Removal of hazardous dye using a polysulfone-polyaniline composite membrane: A combined experimental and molecular modeling approach

• Composite membranes were developed by incorporating polyaniline (PANi) into polysulfone (PSF). • PANi significantly enhanced the hydrophilicity, porosity, and permeability of PSF membranes. • PSF/PANi membranes showed high removal efficiency for methylene blue and congo red dyes. • GFN2-xTB molecular modeling confirmed improved adsorption energy with PANi addition. • QTAIM analysis revealed strong intermolecular interactions (π–H, π–π stacking, hydrogen bonding) enhancing adsorption. In this study, composite membranes composed of polysulfone and polyaniline (PSF/PANi) were prepared via the phase inversion technique for the efficient removal of hazardous binary dye mixtures methylene blue (MB) and congo red (CR) (MB/CR) from aqueous solutions. The incorporation of PANi significantly enhanced the physicochemical properties of the PSF membranes. Notably, hydropholicity improved, as evidenced by a reduction in contact angle from 85.12° (pristine PSF) to 39.45°, alongside increased porosity and permeability. These enhancements contributed to superior dye separation performance. Moreover, the separation efficiency in the MB/CR binary dyes system was systematically optimized using the Box-Behnken design (BBD) in conjunction with response surface methodology (RSM), enabling the identification of optimal operational parameters for maximum dye rejection. Molecular modeling using the semi-empirical GFN2-xTB method further confirmed the enhanced adsorption performance of PSF membranes upon PANi incorporation. Calculations of frontier molecular orbitals and global reactivity descriptors such as chemical potential, global hardness, and electrophilicity-based charge transfer (ECT) indicated stronger interactions between the composite membrane and dye molecules. Additionally, analysis based on the Quantum Theory of Atoms in Molecules (QTAIM) revealed the presence of significant intermolecular interactions, including π–π stacking and hydrogen bonding. These findings demonstrate that PSF/PANi composite membranes represent a promising, environmentally friendly, and cost-effective solution for the efficient removal of organic pollutants from wastewater.