Acid treatment of south Tunisian palygorskite: Removal of Cd(II) from aqueous and phosphoric acid solutions Original Research Article

The object of this work is to study the modifications of Tunisian palygorskite upon HCl treatment and to investigate the ability of natural and acid treated palygorskite to adsorb heavy metal ions. Chemical analysis, X ray diffraction, infrared spectra, MAS-NMR methods, BET surface and surface charge of HCl treated palygorskite have been reported. It was established that acid leaching at reflux temperature resulted in an increase in the amount of Mg, Fe and Al extracted and in surface area from 59.7 to 437 m2 g− 1 for 2 M HCl samples and from 59.7 to 360 m2 g− 1 for 4 M HCl samples, due to a dissolution of the octahedral sheet and the creation of mesoporosity. 29Si-MAS-NMR studies yield information on changes occurring in the structure of the mineral. During acid treatment the clay structure is progressively transformed into amorphous silica (essentially for samples treated by HCl 4 M for 10 h and HCl 2 M for 35 h).