Separation of methylene blue from aqueous solution by micellar enhanced ultrafiltration

Micellar enhanced ultrafiltration (MEUF) is a separation technique which can be used to remove metals ions or dissolved organics from water. In this study MEUF has been carried out to investigate the retention of metylene blue (MB), a cationic dye, from aqueous stream. Regenerated cellulose membrane of molecular weight cut-off 10 kDa was used in a cross-flow ultrafiltration unit. Sodium dodecylsulfate (SDS), hexadecyltrimethyl ammonium bromide (CTAB) and triton X-100 (TX-100) were used as surfactants and NaCl as an electrolyte. The removal of MB and permeate flux were studied as a function of dye and surfactant concentrations, nature of surfactant, ionic strength and pH. The ultrafiltration experiments showed that anionic surfactant SDS allowed best rejection of methylene blue (R > 97%) for the used range of dye and surfactant concentrations. High retention was also obtained at pH range from 2 to 11. Permeate flux decreases when surfactant or electrolyte concentration increases due mainly to polarisation concentration, osmotic pressure and precipitation. Prior to MEUF experiments the effect of surfactant type and electrolyte concentration on the spectra of methylene blue has been investigated in the submicellar and micellar concentration range.