Sorbent Materials Characterization Based on Mechanical or Thermal Pretreated Montmorillonite Modified by Surfactant Loading for Improved Chromium Retention

MONTES, MARÍA L.; TORRES SÁNCHEZ, ROSA M.; MORANTES, CÉSAR FERNÁNDEZ; MERCADER, ROBERTO C.; YARZA, FLORENCIA; CURUTCHET, GUSTAVO

WATER AIR AND SOIL POLLUTION

SPRINGER

Año: 2020 vol. 231

0049-6979

To improve hexavalent chromium (Cr(VI)) retention of montmorillonite (Mt) at pH 3, Mt samplewas subjected to different treatments: thermal ones at 600 °C or 950 °C, 2 h, or mechanical grinding for 300 s. Then, the obtained products were loaded with different octadecyl trimethyl ammonium loading and 50% and 100% of Mt cation exchange capacity (CEC). The samples were characterized by several techniques at each stage. Differential thermogravimetric analysis (DTGA) performed on the products allowed determining the actual surfactant amount related to the internal or externalsurface by cation exchange and Van der Waals (VdW) mechanisms, respectively, taking into account the CEC of the thermal or mechanical pretreated Mt base sample used. X-ray diffraction (XRD) analysesrevealed that the surfactant loading allowed the reversal of the collapsed interlayer after both treatments. The samples subjected to the thermal treatment at 600 °C and the raw Mt samples exhibit higher positive zeta potential values than the mechanical pretreated Mt oneswith 100% of the CEC surfactant loaded at pH 3. This was directly related to the external surface covered by the surfactant. The agreement between the results of the surfactant coverage on the external surface and Cr(VI) removal at pH 3 indicates that the electrostatic mechanismis the main driving force for the sorption of Cr(VI).These synthesized sorbents achieve similar Cr(VI) retention using less than half the surfactant amount of already published studies.