Catalytic wet peroxide oxidation of phenolic solutions over a LaTi1−xCuxO3 perovskite catalyst

LaTi_1−xCu_xO₃ perovskites are efficient catalysts for the oxidation of aqueous solutions of phenol using hydrogen peroxide as precursor of free radicals. The catalytic results have shown that under mild reaction conditions and oxidant contents lower than stoichiometric, phenol was rapidly removed with a final total organic carbon (TOC) conversion of ca. 90%. Initial rate of TOC removal depends dramatically on temperature, catalyst loading and peroxide concentration. Perovskite catalyst after reaction is completely regenerated by calcination and retains a similar catalytic performance. Finally, the catalytic results demonstrate that leaching of active species during the catalytic oxidation seems to proceed by a complex mechanism in which the presence of hydrogen peroxide in combination with phenol plays an essential role.     

Mineralization of phenol by a heterogeneous ultrasound/Fe-SBA-15/H2O2 process: Multivariate study by factorial design of experiments

A novel heterogeneous catalyst has been used for the oxidation of aqueous solutions of phenol by catalytic wet peroxide oxidation assisted by ultrasound irradiation. This composite catalyst material that contains crystalline hematite particles embedded into a mesostructured SBA-15 matrix was used successfully in the oxidation of phenol by heterogeneous Fenton and photo-Fenton processes. Ultrasound is found to enhance the activity of the catalyst in the process, without prejudice to the stability of the iron supported species. The influence of different variables, such as hydrogen peroxide concentration or catalyst loadings in the reaction was studied by factorial design of experiments. Catalyst loadings of 0.6 g L⁻¹ and a concentration of hydrogen peroxide close to twice the stoichiometric amount yield a remarkable organic mineralization, accompanied by excellent catalyst stability. The coupled US/Fe-SBA-15/H₂O₂ process at room temperature is revealed as a promising technique for wastewater treatment.     

Preparation of nitrogen-containing humic preparations from peat

The effects of the duration of cavitation treatment, the concentration of NH₃, the amount of hydrogen peroxide, and the water duty on the nitrogen content the dry residue and the amount of organic substances in the liquid phase of the oxidation products of peat with hydrogen peroxide in an aqueous ammonia solution using a cavitation technology were studied. The elemental and functional-type compositions of isolated nitrogen-containing humic preparations were studied.     

Characterization and Activity of Cu/ZSM5 Catalysts for the Oxidation of Phenol with Hydrogen Peroxide

The heterogeneous catalytic wet peroxide oxidation (CWPO), involving total oxidation of organic compounds to CO₂ and H₂O is a possible path for the treatment of toxic and bio‐refractory wastewater streams. The aim of this work was to synthesize and characterize three Cu/ZSM5 catalysts prepared by direct hydrothermal synthesis. The mass ratio of the active metal component in the zeolite ranged from 1.62–3.24 wt %. These materials were tested for CWPO of aqueous phenol in a stainless steel Parr reactor, in batch operation under mild conditions (at atmospheric pressure and a temperature of 353 K). The catalyst weight was 0.1 g dm^–3 and the initial concentration of phenol and hydrogen peroxide were 0.01 mol dm^–3 and 0.1 mol dm^–3, respectively. The catalysts were characterized by powder X‐ray diffraction (XRD), scanning electron microscopy (SEM), AAS and ICP‐MS. Their catalytic performance was monitored in terms of phenol and total organic carbon (TOC) conversion, hydrogen peroxide decomposition, by‐product distribution and the degree of copper leached into the aqueous solution. The experimental results indicated that within 180 min, these catalysts facilitated almost complete elimination of phenol and a significant removal of chemical oxygen demand, without significant leaching of Cu ions from the zeolite. The Cu/ZSM5‐DHS3 catalyst with the highest copper loading was proven to be the best candidate. The useful fraction of hydrogen peroxide that contributed to the removal of the organic compounds quantified in terms of selectivity, S, indicated that the CWPO selectivity was always less than 100 %, which meant that there was some self‐degradation of oxidant. It was also shown that oxidation of phenol took place on the catalyst surface via a heterogeneous mechanism, and that the contribution of any homogeneous reaction mechanism was not significant.     

Advanced Oxidation of Tannic Acid in Aqueous Solution

Decomposition of tannic acid in aqueous solution in advanced oxidation processes has been studied. Different oxidizing agents: ozone, hydrogen peroxide and UV radiation have been used both as single and mutually combined components of the system. The course of reaction was examined by the changes of chemical oxygen demand (COD) and total organic carbon (TOC) in aqueous solutions. Particular attention has been paid to determine optimal concentration of hydrogen peroxide, when it is used alone, together with O₃ and in H₂O₂+O₃+UV combination. The most effective optimal concentration of H₂O₂ was found. The entire mineralization of tannic acid into final products CO₂ and H₂O can be accomplished in all combinations of advanced oxidation with ozone. Bacteriological test ToxAlert® with luminescence bacteria Vibro fisheri proved that toxicity of solutions decreased considerably during advanced oxidation of tannic acid solution.     

Reverse osmosis for the separation of organics from aqueous solutions

The properties of modern polymer membranes with respect to organic aqueous solutions are discussed to some extent. The potential of reverse osmosis for the treatment of organics-contaminated waste water is demonstrated by a discussion of two examples—landfill-drainage water and ‘desorbate’. It is shown that in the case of partial immiscibility, a combination of reverse osmosis and phase separation allows operation at very high recovery rates without exceeding tolerable concentrations of organics within the reverse osmosis modules. Furthermore, it is shown that a purification of the organic phase by pervaporation is economically feasible.     

Application of O3 and O3/H2O2 as post-treatment processes for color removal in swine wastewater from a membrane filtration system

This study was aimed to evaluate the use of ozone (O₃) alone and peroxone (a combination of ozone and hydrogen peroxide; O₃/H₂O₂) as post-treatment processes for color removal in swine wastewater from a membrane filtration system. Results showed that the application of ozone-alone process or the peroxone process could reduce both capital and operating costs compared to reverse osmosis (RO) treatment. Of the two oxidation processes, the ozone-alone process was the most effective for treating nanofiltration (NF)-filtered wastewater, while the peroxone process was the most effective for treating ultrafiltration (UF)-filtered wastewater.     

Removal of phenol from coupling of talc and peroxidase. Application for depollution of waste water containing phenolic compounds

The degradation of phenol by a combination of horseradish peroxidase/hydrogen peroxide in the presence of talc, a natural abundant and low cost mineral, was investigated. Adsorption of the reaction products on the talc effectively protected the biocatalyst against contamination by oxidative products, thereby prolonging its catalytic action and leading to almost complete elimination of phenols in aqueous media. Suitable conditions for depollution of waste water containing phenolic substances were developed after optimization of various parameters (type and amount of talc, reaction duration).     

Catalytic oxidation of Fe(II) by activated carbon in the presence of oxygen.: Effect of the surface oxidation degree on the catalytic activity

The catalytic oxidation of Fe(II) species in aqueous solution by activated carbons with different degrees of surface oxidation is described. The parent activated carbon was oxidized with aqueous solutions of nitric acid or hydrogen peroxide, and submitted to thermal treatment at 373, 523 and 773 K. The activated carbons prepared were characterized by N₂ adsorption and temperature-programmed desorption, and their catalytic behavior was determined by measuring the oxidation rate of Fe(II) to Fe(III) and the generation of hydrogen peroxide. Catalytic activity is a function of the nature of oxygen surface groups generated by oxidation.     

Catalytic oxidation of Fe(II) by activated carbon in the presence of oxygen.: Effect of the surface oxidation degree on the catalytic activity

The catalytic oxidation of Fe(II) species in aqueous solution by activated carbons with different degrees of surface oxidation is described. The parent activated carbon was oxidized with aqueous solutions of nitric acid or hydrogen peroxide, and submitted to thermal treatment at 373, 523 and 773 K. The activated carbons prepared were characterized by N₂ adsorption and temperature-programmed desorption, and their catalytic behavior was determined by measuring the oxidation rate of Fe(II) to Fe(III) and the generation of hydrogen peroxide. Catalytic activity is a function of the nature of oxygen surface groups generated by oxidation.     

Oxidation and halogenation of jojoba wax

The oxidation with hydrogen peroxide and permanganate and the allylic bromination, chlorination and chloro-etherification of the olefinic bonds of the liquid wax extracted from beans of jojoba (Simmondsia chinensis) were studied. Hydrolytic splitting of the wax into its carboxylic and alcoholic components competed with most reactions carried out in aqueous systems. The use of a suitable phase-transfer catalyst enabled the oxidation of the double bonds to carboxyls using permanganate in aqueous systems. Reaction of the wax with hydrogen peroxide in formic acid yielded formates, which were then hydrolyzed to vicinal glycols. The diglycols obtained by hydrogen peroxide oxidation were benzoylated. Allylic chlorination of jojoba wax with t-butyl hypochlorite in organic solvents was carried out. Conditions were found for the allylic bromination of the wax, yielding mono-, di-, tetra-, or octabromo derivatives.     

Water delignification by advanced oxidation processes: Homogeneous and heterogeneous Fenton and H2O2 photo-assisted reactions

The oxidation of lignin in synthetic aqueous solutions as well as in the biologically treated pulp-and-paper mill wastewater with hydrogen peroxide was studied in various methods: hydrogen peroxide UV-photolysis, homogeneous, heterogeneous and UV-assisted heterogeneous Fenton reactions, catalysed by FeZSM-5 zeolite. Contrasting the low-molecular organic contaminants, the oxidation of lignin in aqueous solutions was drastically slowed down in presence of heterogeneous FeZSM-5 zeolite, showing the superior performance of acidic homogeneous Fenton and hydrogen peroxide photolysis. This is explained by steric hindrance in oxidation of lignin with OH radicals on the catalyst surface and possible deactivation of lignin molecules adsorbed on the zeolite. The hydrogen peroxide photolysis among the studied delignification methods appeared to be the most efficient one in a wide range of pH.     

Water delignification by advanced oxidation processes: Homogeneous and heterogeneous Fenton and H2O2 photo-assisted reactions

The oxidation of lignin in synthetic aqueous solutions as well as in the biologically treated pulp-and-paper mill wastewater with hydrogen peroxide was studied in various methods: hydrogen peroxide UV-photolysis, homogeneous, heterogeneous and UV-assisted heterogeneous Fenton reactions, catalysed by FeZSM-5 zeolite. Contrasting the low-molecular organic contaminants, the oxidation of lignin in aqueous solutions was drastically slowed down in presence of heterogeneous FeZSM-5 zeolite, showing the superior performance of acidic homogeneous Fenton and hydrogen peroxide photolysis. This is explained by steric hindrance in oxidation of lignin with OH radicals on the catalyst surface and possible deactivation of lignin molecules adsorbed on the zeolite. The hydrogen peroxide photolysis among the studied delignification methods appeared to be the most efficient one in a wide range of pH.     

回流固定床臭氧催化氧化煤化工反渗透浓水

设计了一种具有回流的固定床臭氧催化氧化反应装置,对浸渍法制得的α-Fe₂O₃/γ-Al₂O₃催化剂的性能进行了表征,并利用其在回流固定床反应装置中对煤化工反渗透浓水的臭氧催化氧化性能进行了研究。结果表明：α-Fe₂O₃/γ-Al₂O₃的比表面积、平均孔径、总孔容和活性组分α-Fe₂O₃含量分别为161.74m²/g、10nm、0.4533cm³/g和8.73%。反渗透浓水COD去除率随催化剂装填高度、臭氧投加浓度和过氧化氢投加量的增加而均呈现为先增加、后降低的变化趋势,回流可显著地提高废水COD去除率,适宜的催化剂装填高度、臭氧投加浓度、过氧化氢投加量和回流比分别为350mm、300mg/L、150mg/L和50%,臭氧催化氧化反渗透浓水的COD去除率达74.33%。煤化工反渗透浓水中大部分溶解性有机物和腐殖酸类物质均被臭氧催化氧化分解。     

Kinetic study and hydrogen peroxide consumption of phenolic compounds oxidation by Fenton’s reagent

Synthetic solutions of phenol, o-, m- and p-cresol were oxidised by using Fenton’s reagent. The application of substoichiometric dosage of H₂O₂ led to the formation of intermediate compounds, continuing later the oxidation to complete oxidation. An important objective was to analyze the effect of hydrogen peroxide dosage applied and the reaction pH together with the iron oxidation state on the degradation level. A kinetic model was derived from a reaction mechanism postulated which was used to analyze the results of the experiments. Another aim was to analyze the hydrogen peroxide consumption. Noteworthy results include an increase in oxidant consumption to intensify phenol removal. Furthermore, oxidant consumption was analyzed through the ratio H₂O₂ to phenol removed and the average specific rate of removal (ASRR). By analyzing these two parameters it has been possible to ascertain the most favorable strategy for an efficient application of H₂O₂.     

Anodic oxidation of phenol for waste water treatment

The electrochemical oxidation of phenol for waste water treatment applications was investigated on lead dioxide packedbed anodes. Cells were operated in both batch and continuous modes with feed streams up to 1100 mg/l phenol dissolved in aqueous solutions of Na₂SO₄ and H₂SO₄ or NaOH. All the phenol in solution could be readily oxidized but complete total organic carbon (T.O.C.) removal was more difficult. The percent phenol oxidized increased with increasing current density, and decreased as initial phenol concentration, electrolyte flow rate, pH and anode particle size were increased. Results are compared to simple mathematical models.     

Anodic oxidation of phenol for waste water treatment

The electrochemical oxidation of phenol for waste water treatment applications was investigated on lead dioxide packed-bed anodes. Cells were operated in both batch and continuous modes with feed streams up to 1100 nig/1 phenol dissolved in aqueous solutions of Na₂SO₄ and H₂SO₄ or NaOH. All the phenol in solution could be readily oxidized but complete total organic carbon (T.O.C.) removal was more difficult. The percent phenol oxidized increased with increasing current density, and decreased as initial phenol concentration, electrolyte flow rate, pH and anode particle size were increased. Results are compared to simple mathematical models.     

Reverse osmosis separation of phenols in aqueous solutions using porous cellulose acetate membranes

Reverse osmosis separations of phenol (9.4 to 108 ppm), p-cresol (108 ppm), and p-chlorophenol (129 ppm) were studied using Loeb-Sourirajan-type porous cellulose acetate membranes, and single-solute aqueous feed solutions at 500 psig and the indicated solute concentrations. It was found that, by dissociating the solute by changing the pH of the feed solution, all the above phenols could be separated by reverse osmosis. Solute separation increased with increase in the degree of dissociation of the solute in the feed solution; and, by the appropriate choice of pore size on the membrane surface, separations of phenol approaching the degree of dissociation of phenol in the feed solution could be obtained under the operating conditions used. Similar experiments using aniline (93 ppm) as the solute showed that dissociation of solute molecules in the feed solution could be a technique generally applicable for the reverse osmosis separation of nonionic solutes in aqueous solution. The effects of operating pressure in the range 250 to 1500 psig and pore size on the membrane surface on the separation of un-ionized phenol and p-chlorophenol showed that, with respect to single-solute aqueous feed solutions of phenols, the component whose relative acidity was greater was preferentially sorbed at the cellulose acetate membrane—aqueous solution interface, and the solute concentration in the membrane-permeated product solution was a function of the extent and mobility of each of the sorbed species.     

Direct hydro-alcohol thermal synthesis of special core–shell structured Fe-doped titania microspheres with extended visible light response and enhanced photoactivity

The influence of ultrasound at 24 kHz on the heterogeneous aqueous oxidation of phenol over RuI₃ with hydrogen peroxide (H₂O₂) was studied isothermally at 298 K. Effect of ultrasound irradiation on catalytic properties and performance of RuI₃ has been studied in details by means of scanning electron microscopy (SEM), X-ray powder diffraction (XRD), dispersion analyzer and a surface analyzer. Turn over frequency of the catalyst was also calculated. In this work, experimental design methodology was applied to optimize the degradation of phenol in aqueous solution, while minimizing an excessive consumption of chemical reagents. The independent variables considered were the catalyst load and oxidant concentration. The multivariate experimental design allowed the development of empiric non-linear quadratic models for total organic carbon (TOC) removal after 120 and 240 min of the reaction, and the time needed for total hydrogen peroxide consumption, which were adequate to predict responses in all of the range of experimental conditions used. Ruthenium leaching was not detected from samples studied at different stages of the reaction, indicating stability of the chosen catalyst. A reaction scheme involving radical species (OH, HO₂) was proposed to explain phenol conversion. Ultrasound-assisted catalytic oxidation demonstrated nearly two-fold increase in phenol conversion (up to 70%), contrary to 31% obtained during silent process. High catalytic activity of RuI₃ associated with isothermal reaction conditions at circum neutral pH was capable to extend the applicability of such catalyst in ultrasound-assisted oxidation processes.     

The electrochemical oxidation of aqueous phenol at a glassy carbon electrode

The electrooxidation of phenol is of interest as a model compound for the treatment of aqueous organic wastes. The effect of voltage, concentration and temperature on the electrochemical oxidation of acidic dilute aqueous solutions of phenol was studied. Electrolysis was carried out by recirculating phenol solutions through a flow-by electrochemical reactor employing a reticulated glassy carbon anode. Concentrations of phenol and some breakdown products were monitored using HPLC analysis. Increased voltage was found to shift the product distribution to favour more oxidized products but also to increase electrode corrosion and decrease current efficiency. Higher phenol concentrations (over the range of 5-20 mmol/L) showed a shift in product distribution to favour less oxidized, mostly insoluble products. Elevated temperatures (about 50°C and higher) showed a marked ability to reduce electrode passivation and increase the phenol oxidation rate.