Sorption properties of cadmium on microplastics: The common practice experiment and A two-dimensional correlation spectroscopic study

Microplastics (MPs) that have accumulated in the environment are emerging as contaminating pollutants due to their interactions with metal ions. MPs change the migration and transformation of metal ions in the environment and afterward impact their environmental presence. Therefore, it is necessary to evaluate the interaction characteristics and mechanisms between Cd²⁺and MPs for assessing the ecological impacts of MPs. The traditional sequencing batch equilibrium test demonstrated that the sorption of Cd²⁺ onto MPs was related to the type of MPs present, the pH value of the solution, the ionic strength of the participants and the presence of humic acid. The sorption dynamics and isotherm experiment illustrated that the interactions were controlled by surface sorption and distribution effects. The specific surface area and surface charge were the main factors in managing the sorption process. FTIR spectra and a 2D-COS analysis showed that different functional groups played an important role in the sorption of Cd²⁺onto MPs. The results from this work afford new insights on how MPs may play an important role in the fate and transport of heavy metals and present a new analysis method for evaluating the environmental behavior of MPs and their role in transporting other contaminants.