Microplastics inhibit lead binding to sediment components: Influence of surface functional groups and charge...

Area of Science:

• Environmental Chemistry
• Geochemistry
• Materials Science

Background:

• Heavy metals and microplastics coexisting in sediments pose environmental risks.
• Interactions in ternary sediment-microplastic-heavy metal systems are not fully understood.
• Diverse sequences of coexistence require comprehensive investigation.

Purpose of the Study:

• To systematically investigate interactions among lead (Pb), polystyrene (PS) microplastics, and sediments (goethite and goethite-humic acid) under varying coexistence orders.
• To elucidate the mechanisms behind Pb adsorption inhibition by PS in different sediment matrices.
• To provide a theoretical basis for understanding the environmental fate of microplastics and heavy metals.

Main Methods:

• Systematic investigation of Pb, PS, and sediment interactions under different coexistence orders.
• Analysis of adsorption kinetics and hydrochemical conditions.
• X-ray photoelectron spectroscopy (Pb 4f deconvolution) to determine surface interactions.
• Evaluation of Pb adsorption behavior and Pb-O content changes.

Main Results:

• Polystyrene (PS) significantly inhibited lead (Pb) adsorption onto both goethite (Goe) and goethite-humic acid (GH) composites.
• In the Goe system, PS reduced electrostatic repulsion, increasing Pb mass transfer rate but decreasing adsorption by 7.4% due to competition for hydroxyl groups.
• In the GH system, hydrophobic interactions and complexation between PS and humic acid inhibited Pb adsorption by 28.0% through competition for carboxyl and hydroxyl groups.

Conclusions:

• Polystyrene microplastics exert a significant inhibitory effect on lead adsorption by goethite and goethite-humic acid.
• Understanding these interactions is crucial for predicting the migration and transformation of heavy metals and microplastics in sediments.
• This study provides essential insights into the complex environmental behavior of coexisting pollutants.