Degradation of 2,4-dichlorophenoxyacetic acid by photolysis and photo-Fenton oxidation

Abstract

A B S T R A C TThis work aimed at comparing different UV and H 2 O 2 based advanced oxidation processes (AOPs) −photolysis, UV/H 2 O 2 , and photo-Fenton reaction-for the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D), a common ingredient of phytosanitary products. The influence of oxidant dose (H 2 O 2 ), catalyst type and concentration, pollutant concentration, water matrix and irradiation spectrum was also analyzed. Under reference conditions (25 mg/L of 2,4-D in osmosed water), photo-Fenton oxidation using Fe 2+ salt, initial pH value of 2.6 and a lowpressure mercury vapor lamp (10 W, λ = 254 nm) yielded more than 85% of pollutant mineralization in one hour, as compared to 60% and less than 10% for UV/H 2 O 2 and photolysis, respectively. Such a performance could be achieved in 10 min only when applying optimal concentration range for Fenton's reagent (2 to 5 times the stoichiometric amount of H 2 O 2 and oxidant-to-catalyst molar ratio from 25 to 40). Conversely, addition of a ZSM-5 zeolite bearing iron active sites albeit catalyzing Fenton oxidation at natural pHdid not bring additional benefit to UV/H 2 O 2 process. Use of wastewater treatment plant effluent as aqueous matrix or irradiation in the UVA-visible range somewhat lowered the fficiency of the homogeneous photo-Fenton process. Nonetheless, bench scale experiments under sunlight gave promising results for 2,4 D remediation in wastewater, leading to over 80% conversion of the pollutant within ten minutes.

Degradation of ibuprofen by photo-based advanced oxidation processes: exploring methods of activation and related reaction routes

“…The IBP oxidation rate increased with the H 2 O 2 concentration up to 6.4 mM before leveling off, indicating that • OH scavenging occurs at high H 2 O 2 excess (Eq. 9) (Cruz González et al 2018;Adak et al 2019).…”

Effect of the Precursor on the Synthesis of ZnO and Its Photocatalytic Activity

“…The 2,4-DCP and 2,4-D are pesticides widely used in the agro-industry to deal with certain pests which are a threat to agriculture. Although the Federal Drugs Administration (FDA) and World Health Organization (WHO) have banned these products in Mexico, they are still used [3][4][5]. When the concentration of 2,4 D and 2,4-DCP is significant, these compounds can reach the aquifers and lead to intestinal diseases, and their accumulation in humans can cause carcinogenesis after water consumption [6]; the presence of these compounds in water has been reported [7,8].…”

Occurrence and transformation of phenoxy acids in aquatic environment and photochemical methods of their removal: a review

“…The activity of bacteria in relation to individual phenoxy acids, even of similar structure, is not identical. Therefore, the threshold concentration value shows differentiation for different bacterial strains and also depends on physicochemical properties of water (Gözdereliler 2012). When pesticide concentrations decrease below the threshold value, metabolic processes are too slow to provide sufficient amounts of energy for microbial proliferation.…”

“…In addition, only some types of microorganisms are adapted to use low concentrations of substrates. Therefore, degradation of the compound at low concentration levels may show differences in relation to its degradation at high concentrations (Tros et al 1996;Gözdereliler 2012). Literature data indicate that some indigenous bacteria belonging to oligotrophs are able to metabolize low concentrations of impurities.…”

“…However, there is little information in the literature about degradation of phenoxy acids at low concentrations. Gözdereliler (2012) has isolated from groundwater sediments bacterial strains that have created an effective mechanism of degradation of MCPA, present in low concentration (1 μg L −1 ). The isolated strains b elonge d t o t he ge nera Pro t eobac teria, Achromobacter, Pseudomonas, Variovorax, Cupriavidus, and Sphingomonas.…”