New insights into single-compound and binary adsorption of copper and lead ions on a treated sea mango shell: experimental and theoretical studies

Abstract

Herein, adsorption isotherms of Pb(II) and Cu(II) ions on treated sea mango fruit in both single-compound and binary systems were experimentally realized at different temperatures in the range of 30-50 1C.Experimental results show that adsorption of Pb(II) was more as compared to that of Cu(II) ions; however, for both ions, a significant reduction in the adsorption capacity was observed in the binary system as compared to that in the single-compound systems. Moreover, under all the investigated conditions, adsorption seems to be promoted by an increase in temperature. To understand and interpret the experimental evidences, the Hill and competitive Hill models developed on the basis of the grand canonical ensemble were applied for the analysis of adsorption equilibrium data. These models contain some physicochemical parameters that allow an exhaustive analysis of the dynamics of single-compound and binary adsorptions. Based on the fitting results, in particular, through the evaluation of the number of ions bonded per site (n and n i ), it was found that lead and copper ions interacted by inclined and horizontal positions on treated sea mango in single-compound and binary systems, respectively. In addition, based on the same parameters, a significant interaction between ions was retrieved. A study focused on the saturation adsorption capacity in single-compound and binary systems affirmed that the adsorbent was more selective for lead than for copper. The reduction of the adsorbed capacity ratio between the binary and single-compound systems (i.e. Q b /Q s ) explained and confirmed that an inhibition effect between copper and lead ions at the same receptor site occurred. Finally, based on the energetic investigations, it was deduced that the adsorption energy represented the dominant factor promoting the greater adsorption of lead than that of copper in both systems.

Equilibrium study of single and binary adsorption of lead and mercury on bentonite-alginate composite: Experiments and application of two theoretical approaches

“…In singlecompound systems, the adsorption capacity of Pb (II) is higher than Hg (II) and for all the investigated temperatures. According to the literature, this difference could be explained by the physicochemical properties of adsorbates and adsorbent [26] and by differences in the interaction energies between the adsorbates and the adsorbent surface [14,15]. Furthermore, the adsorption of Hg (II) was significantly influenced by the presence of Pb (II) in binary systems.…”

“…Analytically, the occupation of BAC receptor site by Pb (II) and Hg (II) heavy metals ions was illustrated by n and n i parameters defined as the number of ions captured by BAC receptor sites in singlecompound and binary system, respectively. However, even if these two parameters are steric, the studies of adsorption phenomena by statistical physics models [14,15] demonstrated that these parameters play an important role in explaining the adsorption mechanism but they are not dominant.…”

“…They are simple and very explicative containing some steric and energetic physicochemical parameters. The mathematical development of these models has been previously detailed [15,27]. The expression of Hill model is given in Eq.…”

“…Hence, the assessment of the adsorption capacity of a compound in the presence of other solutes as well as the definition of appropriate theoretical models is necessary for a proper design of a cost-effective depuration system [11,12]. In the latest years, many efforts have been made by our research group for the individuation of reliable models able to describe, under the same hypothesis, the single-compound and multicomponent adsorption, in order to define their competitive relationships [13,15]. However, one of the main issues dealing with adsorption is that each adsorption system can behave differently and a dedicated study for each of them can be required.…”

“…Far to the classical models and to well quantify the interference of one metal with the adsorption of the other, Hill and competitive Hill models previously published [15,17] were adopted and applied in this paper. The models containing several parameters having the same physicochemical aspect classified in two types (steric and energetic), which can be proficiently adopted to explain the single-compound and simultaneous adsorption mechanism in the same framework.…”