Photo-Fenton process at natural conditions of pH, iron, ions, and humic acids for degradation of diuron and amoxicillin

Abstract

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), 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 * Paula Osorio-Vargas

Constructing an Acidic Microenvironment by MoS2 in Heterogeneous Fenton Reaction for Pollutant Control

“…[3] However,the pH of the system often changes from neutral to acidic during or after the Fenton reaction. [4] If the pH of the system is kept neutral by using ab uffer solution, the activity of the heterogeneous Fenton reaction to degrade organic matter is extremely reduced. [5] This result is mainly because when the pH is close to neutral, Fe 2+ will react with OH À to precipitate iron oxides,such as iron hydroxide,resulting in the formation of iron sludge and as harp decrease in the decomposition efficiency of H 2 O 2 .Furthermore,the oxidation potential of COH under neutral conditions decreases,g reatly decreasing its oxidation capacity.H owever,a cidic reaction conditions not only corrode equipment but also increase the reaction cost, which is not conducive to the large-scale promotion of Fenton technology.Therefore,the development of heterogeneous Fenton reaction systems that can truly overcome the pH limitation has important scientific significance in the field of environmental pollution control.…”

Constructing an Acidic Microenvironment by MoS2 in Heterogeneous Fenton Reaction for Pollutant Control

“…Although heterogeneous Fenton techniques are considered to be able to degrade organics under neutral conditions, most reported heterogeneous Fenton techniques focus on the initial pH (pH initial ) of the reaction solution [3] . However, the pH of the system often changes from neutral to acidic during or after the Fenton reaction [4] . If the pH of the system is kept neutral by using a buffer solution, the activity of the heterogeneous Fenton reaction to degrade organic matter is extremely reduced [5] .…”

Detoxification of As(III) in Aqueous Media by Using Photo-Fenton Method

“…The extension of Fe 2+ concentration could generate more •OH radicals, and so improvement of the oxidation. In contrast, the excessive Fe 2+ could act as •OH radical scavenger (Azhdarpoor et al, 2015;Buitrago et al, 2020;Ebrahiem et al, 2017;Reza et al, 2016;Wahyuni et al, 2016;, following reaction (Eq 3), that caused the •OH radicals diminished. Then, Fe 3+ and -OH resulted from Eq.…”

“…Compared to the heterogeneous oxidation, the homogenous photo-Fenton-like (UV + H 2 O 2 ) processes posse low mass-transfer resistance and favor to faster degradation of pollutants (Lescano et al, 2011;Sorlini et al, 2010). In the photo-Fenton, OH radicals are not only produced from reaction between Fe(II) with H 2 O 2 , but can also be resulted from the H 2 O 2 irradiation with UV light, as presented as equations ( 1) and ( 2) (Azhdarpoor et al, 2015;Buitrago et al, 2020;Ebrahiem, et al, 2015;O'Dowd and Pillai, 2020;Reza et al, 2016;Villages-Guzman, et al, 2017;Wahyuni et al, 2016;.…”

“…Due to the rich • OH radicals provided, photo-Fenton method has accepted intensively attention and has been frequently used to treat a large number of organic pollutants such as dyes (Reza et al, 2016), cosmetic residual in industrial wastewater (Ebrahiem et al, 2015), anionic surfactant in the laundry wastewater (Wahyuni et al, 2016), and amoxicillin (Buitrago et al, 2020) with satisfying results. Additionally, some other studies have also examined photo-Fenton method to destroy bacteria (Villages-Guzman, et al, 2017;O'Dowd and Pillai, 2020), leach several heavy metals from sediments (Azhdarpoor et al, 2015) and oxidize Pb(II) in aqueous media to form the insoluble Pb(IV) (Wahyuni et al, 2019).…”