Novel functional carbon dot based on Angelica residue and polyethyleneimine: A super-efficient corrosion and scale inhibitor

The stability and high-dose addition of carbon dots in corrosion and scale inhibition are obstacles to their commercial application. Herein, we report a new type of functional CDs (PEI-CD_A) based on Angelica residue and polyethyleneimine (PEI), which can remarkably boost the performance of corrosion and scale inhibition, while expending the application of traditional Chinese medicine waste residue. At 303.15 K, the corrosion inhibition efficiency of PEI-CD_A for carbon steel in 1.0 M HCl medium was tested by weight loss method and electrochemical method and reached over 93 %, which is significantly better than that of CD_A (83 %) under the same conditions. And its corrosion inhibition efficiency can still remain stable after 15 h. The ultra-low dose (5 mg·L^-1) PEI-CD_A has excellent anti-corrosion protection effect on carbon steel due to its ability to form a dense and well-organized adsorption film covering on the carbon steel surface, whose adsorption includes two types of chemical and physical adsorption, and follows the Langmuir adsorption model. Furthermore, static methods display that the CaSO₄ scale inhibition efficiency of PEI-CD_A is up to 100 % when its dosage is 100 mg·L^-1. Analysis of the generated CaSO₄ scale shows that the addition of PEI-CD_A causes lattice distortion, chelation, and dispersion of scale. In addition, the fluorescence spectra imply that PEI-CD_A can be expected to on-line detection of its residual content in the water system. The results demonstrate that PEI-CD_A possesses significant potential in green inhibitors and the comprehensive utilization of waste resources.