Chemometrics approach for adsorption multi-response optimization of Cu(II), Zn(II), and Cd(II) ions from phosphoric acid solution using natural clay

This study describes the elimination percentage optimization of Cu(II), Zn(II), and Cd(II) heavy metal ions from a phosphoric acid solution (three-metal ions system) using a natural clay (NC). The response surface methodology (RSM) based on the central composite design (CCD) was used to maximize the elimination percentages of these heavy metals. The natural clay was characterized by FTIR, XRD, TGA-DTG, SEM, and EDX techniques. Several important parameters influencing the adsorption process of these ions in the multi-metallic mixture such as contact time (X₁), temperature (X₂), and mass of NC (X₃) were investigated systematically by batch experiments. The fitted model indicated that the optimal conditions to simultaneously maximize the elimination percentage of these ions were 26.82 min, 16.26 °C, and 3.56 g of NC mass. Under these conditions, the numerical estimation of the elimination percentages was 71.10, 69.06, and 67.83% for Cu(II), Zn(II), and Cd(II), respectively. Freundlich and Langmuir’s models were fitted to evaluate the equilibrium data of the heavy metal adsorption process by natural clay. According to the obtained results, it appeared that Freundlich isotherm gives a good representation of the adsorption phenomenon of Cu(II) ions, and for the adsorption of Cd(II) and Zn(II) on NC, the data shows fit both Freundlich and Langmuir isotherm model.