Abstract

In this research work, methylene blue (MB) removal from aqueous solutions was performed by polymer enhanced ultrafiltration (PEUF) with the soluble biopolymer Kappa-Carrageenan (KC). The chemical and molecular structure of KC was verified through the vibrational displacement of specific functional groups in the Fourier transform infrared spectroscopy (FT-IR). The content of 20.7 mmol of sulfate groups per gram of KC and a pKa equal to 2.22 were revealed by acid-base titration. This evidenced the strong acidic character of KC and its ability to attract cationic dyes from aqueous solutions. Almost 100 % of MB was removed from water independent of pH and initial MB concentration. Without the need for pH adjustment (5.10), the washing method allowed 2500 mg L?1 of KC to capture up to 399.67 mg g?1 of MB at a concentration of 500 mg L?1. KC in the PEUF process allowed a high effectiveness and efficiency of MB removal in the presence of interferents and in simulated textile waste (98.4 %). Also, its reuse up to four consecutive cycles. Through the enrichment method, a maximum capture capacity of 39 g g?1 was shown in solutions with an initial concentration of 100 mg L?1 of MB without pH adjustment. © 2025 Elsevier B.V.