Online measurement and timely optimization of hydrogen peroxide concentration in photo-Fenton processes: Application of an Arduino device

In this project decolorization and mineralization of synthetic wastewater containing acid red 33 (AR33) was investigated by Fenton and photo Fenton processes in a batch photo reactor. A comparative assessment using Fenton and photo Fenton processes was performed after initial optimization studies such as varying pH, the concentration of pollutant, peroxide and iron. The color removal and mineralization efficiency of AR33 were calculated by Spectrophotometric and chemical oxygen demand (COD) tests. The degradation efficiency in photo Fenton process (98.5% in 10 min of reaction) was higher than Fenton ones (97.5% in 30 min). After 60 min of reaction, the removal of COD in photo Fenton and Fenton processes was 71% and 37.5%, respectively. Therefore, photo Fenton was the most effective process in partial mineralization of AR33. Kinetic constants were evaluated using pseudo first order equations to obtain the rate constant, K.

Direct Blue 71 removal by electrocoagulation sludge recycling in photo-Fenton process: response surface modeling and optimization

Effluents from radiographic X-ray film developing processes feature a high contaminant load (COD about 70000 mg/L and total phenols concentration about 16956 mg/L). Photo-Fenton's are potentially useful oxidation processes for destroying toxic organic compounds in water. In these reactions, hydrogen peroxide is combined with ferrous or ferric iron in the presence of light to generate hydroxyl radicals (·OH). The photo-Fenton process was explored as a photochemical treatment to degrade wastewater from radiographic X-ray film developing processes coming from odontologic clinics. A response surface methodology was applied to optimize the photo-Fenton oxidation process conditions using total phenol removal as the target parameter to be optimized, and the reagent concentrations, as related to the initial concentration of organic matter in the effluent, and time and pH as the control factors to be optimized. The best results in terms of maximal total phenol removal and economic process were achieved when wastewater samples were treated at pH 5 in the presence of hydrogen peroxide and iron in the ratios [total phenols]:[H2O2] 1:3 w/w and [Fe2+]:[H2O2] 1:18 w/w and time 1 h.

ABSTRACT. In this study, the effect of Fenton and photo-Fenton processes, which are advanced oxidation processes that use the hydroxyl radical for the decolorization of Novacron Black from aqueous solutions, on decolorization was investigated. Optimum levels of initial pH, temperature, hydrogen peroxide concentration, initial dyestuff concentration, and iron concentration were determined. Initial pH, Fe2+ concentration, temperature, and initial Novacron Black concentration are the most effective experimental parameters in the decolorization of Novacron Black with Fenton and photo-Fenton processes. While the Novacron Black concentration was 200 mg/L, the H2O2 concentration was 100 mg/L, the initial solution pH was 3, and the temperature was 20 °C, a decolorization efficiency of 82.1% was obtained in the Fenton process at a concentration of 5 mg/L Fe2+, while in the photo-Fenton process at a 2 mg/L Fe2+ concentration, a 94.6% decolorization efficiency was obtained. Upon decolorization of Novacron Black, the photo-Fenton process had a higher removal efficiency than the Fenton process, even at low iron concentrations. From data obtained at various concentrations of initial Novacron Black, the non-linear method was used to determine the decolorization kinetics of Novacron Black. Finally, an economic analysis was carried out to compare the differences in operating costs between Fenton and photo-Fenton processes. KEY WORDS: Advanced oxidation process, Decolorization, Fenton oxidation, Kinetic model, Photo-Fenton oxidation Bull. Chem. Soc. Ethiop. 2023, 37(1), 197-210. DOI: https://dx.doi.org/10.4314/bcse.v37i1.16

The oxidation potentiality of simulated aqueous solution of 2-chlorophenol (2-CP) by Fenton's reagent was assessed for wastewater treatment. Batch experiments were carried out to investigate the effects of pH, hydrogen peroxide (H2O2), and ferrous ion (Fe2+) concentrations. Degradation reaction occurred within a limited pH range of 2.5–4.0. Maximum degradation occurred at a concentration of 22 mM of H2O2 and at 0.45 mM of Fe2+. Influence of temperature on degradation of 2-CP was investigated. Arrhenius plot for the degradation of 2-CP at various temperatures was plotted based on the experimental data. The role of solar light and UV in photo-fenton degradation of 2-CP was investigated and compared with Fenton process. In both Fenton and photo-fenton processes, free chloride ion generated from 2-CP degradation process reached a maximum concentration at a very short interval of time. Maximum DOC removal of 39% was achieved in Fenton's process (i.e.,) only 2/5th of compound was mineralized. The efficiency of mineralization was considerably improved to 95–97% in photo-fenton processes. Low molecular weight aliphatic organic compounds like oxalic acid and acetic acid formed during the reaction were monitored for Fenton's process. The fate of these stable intermediates compounds in photo-fenton processes were also discussed.

This work addresses the dosage of H2O2 in photo-Fenton processes and the monitoring of Dissolved oxygen (DO) that can be used to drive the dosage of H2O2. The objective of this work is to show that a smarter monitoring of a process variable such as DO (for which on-line measurement can be inexpensively obtained) enables the proposal and implementation of efficient dosage strategies. The work explores the application of a recent proposed strategy consisting of: (i) initial H2O2 addition, (ii) continuous H2O2 addition until a DO set up is reached, and (iii) automatic H2O2 addition by an on-off control system based on DO slope monitoring, and applies it to the treatment of different individual contaminants and their mixtures (paracetamol and sulfamethazine). The assays performed following this dosage strategy showed improved values of TOC removed per H2O2 consumed. For the case of sulfamethazine, this improvement increased up to 25–35% with respect to the efficiency obtained without dosage. Furthermore, a deeper analysis of the results allowed detecting and assessing the opportunity to redesign the dosage scheme and reduce its complexity and the number of control parameters. The promising results obtained are discussed in regard of future research into further increasing the simplicity and robustness of this generalized control strategy that improves the applicability of the photo-Fenton process by reducing its operating costs and increasing automation.

In the present work, the treatment of a leachate from Fez city urban sanitary landfill (Morocco) was evaluated using different advanced oxidation processes (AOPs), such as, Fenton (Fe2+/H2O2), photo-Fenton (Fe2+/H2O2/UV-A), UV-A and UV-A/H2O2. The leachate was characterized by high chemical oxygen demand (COD), low biodegradability and intense dark color. The treatment efficiency was evaluated as a function of different operation variables ([H2O2], [Fe2+], UV-A irradiance), resulting in COD removals between 30% and 77%. Removal efficiencies decreased in the following order: photo-Fenton> Fenton> UV-A/H2O2> UV-A. Thus, a detailed experimental analysis was carried out to analyze the effect of hydrogen peroxide and iron concentration in the photo-Fenton process. It was observed that: (a) COD removal ranged from 4% to 84% depending on the H2O2 dose, (b) COD removal increased by adding the H2O2 dose in multiple steps (84%) and (c) iron concentration corresponding to a Fe2+/COD mass ratio = 0.35 was found to be the most favorable. At optimum conditions, COD removal was 70% and 84% for Fenton and photo–Fenton processes, respectively. In addition, the optimum contact time for both processes was 1 hr. Finally, the results of this study showed that the Fenton and photo-Fenton process is capable of achieving high levels of COD removal.

The photo-Fenton process is an advanced oxidation process that uses the hydroxyl radical to disinfect and decontaminate water. Its non-selectivity makes it ideal for the removal of a range of microorganisms including those with antimicrobial resistance. Optimum parameters such as pH, temperature, hydrogen peroxide and iron concentrations and the intensity and wavelength of light irradiation are important to carry out an efficient photo-Fenton process. Traditionally photo-Fenton has been carried out at low acidic pH to obtain greater efficiency, but recent studies have been performed at near neutral. The current review examines the effectiveness of the photo-Fenton process at a near neutral pH for the disinfection of water. The optimal pH was seen to be at 2.8, with the efficiency of the photo-Fenton process decreasing as the pH rises. The optimal reagent concentrations showed considerable variation depending on the iron catalyst used and the iron to hydrogen peroxide concentration used. The effect of irradiance and temperature showed improved efficiency with higher levels. Different types of microorganisms such as E. coli, Pseudomonas sp., Enterococcus faecalis, Klebsiella pneumonia, Salmonella spp., total Coliforms, MRSA, MSSA, B. subtilis, Clostridium sp., Faecal Coliform, MS2 coliphage and Curvularia sp. are also examined and the effect the process will have on them. The design of reactors, such as compound parabolic reactors are also examined. The impact of light sources, including the recent reports on LEDs, on the production of hydrogen peroxide and thereby the improvement in the overall photo-Fenton disinfection is also discussed in detail. Finally, a techno-economic analysis to explain various costs associated with photo-Fenton process has also been carried out. It is concluded that the development of new heterogeneous supported immobilised catalysts that could work at the near neutral pH is an area, which requires considerable future research.

This study evaluated, at laboratory scale, if the using iron naturally present (0.3mgL-1) and adding 10mgL-1 of hydrogen peroxide was effective to remove 24.3mgL-1 of 2,4-dichlorophenoxyacetic acid (2,4-D) from groundwater samples by simulated solar irradiation (global intensity=300Wm-2). Under these conditions, the degradation of 2,4-D reached 75.2% and the apparition of its main oxidation byproduct 2,4-dichlorophenol (DCP) was observed. On the other hand, pH exhibited an increasing from 7.0 to 8.3 during the experiment. Experiments using Milli-Q water at pH7.0, iron, and H2O2 concentrations of 0.3 and 10mgL-1, respectively, were carried out in order to study the effect of ions such as carbonate species, phosphate, and fluoride in typical concentrations often found in groundwater. Ion concentrations were combined by using a factorial experimental design 23. Results showed that carbonates and fluoride did not produce a detrimental effect on the 2,4-D degradation, while phosphate inhibited the process. In this case, the pH increased also from 7.0 to 7.95 and 8.99. Effect of parameters such as pH, iron concentration, and hydrogen peroxide concentration on the 2,4-D degradation by the photo-Fenton process in groundwater was evaluated by using a factorial experimental design 23. Results showed that the pH was the main parameter affecting the process. This study shows for the first time that using the photo-Fenton process at circumneutral pH and iron naturally present seems to be a promising process to remove pesticides from groundwater.

Advanced treatment of landfill leachate using integrated coagulation/ photo-Fenton process through in-situ generated nascent Al3+ and H2O2 by Cl, N co-doped aluminum-graphite composite

The oxidative degradation of non-ionic surfactants by the photo-Fenton process has been examined. The photo-Fenton degradation kinetics of mixtures of non-ionic surfactant and other type surfactants has been also investigated since mixtures of non-ionic and ionic surfactants are commonly used to utilize their synergistic effects in many practices. Effects of operating parameters such as dosages of Fenton reagents (iron and hydrogen peroxide) and UV light intensity on the degradation of commercial non-ionic surfactant Sannonic SS-90 (polyoxyethylene alkyl ether) were studied. Although the dosages of the Fenton reagents increased the degradation rate up to the optimum dosages, further addition of the reagents could not enhance the degradation rate. Excess dosages of Fe and H2O2 caused excess OH radicals which could be a scavenger of OH radicals and as a result could not enhance the degradation of the surfactant. The increase in UV light intensity resulting in the faster photo-Fenton process or the enhancement of OH radical formation rate led to the increase in degradation rate of non-ionic surfactant. Although the existence of the anionic surfactant (sodium dodecylbenzene sulphonate) would inhibit the degradation of the non-ionic surfactant due to the formation of complex with Fe ion, the existence of cationic surfactant (dodecyltrimethyl ammonium chloride) affected insignificantly the photo-Fenton degradation process of the non-ionic surfactant.

This study was conducted to evaluate the COD removal efficiency of Photo-Fenton oxidation process. The reagents used in the Photo-Fenton process are catalyst Fe2+ and H2O2 as oxidizing agent. A 16W UV lamp was used to carry out the experiments. All the experiments were performed in batch mode to investigate the influence of operating conditions viz., Fenton reagents dosage, molar ratio and reaction time. The maximum COD removal observed was 68% under optimum operating conditions. The operating conditions H2O2/Fe2+ molar ratio = 3 and reaction time = 90 minutes were found to optimum. The dosages of Fenton reagents i.e. hydrogen peroxide and Fe2+ were optimum at 0.09 mol/L and 0.03 mol/L respectively.

Iron redox cycling in hydroxyl radical generation during the photo-Fenton oxidative degradation: Dynamic change of hydroxyl radical concentration

An artificial neural network (ANN) was implemented for modeling phenol mineralization in aqueous solution using the photo-Fenton process. The experiments were conducted in a photochemical multi-lamp reactor equipped with twelve fluorescent black light lamps (40 W each) irradiating UV light. A three-layer neural network was optimized in order to model the behavior of the process. The concentrations of ferrous ions and hydrogen peroxide, and the reaction time were introduced as inputs of the network and the efficiency of phenol mineralization was expressed in terms of dissolved organic carbon (DOC) as an output. Both concentrations of Fe(2+) and H2O2 were shown to be significant parameters on the phenol mineralization process. The ANN model provided the best result through the application of six neurons in the hidden layer, resulting in a high determination coefficient. The ANN model was shown to be efficient in the simulation of phenol mineralization through the photo-Fenton process using a multi-lamp reactor.

Degradation of microcystin-LR toxin by Fenton and Photo-Fenton processes