Slow-releasing permanganate ions from permanganate core-manganese oxide shell particles for the oxidative degradation of an algae odorant in water

In this work, potassium permanganate particles (KMnO₄) were modified with a manganese oxide (MnOx) shell comprising passages for the slow release of permanganate ions (MnO₄^-) in aquatic systems. The bare particle (KMnO₄) and KMnO₄ core-MnOx shell particles (CP-60) were characterized by attenuated total reflectance (ATR)-Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The CP-60 were evaluated as a slow source of MnO₄^- for the oxidative treatment of pure and lake water containing dimethyl trisulfide (DMTS), a water odorant produced by cyanobacteria in many eutrophic waters. XPS and ATR-FTIR results confirmed the presence of MnOx surface shell (diameter ∼ 1 μm) on CP-60. SEM images revealed cracks on CP-60, which serve as outlets for MnO₄^-. Approximately 0.76 ± 0.07 g KMnO₄/g of CP-60 was released from the core of CP-60 after 120 min. The CP-60 degraded 88.9 ± 2.5% and 70.8 ± 6.3% of DMTS in pure water and lake water matrix within 120 min, respectively. The degradation was slightly more effective than the degradation using aqueous KMnO₄ (74.2%) reported in literature. The release kinetics of the particles is consistent with a pseudo-first order equation with correlation coefficients of 0.99 and 0.97 in pure water and lake water matrix, respectively. The CP could serve as low cost slow-release particles for the degradation of micropollutants, even in cyanobacteria laden water. Notably, the in situ MnOx formed during the KMnO₄ oxidation reaction can facilitate adsorption of organics and metal ions, improving water quality.