Effective removal of organic dyes using the ultrasonic-assisted hydrothermal synthesis of NaP zeolite doping Cu or Fe in Fenton-like oxidation systems

NaP zeolite was successfully synthesized via ultrasonic-assisted hydrothermal synthesis. The approaches for Cu or Fe doping were screened. Additionally, the oxidation process of methylene blue (MB) and methyl violet-6B (MV-6B) by the doped NaPultra zeolites was surveyed. NaPultra zeolite exhibited higher crystallinity (94.99%), while the crystallization temperature and duration decreased from 120 °C to 90 °C and from 8 h to 4 h with the n(SiO2)/n(Al2O3) increasing from 2.0 to 4.0, compared to the hydrothermal synthesis. At the ultrasonic power intensity of 30% and the density of 60 mL/W, the conversion rates of Si and Al rosed from 66.46% to 84.68% and from 73.75% to 95.25%, respectively. Comparatively, the complexation approach demonstrated superior findings in the crystallinity (Fe-NaPultra: 92.37% and Cu-NaPultra: 94.14%) at the n(Fe(NO3)3):n(Al2O3) ratio of 1:4 and the n(Cu(NO3)2):n(Al2O3) ratio of 1:6. The ultrasonic resulted in the smaller crystal sizes for Fe-NaPultra (1.90 μm) and Cu-NaPultra (1.80 μm). Cu-NaPultra displayed better oxidation performance in the elimination of MB (93.22%) and MV-6B (98.71%) via the HO at the condition of pH = 5.0, 30 min, 2.5 g/L, 50 mg/L, and 25 °C. Through the combined action of adsorption and Fenton-like oxidation, the rapid enrichment of organic dyes by the zeolite was realized, and the dyes were removed efficiently. Cu-NaPultra was capable of retaining good removal performance throughout four cycles, suggesting that it is a promising catalyst for Fenton-like oxidation reactions and may help to pave the way for the removal of organic dyes.