Application of micellar enhanced ultrafiltration (MEUF) process for zinc (II) removal in synthetic wastewater: Kinetics and two-parameter isotherm models

• Beneficial aspect of concentration polarization was figured out in metal removal.
• Zinc(II) adsorption was best described by pseudo-second-order kinetic model.
• Isotherm studies revealed better accountability of Freundlich isotherm.

Micellar enhanced ultrafiltration (MEUF) of zinc(II) from synthetic wastewater using sodium dodecyl sulfate (SDS) at low concentration was carried out in lab scale membrane system. Initial SDS concentration below critical micelle concentration (CMC) showed marginal increment and sharp reduction in zinc(II) removal percentage above CMC. Zinc(II) removal percentage decreased from 84.67 to 82.42% when the initial zinc(II) concentration increases from 0.42 to 2.10 mM at constant SDS concentration. Various performance parameters, i.e., amount of SDS micelles, gross of surfactant, ratio of S′ to M′ (i.e., molar ratio of the SDS micelle to the zinc(II) ions), average concentration factor, volume concentration ratio, and system conversion, as function of initial SDS concentration were investigated. Pseudo-second-order kinetic equation could be used to elucidate kinetics, while Freundlich two-parameter isotherm model was apposite to describe zinc(II) adsorption on SDS micelles. Further, distribution coefficient of zinc(II) ions in micellar and aqueous pseudo-phases, micelle loading, and micelle binding constant were estimated to evaluate MEUF process.