Wide-pH applicable permanganate activation achieved by MgAl-MnO4-LDH spatial design for enhanced alkaline phenol wastewater treatment

The oxidative efficiency of potassium permanganate (KMnO 4 ) is severely limited under alkaline conditions. To address this limitation, permanganate-intercalated MgAl-layered double hydroxide (MgAl-MnO 4 -LDH) was synthesized via ion exchange. Structural characterization confirmed MnO 4 - intercalation, expanding the interlayer distance to 0.908 nm. The maximum Mn loading (145.52 mg/g) occurred at Mg-Al = 2:1, attributed to enlarged interlayer space. MgAl-MnO 4 -LDH achieved phenol oxidation efficiencies ranging from 15.04% to 70.51% across pH 6.35-12, with the peak oxidation efficiency (70.51%) observed for Mg2Al-MnO 4 -LDH at pH 10 — a 14-fold enhancement over equivalent KMnO 4 . Kinetic and thermodynamic studies revealed a heterogeneous oxidation mechanism: phenol adsorption on LDH surfaces/near-surface followed by oxidation via high-valent manganese confined at laminate edges. It is suggested that the LDH lamellar structure spatially segregates intercalated high-valent manganese from expelled reduction products (Mn 2+ /Mn 3+ /MnO 2 ), maintaining persistent oxidation capacity. The synergistic edge-confined reaction and self-purifying interlayer environment provide a novel strategy for advanced oxidation of alkaline anionic organic wastewater. • Ion exchange synthesis of MgAl-MnO₄-LDH expanded interlayer distance to 0.908 nm. • Peak oxidation efficiency (70.51%) at pH 10, 14-fold higher than equivalent KMnO₄. • Heterogeneous mechanism: Adsorption and edge-confined oxidation by high-valent manganese. • Self-regenerative activity via spatial segregation of Mn species in LDH lamellae.