Removal of Hexavalent Chromium From Aqueous Solutions Using Extruded PLA Films Coated With Polyaniline or Polypyrrole

In this study, the efficiency of novel materials based on extruded Poly(lactic acid)(PLA) films coated with polyaniline (PLA-PANi) and polypyrrole (PLA-PPy) for the removal of Cr(VI) from aqueous solutions was evaluated. The composite films exhibited maximum Cr(VI) removal efficiency at pH 2, reaching 97.39% for PLA-PANi and 92.15% for PLA-PPy. PLA-PPy reached adsorption equilibrium in 10 h, whereas PLA-PANi required 14 h to stabilize, and its behavior was better described by the pseudo-second-order model, indicating a predominant chemisorption mechanism. Moreover, the experimental removal data fit the Langmuir model, suggesting that elimination occurs mainly via monolayer adsorption through ion exchange, as confirmed by x-ray photoelectron spectroscopy (XPS) analysis. Both films showed high selectivity toward Cr(VI), maintaining removal efficiencies above 90% even in the presence of other anions and cations in solution. Additionally, they demonstrated adequate reusability, retaining more than 70% of their removal capacity after three adsorption–desorption cycles. Overall, these results indicate that composite films are efficient adsorbents for Cr(VI) removal from aqueous solutions and represent a promising approach for the treatment of contaminated water.