Lignocellulosic Wheat Straw-Derived Ion-Exchange Adsorbent for Heavy Metals Removal

The aim of this work is to develop partially delignified Ca2+-and-Mg2+-ion-exchanged product from lignocellulosic wheat straw for the removal of eight different heavy metals Pb2+, Cd2+, Hg2+, Co2+, Ni2+, Mn2+, Zn2+, and Cu2+ and for detoxification of Cr(VI). Maximum fixation capacity, pH, and initial metal concentration dependence were determined to confirm strong affinity of Pb2+, Cd2+, Cu2+, Zn2+, and Hg2+ ions onto the product, whereas Co2+, Ni2+, and Mn2+ were the least fixed. Morphology of the product characterized by scanning electron microscope showed its physical integrity. Different experimental approaches were applied to determine the role of cations such as Ca2+, Mg2+, and Na+ and several functional groups present in the product in an ion exchange for the fixation of metal ions. Potentiometric titration and Scatchard and Dahlquist interpretation were employed for determination of binding site heterogeneity. Results showed strong and weak binding sites in the product. This product has advantages over other conventional processes by virtue of abundance, easy operational process, and cost reduction in waste disposal of its raw material.