Abstract
•The Na species amount plays an important role for the formation of Na2Mo4O13/α-MoO3.•The synthesis pH range can be widened from 3 to 6 by adding more Na species.•The catalytic activity of all catalyst for the degradation of dye was investigated.•The mechanism of the promoting effect form Na2Mo4O13 was explored.
The influence of added Na species amount on the formation of Na2Mo4O13/α-MoO3 hybrid catalysts and their catalytic wet air oxidation activity for the degradation of cationic red GTL at ambient conditions were systematically investigated. The structure and morphology of the catalyst precursors and the final Na2Mo4O13/α-MoO3 hybrid catalysts were examined using XRD and SEM analyses, which suggested that the active catalyst Na2Mo4O13/α-MoO3 with nanofiber morphology could be obtained in a much wider pH range by adding more Na species. The influence of some key parameters including reaction time, the volume of dye wastewater, testing temperature, and calcination temperature were evaluated. The mechanism involved was also explored using UV–vis and ESR analyses, which suggested that the benzene ring and azo linkage of dye molecules could be destroyed within 30–45min and the formation of OH radicals is critical for the high activity. By adding more Na species, the removal of both total organic carbon (TOC) and chemical oxygen demand (COD) could also be accelerated. Cycling tests suggested that the catalysts were very robust, and the degradation efficiency was still 99.6–99.9% even after 5 cycles.