Demetallization from crude oil using spherical polyelectrolyte brushes synthesized via emulsifier-free polymerization with the assistance of DFT

The elevated concentrations of metals, such as Fe, Ni, and V, in heavy crude oil pose considerable challenges to refining processes and the quality of the resulting products. Negatively charged spherical polyelectrolyte brushes have demonstrated exceptional efficacy as agents for metal removal. However, the metal removal efficiency of polyelectrolyte brushes is constrained by their particle size. In this study, we synthesized a novel amphiphilic spherical polyelectrolyte brush (PAA@PMMA) characterized by narrow particle size distributions, exceptional dispersion stability, and a high carboxylic acid content through emulsifier-free emulsion polymerization, employing it for the demetallization of crude oil. Utilizing the conductivity titration method, we assessed the carboxylic acid distributions within the spherical polyelectrolyte brush emulsions. The results revealed that the synthesized polyelectrolyte brushes exhibited a smaller particle size (289.7 nm) and a higher grafting rate (28.33 %) compared to traditional polyelectrolyte brushes. Furthermore, we investigated the effects of carboxylic acid distributions on metal removal efficiency. The removal rates increased with the initiator content, ligand dosage, and polymerization temperature, achieving maximum removal rates of 83.5 % for Fe, 50.3 % for Ni, and 80.6 % for V, respectively. Finally, the demetallization mechanism of the novel spherical polyelectrolyte brushes was elucidated with the assistance of density functional theory (DFT) calculations. As the polymer chains approach the core, the Donnan effect of the novel brushes is enhanced, significantly boosting the electrostatic attraction and complexation between ligand molecules and metal ions, thereby resulting in a substantial improvement in metal removal efficiency.