Transformation of Atrazine to Hydroxyatrazine with Alkali-H₂O₂ Treatment: An Efficient Dechlorination Strategy under Alkaline Conditions

Abstract

In this study, we develop a new strategy for dechlorination of atrazine using hydrogen peroxide (H2O2) at pH ≥ 11.0 without addition of any other reagents at room temperature. Scavenging experiments, isotope experiments, theoretical calculation, and high resolution mass spectra reveal that the hydroperoxide anion (HO2 –), the product of deprotonation of H2O2, can induce dechlorination of atrazine to form triazinyl hydroperoxide (C8H14N5OOH) via nucleophilic substitution. Subsequently, the as-obtained C8H14N5OOH reacts with reductive HO2 – to generate C8H14N5OOOH. Finally, hydroxyatrazine (C8H14N5OH) is generated through intramolecular redox decomposition of C8H14N5OOOH. Even though atrazine cannot be completely mineralized by this method, this H2O2-induced dechlorination of atrazine can greatly decrease their biological toxicity. In addition, the alkaline H2O2 system also achieves outstanding performance in dechlorination of other typical chlorotriazine herbicides such as simazine, propazine, and terbutylazine. The typical coexisted ions of Cl– and NH4 + show negligible effect on degradation of these chlorotriazine herbicides. This study will have an important implication on the potential application of alkali-H2O2 for treatment of chlorotriazines manufacturing wastewater.

Application of Raney Al-Ni Alloy for Simple Hydrodehalogenation of Diclofenac and Other Halogenated Biocidal Contaminants in Alkaline Aqueous Solution under Ambient Conditions

“…Leonard et al described nickel catalyst effective for HDC of atrazine caused by pressurized gaseous hydrogen at 5 MPa and 140 °C [ 40 ]. Both atrazine and simazine are detoxified by nucleophilic substitution of bound chlorine by the action of alkaline hydrogen peroxide solution [ 41 ].…”

Kinetic and Mechanistic Insights into the Oxidative Transformation of Atrazine by Aqueous Fe(IV): Comparison with Hydroxyl and Sulfate Radicals

“…Dechlorination-hydroxylation of ATZ by Fe­(IV), illustrated by path 3 of Scheme , resulted in the formation of two byproducts: ODIT and DEHA. Dechlorination of ATZ with forming nontoxic hydroxyatrazine is regarded as an efficient detoxification strategy, and hence, this pathway has been intensively investigated recently. ,, The direct dechlorination-hydroxylation of ATZ predominated during the UV irradiation process, as described by Scheme S4. Mu et al and Torrents et al proposed that ATZ was first transformed to its excited triplet states ( 3 ATZ*) by UV irradiation and then the H 2 O molecule-assisted nucleophilic substitution of 3 ATZ* induced the formation of hydroxyatrazine (OIET, 4-ethylamino-6-isopropylamino-2-hydroxy- s -triazine), which could be further transformed to its dealkylation (e.g., DEHA) and alkylic-oxidation (e.g., ODIT) byproducts.…”

Defective Layered Double Hydroxide Nanosheet Boosts Electrocatalytic Hydrodechlorination Reaction on Supported Palladium Nanoparticles

“…Correspondingly, as observed in Figure 5b, the 2,4-DCP removal efficiency of the electrode drops by 24.1% and, intriguingly, gets close to that of Pd/Ni(OH) 2 . To exclude the occupation of the active Pd sites by PO 4 3− that might also be detrimental to EHDC, we compare the EHDC efficiencies of OH v -free Pd/Ni(OH) 2 before and after being immersed in the same PO 4 3− solution. Figure 5b shows that the PO 4 3− treatment poses limited effects on the activity of Pd/Ni(OH) 2 .…”

“…It has been well documented that the EHDC reaction is initiated by the reactive atomic hydrogen free radical (H*), which is generated in situ at the cathode surface via H + reduction on a specific catalyst, serving in hydrogenolysis of the C−Cl bond. 4,5 The noble metal palladium (Pd) is the priority catalyst for EHDC due to its relatively low energy barrier in H + /H* conversion, and its appropriate binding strength with H* that enables its evolution to H 2 to be slowed down. 6,7 Current work primarily focuses on strategies to optimize the geometric and electronic states of Pd for intensified H* generation, which is dedicated to boosting the EHDC reaction and raising the atomic utilization efficiency of Pd.…”

“…It has been well documented that the EHDC reaction is initiated by the reactive atomic hydrogen free radical (H*), which is generated in situ at the cathode surface via H + reduction on a specific catalyst, serving in hydrogenolysis of the C–Cl bond. , The noble metal palladium (Pd) is the priority catalyst for EHDC due to its relatively low energy barrier in H + /H* conversion, and its appropriate binding strength with H* that enables its evolution to H 2 to be slowed down. , Current work primarily focuses on strategies to optimize the geometric and electronic states of Pd for intensified H* generation, which is dedicated to boosting the EHDC reaction and raising the atomic utilization efficiency of Pd . Engineering Pd into nanowire/nanosheet structures, , alloying Pd with a promoting metal (Ag, In, and Cu), , constructing Pd-support interfaces (Pd–MnO 2 , Pd–TiO 2 , Pd–C 3 N 4 , Pd–Ni 2 CoO 4 , and Pd–TiN/TiC), decorating Pd with organic ligands, and creating atomically dispersed Pd sites ,− have all suggested to be efficient in affording high EHDC efficiencies.…”