A practical parametrical characterization of the Fenton and the photo‐Fenton sulfamethazine treatment using semi‐empirical modeling

BACKGROUND: Sulfamethazine (SMT) has received little attention in the water treatment literature. Yet, SMT is among the non‐biodegradable substances increasingly found in aqueous media and affecting both public health and wastewater treatments. For a long time, advanced oxidation processes (AOPs) were studied via pure empirical modeling, although the surface response models resulting from lumped information (TOC, COD, etc.) present limitations regarding extrapolation and optimization. Conversely, detailed first‐principles modeling may not be affordable due to the computational burden and the chemical analysis needs. Thus, a balanced approach may be practical in many cases. RESULTS: Experiments on SMT solutions (500 mL, 50 mg L^?1) were performed under conditions set by an experimental design. A set of replicated degradation time‐profiles (TOC and SMT concentrations) was obtained and a semi‐empirical kinetic model was fitted to these data to determine maximum conversion and kinetic rate. CONCLUSIONS: SMT can be completely degraded from water via photo‐Fenton treatment. Conditions for this treatment were investigated and its outcomes were systematically characterized by a simple kinetic model and two lumped parameters, conversion and kinetic rate. Both, the model and the corresponding parametrical characterization are introduced as a means to discriminate the most efficient treatment conditions in a practical and efficient way. Copyright © 2011 Society of Chemical Industry     

Heterogeneous photo-Fenton oxidation of reactive azo dye solutions using iron exchanged zeolite as a catalyst

The heterogeneous photo-Fenton-type oxidation of reactive azo dye solutions has been investigated in a quartz batch reactor using artificial UVA as a light source. Fe-exchanged zeolite has been used as a heterogeneous catalyst in the process. The effect of various process variables on decolorization performance of the process was evaluated by examining temperature, pH, H₂O₂ dosage, catalyst loading, initial dye concentration and light intensity. The optimal operational parameters were found as follows: 35 °C, pH as solution pH 5.2, 15 mmol H₂O₂ dosage, 1 g/L catalyst loading. Stability and reuse of the catalyst were also tested. Mineralization and comparison with homogenous photo-Fenton process were evaluated by analyzing color removal and total organic carbon (TOC) values.     

Advanced oxidation processes for the degradation of p‐hydroxybenzoic acid 2: Photo‐assisted Fenton oxidation

Oxidation of p‐hydroxybenzoic acid in aqueous solution by the photo‐assisted Fenton reaction (Fe²⁺ + H₂O₂ + UV) has been studied. The effects of ferrous ion concentration (0.05, 0.14 and 0.29 mmol dm^?3), temperature (10, 20, 30 and 40 °C), and initial hydrogen peroxide concentration (0.7, 1.4, 2.2 and 2.9 mmol dm^?3) on the p‐hydroxybenzoic acid conversion were established. Experimental results indicate that the kinetics of this oxidation process fits pseudo‐first‐order kinetics well. The overall kinetic rate constant was split into two components: direct oxidation by UV radiation (photolysis) and oxidation by free radicals (mainly OH·) generated in the system. The importance of these two reaction paths for each specific value of ferrous ion concentration, temperature and initial hydrogen peroxide concentration was evaluated. A semi‐empirical expression is proposed for the overall reaction rate which takes into account both oxidation pathways and is a function of operating variables. © 2001 Society of Chemical Industry     

污泥生物炭基催化剂在高级氧化水处理的应用

污泥作为污水处理过程的残留物,含有多种重金属、有机物以及微生物等污染物,严重危害环境和人体健康.污泥衍生的生物炭基材料具有优良的孔隙结构、表面电荷分布以及含氧基团,在高级氧化水处理领域显示出极大潜力.目前,多种污泥生物炭基催化剂成功应用于光催化、过硫酸盐活化以及芬顿等氧化体系,显示出较高催化活性.系统地总结了污泥生物炭...     

Highly stable Fe/γ‐Al2O3 catalyst for catalytic wet peroxide oxidation

BACKGROUND: A highly stable Fe/γ‐Al₂O₃ catalyst for catalytic wet peroxide oxidation has been studied using phenol as target pollutant. The catalyst was prepared by incipient wetness impregnation of γ‐Al₂O₃ with an aqueous solution of Fe(NO₃)₃· 9H₂O. The influence of pH, temperature, catalyst and H₂O₂ doses, as well as the initial phenol concentration has been analyzed. RESULTS: The reaction temperature and initial pH significantly affect both phenol conversion and total organic carbon removal. Working at 50 °C, an initial pH of 3, 100 mg L^?1 of phenol, a dose of H₂O₂ corresponding to the stoichiometric amount and 1250 mg L^?1 of catalyst, complete phenol conversion and a total organic carbon removal efficiency close to 80% were achieved. When the initial phenol concentration was increased to 1500 mg L^?1, a decreased efficiency in total organic carbon removal was observed with increased leaching of iron that can be related to a higher concentration of oxalic acid, as by‐product from catalytic wet peroxide oxidation of phenol. CONCLUSION: A laboratory synthesized γ‐Al₂O₃ supported Fe has shown potential application in catalytic wet peroxide oxidation of phenolic wastewaters. The catalyst showed remarkable stability in long‐term continuous experiments with limited Fe leaching, < 3% of the initial loading. Copyright © 2010 Society of Chemical Industry     

Contributions of electrochemical oxidation to waste‐water treatment: fundamentals and review of applications

OVERVIEW: This paper provides an overview of some fundamental aspects of electrochemical oxidation and gives updated information on the application of this technology to waste‐water treatment. In recent years, electrochemical oxidation has gained increasing interest due to its outstanding technical characteristics for eliminating a wide variety of pollutants normally present in waste‐waters such as refractory organic matter, nitrogen species and microorganisms. IMPACT: The strict disposal limits and health quality standards set by legislation may be met by applying electrochemical oxidation. However, treatment costs have to be cut down before full‐scale application of this technology. Deployment of electrochemical oxidation in combination with other technologies and the use of renewable sources to power this process are two steps in this direction. APPLICATIONS: Effluents from landfill and a wide diversity of industrial effluents including the agro‐industry, chemical, textile, tannery and food industry, have been effectively treated by this technology. Its high efficiency together with its disinfection capabilities makes electro‐oxidation a suitable technology for water reuse programs. Copyright © 2009 Society of Chemical Industry     

Ethanol perm‐selective B‐ZSM‐5 zeolite membranes from dilute solutions

Boron‐substituted MFI (B‐ZSM‐5) zeolite membranes with high pervaporation (PV) performance were prepared onto seeded inexpensive macroporous α‐Al₂O₃ supports from dilute solution and explored for the separation of ethanol/water mixtures by PV. The effects of several parameters on microstructures and PV performance of the B‐ZSM‐5 membranes were examined systematically, including the seed size, synthesis temperature, crystallization time, B/Si ratio, H₂O/SiO₂ ratio and silica source. A continuous and compact B‐ZSM‐5 membrane was fabricated from solution containing 1 tetraethyl orthosilicate/0.2 tetrapropylammonium hydroxide/0.06 boric acid/600 H₂O at 448 K for 24 h, showing a separation factor of 55 and a flux of 2.6 kg/m² h along with high reproducibility for a 5 wt % ethanol/water mixture at 333 K. It was demonstrated that the incorporation of boron into mobile five (MFI) structure could increase the hydrophobicity of B‐ZSM‐5 membrane evidenced by the improved contact angle and amount of the adsorbed ethanol, and thus enhance the PV property for ethanol/water mixtures. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2447–2458, 2016     

Simultaneous removal of COD and NH3‐N in secondary effluent of high‐salinity industrial waste‐water by electrochemical oxidation

BACKGROUND: Electrochemical oxidation has been applied successfully in industrial waste‐water treatment. The simultaneous removal of COD_Cr and NH₃‐N, as well as the corresponding mechanisms and reaction zone, were examined in this study. The reaction kinetics and the significant factors that affect removal performance were also studied. RESULTS: The COD_Cr removal efficiency without chlorides in waste‐water was only 11.8% after 120 min of treatment, which was much lower than the efficiency with chlorides, and agitation did not improve the performance. When the current density was increased from 2.5 to 10 mA cm^?2, the removal efficiency was improved. The removal efficiencies of COD_Cr and NH₃‐N were less at initial pH = 11 than at pH = 3 and 8.7 (without adjustment). The COD_Cr and NH₃‐N removal efficiencies were decreased by about 30% and 50%, respectively, when the electrode distance was increased from 4 to 12 cm. Instantaneous current efficiency decreased with increase in current density. CONCLUSIONS: The degradation of pollutants occurred mainly at the boundary layer between the electrode and the bulk solution. The indirect oxidation by active chlorine generated from the chlorides was proven to be the primary mechanism of electrochemical oxidation treatment. The removal of COD_Cr in this study followed a pseudo‐first‐order kinetic model. Copyright © 2011 Society of Chemical Industry     

Kinetics of phenylurea herbicides oxidation by Fenton and photo‐Fenton processes

The chemical oxidation of four selected phenylurea herbicides (linuron, chlortoluron, diuron, and isoproturon) was studied by means of the Fenton system. The influence of the initial concentrations of hydrogen peroxide and ferrous ions, the pH and the type of buffer (perchloric acid/perchlorate, acetic acid/acetate, or phosphoric acid/phosphate) was established according to the degradation levels obtained. In the kinetic study, the general decomposition reaction was divided into two stages with different reaction rates, which was justified by considering the whole reaction mechanism for this system. In this kinetic study, a competition kinetics model, which used p‐chlorobenzoic acid as a reference compound, was applied for the evaluation of the rate constants for each reaction between the herbicides and the hydroxyl radical. The proposed values for these rate constants are: 7.5 × 10⁹ L mol^?1 s^?1 for chlortoluron, 5.6 × 10⁹ L mol^?1 s^?1 for linuron, 7.1 × 10⁹ L mol^?1 s^?1 for diuron and 5.7 × 10⁹ L mol^?1 s^?1 for isoproturon. Finally, some experiments with the photo‐Fenton system reveal increases in the decomposition levels of the herbicides, due to additional generation reactions of hydroxyl radicals. Copyright © 2007 Society of Chemical Industry     

Removal of Hg0 from flue gas using two homogeneous photo‐fenton‐like reactions

Removal of Hg⁰ using two homogeneous Photo‐Fenton‐Like reactions was first investigated in a photochemical reactor. Effects of process parameters on Hg⁰ removal were studied. Free radical and reaction products were analyzed. Removal pathways of Hg⁰ were discussed. Simultaneous removal of Hg⁰, NO, and SO₂ is also studied briefly. The results show that UV power, wavelength, H₂O₂ concentration, and solution pH have great effects on Hg⁰ removal. Hg⁰, and SO₂ concentrations, solution temperature, Fe³⁺, Cu²⁺, , and concentrations also have significant effects on Hg⁰ removal. However, concentrations of CO₂, NO, O₂, Cl^?, , , SiO₂, Al₂O₃, and Fe₂O₃ only have slight effects on Hg⁰ removal. Hg⁰/NO/SO₂ can be simultaneously removed by Photo‐Fenton‐Like reactions. ·OH was captured, and / /Hg²⁺ were also detected. Removals of Hg⁰ by photochemical oxidation and ·OH oxidation play a major role, and removal of Hg⁰ by H₂O₂ oxidation only plays a secondary role in removal of Hg⁰. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1322–1333, 2015     

Efficient mineralization of sugar industry wastewater by catalytic wet air oxidation as an eco-friendly method and its kinetic modelling

In this study, catalytic wet air oxidation using lanthanum cobalt oxide (LaCoO₃) as catalyst was employed for the efficient treatment of synthetic sugar industry wastewater in a single process. A parametric study was performed to determine the optimum conditions. The results showed that reaction temperature and theoretical air percentage were the most effective parameters. Sugar derivatives were almost completely destroyed at the optimum conditions and total organic carbon (TOC) and chemical oxygen demand (COD) removals were determined as 91% and 87%, respectively, indicating a high mineralization degree, which was the main goal of advanced oxidation. The reaction kinetics were investigated by pseudo-homogeneous and heterogeneous models based on two different parameters: sucrose and TOC concentration. The degree of fit showed that the reaction order was determined as two for the pseudo-homogeneous approach. According to the surface concentration calculations for heterogeneous models, the presence of mass transfer limitations was only observed for oxygen as gas reactant. All heterogeneous models also fitted the reaction rate data accurately, but the Mars–van Krevelen was the selected model for sucrose and TOC oxidation with the best fit.     

Enhancement of biodegradability of industrial wastewaters by chemical oxidation pre‐treatment

Chemical oxidation technologies are often employed for the treatment of complex industrial effluents that are not amenable to conventional biological methods. The role of chemical oxidation depends on the treatment objectives and may vary from partial remediation to complete mineralization. In the case of partial treatment, chemical oxidation aims at the selective removal of the more bioresistant fractions and their conversion to readily biodegradable intermediates that can subsequently be treated biologically. Coupling chemical pre‐oxidation with biological post‐treatment is conceptually beneficial as it can lead to increased overall treatment efficiencies compared with the efficiency of each individual stage. This paper reviews recent developments and highlights some important aspects that need to be addressed when considering such integrated schemes. Copyright © 2004 Society of Chemical Industry