Selective separation of copper (II) and cobalt (II) from wastewater by using continuous cross‐flow micellar‐enhanced ultrafiltration and surfactant recovery from metal micellar solutions

Performance of continuous cross‐flow micellar‐enhanced ultrafiltration (MEUF) method was investigated for the selective separation of copper (Cu²⁺) and cobalt (Co²⁺) from the aqueous phase using sodium dodecyl sulfate (SDS) as an anionic surfactant and iminodiacetic acid (IDA) as a chelating agent. Operating parameters such as operating time (10–120 min), cross‐flow rate (100–250 mL/min), pH of the solution (2.8–5.6), molar concentration ratio of the chelating agent to metals (the C/M ratio, 0.5–2.5), molar concentration ratio of the surfactant to metals (the S/M ratio, 5–8) and mode of operation were studied to investigate the effectiveness of the process on selective separation. At optimal parameters, above 90% selective separation (Cu²⁺ in permeate and Co²⁺ in retentate) was achieved. Two methods were studied for the separation of Co²⁺ and SDS from retentate stream; acidification followed by UF and addition of chelating agent followed by UF with surfactant recovery of 75% and 83%, respectively, and Co going into the permeate.