Dinamic Laser Speckle applied to the determination of the specific surface area of clays

MOJICA SEPÚLVEDA; MENDOZA-HERRERA; GUILERMO BERTOLINI; C. I. CABELLO; D. B. SORIA; M. TRIVI

OSA Frontiers in Optics, Laser Science APS/DLS

ELSEVIER. OSA - The Optical Society of America

Año: 2019 vol. 4

2162-2701

Dynamic laser speckle (DLS) is proposed as a complementary technique todetermine the specific surface area of natural and chemically modified bentonite. To verifythis approach, we compared DLS technique with the standard physicochemical methods.The determination of the specific surface area of porous materials is an important feature to establish their texturalproperties and their utility as adsorbents for different applications.The most used technique for the determination of the specific surface area of several materials is nitrogen sorption[1]. To model the experimental values obtained by this technique, there are several isothermal equations of whichthe most employed is the BET equation [2] used by the ISO standards. However, the BET model adjusts only theexperimental data for small values of relative pressure. There is not a single function that fits the values obtained forthe entire range of relative pressures used in the sorption experiments for a given surface under study.In this paper, we propose a new approach using dynamic laser speckle (DLS) technique [4?10] to correlate thehydroadsorption capacity of the porous clays with their specific surface rea. We performed DLS measurements fordifferent samples. Then, we use the physicochemical nitrogen sorption standard method to obtain the appropriateisotherm for determine the specific surface area of the materials. Finally, a calibration curve is established between thespecific surface area and the DLS characteristic time τ of the hydroadsorption process.