Effect of anionic surfactants on the heavy metal ions removal by adsorption onto ion exchangers - batch and column studies

Abstract

Adsorption of heavy metals by various sorbents has been widely studied by many scientists due to the processes of industrialization as well as the great concentration of these toxic and dangerous pollutants in the environment the elimination of which is significant important. The ion exchangers Lewatit MonoPlus SR7, Lewatit MonoPlus TP220, Purolite A830 and Lewatit AF5 were used as adsorbents to remove heavy metal ions (M(II)) such as zinc (Zn(II)), nickel (Ni(II)) and copper (Cu(II)) (especially Cu(II)) in the presence of anionic surfactants to examine the adsorption efficiency in such systems. The main objective of this paper were the kinetic, equilibrium, thermodynamic and column studies in the HCl–M(II)–anionic surfactant (AS) such as SDS (Sodium Dodecyl Sulfate), ABS (Dodecylbenzene Sulfonic Acid) or ABSNa50 (Sodium Dodecylbenzene Sulfonate) systems. The largest adsorption capacities were obtained in the HCl–M(II)–AS systems for Lewatit MonoPlus TP220 (Cu(II): 9.9–10 mg/g; Zn(II): 8.5–8.9 mg/g and Ni(II): 7.3–9.2 mg/g) compared to the other ion exchangers. Therefore, after the first selection, Lewatit MonoPlus TP220 and the systems containing Cu(II) were further examined. The isotherms models were applied in the experimental data analysis and show that the Langmuir (determination coefficient, R2 > 0.993) and Temkin (R2 = 0.948–0.965) isotherm models exhibit the best fitting. The results of the temperature-dependent adsorption of Cu(II) in the presence of SDS on Lewatit MonoPlus TP220 suggested that the adsorption was spontaneous, thermodynamically favourable, and exothermic in nature (the enthalpy, ∆H° = −7.19 kJ/mol (↓CMC) and −7.03 kJ/mol (↑CMC). The largest working ion exchange capacities of the anion exchange resin were obtained for the ABS surfactant (Cw = 30 g/L (↓CMC) and 12 g/L (↑CMC)). As follows from the current investigations Lewatit MonoPlus TP220 has a great potential for the removal of Cu(II) in the presence of ABS and SDS. For comparison, Cu(II) ions removal by the micellar enhanced ultrafiltration process was also presented and exhibits 54–73.88 % Cu(II) removal efficiency in the presence of SDS and ABS.