Action of Low-Density Polyethylene Microspheres in the Transport of Metformin Hydrochloride in Aqueous Medium Through Adsorption and Desorption

The present study addresses the issue of transporting pharmaceuticals via microplastics in aquatic environments. For this purpose, the adsorption and desorption of metformin hydrochloride (MET), a hydrophilic compound, on polyethylene microspheres (PMEs) were studied via batch adsorption and desorption capacity and kinetics tests. The adsorption test results indicated minimal influence of pH values above 5, alongside a decrease in adsorption capacity with an increasing mass of PMEs. The Freundlich model best represented the adsorption capacity data; however, values of n < 1 (0.6) and low K suggest a decrease in the sorption affinity of MET with increasing initial MET concentration and a low affinity of MET for PM beads. The rate and equilibrium of adsorption were fast, and the results adequately fit the pseudo-first- and pseudo-second-order models, suggesting that physical and chemical mechanisms contributed to the adsorption of MET onto the PEMs under the conditions of this study. The desorption equilibrium result was 1.3 mg g−1 ± 0.04 mg g−1, without significant change, regardless of the initial amount of adsorbed MET. However, the desorption percentage varied between 26.14% and 7.01% as a function of the amount. of MET adsorbed onto the PMEs. These results suggest that PMEs could be potential vectors of MET transport in aquatic environments.