Sustainable Synthesis of Carbon Quantum Dots with Tailored Surface Functional Groups from Pomelo Peel Waste for Inhibiting Scale

Abstract Fruit Shatian pomelo peel is a common solid biological waste. This article reports the environmentally friendly synthesis of carbon quantum dots from Shatian pomelo peel waste by hydrothermal method. The synthesized carbon quantum dots (named PCA‐CQDs) were characterized by transmission electron microscope (TEM), Fourier transform infrared (FT‐IR) spectroscopy, X‐ray photoelectron spectroscopy (XPS), ultraviolet‐visible spectroscopy (UV‐vis) and excitation‐dependent fluorescence emission spectroscopy. The resultant carbon quantum dots were spherical, and the average particle diameter was measured to be 5 nm. The surface of PCA‐CQDs has been successfully modified with functional oxygen‐containing functional groups such as hydroxyl and carboxyl groups. Therefore, PCA‐CQDs exhibit excellent water solubility and calcium ion chelating properties. Most importantly, PCA‐CQDs were used as a new type of green scale inhibitor for inhibiting the CaSO 4 and CaCO 3 scale for the first time, and the scale inhibition efficiency can reach more than 95 %. By observing the changes of the scale crystals in the SEM image, it is speculated that the mechanism of PCA‐CQDs inhibiting calcium scale may include chelation, dispersion and lattice distortion.