Comparison of tetracycline adsorption on UV-aged degradable and non-degradable microplastics

The pervasive challenge of plastic waste and its environmental impacts necessitates an understanding of microplastics' roles as vectors for contaminants. This study investigated the adsorption behavior of tetracycline, a widely used antibiotic, on conventional polyvinyl chloride (PVC) and biodegradable polylactic acid (PLA) microplastics, focusing on the effects of UV aging, particle size, and environmental factors such as pH, salinity, and humic acid concentration. Characterization techniques revealed that UV aging significantly altered the surface morphology and increased the adsorption capacity of both microplastic types, with aged PLA exhibiting superior tetracycline adsorption compared to PVC. Kinetic analyses suggested that the adsorption on PVC followed a pseudo-second-order model, while PLA was better represented by a pseudo-first-order model. Freundlich model provides a better fit for the adsorption behavior of tetracycline on both microplastics suggesting the multilayer adsorption mechanism. Acidic and neutral pH conditions enhanced tetracycline adsorption, whereas increased salinity reduced it, underlining the competitive interactions affecting adsorption dynamics. Additionally, low concentrations of humic acid were observed to promote the adsorption of tetracycline onto microplastics. These findings highlight the environmental risks posed by both traditional and biodegradable microplastics, particularly in relation to the transport of harmful contaminants in aquatic ecosystems.