Degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) using cobalt-peroxymonosulfate in Fenton-like process (original) (raw)
Related papers
Journal of Hazardous Materials, 2011
A central composite rotatable design and response surface methodology (RSM) were used to optimize the experimental variables of the solar photoelectro-Fenton (SPEF) treatment of the herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA). The experiments were made with a flow plant containing a Pt/air-diffusion reactor coupled to a solar compound parabolic collector (CPC) under recirculation of 10 L of 186 mg L −1 MCPA solutions in 0.05 M Na 2 SO 4 at a liquid flow rate of 180 L h −1 with an average UV irradiation intensity of about 32 W m −2 . The optimum variables found for the SPEF process were 5.0 A, 1.0 mM Fe 2+ and pH 3.0 after 120 min of electrolysis. Under these conditions, 75% of mineralization with 71% of current efficiency and 87.7 kWh kg −1 TOC of energy consumption were obtained. MCPA decayed under the attack of generated hydroxyl radicals following a pseudo-first-order kinetics. Hydroxyl radicals also destroyed 4-chloro-2-methylphenol, methylhydroquinone and methyl-p-benzoquinone detected as aromatic by-products. Glycolic, maleic, fumaric, malic, succinic, tartronic, oxalic and formic acids were identified as generated carboxylic acids, which form Fe(III) complexes that are quickly photodecarboxylated by the UV irradiation of sunlight at the CPC photoreactor. A reaction sequence for the SPEF degradation of MCPA was proposed. (E. Brillas).
2010
The oxidative degradation of a series of hydroxy and hydroxynitro derivatives of benzoic acid by Fenton-like and photo-Fenton processes was compared under identical conditions (initial concentrations, pH and temperature). In spite of closely related chemical structures, (2-hydroxybenzoic (2H-BA), 2,4-dihydroxybenzoic (24DH-BA), 2-hydroxy-5-nitrobenzoic (2H5N-BA), 4-hydroxy-3-nitrobenzoic (4H3N-BA) and 2-hydroxy-4-nitrobenzoic (2H4N-BA) acids), the degradation timescales were remarkably different. A common feature was, however, that autocatalytic decay profiles were displayed by the substrates and H 2 O 2. A simple equation, which may be used as a valuable tool for a semiquantitative analysis of the main kinetic features of the inverted "S" profiles, is presented. In addition, a method for the estimation of the relative contribution of photoinduced pathways in photo-Fenton systems (photoenhancement factors) is proposed. In order to assess the key processes governing the kinetic profiles observed, complementary studies were performed to evaluate the formation of ferric complexes, the reactivity towards HO • and Fe(II) production efficiencies. Except for 4H3N-BA, the model substrates form highly stable complexes with Fe(III). Competition experiments showed that the reactivities of both the substrates and the ferric complexes with hydroxyl radicals cannot explain the large timescale differences observed in Fenton-like and photo-Fenton systems. The comparison of Fe(II) production under irradiation in the absence of H 2 O 2 with the decay profiles observed in both Fenton-like and photo-Fenton systems confirms that the main factor controlling the autocatalytic behavior is the formation of organic intermediates that are capable of reducing Fe(III) species. An additional factor in the photo-Fenton process may be the efficiency of photoinduced Fe(II) production, which is affected by complex formation since the studied complexes exhibit a lower efficiency of Fe(III) photoreduction than the Fe(III)-aquo complex.
Solar photo-Fenton treatment of a commercial pesticide mixture
2009
The water supply situation is deteriorating globally due to economical and industrial growth. Especially in the Mediterranean basin the increase of intense agriculture caused a high consumption of fresh water and also a problematic pollution originated by pesticides and other chemical compounds. In this work the possibility of treating wastewater polluted by pesticides coming from the horticultural centre in the south of Spain, is studied. AOPs seem to be the most promising solution as a preliminary treatment of biorecalcitrant contaminants for the purpose of degrading those using an inexpensive biotreatment. AOPs are known to be the most effective way for oxidizing biorecalcitrant substances, but have the major drawback of high operation costs. The combination of a solar advanced oxidation process (AOP) and a conventional biological treatment has been reported as an attractive approach for solving this problem. This work was elaborated and carried out at the PSA (Tabernas, Spain). as a part of the FOTOBIOX project, which is focused on the optimization of a combined solar photo-Fenton/biological system for the decontamination of a pesticide mixture. Evaluating the influence of the temperature as an important factor on the photo-Fenton degradation process was the main objective of the present study. The final aim was to find the best operating conditions for the preliminary treatment of a high concentrated commercial pesticide mixture. The operational conditions should be optimized in order to minimize the costs. In this context photo-Fenton degradation experiments at four different temperatures (25, 35, 42, 50°C) were carried out and the obtained results and effects were controlled by Fenton experiments. All experiments were processed at an iron concentration of 20 mg L-1 and a pH of 2.8. Finally, selected samples from different stages of the photo-Fenton degradation process were analysed in order to determine the toxicity and biodegradability. The objective was to find the optimal point for the consequent biotreatment, and additionally prove the feasibility the proposed combined system.
Journal of environmental management, 2015
This study reports the application of the photo-Fenton process for the degradation of the herbicide 2,4-dichlorophenoxyacetic (2,4-D). The objective of this research was the evaluation of the procedure at natural pH (pH = 5) using the ferrioxalate complex as iron source at two incident irradiation levels. For this purpose, different combinations of attenuation filters from a solar simulator were tested. Since the process depends on several parameters, the influence of the temperature (T) and peroxide to 2,4-D initial concentration ratio (R) were investigated and optimized by the application of a three-level factorial experimental design combined with the Response Surface Methodology (RSM). The significance of models and their coefficients were assessed with the analysis of variance (ANOVA). The found optimal conditions were: T = 50 °C and R = 46.3 and T = 41.53 °C and R = 41.46, achieving experimental conversions of 91.4 and 95.9% for the low and high radiation levels, respectively....
Chemosphere, 2002
The photo-Fenton process using potassium ferrioxalate as a mediator was investigated for the photodegradation of dichloracetic acid (DCA) and 2,4-dichlorophenol (DCP) in aqueous medium using solar light as source of irradiation. The influence of the solution depth, the light intensity and the effect of stirring the solution during irradiation process were evaluated using DCA as a model compound. A negligible influence of stirring the solution was observed when the concentration of ferrioxalate (FeOx) was 0.8 mM and solution depth was 4.5 or 14 cm. The optimum FeOx concentration determined for solution depths between 4.5 and 14 cm was 0.8 mM considering total organic carbon (TOC) removal during DCA irradiation. The high efficiency of the photo-Fenton process was demonstrated on summer days, when only 10 min of exposition (around noon) were sufficient to completely destroy the organic carbon of a 1.0 mM DCA solution in the presence of 0.8 mM FeOx and 6.0 mM H2O2 using a solution depth of 4.5 cm. It was observed that the photodegradation efficiency increases linearly with the solar light intensity up to values around 15 W m−2 but this linear relationship does not hold above this value showing a square root dependence. The photodegradation of a solution of DCP/FeOx showed a lower TOC removal rate than that observed for DCA/FeOx, achieving ∼90% after 35 min irradiation under 19 W m−2, while under this light intensity, the same TOC removal of DCA/FeOx was achieved in only 10 min irradiation.
Journal of pharmacognosy and phytochemistry, 2024
Introduction: Synthetic organic dyes are compounds that cannot be biologically degraded. This persistence is closely related to their chemical reactivity. If an organism has no specific mechanisms either to prevent resorption of a substance, or to eliminate it once it has been absorbed, then the substance accumulates. Methodology: The present study is limited to monitoring the decolorization of aqueous solutions of orange acid 10 molecules as a function of time. More specifically, it aims to compare the performance of the "Fenton" process and the "photo-Fenton" process with regard to the degradation of orange acid 10 molecules. The "Fenton" and "photo-Fenton" processes are based on the attack of synthetic organic dyes by oxidizing, non-selective radical entities known as "hydroxyl radicals". These radicals can be generated by "Fenton" reagents (iron cations Fe2+/hydrogen peroxide molecules H202), which have been extensively studied to remove organic matter from drinking water, explosives waste, industrial and agricultural waste, and polluted soil. Results: The results of our experiments lead us to conclude that the "photo-Fenton" process increases, albeit slightly, the degradation of orange acid 10 molecules compared to the "Fenton" process, irrespective of whether the medium is acidic, neutral or basic. Conclusion: These results are one way of overcoming the problems posed by synthetic organic dyes.
Journal of Chemical Technology & Biotechnology, 2014
BACKGROUND: An experimental study of the homogeneous photo-Fenton degradation of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) is presented. Different sources of iron in water solution were studied: sulphate, oxalate and citrate complexes. The performances of these complexes were evaluated by means of two parameters: (i) the photonic efficiencies of degradation and mineralization; and (ii) the quantum efficiencies of degradation and mineralization. Moreover, in order to quantify the consumption of the oxidizing agent, two parameters were also defined and evaluated: the 'initial specific consumption of the hydrogen peroxide' and the 'minimum hydrogen peroxide consumption for complete mineralization'. RESULTS: For pH = 5 and T = 35 • C, the degradation photonic efficiency using ferric sulphate was 6 times lower than that obtained with the ferric citrate. On the contrary, at pH = 5, quantum efficiencies of mineralization close to 50% for citrate and oxalate complexes were attained. For pH = 5 and 25 or 35 • C, the initial specific consumption of hydrogen peroxide for the ferric sulphate was 5 times higher than those of the remaining complexes. However, considering all the operating conditions, the minimum hydrogen peroxide consumption for complete mineralization using the oxalate complex was always lower than or at most similar to those observed in the other two complexes. CONCLUSION: Using different sources of iron, the influence of pH and temperature on the pollutant degradation and mineralization process was determined. For pH = 5 and both temperatures, the ferric sulphate system required more than twice the time to achieve complete degradation of the herbicide. Moreover, mineralization only reached 55% after 180 min operation.
Chemosphere, 2008
Biodegradability of a partially photo-oxidized pesticide mixture is demonstrated and the effect of photo-Fenton treatment time on growth and substrate consumption of the bacteria Pseudomonas putida CECT 324 is shown. Four commercial pesticides, laition, metasystox, sevnol and ultracid, usually employed in citric orchards in eastern Spain, were chosen for these experiments. The active ingredients are, respectively, dimethoate, oxydemeton-methyl, carbaryl and methidathion. Judging by biomass measurements, dissolved organic carbon measurements and biodegradation efficiency, it may be concluded that 90 min < t 30W < 110 min is the critical point for the photo-Fenton treatment. P. putida is sensitive to photo-produced intermediates giving rise to different kinetic behaviour: longer lag phases, slower growth rates and lower carbon uptake rates. Nonetheless, the percentage of carbon consumption was over 80%, pointing out the biodegradability of the mixture. Biodegradation efficiencies (E f ) of the photo-reaction intermediates were around 60%, in small 50-ml cultures and in a 12-l bubble column bioreactor. But with the main difference that E f in the former took 120 h and the same biodegradation was reached in less than 30 h in the latter. Therefore, for qualitative results, experiments in flasks might be recommendable, but not for quantitative results for designing purposes.
Degradation of a four-pesticide mixture by combined photo-Fenton and biological oxidation
Water Research, 2009
Complete degradation of a pesticide mixture by a combination of a photo-Fenton pretreatment and an activated-sludge batch reactor is demonstrated. Four commercial pesticides, Laition, Metasystox, Sevnol and Ultracid were chosen for this experiment. The active ingredients are, respectively, dimethoate, oxydemeton-methyl, carbaryl and methidathion. The original pesticide concentration was 200 mg L À1. Biotreatment began after 31% photocatalytic mineralization, which after 5 h in a 6-L stirred batch-mode tank reactor with non-acclimated activated sludge, leaves the photo-Fenton effluent completely degraded. This biotreatment time is shorter than commonly found in municipal wastewater treatment plants (w8-10 h). Therefore, the combined process is effective for rapid pesticide degradation in wastewater with complete removal of parent compounds and the associated DOC concentration. Nonetheless, assessment of this technology should take into account higher pesticide concentrations and how this factor affects both the photocatalytic and the biological oxidation.