Simultaneous removal of lead(II), chromium(III), and copper(II) heavy metal ions through an adsorption process using C-phenylcalix4pyrogallolarene material

Heavy metal ion removal remains a serious challenge to the sustainability of our environment. In this work, a simple adsorbent, i.e., C-phenylcalix4pyrogallolarene bearing 12 phenolic functional groups, has been successfully synthesized and evaluated for the simultaneous adsorption of heavy metal ions in acidic media. Results showed that C-phenylcalix4pyrogallolarene exhibited good adsorption percentages for heavy metal ions, i.e., lead(II), chromium(III), copper(II), and nickel(II). Given that the adsorption of all metal ions was driven by the ion exchange mechanism, the adsorption process depends on the pH value of the aqueous phase, yielding the optimum pH values of 5.0, 4.9, 5.2, and 7.9 for lead(II), chromium(III), copper(II), and nickel(II) ions, respectively. The kinetics of heavy metal ion adsorption was governed by the pseudo-second order model, whereas the adsorption isotherm behavior was governed by the Langmuir model. The results also showed that the adsorption capacities for lead(II), chromium(III), copper(II), and nickel(II) were 60.97, 14.31, 8.14, and 16.86 mg g-1, respectively. The interaction between heavy metal ions and C-phenylcalix4pyrogallolarene was also investigated through UV-vis, FTIR, and 1H-nuclear magnetic resonance (NMR) spectroscopic studies. The findings showed that C-phenylcalix4pyrogallolarene is a potential adsorbent material for the simultaneous removal of heavy metal ions.