Recoverable vegetable wastes for the degradation of dyes from wastewater

Food waste is a significant problem globally, with considerable economic and social impact, with estimates suggesting that approximately one-third of products are wasted annually along the supply chain. This waste not only takes up large spaces in landfills, but also contributes to the greenhouse effect by emitting gases with high global warming potential, such as methane and carbon dioxide. A promising method of valorizing food waste consists in converting it into carbon dots, which have various applications due to their extremely low toxicity and minimal impact on the environment. In this work, the transformation of Momordica charantia residues into carbon dots and their use in the purification process of waste water contaminated with textile dyes was pursued. Two dyes were investigated - one anionic (Amaranth) and one cationic (Methylene Blue) - which were treated with carbon dots. The degradation of the dyes was carried out in a basic environment and under the action of type A ultraviolet radiation. Four systems were designed ( Exp 1 ÷ 4) for the degradation of Methylene Blue and Amaranth dyes. The experiments performed suggest that the Exp 2 and Exp 3 (using K 2 CO 3 and H 2 O 2 ) systems are adequate for the degradation of Methylene Blue with k constants of 5.34 × 10 –2 and 8.15 × 10 –2 with t ½ of 12.9 min and 8.5 min. For Amaranth dye, an interaction between CDs and the dye was observed leading to an increase in absorbance intensity, recommending the use of CDs as identification agents.