Removal of cobalt ions from aqueous solution by forward osmosis

The performance of Co(II) removal from aqueous solution by forward osmosis (FO) was investigated. NaCl solutions were used as the draw solutions (DS). The effects of membrane characteristics, feed solutions properties, DS concentration, cross-flow rates on FO performance (water flux, Co(II) flux and retention, and reverse NaCl flux) were determined. The separation mechanisms under the various operational conditions were discussed. Changes of the FO membrane after Co(II) separation were characterized. The results show that CTA-ES featured the highest water fluxes of 15.5 ± 0.5 L m−2 h−1 at AL-FS and 23.4 ± 2.5 L m−2 h−1 at AL-DS among the three membranes. The active layer charge of the FO membrane was a main factor affecting Co(II) retention by FO. The texture of the support layer played a great role in the water permeability and reverse NaCl flux. The optimal operational conditions for Co(II) retention was NaCl concentration of 1.0 M in DS, the cross-flow rates of 11 and 5 cm s−1 at the feed and DS sides respectively. After used, the active layer of the CTA-ES membrane became more rough and hydrophobic. Co might attach to the membrane and became the membrane foulants. FO process could be an alternative technology for radioactive wastewater.