Sorption, preconcentration and visual assessment of picric acid in water samples using polyelectrolyte membranes

Pollution of water bodies by nitroaromatic compounds, particularly picric acid (PA), represents a significant environmental concern due to its high toxicity, persistence in the environment, and ability to form water-soluble ionized species. In this study, a polyelectrolyte membrane based on a complex of poly(sodium 4-styrenesulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDADMAC) was fabricated using an environmentally friendly aqueous phase separation (APS) method as an extraction matrix for batch-wise adsorptive preconcentration and visual assessment of PA. Membrane morphology and surface properties were characterized by SEM and AFM, and pH-dependent water uptake was evaluated. The results demonstrate that the fabricated polyelectrolyte membrane effectively captures PA from aqueous solutions via π–π stacking and electrostatic interactions, achieving >90% removal efficiency. Furthermore, the color change of the membrane during PA sorption enabled the development of a portable calibration palette for its rapid on-site visual assessment, with an established visual limit of detection of 1·10 -5 M. Overall, these findings provide new insights into the interaction mechanisms between nitroaromatic compounds and polyelectrolyte matrices and highlight the potential of PSS–PDADMAC membranes as a sustainable platform for express analytical preconcentration and semi-quantitative monitoring of PA.