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 CaSO4 and CaCO3 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.

Carboxyl-Engineered Silicon Quantum Dots (CSiQDs) as an Efficient Scale Inhibitor: Formulation Inhibition Mechanism

“…The observed high efficiency at low concentrations makes CSiQDs superior to the other materials reported in the literature since those materials require higher dosages to reach maximum efficiency. For example, the gypsum static bottle inhibition test reveals an efficiency of 100% only after a 200 ppm dosage of carboxyl carbon quantum dots (CCQDs) at 70 °C and only after a 55 ppm dosage of carbon quantum dots (PCA-CQDs). ,, Compared to these related studies, CSiQDs reach the maximum efficiency (100%) at a lower dosage of 20 ppm. The high inhibition efficiency attained at lower concentrations is attributed to the highly dense carboxyl functionalization facilitated by the abundant amine groups on the synthesized SiQDs.…”

“…The product was tested against calcium sulfate scale giving a good inhibition efficiency through chelation, dispersion, and lattice distortion. 25 Li et al synthesized sulfur quantum dots using carboxymethylcellulose (CMC-SQDs) as a passivator, which gave a very good scale inhibition efficiency at low dosages. The authors speculated that the negatively charged carboxyl anions chelate with the Ca 2+ hampering the normal crystal growth and further that the CMC-SQDs work as a dispersant and a crystal modifier.…”

“…Zhao et al synthesized carbon quantum dots from pomelo peel waste via a hydrothermal method. The product was tested against calcium sulfate scale giving a good inhibition efficiency through chelation, dispersion, and lattice distortion . Li et al synthesized sulfur quantum dots using carboxymethylcellulose (CMC-SQDs) as a passivator, which gave a very good scale inhibition efficiency at low dosages.…”

Green synthesis of fluorescent carbon quantum dots from bagasse: inhibition of calcium sulphate scales

“…Zhao et al used carbon quantum dots (PCA-CQDs) extracted from grapefruit peels using the hydrothermal method for CaSO 4 and CaCO 3 scale inhibition, which yielded scale inhibition efficiencies of >95%. 14 Long et al synthesised CQDs from lychee leaves via the green hydrothermal treatment; these CQDs exhibited a high corrosion inhibition efficiency of 98.06% for Q235 carbon steel in a hydrochloric acid solution. 15 Xu et al synthesised biomass CQDs from mangoes using the hydrothermal method, which was then used as an effective corrosion inhibitor for metallic copper in a sulphuric acid solution.…”