The removal of zinc from synthetic wastewaters by micellar-enhanced ultrafiltration: statistical design of experiments

The removal of zinc from synthetic wastewater was conducted by micellar-enhanced ultrafiltration (MEUF), using the anionic surfactant sodium dodecyl sulfate (SDS). A two-level full factorial design was used in order to analyze the effect of pressure, membrane nominal molecular weight limit (NMWL), zinc feed concentration, and SDS feed concentration on the rejection coefficient and permeate absolute flux. It was found that NMWL, pressure, and their respective interaction presented the largest influence on the permeate flux, and a negligible effect on the rejection coefficient. Further, zinc and SDS feed concentrations and their interaction had a major influence on the rejection coefficient and negligible effect on the permeate flux. Rejection coefficients up to 99% were achieved when the surfactant to metal molar ratio (S/M) was above 5. Moderate concentration polarization was observed obtaining relative flux of 0.8 when using the smallest pore size membrane.