Chemically Activated Natural Clay as Effective Scavenger for Cd(II) and Co(II): Isotherms, Kinetics and Thermodynamic Evaluations

Abstract

Abstract The investigation of the impact of sulphuric acid activation on natural clay in Cd(II) and Co(II) ions scavenger from aqueous medium under various experimental factors was carried out. The clay samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray Fluorescent (XRF), X-ray diffraction (XRD). The FT-IR results revealed the presence of prominent absorption bands of kaolinite at 3695.63, 3627.52, 1113.54, 918.50, 790.40, 537.93, and 446.95 cm-1. The adsorption process of Co(II) demonstrated good correlation with pseudo-second-order kinetic for both adsorbents, while that of Cd(II) depicted better conformity with pseudo-first-order kinetic model indicating physical adsorption mechanism. The maximum adsorption capacities predicted by Langmuir isotherm for natural clay (NC) and chemically modified natural clay (CMNC) are 86.341 and 158.760 mg/g for Co2+, 78.221 and 136.671 mg/g for Cd2+ respectively with the activated clay showing better adsorption capacity. Values of thermodynamic parameter of ΔH° for NC and CMNC was estimated and found to be 2.534 x 106 and 2.309 x 106 kJ mol−1 for Co2+ and 1.020 x 106 kJ mol−1 and 1.591 x 106 kJ mol−1 for Cd2+ thus indicating endothermic process. The results derived from this present study revealed that the chemically modified natural clay is better adsorbent for the scavenger of Co(II) and Cd(II) ions in contaminated water over natural clay.