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Adsorption behavior and quantum chemical analysis of surface functionalized polystyrene nano-plastics on gatifloxacin.
Summary
Researchers studied how three types of polystyrene nanoplastics — unmodified, amino-modified, and carboxyl-modified — adsorb the antibiotic gatifloxacin, finding that surface chemistry strongly influences uptake. This matters because nanoplastics that absorb antibiotics could serve as vectors carrying these pharmaceuticals into aquatic ecosystems and the organisms that live there.
In this paper, the adsorption of gatifloxacin (GAT) by three types of polystyrene nano-plastics (PSNPs), including 400 nm polystyrene (PS), amino-modified PS (PS-NH), and carboxyl-modified PS (PS-COOH) was studied and the adsorption mechanism were assessed. Experimental findings revealed that the equilibrium adsorption capacity of PSNPs to GAT followed the order PS-NH > PS-COOH > PS. The adsorption was regulated by both physical and chemical mechanisms, with intra-particle and external diffusion jointly controlling the adsorption rate. The adsorption process was heterogeneous, spontaneous, and entropy-driven. Sodium chloride (NaCl), alginic acid, copper ions (Cu), and zinc ions (Zn) inhibited adsorption, with Cu and Zn having the strongest effect on PS-NH. Theoretical computations indicated that π-π and electrostatic interactions dominated PS adsorption of GAT, while PS-COOH and PS-NH adsorbed GAT through electrostatic interactions, hydrogen bonds, and van der Waals (vdW) forces. The surface electrostatic potential of PS-COOH and PS-NH was considerably higher than that of PS, with the maximum vdW penetration distance of GAT-PS-NH being 1.20 Å. This study's findings provide a theoretical foundation for the migration and synergistic removal of antibiotics, micro-plastics (MPs), and nano-plastics (NPs).