Application of carbon dots as efficient catalyst for the green oxidation of phenol: Kinetic study of the degradation and optimization using response surface methodology

Abstract

The reactivity of bio-polymer based nano carbon dots (NCDs) was studied for catalyzing the decomposition of H₂O₂ to generate free hydroxyl radicals and consequently its applicability in the removal of phenol. To the best of our knowledge, for the first time, this work reports that bio-polymer based NCDs could activate H₂O₂ and yielding more than 99% phenol degradation within 20 min in the presence of 12 mmol H₂O₂. Herein, a simple hydrothermal carbonization route was employed for the synthesis of NCDs. The surface morphology, functional groups and crystallinity of the NCDs are studied. SEM images show the NCDs with spherical shape. The graphitic nature of the NCDs was evident from the XRD pattern. The presence of many surface functional groups is confirmed by FT-IR spectra. The influences of three independent operating parameters involving hydrogen peroxide concentration (4-12 mmol), reaction time (10-20 min) and catalyst amount (50-1000 ppm) on the phenol oxidation rate by two NCDs were examined using response surface methodology (RSM). Terephthalic acid (TA) dosimetry demonstrates that the as-prepared NCDs can produce hydroxyl radicals from H₂O₂, and hence catalyze the oxidation of phenol. Finally, the reusability of the NCDs catalysts was examined and the produced catalysts exhibit good recyclability.

Keywords: Carbon dots catalysts; Degradation efficiency; H(2)O(2); Phenol; Response surface methodology.