AND logic gate supported novel speckled phosphorus-doped carbon dots decorated ZrO2/CaO/MgO sonocatalysts for efficient MB dye decolorization

Textile dyes are significant contributors to aquatic pollution in developing nations, and also the current pace of human-caused contamination of worldwide freshwater bodies is frightening. Herein, we report the sonocatalytic decolorization of the methylene blue (MB) dye using a novel synthesis of composite materials of zirconium oxide (ZrO2), calcium oxide (CaO), and magnesium oxide (MgO) nanoparticles (NPs) decorated by phosphorus-doped carbon dots (PCDs). The monoclinic phase of ZrO2 has shown the highest catalytic activity, thus imparting greater decolorization efficiency (DE) in the synthesized metal oxide nanoparticles (MONPs) decorated with PCDs (MONPs@PCDs). The sonocatalytic efficiency of MONPs@PCDs was evaluated using MB as the analyte molecule. We report DE of up to 99.54% via speckled PCDs decoration and synergistic effect in a short time of 30 min at just 20 kHz frequency. The sonocatalytic activity of MONPs@PCDs is AND logic gate supported and was found as ZCMO@PCDs (99.54%) > ZMO@PCDs (96.47%) > ZO@PCDs (94.68%) > ZCO@PCDs (93.40%). However, the sonocatalytic activity of MONPs was only ZCMO (11.21%) > ZMO (9.26%) > ZO (3.79%) > ZCO (2.92%), under identical experimental conditions. The synergistic effect in polymetallic systems opens new pathways to be explored in sonocatalysis. We confirmed the synthesis of PCDs and their speckled decoration on the surface of MONPs using scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The speckled nanocomposites, i.e., MONPs@PCDs, showed an enhanced and faster decolorization efficiency than the bare MONPs, as demonstrated by the kinetics studies as 101 fold increase in k values and 101 fold decrease in t(1/2) values.Novelty statement: Novel nanocomposites have been developed for MB dye decolorization using a low frequency of just 20 kHz and possessing 99.54-93.40% DE in only 30 min, thus may aid in industrial dye decolorization and the reuse of wastewater for environmental sustainability.

Automated summary

This study reports a novel nanocomposite material for decolorization of dyes. The material shows high efficiency in short time and can achieve synergistic effect at low frequency. It is of great significance for industrial dye decolorization and wastewater reuse.