Adsorption mechanism of persistent organic pollutants using carbon quantum dots in wastewater based on molecular simulations and experiments

초록

Emerging concerns have arisen regarding the presence of 14 typical persistent organic pollutants (POPs) in wastewater due to their toxicity and environmental persistence. Adsorption technology has emerged as a promising approach for their removal. In this study, four novel carbon quantum dots (CQDs) with chemical formulas perylenetetracarboxylic dianhydride (C34H14O2), beta-Carotene oxide (C52H72O14), phthalocyanine (C39H30N6O10), and Tetrakis(alkylthio) Porphyrin (C52H72O10S4) were investigated using first-principles calculations to evaluate their adsorption capabilities toward these contaminants. Complementary molecular simulations were also performed to construct adsorption models for the 14 POPs. The surface adsorption properties of the CQDs were found to be strongly influenced by their elemental composition. Specifically, C34H14O2, C52H72O14, C39H30N6O10, and C52H72O10S4 exhibited superior adsorption performance toward decabromodiphenyl ether (C12Br10O), nonylphenol (C15H24O), antibiotic (C25H37NO4), and chlorinated paraffins (C12H19Cl7), respectively. Moreover, the adsorption of POPs onto CQDs significantly altered the band structure, density of states, and electron localization function of the CQDs. The optimal configuration revealed that POPs-3 adsorbs parallel to CQDs-13. Notably, the CQDs-4-POPs-3 complex exhibited the smallest free volume fraction, indicating the strongest adsorption interaction between them. Importantly, non-targeted adsorption was observed between CQDs and POPs, where both adsorption strength and binding mode are intricately dependent on the molecular structure of the individual POPs. This work provides valuable insights for the rational design of CQDs-based adsorbents to remove emerging pollutants from wastewater and mitigate associated ecological and human health risks.

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