Cd(II) adsorption from aqueous solution by raw and modified kaolinite

This study aimed to investigate the adsorption and desorption potential of raw kaolinite (Kaol) and manganese oxide (MnO₂)-modified kaolinite (MnO-Kaol) for the removal of cadmium (Cd(II)) ions from aqueous solution and waste water. The chemical and morphological characterizations of kaol and MnO-Kaol were carried out by using Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FT-IR) analysis methods. The BET surface analysis results showed that the specific surface area of kaol increased by about 68% after MnO₂ modification. The cadmium adsorption feasibility of MnO-Kaol was examined systemically by evaluating the effects of initial pH of solution, contact time, adsorbent concentration, and temperature of solution on the adsorption efficiency. From the Langmuir model, the adsorption capacities of kaol and MnO-Kaol were found to be 14.11 and 36.47mgg^-1. The Dubinin-Radushkevich (D-R) model showed that the Cd(II) adsorption onto MnO-Kaol was progressed essentially by chemical ion-exchange. The recovery test demonstrated that the MnO-Kaol has good reusability performance after repeated ten times adsorption-desorption cycles. The thermodynamic studies revealed that the adsorption process of Cd(II) onto MnO-Kaol has exothermic nature and more feasible with increasing temperature of solution. The kinetic investigations also denoted that the adsorption process better fits the pseudo-second-order kinetic model.