Influence of acid activation on adsorption of Ni(II) and Cu(II) on kaolinite and montmorillonite: Kinetic and thermodynamic study

The removal of Ni(II) and Cu(II) with clays (kaolinite, montmorillonite and their acid-activated forms) in aqueous medium have been studied. Batch adsorption experiments were carried out by considering various solution pH, interaction time, and temperature. The adsorption was strongly dependent on pH of the medium. The uptake was very fast initially and maximum adsorption was observed within 180 and 360 min of agitation for Ni(II) and Cu(II), respectively. The kinetics of the interactions was best described by second order mechanism. The adsorption data yielded Langmuir monolayer capacity as 4.3–28.0 and 7.1–21.3 mg g−1 for clay-Cu(II) and clay-Ni(II) interaction, respectively. Adsorption of Ni(II) and Cu(II) followed exothermic and endothermic paths, respectively. The results showed that kaolinite and montmorillonite and their acid-activated forms are good adsorbents for Ni(II) and Cu(II) in aqueous medium.