X-ray Absorption (XRA): A New Technique for the Characterization of Granular Activated Carbons.

The X-ray absorption (XRA) method using digital image processing techniques is a reliable technique to determine the exhaustion degree of granular activated carbons (GACs). Using an innovative digital image processing technique, the identification of individual adsorbed molecules or ions in a GAC was possible. Adsorption isotherm models (Langmuir and Freundlich) were used to simulate the adsorption equilibrium data of Methylene Blue (MB), nickel, cobalt and iodine. Freundlich equation was found to have the highest value of R2 compared with Langmuir. The identification of distinctive patterns applying XRA for different adsorbed ions and molecules onto GAC was explored. It is demonstrated that unique XRA configurations for each adsorbed ion or molecule are found, as well as a proportional relationship between its incident energy (needed to achieve maximum photon attenuation) and the (effective) atomic number, the adsorbate mass and the molar or atomic mass of adsorbed molecule or ion. XRA method in combination with image histogram modifications was used to obtain a digital signature of adsorbed ions/molecules, giving distinct GSI values for each one in the used energy range. Probabilistic models prove that XRA results are within relationships between effective atomic number and photonic interaction probability, reinforcing the potentialities of XRA for monitoring (multi-)ion and/or molecule combinations on GAC using advanced digital image processing techniques. It was proved that the proposed approach could assess different adsorbed ions/molecules onto GACs in water purification systems.

X-ray absorption as an alternative method to determine the exhausting degree of activated carbon layers in water treatment system for medical services.

Analytical methods based on X-Ray radiation proved to be reliable and sensitive techniques to study activated carbons (ACs). An X-Ray absorption analysis based on digital radiographic images (XRA) is applied for the determination of the exhaustion degree of granular activated carbon (GAC) used in a water purification system for hemodialysis. XRA-method demonstrated the possibility to determine the exhaustion degree at different layers of the GAC filter. The results of the XRA-method were successfully correlated with X-Ray Fluorescence (XRF), TGA, Elemental analysis (EA), SEM, TD-GC/MS, ATR-FTIR, X Ray Diffraction (XRD) and Nuclear Magnetic Resonance relaxometry (NMR) analyses. It was demonstrated that the XRA-method is a fast and reliable analytical tool to give indirect information on the exhaustion degree of GAC at different layers. It is also demonstrated that XRA results can be correlated with the results of the other analytical techniques, rather dealing with the composition and morphology of GAC at different layers.

A novel acoustic approach for the characterization of granular activated carbons used in the rum production.

Acoustic analysis and sound patterns recognition techniques have been widely used in many branches of science, however; almost none focused on the characterization of granular activated carbon. A new methodology has been developed in order to characterize activated carbon based on the dynamic analysis in audible spectra of the sound's relative amplitude power produced by water flooded on granular activated carbon. A home-build recording set-up and management of acoustic measurements have been presented and correlated with the results of porous structure of carbons characterized by N2 adsorption. Five samples of granular activated carbons used in the rum production of different exhausted level have been evaluated by both methods. Parameters as the BET surface area and total pore volume showed a satisfactory correlation with acoustic measurement data when the signal is processed at 1000Hz. Three frequencies components of the produced sound were analyzed and related with the porous characteristics. The found relationship gives the possibility to predict and calculate textural parameters of granular activated carbons applying the acoustic technique. This methodology approach opens possibilities in using acoustic experiments for the characterization of high-porosity materials and to determine their exhausted level.