Equilibrium and Kinetic Studies on Removal of Cd2+ Ion in Aqueous Solution by the Multiple Modified Diatomite

The problem of metal pollution was regarded by many researchers for a long time. The wastewater containing metal ions must be treated. A composite modification technology of acid activating, sodium hydroxide and baking was applied to improve the diatomite adsorption ability, and a modified diatomite was prepared. The adsorption experiment of the metal wastewater by the modified diatomite was carried out in detail. The modified diatomite owned the high adsorption capacity of the Cd²⁺ ion. The operating parameters, such as contact time, concentration of Cd²⁺ ion and reaction temperature, had an important effect on the removal of the Cd²⁺ ion in aqueous solution. The adsorption of Cd²⁺ ions onto the modified diatomite was 9.65 mg/g. The adsorption process fits well with the Langmuir isotherm model and the pseudo-second-order kinetics model and it implied that the adsorption was mainly a physical process. The adsorption process is chemisorption, which involves a sharing of electrons between the adsorbate and the surface of the adsorbent.