Removal of Cd(II) by MEUF-FF with anionic-nonionic mixture at low concentration

Micellar-enhanced ultrafiltration (MEUF) is an effective method to remove cadmium ions (Cd(II)) with sodium dodecyl sulfate (SDS). The dosages of SDS in previous studies were often quite large. This paper investigated the synergism of anionic-nonionic surfactants and combined process of MEUF and foam fractionation (MEUF-FF), especially the influence of the mole ratio of Triton X-100 (TX-100) to SDS on the rejection factor of Cd(II). At the same time, the separation characteristics including residual ratio of SDS, TX-100 and total surfactants were also studied. Moreover, the performances of MEUF-FF in SDS/TX-100 mixed system were compared with those in SDS-only system. The results of MEUF-FF with SDS/TX-100 mixture showed that the rejection factor of Cd(II) reached the highest value (98.4%) when the dosage of SDS was 337.4 mg/L (0.15 CMC) and the molar ratio of Triton X-100 to SDS was about 0.5. Compared to the results in the SDS-only system, the mixed system saved the dosage of SDS more than 50% and reduced the residual ratio of SDS about 25% at the same Cd(II) rejection factor. This paper provides a promising method using SDS/TX-100 mixture in the MEUF-FF process to efficiently reduce the dosage and residual ratio of anionic surfactant.