Efficient eradication of antibiotic and dye by C-dots@zeolite nanocomposites: Performance evaluation, and degraded products analysis

Metronidazole (MET), a recalcitrant antibiotic from the nitro-imidazole family and commercially used Rhodamine B (RhB) dye, contributes a huge to water pollution, which needs to eliminate, preferably by photocatalytic degradation technique. The Cdots@zeolite (CDZ) nanocomposites with different weight ratios (1:1, 1:3, 1:5, 5:1, 1:7) were synthesized hydrothermally to degrade MET and RhB molecules. The CDZ composites were characterized by XRD, BET, EDS, and XPS technique which verifies the crystalline nature, incorporation of C-dots into zeolite frameworks with high surface area (similar to 187 m(2)/g). The morphology, d-spacing and lattice planes were analyzed by SEM images, HR-TEM and SAED analysis. The maximum degradation (similar to 79%) was achieved at an optimum catalyst dose of 0.2 g/L and pH 4 for MET and that of RhB was similar to 90% at a catalyst dose of 0.4 g/L. The PZC (point of zero charge) value for CDZ composite was about pH 3.4, which justifies the maximum removal of MET at pH 4. The obtained rate constants 'k' were found to be 0.0081, 0.0041, and 0.0101 min(-1) in sun, UV, and visible light sources, respectively. The real industrial wastewater sample has been treated to give similar to 68% of COD and similar to 62% TOC removal. Moreover, the intermediates of plausible degradation pathways were identified by the m/z values obtained from GC-MS analysis.

Automated summary

This study synthesized Cdots@zeolite (CDZ) nanocomposites for the photocatalytic degradation of Metronidazole (MET) and Rhodamine B (RhB). The CDZ composites exhibited high catalytic activity under different light sources, achieving maximum degradation efficiencies of 79% for MET and 90% for RhB. The CDZ composites also demonstrated effective removal of COD and TOC in real industrial wastewater samples. GC-MS analysis further identified the intermediates of plausible degradation pathways.