This study investigated the removal of aqueous hexazinone, a broad-spectrum triazine herbicide, by advanced water treatments, including irradiation with/without hydrogen peroxide (H2O2) and adsorption on coconut shell-based granular activated carbon (CSGAC). A comparison between various irradiation sources (visible, UVA, UVB, and UVC) revealed the highest degradation rate under UVC. The experiments were carried out at 0.5 µM initial concentration of hexazinone. Its removal through photolysis alone (17% with 9 J cm-2 UV fluence) and H2O2 alone (10% with 30 min contact time and 0.5 mM H2O2) were found to be low. However, almost complete degradation of hexazinone (>98%) occurred under 3 J cm-2 UVC fluence in the presence of 0.5 mM H2O2 at pH 7. Further, the degradation rate increased significantly with an increase in the initial dosage of H2O2, UV fluence, and contact time in the UV/H2O2 process. The kinetic studies showed that the degradation followed pseudo-first-order reaction kinetics. In addition, the effect of different scavengers, including methanol, potassium iodide (KI), tert-butyl alcohol (TBA), and potassium dichromate (K2Cr2O7), showed that hydroxyl radicals (•OH) played a dominant role in hexazinone degradation. The rate of degradation was lower (0.003 s-1 µM-1) in secondary effluent, due to the higher abundance of dissolved organics in wastewater, than that in deionized water (0.089 s-1 µM-1). Approximately 90% adsorption of hexazinone was observed with 10 h contact time with CSGAC. Despite being hydrophilic, hexazinone was effectively removed by CSGAC, which may be due to the interaction of CSGAC's surface functional groups with hexazinone's triazine ring through π–π electron donor-acceptor interactions. The adsorption kinetic of hexazinone onto CSGAC fitted the pseudo-second-order model. This study provided mechanistic insights on the removal of hexazinone at the tertiary stage of wastewater treatment.

Removal of aqueous hexazinone using adsorption, photolysis, and UV/H<sub>2</sub>O<sub>2</sub>

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.

Removal of aqueous hexazinone using adsorption, photolysis, and UV/H2O2

Removal of aqueous hexazinone using adsorption, photolysis, and UV/H₂O₂