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The solubilization of methylene blue (MB) in sodium dodecyl sulfate (SDS) using hollow fiber membrane was studied. In MEUF, the effects of important factors (MB and SDS concentrations, temperature and electrolyte concentration) on the permeate and retentate concentrations of MB and SDS, equilibrium distribution constant (Kd) and micelle loading (Lm) were investigated. It was found that MB molecules could be solubilized fully within micelles of SDS. The increase of feed SDS concentration promoted retentate MB concentration. Temperature could change the SDS micellization effect. The addition of NaCl could improve the retentate MB and SDS concentrations and reduce significantly the permeate SDS concentration.

article i nfo Article history: In this study, micellar-enhanced ultrafiltration (MEUF) was used to remove Cd 2+ from synthetic wastewater using a polysulfone spiral wound ultrafiltration membrane and sodium dodecyl sulfate (SDS) as a surfactant. The effects of two important parameters related to membrane fouling in MEUF were investigated: transmem- brane pressure (TMP) and feed concentration. The recycling of retentate to the feed tank, which led to con- tinuous growth of SDS concentration, is investigated. The permeate flux and fouling resistance around the critical micelle concentration (CMC) showed that higher SDS concentrations did not always lead to more se- rious fouling, but fouling became more serious after the SDS concentration reached five times the CMC. With increasing TMP, the flux declined drastically as a result of particle aggregation and gel layer formation. How- ever, the TMP was not always a good criterion of membrane fouling: in different phases, high TMP and low TMP values affected membrane fouling differently; a high TMP such as 0.25 MPa resulted in low membrane fouling at the beginning of the MEUF because of the higher driving power; and a low TMP such as 0.05 MPa caused more serious membrane fouling after stopping because of pore blocking.

Micellar-enhanced ultrafiltration (MEUF) is a promising technology to remove metal ions and organic contaminants simultaneously from wastewater. A laboratory experiment was conducted to evaluate the efficiency of a MEUF operation for the removal of Cd2+ and phenol using pure SDS and mixed surfactants (Triton X-100/SDS). In pure SDS system, with the increase of the feed SDS concentration, a significant rise in Cd2+ rejection was obtained, which peaked at 97.0% with initial SDS concentration being 8.0 mM. Nevertheless, the phenol rejections only kept moderately increasing from 14.5% to 40.0%. In mixed Triton X-100/SDS system, the rejections of Cd2+ and phenol were both enhanced by the moderate addition of nonionic surfactant for the same total feed surfactant concentration as the pure SDS system. With the increase of the molar ratios of Triton X-100 to SDS (α), Cd2+ rejection increased slightly with α ranging from 0 to 0.8, and peaked at 91.3%. And the phenol rejection kept increasing from 27.7% to 42.4% when α was less than 1.0 followed by slight decrease to 40.2% at α = 1.5. Moreover, the SDS dosage and the surfactant(s) concentration in permeate were reduced efficiently. The permeate flux of MEUF with mixed surfactants was lower than that with pure SDS.

Single and simultaneous removal of Cd(2+) and methylene blue (MB) with sodium dodecyl sulfate (SDS) by micellar-enhanced ultrafiltration under different experimental conditions was investigated. In single removal process, with initial SDS concentration increasing, the removal efficiency of Cd(2+) and MB kept increasing and then decreased. When the initial concentrations of SDS and Cd(2+) were 1.0 cmc and 50 mg L(-1), respectively, the maximum removal efficiency of Cd(2+) was obtained as 99.2%. Removal efficiency of MB could achieve more than 99.9% with initial SDS concentration below 2.0 cmc. As compared with single Cd(2+) removal, the removal efficiency of Cd(2+) in the presence of MB was slightly higher with initial SDS concentration below 1.0 cmc, while decreased with the SDS concentration above 1.0 cmc. The maximum removal efficiency of Cd(2+) was 98.8% when initial concentrations of SDS and MB were 1.0 cmc and 4 mg L(-1), respectively. The removal efficiency of MB in the presence of Cd(2+) could achieve higher than 96.5%, which was only 3.4% less than the optimum result of the single removal. Meanwhile, effect of pH on removal efficiency of Cd(2+) was more significant than that of MB.

Micellar-enhanced ultrafiltration (MEUF) of methylene blue (MB) from dye wastewater was explored for obtaining colorless water, using a 10-kDa molecular weight cut-off (MWCO) polysulfone hollow fiber membrane and sodium dodecylsulfate (SDS) as an anionic surfactant. The effects of factors, such as operating pressure, feed SDS, MB and sodium chloride (NaCl) concentrations, on the permeate flux (J) and additional resistance (Rf) as well as the observed MB and SDS rejection were investigated. Moreover, the zeta potential of SDS micelle with feed SDS, MB and NaCl concentrations in the solution was also quantified. The rejection of MB and SDS decreased slightly with operating pressure increasing. It was observed that the permeate flux decreased while the additional resistance increased with increased SDS and MB concentrations in the feed. The addition of NaCl significantly increased surfactant retention and reduced the back contamination. The rejection of MB and SDS were 99.3 and 96.0%, respectively, with MB (6 mg/L), SDS (8 mM) and NaCl (200 or 300 mM) in the solution.

Micellar-enhanced ultrafiltration (MEUF) is a powerful treatment developed to remove heavy metals from wastewater. Efficient removal of Cd(2+)/Zn(2+) from wastewater was performed by MEUF using a polysulfone hollow ultrafiltration membrane, with sodium dodecyl sulfate (SDS) as the surfactant. The adsorption of surfactant micelles and Cd(2+)/Zn(2+) in MEUF was studied by changing the surfactant dosage and the Cd(2+)/Zn(2+) concentration in the feed. In addition, kinetics, adsorption isotherms, and thermodynamic rules were analyzed, and X-ray photoelectron spectroscopy (XPS) was conducted. It was found that when the Cd(2+)/Zn(2+) feed concentration was 50 mg/L, and the SDS dosage reached 2.15 g/L, the concentration of heavy metal ions in the permeate stabilized at around 1-4 mg/L, and the adsorption of Cd(2+)/Zn(2+) on SDS micelles followed second-order kinetics and the Langmuir isotherm laws. Adsorption is a spontaneous endothermic process in which the adsorption force is principally the attraction of opposite electrical charges.