants.

This work reviews an eco-friendly process for producing TiO2 via colloidal aqueous sol–gel synthesis, resulting in crystalline materials without a calcination step. Three types of colloidal aqueous TiO2 are reviewed: the as-synthesized type obtained directly after synthesis, without any specific treatment; the calcined, obtained after a subsequent calcination step; and the hydrothermal, obtained after a specific autoclave treatment. This eco-friendly process is based on the hydrolysis of a Ti precursor in excess of water, followed by the peptization of the precipitated TiO2. Compared to classical TiO2 synthesis, this method results in crystalline TiO2 nanoparticles without any thermal treatment and uses only small amounts of organic chemicals. Depending on the synthesis parameters, the three crystalline phases of TiO2 (anatase, brookite, and rutile) can be obtained. The morphology of the nanoparticles can also be tailored by the synthesis parameters. The most important parameter is ...

This work reviews an eco-friendly process for producing TiO2 via colloidal aqueous sol–gel synthesis, resulting in crystalline materials without a calcination step. Three types of colloidal aqueous TiO2 are reviewed: the as-synthesized type obtained directly after synthesis, without any specific treatment; the calcined, obtained after a subsequent calcination step; and the hydrothermal, obtained after a specific autoclave treatment. This eco-friendly process is based on the hydrolysis of a Ti precursor in excess of water, followed by the peptization of the precipitated TiO2. Compared to classical TiO2 synthesis, this method results in crystalline TiO2 nanoparticles without any thermal treatment and uses only small amounts of organic chemicals. Depending on the synthesis parameters, the three crystalline phases of TiO2 (anatase, brookite, and rutile) can be obtained. The morphology of the nanoparticles can also be tailored by the synthesis parameters. The most important parameter is ...

Contribution of Reactive species for removal of textile effluent with photocatalysis under UV and visible lights Highlights: Textile effluent removal by photocatalysis in visible light is studied Removal pollutants with TiO2 impregnated polyester is investigated Effect of UV-C activated polyester catalysts is studied The role and contribution of reactive oxidizing species were examined

Degradation of amoxicillin (AMX) was achieved using pillared montmorillonite ferric oxalate (PMFeOx) catalyst in photo-Fenton process. The catalyst was prepared by aluminum pillaring of mild acid treated montmorillonite (MATM) clay followed by incorporation of ferric oxalate. The PMFeOx catalyst produced was characterized. XRD results revealed the intercalation of aluminum with an increase in basal spacing from 1.24 to ∼1.69 nm, the specific surface area also increased from 164.94 to 211.61 m 2 g −1. SEM images of PMFeOx showed the formation of irregular flaky morphology with random orientation. The FTIR profile at relevant wavenumbers detected intercalation of aluminum and incorporation of iron. The optimum condition that achieved 99.65% and 84.26% initial concentration reduction and COD removal respectively, for 40 ppm AMX solution was 15% excess H 2 O 2 and 2.0 g PMFeOx catalyst loading at 40 • C in 10 min. The catalyst displayed good efficiency in degrading amoxicillin.

This work reviews an eco-friendly process for producing TiO2 via colloidal aqueous sol–gel synthesis, resulting in crystalline materials without a calcination step. Three types of colloidal aqueous TiO2 are reviewed: the as-synthesized type obtained directly after synthesis, without any specific treatment; the calcined, obtained after a subsequent calcination step; and the hydrothermal, obtained after a specific autoclave treatment. This eco-friendly process is based on the hydrolysis of a Ti precursor in excess of water, followed by the peptization of the precipitated TiO2. Compared to classical TiO2 synthesis, this method results in crystalline TiO2 nanoparticles without any thermal treatment and uses only small amounts of organic chemicals. Depending on the synthesis parameters, the three crystalline phases of TiO2 (anatase, brookite, and rutile) can be obtained. The morphology of the nanoparticles can also be tailored by the synthesis parameters. The most important parameter is ...

Hybrid montmorillonite-alginate beads (MABs) were prepared by the ion-gelation method from alginate and montmorillonite clay suspension dropped in a calcium chloride solution. Similarly, iron-enriched beads (Fe-MABs) were prepared using iron-exchanged montmorillonite. All beads were characterized by atomic absorption and Fourier-transform infrared spectroscopy. The efficiency of Fe-MABs as catalysts for the solar photo-Fenton performed at initial pH = 7.0 was evaluated by varying the catalyst amount and hydrogen peroxide concentration, and monitoring the removal of 4-nitrophenol (4-NP) at initial concentration of 10 ppm. A kinetic analysis showed that the removal of 4-NP by Fe-MABs followed a pseudo first-order kinetics model (R 2 = 0.966). High 4-NP removal (75%) was achieved with 25 Fe-MABs by using 150 ppm of hydrogen peroxide and 40 min of irradiation, while total 4-NP removal was obtained by using 500 ppm of hydrogen peroxide. Moreover, preliminary studies about beads' recycling showed good removal efficiencies for the first three cycles.

In order to enhance depuration of pollutants in photo-Fenton process, copper modified bentonite supported ferrioxalate catalyst (CuMBFOx) was synthesized. The catalyst was characterized with TGA, XRF, XRD, FTIR, BET and SEM techniques. Its catalytic activity was evaluated on the degradation of Direct Blue 71 (DB71), Acid Green 25 (AG25) and Reactive Blue 4 (RB4) dye pollutants in batch photo-Fenton process without pH adjustment. The results showed complete depuration below the detection point of UV-vis spectrophotometer as monitored on their respective UV-vis degradation spectra. The extent of mineralization ability of the CuMBFOx was monitored with chemical oxygen demand (COD) analysis and was used to study the kinetics of mineralization of the dyes using a developed phenomenological mathematical model. The result showed that the efficiency reduced in the order DB71 > AG25 > RB4 owning to their chemical components and structural complexities. CuMBFOx demonstrated excellent qualities toward depuration of DB71, AG25 and RB4.

Ferric oxalate catalyst supported on phosphoric acid treated kaolin (ATKaol) was prepared and tested on the degradation of 4-nitrophenol (4-NP). The X-ray fluorescence (XRF) and Brunauer-Emmett-Teller (BET) characterization results showed drastic distortions in the raw kaolin (Kaol) crystalline structure and an increase in specific surface area (SSA) from 18.78 to 166.12 m 2 g −1 after acid treatment. The incorporation of Fe was confirmed with Fourier transformed infra-red spectroscopy (FTIR), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) results. The degradation of 4-NP without UV was slower compared to when UV was used. There was no appreciable degradation in the absence of either catalyst or hydrogen peroxide (HP). The acid treated kaolinite catalyst (ATKaolCat) exhibits high catalytic activity without pH adjustment degrading 99% of 4-NP (100 ppm) in 4 min using 2.0 g ATKaolCat and 20% excess HP at 40°C. The reusability study shows 9.4% decrease in efficiency after 5 rounds. The kinetic model developed showed good agreement with the experimental data. The model showed that ATKaolCat has higher selectivity for direct oxidation of 4-NP to mineralized products compared to oxidation via intermediates. These qualities make the catalyst promising in 4-NP degradation.

We report the synthesis of pillared clays from natural Mexican bentonites and pillared solutions as a support for Cu and Fe 3+ catalyst. The study shows a favorable cationic exchange capacity on the clays. This is observed with a change of the specific areas: from 66 m 2 /g for the natural clay to 202 m 2 /g for the pillared clay. The molar relation of 4.91 for the Si/Al structure in the natural clay and 3.72 for the pillared clay shows the entrance of aluminum as pillaring ion. We were able to increase the microporosity on the catalytic material observed through a porous volume variation (0.1-0.8 cm 3 /g) at different Fe 3+ concentrations. We obtained an increase on the specific area of more than 200% over the natural clay. Published by Elsevier B.V.

The aim of this study was to investigate the photodegradation of organic pollutants in natural environment with coexistence of iron oxides and oxalic acid. Methylene Blue (MB) was selected as a model pollutant while Fe 2 O 3 was selected as iron oxide. Commercial Fe 2 O 3 was calcined at 300°C, 400°C and 500°C and was used to degrade MB in oxalate solutions of different concentration under UV radiation. Adsorption of MB on the surface of calcined Fe 2 O 3 was studied and 30 minutes was required to reach the adsorption equilibrium. The effect of the initial concentration of oxalic acid, initial concentration of MB and calcined temperature of Fe 2 O 3 on photodegradation of MB in the Fe 2 O 3-oxalate suspension under UV light irradiation was investigated. Oxalic acid plays a very important role, no significant degradation of MB was found in absence of oxalic acid in the suspension. But excess concentration of oxalic acid decreases the degradation. Photodegradation of MB increases with increasing calcined temperature of Fe 2 O 3 and decreases with increase in MB concentration. Since this process does not require the addition of hydrogen peroxide and shows good efficiency under UV irradiation, it is an economically viable method for pre-treating wastewater containing dye.

Catalytic wet peroxide oxidation (CWPO) has been assessed at semi-batch lab scale for the removal of natural organic matter (NOM) from raw surface water currently employed as feedstock in a drinking water treatment's plant. The peroxide solution has been stepwise added and its catalytic activation carried out by Al/Fe-pillared clays prepared from concentrated or diluted both, metal precursor solutions and clay suspensions (aqueous or ethanolic). An improved hydrolysis ratio (OH/(Al + Fe)) of 1.6 was found by Ferron analyses for the preparation of the concentrated metal precursor ([Al + Fe] = 0.628 mol/dm 3 ), without significant metal loss by precipitation. Increased concentration of the pillaring precursor solution led to: (i) slightly decreased and (ii) more broadly distributed XRD-basal spacings, but also (iii) higher cationic compensation on the starting clay. Ethanol as suspension medium enabled the oligomer intercalation to be less susceptible against the clay concentration. It was achieved up to 96% of chemical oxygen demand (COD) removal in 4 h and total color removal in less than 45 min of reaction for a selected catalyst, under very mild conditions of room temperature and atmospheric pressure. The clay catalysts displayed high chemical stability against iron leaching. In addition, the solid prepared from the concentrated metal precursor in a 25% (w/v) ethanolic suspension successfully performed in a high demanding catalytic test, which involved very high humic substrate-to-catalyst ratio, prolonged time of reaction (24 h) and close to neutral pH of reaction (7.5), identical to that featured by the raw surface water.

The effects of hydrochloric acid (HCL) modification of the surface area, morphology and physico-chemical properties of Sayong kaolinite clay was investigated in this study. Sayong kaolinite clay was refluxed with different concentration of HCL (1M, 5M and 10M) at 100˚C for 4 hours and followed by calcination at 500˚C at 1 hour. The samples of untreated and treated clay were characterized by different analytical equipment such as BET Surface Area Analyzer, X-Ray Fluorescence (XRF), Fourier Transform Infrared (FTIR), Thermogravimetric Analyzer (TGA) and Field Emission Scanning Electron Microscopy (FESEM). The acid treatment increased the surface area of the Sayong kaolinite clay almost three times from 24.46 m 2 /g to the maximum value which is 64.04 m 2 /g once treated with 5M HCL. The increasing of the surface area is due to the formation of amorphous silica phase and removal of the octahedral Al 3+ cations and other impurities (such as Mg 2+ , K + , Ca + etc.) when the acid strength is increasing as reported in XRF analysis. FTIR study shows the change of the peak intensity of several types of structural OH groups that presently in the untreated and acid treated samples. TGA-DTA profiles shows that acid treatment increased the amount of physisorbed water as the acid concentration is increased. There are three of endothermic peaks was observed in the untreated sample which centered at 49˚C, 275˚C and 520 ˚C. However, when the clay samples treated with acid, it has increased the physisorbed water and decreased the structural and coordinated water which caused the change in the endothermic curves in the treated sample.

Degradation of amoxicillin (AMX) was achieved using pillared montmorillonite ferric oxalate (PMFeOx) catalyst in photo-Fenton process. The catalyst was prepared by aluminum pillaring of mild acid treated montmorillonite (MATM) clay followed by incorporation of ferric oxalate. The PMFeOx catalyst produced was characterized. XRD results revealed the intercalation of aluminum with an increase in basal spacing from 1.24 to ∼1.69 nm, the specific surface area also increased from 164.94 to 211.61 m 2 g −1 . SEM images of PMFeOx showed the formation of irregular flaky morphology with random orientation. The FTIR profile at relevant wavenumbers detected intercalation of aluminum and incorporation of iron. The optimum condition that achieved 99.65% and 84.26% initial concentration reduction and COD removal respectively, for 40 ppm AMX solution was 15% excess H 2 O 2 and 2.0 g PMFeOx catalyst loading at 40 • C in 10 min. The catalyst displayed good efficiency in degrading amoxicillin.

Degradation of amoxicillin (AMX) was achieved using pillared montmorillonite ferric oxalate (PMFeOx) catalyst in photo-Fenton process. The catalyst was prepared by aluminum pillaring of mild acid treated montmorillonite (MATM) clay followed by incorporation of ferric oxalate. The PMFeOx catalyst produced was characterized. XRD results revealed the intercalation of aluminum with an increase in basal spacing from 1.24 to ∼1.69 nm, the specific surface area also increased from 164.94 to 211.61 m 2 g −1 . SEM images of PMFeOx showed the formation of irregular flaky morphology with random orientation. The FTIR profile at relevant wavenumbers detected intercalation of aluminum and incorporation of iron. The optimum condition that achieved 99.65% and 84.26% initial concentration reduction and COD removal respectively, for 40 ppm AMX solution was 15% excess H 2 O 2 and 2.0 g PMFeOx catalyst loading at 40 • C in 10 min. The catalyst displayed good efficiency in degrading amoxicillin.

The effects of phosphoric acid treatment on kaolinite (Kaol) as catalyst support were investigated in this study. The results showed that as the acid concentration was increased from 5 to 10 M, there was increment in the specific surface area from 18.78 in Kaol to 36.0 and 145.5 m 2 g −1 in 5 M acid treated Kaol supported catalyst (5 M-AT-KaolCat) and 10 M acid treated Kaol supported catalyst (10 M-AT-KaolCat), respectively. Characterization results showed that 10 M-AT-KaolCat has higher percentage of Fe than the 5 M-AT-KaolCat due to the effect of acid treatment which provided larger surface area for its anchoring. Consequently, degradation efficiency is comparably faster in 10 M-AT-KaolCat with about 99% of 40 ppm amoxicillin degraded in 8 min without pH adjustments while it takes 12 min using 5 M-AT-KaolCat. The degradation process showed initial enhanced degradation efficiency with increase in the catalyst loadings which later decreased due to the scavenging effect of excess catalyst loading on the reactive hydroxyl radical. The catalysts showed high resistance to leaching due to the presence of the ferrioxalate (FeOx) ligands and the effect of phosphoric acid modification which introduces monolayer of phosphate functional group on the catalyst support through which the FeOx ligands were properly anchored.

Degradation of amoxicillin (AMX) was achieved using pillared montmorillonite ferric oxalate (PMFeOx) catalyst in photo-Fenton process. The catalyst was prepared by aluminum pillaring of mild acid treated montmorillonite (MATM) clay followed by incorporation of ferric oxalate. The PMFeOx catalyst produced was characterized. XRD results revealed the intercalation of aluminum with an increase in basal spacing from 1.24 to ∼1.69 nm, the specific surface area also increased from 164.94 to 211.61 m 2 g −1 . SEM images of PMFeOx showed the formation of irregular flaky morphology with random orientation. The FTIR profile at relevant wavenumbers detected intercalation of aluminum and incorporation of iron. The optimum condition that achieved 99.65% and 84.26% initial concentration reduction and COD removal respectively, for 40 ppm AMX solution was 15% excess H 2 O 2 and 2.0 g PMFeOx catalyst loading at 40 • C in 10 min. The catalyst displayed good efficiency in degrading amoxicillin.