Abstract
Competitive adsorption of Pb2+, Cd2+ and Zn2+ ions on sodium dodecyl sulfate (SDS) in binary mixtures were investigated compared with non-competitive adsorption in the unitary metal solution in micellar-enhanced ultrafiltration at a temperature of 25 °C. Mutual interference effects were investigated based on the removal rate, the Langmuir Competitive Model (LCM) and equilibrium adsorption capacity ratios, qe/qm, which indicated the presence of other metal ions. The results indicated that the removal rate and adsorption capacity of Pb2+ were higher than that of the other metal ions in unitary and binary systems. The effects on SDS micelles for Cd-Pb and Zn-Pb combinations were found to be antagonistic. However, it was a favorable effect for the Cd-Zn combination, and the metal ions sorption followed the order: Pb2+ > Cd2+ > Zn2+. The behavior of non-competitive and competitive adsorption for Cd2+ and Zn2+ in a single system and in the presence of Pb2+ were well described by LCM. Moreover, the LCM showed poor fitting to non-competitive and competitive adsorption of Pb2+ in a single solution and in the presence of Cd2+ or Zn2+. In conclusion, the removal of Pb2+ in the presence of Zn2+ or Cd2+ showed greater efficacy than that of Cd2+ or Zn2+ in the presence of Pb2+.
Highlights
Wastewater carrying heavy metals has attracted widespread attention owing to the significant threat it poses to the environment and to human health [1]
Channarong [12] reported the simultaneous removal of nickel and zinc from aqueous solution by Micellar-enhanced ultrafiltration (MEUF), and an activated carbon fiber (MEUF-ACF) hybrid process was performed at a constant permeate flow rate (40 mL/min) and operating retentate pressure (1 bar)
In order to study the effect of feed concentration of metal ions, the sodium dodecyl sulfate (SDS) concentration in feed was fixed at 1.8 g/L and the operating pressure of 0.083 MPa was applied to the micelle adsorption
Summary
Wastewater carrying heavy metals has attracted widespread attention owing to the significant threat it poses to the environment and to human health [1]. Research activities on absorption of heavy metals have focused on absorption efficiency from single component system or multi-component systems onto different adsorbents [6,7] and optimization of reaction conditions onto different adsorbents [8,9] Among these studies, MEUF could remove many metal ions, including Cd2+, Ni2+, Zn2+ [10,11,12], Cr3+, Mn2+, Pb2+, CrO43−, Cu2+, Fe3+ and Fe(CN)63− [13,14,15,16]. It is highly desirable to verify the competitive adsorption in order to provide high metal removal efficiency and reduce the surfactant concentration in permeate for wastewater containing multiple metal ions. The present work studies the sorption dynamics of Pb2+, Cd2+, and Zn2+ during their adsorption by SDS from in unitary and binary component systems
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