Ba ²⁺ Removal From Water Using Sulfonated Polymer‐Based Enhanced Ultrafiltration: Insights Into Process Optimization and Mechanism

Polymer‐enhanced ultrafiltration (PEUF) was investigated as an effective, sludge‐free method for removing Ba 2+ ions from aqueous solutions, using poly (sodium p‐styrene sulfonate) as a water‐soluble polymer. The PEUF process involves the interaction of Ba 2+ ions with sulfonate functional groups along the polymer backbone, followed by size‐based separation using an ultrafiltration membrane under nitrogen pressure. The influence of key operational parameters, including monomer‐to‐Ba 2+ molar ratio, contact time, solution pH, and the presence of competing ions, was systematically examined. Increasing the monomer‐to‐Ba 2+ molar ratio enhanced Ba 2+ removal efficiency, reaching 94% at a 5: 1 ratio and approaching a plateau (97%) at higher ratios, indicating effective utilization of sulfonate binding sites. Contact time had a pronounced effect on removal performance, with approximately 96% removal achieved after 45 min. Ba 2+ removal was strongly suppressed at pH 1 but remained high and nearly constant (~97%) over the pH range 3–6. The equilibrium data were best described by the Langmuir isotherm, indicating monolayer binding of Ba 2+ to homogeneous polymer active sites, with a maximum uptake capacity of 268.06 mg/g. Competitive ion experiments showed that monovalent ions (Na + , K + ) caused only minor reductions in removal efficiency, whereas divalent ions (Ca 2+ , Mg 2+ ) significantly decreased Ba 2+ removal due to competitive interactions with the polymer functional groups. These results demonstrate that PEUF using a sulfonated, water‐soluble polymer is a robust and selective approach for Ba 2+ removal from aqueous systems.