SURFACE MODIFICATION OF PYROPHYLLITE WITH ALUMINIUM FOR THE REMOVAL OF PB(II) FROM AQUEOUS SOLUTIONS

The aim of this study is, at first, to show how the surface property of pyrophyllite can be changed by intercalating aluminium in order to boost the active sites at the surface of pyrophyllite to achieve higher adsorption efficiency for metal cations in aqueous solutions. The treatment of pyrophyllite consists of working on two main factors, namely, the molar ratio OH/Al and the calcination temperature. A series of modified clays were prepared by changing these variables. The samples prepared were characterized by XRD, BET surface area, X-ray fluorescence, TGA and DTG. It has been found that for OH/Al = 2, aluminium exists tetrahedral-coordinated in the solution, in AlO4 located in the centre of spherical polymer (AlO4)Al-12(OH)(24)(H2O)(12)(7+). After calcination at 500 degrees C of the treated pyrophyllite, this polymer is transformed into Al2O3 which is known to have a great capacity in fixing the metal cations in an irreversible way. The second aim is to prove that pyrophyllite can be used for removal of Pb(II) ions from aqueous solutions, and it was examined that aluminium-treated pyrophyllite is much more effective. The results of batch adsorption experiments investigating the effects of contact time, pH, amount of adsorbent and initial solute concentration were discussed. The experiments have shown that the sorption capacities of treated pyrophyllite were considerably enhanced, from 7.05 mg/g for natural pyrophyllite to 18.65 mg/g for treated pyrophyllite.