Amine modified kaolinite clay from Nigeria: A resource for removing Cd2+ and Pb2+ ions from aqueous solution

Abstract

Kaolinite clay (KC) obtained from redemption camp; Nigeria was modified by surface grafting and investigated for the removal of Pb²⁺ and Cd²⁺ ions from aqueous solution by adsorption. KC and the modified kaolinite clay (MKC) were characterized using X-ray Diffraction analysis (XRD), Scanning Electron Microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area analyzer, Fourier Transform Infrared spectrometer (FTIR), Particle Size Distribution (PSD), zeta potential, elemental analysis (CHNS/O analyzer) and Energy Dispersive Spectroscopy (EDS). Equilibrium, thermodynamics and kinetic studies were conducted by considering the effects of pH, initial metal ion concentration, contact time, adsorbent weight and temperature. Modification of KC increased its equilibrium adsorption capacity from 8.01 mg/g for Cd²⁺ and from 24.75 mg/g to 36.41 mg/g for Pb²⁺ ions. The adsorption process obeys Freundlich and Temkin isotherms. The adsorption was second-order-kinetic and controlled by both intra-particle and liquid film diffusion. Values of ?G^o, ?H^o, and ?S^o, for KC an MKC showed a stable adsorbent-adsorbate configuration.