In situ generation of H₂O₂ using MWCNT-Al/O₂ system and possible application for glyphosate degradation

Hydrogen peroxide (H₂O₂), as a green oxidant, has been widely applied into advanced oxidation processes (AOPs) for the degradation of toxic organic pollutants. The in situ generation of H₂O₂ can not only improve the storage and transportation safety of H₂O₂ but also reduce the capital and operation costs. In the present work, a novel system, i.e., multi-walled carbon nanotube‑aluminum (MWCNT-Al) composite was used to in situ generate H₂O₂ through micro-electrolysis. The MWCNT-Al composite was characterized and optimized. The accumulation concentration of H₂O₂ reached 947 mg/L at the initial pH of 9.0, the MWCNT-Al composite dosage of 8 g/L and oxygen gas flow rate of 400 mL/min after 60 min. The in situ generation of H₂O₂ was achieved by MWCNT-Al/O₂ system, mainly owing to the direct contact between Al⁰ and MWCNT in MWCNT-Al composite, which accelerated the transfer of electrons from Al⁰ to O₂, as well as the excellent electrocatalytic activity of MWCNT toward the two-electron reduction of oxygen. When H₂O₂ in situ generation technology was used in peroxone process (O₃/H₂O₂ process) to degrade glyphosate in aqueous solution, the removal efficiency of TOC and total phosphorus was 68.35% and 73.27%, respectively. Finally, the possible mechanism of in situ generation of H₂O₂ in MWCNT-Al/O₂ system was temporarily proposed.