Wet hydrogen peroxide catalytic oxidation of olive oil mill wastewaters using Cu-zeolite and Cu-pillared clay catalysts

Photochemical treatment of tyrosol, a model phenolic compound present in olive mill wastewater, by hydroxyl and sulfate radical-based advanced oxidation processes (AOPs)

The photochemical degradation and mineralization of tyrosol (TSL), a model phenolic compound present in olive mill wastewater, were studied by UV-254 nm irradiated peroxymonosulfate (PMS), hydrogen peroxide (H₂O₂) and persulfate (PS). Effects of initial TSL concentration, UV fluence, pH, phosphate buffer and presence of inorganic anions (i.e., Cl^-, SO₄^2- and NO₃^-) were also investigated. Sulfate and hydroxyl radicals were demonstrated to be responsible for TSL degradation and mineralization. Regardless of the treatment conditions, pseudo-first-order kinetics could be obtained, with the efficiencies following UV/PS > UV/H₂O₂ > UV/PMS. The better removal of TSL by UV/PS correlated with the quantum yield and concentration of sulfate radical in the system. Albeit acidic condition slightly enhanced the performance of the AOPs, complete oxidation of TSL was achieved at pH 6.8 by both UV/PS and UV/H₂O₂. Though, inorganic anions or different concentrations of phosphate buffer did not affect TSL degradation kinetics, presence of inorganic ions decreased significantly the TOC removal for both UV/PMS and UV/H₂O₂ processes. Meanwhile, UV/PS process was the least influenced by inorganic ions and showed the highest TOC removal of ∼35%. Overall, UV/PS process was the most effective for TSL degradation and mineralization in the presence or absence of common water constituents.

2D Oxide Nanomaterials to Address the Energy Transition and Catalysis

2D oxide nanomaterials constitute a broad range of materials, with a wide array of current and potential applications, particularly in the fields of energy storage and catalysis for sustainable energy production. Despite the many similarities in structure, composition, and synthetic methods and uses, the current literature on layered oxides is diverse and disconnected. A number of reviews can be found in the literature, but they are mostly focused on one of the particular subclasses of 2D oxides. This review attempts to bridge the knowledge gap between individual layered oxide types by summarizing recent developments in all important 2D oxide systems including supported ultrathin oxide films, layered clays and double hydroxides, layered perovskites, and novel 2D-zeolite-based materials. Particular attention is paid to the underlying similarities and differences between the various materials, and the subsequent challenges faced by each research community. The potential of layered oxides toward future applications is critically evaluated, especially in the areas of electrocatalysis and photocatalysis, biomass conversion, and fine chemical synthesis. Attention is also paid to corresponding novel 3D materials that can be obtained via sophisticated engineering of 2D oxides.

Kinetics of Catalytic Wet Peroxide Oxidation of Phenolics in Olive Oil Mill Wastewaters over Copper Catalysts

During olive oil extraction, large amounts of phenolics are generated in the corresponding wastewaters (up to 10 g dm^-3). This makes olive oil mill wastewater toxic and conventional biological treatment challenging. The catalytic wet peroxide oxidation process can reduce toxicity without significant energy consumption. Hydrogen peroxide oxidation of phenolics present in industrial wastewaters was studied in this work over copper catalysts focusing on understanding the impact of mass transfer and establishing the reaction kinetics. A range of physicochemical methods were used for catalyst characterization. The optimal reaction conditions were identified as 353 K and atmospheric pressure, giving complete conversion of total phenols and over 50% conversion of total organic carbon content. Influence of mass transfer on the observed reaction rate and kinetics was investigated, and parameters of the advanced kinetic model and activation energies for hydrogen peroxide decomposition and polyphenol oxidation were estimated.

Catalytic ozonation of Orange-G through highly interactive contributions of hematite and SBA-16 - To better understand azo-dye oxidation in nature

Hematite-SBA-16 mixture (HS) exhibited high catalytic activity in Orange-G (OG) ozonation in water. Total OG discoloration was achieved in half the time required with hematite or SBA-16 alone, all UV-Vis bands disappeared in less than 2 min. Liquid chromatography- Mass spectrometry (LC-MS) revealed that OG ozonation triggers via both hydroxylation and desulfonation of the aromatic rings into specific intermediates. Prolonged ozonation in the presence of hematite and SBA-16 alone resulted in different distributions of common derivatives. The latter were not detected after 25 min ozonation with HS. Stochastic modeling of the evolution in time of the UV-Vis bands of OG revealed strong binary interaction between the initial pH and catalyst concentration. This was explained in terms of reciprocal contributions of: i. the catalytic properties of hematite in spite of its low porosity; ii. the high specific surface area of SBA-16 for adsorption and surface reaction notwithstanding its low intrinsic catalytic activity. The weak basicity of SBA-16 surface seems to play a key-role in adsorption. These findings are of great interest for envisaging flexible oxidative treatments, where Fe³⁺ containing soils or mixtures of sand and rust may also act as catalyst for total mineralization of various azo-dyes, regardless to their structures.

Total mineralization of sulfamethoxazole and aromatic pollutants through Fe2+-montmorillonite catalyzed ozonation

The catalytic activity and selectivity of montmorillonite exchanged with Na(+), Fe(2+), Co(2+), Ni(2+) and Cu(2+) cations were comparatively investigated in the ozonation of sulfamethoxazole (SMX). Chlorobenzene, benzoic acid, 4-nitrobenzoic acid, 3-hydroxybenzaldehyde, 4-nitrophenol and phenol were used as probe molecules having structural similarity with SMX oxidation intermediates. UV-vis spectrophometry and chemical oxygen demand (COD) measurements showed that Fe(II)-Mt and, to a lesser extent, Co(II)-Mt produce total mineralization of all organic substrates in less than 40 min. Combined HPLC-mass spectrometry revealed a reverse proportionality between the degradation time and molecular size of the organic substrates. Oxalic acid was recognized as a common bottleneck in the ozonation of any organic substrates. Ozonation initially obeyed a first order kinetics, but adsorption took place after 3-5 min, inducing changes in the mechanisms pathways. These findings may be useful for tailoring optimum oxidative treatment of waters without accumulation of hazardous derivatives.

Use of clinoptilolite to improve and protect soil quality from the disposal of olive oil mills wastes

In the framework of LIFE07 ENV/GR/000280 Project "Strategies to improve and protect soil quality from the disposal of olive oil mills wastes in the Mediterranean-PROSODOL", a laboratory experiment was conducted in order to investigate to which extent the natural zeolite clinoptilolite is capable of limiting environmental degradation caused by the uncontrolled disposal of olive oil mills wastes (OOMW). Clinoptilolite was added in various ratios (from 0% up to 30%w/w) to soil samples, which were collected from four OOMW disposal sites (from both the interior of the disposal ponds and the surroundings) located in a pilot Municipality in Rethymno, Crete, Greece. Water soluble K, Ca, Mg, Mn, Zn, Fe, Cu, polyphenols, NO3-, Cl-, SO4(2-) and PO4(3-) were measured in leachates after equilibration of the soil samples with clinoptilolite It was observed that water soluble K, NO3-, Cl-, SO4(2-) and polyphenols were decreased with an increase in zeolite percentage; Ca leaching was slightly increased or remained nearly constant; Mg leaching remained constant or increased, especially for pond soils; and PO4(3-) leaching was very low. Although the soil samples' content in available Mn, Cu, Zn, Fe was high, the metals were not detected in the leachates.

Properties of iron-based mesoporous silica for the CWPO of phenol: a comparison between impregnation and co-condensation routes

Iron-based mesoporous silica materials were prepared according to different impregnation and co-condensation procedures. Several complementary techniques, including XRD, TEM/EDX and nitrogen sorption isotherms were used to evaluate the final structural and textural properties of the calcined Fe/SBA-15 materials. While Fe(2)O(3) isolated particles of which the size is close to the silica pore diameter ( approximately 7-8 nm) were obtained using classical wet impregnation procedure, smaller iron oxide particles ( approximately 2-4 nm) homogeneously dispersed within the hexagonal pore structure of the SBA15 host support were generated by self-combustion of an impregnated iron-glycinic complex. By contrast, the various co-condensation routes used in this work were less efficient to generate iron oxide nanoparticles inside the silica mesopores. Catalytic performances of the materials were evaluated in the case of total phenol oxidation by H(2)O(2) in aqueous solution at ambient conditions. Large differences in terms of catalytic activity and iron species stability were observed. While the impregnated solids proved to be the most active catalysts (highest Fe(2)O(3) nanoparticles dispersion), iron leaching was observed in aqueous solution, accounting for a homogeneous catalytic contribution. In contrast, the co-condensed samples exhibiting larger iron oxide clusters stabilized over the silica surface proved more efficient as active sites in Fenton catalysis.

Evaluating the photo-catalytic application of Fenton's reagent augmented with TiO(2) and ZnO for the mineralization of an oil-water emulsion

In the present study, homogenous (photo-Fenton) and heterogeneous photo-assisted systems (Fenton/TiO(2)/UV, Fenton/ZnO/UV and Fenton/TiO(2)/UV/Air) were investigated for the treatment of a diesel-oil wastewater emulsion. The augmentation of the photo-Fenton process by heterogeneous TiO(2) increased the reaction rate, in terms of COD reduction efficiency from 61% to 71%. Furthermore, the COD removal efficiency was increased to 84% when air was bubbled through the reactants. However, if the Fenton/TiO(2) /UV/Air process is to be utilized as a treatment for this wastewater, the separation of the TiO(2) from the treated effluent would need further consideration.

Heterogeneous catalytic degradation of phenolic substrates: catalysts activity

This review article explored the catalytic degradation of phenol and some phenols derivates by means of advanced oxidation processes (AOPs). Among them, only the heterogeneous catalyzed processes based on catalytic wet peroxide oxidation, catalytic ozonation and catalytic wet oxidation were reviewed. Also selected recent examples about heterogeneous photocatalytic AOPs will be presented. In details, the present review contains: (i) data concerning catalytic wet peroxide oxidation of phenolic compounds over metal-exchanged zeolites, hydrotalcites, metal-exchanged clays and resins. (ii) Use of cobalt-based catalysts, hydrotalcite-like compounds, active carbons in the catalytic ozonation process. (iii) Activity of transition metal oxides, active carbons and supported noble metals catalysts in the catalytic wet oxidation of phenol and acetic acid. The most relevant results in terms of catalytic activity for each class of catalysts were reported.