Removal of Cd(II) and Pb(II) from aqueous solutions by pistachio hull waste

The aim of this study was to use the raw pistachio hull powder for the removal of Cd(II) and Pb(II) from aqueous solutions. The kinetic experiments showed that the bio sorption of Cd(II) and Pb(II) on the adsorbent is rapid, and maximum bio sorption capacities were achieved in 2 h. The time-dependent bio sorption of Cd(II) and Pb(II) onto the adsorbent were well described by both the pseudo-first-order and the pseudo-second-order-models. The experimental adsorption capacity (q_exp) was close to that calculated from these two models. The equilibrium adsorption of Cd(II) and Pb(II) was satisfactorily described by the Sips isotherm. The adsorption isotherms showed that the affinity of Cd(II) and Pb(II) to the adsorbent increased with ph. Based on the estimates obtained by the Visual MINTEQ code, the Pb²⁺ and Cd²⁺ species were the dominant ones in the solutions at ph ≤ 7.0 and ≤ 8.5, respectively. The Fourier transform-infrared results confirmed the interactions between metals and functional groups present on the surface of pistachio hull. These findings show that the raw pistachio hull powder used in this study exhibited a high adsorption capacity for Cd(II) and Pb(II), and thus it may be useful for the immobilization of these metals from polluted sites. (author)