Comparative Study between Acoustic Emission Analysis and Immersion Bubble-Metric Technique, TGA and TD-GC/MS in View of the Characterization of Granular Activated Carbons Used in Rum Production

Microscopic and acoustic emission analysis and sound patterns recognition techniques were applied for the characterization of granular activated carbon (GAC). A new and improved methodology has been developed to characterize the exhaustion degree of GAC used in rum production: (1) based on the acoustic emission analysis of the sound produced by water flooded on GAC; and (2) based on the microscopic analysis of bubbles formed by immersion into glycerol. Acoustic measurements are made in a specific set-up, bubble detection and analysis is performed using dedicated software developed in MATLAB® for circular shape pattern detection based on the Hough transform. Both have been correlated with data of GAC characteristics based on thermogravimetric analysis (TGA) and Thermal Desorption-Gas Chromatography Mass Spectrometry (TD-GC/MS). Eight samples of GAC used in the rum production, obtained at different depths within the fixed-bed filter, have been evaluated. Good correlations are found between the immersion “bubble-metric” technique and the acoustic measurement data from the original signal processed by Band-Pass (BP) filtering at 1.3 kHz and weight loss amounts of adsorbed compounds on the GAC. The found relationship gives the possibility to determine the exhaustion degree of GAC applying these methods and to evaluate high-porosity materials.