Effect of various types of anions and anionic surfactants on the performance of micellar-enhanced ultrafiltration process in the removal of Pb(II) ions: An optimization with the response surface methodology

Abstract

In the present study, the micellar-enhanced ultrafiltration (MEUF) process was employed for the removal of Pb2+ ions from aqueous solutions using sodium dodecyl sulfate (SDS) and sodium lauroyl sarcosinate (Sarkosyl) as the anionic surfactants. The performance of Sarkosyl was compared to SDS, a frequently used surfactant in the MEUF processes, to evaluate their efficiency in the removal of lead ions. Sodium chloride (NaCl) was used as the electrolyte and the role of lead salt anions, lead nitrate (Pb(NO3)2) and lead chloride (PbCl2), was also investigated for the first time in the MEUF process. The MEUF process was modeled using response surface methodology (RSM), and experiments were designed and carried out based on the central composite design (CCD). Two categorical variables of anionic surfactants and lead salts, and two numerical variables of Pb2+ and electrolyte concentrations were considered as the studied factors in this design. The process was assessed in terms of its ability to simultaneously maximize Pb2+ rejection and permeate flux. The results showed that increasing the concentration of NaCl significantly reduces the permeate flux, while lead ions concentration has a negligible impact on the permeate flux. The response surface plots also indicated that the effect of the anionic surfactant type on the permeate flux is insignificant. In the studied range of lead concentrations, the highest removals of Pb2+ ions were observed at the concentration of 21 mg/L of Pb(NO3)2 and 0.05 M of NaCl, equal to 79.27% and 94.74% for Sarkosyl and SDS anionic surfactants, respectively.