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 NaP ultra zeolites was surveyed. NaP ultra 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 (SiO 2 )/ n (Al 2 O 3 ) 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-NaP ultra : 92.37% and Cu-NaP ultra : 94.14%) at the n (Fe(NO 3 ) 3 ): n (Al 2 O 3 ) ratio of 1:4 and the n (Cu(NO 3 ) 2 ): n (Al 2 O 3 ) ratio of 1:6. The ultrasonic resulted in the smaller crystal sizes for Fe-NaP ultra (1.90 μm) and Cu-NaP ultra (1.80 μm). Cu-NaP ultra 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-NaP ultra 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.