Adsorption Characteristics of Heavy Metals onto Functionalized Microplastics

High Resolution Image Download MS PowerPoint Slide Microplastics represent a significant environmental threat owing to their persistence and resistance to degradation. Their co-occurrence with heavy metals in aquatic environments exacerbates the risks of complex pollution. While most current research focuses on conventional microplastics such as polyethylene and poly(vinyl chloride), functionalized microplastics, which exhibit richer functional groups and more complex environmental behaviors, remain insufficiently studied. This research examines the adsorption behaviors of cadmium (Cd 2 + ), copper (Cu 2 + ), and lead (Pb 2 + ) onto three types of functionalized microplastics: polyacrylate (PAT), biobased polyurethane (BPU), and petroleum-based polyurethane (PPU). Analyses based on Langmuir and Freundlich isotherm models indicate that microplastics with a particle size of 150 μm exhibit significantly enhanced adsorption capacities for Cd 2 +, Cu 2 +, and Pb 2 +, showing increases of 5–18.62, 12.91–18.04, and 8.7–12.31%, respectively, compared to larger particles (1–2 mm). Among the tested materials, polyacrylate (PAT) exhibited the strongest adsorption affinity, with Langmuir maximum capacities ( q m ) of 34.68, 29.85, and 12.31 mg/g for Pb 2 +, Cu 2 +, and Cd 2 +, respectively, following the order: Pb 2 + > Cu 2 + > Cd 2 + . Furthermore, UV aging increased the adsorption capacity of PAT for Cd 2 + from 7.07 to 11.22 mg/g, as described by the pseudo-second-order model. However, the rate constant ( k 2 ) decreased from 0.027 to 0.006 g/(mg·min), indicating slower adsorption kinetics. These findings provide valuable insight into the interaction mechanisms between microplastics and heavy metals, offering a scientific basis for assessing their copollution behavior and ecological risks.