The increasing discharge of cobalt-containing effluents from metallurgical, electroplating, and battery-related industries necessitates the development of efficient and stable separation technologies. In this study, a sodium dodecyl sulfate (SDS)-assisted micellar-enhanced ultrafiltration (MEUF) process was systematically evaluated for the removal of Co2+ from aqueous solutions using a flat-sheet polyethersulfone (PES) membrane operated under crossflow conditions. The effects of surfactant concentration, initial solution pH, cobalt concentration, background electrolyte, and extended filtration time were examined to assess process performance and operational stability. Direct ultrafiltration of 50 mg L−1 Co2+ without surfactant resulted in limited rejection (~18%). The introduction of SDS markedly improved removal efficiency, achieving >99% rejection at and above 1 critical micelle concentration (CMC). An SDS dosage of 1 CMC provided an optimal balance between permeate flux (~155 L m−2 h−1) and cobalt removal (>99%). The system maintained high rejection efficiency across a pH range of 3–9, demonstrating robust cobalt–micelle interactions. Increasing the initial cobalt concentration from 10 to 50 mg L−1 caused a moderate decline in flux but did not significantly affect rejection efficiency. In contrast, elevated ionic strength due to NaNO3 addition reduced both flux and cobalt removal, highlighting the influence of competing ions on micelle-mediated separation. Long-term continuous operation for 40 h showed stable permeate flux and sustained cobalt rejection above 99%, indicating minimal fouling. FTIR and SEM–EDS analyses confirmed membrane chemical stability and negligible cobalt deposition. These findings demonstrate that SDS-based MEUF is an effective and operationally stable approach for cobalt removal from contaminated water systems.
Kommalapati et al. (Wed,) studied this question.