Hierarchical nano-reactor with core-shell structure for efficient removal of atrazine via heterogeneous catalytic ozonation: Experimental parameters, kinetics and performance analysis

Abstract

The engineering application of the heterogeneous catalytic ozonation process (HCOP) is severely hampered by inefficient heterogeneous catalysts. Herein, a novel hierarchical core-shell MnO2@mSiO2 nano-reactor was prepared using hydrothermal and sol-gel methods. Its catalytic performance was systematically evaluated through the degradation and mineralization of atrazine (ATZ) in HCOP under various reaction parameters. At optimal parameters (O3/7.5 mg/L, ATZ/15 uM, catalyst/30 mg/L, pH = 7), 96.5 % and 36.1 % of ATZ and total organic carbon (TOC) removal efficiencies could be obtained after 30 min, respectively. After five cycles, the ATZ removal efficiency of MnO2@mSiO2 only decreased by approximately 10 %. The synergy effects between the core and mesoporous shell played a vital role in its efficient catalytic activity. The large specific surface area and confined environment favored ozone adsorption, mass transfer and enhanced the enrichment of ATZ, intermediate products, and oxidants. Quenching experiments and the chemical kinetic model indicated that hydroxyl radical (·OH) was the primary oxidant. The Mn3+/ Mn4+ and oxygen vacancies (OVs) acted as active sites to promote ozone decomposition via electron transfer facilitated by the shell. This work provides new advancements for the development of high-efficiency catalysts for the engineering application of HCOP.