Intercalation of halloysite from Djebel Debagh (Algeria) and adsorption of copper ions

Halloysite available in Djebel Debagh, Guelma (eastern region of Algeria) was characterised by XRF, SEM, XRD, FTIR and by CEC, specific surface area and electrokinetic measurements. The crude halloysite was modified with Mn+(CH3COO)n (M = Na+, NH4+ or Pb2+), and intercalation of NaCH3COO was monitored with time. XRD showed that the intercalation rate exceeded 90% for NaCH3COO at long reaction time. X-ray diffraction also showed an expansion of the interlamellar space of 5.5 and 6.3 Å due to the intercalation of Pb(CH3COO)2 and NH4CH3COO. FTIR proved that Mn+(CH3COO)n reacted with the inner surface hydroxyl groups of halloysite, on the basis of disappearance of the frequence bands at 3676 and 3652 cm− 1 and the appearance of new bands around 3699 and 3457 cm− 1. Intercalation of Pb(CH3COO)2 and NH4CH3COO shifted the band at 1650 towards 1663 and 1671 cm− 1, respectively. The untreated and intercalated halloysite samples were used for removing copper(II) ions from aqueous solutions. The adsorption isotherms were of L-type according to the classification of Giles et al. (Giles, C.H., Mac Ewan, T.H., Makhwa, S.N., Smith, D., 1960. Studies in adsorption. Part XI. A system of classification of solution adsorption isotherms and its use in diagnosis of adsorption mechanisms and in measurement of specific surface areas of solids. J. Colloid Interface Sci. 3, 3973–3993.). The adsorption of copper ions was explained by electrostatic interaction between the copper(II) ions and negatively charged binding sites on halloysite surface and ion-exchange of the cations associated with acetate within the interlayer space.