Degradation of Metoprolol by photo-Fenton: Comparison of different photoreactors performance (original) (raw)
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Simultaneous degradation of pharmaceuticals by classic and modified photo-Fenton process
Journal of Environmental Chemical Engineering, 2018
Pharmaceutical compounds are known to be persistent. Their presence after conventional treatments in sewage treatment plants may harm aquatic environments. The simultaneous degradation of the pharmaceuticals gemfibrozil, hydrochlorothiazide and naproxen involving photo-Fenton processes was evaluated using different sources and concentrations of iron (Fe 2+ , Fe 3+ and the iron complexes of oxalate-FeOx), initial pH (2.6, 5.0 and 7.0) and concentrations of H2O2. The classic photo-Fenton reaction (at initial pH 2.6, using Fe 2+ and Fe 3+) showed a limited efficiency in promoting gemfibrozil degradation, which, based on evidence provided by LC-MS measurements, is related to the formation of associations between this compound and iron ions. The simultaneous degradation of gemfibrozil and the other compounds was improved using FeOx (1.0 mg L-1 in iron) at an initial pH of 2.6 and 2.0 mg L-1 H2O2. In addition, using this catalyst it was possible to efficiently degrade the pharmaceuticals at an initial pH of 5.0, reaching complete degradation of these compounds with a treatment time varying between 20 and 60 min and generating a low toxicity effluent. These results highlight the potential applicability of ferrioxalate as a photocatalyst in the photo-Fenton process as an alternative method to degrade this kind of pollutant at a pH near neutrality.
Current Organic Chemistry
The aim of this paper is to provide an overview on the different approaches that can be employed to drive a photo-Fenton process under mild conditions, using both heterogeneous and homogeneous iron sources. For this purpose, sections are devoted to the following strategies: a) addition of iron at low concentrations; b) using the matrix of the effluent in order to avoid deactivation of iron; c) addition of chemical auxiliaries to form photoactive complexes with iron, such as carboxylates, chelating agents and humic-like macromolecules; d) strategies leading to the application of heterogeneous photo-Fenton process, by using iron-based solid particles or by hosting iron on different supports and; e) using heterogeneous iron sources as a reservoir for constant dosing of homogeneous iron photocatalyst. In particular, the review will focus on the elimination of emerging pollutants (e.g. drugs, personal care products or pesticides at low concentrations) which are the effluents where applying neutral photo-Fenton seems especially meaningful, although relevant works with other families of pollutants are also considered.
Environmental Science and Pollution Research, 2019
Effect of ferric ions at concentrations typically found in natural waters (0.05 to 1.06 mg L −1) and low H 2 O 2 concentrations (between 0.5 and 17.9 mg L −1) on simulated sunlight-induced (300 W m −2) photo-Fenton degradation at initial neutral pH (7.0) of amoxicillin and diuron in Milli-Q water was studied using an rotatable central composite experimental design 2 2 with a central and two axial points. H 2 O 2 concentration was the parameter playing the key role on the degradation of both pollutants. Despite that initial pH was 7.0 in Milli-Q water, this latter decreased rapidly in the first minutes, reaching values of 3.5 and 5.0 for diuron and amoxicillin respectively after 15 min of simulated sunlight irradiation. In contrast, in presence of bicarbonate/carbonate (HCO 3 − /CO 3 =), fluoride (F −), and humic acids (HAs) at concentrations found often in surface and well waters with ferric ion and H 2 O 2 concentrations of 0.3 and 9.7 and 15.2 mg L −1 respectively, both pollutants exhibited a strong degradation keeping the circumneutral pH. Amoxicillin and diuron degradation byproducts found by HPLC/MS were compatible with HO • and/or CO 3-• radical attack. Several photo-induced processes such as photo-Fenton (by dissolved ferric-HA complexes), heterogeneous photocatalysis (by colloidal iron), UV-B H 2 O 2 photolysis, irradiated-dissolved organic matter, and their reactions with pollutants would be the main oxidative route responsible of degradations. These findings demonstrated that it could be possible using iron concentrations often found in natural waters to oxidize via photo-Fenton processes among other events, organic pollutants at natural pH conditions. Keywords Circumneutral photo-Fenton. Diuron. Amoxicillin. H 2 O 2 photolysis. Water detoxification. Low iron amounts
Homogeneous photo-Fenton processes at near neutral pH: A review
Applied Catalysis B-environmental, 2017
Highlights A comprehensive literature survey on photo-Fenton processes at neutral pH Classification of modified photo-Fenton processes by chelating species adopted Mechanism of photolysis and speciation diagram of Fe(III)-ligand complexes Comparison of light absorption, biodegradation, and toxicity properties Suitable criteria for choosing chelating agent and operating conditions
Treatment of organic pollutants by homogeneous and heterogeneous Fenton reaction processes
Environmental Chemistry Letters, 2018
Nowadays, the water ecosystem is being polluted due to the rapid industrialization and massive use of antibiotics, fertilizers, cosmetics, paints, and other chemicals. Chemical oxidation is one of the most applied processes to degrade contaminants in water. However, chemicals are often unable to completely mineralize the pollutants. Enhanced pollutant degradation can be achieved by Fenton reaction and related processes. As a consequence, Fenton reactions have received great attention in the treatment of domestic and industrial wastewater effluents. Currently, homogeneous and heterogeneous Fenton processes are being investigated intensively and optimized for applications, either alone or in a combination of other processes. This review presents fundamental chemistry involved in various kinds of homogeneous Fenton reactions, which include classical Fenton, electro-Fenton, photo-Fenton, electro-Fenton, sono-electro-Fenton, and solar photoelectron-Fenton. In the homogeneous Fenton reaction process, the molar ratio of iron(II) and hydrogen peroxide, and the pH usually determine the effectiveness of removing target pollutants and subsequently their mineralization, monitored by a decrease in levels of total organic carbon or chemical oxygen demand. We present catalysts used in heterogeneous Fenton or Fenton-like reactions, such as H 2 O 2-Fe 3+ (solid)/nano-zero-valent iron/immobilized iron and electro-Fenton-pyrite. Surface properties of heterogeneous catalysts generally control the efficiency to degrade pollutants. Examples of Fenton reactions are demonstrated to degrade and mineralize a wide range of water pollutants in real industrial wastewaters, such as dyes and phenols. Removal of various antibiotics by homogeneous and heterogeneous Fenton reactions is exemplified.
Evaluation of photo-Fenton degradation of reactive black 5 using response surface method
2007
Photo-Fenton degradation of a reactive dyestuff, Reactive Black 5, was investigated in this study. The effects of UV light on Fenton Reagent process and the influence of reagents dosage, UV light intensity and initial dissolved oxygen concentration on photo-Fenton were explored. The experiments were conducted in a 3-L batch-mode reactor and were designed using Response Surface Method. The performance of the systems was assessed based on TOC removal. UV light was found to increase the efficiency of Fenton Reagent process by about 100%, reduce the reaction time by half and lessen the iron requirement by about 85%. Within the range used in the experiments, UV light intensity, and iron and hydrogen peroxide dosages were found to have significant positive influence on the efficiency of the photo-Fenton process. Iron dosage was significant in the early stage, peroxide dosage was significant at the later stage while UV light intensity was significant throughout the reaction period. The initial dissolved oxygen concentration was not a significant factor for photo-Fenton. Depending on the conditions of the reaction, TOC removal of 41.3% to 88.2% was obtained by photo-Fenton oxidation after 30 minutes.
Chemical Engineering Journal, 2016
An industrial wastewater effluent from the beverage industry has been treated in a pilot plant using a photo-Fenton process, which was intensified with persulfate. Under optimal conditions in a photo-Fenton process, 53% mineralization was achieved after two hours. The remaining Total Organic Carbon (TOC) was mainly composed of acetate and formate, whose decarboxylation was limited via hydroxyl radical reactions. Thus, persulfate (PS) was added to the system after 2 hours to obtain a more efficient decarboxylation by sulfate radicals (SR, SO 4 •-). Different conditions were studied to activate PS (UV-C, thermal, Fe(II) and H 2 O 2). The hydroxyl radical concentration in the solution was also measured, which supports the results in the sulfate-radical-based process. The combined treatment with UV-C irradiation and thermally activated persulfate enhanced the mineralization efficiency. Under the best conditions, 76 % mineralization was achieved in 4 hours: photo-Fenton reaction (UV-C/Fe(II)/H 2 O 2) was achieved in the first two hours and UV-C/Fe(II)/H 2 O 2 /PS/thermal in the second two hours (65ºC) (pH = 2.9, [H 2 O 2 ]= 4000 mg/L; [Fe(II)]= 375 mg/L). Strong inhibition of the oxidation of Fe(III)-oxalic complexes in the last stage of the treatment is not probable because its removal by precipitation does not improve the mineralization rate. Thus, the low reactivity of acetic acid and the formation of oxalic acid are responsible for the slow mineralization at the end of the process. The formation of undesirable chlorinated oxidation products is also improbable.
Fenton chemistry encompasses reactions of hydrogen peroxide in the presence of iron to generate highly reactive species such as the hydroxyl radical and possibly others. In this review, the complex mechanisms of Fenton and Fenton-like reactions and the important factors influencing these reactions, from both a fundamental and practical perspective, in applications to water and soil treatment, are discussed. The review covers modified versions including the photoassisted Fenton reaction, use of chelated iron, electro-Fenton reactions, and Fenton reactions using heterogeneous catalysts. Sections are devoted to nonclassical pathways, by-products, kinetics and process modeling, experimental design methodology, soil and aquifer treatment, use of Fenton in combination with other advanced oxidation processes or biodegradation, economic comparison with other advanced oxidation processes, and case studies.