Competitive Adsorption of Heavy Metals from Aqueous Solution onto Oxidized Activated Carbon Fiber

In this study, the competitive adsorption of Ni(II)–Pb(II) and Ni(II)–Zn(II) on oxidized activated carbon fiber (ACF-Ox) from aqueous solutions was studied. The experimental competitive adsorption data were interpreted by the following multicomponent adsorption isotherms: non-modified, extended, and modified Langmuir; non-modified and modified Redlich-Peterson; extended Freundlich; and Sheindorf-Rebuhn-Sheintuch. The extended Freundlich multicomponent isotherm best fitted the adsorption data for both systems Ni(II)–Pb(II) and Ni(II)–Zn(II) onto ACF-Ox. The single metal adsorption on ACF-Ox showed that the Ni(II) adsorption capacity was 1.12 times greater than that of Zn(II); however, in the competitive adsorption, the Zn(II) presented an intense antagonism to the adsorption of Ni(II) and Ni(II) to Zn(II) too. The single-adsorption isotherms of Pb(II) and Ni(II) on ACF-Ox revealed that the selectivity of Pb(II) towards ACF-Ox was slightly higher than that of the Ni(II). Nevertheless, in the competitive adsorption, the affinity of Pb(II) towards the ACF-Ox was far greater than that of the Ni(II).