Continuous oxidation of organic contaminates in soil by polylactic acid-coated KMnO4

Abstract

Potassium permanganate (KMnO₄), as a versatile and safe solid source of MnO₄^-, received substantial attention from researchers as a potential soil oxidant reagent. In this study, we prepared polylactic acid (PLA)-coated KMnO₄ (KMnO₄@PLA) to control MnO₄^- release. The experimental results indicated that the optimal preparation scheme for KMnO₄@PLA was a particle size of 1–2 mm, a solid-liquid ratio of 1:3, and a core-shell ratio of 1:3. And the release lifetimes of MnO₄^- from KMnO₄@PLA in aqueous and quartz sand media were 200 hours and 310 hours, respectively, which were 2400 and 33 times longer than the release lifetimes of raw KMnO₄. The controlled release of MnO₄^- from KMnO₄@PLA was achieved through the hydrolysis of PLA. And the release process adhered to first-order reaction kinetics and displayed Fickian diffusion characteristics. Moreover, the removal of phenol by KMnO₄@PLA in aqueous, quartz sand, and soil media were investigated through batch and flow column experiments. Compared with the raw KMnO₄, the KMnO₄@PLA exhibited a stronger ability to degrade phenol, due to the mildly acidic nature of the PLA shell. These findings demonstrated that KMnO₄@PLA has significant advantages for the remediation of organically contaminated soils.