Wastewaters decontamination: Mechanisms of PB(II), ZN(II), and CD(II) competitive adsorption on tunisian smectite in single and multi‐solute systems

Abstract

Polluted water may contain more than one heavy metal species. Consequently, the behavior of a particular metal in a water system may be affected by the presence of the others. In this study, the adsorption of Pb(II), Zn(II), and Cd(II) in single and multi‐element systems onto raw, acid‐activated, and aluminum‐pillared Tunisian smectite (RSM, ASM, and Al‐SM, respectively) was investigated as a function of pH and species concentrations. Physico‐chemical, Textural, XRD, and SEM analyses were investigated onto three different clay materials. The Al‐SM samples, which were calcined at 450°C, presented the best results for the surface areas (267 m2/g) and for the Pb(II) adsorption capacity (75.35 mg/g). For instance, once they contained in a batch system at 25°C, pH 6, they retained more heavy metals due to their textural characteristics. The selected order of adsorption Pb(II) > Zn(II) > Cd(II) showed the importance of the competitive phenomenon onto clay materials' pores adsorption. At a higher pH, the precipitation phenomenon was possible. The two‐site, Langmuir isotherm also yielded the best fit for Pb(II) and Zn(II) adsorption on RSM and Al‐SM in binary and ternary solute‐systems. However, it failed in the case of Pb(II), Zn(II), and Cd(II) on ASM, which had less heterogeneity than other samples. The obtained results can serve as baseline data to design an adsorption process using this local adsorbent for the wastewaters rich in heavy metals. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 229‐238, 2013