Adsorption of Fe(III), Co(II) and Ni(II) on ZrO–kaolinite and ZrO–montmorillonite surfaces in aqueous medium

Adsorption of Fe(III), Co(II) and Ni(II) from aqueous solution on kaolinite and montmorillonite, intercalated with zirconium oxychloride (ZrOCl2·8H2O) is investigated in this work. The study is carried out under different environmental conditions obtained by varying pH, concentration of the metal ions, amount of adsorbent, interaction time and temperature. The adsorption is rapid with equilibrium approaching within 300 min for Fe(III), 240 min for Co(II) and 180 min for Ni(II). Second order kinetics gives a better explanation of the rate processes and ZrO–montmorillonite has a larger adsorption capacity than that of ZrO–kaolinite for all the metal ions. The Langmuir monolayer capacity also shows big differences between ZrO–kaolinite and ZrO–montmorillonite, the average values for ZrO–kaolinite and ZrO–montmorillonite being 9.7 and 23.8 mg g−1 with respect to Fe(III), 9.6 and 22.8 mg g−1 for Co(II), and 8.8 and 22.0 mg g−1 for Ni(II), respectively. ZrO–kaolinite interacts endothermically with Co(II) while all the other interactions are exothermic. The results have shown good potentiality for ZrO–clays to be used as adsorbents for Fe(III), Co(II), and Ni(II) ions in aqueous medium.