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The intercalation of pyrazolone-based oxalamide metal complexes into Na-montmorillonite (Na-MMT) for catalytic liquidphase oxidation of phenol using H2O2 was undertaken by a flexible ligand method using metal ions including Mn(II), Zn(II), and Sn(II). First, the metal ions were exchanged with the sodium ions of Na-MMT, and then these metal ions were complexed with a new pyrazolone-based oxalamide ligand. The intercalated metal complexes were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, elemental analysis, and thermogravimetric analysis. Phenol was successfully oxidized by heterogeneous catalysts based on Mn(II), Zn(II), and Sn(II) pyrazolone-based oxalamide complexes intercalated into Na-MMT. These heterogeneous catalysts catalyze the liquid-phase oxidation of phenol using H2O2 to catechol as the major product and hydroquinone and benzoquinone as the minor products. The Mn(II) and Zn(II) complexes intercalated into Na-MMT showed better activity than the Sn(II) complex intercalated into Na-MMT and the reaction without the catalyst. It has been shown that some metal ion complexes intercalated into Na-MMT are active catalysts for liquid-phase oxidation of phenol with hydrogen peroxide. [ABSTRACT FROM AUTHOR]

The intercalation of pyrazolone-based oxalamide metal complexes into Na-montmorillonite (Na-MMT) for catalytic liquidphase oxidation of phenol using H2O2 was undertaken by a flexible ligand method using metal ions including Mn(II), Zn(II), and Sn(II). First, the metal ions were exchanged with the sodium ions of Na-MMT, and then these metal ions were complexed with a new pyrazolone-based oxalamide ligand. The intercalated metal complexes were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, elemental analysis, and thermogravimetric analysis. Phenol was successfully oxidized by heterogeneous catalysts based on Mn(II), Zn(II), and Sn(II) pyrazolone-based oxalamide complexes intercalated into Na-MMT. These heterogeneous catalysts catalyze the liquid-phase oxidation of phenol using H2O2 to catechol as the major product and hydroquinone and benzoquinone as the minor products. The Mn(II) and Zn(II) complexes intercalated into Na-MMT showed better activity than the Sn(II) complex intercalated into Na-MMT and the reaction without the catalyst. It has been shown that some metal ion complexes intercalated into Na-MMT are active catalysts for liquid-phase oxidation of phenol with hydrogen peroxide. [ABSTRACT FROM AUTHOR]

Present study deals with the simulation of the Fenton's process for the removal of phenol using ASPEN-Plus. The effect of phenol concentration, catalyst loading, mole ratio of H2O2 to iron ion, and temperature on the phenol degradation rate has been studied using the developed process flow diagram. The result shows higher flow rate of hydrogen peroxide (4.2 kmol/h) favours phenol degradation (98%) since the hydroxyl radical availability rises. Increase in catalyst loading (186 g) and rise in mole ratio of hydrogen peroxide to iron ion (~1) improves the removal of phenol (~97%) from wastewater since the hydroxyl radical formation improves and thus affect the mechanism and chemical kinetics of Fenton reaction. Increase in temperature improves the degradation, however high temperature above optimum condition (32.5°C) does not favour the degradation of phenol. [ABSTRACT FROM AUTHOR]

• Oxidation catalysts based on dioxidovanadium(V) and ethyl maltol, deferiprone or maltol ligands. • Hydroxylation of phenol to dihydroxybenzene products with H 2 O 2. • Olefin epoxidation with a 100 % selectivity at RT in absence of organic solvents. • Recyclable catalysts for olefin epoxidation. The facile synthesis and structural characterization of a set of three new oxidovanadium(V) complexes of general formula [VO 2 (L)(diimine)], where L is ethyl-maltol(emal) (1), deferiprone(def) (2) or, maltol(mal) (3), and diimine is 5,6-dimethyl-1,10-phenanthroline(5,6-DMP) are described. The neutral complexes 1–3 have been comprehensively characterized by employing various analytical and spectroscopic techniques including single crystal X-ray diffraction analysis. The coordination geometry around the V(V) in each of the complexes was indicated by XRD-analysis to be distorted octahedral with equatorial plane being occupied by the deprotonated O,O-donor ligands. The complexes 1 – 3 could be successfully implemented in organic oxidations viz., hydroxylation of phenol (PH) and olefin epoxidation under environmentally clean organic-solvent-free conditions with aqueous H 2 O 2 as oxidant. Phenol was selectively converted into dihydroxybenzene (DHB) products, catechol (CT) and hydroquinone (HQ) (HQ/CT=1.3:1) with aqueous H 2 O 2 as oxidant at room temperature, with a TON value of 266. Moreover, the catalysts showed impressive activity in epoxidation of styrene and a range of cyclic olefins such as cyclohexene, cyclooctene, and norbornene in absence of organic solvent, to provide high conversion (up to 100 %) with excellent epoxide selectivity and good TON values. The catalysts are stable and afford recyclability for multiple cycles of epoxidation with virtually unaltered catalytic activity. Dioxidovanadium(V) complexes comprising of ethyl maltol, deferiprone or maltol and diimine ligands were synthesized. The complexes efficiently catalyzed H 2 O 2 -induced phenol hydroxylation and alkene epoxidation under organic solvent-free eco-friendly reaction condition. [Display omitted] [ABSTRACT FROM AUTHOR]

Commaille discovered that the toxic principle present in the roots of the thistle Atractylis gummifera was a glucoside of atractylic acid and described the physiological damage it caused in humans and in animals. He also showed that the natural potassium atractylate was exactly equal to the potassium myronate present in mustard seed. He measured the solubility of caffeine in several solvents at two temperatures and determined the composition of Mysore coffee. One important result was the difference between the extracts with cold and with hot water: The latter dissolved most of the phosphates present in the grain. Together with Millon they made a detailed analysis of milk and in doing so discovered a new protein, which they named lactoprotein. They also isolated casein and prepared a large number of its derivatives. Commaille carried a detailed analysis of the seeds of white and black mustard and proved that the latter contained its thiocyanic acid combined with the allyl group. He also developed a fast and precise method for determining the amount of astringent substance contained in a particular body. He also established a fast and high yielding procedure for preparing the dye coralline by oxidation of phenol with sulfuric and oxalic acid. [ABSTRACT FROM AUTHOR]

Chloroperoxidase (CPO) is a hybrid of two different families of enzymes, peroxidases and P450s. However, it is poorly understood on CPO's multiple catalytic functions. Herein, phenol was selected as a model substrate to investigate the multiple catalytic roles of CPO. Results showed that phenol was readily transformed into a variety of brominated organic compounds (BOCs) via the CPO-mediated oxidative process. A total of 16 BOCs were identified using gas and liquid chromatography coupled with mass spectrometry. Possible reaction pathways could be attributable to four CPO-mediated processes, including bromination, radical coupling, intramolecular cyclization and debromination. Higher bromide concentrations and lower pH conditions both facilitated the formation of brominated products. While a higher bromination capacity was observed in pH 3.0 solutions, CPO-mediated radical couplings were more favorable at pH 5.0 and 6.0. Although CPO might catalyze chlorination when chloride and bromide coexisted in the solution, BOCs were the dominant products of CPO-mediated phenol oxidation. Results of this study suggest that various catalytic roles of CPO may contribute to the biotic formation of BOCs in the natural environment. Image 1 • Brominated organic compounds were formed from CPO-mediated oxidation of phenol. • The products included OH-PBDEs, OH-PBBs, and PBDD/Fs. • The reaction may involve bromination, radical coupling, intramolecular cyclization, and debromination. • CPO had preferential catalytic activities under different pH conditions. • In the coexistence of bromide and chloride, BOCs were the dominant products. [ABSTRACT FROM AUTHOR]

Abstract A simple and direct low-temperature hydrothermal synthesis approach (100 °C) has been developed to encapsulate Pd nanoparticles (ca. 2.3 nm) within nano-sized mesoporous TS-1 zeolite by utilizing dichloro(ethylenediamine)palladium (DEAP) and cetyltrimethylammonium bromide (CTAB) as palladium source and mesoporogen, respectively. It's demonstrated that the aging process of the mother liquid and low-temperature hydrothermal treatment can effectively inhibit the premature precipitation of metal precursor and thus the successful encapsulation of Pd nanoparticles into mesoporous TS-1 nanocrystals, so that the frequently occurring of Pd nanoparticle aggregation at high temperature was expectedly avoided. Consequently, the as-synthesized catalysts with highly thermal stability and mesoporous channels exhibit excellent catalytic activity and recyclability in the oxidation of CO with relatively low Pd content (0.53 wt% Pd) and catalytic wet air oxidation of phenol (66.2% of phenol conversion, 100 °C). Graphical abstract Image 1 Highlights • We report a direct synthesis of Pd encapsulated mesoporous TS-1 zeolite via low-temperature hydrothermal treatment. • The optimized synthesis condition (mesoporogen amount, temperature and time of hydrothermal treatment) are studied. • The small-sized Pd nanoparticles (2.3 nm) in mesoporous TS-1 show high stability at 600 °C under air/N 2 /H 2 atomsphere. • The hierarchical micro/mesoporous stucture endow the nano-sized TS-1 zeolite high mass transportation efficiency. • Excellent catalytic activities and recyclabilities of catalyst in the CO oxidation and wet air oxidation of phenol. [ABSTRACT FROM AUTHOR]

• The role of nitrite ions in electrochemical oxidation was initially examined. • Nitrated by-products from anodic oxidation of phenol were investigated. • The generation of nitrogen dioxide radicals was favored in nitrite-rich systems. • The detailed formation pathways of nitrated by-products were proposed. • The degradation of phenol in nitrate media mainly occurred via OH pathways. Using boron-doped diamond (BDD) to mineralize recalcitrant organics has been one of the hottest areas of research interest in the field of water treatment. Here we report for the first time that, in the presence of nitrite ions (NO 2 −), the anodic oxidation of phenol with BDD electrode will lead to the formation of nitrated by-products of phenol. These by-products include 2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol, 2,6-dinitrophenol, 2,4,6-trinitrophenol, 2,3,4,6-tetranitrophenol, 2,3,4,5,6-pentanitrophenol, as well as a large number of dimers and trimers of nitrophenols. Increasing the concentration of NO 2 − will not only greatly affects the degradation and mineralization of phenol, but also enhances the formation of nitrophenols. The nitrated by-products are mainly generated via electrophilic substitution reactions mediated by nitrogen dioxide radicals and hydroxyl radicals, as well as via coupling reactions of phenol. In addition, it is found that several simple nitrophenols may also be formed in nitrate media. As a whole, formation of nitrated by-products is a novel phenomenon in anodic oxidation processes. Since nitrated aromatics are well known for their persistence in the environment, their formations in BDD anode cells should be carefully scrutinized before such technology is applied to groundwater remediation. [ABSTRACT FROM AUTHOR]

The electrochemical behaviour of cefadroxil, a first-generation β-lactam antibiotic, was studied at glassy carbon electrodes in aqueous media over a wide range of pH. The first oxidation process is of the phenol moiety and follows an ECE mechanism, generating catechol and resorcinol derivatives as sub-products, which are then reduced and oxidized in subsequent cycles. The sulphur heteroatom present in the cyclic structure close to the β-lactam moiety is oxidized in two steps generating sulphoxide and sulphone. This process was identified from direct comparison with amoxicillin, which has a similar molecular structure, although they belong to different classes of β-lactam antibiotics. For amoxicillin, oxidation of the sulphur heteroatom occurred at more positive potentials, most likely due to structural difficulties in stabilizing the charged oxidized species. Formation of a complex between copper (II) and each of the antibiotics was studied by cyclic voltammetry. Finally, determination of cefadroxil in commercial samples was successfully carried out. • Electrochemical characterization of cefadroxil at glassy carbon in aqueous media • Oxidation of the phenol moiety by ECE mechanism generating catechol and resorcinol • Comparison between electrochemical profile of cefadroxil and amoxicillin • The phenol oxidation process was used to obtain a limit of detection of 0.3 μM. • Phenol oxidation was used to measure the amount of cefadroxil in commercial samples. [ABSTRACT FROM AUTHOR]

One of the usual ways to degrade phenol contaminant is sulfate radical-based advanced oxidation processes (SR-AOPs). In this study, reactive sulfate radicals have been produced by Co3O4/Fe3O4@nSiO2@mSiO2 catalyst and Fe3O4 nanoparticles. It has been found that the couple of supported cobalt catalyst and peroxymonosulfate (PMS) is highly effective to produce sulfate radicals for phenol oxidation. In contrary to, Fe3O4-PMS system displays much low phenol degradation, and Co3O4/Fe3O4@nSiO2@mSiO2 catalyst shows a good catalytic performance in solution. The properties of this supported catalyst have been characterized by XRD (powder X-ray diffraction), SEM–EDS (scanning electron microscopy–energy-dispersive X-ray spectroscopy), TEM (transmission electron microscopy), and nitrogen adsorption–desorption. This magnetic catalyst is facility separated from the medium by an external magnetic field. Finally, three different methods involving annealing in the air, washing with water and applying ultrasonics was used for regenerating the deactivated catalyst. The heat treatment can recover the catalyst nearly. [ABSTRACT FROM AUTHOR]

• The photooxidation of organic pollutants is achieved with the simultaneous reduction of Cr(VI). • The intermediates of phenol oxidation significantly contribute to Cr(VI) removal. • The redox couple of Fe3+/Fe2+ works as a homogeneous photocatalyst. The sustained oxidation of aqueous organic pollutants using hydroxyl radicals (HO) generated in the UV-irradiated solution of ferric ions was investigated in the presence of Cr(VI). The synergistic effect of simultaneous 4-chlorophenol (4-CP) oxidation and Cr(VI) reduction is explained in terms of the various roles of OH radical, degradation intermediates, and Fe3+/Fe2+ redox cycle. The photolysis of FeIII(OH)2+ generates OH radical which degrades the organic substrate. The reduction of Cr(VI) was inhibited by the OH radical-induced re-oxidation of Cr(III) in the absence of 4-CP. The complete removal of Cr(VI) was achieved only in the presence of phenolic substrates which not only reacts with OH radical (hence inhibiting the reoxidation of Cr(III)) but also generates reducing intermediates which effectively reduce Cr(VI). Fe2+ also converted Cr(VI) to Cr(III) with regenerating Fe3+, which makes the overall process photocatalytic. The photocatalytic activity for the simultaneous removal of 4-CP and Cr(VI) was largely maintained up to five cycles. Such simultaneous and synergic photoactivity was also observed for other phenolic compounds (4-bromophenol, 4-nitrophenol, phenol). The simultaneous and synergic removal of phenolic compounds and Cr(VI) can be enabled through the redox couple of Fe3+/Fe2+ working as a homogeneous photocatalyst. [ABSTRACT FROM AUTHOR]

To mitigate the drawback of the short service life of titanium-based SnO 2 electrodes, we prepared Ti/SnO 2 Sb La electrodes by the sol-gel method with two kinds of Ce Mn and Fe Mn composite intermediate layers, a Mn intermediate layer, or no intermediate layer. The surface structure and morphology of the prepared electrode coating were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), and the influence of the composite intermediate layer on the electrochemical performance of the electrode and the electrocatalytic oxidation of phenol were analysed by cyclic voltammetry, anodic linear voltammetry, AC impedance spectroscopy and Mott-Schottky curve tests; additionally, accelerated lifetime tests were performed for electrodes with different intermediate layers. The experimental results show that, compared to electrodes with the Mn interlayer or no intermediate layer, the electrode with the Ce Mn composite intermediate layer had markedly improved electrochemical performance and oxygen evolution potential, and the highest oxygen evolution potential could reach 1.84 V. Moreover, the capacity for electrocatalytic oxidation degradation of phenol was enhanced to some degree, with the highest removal rate of phenol reaching 93.6% after treatment for 180 min, and the maximum removal rate of COD can reach 77.92%. In the process of degrading phenol, the cell voltage of the electrode is kept to a minimum, and the stability is maximized. Accelerated lifetime testing showed that, compared with that of the no-intermediate-layer electrode, the lifetime of the electrode with the Ce Mn composite intermediate layer was increased 5-fold, with the longest lifetime reaching 85 min. Therefore, the Ce Mn composite intermediate layer can effectively improve the service life of electrodes based on titanium and tin. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • MW radiation mode plays a key role in MW-CWPO. • MW pulsation reaches higher mineralization degree and better H 2 O 2 exploitation. • Energy consumption can be reduced to one third by using the correct strategies. • MW-CWPO is competitive in terms of energy consumption with other intensified AOP. Abstract Over the past few years, microwave technology (MW) has been successfully coupled to different advanced oxidation processes for wastewater treatment. This intensification method provides a rapid and homogeneous heating and, in presence of microwave absorbing materials, hot spots can be generated. These have shown a significant contribution on the overall efficiency of the process. Up to the date, there is no information on the influence of the radiation mode on the system. To gain knowledge on this issue, three different operation modes were studied in the MW-assisted catalytic wet peroxide oxidation of phenol: (i) controlled temperature (120 °C), (ii) controlled continuous MW and (iii) controlled pulsated MW. Other experimental conditions were [Phenol] 0 : 100 mg·L−1, [H 2 O 2 ] 0 : 500 mg·L−1, [graphite]: 500 mg·L−1, pH 0 :3. The pulsated method reached 90% mineralization degree and complete H 2 O 2 decomposition using 240 kJ, three times less energy than the controlled temperature run. Continuous MW showed a slightly inferior performance (X TOC : 82%), ascribed to a worse energy dissipation from the hot spots on the material. After reaction, only biodegradable short chain carboxylic acids remain in the effluent and there are no significant modifications on the catalyst crystallinity, despite the extreme conditions produced by hot spot formation. Under these conditions TOC abatement follows a pseudo-second kinetic order (E A,TOC ≈ 30–40 kJ·mol−1), whereas H 2 O 2 decomposition fits by a pseudo-first order (E A,H2O2 ≈ 33–52 kJ·mol−1). Additionally, the specific energy consumption (EC TOC) for the controlled power runs was lower than that of other intensified AOP, making MW-CWPO a competitive technology for wastewater treatment. [ABSTRACT FROM AUTHOR]

To study the correlation between crystal facets and oxygen vacancies, three kinds of ceria samples with various crystal facets, cube [100], rod [110] and octahedron [111], were prepared. For further comparison, two kinds of ceria samples with [110] facets (20–30 nm rod and 5–8 nm filiform) were also constructed. The morphology, crystal structure, surface composition, reducibility and oxygen defects of the prepared samples were characterized by SEM, XRD, N2 adsorption–desorption, H2-TPR, XPS and EPR, respectively. The results showed that the surface oxygen defect contents of the samples followed the order: CeO2–F > CeO2–C > CeO2–R > CeO2–O, indicating that the content of oxygen vacancies is closely related on the crystal facets. The catalytic performance of the samples are all in line with that of the Oads/Olatt ratios, suggesting that crystal facets play a crucial role on surface oxygen vacancies and phenol oxidation of the ceria samples. Furthermore, although the CeO2–R sample (rods) and the CeO2–F sample (filiform) are mainly enclosed by [110] facets, the CeO2–F showed better catalytic performance than that of CeO2–R, revealing that the phenol oxidation not only depends on the crystal facets of CeO2 but also with its surface oxygen vacancy contents. [ABSTRACT FROM AUTHOR]

Zeolite Y was synthesized by hydrothermal method with adding Fenton's reagent. The materials were characterized by X-ray powder diffraction (XRD) and the crystallization kinetics was investigated. The results showed that hydroxyl free radical (∙OH) produced by Fenton's reagent accelerated both the nucleation process and the crystal growth process of zeolite Y. The apparent nucleation activation energy (E n) and apparent growth activation energy (E g) with Fenton's reagent were 67.98 and 42.66 kJ/mol, respectively. Compared with traditional synthesis of zeolite Y, the synthesis adding moderate Fenton's reagent presented shorter induction period, faster nucleation and growth rate, and lower apparent activation energy. In addition, iron was incorporated into the zeolite at the same time and the material showed high catalytic performance for photo-Fenton-like oxidation of phenol. The crystallization process of zeolite Y was promoted by the addition of Fenton's reagent. Image 1070 • FeY zeolite has been rapidly prepared with adding Fenton's reagent. • The crystallization kinetics of the zeolite is studied. • ∙OH promotes the nucleation and crystal growth of FeY zeolite. • FeY zeolite has high catalytic performance in phenol degradation. [ABSTRACT FROM AUTHOR]

• A straightforward method for synthesizing ortho -naphthoquinones were discovered by using easily available Cobalt-Schiff base complex. • The ortho -naphthoquinones showed potent biological activity for the treatment of AML. • Compound 4h represents a potential scaffold to optimize the production of a treatment for AML. A straightforward method for synthesizing ortho -naphthoquinones was identified using an easily available cobalt–Schiff base complex. Efficient oxidation of phenols to ortho -naphthoquinones was useful in obtaining compounds with potent biological activity for the treatment of acute myeloid leukemia (AML). Among these compounds, the compound 4h effectively inhibited the proliferation of different AML cell lines in vitro. Further in vivo antitumor studies indicated that 4h at 40 mg/kg/d led to tumor regression in led to tumor regression in an MV4-11 xenograft model without evident toxicity. The cobalt-Schiff base complex was found to be an efficient catalyst in the transformation of phenols to ortho -quinones, and the compound 4h represents a potential scaffold to optimize the production of a treatment for AML. [ABSTRACT FROM AUTHOR]

Distinct three-dimensional hierarchically stacking SnO2-Sb/TiO2-NTs electrode with a good-adhesion TiO2-NTs@SnO2-Sb interlayer, a compact plate SnO2-Sb middle layer, and an apparent uniform microsphere layer was successfully prepared through the hydrothermal method. The evolution of micro-morphology and structure of electrode catalyst layer was realized so as to improve the catalytic performance of electrode through tuning the hydrochloric acid concentration. Experimental results show that SnO2-Sb/TiO2-NTs electrode prepared in 0.5 mol L−1 HCl condition possesses the optimal performance containing a low phenol oxidation potential of 1.2 V (vs. SCE), and a maximum current density of 3.8 mA cm−2 towards phenol degradation in phosphate buffered solution. The electrochemical phenol removal results show that the phenol degradation process coincides with the first-order kinetics and the corresponding optimal constant reaches 14.2 × 10−3 min−1. The TOC removal efficiency of optimal electrode reaches 62%. Graphical abstract The evolution of micro-morphology and structure of electrode was realized through tuning the hydrochloric acid concentration so as to improve the catalytic performance of electrode. [ABSTRACT FROM AUTHOR]

Abstract In this study, ferrate intercalated Ca/Al-layered double hydroxide (Ferrate-LDH) was synthesized and characterized for water treatment. In the new Ferrate(VI) material, ferrate was stably present in the LDH interlayers, in agreement with results of the Density Functional Theory simulation. The oxidative capability of Ferrate-LDH was examined in terms of the mineralization of phenol in water. The Ferrate-LDH could achieve up to 86.8% utilization efficiency during oxidative destruction of phenol in water (pH = 6.5, TOC = 38.3 mg/L), advantageous over direct ferrate addition that only achieved 12.6% utilization efficiency. A slower evolution of dioxygen (a final product of Ferrate(VI) self-decay) was observed in the Ferrate-LDH water system, suggesting that the LDH structure inhibited Ferrate(VI) self-decay. Therefore, the better phenol removal achieved by Ferrate-LDH was likely ascribed to an increased oxidant exposure caused by the increased lifetime of Fe(VI) in water. Characterization of the LDH products before and after oxidation of phenol revealed that ferric (hydr)oxides capable of surface catalyzing Ferrate(VI) self-decay were formed on the LDH surface, not inside the LDH interlayers, suggesting that ferric(III), the product of Fe(VI) reduction, was repelled from the LDH interlayers. Isolation of Fe(VI) present in the LDH structure from these active iron products may be responsible for the inhibited Ferrate(VI) self-decay when Ferrate-LDH was dosed to water. This study demonstrates that the intercalation of ferrate in LDH represents a promising approach to more efficiently and economically utilizing Ferrate(VI) for the elimination of water pollutants. Graphical abstract Unlabelled Image Highlights • The oxidant exposure of Fe(VI) was increased by its intercalation into CaAl-LDH • Stable Fe(VI) was achieved in LDH in agreement with DFT simulation result • The utilization rate of Fe(VI) in LDH was 7 times higher than that with Fe(VI) alone • Ferric (hydr)oxides from Ferrate(VI) reduction were aggregated on the LDH surface • Utilization of Fe(VI) was improved in LDH interlayer than that in solution [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Carbon materials are active in MW-CWPO, combining redox properties and hot spots. • Surface chemistry has a key role in the activity, especially for graphites. • The structure of the materials affects their stability. • AC crumbles down by hot spot formation inside micropores, causing a pop-corn effect. • Graphitic layered structure allows heat dissipation, enhancing catalyst stability. Abstract Several commercial carbon materials have been tested as catalysts in the Microwave-assisted Catalytic Wet Peroxide Oxidation process (MW-CWPO). Two graphites (G-F and G-S), two activated carbons (AC-M and AC-C), two carbon blacks (CB-V and CB-A) and silicon carbide (SiC) were selected due to their MW-absorbing properties. Phenol (100 mg L−1) was used as target pollutant, operating in batch at pH 0 3, 120 °C, 500 mg L−1 catalyst load and the theoretical stoichiometric amount of H 2 O 2 (500 mg L−1). All carbon materials showed to be active in terms of H 2 O 2 decomposition and phenol oxidation. Nonetheless, G-S and AC-M stood out as the most active materials in terms of TOC removal, with values of 94 and 93% TOC elimination, respectively. On the other hand, both carbon blacks and G-F yielded a significantly lower TOC degradation. Surface chemistry seems to rule the activity of graphites, in particular the pH slurry (4.5 for G-S and 8.4 for G-F). The most active catalysts, G-S and AC-M were used in 5 consecutive cycles in order to study their stability. While G-S remained active, AC-M. [ABSTRACT FROM AUTHOR]

Catalysts of Ru and Ru−Au prepared by the wet impregnation and Deposition‐Precipitation methods supported on ZrO2 modified by CeO2(10 and 20 wt%) synthetized by sol‐gel method, in order to study Au and CeO2 addition effect in the catalytic wet air oxidation of phenol, carried out in an automatized continuous fixed‐bed reactor using oxygen as an oxidizing source. Characterizations of the catalysts were made by X‐ray Diffraction (XRD), Specific Surface Area (BET), X‐ray Photoelectron Spectroscopy (XPS), Transmission Electronic Microscopy (TEM), Scanning Electronic Microscopy (SEM), Ultraviolet–visible Spectroscopy (UV‐vis) and Temperature Programmed Desorption of Ammonia (NH3‐TPD). The effect of Au is reflected in the selectivity to CO2 of the catalysts Ru‐ZrO2 and Ru−Au‐ZrO2 with the increase in selectivity from 89 to 95% related to the increase in acidity which increases from 70 to 102 (μmol of NH3/ gCat). Ce loading effect in this case was important to the enhance the CO2 selectivity explained by the formation of Ce4+‐O2−‐M that could favor the oxygen transfer between the catalyst surface and the adsorbed species by a redox mechanism. This study highlights the importance of the CWAO process for pollutants such as phenol at high concentrations in continuous reactors using catalysts, that increase the selectivity towards CO2 (complete mineralization) reaching the 100% for Ru/ZrO2‐CeO2 20 wt%, Ru−Au/ZrO2‐CeO2 10 wt% and Ru/ZrO2‐CeO2 20 wt% catalysts studied and the removal of the pollutant from the effluent, which in our case, reached 64.6% with the monometallic catalyst Ru/ZrO2‐CeO210 wt%. [ABSTRACT FROM AUTHOR]

The article investigates kinetics of electrocatalytic oxidation of phenol in the solution of sodium sulfate on a platinum electrode in the presence of dispersed oxides of metals of varied valence. It is shown that the degree of phenol oxidation in the presence of oxides increase by 10–15%. The most active catalysts include oxides of cobalt, chromium, copper and titanium, whose catalytic activity diminishes in the series Co3O4 > Cr2O3 > Cr2O3 > TiO2 > CuO; the rate of electrooxidation of phenol increases at a decrease of anolyte. It was shown that a limiting stage of electrochemical oxidation of phenol in aqueous solutions with the concentration 50 mg/dm3 is a diffusion of the substance to the electrode. [ABSTRACT FROM AUTHOR]

The necessity to remove organic pollutants from the industrial wastewater streams has forced the development of new technologies that can produce better results in terms of pollutant removal and process efficiency in combination with low investment and operating costs. One of the new emerging processes with a potential to fulfil these demands is catalytic wet peroxide oxidation, commonly known as the CWPO process. The oxidative effect of the hydrogen peroxide is intensified by the addition of a heterogeneous catalyst that can reduce the operating conditions to atmospheric pressure and temperatures below 383 K. Zeolites, among others, are especially appealing as catalysts for selective oxidation processes due to their unique characteristics such as shape selectivity, thermal and chemical stability, and benign effect on nature and the living world. In this work, catalytic activity, selectivity and stability of Cu/Y-5 zeolite in phenol oxidation with hydrogen peroxide was examined. Catalyst samples were prepared by ion exchange method of the protonic form of commercial zeolite. The catalysts were characterized with powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and AAS elemental analysis, while the adsorption techniques were used for the measurement of the specific surface area. The catalytic tests were carried out in a stainless steel Parr reactor in batch operation mode at the atmospheric pressure and in the temperature range from 323 to 353 K. The catalyst was prepared in powdered form and the mass fraction of the active metal component on the zeolite was 3.46 %. The initial concentration of phenol solution was equal to 0.01 mol dm−3 and the concentration of hydrogen peroxide ranged from 0.01 to 0.10 mol dm−3. The obtained experimental data was tested to a proposed kinetic model for phenol oxidation r = k1 cF cVP and hydrogen peroxide decomposition rHP = k2 cHP. The kinetic parameters were estimated using the Nelder-Mead method of nonlinear regression. On the basis of the obtained results of characterization process and conducted catalytic tests, the following can be observed. Zeolite structure of the prepared catalyst was confirmed through powder X-ray diffraction, scanning electron microscopy and adsorption techniques. Their catalytic performance was monitored in terms of phenol and total organic carbon (TOC) conversions, hydrogen peroxide decomposition, by-product distribution and degree of copper leached into the aqueous solution. The obtained experimental results indicate that in the space of 180 minutes, the use of these catalysts allows almost total elimination of phenol and significant removal of total organic carbon content with the use of small amounts of catalyst (0.1 g dm–3) and substoichiometric level (71.4 %) of oxidant required for complete oxidation of organic pollutant. The main product among aromatics was catechol, followed by hydroquinone and benzoquinone, which exhibited the typical pattern for a series reaction scheme. The distribution of carboxylic acids was as follows: maleic, fumaric, acetic and oxalic acids. These low-molecular carboxylic acids and aromatic compounds were responsible for the TOC that remained after almost complete removal of phenol. Moreover, one of the most interesting options was to use CWPO as a pre-treatment prior to biological treatment, for simple organic acids that are highly biodegradable. During the reactions, destabilization of the catalyst was observed in terms of leaching of copper from zeolite into the reaction mixture, but the previous investigations of similar catalytic systems showed that the activity of the solid catalyst was not due to the homogeneous contribution of the copper leached from the catalyst, but was more likely due to the activity of the heterogeneous catalyst. Further investigations on the mechanism of catalyst destabilization and methods of stabilization are the subject of the following article in the series. The proposed kinetic model adequately fits the experimental data. The rate of phenol oxidation and hydrogen peroxide decomposition increases with the increase in reaction temperature and decrease in initial concentration of hydrogen peroxide. The rate of phenol oxidation is first order toward the concentration of phenol and first order toward the concentration of H2O2. The rate of H2O2 decomposition is first order toward the concentration of H2O2. Activation energy in phenol oxidation was 86.0 kJ mol−1 for phenol oxidation, and 107.6 kJ mol−1 for hydrogen peroxide decomposition, which is in accordance with previously published results.

The intercalation of pyrazolone-based oxalamide metal complexes into Na-montmorillonite (Na-MMT) for catalytic liquid-phase oxidation of phenol using H 2 O 2 was undertaken by a flexible ligand method using metal ions including Mn(II), Zn(II), and Sn(II). First, the metal ions were exchanged with the sodium ions of Na-MMT, and then these metal ions were complexed with a new pyrazolone-based oxalamide ligand. The intercalated metal complexes were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, elemental analysis, and thermogravimetric analysis. Phenol was successfully oxidized by heterogeneous catalysts based on Mn(II), Zn(II), and Sn(II) pyrazolone-based oxalamide complexes intercalated into Na-MMT. These heterogeneous catalysts catalyze the liquid-phase oxidation of phenol using H 2 O 2 to catechol as the major product and hydroquinone and benzoquinone as the minor products. The Mn(II) and Zn(II) complexes intercalated into Na-MMT showed better activity than the Sn(II) complex intercalated into Na-MMT and the reaction without the catalyst. It has been shown that some metal ion complexes intercalated into Na-MMT are active catalysts for liquid-phase oxidation of phenol with hydrogen peroxide., (© TÜBİTAK.)

A series of TiO2 anatase materials with a thickness to width ratio of 0.22-0.62 in their primary nanocrystals, 1.03-1.27 nanocrystals aggregation ratio and 38-68% exposure of (001) facets were tested in phenol CWPO in a fixed-bed reactor in dark. Inactive oxyfluoride phase that covers the as-synthesized nanocrystals should be removed in order to get the highest catalytic activity. Catalytic activity was proportional to the value of surface area related to the exposed (001) facets at the TiO2 nanocrystals surface excluding any synergistic effects between (001) and (101) facets in catalysis. The linear regression of experimental data for studied reaction revealed that the specific catalytic activity per 1 m2 of (001) facets at the surface of TiO2 nanocrystals is at least four times higher compared with that of (101) facets. This is in agreement with theoretical predictions attributing the catalytic activity to surface titanols as active sites and formation of titanols mainly at the surface of (001) facets due to dissociative adsorption of water.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Abstract: Different ferrosilicate samples have been prepared with varying degrees of crystallinity, porous texture, and speciation of the Fe sites by both hydrothermal and sol-gel procedures: Fe-silicalite-1 with microcrystals (2-10 µm) and nanocrystals (180 nm), Fe-containing composite material consisting of silicalite-1 and amorphous silica, and two samples of mesoporous Fe-containing amorphous silica Fe-SiO2. The resulting solids have been tested for their potential as organic pollutants removal under Fenton-like conditions in heterogeneous catalytic wet peroxide oxidation of phenol and clarithromycin lactobionate. Our results indicate that the three aforementioned parameters show a strong interplay towards the abatement of pollutants in liquid phase. Thus, samples with high crystallinity show an improved performance in the oxidation of organic contaminants over amorphous samples in which the Fe speciation is very well controlled.Graphical Abstract: [ABSTRACT FROM AUTHOR]

A polymer-sensitized g-C 3 N 4 /ZnFe 2 O 4 photocatalyst was prepared by in situ calcinations followed by loading of PANI by physisorptions and in situ oxidative polymerization method. The synthesized nanocomposites were characterized by using XRD, FTIR, UV–vis DRS, XPS, PL, SEM and TEM analysis. A good coordination between CN, ZF and PANI was confirmed from FTIR as well as TEM images. The visible light active PANI-sensitized g-C 3 N 4 /ZnFe 2 O 4 heterostructure was used for the photoreduction of Cr (VI) and the photooxidation of phenol simultaneously. However, the photocatalytic reduction of Cr (VI) occurs more rapidly for the coexistence system of phenol and Cr(VI) in comparison to single species, showing synergetic effect. Furthermore, it was found that PANI exhibits excellent photosensitization effect to enhance light absorption. The enhanced photo catalytic activity of PANI-sensitized g-C 3 N 4 /ZnFe 2 O 4 photocatalyst is in good agreement with the obtained photocurrent results. PANI-sensitized g-C 3 N 4 /ZnFe 2 O 4 photocatalyst gives an anodic photocurrent density of 2.5 mA/cm 2 and cathodic current of −1.6 mA/cm 2 , which is much more than that of the neat counterparts. The first-order kinetic constant of photo catalytic Cr(VI) reduction in presence of phenol was 0.0324 min −1 , being about three times more than that for the reduction of single species chromium. The results obtained from this study illustrate that the prepared PANI-sensitized g-C 3 N 4 /ZnFe 2 O 4 photocatalyst can be very well used as an effective and economically viable catalyst due to the ease of separation, and for simultaneous removal of toxic contaminants like Cr(VI) and phenol from wastewater. This magnetic based semiconductor photocatalyst is of great concern to overcome the problem of separation and secondary pollution. This method can also be highly desirable for environmental remediation due to the use of no additional scavengers in this process. [ABSTRACT FROM AUTHOR]

In this work, a hierarchical dendritic Fe 3 O 4 @Fe 0 composite modified with polar C-groups was obtained by electrodeposition and post-solvothermal methods. SEM, EDS, TEM, XRD, Zeta analysis and ESR were employed to study the structure and composition of catalyst, and the catalytic capability was evaluated by phenol degradation experiments. With the increase of water ratio in thermal solution, the composition of prepared catalyst changes into Fe 3 O 4 /Fe 2 O 3 from Fe/Fe 3 O 4 , and the dendritic structure turns into particle-like structure. The phenol degradation experiments indicate the catalyst prepared in pure-ethanol solution possesses the optimal catalytic capability, which has a Fe@Fe 3 O 4 core-shell structure with some polar C-groups on Fe 3 O 4 outer layer. Under the condition of 0.18 g/L of catalyst dosage, 6 mmol/L H 2 O 2 and pH = 4.0, the composite catalyst prepared in pure ethanol could remove 98% phenol for 5 min, greatly higher than dendritic bare Fe o under the same condition. The enhancement of degradation efficiency by Fenton-like reaction might be ascribed to polar groups that facilitate the adsorption of H 2 O 2 , phenol and hydroxyl radicals and promote the transformation of Fe III to Fe II on the catalyst surface. This work provides a new insight into the design and application of high-efficient Fe 0 -based Fenton-like composite catalysts for wastewater purification. [ABSTRACT FROM AUTHOR]

Effects of 0.1 mM melatonin (MT) on chilling injury (CI), membrane fatty acid content and phenolic metabolism in peach fruit were studied during storage at 1°C for 28 days. MT treatment delayed the development of CI in peach fruit, as was illustrated by MT-treated fruit showing lower CI incidence, CI index and firmness loss than the control. MT treatment prevented membrane lipid peroxidation and contributed to maintaining a higher ratio of unsaturated to saturated fatty acids in peach fruit. MT treatment also stimulated the activities of glucose-6-phosphate dehydrogenase, shikimate dehydrogenase and phenylalanine ammonia lyase, but inhibited the activities of polyphenol oxidase and peroxidase. This would help in activating the accumulation of total phenolic and endogenous salicylic acid that might have a direct function in alleviation of CI. These results indicate that MT treatment can be an effective technique to reduce postharvest CI during low temperature storage of peach fruit. [ABSTRACT FROM AUTHOR]

Iron nanoparticles embedded within ordered mesoporous carbon catalyst (Fe-OMC) was prepared using a facile “one-pot” synthesis method. The as-synthesized catalyst was characterized by using FTIR, XRD, SEM-EDS mapping, HRTEM and XPS. The results revealed that Fe oxide nanoparticles were highly dispersed in the OMC. The prepared Fe-OMC materials as heterogeneous Fenton catalysts were specifically applied in the fixed-bed reactor which operated under continuous-flow condition, showing a promising performance in the oxidative degradation of phenol with high catalytic activity (e.g. phenol conversion nearly 100%) and stability. The effects of feed flow rate and catalyst bed height on the conversions of phenol and H 2 O 2 , the iron leaching concentration as well as pH values of reaction solutions were also systematically investigated to determine the optimal operation conditions. The experimental results showed that the Fe-OMC catalyst achieved the highest activity (>99% phenol and H 2 O 2 conversion) with remarkable low iron leaching concentration (10–20 mg/L) under continuous-flow operations. The stability and reusability evaluations of Fe-OMC catalysts indicated the phenol conversion remains above 90% during a 39 h long-term evaluation. It can be finally concluded that the prepared Fe-OMC catalyst in this work shows promising potential to be an efficient heterogeneous Fenton catalyst for the degradation of hazardous phenolic aqueous solutions. [ABSTRACT FROM AUTHOR]

This work reports on the process of phenol electrooxidation, which is carried-out through continuous electrolysis of synthetic, sodium sulphate-based wastewater. Phenol electrodegradation is examined by means of a laboratory size (ca. 700 cm³ of working volume), poly (methyl methacrylate)-made electrolyser unit for various, carbon fi bre and graphite-based anode configurations, and stainless steel cathodes, two different current-densities and concentrations of phenol in synthetically prepared wastewater solution. Proper monitoring of phenol degradation (including quantitative identification of reaction products and calculation of specific energy consumption) in wastewater is performed by means of instrumental, combined HPLC and MS technique in function of electrolysis time. [ABSTRACT FROM AUTHOR]

Electrochemical transformations and antioxidant activity of some Schiff bases 1–5 containing ferrocenyl group and (thio‐)phenol, catechol fragments were investigated. Compounds under investigation are: 2‐(ferrocenylmethylene)amino)phenol (1), 2‐((ferrocenylmethylene)amino)‐4,6‐di‐tert‐butylphenol (2), 2‐((ferrocenylmethylene)amino)‐thiophenol (3), 3‐((ferrocenylmethylene)hydrazonomethyl)‐4,6‐di‐tert‐butylcatechol (4) and 2‐((3,5‐di‐tert‐butyl‐4‐hydroxybenzylidene)amino)thiophenol (5). In a case of compounds 1–3 it has shown that the sequence of electrochemical transformations leads to the products of intramolecular cyclization – 2‐ferrocenylbenzoxazole (benzothiazole). o‐Quinone formation occurs during the electrochemical oxidation of catechol‐ferrocene 4 at the first anode stage. Electrochemical oxidation of the redox‐active fragments in Schiff bases 1–4 can be achieved indirectly at a lower potential corresponding to the oxidation of ferrocenyl moiety, consequently these substances can reveal more pronounced antioxidant properties. The antioxidant activities of the compounds were evaluated using 2,2′‐diphenyl‐1‐picrylhydrazyl radical (DPPH) assay, the reaction of 2,2′‐azobis(2‐amidinopropane hydrochloride) (AAPH) induced glutathione depletion (GSH), the oxidative damage of the DNA, the process of lipid peroxidation of rat (Wistar) brain homogenates in vitro. The compounds 1–4 in the antioxidant assays show effectiveness comparable with standard antioxidants (vitamin E, Trolox) and in some parameters superior to them. In the reaction of AAPH with the glutathione compounds 2–5 have a more pronounced protective activity than Trolox. Compounds 1–5 inhibit AAPH induced oxidation damage of the DNA. The more effective inhibitors of the lipid peroxidation process in vitro are molecules containing the bulky tert‐butyl groups: 2 and 4 and Schiff base 3. [ABSTRACT FROM AUTHOR]

Structured copper-containing MFI-type (Cu-MFI) zeolite catalysts on paper-like sintered stainless fiber (PSSF) were prepared by a secondary hydrothermal synthesis method and resulting in Cu-MFI coating with good relative crystallinity (80.7%), high BET surface area (237.5 m 2 /g) and uniform pore size distribution (2–3 nm). The influence of synthesis temperature (120–180 °C) and crystalline time (6–48 h) on the relative crystallinity and thickness of the MFI coating were investigated by XRD and SEM showing the adjustable coating thickness of SiCuMFI zeolite (1–7 μm). Both framework and non-framework (as CuO phase) Cu species were identified for the prepared catalysts by XPS and H 2 -TPR. Specifically, the framework Cu species were confirmed by FT-IR, Raman and UV-vis spectroscopic analyses, showing the effectiveness of the current method for promoting the incorporation of Cu in the MFI framework. A new impeller was designed to host the developed structured catalysts, which allowed the facile use of the catalyst for the practical application in a batch reactor for water/wastewater treatment. Catalytic tests (using phenol as the model pollutant) showed the outstanding catalytic activity of the developed catalysts (99% conversion after 40 min) with negligible Cu leaching (lower than 1 mg/L). [ABSTRACT FROM AUTHOR]

Analysis of the kinetics of aqueous phenol oxidation by a sono-Fenton process reveals that the via involving ortho -substituted intermediates prevails: catechol (25.0%), hydroquinone (7.7%) and resorcinol (0.6%). During the oxidation, water rapidly acquires color that reaches its maximum intensity at the maximum concentration of p -benzoquinone. Turbidity formation occurs at a slower rate. Oxidant dosage determines the nature of the intermediates, being trihydroxylated benzenes (pyrogallol, hydroxyhydroquinone) and muconic acid the main precursors causing turbidity. It is found that the concentration of iron species and ultrasonic waves affects the intensity of the turbidity. The pathway of (hydro)peroxo-iron(II) complexes formation is proposed. Operating with 20.0–27.8 mg Fe 2+ /kW rates leads to formation of (hydro)peroxo-iron(II) complexes, which induce high turbidity levels. These species would dissociate into ZZ-muconic acid and ferrous ions. Applying relationships around 13.9 mg Fe 2+ /kW, the formation of (hydro)peroxo-iron(III) complexes would occur, which could react with carboxylic acids (2,5-dioxo-3-hexenedioic acid). That reaction induces turbidity slower. This is due to the organic substrate reacting with two molecules of the (hydro)peroxo complex. Therefore, it is necessary to accelerate the iron regeneration, intensifying the ultrasonic irradiation. Afterwards, this complex would dissociate into maleic acid and ferric ions. [ABSTRACT FROM AUTHOR]

The C/V-SiO samples were synthesized by the hydrothermal treatment of aqueous glucose and V-SiO that was pre-prepared by a sol-gel process. The samples were characterized by XRD, XPS, EPR, FT-IR, SEM, N adsorption-desorption. The results showed that in the hydrothermal process the V-SiO was covered by a rod-like carbonization material, and a small portion of V species was reduced to V. The activity of the C/V-SiO in benzene hydroxylation with O was tested. The leaching of V from the C/V-SiO during the reaction was restrained because the surface of the V-SiO was covered with the carbonization material. The phenol selectivity of 100% and benzene conversion of 10.8% over C/V(3.9)-SiO were obtained, and the catalytic performance did not decreased after being recycled three times. Graphical Abstract: The leaching of V from the C/V-SiO was restrained in the hydroxylation of benzene with O because the surface of V-SiO was covered with the carbonization material. [ABSTRACT FROM AUTHOR]

Three different Co 3 O 4 materials in sphere, cube and truncated cube were prepared by a hydrothermal process and tested in catalytic phenol degradation using oxone®. The properties of the Co 3 O 4 were characterized by several techniques such as X-ray diffraction (XRD), N 2 adsorption, and scanning electron microscopy (SEM). Co 3 O 4 -cube is highly effective in heterogeneous activation of oxone® to produce sulfate radicals for phenol degradation and the activity of catalysts shows an order of Co 3 O 4 -cube > Co 3 O 4 -sphere > Co 3 O 4 -truncated cube. Kinetic study showed that phenol degradation followed a first order reaction. [ABSTRACT FROM AUTHOR]

Surface properties of nanoceria can strongly affect the catalytic performance in oxidation reactions. In this work, a simple but efficient post-treatment, where H2O2 is used as a complexing agent to dissolve Ce3+ from the surface of CeO2 nanorods with the help of ultrasonic treatment, is carried out to tune the surface properties and increase their catalytic performance for catalytic wet air oxidation (CWAO) of phenol. It is found that the dissolution of Ce3+ from the surface of CeO2 nanorods can create more surface defects and result in a much rougher surface. The H2O2--ultrasonic treatment can also increase Ce3+ concentration, create more surface oxygen vacancies, and narrow the band gap of CeO2 nanorods. These properties enable H2O2--ultrasonic-treated CeO2 nanorods (CeO2-H2O2-sf) to possess strong oxidizing ability to effectively oxidize phenol. Additionally, for the sake of comparison, other post-treatments, including calcination, H2O2, and ultrasonic--H2O, are also imposed on CeO2 nanorods. [ABSTRACT FROM AUTHOR]

Novel amorphous Fe 3 O 4 /FePO 4 /ZrO 2 ceramic coatings as solid acid with porous structure were successfully synthesized in the phosphate electrolyte containing K 2 ZrF 6 via plasma electrolytic oxidation (PEO) technique and characterized by scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The surface acidic property was investigated by NH 3 -TPD method. The results showed that the pore size and the intensity of pore interconnection of amorphous Fe 3 O 4 /FePO 4 /ZrO 2 ceramic coating with solid acid property, increased with the increase of the K 2 ZrF 6 dosage from 0.5 g to 2.0 g in the phosphate electrolyte. The Fenton-like performance of PEO coating catalysts was investigated by degradation of phenol under circumneutral pH. It was found that phenol removal efficiency decreased with the adding of K 2 ZrF 6 amount from 0.5 g to 2.0 g except no catalytic activity of coating prepared without K 2 ZrF 6 , and Fenton-like PEO coating catalyst prepared with 0.5 g K 2 ZrF 6 exhibited a superior catalytic activity which could degrade phenol thoroughly within 2 min under circumneutral pH. The strong acid sites played a dominant role in enhancing the Fenton-like catalytic activity. The excellent catalytic activity of PEO coating prepared in the phosphate electrolyte containing K 2 ZrF 6 endowed it potential application in wastewater treatment. [ABSTRACT FROM AUTHOR]

A novel immobilized solid acid coating on Q235 carbon steel was successfully prepared via plasma electrolytic oxidation. Sulfate functionalized Fe 3 O 4 /FeAl 2 O 4 was confirmed by XRD, TEM and XPS analysis and surface acidic property was verified by NH 3 -TPD measurement. Fenton-like degradation performance was evaluated by employing phenol as target pollutant. Fast phenol degradation under the wide range of pH (pH 6–9) was accomplished within only 11 min. Without sulfate functionalization, phenol could hardly be degraded by Fenton-like oxidation which meant that after sulfate functionalization the existence of acidic microenvironment on the catalyst surface not only provided an optimal circumstance for enhanced Fenton-like reaction, but also avoided adjusting pH of the treated wastewater. A reasonable Fenton-like degradation mechanism was proposed. This paper offered a novel design thought for synthesizing excellent Fenton-like coating catalyst under circumneutral pH. [ABSTRACT FROM AUTHOR]

A new strategy for the synthesis of benzothiophenes through formal [3+2] annulation of sulfanylacetaldehyde and cyclohexa-2,4-dien-1-one monoketals has been developed. This approach relies on the ease of aromatization of tetrahydrobenzothiophenone derivatives prepared by the aforementioned protocol. Given the ready accessibility of various substituted cyclohexa-2,4-dien-1-one monoketals, a range of benzothiophene derivatives became available. [ABSTRACT FROM AUTHOR]

This study examined the oxidation of phenol by electrochemical processes using different mixed-metal oxide (MMO) anodes, namely, Ti/Pt, Ti/IrO2-Ta2O5, Ti/Ta2O5-SnO2-IrO2, Ti/RuO2 and Ti/IrO2-RuO2. First, the effectiveness of different anodes by phenol oxidation was evaluated with the help of such parameters as cyclic voltammetry (CV), current efficiencies and degradation rates. The Ti/Pt anode was found to be the most effective of all types of anodes, as almost complete phenol degradation was gained with its use. Then, optimum operational conditions, applied current density and initial pH, were determined using Ti/Pt as the anode. By-products of phenol degradation (benzoquinone, hydroquinone, pyrocatechol, oxalic and maleic acid) arising gradually during the reaction were determined via high-performance liquid chromatography (HPLC) for all selected anodes. There was a considerable difference between the anodes with regard to degradation efficiency and concentrations of formed by-products. The toxicity was evaluated by measuring the natural luminescence of the bacteria, Vibrio fischeri, for all selected anodes. According to the toxicity assessment, a number of toxic by-products were formed from phenol degradation for all selected anodes. However, their toxicity decreased at the end of electrolysis on the Ti/Pt anode. [ABSTRACT FROM AUTHOR]

A novel solar-light-driven (SLD) Fenton catalyst was developed by reducing the ferrous-ion onto graphene oxide (GO) and forming reduced graphene oxide/α-FeOOH composites (RF) via in-situ induced self-assembly process. The RF was supported on several mesoporous supports (i.e., Al-MCM-41, MCM-41 and γ-Al 2 O 3 ). The activity, stability and energy use for phenol oxidation were systematically studied for a wide pH range. Furthermore, the catalytic mechanism at acid and alkaline aqueous conditions was also elucidated. The results showed that Fe(II) was reduced onto GO nanosheets and α-FeOOH crystals were formed during the self-assembly process. Compared with Fenton reaction without SLD irradiation, the visible light irradiation not only dramatically accelerated the rate of Fenton-based reactions, but also extended the operating pH for the Fenton reaction (from 4.0 to 8.0). The phenol oxidation on RF supported catalysts was fitting well with the pseudo-first-order kinetics, and needed low initiating energy, insensitive to the reacting temperature changes (273–318 K). The Al-MCM-41 supported RF was a more highly energy-efficient catalyst with the prominent catalytic activity at wide operating pHs. During the reaction, OH radicals were generated by the SLD irradiation from H 2 O 2 reduction and H 2 O oxidation in the Fe Ⅱ /Fe Ⅲ and Fe Ⅲ /Fe Ⅳ cycling processes. [ABSTRACT FROM AUTHOR]

The hydrothermal oxidation is an efficient and clean way for wastewater treatment; it is also an energy self sufficient process under certain conditions, by the mean of the highly exothermic reaction of oxidation. In this present work, we studied the modeling of hydrothermal oxidation of phenol in polluted water using supercritical conditions. First we apply a simple mathematical model for tubular reactor, resulting from mass, momentum and energy balances, which is often difficult to solve in its general form. According to adequate simplifications, the profiles of temperature and concentration of chemical species are computed along the reactor. Finite differences numerical method was used to solve the obtained system of equations and a MathCAD program was developed for this purpose. The results are close to experimental works from the literature. To study the influence of some operating conditions on the efficiency of the treatment and the amount of heat generated by the reaction and which will be recovered to heat the inlet flows, we exploited the modeling results to perform a full factorial design of experiment (DOE). The results allow fixing the optimal conditions for the studied factors on the efficiency and energy recovery of the process treatment. [ABSTRACT FROM AUTHOR]

Structural and electronic properties of [ cis -[Cr(tmpcH)X 2 ] n+ (n = 2 or 4; X = OH − , Cl − , Br − and H 2 O; tmpcH = 1,4,8,11-tetrakis(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane were analyzed by DFT and TD-DFT methods. The local reactivity active site of the ligand was determined by the condensed-to atom Fukui indexes (CAFI) f(r) . In the study, the axial bond distance with metal ion undergoes a considerable change from shorter to longer as OH < Cl − < Br − < H 2 O, agreeing with the molecular orbital analysis where the dz 2 energy is lowered for OH − compared to H 2 O at the axial position. After analyzing the geometrical data collected from literature for the complexes of Cr(II), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), and Zn (II) with tmpcH, it was found that the bond distance decreases with increasing number of d-electrons in the 3d orbital, suggesting that the over-lapping of oribital (π) from N py with the metal d-orbital is more effective than those from N cyclam with metal d-orbital. Therefore, the change of different oxidation states for [ cis -[Cr(tmpcH)X 2 ] n+ influences significantly the geometrical and electronic parameters. For cis -[Cr(tmpcH)Cl 2 ] 2+ the calculated bands are red shifted except for the lower energy band (595 nm) which agrees qualitatively with the experimental one; in addition, the effect of solvent on the electronic transition was analyzed. Furthermore, we collected the electronic data for several chromium complexes from the literature, and compared with our results by plotting the data against number of chromium compounds. Finally, the phenol oxidation properties of the chromium complexes were studied, and phenol forms an adduct with [Cr(tmpcH)Cl] 3+ to yield [Cr(tmpcH)Cl-OPh] 2+ which could produce the phenol radical, which is enhanced by the presence of -OCH 3 group at para - position in the phenolic ring. [ABSTRACT FROM AUTHOR]

The homogeneous wet oxidation of phenol, catalysed by Cu(II), has been studied in a trickle-bed reactor. The reactor bed consisted of a ceramic foam made of alumina with a cell density of 20 ppi. This bed is especially suited to promote mass transfer between phases with very low pressure drop.The gas phase (oxygen at 0.6 MPa) was circulated continuously, while the liquid phase (40 mol/m3 phenol in water) was circulated in discontinuous mode, i.e. with total recirculation of liquid. The experiments were planned to determine the influence of the main operating conditions, i.e. liquid superficial velocity (0.9–3.3 × 10−3 m/s), Cu(II) concentration (0.41–0.945 mol/m3) and temperature (110–143 °C). Temperature and liquid superficial velocity were found to have the most marked influence in phenol conversion. The use of the foam packing, particularly at high liquid superficial velocities, enhances oxygen mass transfer between phases and increases the efficiency of the process (higher phenol conversion).A mathematical model, based on conservation equations applied to the bulk liquid and liquid film, has been proposed and validated with the experimental results. It has been found that the model is able to predict the experiments within an error of ±10%. [ABSTRACT FROM AUTHOR]

More and more attention has recently been paid to the electrochemical treatment of wastewater for the degradation of refractory organics, such as phenol and its derivatives. The electrodeposition of different types of manganese oxides (MnO x ) over two substrates, namely metallic titanium and titania nanotubes (TiO 2 -NTs), is reported herein. X-Ray Diffraction (XRD) and X-Ray Photoelectron Spectroscopy (XPS) analyses have confirmed the formation of different oxidation states of the manganese, while Field Emission Scanning Electronic Microscopy (FESEM) analysis has helped to point out the evolutions in the morphology of the samples, which depends on the electrodeposition parameters and calcination conditions. Moreover, cross section FESEM images have demonstrated the penetration of manganese oxides inside the NTs for anodically deposited samples. The electrochemical properties of the electrodes have been investigated by means of cyclic voltammetry (CV) and linear sweep voltammetry (LSV), both of which have shown that both calcination and electrodeposition over TiO 2 -NTs lead to more stable electrodes that exhibited a marked increase in the current density. The activity of the proposed nanostructured samples toward phenol degradation has been investigated. The cathodically electrodeposited manganese oxides (α-MnO 2 ) have been found to be the most active phase, with a phenol conversion of 26.8%. The anodically electrodeposited manganese oxides (α-Mn 2 O 3 ), instead, have shown higher stability, with a final working potential of 2.9 V vs. RHE. The TiO 2 -NTs interlayer has contributed, in all cases, to a decrease of about 1–1.5 V in the final (reached) potential, after a reaction time of 5 h. Electrochemical impedance spectroscopy (EIS) and accelerated life time tests have confirmed the beneficial effect of TiO 2 -NTs, which contributes by improving both the charge transfer properties (kinetics of reaction) and the adhesion of MnO x films. [ABSTRACT FROM AUTHOR]

This work reports on the importance of adsorption and passivation phenomena during the electro-oxidation of phenolic mixture. A case study of the anodic oxidation of phenol and 2-chlorophenol was performed. A carbon black-diamond electrode with 20% carbon black (20CBD electrode) was used as the anode. The anodic oxidation behaviors of 100 mg/L phenol and 100 mg/L 2-chlorophenol on the 20CBD electrode were investigated using cyclic voltammetry in aqueous solutions of 0.25 M Na2SO4. The electrochemical impedance technique was used to investigate the effects of electrode passivation and the adsorption of phenol and 2-chlorophenol through the electrochemical degradation process. The results showed that oxidation of 2-chlorophenol was easier than that of phenol. Even in a 1:1 mixture of 2-chlorophenol and phenol, each at 100 mg/L, the removal rate of 2-chlorophenol was higher than that of phenol. After 6 h, up to 94% of the 2-chlorophenol had degraded, whereas only 20% of the phenol had degraded in the same time. The mass-transfer resistance of phenol was up to 10 times higher than that of 2-chlorophenol. Moreover, the passivation resistance generated on the electrode surface by phenol oxidation was also higher than that generated by 2-chlorophenol oxidation. [ABSTRACT FROM AUTHOR]

Shock-induced cavitation phenomena, resulting from the propagation of the trail of shock-waves generated upon the impact of a solid piston on a liquid surface, was used as an innovative way of intensifying the oxidation of phenol in aqueous media. The amount of energy communicated by the impact was found to be proportional to the impact height, and was directly related to the maximal pressure attained, i.e. in the order of several tens of bars. This peak was followed by a rarefaction period that results in the origination of several cavitation phenomena, which continued upon piston rebound and further shock-wave generation and propagation. The multi-frequency nature of shock-induced cavitation, capable of exciting a wide range of frequencies between 1 kHz and 100 kHz, was confirmed by means of wavelet analysis. Under shock-induced cavitation conditions, phenol degradation was found to be possible even in the absence of any oxidizing agent. High extents of mineralization, i.e. 45.3 and 56.2% TOC elimination, 50 mg/L solution, neutral pH, were obtained in the presence of H 2 O 2 (aprox. 10% vol.), pointing to an acceleration of the oxidation reaction based in a faster and more efficient creation of radical species. [ABSTRACT FROM AUTHOR]

The catalytic wet peroxide oxidation of phenol was investigated over ZnFe2O4 nano spinels under different conditions designed by the experimental design. ZnFe2O4 nano oxide was synthesized by the sol-gel combustion method and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscope techniques. The mean particle size was determined to be around 80-90 nm. The experiments were designed by the Box-Behnken type of response surface methodology by considering four process variables: CH2O2 (mol L−1), ZnFe2O4 amount (g), temperature (°C), and reaction time (min). The optimum condition for the degradation of the phenol was predicted by the response surface methodology. The optimal conditions for phenol degradation were at 0.144 M, 0.156 g, 70 °C, and 300 min of peroxide concentration, catalyst amount, temperature, and reaction time, respectively. The predicted response under these conditions was 99%, whereas the experimental test of predicted condition led to 97% degradation of phenol. Pareto analysis predicted that the order of relative importance of model terms is as follows: reaction temperature (29%) > catalyst amount - reaction temperature (19%) > reaction temperature - reaction time (14%) > reaction time (10.9%) > catalyst amount (9.8%). The study revealed that zinc ferrite nano spinels could be promising for removal of pollutants by the catalytic wet peroxide oxidation process. [ABSTRACT FROM AUTHOR]

Hierarchical zeolites were prepared by post synthesis treatments of commercial ZSM-5 zeolite (Si/Al = 13) involving alkali treatment, acid treatment, steam treatment, combination of acid-alkali treatments, and combination of steam-acid-alkali treatments. Various characterization techniques were employed to investigate the influence of each post synthesis treatment step on the structure, composition, porosity, acidity and iron species of the samples. The catalytic activity and selectivity of the post modified samples were also measured in the direct oxidation of benzene to phenol using nitrous oxide as an oxidising agent. The combination of steam-acid-alkali treatments of ZSM-5 zeolite exhibiting low Si/Al ratio lead to significant high level of mesoporosity with considerable preserved amount of microporosity that was not possible to achieve by the other treatment methods outlined above. ESR results reveal the homogeneous distribution of iron species when commercial MFI zeolite containing low amount of iron was steam treated. The modified iron species were not significantly altered by subsequent acid and alkali treatments, while the alkali treatment heals the destructed part of the zeolite that was produced by steam and acid treatments. These modifications in the pore structure and iron species led to excellent catalytic performance in the direct oxidation of benzene to phenol using nitrous oxide. [ABSTRACT FROM AUTHOR]