Showing papers on "Wet oxidation published in 2017"
TL;DR: Information is collected on the production of valuable chemicals by thermal hydrolysis and wet oxidation and on their main features, which seem to be more suitable for yielding higher amounts of acid than diluted, undigested and primary ones.
100 citations
TL;DR: Preliminary differential cost analysis showed that wet oxidation combined with precipitation at an optimal pH and magnesium ion dose could generate revenue and was more sensitive to pH than magnesium ion concentration.
94 citations
TL;DR: In this paper, the literature published in the treatment of refractory organic pollutants in industrial wastewaters, such as dyes, were taken as model pollutants in most cases.
88 citations
TL;DR: In this article, N-containing graphenes obtained either by simultaneous amination and reduction of graphene oxide or by pyrolysis of chitosan under an inert atmosphere have been found to act as catalysts for the selective wet oxidation of glucose to succinic acid.
51 citations
TL;DR: In this paper, the MoO 3 catalysts as a wet air oxidation catalyst have been synthesized by a simple hydrothermal method, and a detailed orthogonal design on the preparation conditions was performed, aiming to optimize the parameters to produce MoO3 with the most prominent catalytic performance.
40 citations
TL;DR: In this article, BEA type zeolites, with high content of Lewis and Bronsted sites, promoted the catalytic D4 ring-opening leading on the formation of smaller α-ω-silanediols, which are narrower molecules able to diffuse into the channel system.
37 citations
TL;DR: In this paper, an easy to handle, solvent-free post-doping method, combining a mechanical treatment under ball-milling followed by thermal treatments under inert atmosphere or ammonia was developed.
Abstract: In this work, a comprehensive study was performed regarding the incorporation of N-groups into the multi-walled carbon nanotube sp2 network, namely, quaternary nitrogen, pyrrolic and pyridinic groups. An easy to handle, solvent-free post-doping method, combining a mechanical treatment under ball-milling followed by thermal treatments under inert atmosphere or ammonia was developed. Different nitrogen precursors (melamine, urea, NH 3 ), different precursor/CNT ratios, presence of O-containing surface groups and final temperatures of the thermal treatment were evaluated towards the generation of active and stable N-species. The materials were characterized in terms of texture and surface chemistry by several techniques: N 2 adsorption, XPS, TPD, TGA and elemental analysis. The catalytic performance of the novel N-doped CNTs was evaluated in the oxidation of oxalic acid and phenol (used as model pollutants) by catalytic wet air oxidation (CWAO). Catalytic oxidation of model pollutants is faster in the presence of samples rich in nitrogen, and also favoured in the absence of O-containing surface groups on the CNT surface.
35 citations
TL;DR: This letter demonstrates a simple method to achieve high-yields of 1H semiconducting MoS2 monolayers in concentrated, colloidally-stable aqueous suspension based on oxidation suppression during the hydrothermal processing step used for metal-to-semiconductor phase reversion.
Abstract: This letter demonstrates a simple method to achieve high-yields of 1H semiconducting MoS2 monolayers in concentrated, colloidally-stable aqueous suspension. The method is based on oxidation suppression during the hydrothermal processing step used for metal-to-semiconductor phase reversion. Accompanying DFT calculations on elementary steps in the MoS2 wet oxidation reaction suggest that a two-site corrosion mechanism is responsible for the observed high reactivity and low stability of 1T metallic MoS2.
35 citations
TL;DR: In this paper, the effect of oxygen vacancies on the catalytic wet air oxidation (CWAO) of phenol was investigated with CeO2 and MnOx-CeO2 as catalysts.
Abstract: Catalytic oxidation can be effectively promoted by the presence of oxygen vacancies on the catalyst surface In this study, the effect of oxygen vacancies on the catalytic wet air oxidation (CWAO) of phenol was investigated with CeO2 and MnOx–CeO2 as catalysts CeO2 and MnOx–CeO2 catalysts with different amounts of oxygen vacancies were obtained via hydrothermal methods and applied for the CWAO of phenol It was found that CeO2 and MnOx–CeO2 nanorods were much more active than the cubic nanorods The physicochemical properties of the samples were characterized by TEM, XRD, BET, XPS, and H2-TPR techniques The results revealed that the presence of oxygen vacancies in CeO2 and MnOx–CeO2 catalysts could increase the oxidizing ability of the catalysts surface The addition of Mn could greatly improve the adsorption ability of CeO2 and more efficiently oxidize phenol and its intermediates The synergy between Mn and Ce could further improve the catalyst redox properties and produce a larger amount of active oxygen species, which is the reason why MnOx–CeO2 nanorods are the most active catalysts among the catalysts investigated in this study
33 citations
TL;DR: In this article, X-ray diffraction patterns reveal that the tetragonal ZrO2 phase is stabilized by the presence of CeO2, forming a solid solution, and preventing transformation to the monoclinic phase.
Abstract: In this work Ag nanoparticles supported on ZrO2–CeO2 promoted with different amounts of CeO2 (0, 0.5, 1, 5, 10, 15 and 20 wt%) were synthesized by deposition–precipitation method in order to test the Catalytic Wet Air Oxidation (CWAO) of Methyl Tert-Butyl Ether (MTBE). X-ray diffraction patterns reveal that the tetragonal ZrO2 phase (t-ZrO2) present in the catalysts is stabilized by the presence of CeO2, forming a solid solution, and preventing transformation to the monoclinic phase (m-ZrO2). The t-ZrO2 stability and the dispersion of Ag on ZrO2 increase with CeO2 concentration. HRTEM images confirmed that the mean crystallite size of supports and monometallic Ag catalyst decreases by CeO2 addition. CeO2 can also improve the reduction of Ag2O and increase also the d-electron density of the surface silver atoms. Furthermore, CeO2 has a promoting effect on silver supported zirconia–ceria because of the strong metal–support interaction and its relationship of oxygen vacancies of zirconia–ceria support. The extent of reduction of silver controls the quantity of oxygen to be adsorbed during the catalytic oxidation reaction. In general, a small crystal size and high metallic dispersion can enhance the activity of MTBE catalytic wet air oxidation. The Ag/ZrO2–(15%)CeO2 catalyst was the most active with 90% MTBE conversion.
32 citations
TL;DR: Of the two catalysts used, phosphomolybdic acid gave the most promising results, with carboxylic acid yields and lignin conversions of up to 45% and 95%, respectively.
Abstract: The production of carboxylic acids by partial wet oxidation of alkali lignin at elevated temperatures and pressures was studied experimentally Two different heteropoly acids, phosphotungstic acid (H₃PW12O40) and phosphomolybdic acid (H₃PMo12O40), were used to catalyze the oxidation of lignin under hydrothermal conditions Factors influencing the total yield of carboxylic acids formed during the partial oxidation of lignin were investigated Formic, acetic and succinic acids were the major products identified Of the two catalysts used, phosphomolybdic acid gave the most promising results, with carboxylic acid yields and lignin conversions of up to 45% and 95%, respectively
TL;DR: In this article, a very high amount of Mn4+ was used for the wet air oxidation (CWAO) of phenol at a very low temperature of 70 °C.
TL;DR: The temperature was found to be the most significant factor for metals immobilisation, followed by reaction time, while pH had negligible effect, and optimal conditions of SCWO on metals were found at 240°C, 60min, pH 5.
TL;DR: In this article, a hybrid organic-inorganic solar cell following an inverted bulk heterojunction configuration was fabricated based on the lotus-like ZnO structures, which achieved a power conversion efficiency of up to 1.18% which demonstrates the applicability of the technique for photovoltaic applications.
Abstract: Zinc oxide (ZnO) nanostructures with various morphologies (pencil-like nanorods, nanotubes, and lotus-like structures) have been successfully formed by simple oxidation of vacuum deposited Zn thin film on glass/ITO substrates in hot water at 90 °C. The morphology evolved from pencil-like nanorods to nanotubes to lotus-like structures with prolonged oxidation of Zn thin film for 6–24 h. The change in morphology of ZnO is attributed to the combined effects of electrochemical reactions in the solution, morphology and structure of Zn thin film, and wurtzite structure of resulting ZnO. A hybrid organic–inorganic solar cell following an inverted bulk heterojunction configuration was fabricated based on the lotus-like ZnO structures. The solar cell achieved a power conversion efficiency of up to 1.18%, which demonstrates the applicability of the technique for photovoltaic applications.
TL;DR: In this paper, different advanced oxidation processes (AOPs) are compared for their feasibility for mineralization of alkyd resin wastewater, including Fenton process, combined ozonation (O 3 ) and hydrogen peroxide (H 2 O 2 ), electro-oxidation (EO), wet air oxidation and cavitation using ultrasonic horn (US).
Abstract: In the present study, different advanced oxidation processes (AOPs) are compared for their feasibility for mineralization of alkyd resin wastewater. The AOPs studied include: Fenton process, combined ozonation (O 3 ) and hydrogen peroxide (H 2 O 2 ), electro-oxidation (EO), wet air oxidation and cavitation using ultrasonic horn (US). The studied AOPs in the order of increasing electrical energy consumption per unit mass of TOC removal (E EM ) are: Fenton process (18 kWh/kg), EO (83.58 kWh/kg), combined EO and O 3 (187 kWh/kg), wet air oxidation (429 kWh/kg), combined O 3 and H 2 O 2 at pH 8 (477 kWh/kg), combined US, O 3 and H 2 O 2 at pH 8 (776 kWh/kg) and US alone at pH 8 (990 kWh/kg). Among the studied AOPs and their combinations, the combined O 3 and H 2 O 2 is most promising as it doesn’t suffer from complex formation issues as in the Fenton process, EO and combined EO and O 3 , requires lower fixed cost as compared to wet air oxidation and requires less E EM as compared to combined US, O 3 and H 2 O 2 and US alone.
TL;DR: The absorbent of [C4mim]3PMo12O40-ionic liquid system provides a new approach for wet oxidation desulfurization at high temperature.
TL;DR: In this article, 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.
Abstract: 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.
TL;DR: In this article, the treatment of non-biodegradable industrial organic raffinate containing refractory and toxic organic compounds pyridine, β-picoline and 3-cyanopyridine has been studied by coupling of catalytic wet air oxidation (CWAO) over alumina based platinum catalyst and biological processes.
TL;DR: In this article, the authors evaluated a plausible pretreatment for rice straw based on the 23-factorial experimental design with a goal to reduce biomass recalcitrance by enhancing the cellulose recovery, hemicellulose solubilization, lignin removal and concomitantly generating limited degradation products.
Abstract: Biomass recalcitrance is considered to be one of the impediments in bioconversion of lignocellulosic biomass (LCB) to sugars. Rice straw, a potential lignocellulosic waste, owing to the surplus availability, renewability and high carbohydrate content was used as a model LCB in the present study. The alkaline hydrogen peroxide-assisted wet air oxidation (APWAO) was evaluated as plausible pretreatment for rice straw based on the 23—factorial experimental design with a goal to reduce biomass recalcitrance by enhancing the cellulose recovery, hemicellulose solubilization, lignin removal and concomitantly generating limited degradation products. APWAO resulted in an overall cellulose recovery ranging from 80.54 to 93.02%, hemicellulose solubilization of 36.44–82.08% and lignin removal of 65.95–81.11% (all on w/w basis) respectively and absence of potent inhibitors viz. furfural and 5-hydroxymethylfurfural. The statistically significant pretreatment factors that affected each of these responses were assessed and optimum pretreatment conditions were determined to be biomass soaking in 0.5% H2O2 for 14 h succeeded by wet air oxidation (WAO) at 190 °C, 6 bar, 20 min by multi-objective numerical optimization. Further, the morphological and structural changes occurring as a result of pretreatment were scrutinized using SEM and FT-IR. APWAO further ensued in enhanced cellulose accessibility during enzymatic saccharification indicated by the glucose yield ranging from 113.97 to 200.34 g/kg untreated rice straw. Thus, the combined pretreatment (APWAO) i.e. pre-soaking in alkaline H2O2 followed by WAO was shown to enhance glucose yields owing to significant delignification.
TL;DR: In this article, the catalytic wet oxidation of paracetamol (PAR) was tested with Pt, Ru, Ir containing Ti monoliths measuring COD, TOC and TN conversion and compared with that of the non-catalytic reaction.
TL;DR: In this paper, a series of characterization techniques are conducted to determine the relationship between physico-chemical properties and the catalytic performance of Ru/Ti 0.9 Zr 0.1 O 2 catalyst.
TL;DR: In this article, small ruthenium oxyhydroxide nanoparticles supported on N-doped graphene were used for the conversion of glucose into succinic acid under wet oxidation conditions (160 oC, 18 atm O2 pressure).
Abstract: Impregnation of RuCl3 on N-doped graphenes results in the formation of well-dispersed, small ruthenium oxyhydroxide nanoparticles supported on N-doped graphene that may exhibit high selectivity (87 %) for the conversion of glucose into succinic acid under wet oxidation conditions (160 oC, 18 atm O2 pressure). Ruthenium loading and N atom distribution on graphene influence the catalytic activity, the best performing catalyst having 1 wt% Ru loading on a graphene having a large population of graphenic N atoms. The high catalytic selectivity to succinic acid has been correlated with the presence of small ruthenium nanoparticles. The present catalyst improves the best one previously reported, since it does not require the continuous addition of an excess of amine to reach high succinic acid selectivity and reusability.
TL;DR: In this article, a detailed model for the homogeneous wet air oxidation was presented, and it was concluded that dissolved copper undoubtedly contributes, even in low concentration, to the overall phenol conversion.
Abstract: Wastewaters containing phenol and related compounds are refractory to biological treatments. Wet air oxidation has been proposed as an alternative. The replacement of the usual homogeneous catalysts by heterogeneous ones would be of great economic and operational benefits. The reaction has been studied in a batch reactor, at different operating conditions (temperature, phenol concentration, and pH), using CuO/γ–Al 2 O 3 as catalyst). The catalyst stability decreases due to copper leaching, solid polymer deposition on the catalyst surface and changes of the catalyst structure. Copper leaching is produced when pH decreases as a consequence of the short chain acids (oxalic and maleic acid) generated during the reaction. The deposition of solid polymer is caused by the reaction of phenol oxidation intermediates. Copper leaching is considerably reduced when pH is controlled during the reaction: at pH 7 and 10, leaching takes place at very low extent (less than 2% catalyst loss). Based on a detailed model for the homogeneous wet air oxidation, it can be concluded that dissolved copper undoubtedly contributes, even in low concentration, to the overall phenol conversion. The homogeneous reaction was found to be considerably faster than the heterogeneous one.
TL;DR: In this paper, a hierarchical zinc oxide (ZnO) nanostructures were successfully grown by oxidation of etched Zn foil in water at 90°C and the morphology evolved from nanorods to hexagonal nanotubes then to flower-like structures with continued oxidation.
Abstract: Hierarchical zinc oxide (ZnO) nanostructures were successfully grown by oxidation of etched Zn foil in water at 90 °C The morphology of the ZnO nanostructures evolved from nanorods to hexagonal nanotubes then to flower-like structures with continued oxidation Etching of the foil possibly promotes the growth of these ZnO nanostructures by creating inhomogeneities on the surface of the foil, which act as nucleation sites In situ mixed potential measurement in combination with thermodynamic calculation was performed to elucidate the effect of temperature on the formation of the ZnO hierarchical nanostructures The mixed potential increased with higher oxidation temperatures, suggesting enhanced oxidation
TL;DR: In this paper, a model that describes the evolution of soluble biopolymers during the wet oxidation of activated sludge was proposed and successfully fitted to the experimental data, achieving values of 23.1%, 14.7%, 8.3%, 0.9% and 0.5% for proteins, humic acids, carbohydrates, uronic acids and DNA, respectively, with regard to the initial volatile suspended solids con...
Abstract: In this paper, wet oxidation was applied to an activated sludge as a potential technique for the recovery of products of industrial value. With this end, the effect of the treatment on the polymeric composition of the sludge was analyzed. To establish differences due to the origin of the biopolymers (extracellular or intracellular), the sludge was separated into fractions: soluble microbial products (SMP), loosely bound extracellular polymeric substances (LB-EPS), tightly bound extracellular polymeric substances (TB-EPS) and naked cells and each was treated at 190 °C and 65 atm. A model that describes the evolution of soluble biopolymers during the wet oxidation of sludge was proposed and successfully fitted to the experimental data. Results showed a rapid solubilization of polymers during the first minutes of reaction, achieving values of 23.1%, 14.7%, 8.3%, 0.9% and 0.5% for proteins, humic acids, carbohydrates, uronic acids and DNA, respectively, with regard to the initial volatile suspended solids con...
TL;DR: In this paper, the authors reported the catalytic wet air oxidation of paper industry wastewater using CuO CeO 2 nanocatalysts, which were prepared by co-precipitation method without using any surfactant.
Abstract: Today, the removal of persistent organic pollutants from industrial wastewater stands a major challenge. Here we report the catalytic wet air oxidation of paper industry wastewater using CuO CeO 2 nanocatalysts. The catalysts were prepared by co-precipitation method without using any surfactant. The catalysts were characterized by XRD, FTIR, XPS, Raman, N 2 -sorption, FE-SEM, TEM and EDX techniques. Characterization results revealed the formation of porous CuO CeO 2 nanocatalysts with high surface area, pore volume and oxygen vacancies. Interaction between copper and cerium greatly enhanced the catalyst activity, and the maximum removal of COD (67%), color (81%), AOX (61%), TOC (64%) and chlorophenolics (66%) was achieved with Ce 40 Cu 60 nanocatalyst. The degradation of non-biodegradable compounds resulted in increased biodegradability index.
TL;DR: In this paper, a facile MgO-based wet oxidation process for biomass pretreatment was developed, which could provide an indispensably weak but adequate alkaline environment to support the oxygen delignification reaction.
Abstract: We have developed a facile MgO-based wet oxidation process for biomass pretreatment. Herein, we performed kilo-scale experiments to elucidate the transformations of Mg in the process as well as the recycling of the MgO-based solid alkali. A new intermediate, magnesium oxide carbonate [Mg3O(CO3)2] generated in situ during the process was shown for the first time, which could provide an indispensably weak but adequate alkaline environment to support the oxygen delignification reaction. However, once the solid alkali was transformed into hydromagnesite [Mg5(CO3)4(OH)2] with sufficient CO2, the hydromagnesite form would prevent the solid alkali from developing resistance to the acidic gaseous CO2. Ultimately, if we take the features of the solid alkali into consideration, alkali recovery for this process was fulfilled easily without concentration or causticization, which are of high cost but unavoidable in the traditional recycling of sodium alkali.
TL;DR: In this article, the efficiency of catalytic wet oxidation (CWO) for the destruction of three phenolic compounds (phenol, o-cresol and 2,5-dimethylphenol) individually as well as in mixture was investigated.
Abstract: The present study investigated the efficiency of catalytic wet oxidation (CWO) for the destruction of three phenolic compounds (phenol, o -cresol and 2,5-dimethylphenol) individually as well as in mixture (phenolics concentration = 10 g/L, NaOH concentration = 10 g/L, chemical oxygen demand (COD) = 24000 mg/L, total organic carbon (TOC) = ∼7800 mg/L and pH ∼13). The oxidative hydrothermal reaction was carried out in a laboratory scale high pressure batch reactor (capacity = 0.7 L) at moderate temperature (120–160 ° C) and pressure (oxygen partial pressure = 0.8 MPa) conditions in the presence of a heterogeneous catalyst (i.e., 5% Cu/activated carbon). After 4 h CWO reaction on the mixture of phenolics at a reaction temperature of 160 °C and initial reaction pH of 9.0, TOC and COD were reduced by ∼90% and 82%, respectively. The phenolics removal was mainly due to the oxidation reaction and the contribution of other reactions such as adsorption and/or hydrolysis was lower. The copper leaching in the solution was found to be 15–26 ppm. The characterization of recovered catalyst showed increase in carbon content thus confirming the deposition of carbonaceous deposit.
TL;DR: In this article, a novel structure of Mo-Cu-Fe-O composite was successfully prepared by co-precipitation and impregnation method, and the properties of the as-prepared samples were determined using X-ray diffraction, temperatureprogrammed reduction by H2, cyclic voltammetry, and temperature-programmed desorption by O2.
TL;DR: It is concluded that the oxidation of Hg0 mainly depends on the electronic supply efficiency from the solution, and the Fenton reagent, composed of H2O2 and metal cations, is superior to O3 and the solution of KMnO4 and NaClO2.
Abstract: The vast majority of Hg2+ can be removed while elemental mercury (Hg0) can hardly be removed due to its characteristic of high volatility and insolubility in water. Till now, how to oxidize Hg0 to Hg2+ is the key for the purification of Hg0, especially when there are others pollutants, such as HCl, SO2, and NOx. In this review, the method and mechanism of Hg0 purification from flue gas by H2O2, KMnO4, NaClO2, and O3 are reviewed comprehensively. It is concluded that the oxidation of Hg0 mainly depends on the electronic supply efficiency from the solution. The Fenton reagent, composed of H2O2 and metal cations, is superior to O3 and the solution of KMnO4 and NaClO2. Moreover, HCl, SO2, and NOx in the flue gas can influence the oxidation and purification mechanism of Hg0. It is found that HCl in flue gas had obvious auxo-action on the oxidation of mercury, and SO2 and NOx have different effects on the oxidation of Hg0 with the change of compositions and concentration of pollutants in the flue gas. In general, SO2 and NOx can slightly promote the oxidation of Hg0 due to the synergistic effect.