Acid activation of a palygorskite with HCl: Development of physico-chemical, textural and surface properties

A palygorskite from Bercimuel (Segovia, Spain) was treated with 1.0, 3.0, 5.0 and 7.0 N solutions of HCI for 1 hour under reflux. The solids obtained were characterized by XRD, FT-IR spectroscopy, thermal analyses, TEM and nitrogen adsorption-desorption isotherms at 77 K. The acid treatment runs with the removal of the octahedral cations—Mg(II), Al(III) —and the formation of amorphous silica from the tetrahedral sheet. An important increase in the specific surface area was observed during treatment, reaching a maximum of 286 m2/g in the sample treated with 5.0 N HCI. The silica obtained after the treatments maintains the fibrous morphology of natural palygorskite. No creation of microporosity is observed during the treatment.