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Enhanced copper adsorption by polyamide and polylactic acid microplastics: The role of biofilm development and chemical aging
Summary
Researchers studied how chemical aging and biofilm growth on polyamide and polylactic acid microplastics changed their ability to absorb copper from water. Both processes significantly increased the surface area and chemical reactivity of the plastics, making them absorb substantially more copper than fresh microplastics. The study suggests that as microplastics age and develop biofilms in natural waterways, they become increasingly effective at concentrating heavy metals, potentially altering how these contaminants move through aquatic environments.
Plastics undergo a range of physical, chemical, and biological changes in natural aquatic environments, which profoundly affect their environmental fate and bioavailability. This study investigates the effects of potassium persulfate (KSO) oxidation and biofilm attachment on the surface p'roperties and Cu(II) adsorption behavior of polyamide (PA) and polylactic acid (PLA) microplastics. Both chemical aging and biofilm formation significantly increase the specific surface area, crystallinity, and oxygen-containing functional groups of these microplastics. Specifically, the specific surface area of KSO-aged PA and PLA microplastics increased to 3.546 m g and 2.930 m g, respectively. 16S rDNA analysis revealed distinct bacterial communities on PA and PLA-MPs, reflecting different microbial attachment due to polymer types. Compared to pristine microplastics, KSO-aged PA and biofilm-covered PA had Cu(II) adsorption capacities of 1.536 mg g and 0.946 mg g, respectively, while KSO-aged PLA and biofilm-covered PLA capacities increased to 1.163 mg g and 0.812 mg g. Cu(II) adsorption onto aged microplastics followed the Freundlich model, indicating a multilayer adsorption mechanism. The pH significantly impacted Cu(II) adsorption efficiency, with the best performance observed under near-neutral conditions. Fulvic acid inhibited Cu(II) adsorption by competing for adsorption sites and forming complexes with Cu(II). These findings highlight the transformation mechanisms of microplastics within natural settings and their potential as heavy metal carriers, providing vital insights for assessing the environmental impact of microplastic pollution.
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