Efficient removal of aromatic pollutants via catalytic wet peroxide oxidation over synthetic anisotropic ilmenite/carbon nanocomposites

Abstract

As one of the most common ferrous (Fe2+)-containing oxide minerals in the Earth’s crust, ilmenite (FeTiO3) is a potential low-cost heterogeneous Fenton-like catalyst for organic wastewater treatment via catalytic wet peroxide oxidation (CWPO). However, it suffers from low activity and long induction time. Herein anisotropic FeTiO3/C nanocomposite with rich Fe2+ ions on large surface area of 159.0 m2 g−1 (surface Fe/Ti and Fe2+/Fe3+ ratios were respectively 2.1 and 2.0) was prepared via cetyltrimethylammonium (CTA+)-assisted sol-gel synthesis. CTA+ modulated the growth of FeTiO3 nanoparticles with more exposed metallic sites by preferential adsorption on its (104) plane via electrostatic attraction, provided the carbon source and facilitated the generation of more Fe2+ ions at the interface of FeTiO3/C via carbothermal reduction of FeTiO3. FeTiO3/C efficiently catalyzed CWPO removal of six aromatic pollutants with different charges (25 mg L−1 each) at 25 oC and pH 3.0 without an induction period owing to rich Fe2+ content on neutral surface (pHpzc ~3.3)—three dye solutions completely decolorized in 1 h and three antibiotics degraded by >90% in 3 h. Reusability of FeTiO3/C was demonstrated with cationic rhodamine B and anionic orange G dyes in five consecutive runs. Scavenging tests and spin-trapping EPR spectra confirmed the generation of dominant ·OH and minor O2•− species for organic degradation via catalytic decomposition of H2O2 on FeTiO3/C as a heterogeneous Fenton-like catalyst.