Saffron derived carbon quantum dot/N-doped ZnO/fulvic acid nanocomposite for sonocatalytic degradation of methylene blue

In the present study, N-doped ZnO/fulvic acid (FA)/carbon quantum dot (CQD) nanocomposite was prepared through hydrothermal method for catalytic degradation of methylene blue (MB). The CQD nanoparticles were synthesized from dried stigma of saffron. FT-IR, XRD, TGA, BET, FESEM-EDS, and TEM were conducted to characterize the prepared nanocomposite. A sonocatalytic approach using probe-type ultrasonic irradiation (20 kHz, 100 W) was applied to treat polluted water with MB. The synergetic capability of ultrasonic irradiation and catalytic activity of N-ZnO/FA/CQD nanocomposite produce reactive species for better degradation of MB in aqueous environments. Based on the results, the optimized values for main parameters in pH of 8 were determined as N-ZnO/FA/CQD dosage of 1.5 g/L, MB primary concentration of 20 mg/L, time = 50 min, and [H2O2] = 5 mM. The adsorption behavior of MB onto N-ZnO/FA/CQD was demonstrated through the pseudo second-order kinetic model and can be fitted with Langmuir isotherm model. The N-ZnO/FA/CQD nano composite showed the enhanced sonocatalytic activity with degradation efficiency of 94% for MB dye. The N-ZnO/FA/CQD nanocomposite might be regarded as an efficient catalyst for degredation of organic dyes in wastewater.