Catalytic Wet Peroxide Oxidation Research Articles

On developing ferrisilicate catalysts supported on silicon carbide (SiC) foam catalysts for continuous catalytic wet peroxide oxidation (CWPO) reactions

Fe supported catalysts show great promise for enabling practical environmental catalysis, exemplified by the catalytic wet peroxide oxidation (CWPO) process. In order to mitigate the Fe leaching issue, a strategy of assembling zeolitic coatings with intraframework Fe (ferrisilicate) on SiC foams was developed, showing a good stability in CWPO and a low Fe leaching of 2.0 mg l−1. Direct hydrothermal synthesis of ferrisilicate/SiC foam composites was systematically studied, showing that their characteristics depend on the growth time, pH value and iron concentration of the growth solution. Selected ferrisilicate/SiC foam composite was evaluated using the continuous CWPO of phenolic aqueous solution at 60 °C. The open-cell size of SiC foam was varied between 800 and 2,000 μm and showed insignificant effect on the hydrodynamics of the flow process at 1 ml min −1, but the process efficiency in terms of phenol and total-organic-carbon (TOC) conversions was favored by a high surface-to-volume ratio (i.e. small open-cell sizes). Ferrisilicate/SiC foam catalysts (average open-cell size = 800 μm) showed good stability in the model system with the stable conversions of phenol (97%), H2O2 (84%) and TOC (37%) over 24 h time-on-stream.

Structural stabilization and characterization of active peroxo species on TiO2-nanotube based materials in mild catalytic wet peroxide oxidation process

Amorphous TiO2 based nanotubes (TN) obtained through alkaline hydrothermal restructuring of P25 were treated with various acids and functionalized with hydrogen peroxide in order to tailor formation of structurally distinctive titanium peroxo species. Obtained solids were used as catalysts in the catalytic wet peroxide oxidation (CWPO) of model methyl orange (MO) aqueous solution under mild conditions. With the usage of 2 g/L of peroxide modified TN/ClO4p 0.01 catalyst and double stoichiometric amount of hydrogen peroxide, 50 ppm MO solution was purified up to 93% during 1 h at 40°C. No decay of catalyst activity was observed in 5 consecutive runs using the same catalyst batch. 17O NMR and TPD/MS analyses have revealed that catalytic activity of TN/ClO4p 0.01 sample can mainly be assigned to bidentate η2 surface peroxo species whose amount during 5 consecutive catalytic runs is almost constant, namely 5.9×10−7 and 5.2×10−7 mol/m2 prior and after usage, respectively. In addition, it has been observed that considerable amount of thermally labile oxygen species is used during 5 consecutive runs. From 17O NMR analysis we have observed that these species can be attributed to two coordinated (OTi2) oxygen formed on the place of terminal intra/interlayered −OH groups. Former can serve as structural stabilizing agents which enable formation of new η2 surface peroxo species during CWPO runs. To the best of our knowledge, this study is the first attempt to explain the possibility for η2 peroxo species structural stabilization during CWPO under mild conditions.

On the redox nature of ceria-zirconia mixed nanocatalysts and its effect on catalytic wet peroxide oxidation of chlorinated organic pollutants

The potential application of ZrxCe1-xO2 (x: 1, 0.75, 0.5, 0.25, 0) nanocomposites in the oxidation of chlorinated phenolic compounds was studied with respect to Catalytic Wet Peroxide oxidation of 4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP) and 2,4-dichlorophenoxy acetic acid (2,4-D) was experimented in presence of aqueous hydrogen peroxide as oxidant. Zirconium doping on nanoceria lattice increased its catalytic activity towards Wet Peroxide Oxidation of the target pollutants. 4-CP (500 mg/L) was degraded with 14.9% TOC and 45.8% COD removal after 75 min at 70 °C using Zr0.75Ce0.25O2 catalyst. 2,4-DCP (250 mg/L) conversion with 22.5% TOC and 52.8% COD removal was observed at 75 min over Zr0.5Ce0.5O2 catalyst. 100% catalytic oxidative conversion of 2,4-D (250 mg/L) with 23.68% Total Organic Carbon (TOC) and 47.80% Chemical Oxygen Demand (COD) removal was achieved at 70 °C at 90 min. Temperature Programmed Reduction (TPR) analysis indicated that the reducing capacity of ceria increased on zirconium doping. The catalysts were stable and reusable upto six successive runs as demonstrated by X-ray diffraction (XRD) and surface area measurements.

Activated carbon as catalyst for microwave-assisted wet peroxide oxidation of aromatic hydrocarbons.

This paper addresses the removal of four aromatic hydrocarbons typically found in petrochemical wastewater: benzene (B), toluene (T), o-xylene (X), and naphthalene (N), by microwave-assisted catalytic wet peroxide oxidation (MW-CWPO) using activated carbon (AC) as catalyst. Under the studied conditions, complete pollutant elimination (B, 1.28mM; T, 1.09mM; X, 0.94mM; and N, 0.78mM) was achieved, with more than 90% TOC removal after only 15-min reaction time, working at 120°C, pH0 = 3, AC at 1gL-1, and H2O2 at the stoichiometric dose. Furthermore, in the case of toluene, naphthalene, and xylene, the hydroxylation and breakdown of the ring is very rapid and toxic intermediates were not detected. The process follows two steps: (i) pollutant adsorption onto AC followed by (ii) adsorbed compounds oxidation. Thus, MW-CWPO with AC as catalyst appears a promising way for a fast and effective process for B, T, X, and N removal in aqueous phase.

Highly dispersed Fe3+-Al2O3 for the Fenton-like oxidation of phenol in a continuous up-flow fixed bed reactor. Enhancing catalyst stability through operating conditions

A highly dispersed Fe3+-Al2O3 catalyst (6 wt% Fe) was used for the catalytic wet hydrogen peroxide oxidation of phenol (1 g/L) in an up-flow fixed bed reactor (UFBR) under continuous operation. To enhance catalytic performance, three simple synthesis strategies were combined: two-stage impregnation of iron citrate, acid washing with CH3COOH and thermal treatment at 900 °C. Solid samples were characterized in depth by several techniques: N2 Physisorption, XRD, SEM–EDAX, TEM, TGA, PZC, TPD of pyridine, XPS and Mössbauer. Peroxidation experiments were performed in an UFBR over a wide range of operating parameters in order to evaluate their influence on phenol mineralization and catalyst stability. Under selected operating condition (T = 90 °C, Wcat = 20 g, QL = 1.2 mL/min and [H2O2]:[Phenol] = 16.8), complete phenol conversion and remarkable TOC reduction of 90% were achieved, with a high H2O2 consumption efficiency (η = 76%) and low Fe leaching (< 3 mg/L). After 70 h of usage at different steady state conditions, the catalyst retained high mineralization levels (XTOC> 70%) but the cumulative iron loss was calculated to be c.a. 20% of the initial Fe loaded in the UFBR. The catalyst was susceptible to leaching due to the accumulation of complexing intermediates such as carboxylic acids. However, acceptable iron leaching values (< 10 mg/L) were achieved when the reactor operating conditions were properly set (55% < XTOC> 80%). The presence of chelating by-products favored also the Fe redistribution inside the catalyst pellets. Nevertheless, catalyst decay in the long-term operation was mainly due to the occurrence and permanence of chelating organic acids. This process was specially promoted by the amphoteric character of the alumina-based catalyst. However, adsorbed species were promptly eliminated by calcination at 500 °C, recovering steady state conversion profiles.

Comparison of different advanced degradation processes for the removal of the pharmaceutical compounds diclofenac and carbamazepine from liquid solutions.

Carbamazepine and diclofenac are two examples of drugs with widespread geographical and environmental media proliferation that are poorly removed by traditional wastewater treatment processes. Advanced oxidation processes (AOPs) have been proposed as alternative methods to remove these compounds in solution. AOPs are based on a wide class of powerful technologies, including UV radiation, ozone, hydrogen peroxide, Fenton process, catalytic wet peroxide oxidation, heterogeneous photocatalysis, electrochemical oxidation and their combinations, sonolysis, and microwaves applicable to both water and wastewater. Moreover, processes rely on the production of oxidizing radicals (•OH and others) in a solution to decompose present pollutants. Water radiolysis-based processes, which are an alternative to the former, involve the use of concentrated energy (beams of accelerated electrons or γ-rays) to split water molecules, generating strong oxidants and reductants (radicals) at the same time. In this paper, the degradation of carbamazepine and diclofenac by means of all these processes is discussed and compared. Energy and byproduct generation issues are also addressed.

Preparation of Cu-ZSM-5 catalysts by chemical vapour deposition for catalytic wet peroxide oxidation of phenol in a fixed bed reactor.

Cu-ZSM-5 catalysts were prepared by chemical vapour deposition for catalytic wet peroxide oxidation (CWPO) of phenol in a fixed bed reactor. Firstly, Cu-ZSM-5 catalysts with Cu loading of 0.5, 2, and 6 wt% were prepared and characterized by X-ray diffraction (XRD), N2 adsorption–desorption and X-ray photoelectron spectra (XPS). The characterization results demonstrated that CuO was uniformly dispersed on ZSM-5 with slight effect on the structure properties of the support. Then, several variables, such as the copper loading, reaction temperature, catalyst bed height and feed flow rate were investigated in the CWPO of phenol in aqueous solution at high concentration (1000 ppm). Compared with the catalyst prepared by the impregnation method, the Cu-ZSM-5 prepared by chemical vapour deposition has a better capacity of further oxidizing the intermediate organic products into carbon dioxide and water with less metal loading. Based on the Cu-ZSM-5 catalyst with Cu loading of 6 wt%, complete removal of phenol and a high TOC reduction (around 70%) have been achieved at the temperature of 80°C feed flow rate of 2 ml min−1 and catalyst bed height of 3 cm. Moreover, this catalyst maintained high catalytic activity after three runs with high phenol conversion (94%) under this optimum operating condition. Finally, the reaction mechanism was studied based on the intermediates detected by high-performance liquid chromatography (HPLC).

Catalytic wet peroxide oxidation of m‐cresol over novel Fe2O3 loaded microfibrous entrapped CNT composite catalyst in a fixed‐bed reactor

AbstractBACKGROUNDA novel iron‐loaded microfibrous entrapped carbon‐nanotube catalyst (Fe2O3‐MF‐CNT) was synthesized by wet lay‐up papermaking, sintering and metal organic chemical vapor deposition (MOCVD) processes. The catalysts were characterized by N2 adsorption–desorption isotherm, mercury porosimetry, scanning electron microscopy (FE‐SEM), energy dispersive spectroscopy (EDS) and NH3 temperature program desorption (NH3‐TPD), and the catalytic performance was tested by catalytic wet peroxide oxidation (CWPO) of m‐cresol in a fixed‐bed reactor. Finally, the probable multistep reaction pathway for CWPO degradation of m‐cresol over Fe2O3‐MF‐CNT catalyst in a fixed‐bed reactor is presented.RESULTSCharacterization results conclude that the prepared catalysts are acid catalysts containing macropores and mesopores. Active components Fe2O3 are evenly loaded on the support by the MOCVD method. CWPO results show that higher temperature and higher space time promote the catalyst performance. Meanwhile, the Fe2O3‐MF‐CNT catalyst shows perfect reusability with nearly no iron leaching concentration and high m‐cresol conversion (above 95.0%) after four successive runs (24 h). Two possible pathways during degradation of m‐cresol are presented. The hydroxyl radicals turn m‐cresols into aromatic by‐products such as p‐toluquinone, 4‐methylpyrocatechol and methylhydroquinone, followed by evolution to organic acids, and finally to carbon dioxide and water. During the reaction, more m‐cresols are degraded through the pathway in which m‐cresols are first converted into 4‐methylpyrocatechol.CONCLUSIONThe novel Fe2O3‐MF‐CNT catalyst presented herein owns the advantages of both CNTs and stainless steel fibers, and it shows promising performance in CWPO of m‐cresol. © 2018 Society of Chemical Industry

Cyclohexanoic acid breakdown by two-step persulfate and heterogeneous Fenton-like oxidation

This work reports on the application of a two-step treatment consisting of persulfate (PS) and heterogeneous Fenton-like oxidation for the breakdown of cyclohexanoic acid (CHA, 50 mg L−1) as the model naphthenic acid (NA) of oil sands process affected wastewaters (OSPWs). Home-made activated carbon and γ-alumina-supported iron (Fe/AC and Fe/γ-Al2O3) catalysts were tested for the Fenton-like step, namely Catalytic Wet Peroxide Oxidation (CWPO). The two catalysts were compared varying the H2O2 dose and temperature on the treatment efficiency and their stability was checked in terms of iron loss by leaching. The catalysts before and after reaction were characterized by 77 K N2 adsorption-desorption, TXRF and XPS analyses. Results show that over 75% mineralization can be achieved by the combined system at 80 °C. The starting pH was the circumneutral natural value of OSPWs (≈8), which during the PS-oxidation step evolved towards the acid (≈3–3.5), optimum pH for the Fenton-like systems. This, together with the partial substitution of PS by cheaper H2O2 and the consequent lower introduction of sulfate into the water are the main advantages of the combined treatment compared to PS-oxidation alone. The time course of TOC in the CWPO step can be well described by pseudo-first and pseudo-second order kinetics for the Fe/AC and Fe/γ-Al2O3 catalysts, respectively. Characterization of the fresh and used catalysts shows negligible changes in porous texture for both of the catalysts, while XPS analyses indicate an apparent decrease of the proportion of inorganic oxygen and increase of carboxylic acid group for the AC-based one. That catalyst suffered higher iron leaching and yielded less effective H2O2 consumption. The amount of oxalic acid formed, the low pH value of the solution after the PS pretreatment and the metal-support interactions in the catalysts tested are experimentally demonstrated to be the main factors affecting iron leaching.

Comparative evaluation of synthesis routes of Cu/zeolite Y catalysts for catalytic wet peroxide oxidation of quinoline in fixed-bed reactor

In order to find a better alternative of conventional aqueous ion-exchange method, several Cu/zeolite Y samples were synthesized by different routes and examined for the catalytic wet peroxide oxidation of quinoline aqueous solution in continuous fixed-bed reactor. The characterization of catalysts using ICPMS, XRD, N2 sorption, UV–vis DRS, FESEM and XPS techniques reveals the profound influence of preparation methods on synergy between copper-support interfaces. Aqueous ion-exchange (CuYAIE) and wet-impregnation (CuYIMP) methods promoted isolated Cu1+/2+ species; however, large crystallites of CuO were present on the external surface of precipitation-impregnation (CuYPI) catalyst. Interestingly, CuYPI showed hierarchical porosity and increase of surface area from 567 to 909 m2 g−1. The generation of mesoporosity in CuYPI was result of higher desilication from zeolite framework due to synergetic effect of copper and NaOH. Almost comparable mineralization (61–65%) and H2O2 stoichiometric efficiencies (44.2–45.7%) were observed for CuYAIE and CuYIMP samples. Higher catalytic activities of both catalysts in comparison to CuYPI suggest that isolated sites are the most redox-active sites for H2O2 activation and play more important role than high surface area, i.e., for CuYPI. Wet-impregnation was found better than aqueous ion-exchange method. CuYIMP exhibited high operation stability with >60% mineralization at LHSV = 4 h−1, particle size = 1.2–1.7 mm, H2O2/quinoline = 48 and T = 80 °C. Copper leaching was majorly influenced by LHSV and particle size. The system was following Eley-Rideal mechanism and kinetic parameters were calculated using model based on this mechanism.

Wet peroxide oxidation of phenol over carbon/zeolite catalysts. Kinetics and diffusion study in batch and flow reactors

New composite catalysts were synthesized by pyrolysis of carbon-containing compounds supported of Cu-substituted ZSM-5 zeolite. Three series of the catalysts containing 12 wt% of carbon and 1 wt% of copper were prepared (powder, honeycomb monolith and extruded trefoils) and characterized by TEM, XPS, N2 adsorption. Kinetics of catalytic wet peroxide oxidation (CWPO) of phenol was studied in the presence of the composite catalysts using batch and flow reactors. The substrate conversion in the batch reactor was reached 45% in two minutes over the composite catalyst but no more than 8% in five minutes over the zeolite catalyst. Studies of the granulated composites (monoliths and trefoil) in the flow reactor demonstrated a higher efficiency of the trefoil catalyst. The conversion of phenol at the flow rate 20 mL min−1 was 35% higher over the composite trefoils than over the carbon-free zeolite. The obtained kinetic data allowed the conclusion to be made about different mechanisms of CWPO over zeolite and composite catalysts. The developed kinetic model of phenol CWPO over the composite catalyst described the formation and destruction of intermediate products of phenol oxidation. It was established that inhibiting of phenol oxidation by the substrate was less pronounced in the presence of the composite catalysts than in the presence of the carbon-free catalysts. The flow reactor for phenol oxidation was modeled with account for the external and internal diffusion deceleration of the reaction over real catalyst granules of different geometry to provide adequate description of the experimental results.

Al,Fe,Ni-pillared bentonite in the catalytic wet peroxide oxidation of the textile dye Acid Yellow 99

The main goal of this work was to prove that nickel containing Al,Fe pillared bentonites have enhanced catalytic properties. The chosen test system was the catalytic wet peroxide oxidation (CWPO) the Acid Yellow 99 dye (AY99) with the initial concentration of 50 mg dm−3, the amount of H2O2 that exceeded the stoichiometric one, 60 °C, magnetic stirrer, atmospheric pressure. Bentonite was successfully pillared with AlFe and AlFeNi polyoxo cations. The chemical composition of the synthesized samples was: SiO2 56.5, Al2O3 31.3, Fe2O3 9.2; SiO2 56.4, Al2O3 31.9, Fe2O3 8.9 and NiO 0.1; SiO2 61.1, Al2O3 31.3, Fe2O3 4.8 and NiO AlFe10Ni5-PILC > AlFe5Ni5-PILC. Almost complete decolorization was achieved using all synthesized catalysts and followed first order kinetics. AlFe10Ni5-PILC induced the highest decolorization rate. Somewhat higher decolorization rate in the presence of AlFe10Ni5-PILC in comparison with AlFe5Ni5-PILC can probably be ascribed to one of the following properties or their combined effect: higher Fe content and more developed porous structure. Adsorption of AY99 on AlFe5Ni5-PILC and its degradation by H2O2 (without catalyst) were investigated in order for their influence on the decolorization of AY99, in comparison with that of CWPO using AlFe10Ni5-PILC, to be estimated. The adsorption was the least efficient, followed by degradation using H2O2 (without catalyst). CWPO was more efficient when compared to adsorption and degradation by H2O2 together. CWPO using Al,Fe,Ni-PILC can be regarded as promising method for degradation of azo dyes.

Screening of catalytic activity of natural iron-bearing materials towards the Catalytic Wet Peroxide Oxidation of Orange II

Natural materials were evaluated in the Catalytic Wet Peroxide Oxidation of a commonly used azo-compound, Orange II. Volcanic ash, black sand, pumice and Montanit300® were selected for evaluation. The materials were thoroughly characterized by several techniques (XRD, SEM/EDX, BET surface area and pore size distribution, TPD, Mössbauer spectroscopy, etc.). Peroxidation experiments were performed varying reaction temperatures (50–80 °C), catalyst loads and pH value (3–8). Complete decolouration was reached in most experiments; however, mineralization levels, peroxide consumptions and stabilities differed between materials. The activity of Fe leached during the reaction was evaluated and a combination of heterogeneous and homogeneous mechanism cannot be discarded. Thus, the materials may behave as Fe dispensers. Long-term stability experiments were also performed. While Montanit300® showed a decreased performance (20% activity reduction in 16 h) due to a higher leaching (20% Fe loss), ash and pumice performances remained almost steady at pH = 3 (Fe loss: 3% ash and 1.3% pumice).Mineralization levels obtained were outstanding (40–70%) and comparable to performances showed by more sophisticated catalysts. The use of these natural materials will optimize the Fenton process economics, since they are unexpensive, abundant and require only minimal modifications.

The preparation of Fe2O3-ZSM-5 catalysts by metal-organic chemical vapour deposition method for catalytic wet peroxide oxidation of m-cresol.

Fe2O3-ZSM-5 catalysts (0.6 wt% Fe load) prepared by metal-organic chemical vapour deposition (MOCVD) method were evaluated in the catalytic wet peroxide oxidation (CWPO) of m-cresol in a batch reactor. The catalysts have a good iron dispersion and small iron crystalline size, and exhibit high stability during reaction. In addition, the kinetics of the reaction were studied and the initial oxidation rate equation was given. Catalysts were first characterized by N2 adsorption–desorption isotherms, scanning electronic microscopy, energy-dispersive spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Results show that extra-framework Fe3+ species (presenting in the form of Fe2O3) are successfully loaded on ZSM-5 supports by MOCVD method. Performances of catalysts were tested and effects of different temperature, stirring rate, catalyst amount on hydrogen peroxide, m-cresol, total organic carbon (TOC) conversion and Fe leaching concentration were studied. Results reveal that catalytic activity increased with higher temperature, faster stirring rate and larger catalyst amount. In all circumstances, m-cresol conversion could reach 99% in 0.5–2.5 h, and the highest TOC removal (80.5%) is obtained after 3 h under conditions of 60°C, 400 r.p.m. and catalyst amount of 2.5 g l−1. The iron-leaching concentrations are less than 1.1 mg l−1 under all conditions. The initial oxidation rate equation is obtained for m-cresol degradation with Fe2O3-ZSM-5 catalysts.

Catalytic wet peroxide oxidation of benzoic acid over Fe/AC catalysts: Effect of nitrogen and sulfur co-doped activated carbon

The parent activated carbon (ACP) was modified with urea and thiourea to obtain N-doped activated carbon (ACN) and N, S co-doped activated carbon (ACNS), respectively. Iron supported on activated carbon (Fe/ACP, Fe/ACN and Fe/ACNS) were prepared and worked as catalyst for catalytic wet peroxide oxidation of benzoic acid (BA). The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscope (TEM), and their performance was evaluated in terms of benzoic acid and TOC removal. The results indicated the doped N and S improved the adsorption capacity as well as catalytic activity of activated carbon. Besides, the catalytic activity toward benzoic acid degradation was found to be enhanced by Fe/ACNS compared to that of Fe/ACP and Fe/ACN. The enhanced catalytic performance was attributed to the presence of the nitrogen and sulfur atoms may serve to improve the relative amount of Fe2+ on iron oxide surface and also help prevent leaching of Fe. It was also observed that the stability or reutilization of Fe/ACNS catalyst was fairly good.

Optimized CWPO phenol oxidation in CSTR reactor catalyzed by Al/Fe-PILC from concentrated precursors at circumneutral pH

The catalytic wet hydrogen peroxide oxidation of phenol catalyzed by an Al/Fe-PILC clay catalyst has been optimized in CSTR reactor. In order to get it more cost-effective, the process was optimized by simultaneous maximization of pollutant’s degradation and mineralization, whereas minimizing H2O2 consumption under very mild conditions of the covariates pH (4.5–11.3), temperature (5.0–25.9 °C) and input concentrations of phenol ranging 8.45–33.1 mg C/dm3 (expressed as TOC concentration); such a set of conditions resembled those typical in surface waters. A central composite statistical experimental design was developed, followed by optimization via response surface methodology with H2O2 dose (50.0–146.5% of the stoichiometric required for full oxidation) and catalyst concentration (0.5–3.0 g/dm3) as experimental factors. Covariate’s analysis showed that input TOC concentration and temperature were the most influencing ones, whereas pH did not result significant on any of the recorded responses within the assessed range (4.5–11.3). Optimal multi-response performance was achieved (65% of phenol degradation and 31% of TOC removal; 650 mg H2O2/dm3 in output stream) under stationary state with residence time of 135 min, room temperature (18 ± 1.0 °C) and neutral pH by using 1.77 g/dm3 of the clay-catalyst and tiny stoichiometric excess of the oxidizing agent (108% of the stoichiometric dose).

Catalytic wet peroxide oxidation of 4-Nitrophenol over Al–Fe PILC: Kinetic study using Fermi’s equation and mechanistic pathways based on TOC reduction

ABSTRACTThe Al–Fe pillared interlayered clay catalyst (PILC) was synthesized by pillaring bentonite clay with Al and Fe metal cations. 4-Nitrophenol (4-NP) was oxidized over Al–Fe PILC using catalytic wet peroxide oxidation process. The catalyst was characterized using X-ray diffraction, BET, wavelength-dispersive X-ray fluorescence, FTIR, and thermogravimetric analysis/derivative thermogravimetric techniques. The Al–Fe PILC was thermally stable as compared to bentonite clay. Reaction kinetics for the catalytic oxidation of 4-NP onto Al–Fe PILC was described using Fermi’s equation. Fermi’s model was fitted well to the experimental data for the degradation of 4-NP and total organic carbon (TOC) removal histories and followed pseudo-first-order rate equation. The apparent activation energies for 4-NP degradation and TOC removal histories were 21.17 and 14.12 kJ/mol, respectively. In the present study, the mechanistic pathways for the catalytic oxidation of 4-NP based upon TOC reduction have been proposed. The toxicity of 4-NP after oxidation decreased as the zone of inhibition decreased to 5 mm from 12 mm.

Exploring the activity of chemical-activated carbons synthesized from peach stones as metal-free catalysts for wet peroxide oxidation

Peach stones were used as raw material for the synthesis of activated carbons with different properties. Firstly, peach stones were chemically activated using a 12 M H3PO4 solution and carbonized under flowing air (400 °C). The obtained activated carbon, named as PS, is characterized by a high surface development (SBET = 1262 m2 g−1) and acidic character (pHPZC = 4.2). A fraction of PS was further carbonized under N2 atmosphere at 800 °C to remove surface functionalities and to increase its basicity (PS-800). In addition, a Pt catalyst supported on PS (3% w/w Pt/PS) was synthesized by incipient wetness impregnation, resulting in a considerable hydrophilicity increasing. The synthesized materials were tested in the catalytic wet peroxide oxidation (CWPO) of highly concentrated solutions of 4-nitrophenol (4-NP, 5 g L−1) during 24 h experiments, conducted at relatively mild operating conditions (T = 50–110 °C, pH = 3, catalyst load = 2.5 g L−1 and [H2O2]0 = 17.8 g L−1, corresponding to the stoichiometric amount of H2O2 needed for the complete mineralization of 4-NP). It was observed that the increase of electron-donating functionalities in PS-800 promotes the generation of reactive HO radicals, being the activity towards CWPO twice higher than that obtained with the pristine PS. Besides, increasing operating temperature substantially enhances CWPO, finding a 80% of 4-NP removal at 110 °C. On the other hand, despite the sharp increment in H2O2 decomposition due to the presence of Pt particles in Pt/PS catalyst, this decomposition is inefficient in all cases, with a consequent poor pollutant removal. This can be attributed to the recombination of HO radicals into non-reactive species −scavenging effects, promoted by the hydrophilicity of the catalyst.

Effect of Calcination Temperature on Catalytic Performance of CeCu Oxide in Removal of Quinoline by Wet Hydrogen Peroxide Oxidation from Water

A facile citric acid-mediated complexation-calcination approach is reported in this paper to prepare the CeCu oxide composite with a porous structure that is highly efficient and durable for treating simulated quinoline wastewater by catalytic wet hydrogen peroxide oxidation (CWPO). As the results indicate, Cu species can be dissolved in CeO2 lattice to fabricate a solid solution. The calcination temperature is critical for an optimum catalyst structure and catalytic performance. As found in investigating the structure and catalytic performance of the CeCu oxide prepared at calcination temperatures ranging from 350 to 750 oC, the optimum temperature is 650 oC, at which a loose surface, a porous structure and considerable adsorbed surface oxide/hydroxyl oxide species are fabricated over the catalyst. This resultant catalyst also takes on the optimal performance with an oxidation conversion reaching 98% for quinoline, a removal efficiency of 80.6% for total organic carbon (TOC) and a low Cu2+ leaching value of 19.3 mg L-1. Besides, the high performance is maintained by the catalysts in a wide pH range of 5.1-10.5. This work generally provides an efficient way to design and fabricate the catalyst for CWPO reaction, which can also be applied in other reactions.

Degrading quinoline wastewater by catalytic wet peroxide oxidation

Degrading quinoline wastewater by catalytic wet peroxide oxidation