RESUMO
Composition of the immobilized layer plays a crucial role in metal adsorption properties of complexing organo-mineral materials. Ignoring the specific features of chemical reactions on solid surface can lead to a significant deterioration in the target properties of the resulted materials. In this research we demonstrated that rationally designed surface-assembling synthesis of organo-silica with covalently immobilized fragments of dipicolinic acid (DPA) resulted in the adsorbent that is capable quantitively recover almost all Rare Earth elements (REEs) from multielement solution with pH > 1.7. In ten consecutive adsorption/desorption cycles no noticeable loss of its efficiency was found, with a mean value of REEs recovery larger than 97%. The adsorbent has been used to recover REEs from model solutions (22 metal ions in 0.5 mol L-1 NaCl) and real leaching solution of waste of fluorescent lamps. It was demonstrated that even 3200-fold excess of Fe and Cu ions only slightly reduces REEs recovery. The adsorbent is capable to recover above 80% of all (except La) REEs from acidic leaching solution from fluorescent lamps with enrichment factors above 600. After adsorption of Eu3+ and Tb3+, the resulting materials exhibited strong red and green luminescence, respectively, indicating chelating mechanism of REEs adsorption on SiO2-DPA.
RESUMO
Feasibility of speckle tracking in optical coherence tomography (OCT) based on digital image correlation (DIC) is discussed in the context of elastography problems. Specifics of applying DIC methods to OCT, compared to processing of photographic images in mechanical engineering applications, are emphasized and main complications are pointed out. Analytical arguments are augmented by accurate numerical simulations of OCT speckle patterns. In contrast to DIC processing for displacement and strain estimation in photographic images, the accuracy of correlational speckle tracking in deformed OCT images is strongly affected by the coherent nature of speckles, for which strain-induced complications of speckle "blinking" and "boiling" are typical. The tracking accuracy is further compromised by the usually more pronounced pixelated structure of OCT scans compared with digital photographic images in classical DIC applications. Processing of complex-valued OCT data (comprising both amplitude and phase) compared to intensity-only scans mitigates these deleterious effects to some degree. Criteria of the attainable speckle tracking accuracy and its dependence on the key OCT system parameters are established.