Synthesis, characterization of carbon dots from onion peel and their application as absorbent and anticancer activity

Abstract

Water pollution through dyes has become a challenging issue all around the world. The recognition of the alarming industrial waste discharge and lack of access to fresh water has impressed us to develop a feasible dye adsorbent. In this regard, highly efficient and low-cost CDs were prepared using onion waste with quantum yield 12% as a prospective adsorbent to remove Congo red and Methyl orange. The optical and physicochemical properties of CDs have been characterized using UV, PL, FTIR, SEM, TEM, XRD, XPS and BET analyses. To optimize the maximum adsorption of Congo red and Methyl orange, an efficient and comparative study of the adsorption process was systematically tested using different parameters such as adsorbent dosage, pH, contact time, and initial dye concentration. From the obtained results, the maximum adsorption efficiency reached 91.53% and 91.09% for Congo red and Methyl orange, respectively. In addition, the equilibrium isotherm, kinetic study, and thermodynamics of the adsorption were calculated. According to the experimental equilibrium, the isotherm analysis is well-fitted for the Freundlich model. It is worth noting adsorption kinetics could be fitted with second-order kinetics models (R2 = 1) for CR and (R2 = 0.998) for MO. Finally, the anticancer activity of CDs against MCF-7 breast cancer cells is demonstrated.