<p>The objective of this study is to develop and evaluate innovative ultrafiltration (UF) composite membranes for water treatment applications, with a particular focus on decolorization. These composite membranes were created by physically combining polylactic acid (PLA) and polyetherimide (PEI) polymers in varying proportions. The resulting collodion was then affixed to a polyamide substrate, thereby endowing the membrane with mechanical strength. During the course of this study, three PEI concentrations were taken into consideration: 20%, 25%, and 30% by weight, corresponding to the membranes M20, M25, and M30, respectively. A series of hydrodynamic tests were conducted on the synthetic membranes, encompassing permeability and selectivity assessments. In addition to these hydrodynamic tests, a range of spectroscopic tests were performed, employing a variety of methodologies. These methodologies included Fourier Transform Infrared (FT-IR) spectroscopy, Nuclear Magnetic Resonance (NMR) spectroscopy, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) spectroscopy, and mechanical resistance testing. A series of ultrafiltration tests were conducted to assess the retention capabilities of the modified membranes. These tests utilized model textile effluents containing dyes such as methyl red (MR) and benzathren green (BG), with a transmembrane pressure of approximately 4 bar. Permeability studies revealed that the enhanced M20 membrane exhibited remarkable water permeability of over 340 L.m⁻².bar⁻¹, along with maximum dye rejection rates of 53.95% and 62.88% for MR and BG, respectively. The enhanced UF composite membrane's superior performance renders it a promising candidate for wastewater treatment and decolorization. The findings of this study demonstrate that the integration of polyamide support with PLA-PEI resulted in the development of an ultrafiltration membrane with exceptional performance.</p> Graphical Abstract <p></p>